Market Insight

Water activity: A better moisture metric for pet food

Producers of pet food, pet treats, and other baked or dried pet snacks like these can improve their product quality and their overall yield with the help of water activity measurement.

Find the ideal water activity range for your pet food product that maximizes profit, nutrition, and tastiness while keeping it safe from microbes and mold.

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.

Formulate intelligently

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.

Know the moisture super-spec

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.

Make every employee a moisture expert

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.

Moisture measurement with benefits

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.

It’s repeatable: Water activity is a test anyone can run to precise scientific standards. Measure water activityto ±0.003.

It’s 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 they’re located or who makes the measurement.

Table 1. Water activities that correlate to the growth of microorganisms in pet food. Water activity is directly related to mold and microbial growth and is an integral part of many HACCP programs. Chart adapted from L.R. Beuchat, Cereal Foods World, 26: 345 (1981).
Range of a_w	Microorganisms Generally Inhibited by lowest a_win 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

Production

Measure at the line with the scientific accuracy of an R&D or QA/QC lab

Packing/shipping

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

Incoming ingredients

Test incoming ingredients for safety and quality

Ensure that the ingredients to be mixed have compatible moisture (a_w) levels

Operations

Maximize operating efficiency by pinpointing the right spec
Reduce waste in the supply chain and manufacturing process
Ensure quality and profit by accurately measuring moisture at the right time

QA/QC

Eliminate variability with a standards-based moisture metric
Use a repeatable, reliable measurement
Run highly accurate, research-grade tests in 5 minutes or less

Research and development

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

Market snapshot: Pet food top competitors

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: