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1. md renes OMNE e e F WR Believe me water activity the future for quality and food shelf life uan BH food sample AquaLab gunking S ia ES the sensor chamber Wh d ha iUm nomm m n a a al a ee LLL a a a e anl a RES Don t move the unit without removing the 24 sample Close the 54 drawer gently EAE 45 1 when it is holding 21 aliquid sample Wipe the sample dish rim with your d finger every time you introduce new sample into _ the chamber This duum keeps the bottom CUNG pom of the chamber 1 mie ur iud M Par 1 2 2 ae ae alita va or natem E nn Golly gee whiz 1 I ve always dreamed of owning a gizmo this lt 4 a 7 gut Ta ala caca a Did yo id you read sane the only fill 182. 1 1 4 LI tb 1 4 LI 1 r I 1 1 1 1 I 1 1 I 4 ex a Li 9 E e e e c AMANO O ea ee u a oQ AquaLab Operators Manual Water activity Measurement 59 Baird Parker and B Freame Combined effect of water activity pH and temperture the growth of Clostridium botulirlum from spore and vegetative cell inocula Journal of App 30 3 420 429 Beuchat Larry Ph D Microbial Stability as Affected by Water Activity Cereal Foods World July 1981 Vol 26 No 7 PAGE 345 349 Bousquet Hicard M G Quayle T Pham and J C Cheftel Comparative study of three methods of determining water activity in intermediate moisture foods Lebensmittel Wissenschaft und Technologie 13 169 173 1980 Campbell G S Ph D Effect of Ethanol on Water Activity Measurements using the 17 Unpublished Chirife J G Favetto C Ferro Fontan and S Resnik The water activity of standard saturated solutions in the range of intermediate moisture foods Lebensmittel Wissenschaft und Technologie 16 36 38 1983 Dole M and L Faller Water sorption by synthetic high polymers Journal of the American Chemical Society 12 414 419 1950 60 AquaLab Operators Manual Water activity Measurement Favetto G S Resnik J Chirife and C Ferro Fontan Statistical evalu
3. You re right 554 Let me eene unplug the p fan assembly kJ and set it to the side for If you break a blade off the tiny internal fan located inside the sensor block your instrument cannot peach equilibrium and mustbefactory repaired Just use 4 little when handling the fan assembly Lay fanto one side Thanks Betty knew you d see my logic Next we clean the sensor mirror Swab it with gentle strokes It says do not use a Q tip during cleaning Glue residues holding the Q tip together can get on the mirrored surface What s a tip d dirty mirror is the main cause of bad water activity readings The contamination is sometimes invisible to the naked eye film dust oil and even a fingerprint can throw things off Clean ail surfaces of the block It is critical for and non H20 soluble substances to be removed without scratching or etching Start with distilled water and a KIM wipe Don t use foam Q tip They have a glue in them which leaves atough residue Paper towel leaves tint and sizing material residue Lint free KIM wipes critical for successful mirror cleaning Cleaning the mirror a a a boh After the mirror is clean we clean the temperature sensor on the lower block Close up of uunderside of block
4. F F E E E E E E a F E NM E E E k E E PNHIFENIESM MEME E E E b E Z MEL m future mH H E Q3 EN wmm uu mmm 3 n m mm m m mmu NH od A bhu a NNNM MM we have brighte FE NE NE NM Thanks to AquaLab water activity meter t gt F 4 It was the black amp white post war atomic age Panoramic movies television and stereo sound were infant ideas yet unleashed on an unsuspecting world In new food labs a growing concern for food safety quality and nutrition fueled a need Welcome to Acme Foods part of new breed of black amp white food processors soon to be producing modern Technicolor foods Dr Betty Smith young amp O something quality control expert works at one of America s finest food processors Acme Foods Hi ag TR ae ensem men 12 saw the dangerous moments when safe food hung in t
5. If the sensor is quite sticky it is usually necessary to clean the bottom of the sample temperature sensor with alcohol car pulls into the parking lot of Acme Foods Always clean the mirror thermopile and the optical sensor After you finish cleaning them to your satisfaction clean them one more time If water doesn t work use 99 isopropyl alcohol E 7 Pa s P a P a A EE KR E the 42 i im a trenc coats and om 1 pork pie hats 7 on no Tt mysterious inspeotors in arriving from the mysterious government regulatory agency suits with Ifyouown several CX 2 sandthey _ produce different water activity readings 0 003 then they all need to be cleaned Don t try to make them match without cleaning it s a waste of J walk fromthe parking 009 x 7 B measures T H Water f activity Inless r Fp E KO 4d od ok 4 E od T b hk oC d d wow ef
6. reete nna 46 12 Troubleshooting Appendix Temperature Control 91 5 re qM 65 AquaLab Operator s Manual Water activity Measurement 5 water activity a It will enable you to quickly and reliably measure the a of your products AquaLab is simple to use and will give accurate results when properly maintained About This Guide included in this reference guide are instructions for setting up AquaLab verifying the calibration of the instrument sample preparation instructions and guidelines to help you maintain and care for your instrument Please read all of these instructions before operating AquaLab to ensure that the instrument performs to its full potential Operator s Manual Water activity Measurement Customer Service Information If you ever have questions about AquaLab or need assistance regarding your instrument there are several ways that you can contact us Our toll free customer service number is available you to call Monday through Friday between 8 a m and 5 p m Pacific Time 1 800 755 2751 Fax us Send us the description of your problem question or application us how we can help you Please include the serial number of your AquaLab and its model number Also include your name phone and fax numbers so that we can ge
7. J OD 268830 ee 4 eo 8 E 8555285 x m m 5 Si WP DIG 2 14 T H A aW 2 Ween Ln 330 114 1 e PLA BM ru utt DOO E m ed 821 Bee Puta ta A n a T ne p 5 0943 920 oe 5 EEEE TE a a n a n d m aa n oa a a oa a d 59 E mm mmm arate ee E EE a a a ala unu LR UR LRL OC 3 Marana ar a arata a a pare e nO 0 F E F F HP H E ER m k A A w wu m EH NH BE BOR 4 I kE kE Fb tT bua m ww mo m 9 NH DL b EH ER H EH EH EH NH HN BEBE WR BOB OB E HH NN LE m m a B B HR m 5m FPP ee et ee r P H MH H8 H U EH PN r EE uu NN E EE ur M
8. Remove the tab by inserting a small screwdriver or awt into the hole at the center bottom of the power module chamber Slide the tool under the tab and hook it into the hole in the center front of the tab You may need to hold the fuse puil lever as you slide the tab gently out The tab allows you to select between four voltage settings 100 120 220 and 240 If your power source does not exactiy match one of these settings choose the closest setting Align the tab by rotating it until the number corresponding to the voltage you want is right side up and facing you Slide the tab back into position The correct voltage should now be displayed in the back left hand corner Carefully replace the fuse and slide the plastic cover over the fuse chamber Preparing AquaLab for Operation After finding a good location and checking the voltage connect the power cord to the back of the unit Before plugging in or turning on AquaLab turn the sample drawer knob to the Open Load position and slide it out empty disposable sample cup is usually placed upside down in the drawer to prevent damage during shipment Remove this cup close the drawer plug in the instrument and turn it on The power switch is located in the lower left of AquaLab s front panel When AquaLab is turned on garbage will appear the display Within 30 seconds the display should show 16 AquaLab Operator s Manuai Water activity Measuremen
9. time will print out Sending Data to a Computer AquaLab can send data to any computer with a serial AquaLink software provided with the RS 232 cable will display collected data on the screen and allow you to save it as a quote and comma delimited ASCII file Most spreadsheets can import these files for further data analysis Check your spreadsheet user s manual for more information Backing Up and Running AquaLink from Floppy Disk Before using the AquaLink program from a floppy disk make a backup copy Insert a blank formatted diskette into drive A Place the AquaLink diskette in drive B Type COPY B AQUALINK EXE Running AquaLink from a floppy disk Place the floppy disk in drive Type A AQUALINK Installing AquaLink to the Hard Drive Place the AquaLink diskette in drive 36 AquaLab Operator s Manual Water activity Measurement Move to your hard drive directory and make AquaLink directory by typing MD AQUALINK Move to the AquaLink directory CD AquaLink and type COPY A AQUALINK EXE Put the original AquaLink diskette in a safe place To run the AquaLink program type C AQUALINK Connecting the RS 232 Cable Connect AquaLab to your computer using the 5 232 interface cable The cable plugs into the serial port on your computer Note if you are not sure which port is COM see your computer manual Collecting Data Running AquaLink To begin
10. activity Measurement important Hints Concerning the CX 2T The 2 should be hooked up to a running water bath for at least one half hour before the unit is turned on This allows the water bath to reach a desired and accurate temperature When using your CX 2T it is important that the temperature of the drawer and the temperature of the sample are the same The sample to be measured should sit in the temperature tray for at least 3 minutes before any measurements are taken When running the CX 2T with a water bath the instrument s case fan must always be turned off When the water bath is not employed the fan must remain on The switch controlling the case fan Is located on the instrument s back panel above the fan fliter The case fan keeps the block temperature constant when the water bath is not in use This helps to ensure accurate readings When a water bath is employed the water maintains the block temperature If the case fan is on at this time it will cool the block to a tamperature lower than the sample causing condensation within the block and faulty readings As temperature of the CX 2T increases water activity readings will decrease It is necessary to adjust for an offset when the instrument is run at different temperatures Instructions for this process are located in chapter five of this manual Note Do not try to chill the CX 2T using a water bath Dew will form throughout the sample ch
11. alf way Sins RU m Wu REI 4 rr 1 7 42 2 i er a we Da vs ru NE 7 ar E 1 t En J A 5 j q a eta tas 7 LJ Fa E Pg E t eu iet ets s Fats ur y Pd _ e ans Pa gt 5 RS E rats n EODD a T Pur M oS u vate gt havet o send i it away 1 can clean it rselves No big gt ig dea It only 15 mines ii WARNING It says in the manual to check the filter in back first Gently release plastic grill Remove foam filter and wash it with soapy water It looks Okay Let s go to the next step Clean the filter on the back regularly Don t let it plug up A plugged filter causes temperature errors Unlike machines
12. clean chamber and the fan filter should be routinely checked and cleared of all contamination The user may observe the sample temperature rise faster than usual as the fan filter becomes AquaLab Operator s Manual Water activity Measurement 43 contaminated A plugged filter will reduce airflow which is necessary for cooling the block to maintain the correct temperature balance between the block and the sample Unplug AquaLab Locate the fan filter at the back of AquaLab s case Location of AquaLab s Fan Filter Carefully separate the two parts of the plastic fan guard by inserting a small screwdriver in between the bars and gently pulling forward Note The user should not need to remove the screws that secure the fan filter If you encounter problems while trying to remove the fan guard contact Decagon Remove the spongy filter and rinse it under running water with the dusty side down Pat the filter gently between two paper towels to eliminate any excess water Replace the filter and the fan guard Checking the Calibration It is necessary to recheck the calibration of AquaLab to correct any linear offset that may have occurred during cleaning 44 AquaLab Operator s Manual Water activity Measurement Check the response of AquaLab by measuring the water activity of a saturated salt and distilled water See chapter five for preparation instructions If a linear offset has occurred refer to chapter
13. collecting data type AQUALINK at the DOS prompt The AquaLink start up screen will appear Press return and begin taking readings with AquaLab The readings will be displayed on screen under three headings time and temperature The time readings are real clock time according to your computer If your computer s clock is set to the correct time the time readings will be accurate Save listed readings to disk at any time by pressing the F1 key When you select F1 the program will prompt you to enter a file name If you wish to save data to a different drive or directory than the one where AquaLink is stored specify that drive and directory with the file name data will be saved to this file AquaLab Operator s Manual Water activity Measurement 37 If you wish to use a spreadsheet to analyze your data you may want to use a particular extension For example comma delimited files must have the extension prn to be read by some versions of Lotus Check your spreadsheet users manual for more information AquaLink can display up to 2000 readings before saving However we recommend saving more frequently to guard against data loss if you enter the same file name at the file name prompt AquaLink will append data to the existing file No data will be lost To exit the program press F2 If some of the data has not been saved AquaLink will prompt Data not saved you sure you want to quit Ma
14. few limitations One of these includes the measurement of propylene glycol which condenses on the surface of the chilled mirror and prevents accurate readings Not volatiles react this way glycerol has posed no problems and most other alcohols used to flavor foods are also measurable AquaLab may also have trouble measuring extremely dry substances with an of less than 0 03 Some very dry or dehydrated foods absorb or desorb moisture in such a way that their readings may take longer than five minutes Black pepper for example causes faulty readings at first but after the initial gas has dissipated the product can be read accurately Operator s Manual Water activity Measurement 13 Before setting up AquaLab check to make sure you have received 4 AquaLab main unit Power cord 100 disposable sample cups Operators Manual Choosing a Location To ensure that AquaLab operates correctly and consistently place it on a level surface This reduces the chance that sample material will spill and contaminate the inside of the instrument To protect the internal electrical components and avoid inaccurate readings place AquaLab in a location where the temperature remains fairly stable This location should be well away from air conditioners heaters refrigerator exhausts or other devices which cause rapid temperature fluctuation Checking and Changing Voltage Settings Users in the United States and C
15. it will be possible to get rel able readings Clean all surfaces of the block with the damp lint free tissue including the port holes on top Lift up the sensor block and gently clean the thermopile it looks like an eye located on the bottom of the block AquaLab Operator s Manual Water activity Measurement 41 Location of AquaLab s Thermopile Clean the lid of the chamber especially the small optical sensor found near the fan Clean the sample drawer and its base any debris from the inside of AquaLab Note When replacing the sample drawer be sure it is fit correctly into the base so that it will engage the switch on the bottom of the drawer Caution if the switch lever on the drawer gets behind the switch lever on the base it will break off the lever causing numerous problems Recheck for debris including fuzz from the tissue Carefully insert the fan assembly into the block Align it so that the four screw holes match When replacing the sensor block make sure that the two alignment pins located on the lower section of the block are lined up with the holes on the drawer base You may have to gently force the pins into the holes in the base Insert the four screws with the metal washers and O rings into the holes Turn them counter clockwise until a slight drop in the screw height is felt or seen Turn the 42 AquaLab Operator s Manual Water activity Measurement sc
16. mirror Location of AquaLab s Sensor Mirror Note If the mirror will not come clean using distilled water a small amount of 9995 isopropyl or ethyl alcohol be used followed by distilled water rinses careful if the cloth too wet with alcohol the seal 40 Operator s Manual Water activity Measurement around the mirror will broken and require repair at Decagon Getting the mirror clean could be likened to getting laboratory glassware clean First use the necessary cleaners and then follow with several rinses After a thorough cleaning it is possible to check the effectiveness of the cleaning by running the instrument with the top off It is important when you do this that you unplug the fan motor Follow the wire from the motor on top of the block lid to the small circuit board Disconnect this plug Turn the knob to read After about one minute the mirror will begin to fog Even fog formation over the entire mirror is an indication of a good cleaning Further cleaning of the mirror surface can be achieved by wiping the fog from the mirror as it forms with tissue as previously described Fogging will continue until the display reads LO or the knob is turned to open This procedure can be repeated as often as desired Taking care not to damage the fan blade by dropping it or running the fan while it is out of the block is of utmost importance Any broken fan blade must be replaced before
17. of water activity answers this question Water activity is an energy measurement which defines the amount of unbound water in a product Because microorganisms require water for survival too much iree water a product can serve as a medium for microbial reproduction travel and contamination But if water 9 10 Operator s Manual Water activity Measurement within a product is held with enough force microorganisms will not be able to exert the energy required to obtain water necessary for their subsistence In this way is commonly used in the evaluation of food quality and safety Energy measurements are influenced by potentials that affect the binding of water These include matric potentials chemical bonding energies osmotic potentials gravitational potentials and pressure potentials Matric chemical bonding and osmotic potentials are very important in their relation to water activity in foods By altering any of these potentials the a of a product may also be altered Matric potential in a food product refers to the product s structure and its ability to hold water within that structure through capillary and surface tensions Chemical bonding energy refers to the energy of chemical water bonds within a product Osmotic potential refers to not only the potential energies exerted on water across semi permeable membranes but also to the energy a microorganism might exert on a product in order
18. on water sorption Lebensmittel Missenschaft und 62 AquaLab Operator s Manual Water activity Measurement Technologie 20 237 240 1987 The water sorption of chitin isolated from the Northern Milk Cap mushroom Lactarius trivialis Lebensmittel Wissenschaft und Technologie 20 259 262 1987 Paakkonen and Kurkela Temperature effect on the water sorption of Northern Milk Cap mushrooms Lactarius trivialis in processing and storage Lebensmitiel Wissenschaft und Technologie 19 215 217 1986 and Kurkela Effect on drying method on the water sorption of blanched Northern Milk Cap mushrooms Lactarius trivialis at different temperatures Lebensmittel Wissenschaft und Technologie 20 158 161 1957 Papendick I and S Campbell Theory and Measurement of Water Potential Water Potentia Relations Soil Microbiology Soil Science Society of America 1980 Pollio M L D Kitic G Favetto and J Chirife Effectiveness of available filters for an electric hygrometer for measurement of water activity in the food industry Journal of Food Science 51 1358 1359 1986 Resnik and J Chirife Proposed theoretical water activity values at various temperatures for selected solutions to be used as references sources in the range of microhial growth Journal of Food Protection 51 419 423 1988 Richard J and T P Labuza
19. precipitates out of the solution Stir periodically for 24 hours It is important to have precipitate at the bottom of the solution in order to assure a saturated solution Verifying Calibration Choose a salt solution from Table 1 and prepare it as previously described The solution should be at ambient temperature for accurate measurements Load a sample cup half full with the solution and place it in AquaLab s sample drawer Take a measurement of its If the reading of the salt standard is consistently higher or lower than the given value a linear offset has occurred An unstable reading signifies that the AquaLab Manual Water activity Measurement 19 chamber has been contaminated and needs to be cleaned see chapter 10 For example saturated solution of NaCt should read 755 at 20 C if the solution of NaCl reads 759 a linear offset has occurred To adjust for a linear offset locate the linear offset adjustment potentiometer on the front panel of the instrument Place your salt solution sample in AquaLab and take a reading Use this reading to adjust the offset Do not turn the knob but rather adjust the offset while is still beeping Use small screwdriver to turn the potentiometer clockwise to increase the number on the display or counter clockwise to decrease it until it gives the correct reading Note It is important to use only pure samples of distilled wate
20. than 03 The instrument cannot read samples AquaLab Operator s Manual Water activity Measurement with an less than 03 The unit also reads LO if the instrument has not detected the formation of dew on the mirror during one complete cycle This is an indication of contamination and the instrument should be cleaned see chapter 10 30 Operator s Manual Water activity Measurement ng a 8 Temperature Control AE In the past water activity instruments have needed temperature control to make accurate sample readings AquaLab takes precision measurements of the air dew point temperature and the sample temperature then uses a microprocessor controlled algorithm to convert these temperatures and other critical information into a water activity reading AquaLab s water activity readings are therefore accurate without temperature control Users constructing and studying moisture sorption isotherms referencing a particular temperature or testing samples more than four degrees Celsius higher than the ambient temperature may want to have temperature control There are several options for controlling AquaLab s temperature One is to use an incubator or hot cold room set at the desired temperature This method is usually satisfactory for users with access to those facilities AquaLab is also available with a temperature control feature which allows it to be connected to an external water bath Temperatu
21. to take on water If the water within a product is tightly bound a microorganism will find it hard to survive If you would like more information about water activity in foods please write to Decagon for more details Decagon has a collection of papers written about water activity in a variety of applications We can send you a copy of the articles or find what you need in the reference section on this manual AquaLab Operators Manual Water activity Measurement Water Activity is the measurement used to determine how tightly water is structurally or chemically bound within product Not only is it vapor pressure ratio but it can also be considered equal to the relative humidity of air in a sealed chamber which is equilibrated with a product AquaLab was created to measure the of a product a influences color odor flavor texture and shelf life of a product If is not controlled the quality and safety of a product suffer AquaLab uses the chilled mirror dew point technique to measure the of a product This technique is primary measurement method of relative humidity When a sample is measured with a stainless steel mirror within the chamber is repeatedly cooled and heated while dew forms and is driven off The instrument s fan circulates air in the sensing chamber speeding up the equilibration process Each time dew forms on the mirror AquaLab measures the temperature and calcula
22. water swollen polymers In Jellinek G Ed Water structure at the water polymer interface New York London Plenum Press 1972 AquaLab Operators Manual alcohols 12 24 49 AquaLink 33 35 beep 26 27 28 beep continuously 26 28 C calibration 5 12 17 18 43 case fan 27 32 chilled products 32 chilled mirror 11 cleaning 38 40 42 43 49 fan filter 42 sensor chamber 38 coated foods 23 coatings 23 computer 33 35 36 Customer Service 6 47 CX 2 1 5 12 25 30 51 2 12 27 30 32 51 Water activity Measurement 65 D dehydrated 12 24 dew point 11 17 28 30 dried foods 23 dry samples 26 dry substances 12 E Extended warranties 46 F fan blade 39 40 49 fan filter 32 42 43 fuse 14 15 47 48 G glycerol 12 49 H HI 28 L limitations 12 linear offset 17 19 21 43 44 50 51 53 LO 25 28 40 49 Load 15 load samples 18 27 Load Read knob 23 Loaner Service 46 location 13 15 O rings 41 42 AquaLab Operator s Manual Water activity Measurement offset 32 output 33 outside coatings 22 printer 33 35 propylene glycol 12 24 49 R reading 18 24 30 false 18 44 28 28 times 12 22 26 water activity 18 19 22 25 26 28 30 31 relative humidity 9 11 17 repairs 22 46 Return Materials Authorization RMA 45 5 232 33 35 5 solution 18 23 52 sta
23. 03 the instrument s sensors have probably been contaminated and will need to be cleaned or serviced Please refer to chapter ten for more information Messages AquaLab will beep once when the knob is turned to the Read position This indicates that the sample has been properly loaded and the instrument is beginning to take a reading AquaLab will beep continuously and the decimal points on the display screen will flash at the end of a reading to indicate that the process is complete The beep and flash will continue until the knob is turned to the open load position The and temperature will remain displayed until the knob is again to the read position or the power is interrupted AquaLab will beep continuously when a sample is loaded if the sample temperature is more than four degrees higher than the chamber The sample should be removed from the instrument and allowed to cool The AquaLab could also be warmed to the temperature of the sample Remember 43 is AquaLab s upper temperature limit the dew point temperature is higher than the sensor temperature AquaLab s display will show a reading of HI This typically means that the sample temperature is much higher than the chamber temperature Once the sample is cooled so that the AquaLab doesn t beep when the knob is in the open load position the reading can be repeated reading of LO is displayed if the of a sample is lower
24. AquaLab Operator s Manual Water activity Measurement AquaLab Model CX 2 Water Activity Measurement Call us Customer Service 800 755 2751 Pacific Decagon Operators Manual Revision 2 2 AquaLab Operator s Manual Water activity Measurement AquaLab Manual Water activity Measurement 3 1 Introduction 5 About This Guide 5 Customer Service Information een 6 Warranty RR 7 Note to Our Readers eene 7 Sellers Liability een 8 2 Water Activity in Foods eren 9 3 About AquaLab 11 4 Getting Started 13 Checking Equipment Choosing Location Checking and Changing Voltage Settings EK Preparing AquaLab for Operation 15 5 Linear Offset and Salt Standards 17 Why Verify Linear Offset 17 When to Verify Linear Offset 17 How to Verify Linear Offset Preparing a Salt Solution Verifying Calibration sese eren 6 Sample Preparation een 22 Materials Needing Special Preparation 23 Coated
25. Determination of the Water Activity of some Heference Solutions Culture Media and Cheese using Dew point Method University of Minnesota Department of Food Science and Nutrition St Paul MN 55108 AquaLab Operator s Manual Water activity Measurement 63 Roa Valentin and Maria S Tapia de Daza Evaluation of Water Activity Measurements with a Dew Point Electronic Humidity Meter Academic Press Limited 1991 Rockland Saturated salt solutions for static control of relative humidity betwen 5 C and 40 C Analytical Chemistry 32 10 1375 1376 1960 Rockland L B and S K Nishi Influence of water activity on food product quality and stability Food Technology 34 42 51 59 1980 Saguy and B Drew Statistical calibration of instruments using water activity determination as an example Journal of Food Science 52 767 771 1987 Scott V N and D T Bernard Influence of temperature on the measurement of water activity of food and salt systems Journal of Food Science 48 552 554 1983 Seiler D A L The mould free shelf life of bakery products Bulletin 1979 2 April 71 74 Snavely M J J Price and W Jun A Comparison of Three Equilibrium Relative Humidity Measuring Devices Drug Development and Industrial Pharmacy 16 8 1990 pages 1399 1408 Stamp J 5 Linscott C Lomauro and T P Labuza Measurement of water activity of s
26. Dried Foods 23 Dehydrated Foods 2 Volatiles MM Low Water Activity 25 Products at Temperature 25 7 Taking A Reading 26 27 Messages 28 AquaLab Operator s Manual Water activity Measurement 8 Temperature Control Important Hints Concerning the CX 2T 32 9 Computer and Printer Interface 33 Equipment enenatis 33 Output Format Configuring and Using the Printer 34 Sending Data to a Computer 35 Backing Up and Running AquaLink from Floppy Disk Installing AquaLink to the Hard Drive 85 Connecting the RS 232 Cable OO Collecting Data Running AquaLink 1 10 Cleaning and 38 Tool List m RR Cleaning the Sensor Chamber 88 Cleaning the Fan Filter 42 Checking the Calibration enne 43 11 Return and Repalt esee eene 45 Repair and Labor Costs 46 Extended Warranties 46 Loaner
27. It says all we of Betty and Bob s I don t think need to clean era AquaLab is AquaLab s Kimwipes have been to service sensorsare invented yet ee how amazed 2 they at the kimwipe 4 convenienoe tweezers MS water We Keep it clean have Never use all that stuff pressurized or UU g canned air for already cleaning It will ahaaa uide MISI ar vp ag In that case use any lint free cloth See who s on the phone while I remove the 8 screws holding on AquaLab s top and the 4 screws inside the block assembly First I ll remove the four screws on each side Bob s obviously confident He doesn t even come unhinged when he hears about the mysterious phone call Next I remove the 4 screws on the sensor block was headquarters A mysterious government agency will be here shortly to perform a mysterious food inspection E VH gt _ T What Mysterious inspections something apart and it s jcrammed full of gooey food pe gunk Bob We re talking serious business This 18 crisis 1 Gooey gunk is serious business We need this AquaLab machine to save millions of dollars and innocent victims and most importantly our jobs ET
28. Water activity Measurement charcoal sample to clean out the remaining propylene glycol Another option is to clean the chamber as described in chapter 10 Low Water Activity Products with an of less than 03 cannot be accurately measured However samples with such low values are rare When a sample s value is less than 03 will display the error message LO on the screen If fhe sample being measured is not extremely dry go to the Troubleshooting section of this guide for other possible explanations Products Not at Room Temperature Products which are colder than the instrument need to be warmed to ambient temperature before a fast accurate reading can be made Rapid changes in temperature over short periods of time will cause the a readings to ramp up or down until the temperature stabilizes Because the CX 2 is always comparing its previous and current result the instrument will not terminate the read cycle until its compared readings are less than 0 001 apart Initial readings on cooler samples shouid not be averaged Such measurements will not be accurate When the temperature stabil zes within one or two degrees of the chamber temperature the operator can proceed with normal measurements 25 AquaLab Operator s Manual 26 Water activity Measurement 7 Taking A Reading m Taking a reading with AquaLab is very simple Turn the sample drawer knob to the Open Lo
29. ad position and open the sample drawer Place a sample cup half filled with the prepared sample in the drawer Check the top lip of the cup to make sure that it is free from contamination Slide the drawer carefully closed to prevent spiashing liquid samples onto the block and causing contamination Turn the knob to the Read position to seal the sample cup with the chamber This also starts the read cycle AquaLab will beep once to let you know the read cycle has begun AquaLab will begin to take readings In 30 45 seconds the first measurement of and the temperature will appear on the display Slightly longer reading times may be required for very dry samples AquaLab will repeat readings until two consecutive readings are within 0 001 of each other The instrument crosses the dew threshold numerous times to ensure the accuracy of readings When the instrument begins to beep continuously and the decimal points flash the reading is complete The display will show a final and temperature measurement Note Any large change of between consecutive AquaLab Operators Manual Water activity Measurement samples may require extra time to reach equilibrium as some atmosphere is retained from the previous sample Cautions Never leave a sample in AquaLab after a reading has been taken If left too long the sample may contaminate the instrument s chamber Never leave a sample in AquaLab overnight Ne
30. ait solutions and foods by several electronic methods as compared to direct vapor pressure measurement Journal of Food Science 49 1139 1142 1984 64 AquaLab Operator s Manual Water activity Measurement Stoloff L Calibration of water activity measuring instruments and devices Collaborative study Journal of Association of official Analytical Chemists 61 1166 1178 1978 Taoukis W Breene and T Labuza Intermediate moisture foods Advances in Cereal Science and Technology 9 91 128 1988 Troller J A Statistical analysis of ay measurements obtained with the Sina Scope Journal of Food Science 42 86 90 1977 Troller J A Methods to measure water activity Journal of Food Protection 46 129 134 1983 Troller J A and J B Christian Methods In Water Activity and Food New York Academic Press pp 13 47 1978 Vermeulen and J Wessels Chitin biosynthesis by a fungal membrane preparation European Journal of Biochemistry 158 411 415 1986 Vos T and T P Labuza Technique for measurements of water activity in the high aw range Journal of Agricultural and Food Chemistry 22 326 327 1974 Voysey Dr Philip Evaluation of the AquaLab CX 2 System for Measuring Water Activity Digest Microbiology Section 124 February 25 1993 Yasuda H G Olf B Crist C E Lamaze and Peterlin Movement of water in homogeneous
31. amber causing accuracy errors To read chilled products the entire instrument must be chilled For more detailed information regarding the operation of the CX 2T please refer to Appendix A AquaLab Operators Manual Water activity Measurement 33 Water activity data collected with AquaLab can be sent to a computer for further analysis or printed on a printer as it is measured If you are collecting data for further analysis data storage or printing may save time To do 50 AquaLab s HS 232 output port must be connected to the serial port of a computer or printer using an RS 232 cable available from Decagon Equipment Included with the RS 232 accessory kit are AquaLink software to connect to your computer RS 232 cable Printers good quality low cost printer with serial port is also available as an accessory For pricing and information contact Decagon Many printers for use with a personal computer have serial ports and will interface with AquaLab if you are not sure whether your printer has a serial port refer to ihe printer manual Output Format AquaLab data is output in comma delimited ASCII format Each time a measurement is made with the instrument one line of information will be sent to the computer or printer On a printer each line contains four values For example 34 AquaLab Operator s Manual Water activity Measurement 187 405 20 77 6 The first value is fro
32. anada will not have to change AquaLab s voltage setting Users in other areas particularly those which supply power at 220 or 240 volts 14 AquaLab Operator s Manual Water activity Measurement should check the voltage setting before using the instrument AquaLab may sustain damage if the voltage is incorrectly set AquaLab will operate at both 50 and 60 Hz and any voltage near 110 120 220 or 240 volts 15 factory preset to operate at 120 volts The voltage setting can easily be changed by rotating a tab inserted in the power module The power module is located in the lower right corner of the instrument s back panel Location of Power Module on back panel Unplug AquaLab s power cord before checking or changing the voltage Slide the plastic cover to the left to expose the fuse chamber Hemove the fuse by pulling out on the fuse pull lever Carefully place the fuse to one side Diagram of the Power Module When the fuse has been removed the voltage tab a smail light colored board lying on the bottom of the chamber will be visible The current voltage setting is displayed in the back left hand corner If this voltage matches the voltage of the power source to be used AquaLab Operator s Manual Water activity Measurement 15 replace the fuse and continue setting up AquaLab If the two do not match the voltage tab needs to be changed to match the correct line voltage To change the voltage
33. ar offset AquaLab Operator s Manual 54 Water activity Measurement fable 2 Water Activity of Saturated Sample Temp Table 2 shows saturated solutions of at different temperatures AquaLab Operator s Manual 55 Water activity Measurement BE 9t Ge re 5 1917 es jo 5 DE Water Activity 24 26 Figure 2 of GM NaCl Solution 28 30 32 Temperature 34 36 95 enuen qe Tqenby 57 AquaLab Operator s Manual Water activity Measurement 8t ze t 82 e ie anba 92 vc m T 51001 0200 JAJEM AquaLab Manual 58 Water activity Measurement 1 r I I 1 1 I 1 1 1 1 1 1 L 1 5 1 L 1 1 r I 1 1 1 1 I 1 L 1 1 1 e ry a 1 Un S 1 4 L 1 1 1 ie 4 1 L i 4 gt 1 o 2 1 1 1 D 1 1 1 LI 1 1 LI E 1 1 e I 1 1
34. ation of water activity measurement obtained with the Vaisala Humicap humidity meter Journal of Food Science 48 534 538 1983 Franks Felix Ph D Water Activity as a Measure of Biological Viability and Quality Control Cerea Foods World September 1982 page 403 407 Greenspan L Humidity fixed points of binary saturated aqueous solutions Journal of Hesearch of the National Bureau of Standards Section A Physics amp Chemistry 81 89 96 1977 Hale S and J D Legan Pitfalls of measurement FMBAA Bulletin 1988 No 2 April 68 86 Hand Larry Controlling Water Activity and pH in Snack Sticks Meat Marketing amp Technology May 1994 page 55 56 Heidemann Dorothy and Paul J Jarosz Preformulation Studies Involving Moisture Uptake in Solid Dosage Forms Pharmaccutical Rescarch Vol 8 No 3 1991 Research Article Plenum Publishing Corpontion 1991 Jakobsen M Filament hygrometer for water activity measurement interlaboratory evaluation Journal of Association of Official Analytical Chemists 66 1106 1111 1983 Kanada P B and J 5 Pai Moisture sorption method for hygroscopic samples using a modified proximity equilibration cell Journal of Food Science 53 1218 1219 1988 Kitic D Favetto J Chirife and S Resnik Measurement of water activity in the intermediate moisture range with the Novasina Thermoconstanter AquaLab Operator s Manual Water act
35. bers of the scientific community We apologize for this However this manual was written to help aid the end user understanding the most basic concepts and theories of water activity thus enabling them to use our instrument with confidence Every has been made to ensure that the topics are correct and scientifically sound 7 Aqual ab Operators Manual Water activity Measurement Seller s Liability Seller warrants new equipment of its own manufacture against defective workmanship and materials for a of one year from date of receipt of equipment the results of ordinary wear and tear neglect misuse accident and excessive deterioration due to corrosion from any cause not to be considered a defect but Seller s liability for defective parts shall in no event exceed the furnishing of replacement parts f o b the factory where originally manufactured Material and equipment covered hereby which is not manufactured by Seller shall be covered only by the warranty of its manufacturer Seller shall not be liable to Buyer for loss damage or injuries to persons including death or to property or things of whatsoever kind including but not without limitation loss of anticipated profits occasioned by or arising out of the installation operation use misuse nonuse repair or replacement of said material and equipment or out of the use of any method or process for which the same may be employed The use of this e
36. blade can be replaced by the user 4 The mirror or the cooler may have become detached from the block Return the instrument for repair Refer to chapter eleven for return and repair instructions Probiem When measuring samples AquaLab displays a LO message Solution 1 The mirror is dirty Refer to chapter 10 for cleaning instructions 50 AquaLab Operator s Manual Water activity Measurement 2 AquaLab is not detecting the formation of dew on the mirror Refer to chapter 10 for cleaning instructions 3 One of the chamber components may be damaged AquaLab must be returned for repair Refer to chapter 11 for return and repair instructions Probiem Water activity readings on standard solutions are too high and the potentiometer can t be adjusted any further Solution The thermopile which measures sample temperature has probably been contaminated Refer to chapter 10 for cleaning instructions The potentiometer twists all the way around making it difficult or impossible to adjust for a linear offset Solution Do not force the potentiometer It was designed to only rotate one full turn If you can twist it all the way around itis broken and AquaLab must be returned for repair See chapter 11 for return and repair instructions Problem While using AquaLab at elevated temperatures the instrument displays zeroes or garbage on the screen Sotution The water bath or environmental te
37. blem Readings seem much slower than usual or readings are very unstable and inconsistent changing significantly between successive tries Solution 1 Some foods absorb or desorb moisture so slowly that AquaLab Operator s Manual Water activity Measurement 49 measurements take longer than five minutes See chapter six for more details 2 substance that contains propylene glycol will cause unstable readings The propylene glycol vaporizes on the surface of the chilled mirror altering readings We recommend that you not use AquaLab to measure samples containing propylene glycol However measurements may be made without risk of damage to AquaLab Please contact Decagon at 1 800 755 2751 with any questions concerning the measurement of propylene glycol Note As yet propylene glycol is the only volatile known to act unpredictably Glycerol and almost all other alcohols used to flavor foods can be measured without problems see chapter 6 Some aeromatics have aslo caused unstable readings call Decagon if this seems to be a problem 3 If standard salt solutions take an equally long time to read a fan blade inside the block may be broken This is especially likely you have just cleaned the instrument and removed the fan from the block assembly First make sure that the fan motor is running in the read mode it is check the fan blade If there is a problem with the blade contact Decagon at 1 800 755 2751 A broken fan
38. ds are to be sensory tested Foods held over K acetate will take on a vinegar like flavor and foods held over sodium nitrate absorb nitrous oxide which catalyzes lipid oxidation Labuza et al 1984 Note Because lithium chloride is so hard to keep in AquaLab Operator s Manual Water activity Measurement 21 Saturation over 5 temperature fluctuations we allow an accuracy of 0 006 when we use it to verify the linear offset Lithium chloride and other salts this dry should not be used to adjust the linear offset as they easily come out of saturation by taking on water They are good however for verifying that the offset is correct 22 AquaLab Operator s Manual Water activity Measurement m 6 Sample Preparation AquaLab will continually provide accurate water activity measurements as long as it is not internally contaminated Careful preparation of samples will lengthen time between necessary cleanings and help you avoid costly repairs and down time To prepare a sample follow these steps Make sure the material to be measured is homogeneous Samples that combine wet and dry ingredients i e muffins with raisins or samples that have outside coatings i e fried foods can be measured but will take longer to For these items AquaLab may take more than 5 minutes to give an accurate reading or may require multiple readings of the same sample Measuring the amp of these types Of foods i
39. five for offset correction instructions If after adjusting the offset AquaLab is still not correctly reading samples please contact Decagon for technical assistance AquaLab Operator s Manual Water activity Measurement 45 Should anything ever wrong with AquaLab Decagon will repair it Just follow the instructions below for returning the instrument Before returning AquaLab call our office at 1 800 755 2751 for a Return Materials Authorization Number and return shipping instructions Include this number on all correspondence regarding the repair of your instrument With your return please include your RMA a complete return address the name and department of the person responsible for AquaLab a repair budget for non warranty instruments and purchase order number If possible the CX 2 should be shipped back to us in its original cardboard case If this is not possible there are several things that will help in getting your instrument here safely or at least allowing you to put in a claim to the carrier for damages 1 Put your CX 2 in a plastic bag to avoid disfiguring marks from the packaging 2 Do not include your power cord when shipping the CX 2 back we have plenty here at the factory 3 Use a box that has af least four 4 inches of space between your instrument and the wall of the cardboard box on ail sides 4 Pack the box moderately tightly with springy packing material preferably
40. he balance Pee ee pi Ce et ot P 1 T ed Agent X places AquaLab on 3 the time transporter O A Thanks to the AquaLab CXS Time save humanity from microbes tainted Machine food causing poor nourishment and Operator 2nd tasteless comestibles class transfer 8 water activity meters back in time i cm Bob speaking of water activity this instrument just mysteriously appeared on our test bench Did you put it here zl BM 3 Pro ark inthe ES Betty s co worker fiddles with gizmos on the bench 1 m E b d y NH 9 NE x x B ER E 3 h Ho 4 B L Ww 4 4 21 ELENEN hu 5 7 Ed DM a E a a Pa EL
41. ith water activity reading near that of the samples you wish to measure Figure 4 shows the effect of temperature on water activity when the linear offset is not corrected The data was collected at different temperatures over a period of one month and then averaged to produce this graph Without adjusting the offset these are the types of results to expect o2 AquaLab Operator s Manual Water activity Measurement As temperature increases readings become more repetitive especially when measuring water The same is true for the 6M NaCl This is because it is possible to keep stable solutions of water and 6M NaCl But as table 1 displays the saturated LiCl solution showed continual decrease in water activity as the temperature increased It is difficult to maintain a saturated salt solution and it js therefore more subject to change with temperature AquaLab Operator s Manual Water activity Measurement 53 fable 1 Water Activity of a Sample temp 0 76052 23 144 0 sees 1 23 240 0 75992 0 76010 29 914 0 76053 29 921 0 76030 29 935 0 76009 9 76007 EEG Di 41 0 75986 38 962 0 75978 39 027 0 75974 39 054 0 75983 39 063 0 75985 39 072 0 75996 39 084 0 75996 39 089 Table 1 shows water activity of 6M NaCl at different temperatures In this table the shading indicates which samples were used to correct the line
42. ivity Measurement 61 humidity meter Lebensmittel Wissenschaft und Technologie 19 297 301 1986 D D C Pereira Jardim G J Favetto S L Resnik and J Chirife Theoretical prediction of the water activity of standard saturated salt solutions at various temperatures Journal of Food Science 1037 1042 1986 Kress Rogers Dr Erika Food quality measurement Food Industry News September 1993 page 23 26 Kuntz Lynn A Keeping Microorganisms in Control Food Product Design August 1992 page 44 51 Kurkela and Water sorption of Northern Milk Cap mushroom Lactarius trivialis Lebensmittel Wissenschaft und Technologie 17 285 288 1983 Labuza T P Moisture gain and loss in packaged foods Food Technology 36 92 97 1982 Labuza P S and Y Lee Water activity determination a collaborative study of different methods Journal of Food Science 41 910 917 1976 Labuza Theodore P Ph D and Contreras Medellln Prediction of Moisture Protection Requirements for Foods Cereal Foods World July 1981 Vol 26 7 335 343 Paakkonen Equilibrium moisture content and the state of water in processed Northern Milk Cap mushroom Lactarius trivialis Unpublished manuscript Paakkonen Effects of different components of the Northern Milk Cap mushroom Lactarius trivialis
43. ke sure your data has been saved and then exit AquaLab Operator s Manual 38 Water activity Measurement 1 Cleaning Maintenance _ It is important to keep AquaLab clean to maintain the accuracy of its readings Dust and debris can contaminate the chamber and must be removed regularly When your instrument needs to be cleaned carefully follow the instructions below Or call our toil free number for technical assistance Tool List Tweezers Distilled Water Lint free or sizing free tissue Kimwipe Phillips screwdriver Cleaning the Sensor Chamber Unplug AquaLab Remove the eight screws that secure the cover located on each side of the AquaLab Remove the Cover T LES Location of the Case Screws AquaLab Manual Water activity Measurement 39 Using a phillips screwdriver remove the four screws that secure the fan assembly to the block Location of the Fan Assembly Block Screws Carefully remove the fan assembly by lifting it straight up from the block There is a small fan on the under side of this lid The little blades break easily and AquaLab will not work properly when one breaks Treat this fan with care AquaLab s sensor mirror is located on top of the block between two round ports Wrap a small piece of lint free tissue around the end of the tweezers Dip this cloth in the distilled water so that it is wet but not soaked Gently wipe the
44. l i h h d 4 E k Right Ch L AquaLab verifies our Pau War a F Tg un o 3 a gt 3 amp 2 3 5 Let s check this place out oh de 1 Until next time m t IT sure glad t hard to Thanks to AquaLab wasn 1 4 Whew We Hey Where did the AquaLab water activity meter go This AquaLab is one Vct of 8 4 emergeneyloaners I fess couldn t leave it with E Bob and Betty Not until they re future Decagon customers Besides it s needed elsewhere wherever the danger of bad food taste threatens 25 48 E nD 2 9501 NE
45. m the datalogger and is not relevant to user measurements The second is the water activity value The third is the temperature in degrees Celsius at the time of measurement and the fourth is the time in hours and minutes since AquaLab was turned on If AquaLab is left on for more than 24 hours the clock will reset to zero On a computer each line of output contains three values For example 12 40 24 405 20 77 Here the first value is the computer time the second the sample water activity and the third is the sample temperature Configuring and Using the Printer If you purchased a printer as an AquaLab accessory it will come configured to receive ASCII files and with dip switches set to match AquaLab s communication protocol If you are using your own printer you must configure it to receive ASCII files Configuration procedures differ printer to printer check your printer s operator s manuat for specific instructions Configure the printer to match the following communications protocol Baud rate 300 None Data Bits 8 Stop Bits 1 AquaLab Operator s Manual Water activity Measurement 35 Once the printer has been configured it is ready to print Connect AquaLab to the printer using the 5 232 cable Turn on the printer and begin making measurements with AquaLab Each time a water activity endpoint is reached a line of data which includes datalogger information water activity temperature and
46. mperature is above 409 C Cool the water bath and lower the environmental temperature AquaLab will not be damaged by these higher temperatures if the problem persists after cooling carefully clean the block If this doesn t solve the problem please contact Decagon for technical assistance at 1 800 755 2751 or aqualab decagon com Aqualab Operators Manual Water activity Measurement 51 AquaLab C 2 allows for applications where temperature control is necessary or desired permitting the user to take readings across a larger range of temperatures As the temperature of the CX 2T changes there is a slight variation in water activity readings Figure 4 This variation is expected and it can be adjusted by correcting the linear offset Tables 1 and 2 show water activity readings collected at different temperatures At each temperature was measured and the first three measurements were used to correct the linear offset These measurements were followed by corrected measurements of saturated LiCl solutions and distilled water measurements were made on the same day and this data was used to create figures 1 2 and 3 In figure 2 the readings used to correct the linear offset are enclosed in brackets The remaining readings in each figure are corrected for linear offset and display the CX 2T s level of repeatability As with the CX 2 it is a good idea to adjust the linear offset of the CX 2T using a sample w
47. ncounter difficulties Common problems and their solutions are listed below If your problem isn t listed here or if you can t seem to solve it call our Customer Service number at 1 800 755 2751 robiem won t power up Solution 1 The power cord may have come loose from the instrument or the wall 2 A power or component surge may have caused AquaLab s fuse to blow To change the fuse follow these instructions Unplug the power cord from the wall and the instrument Locate AquaLab s fuse box on the back panel of the instrument Slide the clear plastic panel to the left exposing the fuse chamber AquaLab Operator s Manual 48 Water activity Measurement Location of AquaLab s Fuse Chamber Pull out on the fuse pull lever Replace the fuse with a 120 V 1 amp fast blow fuse Caution Use of any other fuse type will void AquaLab s warranty Reconnect the power cord and turn the instrument on If the fuse blows again a component surge may be causing the problem Refer to chapter eleven for return and repair instructions Problem The instrument doesn t go to zeros after a short period of time Solution The garbage that shows on the display when AquaLab is first turned on should disappear after about thirty seconds If it doesn t some of the internal components may be damaged or broken Return AquaLab for repair See chapter eleven for return and repair instructions Pro
48. ndard 17 18 9 11 13 18 27 30 32 42 43 50 and salt standards 18 chamber 16 Cups 13 15 18 22 26 drawer 18 drawer knob 15 26 materials 22 measurement 19 22 23 28 51 dry 27 28 preparation 5 22 23 temperatures 22 sample cup 42 sample drawer 30 41 Service 46 T technical assistance 38 44 50 See also Customer Service temperature control 11 12 27 30 31 51 verify 17 21 volatiles 12 24 voltage 13 14 15 voltage settings 13 15 W wet and dry ingredients 22 AquaLab Operator s Manual Water activity Measurement 67 AquaLab Operator s Manual 68 Water activity Measurement 7 tnus f DE NE F AE A T Fa VS atre EL EX DU 8 Professor 300 4 3 8 3 8 x TI Credis A Brad wd e deDecagon s E a OR E Wm HN 1 gt o E Wo Rod Nm mom b B3 s F h m m JF m 4 E ET a s E 1 o HLOO PM 3 Et amp EE Annee
49. ng for the coating Another way to speed up readings on coated and dried foods is to restart AquaLab during its reading cycle You do this by first starting the read cycle listen for the beep and watch for the zeros then waiting 60 seconds At about 60 seconds turn the open read knob about half way to open and then back to read The AquaLab should beep again and the display should show ail zeros If this is not the case turn the knob a little further toward open This action essentially speeds up sample equilibration by restarting the read cycle while keeping the chamber sealed Dehydrated Foods Some dehydrated foods because of their moisture sorption characteristics also have increased reading times AquaLab may require up to ten minutes to reach an accurate measurement of a Nothing can be done to decrease the reading times of some dehydrated foods Volatiles AquaLab will give accurate readings on almost all alcohols used to flavor foods with the exception of propylene giycot Products containing propylene glycol will not damage the instrument but values for those products will not be accurate This is because propylene glycol condenses on the mirror during the reading process but never evaporates from the mirror as water does The very first reading will be somewhat accurate but subsequent readings will not be After propylene glycol has contaminated the chamber run an activated AquaLab Operator s Manual
50. o good idea to check the offset with a standard of similar when the general water activity range is changing Checking the a of a standard solution will alert the operator to the possibility of contamination of the unit or shifts in the linear offset from other causes How to Verify Linear Offset The linear offset of AquaLab may be verified by 18 AquaLab Operator s Manual Water activity Measurement choosing a salt standard that corresponds to the of the sample to be measured To find the correct salt standard for your sample please refer to Table 1 which shows readings for a variety of salts at various temperatures From this table choose a salt with near that of the sample you be reading Note is best to set the linear offset with a solution whose no lower than 0 500 Once the offset is set at the higher water activities the drier samples will read accurately if is not necessary to set the offset with a sample as dry as those you will be reading AquaLab s reading should be within 003 of the given value for the saturated salt if the instruments does not match the given value a linear offset has probably occurred Refer to the next page for instructions on adjusting linear offset Note Two readings of the salt solution should be taken to ensure accuracy Preparing a Salt Solution Mix a reagent grade salt in distilled water stirring constantly Add salt until it
51. packing peanuts 46 AquaLab Operator s Manual Water activity Measurement 5 Tape the box in both directions so that it cannot be broken open in shipment 6 include necessary paperwork so that the instrument can be processed quickly This includes Name full address phone fax RMA and in addition to an explanation of the problem Pack AquaLab carefully as instructied and return to RMA XXXX Decagon Devices Inc 1525 Merman Drive Pullman WA 99163 Repair and Labor Costs If your instrument is under warranty there is no charge for repairs or replaced parts If your instrument s one year warranty has expired there will be a 50 minimum repair charge plus shipping costs Additional labor is billed per hour and rush work is extra Extended Warranties Extended warranties are available for AquaLab Please contact Decagon for more information about this service Loaner Service Decagon has loaner instruments for those whose AquaLabs are being repaired There is a limited number of loaner AquaLabs They are granted on need and first come first served basis This program helps you if your AquaLab needs service during critical operations AquaLab Operator s Manual Water activity Measurement 47 shc Trouble AquaLab is a high performance low maintenance instrument and has few problems if used with care But even the best operators using the best instruments may occasionally e
52. quipment constitutes Buyer s acceptance of the terms set forth in this warranty There are no understandings representations or warranties of any kind express implied statutory or otherwise including but without limitation the implied warranties of merchantability and fitness for a particular purpose not expressly set forth herein AquaLab Operator s Manual Water activity Measurement Water Activity a is a water energy measurement It is an indication of free water in a sample free referring to the water molecules in a product that are not chemically or physically bound a or Equilibrium Retative Humidity is measured as a ratio of water vapor pressure above any sample to the water vapor pressure of pure water at the same temperature Products with no free water will have an of 0 000 while a product such as pure water will have an of 1 000 There are two basic types of water analysis The first is a quantitative or volumetric analysis to determine the water content of a product Typically the product is first weighed then oven dried and reweighed to measure its total water content But merely knowing the water content of a product does not give an indication of the physical properties of that water The question is not how much water is in a product but how much of that water is available to be used by microorganisms or other destructive agents The second type of water analysis the measurement
53. r and saturated salt when testing for a linear offset Location of potentiometer on AquaLab s front panel Run the saturated salt sample again to ensure that the offset has been adjusted Caution Be extremely careful when adjusting the potentiometer it is easily broken and is designed to handle only one complete turn Turning the potentiometer past its stops will damage it Use a small screwdriver that fits the slot to adjust ihe potentiometer Do not use a screwdriver that does not fit 20 AquaLab Operators Manual Water activity Measurement If for some reason you cannot adjust the potentiometer to the correct reading refer to the Troubleshooting section of this manual Verifying and adjusting the linear offset will ensure that AquaLab will read accurately there continues to be problem with accuracy clean the sensor chamber chapter 10 or call Decagon at 1 800 755 2751 Magnesium Chloride 328 002 Potassium Carbonate 32 003 432 004 Sodium Chloride 7554 001 752 001 Potassium Chloride 851 003 843 003 Potassium Sulfate 976 005 973 005 Distilled Water 1 000 003 1 000 003 Table 1 Water Activity Table for Selected Saturated Solutions Adapted from Greenspan 1977 The numbers in this table have been rounded to the nearest thousandth Note Some salts may become toxic if they contaminate the food being sampled KBr NaNO and K Cr 0 should not be used if humidifying foo
54. re control can be purchased as a feature on the AquaLab model CX 2T instrument or retrofit in an existing AquaLab model CX 2 Water is circulated from a user provided water bath through the sample drawer base and a temperature tray The temperature tray holds two samples and equilibrates them to the temperature of the drawer This speeds the reading process However the water bath should only be used for higher than ambient samples The temperature of the AquaLab Operators Manual Water activity Measurement 31 whole instrument needs to be altered when reading samples colder than AquaLab The coldest ambient temperature of AquaLab and the cold samples should not be below 5 If you have purchased AquaLab with the temperature control feature you should have received fit with water ports and interna circulating base Temperature Tray model 21128 Tygon tubing for connections 4 Elbows 2 with valves for the rear of AquaLab 2 without valves for the sample tray The drawer should be placed in the feed loop from the water bath and the temperature tray should be placed in the retum path This keeps sample temperatures below the block temperature to ensure that unwanted condensation does not occur Water Flow Water Bath Diagram of AquaLab model CX2T Note Water temperature settings and water circulation are controlled by the user provided water bath 32 AquaLab Operator s Manual Water
55. rews clockwise until they are secure four screws should be tightened equally to form seal between the fan and the block Note These screws may resist tightening If there is any resistance do not force them Turn the screw counterclockwise until a little drop is felt and then turn it clockwise to tighten If these screws are forced it will cause stripping and they will not fully tighten This in turn will prevent the chamber from sealing as it should and any following readings will be inaccurate Adjust the screws so that there is pressure on the sample cup when the knob is turned This ensures that the chamber is sealed Test the tightness of the screws by placing an empty sample cup in the drawer and turning the knob to read If the knob is too easy to turn the screws need to be tightened Your instrument is equipped with O rings under the screws don t compress them The O rings help ensure proper sealing of the chamber during the read cycle without over tightening of the screws Repiace AquaLab s outer case Make sure the holes in the case align with the holes in the main unit before inserting and tightening the screws Note The outer case should always be in place when measuring For ease of cleaning the cover screws could left out or reduced to one or two Cleaning the Fan Filter AquaLab s fan filter limits intake of debris from the environment The accuracy of the instrument is dependent on a
56. s however some materials may require longer reading times These materials need some special preparation to ensure quick accurate readings find out whether special sample preparation is necessary take a reading If the reading takes longer than six minutes remove the sample and take a reading of a saturated salt solution This will ensure that the sample itself is causing the longer reading time If the saturated salt also takes longer than six minutes to read also check the Troubleshooting section for more information Coated and Dried Foods Foods that have coatings such as sugar or fat often require longer reading times This is because it takes longer for the samples to equilibrate if this is the case it is better simply to allow the sample to take more time to read To reduce the time needed to take an reading crush the sample before putting it in the sample cup Crushing increases the surface area of the sample thus decreasing reading times However keep in mind that crushing some foods may alter their readings For 24 AquaLab Operator s Manual Water activity Measurement example a candy may have a soft chocolate center and a hard outer coating The reading for the center and the outer coating will be different so evaluate which part of the sample you need to measure before crushing When the candy is crushed the will represent that of the center whereas leaving the candy whole will give readi
57. s discussed more in depth later in this chapter see special preparation instructions Spread the sample material in the bottom of a disposable sample cup covering the bottom of the cup if possible A larger sample surface area increases instrument efficiency by providing more stable infrared sample temperatures It also speeds up the reading by shortening the time needed to reach vapor equilibrium Do not fill the sample cup more than half full Over filled cups will contaminate the chamber Make sure that the rim and outside of the sample are clean Wipe any sample material from the rim of the AquaLab Manual Water activity Measurement 23 cup with a clean tissue Material left on the rim or the outside of the cup will contaminate the chamber and will be transferred to subsequent samples The rim of the cup is pushed up to form a vapor seal with the sensor block when the Load Read knob is turned to Read any sample material left on the cup rim will be transferred to the block and may prevent this seal and contaminate future samples If the same sample will be read at some other time put a disposable lid on the sample cup to restrict water transfer To seal the cup place tape completely around the cup iid junction It is necessary to seal the cup if it will be a long time before the measurement is made Materials Needing Special Preparation AquaLab reads most materials in two to five minute
58. t all 05 AquaLab requires a warm up time to equilibrate to the temperature of its surroundings This takes from 15 minutes to an hour This equilibration time is important each time the instrument is turned on so that the temperature of the air inside the AquaLab comes into equillibrium with that on the outside AquaLab s Display Screen when first turned on It can be helpful during this equilibration time to run a few samples as this will warm up the sample chamber For instructions on preparing samples and taking readings refer to chapters six and seven AquaLab Operators Manual Water activity Measurement 17 Why Verify Linear Offset AquaL ab uses the cooled mirror dew point technique for measuring water activity Because this is a primary measurement method of relative humidity no calibration is necessary however it is important to verify the linear offset periodically The electronics used to measure in the instrument are subject to changes that may affect its performance These changes are usually the result of chamber contamination but sometimes the electronic components may degrade or fail Linear offset verification assures the user that AquaLab is performing correctly When to Verify Linear Offset AquaLab s linear offset shouid be verified against known salt standard daily For batch processing the instrument should be checked regularly against a known salt standard of similar It is als
59. t back to you Our fax number is 1 509 332 5158 internet Email Send us the description of your problem question or application Tell us how we can help you Please include the serial number of your AquaLab and its model number Also include your name and where you can be contacted in your communication Send this information to supporte decagon com If you subscribe to Compuserve American On Line Prodigy eWorld or another on line service you may still be able contact us at this address Please contact your service provider for specific instructions If you have a general question about your application with AquaLab please send your email with the above information to aqualab decagon com Operator s Manual Water activity Measurement Warranty AquaLab has a 30 day satisfaction guarantee and a one year warranty on parts and labor To validate your warranty please complete and return the warranty card included with this manual You can retum your warranty information by fax email phone or simply drop the postage paid card into the mail Please include all of the information requested on the warranty card It is necessary for Decagon to have your current mailing address and telephone number in case we need to send updated product information to you Note to Our Headers We understand ihat some of our references to scientific terminology in this manual do not meet the criteria of of the mem
60. tes the sample saving these values to compare to previous values as it repeats its readings When the values of consecutive readings are less than 001 apart the measurement process is complete AquaLab signals by beeping and flashing the decimal points and displays the final and temperature of the product With AquaLab temperature control is unnecessary for 11 12 Operator s Manual Water activity Measurement most applications The change in with temperature for most materials is lass than 0 002 per degree Celsius The CX 2 is ideal for the measurement of products at room temperature However products not at room temperature during the read cycle will equilibrate to the temperature of AquaLab This variable temperature will cause longer reading times as a complete and accurate reading will not be made until the sample and the instrument are within 2 degrees of each other For applications where temperature control is critical AquaLab can be operated in a controlled temperature chamber or room or a 2 Temperature Control Model of AquaLab may be purchased For more information on temperature control please refer to the Temperature Control section of this manual AquaLab is the fastest instrument for measuring giving readings in five minutes or less Its readings are precise providing 0 003 accuracy The instrument is easily cleaned and calibration checks are simple AquaLab has a
61. ver try to move AquaLab after a sample has been loaded Movement may cause the sample to spill and could contaminate the chamber Be especially careful when loading liquid samples sample has a temperature four degrees higher than AquaLab s chamber the instrument will beep to alert the operator to cool the sample Although the instrument will measure warmer samples the readings may be inaccurate The physical temperature of the instrument should be between 5 and 43 At these ambient temperatures AquaLab will measure samples of similar temperature easily and accurately model CX21 with temperature control abilities can read samples at temperatures different from ambient temperature but no higher than 437 When measuring the of powdery samples there are a number of precautions that can be taken to ensure that the chamber will not be contaminated When first loading the sample cover the case fan in the rear of the instrument with a piece of cardboard until the drawer is closed and locked This will prevent the fan which is always on from blowing your sample around on the inside of the instrument Once the sample drawer is all the way pushed in take the card away from the fan 28 AquaLab Operator s Manual Water activity Measurement sample has an lower than 03 AquaLab s display will read If the instrument gives a LO reading for samples with an that is higher than
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