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Moisture plays a key role in the quality of pet food products. For each product, thereβs 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 innovativeβand commercially successfulβpet 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 several 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:
It accurately predicts safety: Water activity predicts whether microbes will grow on or in a product.
It also predicts quality: Water activity is correlated with many reactions (lipid oxidation, vitamin degradation, texture changes) that end shelf life.
Itβs repeatable: Water activity is a test anyone can run to precise scientific standards. Measure water activityto Β±0.003.
Itβs standards-based: Unlike other moisture measurements, water activity has a scale with a known zero, and measurements can be verified with known NIST-traceable standards. Results can be compared between departments, factories, or companies no matter where theyβre located or who makes the measurement.
Range of aw | Microorganisms Generally Inhibited by lowest aw in this Range | Pet Foods Generally Within this Range |
1.00β0.95 | Pseudomonas, Escherichia, Proteus, Shigells, Klebsiella, Bacillus, Clostridium perfringens, some yeasts | PedigreeβLittle Champions Meow MixβTender Favorites PedigreeβLittle Champions PurinaβBeneful Prepared Meals |
0.95β0.91 | Salmonella, Vibrio parahaemalyticus, C. Botulinum, Serratia, Lactobacillus, Pediococcus, some molds, yeasts (Rhodotorula, Pichia) | Canine Carry Outsβbeef |
0.91β0.87 | Many yeasts (Candida, Tarulopsis, Hansenula), Micrococcus | PurinaβMoist & Meaty Dog Food |
0.87β0.80 | Most molds (mycotaxigenic penicilla), Staphyloccocus aureus, most Saccharomyces (bailiii) spp., Debaryomyces | CesarβSofties Canine Carry Outsβbacon |
0.80β0.75 | Most halaphilic bacteria, mycotoxigenic aspergilli | PurinaβBeggin Strips |
0.75β0.65 | Xerophilic molds (Aspergillus chevalieri, A. candidus, Wallemia sebi), Saccharomyces bisporus | Milk BoneβTrail Mix |
0.65β0.40 | Osmophilic yeasts (Saccharomyces rouxii), few molds (Aspergilius echinulatus, Monascus bisporus) | Iam's ProActive HealthβMiniChunks Natural Life Grain-Freeβadult dog WiskasβTemptations |
0.60β0.50 | No microbial proliferation | Iam's ProActive HealthβOriginal Cat PurinaβAlpo Variety Snaps |
Measure at the line with the scientific accuracy of an R&D or QA/QC lab
Ensure that packaging will maintain product safety and quality over shelf life
Predict impacts of storing or shipping under abuse conditions
Set accurate sell by/use by dates
Determine storage requirements
Test incoming ingredients for safety and quality
Ensure that the ingredients to be mixed have compatible moisture (aw) levels
Prevent multi-component moisture migration
Do accelerated shelf-life testing
Set a spec for the product to avoid safety and quality issues such as mold, microbial growth, texture problems, off smells or flavors
Eliminate variability with a standards-based moisture metric
Use water activity to guide innovative formulations
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 β even on volatile samples that cripple other instruments.
Make detailed moisture maps to predict, understand, and control moistureβs effects. High-resolution moisture sorption isotherms for shelf life prediction.