2001
Water Activity a Key Parameter in a New Shelf Stable Baked Good Standard activity level OW CERTIFICATION to ANSI/NSF below which it Standard 75 ensures that certain baked goods will not support the rapid cannot grow. and progressive growth of potentially hazardous Water activity, not water bacteria. This is accomplished by reformulation to a water activity value of 0.85 or less and/or content, determines the a pH level of 4.6 or less, or challenge testing lower limit of with inoculation of specific strains of bacteria. _Water activity available water These products can be stored at ambient is the vocabulary for microbial of quality control temperatures for a specified period of time, understood growth. The lowest a w at saving costly refrigeration space without around the globe. which the vast majority of endangering the public health and safety. food spoilage bacteria will grow Standard 75 was developed based on the is about 0.90. current FDA Food Code definition of nonStaphylococcus aureus under potentially hazardous foods. Non-potentially anaerobic conditions is inhibited at an a w of hazardous foods do not support the rapid and 0.91, but aerobically the a w level is 0.86. The progressive growth of infectious or toxigenic microorganisms. Every microorganism has a water Continued on page 6
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XXXXXXXXXXXXXXXXXXXXXXX Maximizing Return on Investment in Water Activity Measurements G. S. Campbell, Ph.D V. P. Engineering—DECAGON
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Y Food ingredients or finished product: all need water activity measurement.
HE FIRST ANNUAL Food Quality Award was presented by Food Quality Magazine last fall at its annual conference in Philadelphia. The award was presented to Franklin Foods, a Vermont company that specializes in cheese products. I attended the presentation and was impressed by the attitude of Mr. Curtt Perry, the quality assurance manager, and his company, toward food safety. Quality control is often viewed as a necessary evil. In contrast, Mr. Perry and Franklin Foods saw quality assurance as an opportunity to add value to their products. This proactive approach to Continued on page 7
INSIDE THIS ISSUE: (Shelf-life (Up-to-date Reference List (Tips for Successful Measurement (Listeria Prevention (2001 Scheduled Events
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The Effect of Water Activity on Shelf Life
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ATER ACTIVITY is an important means of predicting and controlling the shelf life of food products. Shelf life is the time during which a product will remain safe, maintain desired sensory, chemical, physical and microbiological properties, and comply with nutritional labeling. Many factors influence shelf life such as; water activity, pH, redox potential, oxygen, use of preservatives, and processing/ storage conditions. By measuring and controlling the water activity of foodstuffs, it is possible to; a) predict which microorganisms will be potential sources of spoilage and infection, b) maintain the chemical stability of foods, c) minimize nonenzymatic browning reactions and spontaneous autocatalytic lipid oxidation reactions, d) control the activity of enzymes, e) prolong nutrients and vitamins in food, and f) optimize the physical properties of foods. Every microorganism has a water activity level below which it cannot grow. Controlling water activity controls microbial growth extends shelf life and allows some products to be safely stored without refrigeration. Water activity influences deteriorative chemical reaction rates because water acts as a solvent, can be a reactant itself, or can change the mobility of reactants through viscosity. One or a combination of any of these factors can lead to faster deterioration and a shortened product shelf life. Non-enzymic browning reactions increase with increasing a w to a maximum at 0.6 to 0.7 a w . Lipid oxidation has a minimum at about 0.2 to 0.3 a w. Moisture migration is a major cause of deteriorative physical changes and texture loss in food. Water activity is a function of temperature, thus shipping and storage temperature changes water activities effect on the microbial, chemical and physical properties.
It is important to determine critical water activity levels for a product and how sensitive it is to changes in water activity. Optimum chemical stability is generally found near the monolayer moisture content, as determined from moisture sorption isotherms. Changes in water activity by absorption of water when a product is exposed to a high humidity environment or loss of water when placed in a low humidity environment brings about undesirable changes in products and shortens shelf life. These changes can be physical, such as loss of crispness in dry products, caking and clumping of powders, or moist products losing water to become tough and chewy. Other undesirable changes are acceleration of chemical deterioration, or potential for microbial growth. Understanding and maintaining the critical water activity level of a product through suitable packaging will extend shelf life. Many dry powders will eventually cake if they are stored without any moisture barrier or anticaking agent. Most breakfast cereals are less susceptible to moisture gain and do not demand high barrier levels. Moisture loss can be critical for some baked goods, but if too much moisture remains in the package then microbial growth can develop. Multi-component products may require separate packaging or barriers to prevent moisture transfer if the water activity of the individual components cannot be adjusted closer together. By knowing the critical water activity limits of a product it is possible to calculate shelf life based on the relevant barrier properties of the packaging material or dictate the barrier specifications of the package to obtain a desired shelf life. /
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W ater activity in formulation, processing and storage affect the How to load a Pawkit.
quality, shelf life, and safety of our food supply.
In spite of its light weight and sophisticated electronics, Pawkit is very rugged and easy to use. To open: Grip the Pawkit on each side of the display while holding it level. Pull down on the front tab until it clicks. Don’t worry it will not break. Set the Pawkit on a flat surface open.
Place a half-full sample cup inside the bottom ring.
The lid closes forward with the touch of a finger.
To close: After the reading is done, remove the sample. Pick up Pawkit, turn it over, press the dots to snap the bottom closed. See. Easy!
Important Current Water Activity References 6Barrett, A. H., Cardello, A. V., Mair, L., Maguire, P., Lesher, L. L., Richardson, M., Briggs, J., and Taub, I. A. (2000). Textural optimization of shelf-stable bread: Effects of glycerol content and dough-forming technique. Cereal Chemistry. 77(2):169-176. 6Bell, Leonard N. and Labuza, Theodore P. (2000). Moisture Sorption Practical Aspects of Isotherm Measurement and Use. American Association of Cereal Chemists. St. Paul. 6Fontana, A. J. (2000). Understanding the importance of water activity in food. Cereal Foods World. 45(1):7-10. 6Fontana, A. J. (2001). Water activity’s role in food safety and quality. Food Safety Magazine. 7(1):19-21,57. 6Mazurkiewicz, J. and Tomasik, P. (2001). Relationships between water activity and viscosity of solutions. Food Hydrocolloids. 15(1):43-46. 6Morillon, V., Debeaufort, F., Capelle, M., Blond, G., and Voilley, A. (2000). Influence of the physical state of water on the barrier properties of hydrophilic and hydrophobic films. Journal of Agricultural and Food Chemistry. 48(1):1116. 6Rosso, L. and Robinson, T. P. (2001). A cardinal model to describe the effect of water activity on the growth of moulds. International Journal of Food Microbiology. 63(3):265-273. 6Shadbolt, C., Ross, T., and McMeekin, T. A. (2001). Differentiation of the effects of lethal pH and water activity: food safety implications. Letters In Applied Microbiology. 32(2):99-102. 6Valik, L. and Pieckova, E. (2001). Growth modelling of heat-resistant fungi: the effect of water activity. International Journal of Food Microbiology. 63(1-2):11-17. 6Wijtzes, T., Rombouts, F. M., Kant-Muermans, M. L., Van’T Riet, K., and Zwietering, M. H. (2001). Development and validation of a combined temperature, water activity, pH model for bacterial growth rate of Lactobacillus curvatus. International Journal of Food Microbiology. 63(12):57-64.
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Keys to a successful, accurate water activity reading. Machine Prep: • Warm the machine up for at least 15 minutes. • Check a verification salt closest to the value of your sample (see flow chart below). • If the salt reads correctly, then check distilled H 2O. • If the salt reads incorrectly, you need to clean the meter and maybe adjust the linear offset. (Refer to your manual for instructions.)
Sample Prep: • Sample must be homogeneous, representative of the product being tested. • Temperature of sample must be within 4°C of the meter. The closer the temp., the quicker your readings will be. • Keep sample covered when storing, heating, or cooling. • Don’t overfill sample dishes. Half full is sufficient. • Make sure all users know and folow a standard sample preparation technique. (Contact Decagon for SOP template document.)
Remember these few steps and you can be sure your readings are as accurate as possible!
Decagon’s water activity meters only use only AOAC approved methods. Decagon is a member of the AOAC International, a scientific association dedicated to analytical excellence. Clean cups and pure standards keep your AquaLab running strong.
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SING CLEAN cups and checking your AquaLab with verification standards will ensure that your readings are as accurate as possible. Here’s why: Cups Contaminated cups reduce accuracy. Even after cleaning out a cup, residue can be left in the cup, causing contamination. We strongly recommend that cups be used only once. Single use of cups will ensure that your samples have a fresh chamber to be stored in and that your sample will not be contaminated. Verification Standards AquaLab’s performance should be verified daily. Verification salts are an essential tool in testing your meter’s cleanliness and accuracy. By checking a salt, you have a quick indicator to let you know if you need to clean and possibly adjust your meter. Decagon makes this procedure hassle free by offering independently verified, prepackaged salts, in 4 different a w ranges, 0.250, 0.500, 0.760, and 0.984. Disposable sample dishes and verification salts can be purchased directly from Decagon by calling 800-755-2751. /
Calibration diagram.
Trade-in your old CX2 or CX1 and receive a credit on the purchase of a new AquaLab Series 3 or Series 3TE 4 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
It is possible to assess the risk of post-packaging L. monocytogenes growth in many food products using the 0.92 w standard.
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Listeria Prevention
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HE FDA, FSIS, USDA, AND CDC ARE working on an action plan to reduce the incidence of listerial gastroenteritis and listeriosis resulting from the contamination of the United States food supply with Listeria. They have invited public comment and Decagon has responded because water activity control can be used as part of a program to reduce the risk of sickness or death due to Listeria contamination. Reducing the risk. As presently constituted, the action plan for the reduction of the presence of Listeria in food products focuses primarily on detection of the bacteria and the creation of new handling procedures for ready-to-eat food products. While these measures will certainly help reduce the risk of a Listeria outbreak, a more complete food safety plan should include a method for evaluating whether Listeriacontaminated products can support proliferation of this bacteria, since the level of bacteria present invariably affects the severity of the illness in persons who consume contaminated products. Water activity testing can be used for this risk assessment. Microorganism multiply even at refrigeration temperatures. Although Listeria may be initially present at a low level in a contaminated food, the microorganism can multiply during storage (even at refrigeration temperatures.) If the water
activity of the contaminated food is below 0.92, no such growth occurs. Water activity in combination with other hurdles, such as pH, temperature, or modified atmosphere packaging, will limit growth even at higher than 0.92 water activity levels. Stopping Listeria growth. While it is impractical to bring the water activities of some products below this level, it is possible to assess the risk of post-packaging Listeria growth in many food products using the 0.92 a w standard. These products include: Smoked Seafood, Preserved Fish, Natural Cheese, Aged Cheese, Dry/Semi-Dry Fermented Sausages, P창te, and Meat Spreads. Because the water activities of these products are relatively close to 0.92, simple changes in processing or formulation that slightly lower the water activity can stop Listeria growth. Furthermore, continual monitoring of water activity can confirm that all product runs that leave a processing facility will be safe from Listeria growth. /
_Water activity is the secret to product improvement, long shelf-life, and better texture.
Water Activity OK
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Announcement of 2 New AquaLab Accessories
YWhat’s the buzz? New Pawkit portable water activity meter !
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AquaLink software: AQUALINK is a Windows-based program designed for collection and graphing of data from all AquaLab models. It logs water activity, temperature, time of measurement, and a time and date stamp (from your computer’s clock) as well as real-time sample identification and comments fields. Y Screen shot of AquaLink utility. AquaLink makes it easy to have a permanent record for inspectors, GMP, HACCP, or ISO documentation. It also makes writing reports simple.
Baked Goods Standard
continued from cover
minimum a w for toxin production is generally higher than the minimum a w growth level. Water activity controls microbial growth and allows the product to be safely stored without refrigeration. A recent study by NSF shows a 40% increase in product sales when merchandise is stored in high-traffic, non-refrigerated display units. Today, desserts such as soft pies and filled pastries face greater regulatory scrutiny when displayed without refrigeration. ANSI/NSF Standard 75 provides test methods and evaluation criteria (i.e. critical a w limit) to determine that a product does not require refrigeration for safe storage. /
_ TEP Specifications: Range: -10°C to 90°C. Digital Control to 1%. Control ar ambient. Energy efficient Peltier design. Small, compact size uses little bench space.
2 Thermal Equilibration Plate: ^ Pre-equilibrate samples for water activity measurement away from ambient temperature. ^ Rapidly heat or cool samples to ambient temperature for faster water activity measurements. /
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Thermal Conductivity and Thermal Diffusivity for Foods •Direct readout •Portable •Compact •Easy to use ^ Fast 2 minute readings.
KD2 for foods. Call today.
KD2 is designed for use in solids, gels, powders and now liquid samples.
DECAGON
800-755-2751 509-332-5158 kd2@decagon.com www.decagon.com/kd2
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^Every company would benefit financially from turning water activity measurement into a value added activity. Maximize Your R.O.I. continued from cover quality not only won the support of the production department, and the loyalty of customers, it added substantially to the company’s bottom line. When we visit customers to try to better understand their applications and needs, we typically find one of two attitudes. One type of customer sees water activity measurement as something that is needed to satisfy a regulatory requirement; something they would prefer not to do. The other type of customer understands the principles and applications of water activity and applies this knowledge to add value to products. This added value can be critical in securing or maintaining market share, or demanding premium prices for products. One customer indicated that their product would be physically unstable and unsuitable for market without careful attention to water activity in the design and manufacture of the product. Other customers use water activity measurements to assure the quality of incoming ingredients. The first type of customer often has little or no knowledge of what water activity is, let alone how to apply it to improve product quality. The result of the measurement is just a number to be written in a notebook or entered into a computer. The second type has taken the time to understand the concepts and _Time to trim costs and save applications, and with water looks for new activity. applications as they design products and processes. Z
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AquaLab’s NEW internal temperature control conquers even the harshest conditions. AquaLab Series 3 TE: Our most accurate water activity meter measures a w in under 5 minutes guaranteed.
X Precise temperature control, to ±0.2 °C, with the push of a button.
DECAGON
800-755-2751 fax 509/332-5158 aqualab@decagon.com www.decagon.com/aqualab
XXXXXXXXXXXXXXXXXXXXXXX It seems obvious that every company would benefit financially from turning water activity measurement into a value added activity, instead of just a way to meet regulatory requirements. We feel that it is in Decagon’s best interest to assist customers in getting the most out of their investment in water activity. We therefore employ scientists who are experts in water activity applications. These scientists publish application notes, write magazine articles, and give seminars. Our latest offering is a day-long workshop which is loaded with useful applications. We hope you are making maximum use of these resources, and that you will contact us if we can help you get more out of your water activity investment. /
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Water Activity News 2001
Dear CustomerAt Decagon, we value education. We believe that if you understand all the applications of water activity, you will receive the greatest value from owning AquaLab. In pursuit of this value we have visited many of you in the past year and presented a short in-house seminar on the application of water activity. In June 2001 we offered a full-day seminar in three different cities, teaching fundamentals of water activity in depth. If we have not visited you, give us a call at 800-755-2751 and we will let you know if we will be in your area. If we can’t get together face-to-face, visit our website www.aqualab.com where you will find helpful information and application notes. Sincerely,
Tamsin Campbell AquaLab Product Manager
Decagon Devices, Inc. publishes Water Activity News annually. No subscription or dues. ISSN# 1083-3943. Printed in USA. ©2001 DECAGON
Y Are you branching your product line out. Put AquaLab on your list to help maintain product quality.
^Pawkit Design Award
ASAE, The Society for Engineering in Agriculture, Food, and Biological Systems chose Decagon Devices as one of the year 2001 AE50 award winners. The AE50 award program is Award Winner for sponsered by Resource to emphasize Technical the role of new products and systems Innovation in bringing advanced technology to the marketplace. These engineering developments help farmers, food processors, and equipment manufacturers cut costs, enhance quality, and increase profits.
DECAGON 2001 trade shows and conferences. Northwest Food Protection Association Portland, OR January 22–24 Petfood Forum 2001 Chicago, IL March 26–27 Food Safety Summit and Expo Washington, DC April 16–18 AFDO Atlanta, GA April 16–20 Fundamentals of Water Activity One-Day Short Course Chicago, IL June 5 Fundamentals of Water Activity One-Day Short Course Mahwah, NJ June 7 Fundamentals of Water Activity One-Day Short Course New Orleans, LA June 22
DECAGON 950 NE Nelson Court Pullman, Washington 99163
800-755-2751
AE50
Institute of Food Technologists (IFT) New Orleans, LA June 24–27
Society for Engineering in Agricultural, Food, and Biological Systems (ASAE) Sacramento, CA July 29–August 1 International Association for Food Protection (formerly IAMFES) Minneapolis, MN August 5–8 FDA Regional SeminarsNorth East Region Hyde Park, NY August 15 FDA Regional SeminarsPacific Region Edmunds, WA August 22 FDA Regional SeminarsCentral Region Bloomington, MN September 12 American Association of Cereal Chemists Charlotte, NC October 14–17 American Association of Pharmaceutical Scientists Denver, CO October 21–25
fax 509/332-5158 aqualab@decagon.com www.decagon.com/aqualab
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