AquaLab 4TE Series Operator's Manual
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AquaLab 4TE Series Operator's Manual

Series 4, water activity meter
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Water Activity Meter
Operator's Manual
For Series 4, 4TE, 4TEV, DUO, and TEV DUO
Decagon Devices, Inc.
Version: February 28, 2014 — 09:24:12

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Summary of Contents for AquaLab 4TE Series

  • Page 1 Water Activity Meter Operator’s Manual For Series 4, 4TE, 4TEV, DUO, and TEV DUO Decagon Devices, Inc. Version: February 28, 2014 — 09:24:12...
  • Page 2 AquaLab Decagon Devices, Inc. 2365 NE Hopkins Court Pullman WA 99163 Phone: 509-332-5601 Fax: 509-332-5158 Website: www.aqualab.com Email: support@aqualab.com or sales@aqualab.com Trademarks AquaLab is a registered trademark of Decagon Devices, Inc. c 2008-2013 Decagon Devices, Inc.

  • Page 3: Table Of Contents

    2.3 AquaLab Model and Options ....2.4 How AquaLab Works ....
  • Page 4 9.1 Measurement Steps ....47 9.2 How AquaLab Takes Readings ... . . 47 10 DUO Operation (Optional) 10.1 Obtaining Product Isotherm Models .
  • Page 5 AquaLab CONTENTS 15.1 Preparing Salt Solution ....100 16 Appendix B 17 Appendix C 18 Declaration of Conformity 19 Certificate of Traceability...

  • Page 6: Introduction

    AquaLab is the quickest, most accurate, and most reliable instru- ment available for measuring water activity. Whether you are re- searching or working on the production line, AquaLab will suit your needs. It is easy to use and provides accurate and timely results.

  • Page 7: Warranty

    Your warranty is automatically validated upon receipt of the instrument. We will contact you within the first 90 days of your purchase to see how the AquaLab is working for you. Seller’s Liability Seller warrants new equipment of its own manufacture against de- fective workmanship and materials for a period of one year from the date of receipt of equipment.

  • Page 8: About Aqualab

    AquaLab 2 ABOUT AQUALAB About AquaLab AquaLab is the fastest and most accurate instrument for measuring water activity, giving readings in five minutes or less. Its readings are reliable, providing 0.003 a accuracy. The instrument is easy to clean and checking calibration is simple.

  • Page 9: Aqualab 4 Duo Specifications

    2 ABOUT AQUALAB AquaLab AquaLab 4 DUO Specifications Moisture Content Repeatability: 0.02% Accuracy to Moisture Content Ref.: 0.1% to 0.5% AquaLab Model and Options Series 4: Uses a chilled-mirror dew point sensor, but lacks the tem- perature control features found in our premium models.

  • Page 10: How Aqualab Works

    five minutes for most samples. The AquaLab 4TEV and 4TEV DUO both use a capacitance humidity sensor to measure the water activity of a sample. The sensor is suspended in the headspace of the chamber and uses a special polymide material sandwiched be- tween two electrodes to sense humidity changes.

  • Page 11: Aqualab And Temperature

    AquaLab and Temperature Samples not read at room temperature during the read cycle will equilibrate with the AquaLab temperature before the water activity is displayed. Large temperature differences will cause longer reading times, since a complete and accurate reading will not be made until the sample and the instrument are within 2 C of each other.

  • Page 12: Chilled Mirror Dew Point Limitations

    Series 4TE models. Chilled Mirror Dew Point Limitations AquaLab limitation is its ability to accurately measure samples with high concentrations (typically > 1%) of certain volatiles such as ethanol or propylene glycol, which can condense on the surface of the chilled mirror.

  • Page 13: Water Activity Theory

    In the AquaLab, you place a sample in a sam- ple cup that seals inside the sample chamber. Inside the sample chamber is a fan, a dew point sensor, a temperature sensor, and an infrared thermometer.
  • Page 14 AquaLab 3 WATER ACTIVITY THEORY Figure 1: Water Activity Diagram adapted from Labuza temperature of the air in the chamber, and the infrared thermome- ter measures the sample temperature. From these measurements, the relative humidity of the head-space is computed as the ratio of dew point temperature saturation vapor pressure to saturation vapor pressure at the sample temperature.

  • Page 15: Water Potential

    A sample at 0.75 a needs to be approximately 4 C above the chamber temperature to cause condensation. The AquaLab warns the user if a sample is more than 4 C above the chamber temperature, but for high water...
  • Page 16 AquaLab 3 WATER ACTIVITY THEORY the same everywhere in the system. Equilibrium between the liquid and the vapor phases implies that (µ) is the same in both phases. It is this fact that allows us to measure the water potential of the va- por phase and use that to determine the water potential of the liquid phase.

  • Page 17: Sorption Isotherms

    Isotherm Generator called the AquaLab Vapor Sorption An- alyzer (VSA) or you can also have Decagon run the isotherm for a fee. For example, if you were using the AquaLab to monitor the water content of dried potato flakes, you would measure the water activity and water content of potato flakes dried to varying degrees using the...
  • Page 18 AquaLab 3 WATER ACTIVITY THEORY data to construct an isotherm and infer the water content using the measured water activity of samples and that isotherm. Decagon has an upgrade available to Series 4TE users that would allow you to determine moisture content and water activity simultaneously. This instrument is called the Series 4TE DUO.

  • Page 19: Getting Started

    This location should be well away from air conditioner and heater vents, open windows, etc. Place the AquaLab in a location where cleanliness can be maintained to prevent contamination of the sample chamber.

  • Page 20: Preparing Aqualab For Operation

    4 GETTING STARTED Preparing AquaLab for Operation After finding a good location for your AquaLab, plug the power cord into the back of the unit. The ON/OFF switch is located on the lower left corner of the AquaLab back panel. When the AquaLab is turned on, you should see a model name/number screen and then the main Measurement screen.

  • Page 21: Menus

    Measurement Tab The Measurement tab, as seen above, is the main screen which dis- plays each time you turn on your AquaLab. If this screen does not appear, refer to Chapter 12 for troubleshooting instructions. As mentioned earlier, the water activity and sample temperature are displayed on the screen.

  • Page 22: Configuration Tab

    AquaLab 5 MENUS Configuration Tab When at the configuration screen, pressing the up and down arrow keys moves the cursor through the various configuration options. Press the left and right arrows to page through the options. The Enter button will allow you to change the highlighted setting.
  • Page 23 The AquaLab Series 4TE models may be set between 15 and 50 C by 0.1 C intervals. Using the up and down arrows, set the AquaLab to your desired temperature and press the save button. Temp Eq...
  • Page 24 Continuous Mode: Continuous mode reads your sample until you open the chamber lid or stop the test using the stop button. AquaLab reads the sample, displays the water activity and temperature, then begins another read cycle without further input from the user. Be- tween samples, the machine will signal you with beeps.
  • Page 25 final test. If auto save is turned on, all test readings will be saved to the instruments memory, but only the final reading will appear on the main measurement screen. If AquaLab is connected to a computer using AquaLink 4 (See Chapter 11. Computer Interface), all readings taken during a custom mode test will be downloaded to the AquaLink 4 software.
  • Page 26 (To exit without updating, press the cancel button). Date AquaLab Series 4 models now have an internal calendar and clock. The time and date are recorded with each water activity reading. Pressing Enter when the Date option is highlighted allows you to set the date in the instrument.

  • Page 27: Admin Settings

    5 MENUS AquaLab Time Pressing Enter with the Time option highlighted allows you to set the current local time. Press the up or down arrows to change any of the individual values. Press the left or right buttons to change between hour and minutes.
  • Page 28 AquaLab 5 MENUS The admin. settings allow the administrator to grant or block access to some or all of the configuration options in all Series 4 models. For example: If the administrator wanted to make sure that all samples were read at 25 C the administrator would set their temperature to 25 C and then lock all other users out of that configuration screen.
  • Page 29 By selecting Auto Save “On,” the instrument will automatically store every water activity reading in the internal memory. AquaLab Series 4 can store up to 8,000 records before the memory is full. If you turn Auto Save “off” then the in-...
  • Page 30 AquaLab 5 MENUS save the reading without a name. If the save icon is not pressed after a reading, and the reading is autosaved, it is not possible to give an annotation later. Beeps Allows you to set the reading finished notification from 4 beeps to continuous beeps.
  • Page 31 5 MENUS AquaLab For the capacitance sensor (TEV Models only) Diagnostics provides you alid, base, and sample temperatures, relative humidity, as well as the capacitive sensor calibration. About This screen provides important information including the serial num- ber and code version of your instrument.

  • Page 32: Data Tab

    AquaLab 5 MENUS Data Tab View This selection will allow you to view your stored measurements. The up/down arrows will move you through the stored data with the most recent measurements at the top of the table. You may also press the left and right arrows to page quickly through the data.
  • Page 33 5 MENUS AquaLab The information shown is the water activity of the sample, the tem- perature, the test time, the user who ran the test (if setup), the date of the reading, the sensor used (4TEV only), the time the reading was taken, and the sequence number of the stored reading.

  • Page 34: Cleaning And Maintenance

    AquaLab 6 CLEANING AND MAINTENANCE Cleaning and Maintenance Keeping your AquaLab clean is vital to maintaining the accuracy of your instrument. Dust and sampling debris can contaminate the sampling chamber, so you must regularly clean your instrument. To clean your instrument, carefully follow these instructions and refer to the labeled diagram in Figure 2.

  • Page 35: Cleaning The Block Sensors

    Cleaning the Block Sensors Accessing the Sample Chamber Turn the power off on your AquaLab. If latched, move the lever over to the open position. Lift the chamber cover to expose the sam- ple chamber and sensors. The sample chamber consists of all surfaces...

  • Page 36: Cleaning A Series 4Tev

    6 CLEANING AND MAINTENANCE Cleaning a Series 4TEV If cleaning an AquaLab Series 4TEV, follow the cleaning procedures listed below being careful not to get cleaning solution on the capaci- tance sensor filter (see illustration on previous page). If you run out of Decagon Cleaning Solution, you can use isopropyl alcohol (IPA) instead.
  • Page 37 6 CLEANING AND MAINTENANCE AquaLab the Kimwipe if it becomes too dirty during this process. (d) Clean lower block with a fresh Kimwipe. Be sure to clean the entire block surface. (e) RINSE — Repeat steps b through d using new Kimwipes with distilled water.

  • Page 38: Verification Of Calibration

    Verification of Calibration After you have cleaned the chamber and other parts of your AquaLab, it is important to check the instrument performance in order to cor- rect for any linear offset that may have occurred during the cleaning process.

  • Page 39: Verification And Calibration

    7 VERIFICATION AND CALIBRATION AquaLab Verification and Calibration It is important to verify AquaLab water activity calibration against known standards to guarantee optimal performance and accuracy. Decagon recommends verification daily, once per shift or before each use. Decagon also recommends annual factory calibration to main- tain optimal performance.

  • Page 40: Verification Of Calibration

    To use a verification standard, remove the twist top and pour the contents into an AquaLab sample cup. Information about the stan- dard value and molality can be found printed on the outside of the plastic vial. If for some reason you cannot obtain Decagon’s ver- ification standards and need to make a saturated salt solution for...
  • Page 41 Follow steps 1 through 8 to verify for linear offset of your AquaLab. (Refer to Figure 3: the Verification Standard Flowchart for a quick overview.) 1.
  • Page 42 AquaLab 7 VERIFICATION AND CALIBRATION second verification standard should be within 0.003 a . 7. If either of the verification standards is not correct, it is prob- ably due to contamination of the sensor chamber. For cleaning instructions, see Chapter 6. After cleaning, repeat verification from step two.
  • Page 43 7 VERIFICATION AND CALIBRATION AquaLab Adjust for Linear Offset 1. Once you are certain a linear offset has occurred, toggle to the Configuration tab by pressing the Menu icon button. Calibra- tion is the first option highlighted in the Configuration tab.
  • Page 44 6.00 NaCl (0.76 a ). Do not adjust for the offset using steam distilled water. Ensure the rim and outside of the cup are clean. Place the sample cup in the AquaLab sample chamber. Note: You may use the same verification standard to verify and adjust the linear offset.
  • Page 45 If you still have incorrect verification standard readings after cleaning the chamber and adjusting for linear offset, contact Decagon by e-mail at support@aqualab.com or by phone at 509-332-5601 for further instructions. If you purchased your Decagon instrument from one of our international distributors, please contact them for local service and support.
  • Page 46 AquaLab 7 VERIFICATION AND CALIBRATION 3. To restore the factory calibration values, select the Check icon. To cancel and return to the main menu, choose the Cancel but- ton. After pressing the Check icon, the Calibration screen will verify that you have restored the factory calibration.

  • Page 47: Sample Preparation

    (like deep-fried, breaded foods) can be measured, but may take longer to equilibrate. For samples like these, AquaLab may take more than five minutes to give an accurate reading, or may require multiple readings of the same sample.

  • Page 48: Samples Needing Special Preparation

    Samples Needing Special Preparation AquaLab reads most materials in five minutes or less. However, the nature of some samples necessitates longer reading times. These materials need additional preparation to ensure quick, accurate read- ings.

  • Page 49: Slow Water-Emitting Samples

    The most effective way to test these types of samples is to run them in the AquaLab using the continuous or custom mode and wait for the water activity read- ings to stabilize.

  • Page 50: Low Water Activity

    Low Water Activity When a sample water activity value is below the cooling capacity of the Series 4, your AquaLab will display an error message indicating the lowest reading it attained on that particular sample. See the troubleshooting problem number five in Chapter 12 for possible so- lutions.
  • Page 51 8 SAMPLE PREPARATION AquaLab lizes. When the temperature stabilizes within an optimal one or two degrees of the chamber temperature, you can proceed with normal measurements. High-water activity samples that are warmer than the chamber tem- perature can cause condensation inside the measuring chamber, which will adversely affect subsequent readings.

  • Page 52: Taking A Reading

    How AquaLab Takes Readings The AquaLab reading cycle continues until the rate of change of three consecutive readings are less than 0.0005 a of each other.
  • Page 53 AquaLab and, if enabled, you will hear a series of beeps. Cautions Never leave a sample in your AquaLab after a reading has been taken. The sample may spill and contaminate the instrument chamber if the instrument is acciden- tally moved or jolted.
  • Page 54 50 C. If a sample has a water activity lower than about 0.03, AquaLab will display the < symbol in the Measurement window to notify you that your sample is too dry to be accurately measured by the AquaLab.

  • Page 55: Duo Operation (Optional)

    10 DUO OPERATION (OPTIONAL) AquaLab DUO Operation (Optional) Previously, measuring moisture content and water activity required different instruments. Now it is possible to determine both moisture content and water activity with one machine. The Series 4TE can be upgraded to Series 4TE DUO which can display moisture content simultaneously with water activity.

  • Page 56: Obtaining Product Isotherm Models

    AquaLab 10 DUO OPERATION (OPTIONAL) 10.1 Obtaining Product Isotherm Models Since the isotherm relationship for each product is unique, each prod- uct isotherm model must be determined experimentally. This only needs to be done once, but must be done prior to testing moisture content with the DUO.

  • Page 57: Measuring Moisture Content

    10 DUO OPERATION (OPTIONAL) AquaLab (including moisture content) from the instrument, present the data in table form, filter the data, and print reports. (See Figure 2.) 10.3 Measuring Moisture Content With the product models loaded into the instrument, the Series 4TE DUO can generate moisture content and water activity simultane- ously.
  • Page 58 AquaLab 10 DUO OPERATION (OPTIONAL) 4. Select the model for the product to be analyzed. Selecting None will not select any model. Taking a Reading 1. Readings are taken with the DUO the same as outlined in Chapter 9. First, return to the main screen.

  • Page 59: Moisture Content Adjustment

    10.4 Moisture Content Adjustment AquaLab DUO moisture analyzers calculate moisture content values based on water activity readings by utilizing models stored within the instrument. Because moisture content results vary between reference methods, it is important to ensure that the model in the instrument correlates well with your reference method moisture contents (i.e.

  • Page 60: How To Adjust For Linear Offset Or Create A New Model Based Off An Old Model

    Therefore, if moisture contents calculated with the AquaLab DUO instrument are not agreeing with your reference method, the problem can likely be addressed by ad- justing a linear offset.
  • Page 61 10 DUO OPERATION (OPTIONAL) AquaLab 4. Select Edit to edit and replace an existing model. Select New if you would like to create a new offset model with this cali- bration instead of replacing the existing model. Pressing Enter opens a model screen listing all models currently loaded on the instrument.
  • Page 62 If your moisture content readings are still inconsistent, contact Decagon by e-mail at support@aqualab.com or by phone at 509-332-5601 for further instructions. If you purchased your AquaLab Instrument from one of our international distributors, please contact them for...

  • Page 63: Restore Moisture Content Settings

    To restore the original model settings, do the following: 1. Navigate to the calibration screen in the Configuration menu of the AquaLab DUO Moisture Analyzer and select %Moisture from the list of calibration types. Note: If you do not see %Moisture as an option you may not have a DUO model or you may not have any models installed.
  • Page 64 AquaLab 10 DUO OPERATION (OPTIONAL) 4. Scroll down to Defaults and press the Enter icon button to restore to defaults. To cancel and return to the Main menu, select the Cancel icon. After selecting the Enter button, the system will prompt you to reset the defaults.

  • Page 65: How To Delete Models

    1. Navigate to the calibration screen in the Configuration menu of the AquaLab Moisture Analyzer and select %Moisture from the list of calibration types. Note: If you do not see %Moisture as an option you may not have a DUO model or you may not have any models installed.
  • Page 66 AquaLab 10 DUO OPERATION (OPTIONAL) 4. Upon pressing Enter, the following screen should appear indi- cating the model to be deleted. Press the Check icon to delete the model or press the Cancel icon to cancel the deletion.

  • Page 67: Computer Interface

    Computer Interface Your AquaLab may connect to your computer using USB or RS232. Your AquaLab was shipped to you with a standard USB cable. Using this cable, you can send water activity data to a computer for further analysis and storage. The interface is run through the AquaLink 4 Software or a terminal communication program.

  • Page 68: Aqualink 4 Part 11 Compatible Software

    Hyperterminal which came standard with Microsoft Windows prior to Windows 7. To use any of these terminal programs with your AquaLab, follow the instructions for the program with the following settings. Be sure to power on the AquaLab prior to connecting the USB interface cable...
  • Page 69 1 stop bit Flow control set to none After successfully connecting the AquaLab to your computer and upon completion of a water activity reading, the data will be dis- played in the terminal program in the format as follows: measure- ment time (minutes), sample temperature, and water activity.

  • Page 70: Troubleshooting

    AquaLab 12 TROUBLESHOOTING Troubleshooting AquaLab is a high performance, low maintenance instrument, de- signed to have few problems if used with care. Unfortunately, some- times even the best operators using the best instruments encounter technical difficulties. Below is quick reference guide that will di- rect you to detailed solutions of some problems that may occur.
  • Page 71 12 TROUBLESHOOTING AquaLab 1.PROBLEM: AquaLab will not turn on. SOLUTIONS: 1. Check to make sure your power cord is securely attached to the back of the instrument and it is plugged into the power outlet. 2. A power surge may have caused a fuse to blow. To change the fuses, follow instructions a through d.
  • Page 72 AquaLab 12 TROUBLESHOOTING be made. (Refer to Chapter 8, Samples Not at Room Temper- ature.) 3. Some products absorb or desorb moisture very slowly, causing measurements to take longer than usual, and nothing can be done to speed up the process. Refer to Chapter 8 for further explanation.
  • Page 73 12 TROUBLESHOOTING AquaLab SOLUTION: Your sample temperature is too high for the instrument to equili- brate with it in a reasonable amount of time. The instrument and sample need to be in temperature equilibrium before accurate mea- surements can be made. Therefore, very cold samples will take a very long time to measure for the same reason.
  • Page 74 AquaLab 12 TROUBLESHOOTING SOLUTIONS: 1. The sample is too dry for the instrument to read accurately. If your sample has a water activity that is less than below the detection limits of the instrument, this message will come up. Essentially, it means that there is not enough sample moisture to condense on the mirror and provide a reading.
  • Page 75 12 TROUBLESHOOTING AquaLab SOLUTION: The crystal that runs the firmware is having trouble starting. Oc- casionally, cycling the power will solve the problem. If this mes- sage continues to appear, the instrument will need to be serviced by Decagon. See Chapter 13 for detailed instructions.
  • Page 76 AquaLab 12 TROUBLESHOOTING SOLUTION: The mirror used for dew point measurements requires cleaning. Fol- low the instructions outlined in Chapter 6: Cleaning and Mainte- nance before trying to run your sample again. If this message con- tinues to appear, contact Decagon for further options.
  • Page 77 Message on Moisture Analyzer screen prompts you to activate your demo by contacting your distributor. SOLUTION: In order to begin your trial period for your AquaLab Series 4 in- strument, you will need to contact Decagon Devices for instructions on how to activate your demo.
  • Page 78 3. If the correct model is not available, load the appropriate model using AquaLink 4 Software. The AquaLab DUO can hold a total of 100 models at any one time. You may need to re- move a model using the Software or use the delete option in the %Moisture Calibration menu before you can add a new one.
  • Page 79 12 TROUBLESHOOTING AquaLab 15. DUO PROBLEM: Moisture content does not show up on the screen. SOLUTION: Moisture content has not been activated. 1. Toggle to menu tab, select moisture content, and select the appropriate model. (a) If no models appear in moisture content screen, models will need to be reloaded using AquaLink 4 software.
  • Page 80 If, after cleaning your instrument and reading the other troubleshoot- ing hints, you have reason to believe that one of the components of your AquaLab may be causing measurement error, you may access a screen that will display values for component performance. Cus- tomers can access this Diagnostics screen by navigating to the Con- figuration tab and then by scrolling down to the diagnostics option.

  • Page 81: Support And Repair

    If this is not possible, use a box that has at least four inches of space between your instrument and each wall of the box. 2. Place the AquaLab in a plastic bag to avoid disfiguring marks from the packaging. 3. Do not ship the power cord or serial cable.

  • Page 82: Repair Costs

    Loaner Service Decagon has loaner instruments to keep you measuring water ac- tivity while your instrument is being serviced. If your AquaLab is still under calibration warranty or you have a service plan with your instrument, there is no charge for the loaner service.

  • Page 83: Further Reading

    14 FURTHER READING AquaLab Further Reading 14.1 Water Activity Theory & Measurement Bousquet-Ricard, M., G. Qualyle, T. Pharm, and J. C. Cheftel. 1980. Comparative study of three methods of determining water activity in intermediate moisture foods. Lebensm Wiss Technol 13:169-173.
  • Page 84 AquaLab 14 FURTHER READING different methods. Journal of Food Science 41:910-917. Marcolli, C., and Th . Peter. 2005. Water activity in polyol/water systems: new UNIFAC parameterization. Atmospheric Chemistry and Physics 5:1545-1555. Ninni, L., M.S. Camargo, and A.J.A. Meirelles. 2000. Water ac- tivity in polyol systems.
  • Page 85 14 FURTHER READING AquaLab Wiss Technol 24:208-213. Rodel, W. 2001. Water activity and its measurement in food. P. 453-483. In E. Kress-Rogers, and C.B. Brimelow (ed.) Instrumenta- tion and sensors for the food industry. CRC Press LLC, Boca Raton, Roos, K.D. 1975. Estimation of water activity in intermediate mois- ture foods.
  • Page 86 J. Agric. Food Chem. 22:326- 327. Voysey, P. 1993. An evaluation of the AquaLab CX-2 system for measuring water activity. F. M. B. R. A. Digest No. 124 24-25. Food Safety and Microbiology Bei, Z.H., and R.-M.J.
  • Page 87 14 FURTHER READING AquaLab Cereal Foods World 26:345-349. Brandt, L. 1996. Bound for success. Controlling water activity gives technologists the edge in developing safe, shelf-stable foods. Food Formulating 2:41-48. Chirife, J., and M.P. Buera. 1994. Water activity, glass transi- tion and microbial stability in concentrated/semimoist food systems.
  • Page 88 AquaLab 14 FURTHER READING in surface agar culture. Appl Environ Microbiol 63:1048-1053. Hardman, T.M. 1988. Water and food quality. Elseiver Press, Lon- don. Hocking, A.D., and B.F. Miscamble. 1995. Water relations of some Zygomycetes isolated from food. Mycological Research 99:1113-1118.
  • Page 89 14 FURTHER READING AquaLab Marauska, M., A. Vigants, A. Klincare, D. Upite, E. Kaminska, and M. Bekers. 1996. Influence of water activity and medium osmolality on the growth and acid production of Lactobacillus casei var. alac- tosus. Proceedings of the Latvian Academy of Sciences Section B Natural Exact and Applied Sciences 50:144-146.
  • Page 90 AquaLab 14 FURTHER READING Nelson, K.A., and T.P. Labuza. 1994. Water activity and food poly- mer science: Implications of state on arrhenius and WLF models in predicting shelf life. Journal of Food Engineering 22:271-289. Nesci, A., M. Rodrigues, and M. Etcheverry. 2003. Control of Aspergillus growth and aflatoxin production using antioxidants at...
  • Page 91 14 FURTHER READING AquaLab activity and pH on the growth of Bacillus cells and spore: A response surface methodology study. International Journal of Food Microbi- ology 19:207-216. Rockland, L.B., and G.F. Stewart. 1981. Water activity: Influ- ences on food quality. Academic Press, New York.
  • Page 92 AquaLab 14 FURTHER READING Tapia de Daza, M.S., Y. Villegas, and A. Martinez. 1991. Mini- mal water activity for growth of Listeria monocytogenes as affected by solute and temperature. International Journal of Food Microbi- ology 14:333-337. Tokuoka, K., and T. Ishitani. 1991. Minimum water activities for the growth of yeasts isolated from high-sugar foods.
  • Page 93 14 FURTHER READING AquaLab coli O157:H7 in broth and processed salami as influenced by pH, wa- ter activity, and temperature and suitability of media for its recovery. Appl Environ Microbiol 62:2735-2740. Duffy, L.L., P.B. Vanderlinde, and F.H. Grau. 1994. Growth of Listeria monocytogenes on vacuum-packed cooked meats: Effects of...
  • Page 94 AquaLab 14 FURTHER READING determing water activity. Ciencia y Tecnologia Alimentaria 3(4):229- 235. Rocha-Garza, A.E., and J.F. Zayas. 1996. Quality of broiled beef patties supplemented with wheat germ protein flour. Journal of Food Science 61:418-421 Sabadini, E., M.D. Hubinger, P.-J.d.Sobral, and B.C. Carvalho, Jr.
  • Page 95 14 FURTHER READING AquaLab Duffy, L.L., P.B.Vanderlinde, and F.H. Grau. 1994. Growth of Lis- teria monocytogenes on vacuum-packed cooked meats: Effects of pH, a , nitrite and ascorbate. International Journal of Food Microbiol- ogy 23:377-390. Gmez, R., and J. Fernandez-Salguero. 1993. Note: Water activity of Spanish intermediate moisture fish products.
  • Page 96 AquaLab 14 FURTHER READING probiotic bacteria. Australian Journal of Dairy Technology 55(3):127- 131. Shimasaki, T., K. Miake, Y. Tsukamasa, M.A. Sugiyama, Y. Minegishi, and H. Shinano. 1994. Effect of water activity and storage tempera- ture on the quality and microflora of smoked salmon. Nippon Suisan Gakkaishi 60:569-576.
  • Page 97 14 FURTHER READING AquaLab Gogus, F., C. Cuzdemir, and S. Eren. 2000. Effects of some hydro- colloids and water activity on nonenzymic browning of concentrated orange juice. Nahrung 44(6):438-442. Hubinger, M., F.C. Menegalli, R.J. Aguerre, and C. Suarez. 1992. Water vapor adsorption isotherms of guava, mango and pineapple.
  • Page 98 AquaLab 14 FURTHER READING Marin, S., V. Sanchis, I. Vinas, R. Canela, and N. Magan. 1995. Effect of water activity and temperature on growth and fumonisin B-1 and B-2 production by Fusarium proliferatum and F. monili- forme on maize grain. Lett Appl Microbiol 21:298-301.
  • Page 99 14 FURTHER READING AquaLab quick breads. Journal of Food Protection 57:882-886. Cahagnier, B., L. Lesage, and D. Richard-Molard. 1993. Mould growth and conidiation in cereal grains as affected by water activity and temperature. Lett Appl Microbiol 17:7-13. Clawson, A.R., and A.J.Taylor. 1993. Chemical changes during cooking of wheat.
  • Page 100 AquaLab 14 FURTHER READING canos de Mutricion. 50(2):183-186. Phoungchandang, S., and J.L. Woods. 2000. Moisture diffusion and desorption isotherms for banana. Journal of Food Science 65:651-657. Ramanathan, S., and S. Cenkowski. 1995. Sorption isotherms of flour and flow behaviour of dough as influenced by flour compaction.
  • Page 101 14 FURTHER READING AquaLab Analysis to the determination of shelf life of roasted and ground cof- fee. Lebensm Wiss Technol 34:273-278. Carson, K.J., J.L. Collins, and M.P. Penfield. 1994. Unrefined, dried apple pomace as a potential food ingredient. Journal of Food Science 59:1213-1215.
  • Page 102 AquaLab 14 FURTHER READING dition of sodium citrate on the pasteurizing conditions in “Tuyu,” Japanese noodle soup. Journal of the Japanese Society for Food Sci- ence and Technology 43:740-747. Perera, C.O. 2005. Selected quality attributes of dried foods. Drying Technology 23:717-730.
  • Page 103 14 FURTHER READING AquaLab tice. Marcel Dekker. Hageman, M.J. 1988. The Role of Moisture in Protein Stability. Drug Dev. Ind. Pharm. 14:2047-2070. Heidemann, D.R., and P.J. Jarosz. 1991. Preformulation Studies Involving Moisture Uptake in Solid Dosage Forms. Pharmaceutical Research 8:292-297.
  • Page 104 AquaLab 14 FURTHER READING Bhandari, B., and I. Bareyre, 2003. Estimarion of crystalline phase present in glucose crystal-solution mixture by water activity mea- surement. Lebensm Wiss Technol 36:729-733(5). Brake, N.C., and O.R. Fennema. 1993. Edible coatings to inhibit lipid migration in a confectionery product. Journal of Food Science 58:1422-1425.

  • Page 105: Appendix A

    Greenspan’s standard error for each salt solution, not the AquaLab accuracy in measuring the salt. AquaLab measures all samples with an accuracy of 0.003 a .
  • Page 106 AquaLab 15 APPENDIX A Table 4: Water Activity of Selected Salt Solutions Saturated Solution a at 20 C a at 25 C Lithium Chloride 0.113 0.003 0.113 0.003 Magnesium Chloride 0.331 0.002 0.328 0.002 Potassium Carbonate 0.432 0.003 0.432 0.004 Magnesium Nitrate 0.544...

  • Page 107: Appendix B

    0.760 0.500 0.250 30.0 1.000 0.984 0.920 0.760 0.504 0.255 35.0 1.000 0.984 0.920 0.760 0.508 0.261 40.0 1.000 0.984 0.921 0.760 0.512 0.266 50.0 1.000 0.984 0.894 0.740 0.517 0.275 Note: AquaLab will measure these verification standards to 0.003...

  • Page 108: Appendix C

    Avoid solution handling and mixing errors. Save technician time. The AquaLab should be verified against a known salt standard daily. For high use or batch processing, the instrument should be checked regularly against a known salt standard of similar water activity.
  • Page 109 Practices (GLP), a saturated salt solution must read within reasonable analytical error of the accepted published value for a given temperature. Why AquaLab Verification Standards are Superior Our research indicates that unsaturated salt solutions make much better standards than saturated salts. Robinson and Stokes (1965) give activity coefficient for various salt solutions.
  • Page 110 Instructions for Using Decagon’s Verification Standards Simply empty one vial of standard solution into a sample dish and place the dish immediately into the AquaLab for measurement. Each vial will fill a sample dish to just less than half full. Table 6 shows the expected values.
  • Page 111 13.4 mol/kg LiCl 0.250 0.003 Verify the AquaLab is functioning properly with any two of these solutions. We recommended that you choose a standard from the range in which you are measuring and distilled water (or another solution from the table).
  • Page 112 AquaLab 17 APPENDIX C Chem. 81A:89-96. Lang, A.R.G. 1967. Osmotic coefficients and water potentials of sodium chloride solutions from 0 to 40 C. Aust. J. Chem. 20:2017- 2023. Robinson, R.A. and R.H. Stokes. 1965. Electrolyte Solutions. But- terworths, London.

  • Page 113: Declaration Of Conformity

    4TEV, and Series 4DUO Year of First Manufacture: 2008 This is to certify that the AquaLab water activity meter, manufac- tured by Decagon Devices, Inc., a corporation based in Pullman, Washington, USA meets or exceeds the standards for CE compli- ance as per the Council Directives noted above.

  • Page 114: Certificate Of Traceability

    Pullman WA 99163 USA Tel: 509-332-5601 Fax: 509-332-5158 support@Aqualab.com This NIST seal certifies that Decagon Inc. manufactures all AquaLab water activity meters according to temperature standards with cal- ibration traceable to the National Institute of Standards and Tech- nology (NIST).
  • Page 115 Administrator Password, 23 Email, 1, 40, 57, 76, 109 Annual Calibration Service, 30, Equilibrate, 43, 45 33, 34, 76 Equilibrium, 5, 10 AquaLab and Water Activity, 4 Error Message, 45 AquaLab Models, 4 Auto Save, 24 Fuse, 66 Barrier, 43...
  • Page 116 AquaLab INDEX Osmotic, 11 Verification, 33 Verification Standards, 33, 34 Part 11 Compliance, 63 View, 27 Performance, 34 Volatile Samples, 44 Perishability, 8 Voltage, 25 Pharmaceuticals, 8, 13 Phone, 34, 40 Warranty, 2, 77 Photo Detector, 5 Water Activity, 4, 8...

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