Without an accurate, product-specific shelf life, you could be scrapping expired product that is still good. Or selling unexpired product that is actually bad. You could be paying too much for packaging that doesn’t help your product. Or giving up significant shelf life that would come from better packaging. The point is, you don’t know for sure because you’re operating in the dark.
So why don’t people do more shelf life testing?
Learn more about monitoring shelf life from METER’s Food science experts
Full-blown shelf life testing
Typically, it’s because a true, full-blown shelf life test is a daunting task. It involves complex relationships between moisture, temperature, and product failure modes.
Any number of things could make your product unsafe or unpalatable—mold, microbial growth, rancidity, changes in texture or flavor, vitamin degradation. Most people don’t have the expertise to do full-blown shelf life testing in-house, and getting an outside lab to do it is expensive.
There is a scientifically sound alternative to this kind of shelf life testing. It’s shelf life, simplified by water activity. It generates all the data you need to predict your product’s shelf life from an experiment anyone, even a small startup, can afford to run.
Shelf life and water activity
- It eliminates distractions. When you know your product’s water activity, you will know which failure modes are an issue for that product.
- It simplifies prediction. You can use your water activity meter plus one other measurement method (which one depends on your particular failure mode) to run a straightforward, in-house experiment that will predict your shelf life accurately.
- It standardizes production. You can set a water activity specification that lets you achieve your optimal shelf life with every batch.
Your shelf life data can provide valuable insights to help you stop product failure, predict and lengthen shelf life, choose the most cost-effective packaging, and more.
How does water activity predict shelf life?
Water 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, including water activity, pH, redox potential, oxygen, use of preservatives, and processing/storage conditions. By measuring and controlling the water activity of foods and pharmaceuticals, it is possible to:
- Predict which microorganisms will be potential sources of spoilage and infection
- Maintain the chemical stability of foods
- Minimize nonenzymatic browning reactions and spontaneous autocatalytic lipid oxidation reactions
- Control the activity of enzymes
- Prolong nutrients and vitamins in food
- Optimize the physical properties of foods
Factors that end shelf life
There are three main factors that influence shelf life: microbial properties, chemical changes, and physical deterioration. All of these factors are connected to water activity.
Mold and microbial growth are the most dangerous threats to shelf life. Controlling water activity can inhibit or preclude microbial growth, extend shelf life, and allow some products to be safely stored without refrigeration. Using well-defined tables, you can set a water activity limit for your product and use this in shelf life testing.
|0.97||Clostridium botulinum E |
|fresh meat, fruits, |
vegetables, canned fruit, canned vegetables
|low-salt bacon, cooked sausages,|
nasal spray, eye drops
|0.94||Clostridium botulinum A, B|
|0.93||Bacillus cereus||Rhizopus nigricans||some cheeses, cured meat (ham)|
evaporated milk, ral liquid
suspensions, topical lotions
|0.85||Aspergillus clavatus||sweetened condensed milk, aged cheeses (cheddar), fermented sausage (salami), dried meats (jerky), bacon, most fruit juice concentrates, chocolate syrup, fruit cake, fondants, cough syrup, oral analgesic suspensions|
|0.81||Penicillium Penicillium cyclopium|
|0.78||Aspergillus flavus||jam, marmalade, marzipan, glace fruits, molasses, dried figs, heavily salted fish|
|0.62||Saccharomyces rouxii||dried fruits, corn syrup, licorice, marshmallows, chewing gums, dried pet foods|
|0.60||No microbial proliferation|
|0.50||No microbial proliferation||caramels, toffees, honey, noodles, topical ointments|
|0.40||No microbial proliferation||whole egg powder, cocoa, liquid center cough drop|
|0.30||No microbial proliferation||crackers, starch-based snack foods, cake mixes, vitamin tablets, suppositories|
|0.20||No microbial proliferation||boiled sweets, milk powder, infant formula|
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. For example, non-enzymic browning reactions increase with increasing water activity to a maximum at 0.6 to 0.7 aw, and lipid oxidation is minimized from about 0.2 to 0.3 aw. Optimum chemical stability is generally found near the monolayer moisture content, as determined from moisture sorption isotherms.
High and (less often) low humidity environments can affect a product’s water activity, causing undesirable changes in the product’s texture or physical properties and shortening shelf life. Issues include loss of crispness in dry products, caking and clumping of powders, and toughness or chewiness in moist products. Finding the critical water activity for your product can involve some research, but water activity makes it much easier to do.
Packaging, shipping, and storage
Water activity changes during shipping and storage can profoundly influence shelf life. Water activity is a function of temperature, and shipping and storage temperatures can affect water activity inside the package. Simplified shelf life testing can help you determine the best packaging and evaluate the effect of shipping and storage conditions on the shelf life of your product.