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Moisture plays a key role in the quality of pet food products. For each product, there’s an ideal range of water activity values that maximizes profit, nutrition, and tastiness while keeping the product safe from microbes and mold.
For example, a bag of dog food kibbles has a moisture sweet spot of 0.55-0.65. Any lower than 0.55, and the dog food is unappetizingly dry and hard. Not to mention the seller is losing money because the product has been over-processed. Any higher than 0.65, and the product will mold in the bag, becoming unacceptable.
Water activity has been used to guide the formulation of some of the most innovative–and commercially successful–pet food products. Complex pet food formulations like a simulated marrow-filled bone, a meaty cat food containing crunchy vitamin bits, and a shelf-stable, moist, meat-like product are all controlled by water activity.
Isotherms (curves showing how water activity changes as moisture increases and decreases in a specific product) are also a key formulation tool. They can be used to locate critical points where phase changes occur, to create mixing models, to investigate moisture-related issues, and in many other ways.
Using water activity as a moisture super-spec can help you solve specific moisture challenges, determine shelf life, choose packaging, monitor incoming ingredients, prevent spoilage, and maintain taste, texture, and nutrition.
For example, there are a number of products on the market with multi-textured characteristics that use water activity. These products combine a hard, dry-baked pet food and a soft, moist pet food. The hard, dry component has the advantage of teeth cleaning, but is less palatable than a soft, moist food. Careful formulation using water activity keeps the crunchy kibble crunchy and the moist bits soft. The two can share a bag and a long shelf life without the kibble getting soft and the bits losing their moist texture.
Water activity is a test anyone can run to precise scientific standards. A certification course trains new users to measure water activity. In 20 minutes, nearly anyone can learn to run a reliable, repeatable, verified water activity test.
Pet food manufacturers use water activity to monitor their products because:
Range of aw | Microorganisms Generally Inhibited by lowest aw in this Range | Pet Foods Generally Within this Range |
1.00–0.95 | Pseudomonas, Escherichia, Proteus, Shigells, Klebsiella, Bacillus, Clostridium perfringens, some yeasts | Pedigree–Little Champions Meow Mix–Tender Favorites Pedigree–Little Champions Purina–Beneful Prepared Meals |
0.95–0.91 | Salmonella, Vibrio parahaemalyticus, C. Botulinum, Serratia, Lactobacillus, Pediococcus, some molds, yeasts (Rhodotorula, Pichia) | Canine Carry Outs–beef |
0.91–0.87 | Many yeasts (Candida, Tarulopsis, Hansenula), Micrococcus | Purina–Moist & Meaty Dog Food |
0.87–0.80 | Most molds (mycotaxigenic penicilla), Staphyloccocus aureus, most Saccharomyces (bailiii) spp., Debaryomyces | Cesar–Softies Canine Carry Outs–bacon |
0.80–0.75 | Most halaphilic bacteria, mycotoxigenic aspergilli | Purina–Beggin Strips |
0.75–0.65 | Xerophilic molds (Aspergillus chevalieri, A. candidus, Wallemia sebi), Saccharomyces bisporus | Milk Bone–Trail Mix |
0.65–0.40 | Osmophilic yeasts (Saccharomyces rouxii), few molds (Aspergilius echinulatus, Monascus bisporus) | Iam's ProActive Health–MiniChunks Natural Life Grain-Free–adult dog Wiskas–Temptations |
0.60–0.50 | No microbial proliferation | Iam's ProActive Health–Original Cat Purina–Alpo Variety Snaps |
We bought bags of kibble from a variety of retailers. We tested big brands alongside small niche companies. The result? A market snapshot of thirteen pet food brands. In this quick 15-minute webinar, Scott Campbell reviews the findings.
Learn:
Lightning-fast total moisture analysis to tighten process control and boost quality. Combine moisture content and water activity in one device.
Precise aw readings in minutes — even on volatile samples that cripple other instruments.
Make detailed moisture maps to predict, understand, and control moisture’s effects. High-resolution moisture sorption isotherms for shelf life prediction.