Water Activity News 2006 by Decagon Devices

www.aqualab.com

WaterActivityNews 2006

Is the AquaLab Still the Fastest and Most Accurate?

ecagon’s advertising slogan for its AquaLab water activity meters states that they are the fastest, most accurate, guaranteed. This slogan is based on Decagon’s claims that for most products, water activity tests can be done in less than five minutes, with an accuracy of ±0.003aw, and a precision (repeatability) of ±0.001aw using an AquaLab chilled mirror dewpoint instrument. It has been suggested that Decagon cannot achieve the results they claim; instead the less-than-five-minute test is accomplished by some type of predictor

AQUALAB SAFETY

Redefining Potentially Hazardous Foods

he term potentially hazardous food (PHF) was developed by the U.S. Public Health Service during the last half of the twentieth century to regulate perishable food. In 1962, PHF was defined as a perishable food that supports the rapid and progressive growth of infectious or toxigenic microorganisms. Exemptions for foods with an aw ≤ 0.85 or pH ≤ 4.6 were added in 1976. Thus, foods were considered non-PHF when their aw ≤ 0.85, which is below the water activity for Staphylococcus aureus growth and toxin production or the pH ≤ 4.6, which is below the pH for proteolytic Clostridium botulinum growth and toxin production. Potentially hazardous food means a food that has no or inadequate hurdles to pathogenic bacterial growth and requires temperature control for safety (TCS) to limit pathogenic microorganism growth or toxin formation in the food. continued on page 6 AQUALAB PRECISION

mode and that the reported accuracy actually refers to the precision of the instrument. What is the real story? This article clearly details the validity of Decagon’s claims. AQUALAB

Water Activity QUALITY Measurement Theory First, an understanding of how to determine water activity is needed to understand why the AquaLab is fast and accurate. Water activity is continued on page 2

See AquaLab, AquaLab Lite, & Pawkit in action at our 2006 Tradeshows! Visit us at the following tradeshows and conferences in 2006: IFT Annual Meeting and Food Expo Orlando, Florida June 24–28, 2006 National Environmental Health Association San Antonio, Texas June 25–28, 2006 International Association of Food Protection Calgary, Albert, Canada August 13–16, 2006 American Association of Cereal Chemists San Francisco, California September 17–20, 2006

Contents Is the AquaLab Still the Fastest and Most Accurate? Pg 1 Redefining Potentially Hazardous Foods Pg 1 Dear Anthony, Pg 4 Teaching Students Principles of Water Activity Pg 7 How Decagon Tailors Training Seminars for Their Customers Pg 8 Moisture Sorption Isotherms Pg 10 Water Activity Seminar Schedule Pg 11

American Association of Pharmaceutical Scientists San Antonio, Texas October 29 – November 2, 2006

Decagon Devices Sponsors AACC Symposium Pg 12

Eastern Analytical Symposium Somerset, New Jersy November 13–16, 2006

Newly Redesigned Pawkit Pg 12

DECAGON DEVICES

“The AquaLab v3 is highly innovative yet extremely user friendly. It allows for accurate results in a timely manner. Decagon’s superb customer service is readily available and eager to assist their every customer’s needs.” —Priscilla Rangel, Laboratory Manager, Quanta Lab

AquaLab— Still Fastest and Most Accurate? continued from cover

Why is the AquaLab Accurate It has been suggested that since AquaLab uses these two temperatures to determine water activity and each can only be measured with an accuracy in the range of ±0.10 to ±0.15 °C, the best water activity accuracy that can be achieved is ±0.015 based on reference to a psychometric chart. It is critical to remember that AquaLab uses saturated vapor pressures to calculate water activity, not a psychometric chart. Since dividing saturated vapor pressures allows subtracting the sample temperature from the dewpoint temperature, the critical measurement is the Table 1. The differences between final a w and initial a w for 4 saturated difference between two salts solutions and water when tested continuously for 90 minutes. Measuring Water temperature means— Final aw - Initial aw Water Activity Saturated Activity rather then (90 minutes) (25°C) Solution An electric hygrometer measurement of the 0.0009 0.1130 LiCl uses a relative humidity temperatures sensor to indirectly themselves. AquaLab -0.0002 0.4315 K 2 CO 3 determine the relative measures this -0.0005 0.7529 NaCl humidity (vapor temperature difference -0.0006 0.8434 KCl pressure) of the with an accuracy of headspace. This is an 0.01 or better. Hence, -0.0005 1.0000 Water indirect measurement Decagon is able to -0.0002 Average because humidity achieve the accuracy a. Test time for each water activity test never exceeded 5 minutes and sensors require a they claim because the tests were run until the cumulative test time exceeded 90 minutes. calibration that relates AquaLab measures changes in electrical water activity by properties to relative humidity values of known determining the difference between two standards. Decagon’s LITE and Pawkit, and all temperature means. competitor instruments, are electric hygrometers. AquaLab directly measures water activity by Why is the AquaLab Fast recording the dewpoint temperature of the air in It also has been claimed that AquaLab cannot the headspace and the temperature of the sample complete a water activity test in less than 5 once vapor equilibrium has occurred. The minutes because the equilibration process takes dewpoint temperature is used to calculate the a minimum of 20–30 minutes for all samples. In saturated vapor pressure at the dewpoint reality, vapor equilibration occurs very quickly temperature. By definition, the saturated vapor as evidenced by theoretical modeling and by pressure at the dewpoint temperature is equal observation using NMR techniques. So, it is to the vapor pressure at ambient temperature. thermal equilibration that requires the longest The sample temperature is used to calculate the time. When using an electric hygrometer that saturated vapor pressure at the same does not use the sample temperature as part of temperature. Water activity is then determined the calculation, it is necessary for the sample by dividing the saturated vapor pressure at the More spark to be in complete thermal equilibration with dewpoint temperature by the saturated vapor for your product the humidity sensor to obtain accurate protection. pressure at the sample temperature. results. This process can take up to 20 defined as the partial vapor pressure of water in equilibrium with a sample divided by the vapor pressure of pure water at the same temperature. It is often written as aw = p/po. All water activity instruments operate under the same theory. A sample is placed in a closed chamber and the water in the sample is allowed to equilibrate with the water vapor in the headspace. The rate limiting steps of the process are the time it takes for vapor and temperature equilibrium to occur. Once equilibrium is obtained, some method is used to measure the humidity or vapor pressure in the headspace above the sample.

minutes or longer. However, if the sample . temperature is used as part of the calculation, it is not necessary for the sample to be in complete thermal equilibration with the sensor, only Table 2. Precision and accuracy of water activity measurements of 4 saturated that it be close so that the sample is not salt solutions and water across 19 observations. undergoing drastic temperature changes Saturated Water Activity during the test. Consequently, since vapor Precision Accuracy Solution (25°C) equilibration happens very quickly and LiCl 0.1130 AquaLab measures the sample temperature, 0.0004 0.0004 tests can be completed in less than 5 minutes K 2 CO 3 0.4315 0.0004 0.0010 for most products. It is possible that some NaCl 0.7529 0.0003 0.0009 samples may require longer equilibration times, such as those with coatings, high fat, KCl 0.8434 0.0007 0.0008 high viscosity, glassy texture, or multiple Water 1.0000 0.0005 0.0005 components.

Working together.

Average

How Fast is the AquaLab Now that the theory of AquaLab has been explained, it is time to test the theory. First, can equilibration be achieved in less than 5 minutes? Four saturated salts and water were evaluated continuously in the AquaLab Series 3TE over a time period of 90 minutes. This was accomplished using the continuous mode setting on the AquaLab Series 3TE, which runs a test to completion, logs the data, then immediately begins the next test. The time per individual test never exceeded 5 minutes for any solution. The largest difference between the initial aw and the final aw for any solution was 0.0009, which is less than the reported precision of the instrument. Since there is essentially no change in water activity from the first <5 minute test to the final test after 90 minutes, it can be concluded that for the solutions tested, and most sample types, vapor equilibration can be achieved in less than 5 minutes. Accurate and Precise The difficulty in reporting an accuracy and precision value for a water activity instrument is that accuracy and precision will depend on the sample being analyzed. Standard procedure to determine the accuracy of water activity instrumentation is to compare its readings to literature values for saturated salts. Since the accuracy can vary with each solution, an average accuracy across the range of possible water activity values may be reported. Another difficulty lies in how to DECAGON calculate accuracy. Precision is simply

0.0005

0.0006

calculated as the standard deviation across multiple observations. However, there is no standard calculation for determining accuracy. For this work, accuracy was determined as the square root of the sum of square differences between measured values and literature values across all observations divided by the degrees of freedom. Four saturated salts and water representing a range of water activities were evaluated for water activity across 19 replicated observations per solution in an AquaLab Series 3TE. Table 2 indicates that AquaLab’s accuracy and precision values were very good for all 5 solutions and were better than Decagon’s reported accuracy (±0.003) and precision (±0.001) values. The average accuracy across all solutions was ±0.0006 while the average precision was ±0.0005. While the accuracy of other types of samples may not be as good as for these solutions since the samples themselves are not completely uniform, the results of this study indicate that the accuracy and precision of the AquaLab when reading saturated salt solutions and water are actually better than the values listed in the specifications and certainly better than the ±0.015 that has been suggested by others. Fastest, Most Accurate, Guaranteed Decagon Devices claims their AquaLab water activity instruments are the fastest, most accurate, guaranteed. The information presented here indicates that both in theory and in practice, they are.

DEVICES 3

DECAGON DEVICES

Dear Anthony, What is the status of Are there other uses for water activity USP Method <1112> for besides controlling microorganisms? pharmaceutical products? Yes! Water activity also influences the rate of The Microbiology Committee at chemical reactions, physical properties such as USP has approved USP Method texture, moisture migration and shelf life. Similar to <1112> Microbiological microbial control, the reaction rate of many chemical Attributes of Nonsterile reactions, that impact stability are dependent on Pharmaceutical Products – water Application of Water activity. Activity Determination. Water “Thank you for such a The method will be may speedy repair on our published in the USP-NF influence Second Supplement in August 2006. chemical Pawkit meter. We Control of the water activity in a reactivity appreciate everything pharmaceutical product can be used to by inhibit microbial growth. Reduced water acting you do for us.” activity will greatly assist in the as a —Erin Cillessen prevention of microbial contamination of solvent, Dynamic Foods pharmaceutical products, and the reactant, formulation, manufacturing, and testing or by of nonsterile dosage forms should reflect changing this parameter. When formulating drug products, the the mobility of the reactants by affecting the water activity should be evaluated so that the viscosity of the product. Water activity influences product may be self-preserving. To lower water non-enzymatic browning, lipid oxidation, activity of a food, one can remove water, add degradation of vitamins, enzymatic reactions, protein ingredients, or lower the temperature. Adding denaturation, starch gelatinization, and starch ingredients such as salt, sugars, glycols, glycerin or retrogradation. amino acids will result in a formulation with a lower Since water activity describes the thermodynamic water activity that discourages the proliferation of energy status of the water within a system, there is a microorganisms in the product. close relationship between water activity and the The new method can be used to establish a physical stability and shelf life. Foods with high aw microbial limits testing strategy for typical have a texture that is described as moist, juicy, tender pharmaceutical and over-the-counter drug products based on water activity. Pharmaceutical drug products with water activities well below 0.75, i.e. “Your company is the best, direct compression tablets, liquid-filled capsules, nonaqueous liquid products, ointments, and others very efficient and courteous would be excellent candidates for reduced microbial limit testing. This is especially true when to work with.” pharmaceutical products are made from ingredients —Carol Brown, Sensus America of good microbial quality, in manufacturing environments that do not foster microbial contamination, by processes that inherently reduce the microbial content, and in manufacturing sites and chewy. When the water activity of these that have an established testing history of low products is lowered, undesirable textural attributes— bioburden associated with their products. such as hard, dry, stale and tough—are used. Low aw foods normally have texture attributes described as crisp and crunchy, while at higher aw the texture 4

www.aqualab.com changes to soggy. Also, water activity affects the flow, caking and clumping properties of powders and granulations. Differences in water activity levels between components or a component and the Tune-up your risk reduction. environmental humidity are a driving force for moisture migration. Knowledge of whether water will absorb or desorb from a particular component is essential to prevent degradation, especially if one of the substances is moisture sensitive. For example, if equal amounts of component A at 2% and component B at 10% moisture content are to be blended together, will there be moisture exchange between the components? The final moisture content of the blended material would be 6%, but did any moisture exchange between component A and B? The answer depends on the water activities of the two components. If the water activities of the two components are the same, then no moisture will exchange between the two components. Likewise, two ingredients at the same moisture content may not be compatible when mixed together. If two materials of differing water activities but the same water content are mixed together, the

Product protection is more than luck.

water will adjust between the materials until an equilibrium water activity is obtained. Therefore, water activity provides more useful information for formulation design, manufacturing conditions, and packaging requirements than water content. Finally, you can use water activity to obtain rapid moisture content data through the moisture sorption isotherm curve for your product. The relationship between water activity and moisture content at a given temperature is called the moisture sorption isotherm. After you have developed the isotherm curve for your product, you can use aw to obtain the moisture content information. Thus, you will have the complete water picture for your product in less than 5 minutes. Why is Decagonâ&#x20AC;&#x2122;s Calibration Service important? Decagon knows how important accurate water activity analysis is to your company. Your AquaLab will measure water activity of your product accurately for years with verification of standards and occasional cleaning. For many customers the daily checking of water activity standards is enough to ensure the safety and quality of their product. But some companies need documentation to certify that AquaLab is working within specifications. With Decagonâ&#x20AC;&#x2122;s Calibration Service, you will receive compliance documentation for either HACCP, ISO 9000, ISO Guide 25, Good Laboratory Practices, or Good Manufacturing Practices.

[ KD2 Pro Decagon manufactures easy-to-use instrumentation for the measurement of thermal properties: thermal conductivity, thermal resistivity, specific heat (heat capacity) and thermal diffusivity.

[ Thermal properties measurement of natural and engineered materials.

www.thermal.decagon.com

continued from cover

Redefining Potentially Hazardous Foods Growth of Infectious Pathogens Why was the definition of potentially hazardous food changed in the 2005 Food Code? There were many factors that went into the FDA decision to update this definition, including the following reasons: the term “rapid and progressive growth of infectious and toxigenic microorganisms” in the old definition was not clearly defined. A 0.85aw level of safety against Staphylococcus aureus was conservatively low. A pH of 4.6 may be inappropriate as Listeria monocytogenes grows at 4.39, Salmonella spp. at 4.2 and Yersinia enterocolitica at 4.2, although a pH 4.6 is appropriate when only spore forming pathogens are present. The slow growth of low infectious dose pathogens such as Listeria monocytogenes was not considered. Finally, sufficient research has been done on food products to construct tables that predict the growth of pathogenic microorganisms when the interaction of both pH and aw are considered (See Tables A & B).

Table A. Interaction of pH and a w for control of spores in food heat-treated to destroy vegetative cells and subsequently packaged.

pH Values

Values < 4.6

> 4.6 – 5.6

> 5.6

< 0.92

Non-PHF*/non-TCS**

Non-PHF/non-TCS

> 0.92 – 0.95

Non-PHF/non-TCS

PA***

> 0.95

Non-PHF/non-TCS

* PHF means “Potentially Hazardous Food” ** TCS means “Time/Temperature Control for Safety Food” *** PA means “Product Assessment Required” Table A can be used to determine if a food which is heat-treated and packaged is PHF, Non-PHF or Requires Product Assessment. Food must meet cooking requirements of Food Code section 3-401.11 (no partial cooks) to eliminate vegetative pathogens. Spore forming pathogens are the only remaining biological hazards of concern. Food is packaged to prevent re-contamination. Therefore, higher pH & a w can be safely tolerated.

Table B. Interaction of pH and a w for control of vegetative cells and spores in food not heat-treated or heat-treated but not packaged.

pH Values

Values < 4.2

4.2 – 4.6

> 4.6 – 5.0

> 5.0

< 0.88

Non-PHF*/non-TCS**

Non-PHF/non-TCS

0.88 – 0.90

Non-PHF/non-TCS

PA***

> 0.90 – 0.92

Non-PHF/non-TCS

>0.92

Non-PHF/non-TCS

* PHF means “Potentially Hazardous Food” ** TCS means “Time/Temperature Control for Safety Food” *** PA means “Product Assessment Required” Table B can be used to determine if a food which is not heat-treated or heat-treated but not packaged is PHF, Non-PHF or Requires Product Assessment. Food not heat-treated may contain vegetative cells and pathogenic spores. Food that was heat-treated but not packaged may become re-contaminated. pH values considered in Table B must include 4.2 because Staphylococcus aureus can grow at that level.

Interaction of a w and pH The 2005 version of the Food Code updates the definitions of PHF by using a scientific based criteria that considers the interaction of aw and pH in determining if a food is designated as a non-PHF/ non-TCS food. Interaction Tables A & B consider the interaction of aw and pH under certain conditions of heat-treatment and packaging. The hurdle effect is used to control or eliminate pathogens that would otherwise be ineffective when used alone. The effect of a heat treatment which destroys vegetative cells and the effect of packaging which prevents re-contamination is considered. 6

Simplifying Food Safety In the United States, most states have adopted the Food Code definition of potentially hazardous foods. Because of the complexity in the US food systems and the confusion over the old definition of potentially hazardous foods, this new science-based definition offers a more accurate and easily defined assessment for the safety of food products. This definition relies solely on pH and aw as the parameters for making decisions about the need for time/temperature control for safety.

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Teaching Students Principles of Water Activity —the Humble Twinkie

f you want to get a child’s attention, start talking about foods they like- especially sweet, sugary foods like Twinkies. Twinkies can teach kids a lot about food science—specifically water activity.

K-12 Food Science Awareness In an effort to promote K-12 education of food science, Decagon has begun teaching teachers the importance of water activity. Similar work is being done by the Institute of Food Technologists (IFT). IFT is promoting food science awareness in an effort to increase the number of students choosing to get a degree in Food Science.

Because food is integral to life, teachers have been using Twinkies to demonstrate shelf-life for years. One teacher we spoke with hangs a new Twinkie from the ceiling of her room at the beginning of each school year and they observe it all year long to see if it will grow mold. Now that she understands water activity, she knows why there is no mold or microbial growth during the school year.

Interested in teaching students about water activity? Email to get a free water activity sample lesson or learn more about Decagon’s lab books suitable for educators grades 10 through collegiate.

DA7200 for Water Activity DA7200 utilizes NIR spectroscopy to determine the activity of the water in the sample.

New NIR approach to fast water activity measurement.

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DECAGON DEVICES 950 NE Nelson Court Pullman, Washington 99163 800-755-2751 fax 509/332-5158 aqualab@decagon.com www.aqualab.com

Your food product is only as safe as

it’s weakest link.

“We had no experience with water activity at all…” How Decagon Tailors Training Seminars for Their Customers

t the Maryland Environmental Safety Lab, they don’t measure water activity every day. They analyze a variety of samples for the Maryland Department of Health and Mental Hygiene (DHMH), local health departments, and concerned citizens, using many different lab instruments. Doing food safety tests for the food control program in the Health Department is just one of their jobs. In fact, they might only use AquaLab once a week. But they need to be confident that their water activity readings are accurate.

Tailored to Your Needs The seminar is tailored to the needs of the specific customer. According to Brady Carter, Decagon applications engineer, that can mean anything from a three hour discussion of water activity applications to a highly technical 8 hour short course. “Of course we cover the basics, but we fine-tune the program to address specific problems and issues,” he says. In the DHMH seminar, that meant focusing on understanding water activity as an indication of food safety and accurately measuring the water activity of a variety of samples.

On-site Installation and Seminar When they started measuring water activity, they didn’t know much about it. “It was a brand new test,” according to Kalpana Hegde, who does much of the analytical testing in the lab. “We had no experience with water activity at all.” Some people with extensive water activity experience might feel comfortable just pulling the instrument out of the box and getting started with measurements. DHMH opted instead for a more complete introduction through the on-site installation and seminar program.

Process Standardization Kalpana uses the seminar information every time she tests a sample. “I use very homogeneous samples at room temperature. I run verification standards to check for linearity and Plan for a use distilled water for a blank at the rainy day. beginning and end of the sample run. In between, I run one or two standards to make sure it’s running right. It gives accurate and precise data.”

Peace of Mind That means instead of an instrument in a box, DHMH got on-site setup and training, an in-house seminar tailored to their particular lab, a year’s worth of sample cups and standards, an AquaTherm temperature equilibration tray, three year’s worth of verification and calibration—and peace of mind. “It was helpful to get all the information at the same time we got the instrument,” said Kalpana. “They covered all the details about the meter—how to use verification standards, how to keep the meter clean, how to use temperature control. I use a new cup for each test, make sure each cup is clean externally and internally—I take so much care, I’ve never had a problem with keeping the meter clean. When I run my standards, it’s right on there.”

A Little Theory DHMH food chemistry also found the theoretical aspects of the seminar helpful. As Delores Willis, program manager, notes, “We just do the testing. We don't make the decision as to why the sample should be tested. We’re kind of the middle person.” Like many AquaLab purchasers, the DHMH lab staff found both the AquaLab instrument and the concept of water activity new. Everyone needs it but why? According to Brady Carter, most people involved with food safety know they need to measure water activity—frequently they’ll find it built into product specifications—but they don’t know exactly how or why. During the seminar, they'll realize all the

“I’ve never had a problem with keeping the meter clean.” applications for water activity—everything from predicting moisture migration to controlling quality factors like clumping, caking, and texture. Product Discovery “People realize, ‘Oh! We could be doing this!’,” Carter says. “One cheese manufacturer discovered that he could be predicting the water activity of a finished product based on the water activities of the ingredients he was adding. He was thrilled to think that he could tweak the recipe to hit a certain water activity without ever mixing up a batch of product.” Understanding Safety Monitoring The food lab at DHMH is not involved with quality issues. “We use AquaLab to analyze food samples— both raw and finished products—to check for shelf life. It’s routine safety monitoring,” explains Delores. Most of their samples come from the food control inspectors in the Health Department. They are asked to analyze everything from home-canned jams and jellies sold at a local farmer's market to hams smoked and sold by a fire station as a fund raiser. But Kalpana still found it helpful to understand the concepts of water activity. “It makes a big difference to understand what you're actually looking for,” she says. “It gives me confidence in the testing.” Learn More The seminar option is also available to customers who already own the instrument. If you are interested in finding out more about an in-house seminar, contact Decagon’s application engineers at 1-509-332-2756.

Get a different

perspective on water activity and food protection.

From the Sales Desk:

he sales department at Decagon is dedicated to the instruments we sell and the customers who buy them. Occasionally, we hear someone say something that gives us pause. Recently a customer said that our instrument was “delicate”. This term is not one we generally hear when discussing the AquaLab. After further investigation, we found out that this user was measuring a product that is very sticky and causes a lot of problems if the user is not cautious when presenting the sample to the instrument. They felt it was delicate because of the maintenance required to keep the block in working order. To this problem the sales department presents a simple solution; never fill the cup over half full and wipe the rim of the cup before sampling. These two quick, easy steps can save a lot of time in cleaning. A misnomer exists that suggests the more product, the faster or more accurate the reading; however, the AquaLab only requires enough sample to cover the bottom of the cup. Another customer sent in a meter that they had affectionately named the “boat anchor”. Best guess suggested that the instrument was not reading correctly, took too long to read, or was unstable. We tell all of our customers that cleaning will solve over 90% of the problems that they may have. If you are unsure how to clean it, give us a call. We can walk you through the cleaning process or we can send you a CD-ROM that contains videos on proper cleaning procedure. Your AquaLab is a highly accurate piece of scientific instrumentation that will provide years of accurate and reliable service if you care for it properly. As cautious consumers we baby our televisions, coddle our cars and do our best to protect our personal items. Your AquaLab should receive the same care and attention that you provide your other investments.

Moisture Sorption Isotherms he relationship between water activity and moisture content at a given temperature is called the moisture sorption isotherm. This relationship is complex and unique for each product due to different interactions (colligative, capillary, and surface effects) between the water and the solid components at different moisture contents. An increase in aw is almost always accompanied by an increase in the water content, but in a nonlinear fashion. Moisture sorption isotherms are sigmoidal in shape for most foods, although foods that contain large amounts of sugar or small soluble molecules have a J-type isotherm curve shape. There is a difference (called hysteresis) in the adsorption (wetting) and desorption (drying) isotherm curves.

vs. dry to a moisture content. The moisture content associated with a safe water activity on the drying curve will not be associated with the same water activity on the wetting curve due to hysteresis. If the production technician controlling drying of a product over-dries beyond the specified moisture content and decides to re-wet the product back to the moisture content specification, the results could be disastrous. The productâ&#x20AC;&#x2122;s response to moisture is no longer following the drying curve, but has switched to the wetting curve. The moisture content specification may correspond to a safe water activity on the drying curve, but on the wetting curve, the moisture content may be related to a very unsafe water activity level.

Automatic Isotherm Generator Decagon is pleased to announce the development of an automatic moisture isotherm generator. It will be available for a much lower price than currently available isotherm instruments. The user will place their sample into the isotherm chamber, set test parameters, and then walk away. In one to three days, a complete isotherm curve (both adsorption and desorption) will be generated. It will be possible to choose from several isotherm equations to characterize the isotherm graph. The isotherm coefficients will be displayed on the screen and transferable to an additional application software package. This instrument will facilitate sorption isotherm development for any company that would like to better understand the water in their product.

Predicting Moisture Content from Water Activity An additional function of the isotherm is moisture content prediction. Although water activity is a much better predictor of safety and quality than moisture content, there are times when it is necessary to know both water activity and moisture content. Moisture content measurements can be inaccurate, time-consuming, and require a precision balance. Thankfully, the sorption isotherm can be used to predict moisture content based on water activity, usually with better accuracy than actually running a moisture content analysis and in much less time. Thus, you will have the complete water picture for your product in less than 5 minutes.

Moisture Content (%)

Drying and Wetting Curves Moisture sorption isotherms provide valuable information to a company. For anyone who dries or wets their product, the sorption isotherm serves as a drying and wetting curve. It shows the water activity of a product when wetted and dried to a specific moisture content. For anyone who still relies on a moisture content specification instead of a water activity specification, the sorption isotherm will clearly illustrate the potential problems that can occur when you wet to a moisture content

Moisture Sorption Isotherm

16 14 12 10 8 6

GAB Isotherm Generator Data

4 2 0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Water Activity ( a w)

0.8

0.9

1.0

Don’t be shortsighted when protecting your products and customers.

Isotherms Aid in Product Development Isotherms are very valuable for formulation and product development. By comparing the isotherms of different formulations, it is possible to determine if a product can be adjusted to allow higher moisture content at a given water activity or a lower water activity at a given moisture content. The result can be a moister product that is still shelf stable. For those producing multi-component products, it is possible using the isotherms of the two components to determine what the final water activity will be of the mixture without actually making the product. For dried products, the isotherm will predict the moisture content of the product when it is dried to a shelf stable water activity level. Shelf-Life Prediction Finally, sorption isotherms are valuable for shelf life prediction. A product’s isotherm can be used to determine package requirements depending on the products sensitivity to moisture gain or loss. Products with a crystalline type isotherm will be less susceptible to caking than products with an amorphous type isotherm. However, the water activity of a crystalline material will increase very quickly until the saturation point is reached—as evidenced by the isotherm. Temperature can also impact shelf life; sorption isotherms conducted at different temperatures help determine the impact of temperature abuse on moisture content and water activity. Affordable Isotherms Isotherms are very valuable to anyone concerned with product quality and safety. With the release of Decagon’s affordable isotherm generator, it will be possible for many more companies to begin developing isotherms for their products. For more information about isotherms and isotherm generation, contact any of Decagon’s Application Engineers.

Water Activity Seminar Schedule for 2006 Dates and Venues Princeton, NJ October 10 (Food Seminar) October 11 (Pharmaceutical Seminar) Chicago, IL October 12 (Food Seminar) What are the water activity seminars all about? Decagon’s one-day short course on the fundamentals of water activity will help you understand how the water in your product relates to quality, shelf-life, and safety. You will learn practical uses and applications of water activity in product formulation, processing, and storage. The concepts will be illustrated with examples from the food and pharmaceutical industry. Register Now $179 for one person. $159 for two or more attendees. www.decagon.com/seminar

Time to get

together and talk about protecting your products.

DECAGON DEVICES 11

www.aqualab.com From the President’s Desk I recently read in Food Processing Magazine that the #1 concern of food processors is food safety. Decagon can help you with this concern. Our fast, accurate water activity meters give you information that you can use to assure food safety and improve product quality. We hope this newsletter illustrates how measuring water activity can benefit you! You can contact me personally by e-mailing tamsin@decagon.com to offer your comments about this newsletter or any of our products. Sincerely,

Tamsin Campbell President

Decagon Devices Sponsors AACC Symposium Water Activity: The More Important Water Analysis

his symposium will introduce the concept of moisture management and the role of water activity as a moisture management strategy. It will cover a description of water activity, why it is important for sweet and salty cereal foods, and how it differs from moisture content. The impact of water activity on product shelf life will also be discussed, specifically its use in predictive models. In addition, the importance of considering water activity during product development will be discussed. Finally, water activity measurement techniques will be discussed with a special emphasis on the new concept of measuring water activity using near infrared (NIR) spectroscopy.

Symposium Highlights Strategies for Moisture Management Shelly Schmidt, Ph.D. What is Water Activity? Anthony Fontana, Ph.D. Shelf Life Prediction using Predictive Models Cindy Stewart, Ph.D. Water Activity in Product Development Yang Kou, Ph.D.

Newly Redesigned Pawkit

Water Activity Measurement Brady Carter Water Activity by NIR Wes Shadow

uring the past year, Decagon completed a redesign of the Pawkit portable water activity meter. Easier-to-use than ever, the new Pawkit features a robust case design and user-friendly sample insertion while maintaining Decagon’s speed, accuracy, and reliability in water activity measurement. This lightweight, space-saving device is ideal for any on-the-go health inspector, QC professional, or food scientist who needs to quickly measure water activity and make decisions in the field.

DECAGON DEVICES

Decagon Devices, Inc. 950 NE Nelson Court Pullman, WA 99163 USA 1-800-755-2751 509-332-2756 Fax: 509-332-5158 aqualab@decagon.com