Water Activity News 99 by Decagon Devices

1999

Product News from Decagon

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RY AND DEHYDRATED

products have a high level of popularity with today’s consumers. Dry mixes are economical and convenient with increased shelflife, reduced packaging, decreased cost (via weight and/or volume reduction) and improved handling properties. Controlling water activity in a dry product maintains proper product structure, texture, stability, density, and rehydration properties.

■ Is your boss hounding you about quality in your dry or dehydrated product? Water activity measurement may help you put on the dog.

Drying or dehydration method.

Physical and structural changes occur during a dehydration process. Drying techniques include freezedrying, spray drying, solar drying, drum drying, vacuum drying, and osmotic dehydration. Shrinkage of cells, loss of rehydration ability, wettability, migration of solids, case hardening, and loss of volatile aroma components are important factors (Bruin et al., 1980). Freeze drying typically results in products with minimal shrinkage and superior rehydration properties. Hot air drying results in a dense product with a hard outer crust and CONTINUED on page 6

QUA AB MODEL IS RIGHT

I need temperature control? What is the low water activity block option? These questions are routinely asked prior to purchasing an AquaLab. Here we will describe the differences between the AquaLab models and applications where each model is appropriate. We currently offer the following ■ You can’t slip options: up with Series 3 - Our most popular AquaLab. Put the sample cup in model, more than adequate for the drawer and most water activity needs. close it. It’s that Series 3T - Equipped for use with an simple. external water bath (user supplied) for temperature control. Series 3TE - User-selectable internal temperature control. Low water activity option - For measuring samples that have a very low water activity (below 0.1aw).

AquaLab Series 3

AquaLab is the world’s leading research-grade, production-floor ready ■ Time for your annual water activity meter. It water activity check up? measures a sample’s water Ask about our Annual Calibration & activity by determining the Validation relative humidity of the air above plan. the sample in a closed chamber. At temperature equilibrium, relative humidity is a direct measurement of water activity, so after measuring a sample, the instrument does some quick calculations to read out directly in water activity units. Patented sensor technology and internal chilledCONTINUED on page 4

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■ More on

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■ No monkeying around. You get a wealth of information at your fingertips. All the newsletters, lots of application notes, the theory of water activity, and who else owns Aqualab. Take a look! Your on-line Water Activity resource. www.decagon.com/ aqualab/

HICH

Inside

a w & dry and dehydrated products.

■ Choosing your AquaLab—continued. ■ Specsmanship of water activity meters. ■ Pharmaceutical applications for water activity. ■ Listeria monocytogene bacteria implicated. ■ AquaLab in Europe.

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Just because it sounds reasonable—is it true?

taken pride in our attention to science as it relates to water activity and the measurement of water activity. We continuously fund intensive research and development projects, incorporating the very latest improvements in technology. Key personnel hold doctorate degrees in related fields of science. We believe all these efforts are ■ Poultry farms monitor water activity in chicken litter to reduce Salmonella critical to Decagon contamination. being able to support AVIAN DISEASES 36:664-671, 1992 and ibid. 39:39-44, 1995 and serve you, our customers. ECAGON HAS ALWAYS

Smear campaign designed to undermine AquaLab credibility.

Recently there have been reports published questioning the specifications (range and accuracy) we claim on the chilled-mirror dewpoint method-used in our instruments. These promotional reports, though they claim to be technical in nature, demonstrate a lack of understanding of the fundamentals of water activity and dewpoint measurement. Whether or not the writers of these reports understand the science, you can verify in a number of ways that the dewpoint method is capable of highly accurate readings (±0.003aw) and it can measure over the whole water activity range from 0.03 to 1.000. We have, in fact, built an instrument accurate to ±0.0003aw. Therefore; our accuracy claims for AquaLab are well within the limits of the technology we implement. Trustworthiness, expertise, and leadership.

Every instrument Decagon builds is checked to make sure it meets or exceeds these specifications. If you have questions about any of our claims, or if you would like to see our AquaLab in action, contact us. We will be happy to demonstrate the superior performance offered by AquaLab. ■

New Aqualab introduced to the Pharmaceutical Industry

HE JAVITS

CENTER IN NEW YORK was the site for the 1999 Interphex meeting. Interphex has been the world’s leading forum for pharmaceutical manufacturing for the past 20 years. Because of the synergy between the pharmaceutical and the food industry, both food scientists and members of the pharmacy industry who use Aqualab were in attendance. Currently, water activity has been submitted to the US Pharmacopeial forum as a new method for a USP physical test. The majority of the groundbreaking work, and its submission as a new method, has been done using Aqualab. The initial proposed use of water activity would be in controlling microbial growth in over-thecounter drug products. ■

Awarded to

Decagon Devices Inc.

AquaLab Series 3 For Outstanding Innovations in Product or Systems Technology 1999

■ 1999 AE50 Award—AquaLab Series 3 is one of the winners of the 12th annual AE50 recognition program. This program honors companies offering the best products engineered for agricultural, food, biological and related systems available on the market for the first time in 1998. The awards program is sponsored by Resource magazine; published by the American Society of Agricultural Engineers (ASAE).

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Pharmaceutical Applications for Water Activity

UR CUSTOMERS MAY BE INTERESTED to know about emerging applications for water activity measurement. Water activity and its use in food safety and product quality is well established in the food industry. Though the need for water activity measurements in the pharmaceutical and cosmetic industries has been recognized by some, its widespread use has not materialized - until now. Increasingly, the concept of water activity in the production of safe, stable and quality drugs is becoming more recognized ■ Your small company can be a big within the pharmaceutical wheel with AquaLab helping on industry. production water activity. Listen to

your inner tube.

Interest in this field is highlighted by several recent publications listed below. In addition, the application of water activity measurement to the microbiological attributes testing of ingredients and drug products has been submitted to the United States Pharmacopeia (USP) as a proposal for a new USP physical test. In the absence of chemical preservatives, water activity alone may determine the ability of a drug product to resist microbial contamination. Knowledge of water activity is essential to obtain a dosage form with optimal chemical, physical, microbial, and shelf-life properties. ■ A list of references pertaining to water activity and pharmaceuticals and a Pharmaceutical Application Note are available from Decagon. This application note written by Dr. Anthony Fontana, Applications Engineer, appeared on Pharmaceutical Online in April. Also, the article, “Water Activity: Its Role in a Comprehensive Microbiological Quality Assurance Plan” by Robert Friedel was published in May.

References ■ Enigl, D.C. and K.M. Sorrels. (1997). Water Activity and SelfPreserving Formulas. In: Preservative-Free and Self-Preserving Cosmetics and Drugs: Principles and Practice. Kabara, J.J. and D.S. Orth (ed.) Marcel Dekker, pp. 45-73. ■ Friedel, R.R. (1999). The application of water activity ( aw) measurement to the microbiological attributes testing of raw materials used in the manufacture of non-sterile pharmaceutical products. Pharmacopeial Forum. (accepted) ■ Friedel, R.R. and A.M. Cundell. (1998). The application of water activity measurement to the microbiological attributes testing of nonsterile over-the-counter drug products. Pharmacopeial Forum. 24(2):6087-6090. ■ Heidemann, D.R. and P.J. Jarosz. (1991). Performulation studies involving moisture uptake in solid dosage forms. Pharmaceutical Research. 8(3):292-297. ■ Pader, M. (1987). The Humectant. In: Oral Hygiene Products and Practice. Marcel Dekker, pp. 266279. ■ Pader, M. (1991). Glycerine in Oral Care Products. In: Glycerine: A Key Cosmetic Ingredient. Jungermann, E. and N.O.V. Sonntag (ed.) Marcel Dekker, pp. 381-395.

Berry Good! ■ Thank you for your timely response in this (repair) matter. I must say you definitely are one of the top companies I have dealt with in customer/technical service. Keep up the great work! Cathy Laube Kerry Ingredients Quality Assurance Manager

Low-water activity option: Special AquaLabs read samples in the very low water activity range, down to 0.030 a w . Call us.

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Choosing your AquaLab

■ AquaLab has several water activity measurement solutions so you don’t spend all your time firefighting.

Continued from page one mirror dewpoint system make AquaLab accurate and fast: ±0.003 on samples from 0.100 to 1.000aw, in five minutes or less. AquaLab Series 3T - External temperature control.

The Series 3T temperature-controlled AquaLab model has fixtures for connecting it to an external userprovided water bath. It also features a tray that keeps two additional samples at the same temperature as the measurement chamber. You need to find a bath with good temperature ■ You don’t sell fish, yet control and a pump your product smells to circulate the fishy? Time to check water activity levels water. The least with AquaLab. expensive baths only raise the water temperature. If you need cooling capability, the circulating bath unit will be more expensive. Decagon doesn’t sell water baths. They are easily procured. We don’t want to pass unnecessary handling charges on to you.

AquaLab Series 3TE - Internal temperature control.

AquaLab Series 3TE is a temperature-controlled water activity meter that allows you to have a temperaturestable sampling environment without the need of an external water bath. The “TE” stands for thermoelectric (Peltier) control. The TE allows you to choose (onscreen) at which temperature from 15 to 40°C you want to measure. You set the desired temperature using push buttons and AquaLab does the rest. The temperature is then monitored and controlled with internal thermoelectric components. Precise temperature control, to ±0.2°C, is managed with the push of a button. No additional equipment or messy connections are required; saving your budget the cost of a good water bath. This self-contained instrument will save valuable lab bench space. Low water activity option.

If you measure samples that fall below a water activity of 0.1, you may be interested in Decagon’s low water activity option. This low-water activity option has been specially optimized to read samples in the

very low water activity range, down to 0.030aw. If you need to measure samples that have a very low water activity, ask for a Series 3L at the time of purchase, or you can add the “L” option to any other AquaLab Series 3 model. The need for temperature control.

There are several advantages in having a temperaturecontrolled model, but AquaLab does not require temperature control, both sample and sensor temperatures are continuously monitored and aw is computed using both measurements. Several reasons for sample temperature control are: 1) Research purposes. To study the effects of temperature on the aw of a sample, comparison of the aw of different samples independent of temperature, accelerated shelf-life studies or other water activity studies where temperature control is critical. There are many shelf-life, packaging, and isotherm studies in which the added feature of temperature control would be very beneficial. 2) To comply with government or internal regulations for specific products. Though the aw of most products varies by less than ±0.002 per °C, some regulations require measurement at a specific temperature. The most common specification is 25°C, though 20°C is sometimes indicated. ■ Coast-to-coast and 3) To minimize extreme ambient temperature fluctuations. If the laboratory and AquaLab temperatures fluctuate by as much as ±5°C daily, water activity readings may vary by ±0.01aw. Often, this much uncertainty in sample aw is unacceptable, so there is a need for temperature control.

across the sea, AquaLab is the world’s most accurate water activity technology.

Thus, if your application meets one of the three above

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AquaLab in Europe.

■ Get to the ROOT of your shelf-life problems by using AquaLab water activity meter. More than 80% ot the Top 100 Food Companies use AquaLab. That’s a BUNCH !

requirements, you should use a temperature-controlled model.

Scott Campbell Decagon

quaLab has helped

hundreds of European food and pharmaceutical companies improve

The importance of temperature in a w measurements.

product quality and safety. One such company is Nestle, which has offices and

Water activity is temperature dependent. Temperature changes water activity due to changes in water binding, dissociation of water, solubility of solutes in water or the state of the matrix. Although, solubility of solutes can be a controlling factor, control is usually from the state of the matrix. Since the state of the matrix (glassy vs. rubbery state) is dependent on temperature, one should not be surprised that temperature affects the water activity of the food. The effect of temperature on the water activity of a food is product specific. Some products increase water activity with temperature, others decrease aw with increasing temperature, while high moisture foods have negligible change with temperature. One can therefore not predict even the direction of the change of water activity with temperature since it depends on how temperature affects the factors that control the water activity in the food.

main laboratories in Switzerland. Nestle controls companies as diverse as Perrier Water and Chamdourcy Chilled Desserts, and has manufacturing plants around the world. Nestle mainly uses AquaLab for three tasks: production quality assurance, research, and investigation of returned products. Main laboratories in Vevey, Switzerland and York, UK utilize a number of AquaLabs with water baths for new product research, and to obtain QA information that will be distributed to other Nestle factories. When items are returned from customers, Nestle uses AquaLab to find out if the product’s water activity caused a problem. If necessary, they can make changes to the mix, storage, or packaging to assure that the aw stays within acceptable levels. On production sites, AquaLab is a valuable tool that can tell QA managers in under 5 minutes whether the water activity of individual product runs is acceptable. AquaLab’s dependability, speed of result, ease of use, and accuracy over a wide range make it Nestle’s choice for water activity

■ Why buy a frog when you can have

instrumentation.

the prince of the industry … AquaLab. The importance of Another European industry leader that relies on AquaLab is temperature control is significant for laboratory the Boots Co. Plc based in Nottingham, England. Boots is one of comparisons, accelerated shelf-life studies and the largest pharmaceuticals manufacturers in the UK. Boots and packaging requirements. Also, temperature may be its subsidiaries make everything from tooth paste and indigestion essential when measuring aw levels near critical values - especially government regulations or critical control tablets to baby food products. They also supply a wide range points. The precision you require in your water activity of cosmetic and hygiene products. applications will determine your need for temperature control. ■ AquaLab is mainly used in Boots’ research and development ■ Have you been rewarded recently for quality improvements? If not, maybe it’s time to monitor water activity with AquaLab.

laboratories, where testing for mold growth in toothpaste, cosmetics and sunscreen takes place. They also use AquaLab to address moisture and packaging concerns for such products as baby milk powder, pastels and pills. Boots chose AquaLab as their standard water activity meter after testing it at their laboratories. They found AquaLab to be the easiest to use, and the most reliable for accurate and repeatable results. Because they measure a wide range of products, they found AquaLab’s ability to move from one range to another without any special changes or calibration especially helpful. ■

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& Dry and Dehydrated Products. w

■ It’s midnight, you’re missing a glass slipper and your Fairy Godmother’s negotiating with the FDA? AquaLab has improved the texture, flavor, safety, and fragrance of products all over the world. No magic, just science.

Continued from page one. slower water adsorption properties. Functionality and final use determines the appropriate drying or dehydration method and conditions. Water activity affects the textural properties of dry cereal-based foods and starch-based snack products.

Crackers, potato chips, puffed corn curls, and popcorn each lose their sensory crispness with increasing water activity. The crispness intensity and overall hedonic texture of dry snack food products are a function of aw (Katz and Labuza, 1981). Critical water activities are found where the product becomes unacceptable from a sensory standpoint. These fall ■ AquaLab is into the aw range where transportable amorphous to ask about our crystalline ruggedized carrying transformations cases. occur in simple sugar food systems and mobilization of soluble food constituents begins. Excessive and rapid drying or moisture reabsorption by a glassy material can cause the undesirable consequence of product loss by cracking and excessive breakage. To preserve the initial quality as much as possible during dehydration and storage, the chemical and biochemical reactivity and stability must be considered. Water activity influences nonenzymatic browning, lipid oxidation, degradation of vitamins, enzymatic reactions, and protein denaturation. The likelihood of nonenzymatic browning increases with increasing aw, reaching a maximum at an aw range of 0.6 to 0.7. Generally, further decreases in water activity will hinder browning reactions. Lipid oxidation has a minimum in the intermediate aw range and increases at both high and low aw values; although due to different mechanisms. This type of degradation results in the formation of highly objectionable flavors and odors, and the loss of fat soluble vitamins. Water soluble vitamin degradation in food systems increases with increasing aw values (Kirk, 1981). Enzyme and protein stability is influenced significantly by water activity due to their relatively fragile nature. Most enzymes and proteins must maintain conformation to remain active. Therefore, maintaining critical aw levels to prevent or entice conformational changes is important to food quality. Most enzymatic reactions are slowed down at

water activities below 0.8, but some reactions occur even at very low aw values.

nowledge of the water activity of powders as a function of moisture content and temperature is essential for the control of water content during processing, handling, packaging and storage to prevent the deleterious phenomenon of caking, clumping, collapse, and stickiness. Caking is a deleterious phenomenon by which a low-moisture, freeflowing powder is transformed into lumps and eventually into an agglomerated solid, resulting in loss of functionality and lowered quality (Tsourouflis et al., 1976; Saltmarch and Labuza, 1980). This problem is ubiquitous in the food and pharmaceutical industries. Caking is water activity, time, and temperature dependent, and is related to the collapse phenomena of the powder under gravitational force (Chuy and Labuza, 1994). Stages in caking involve bridging, agglomeration, compaction, and liquefaction. Factors known to affect caking kinetics may be divided into those related to the powder itself (particle size distribution, hygroscopicity and charge of particles, state of the material, presence of impurities) and external factors such as temperature, relative ■ When it comes to speed and accuracy; AquaLab can’t be BEET ! humidity, and mechanical stress applied to the substance (Aguilera and del Valle, 1995; Peleg and Mannheim, 1977).

o maintain the proper flow properties of powders and prevent caking of powders, the following methods are available: (a) drying to low moisture content, (b) treatment of the powders at low humidity atmospheres and packaging in high barrier packages, (c) storage at low temperatures, (d) in-package desiccation, (e) agglomeration, and (f) addition of anticaking agents. Anticaking agents are food ingredients added to hygroscopic powders to improve their flowability and inhibit caking. Main food-

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grade anticaking agents are silicon dioxide, silicates and sterates, phosphates, and polysaccharides (Peleg and Hollenbach, 1984). An important class of anticaking agents are ones which can compete ■ Tired of the same parade of with the host powder for QC problems year after year? Get on the stick and check out the available humidity AquaLab water activity meter. due to their large water adsorptive capacity, thus reducing their hygroscopicity and the tendency to cake. Many of these ingredients are of porous nature and exert their protective action in foods first by preferentially adsorbing large amounts of water vapor onto specific sites with high binding energy; thus depressing aw dramatically for relatively large moisture contents (Labuza, 1984; Aguilera and Del Valle, 1995). When all binding sites are occupied pores start to fill and aw corresponds to that of capillary water. Water activity is an important factor affecting the stability of dry and dehydrated products during storage. Controlling water activity in a dry or dehydrated product maintains proper product structure, texture, stability, density, and rehydration properties. ■

References ■ Aguilera, J.M. and J.M. del Valle. (1995). Structural changes in low moisture food powders. In: Food preservation by moisture control: Fundamentals and Applications - ISOPOW Practicum II. BarbosaCanovas, G.V. and J. Welti-Chanes (ed.) Technomic Publishing Company, Lancaster, Pennsylvania. pp. 675-695. ■ Bruin, S. and K.Ch.A.M. Luyben. (1980). Drying of food materials: A review of recent development. In: Advances in Drying: Volume 1. Mujumdar, A.S. (ed.) Hemisphere Publishing Corporation, Washington. pp. 155-215. ■ Chuy, L.E. and T.P. Labuza. (1994). Caking and stickiness of dairy-based food powders as related to glass transition. Journal of Food Science. 59(1):43-46. ■ Katz, E.E. and T.P. Labuza. (1981). Effect of water activity on the sensory crispness and mechanical deformation of snack food products. Journal of Food Science. 46:403-409. ■ Kirk, J.R. (1981). Influence of water activity on stability of vitamins in dehydrated foods. In: Water Activity: Influences on Food Quality. Rockland, L.B. and G.F. Stewart (ed.) Academic Press, New York. pp. 631- ■ Labuza, T.P. (1984). Moisture Sorption: Practical Aspects of Isotherm Measurement and Use. American Association of Cereal Chemists, St. Paul, MN. ■ Peleg, M. and A.M. Hollenbach. (1984). Flow conditioners and anticaking agents. Food Technology. 38(3):93-102. ■ Peleg, M. and C.H. Mannheim. (1977). The mechanism of caking of powdered onion. Journal of Food Processing and Preservation. 1:3-11. ■ Saltmarch, M. and T.P. Labuza. (1980). Influence of relative humidity on the physicochemical state of lactose in spray-dried sweet whey powders. Journal of Food Science. 45:1231-1236,1242. ■ Tsourouflis, S., J.M. Flink, and M. Karel. (1976). Loss of structure in freeze-dried carbohydrate solutions: effect of temperature, moisture content and composition. Journal of the Science of Food and Agriculture. 27:509-519. DON’T FORGET. Food Quality ‘99 Conference and Expo Monday, September 13, 1999 San Francisco Product Demonstrations 4:30-5:30 PM Marriot Willow Room Understanding Water Activity by Anthony J. Fontana, Ph.D. Decagon Devices, Inc. The water activity of a food describes the degree to which water is “bound” in the food and hence its availability to act as a solvent and participate in chemical/biological reactions as growth of microorganisms. It is an important property used to predict stability and safety of food with respect to microbial growth, rate of deterioration reactions and chemical/physical properties. The water activity principle has been incorporated into FDA’s laws and new HACCP regulations, the purpose of which is to set requirements that assure products are produced under sanitary conditions and are pure, wholesome and safe. In the past, measuring water activity was a frustrating experience. New instrument technologies, such as AquaLab, have vastly improved the speed, accuracy and reliability of water activity measurements. ■

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DECAGON 950 NE Nelson Court Pullman, Washington 99163

509-332-2756 fax: 509-332-5158 aqualab@decagon.com

Listeria monocytogene bacteria implicated.

OTENTIALLY DEADLY Listeria monocytogene bacteria have forced the recall of more than 45 million pounds of hot dogs, luncheon meats, and other ready-to-eat products, such as cheese spread and milk, since last December. The bacteria have also been implicated in at least 97 illnesses and 20 deaths-14 adults and six miscarriages or stillbirths as of March 1, 1999. Listeria testing isn’t mandatory in ready-to-eat products, and federal inspectors sample for the pathogen only on a random basis. But consumers can help protect themselves with a few simple strategies: ■ When a recall is announced, check your refrigerator and return any contaminated food to the seller. ■ Cook hot dogs to a minimum of 160 degrees F.

Even if you are in far off places you can visit our website: www.decagon.com/aqualab/ USDA’s Food Safety and Inspection Service (FSIS) announces new resources and

■ Make sure you keep hot foods hot (above 140 degrees) and cold foods cold (at or below 40 degrees); never leave them out at room temperature for longer than two hours.

information about Listeria monocytogenes on USDA’s website.

■ The elderly, those with compromised immune systems and pregnant women should avoid luncheon meat entirely, unless they heat it until it is steaming hot.

News releases (May 25, l999)

For more information see the FDA website at www.fda.gov, or call the USDA’s Meat and Poultry Hotline at 800-535-4555.

Listeriosis and Food Safety

—KATHRYN WINIARSKI in Westchester/Rockland County, NY, Journal News, June 1999 Water Activity & Listeria Notes

ecause Listeria monocytogenes is a common environmental contaminant, the critical issues are controlling their growth and preventing their survival. These bacteria can grow slowly at refrigerated temperatures. Subjection to low water activities at low temperature (4°C) enhanced the bacteriostatic effect.

FSIS Consumer information:

Tips FSIS Action Plan for Addressing

Listeria

monocytogenes :

Backgrounder

Listeria Guidelines for Industry, May l999 Federal Register:

monocytogenes

Listeria

contamination

of ready-to-eat products; compliance with HACCP

Listeria monocytogenes have a lower a w limit for growth of approximately 0.90 at 30°C when glycerol is used to control a w. Limits of 0.92 and 0.93 have been reported using NaCl and sucrose, respectively. In a meat system (without added solutes) a limit for growth of 0.93 at 20°C was determined. These limits are similar to those for other Gram-positive bacteria (ICMSF, 1996). —Anthony J. Fontana Jr., PhD., Decagon

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system regulations and

Dear Customer, The President of the United States is talking about food safety! Water activity is one of the key factors affecting food safety so we must be in the right business. Seriously, we watch current issues in water activity closely. This newsletter is our way of sharing what we have learned over the past year. I hope you enjoy the 1999 newsletter. Sincerely,

comment request, May 26, l999.

Visit the USDA website under What’s New. www.fsis.usda.gov

Tamsin Campbell AquaLab Product Manager

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