Understanding the shelf life of your product plays a critical role in protecting your brand, but the way a food’s “best by” date is determined depends highly on the attributes of your individual product. When a food manufacturer contacts me about running a shelf life study, I typically ask a series of questions to help determine which methods are the most relevant – what is the pH and water activity? How is the product processed and packaged? Is it stored ambient, refrigerated or frozen? If you don’t have answers yet, don’t sweat it! We can walk you through what we need to know.

One reason I ask these questions is to determine if it is appropriate to conduct a process authority evaluation prior to performing a shelf life study. Why is this important? Because a process authority letter contains information about how to process a product in order to achieve the appropriate safety and quality standards. If the outcome of the evaluation is a recommendation for reformulation or changes to processing methods, these can be implemented before spending precious time and money on a shelf life study for a now-obsolete formula.

What to Expect From a Process Authority Letter

A comprehensive process authority letter will describe how to process a product to ensure microbiological safety during ambient storage and may include additional recommendations for maintaining product safety or quality. When developing your process schedule, the processing authority should be aware of all hazards associated with the product. They should also consider the product type, formulation and intrinsic properties which impact the safety and stability of the product. Prescriptive processing recommendations will be provided in a process authority letter and should be incorporated into the manufacturing process.

While a process authority letter will tell you about a product’s microbiological safety and stability, it does not offer insight into the shelf life of the product.

Understanding Shelf Life in “Shelf Stable” Foods

Once the processor is meeting or exceeding recommendations of the process authority, the work required to understand product shelf life is not complete. So-called “shelf stable” products do not de facto have an unlimited shelf life – quality indicators such as color, texture, flavor, aroma, rancidity, moisture changes and so on play a key role in determining the shelf life of a product.

Imagine biting into a potato chip only to realize that it tastes rancid and stale. Immediately, you check the “best by” date, but it states that the product is “good” for another three months. To prevent this situation as a manufacturer aiming to protect your brand, it is important to understand which shelf life parameters impact the quality of your product over time. A shelf life study should encompass any indicators that could limit shelf life, and, optimally, it will also correlate analytical and sensory data.


Is it Safe?

Quality vs. Safety

I have on more than one occasion watched people throw away canned foods, condiments and sauces, declaring them “unsafe” because the expiration date has passed. While it’s true that the quality may begin to degrade some, it is not necessarily inedible. The reason a product is able to sit on the shelf for six months or a year in the first place is because it is processed to ensure microbiological safety during extended ambient-temperature storage. Canned foods do not become unsafe overnight, even if the date printed on the bottom of the container says yesterday. On the other hand, the quality of a product is impacted over time by both intrinsic factors, such as moisture, pH, fat content, and extrinsic factors, such as temperature, humidity, oxygen exposure. If the shelf life of a product is based on a storage temperature of 74°F but it is kept in a hot, humid room, then there is a good chance that the quality of the food could be compromised, even within its labeled shelf life.

The bottom line is this: the distinction between safety and quality is an important and often overlooked one. There’s a chance that a contaminated product may taste perfectly fine, and, by the same token, a product is not necessarily unsafe simply because it tastes bad or has expired. Well-designed studies and diligent testing provide the groundwork for understanding both the safety and quality of a product.


The Scoop on Swells

When Spoilage Strikes in Commercially Sterile Products

Bloating cans, off-odors, off-flavors and texture defects are some relatively common clues that a product considered to be “commercially sterile” is not meeting expectations. When canned food is spoiled, the recommendation has always been to discard the product and not consume it, right? That’s solid advice, to be sure, but here’s the scoop: canned products can spoil due to many different causes, and not all of them impact safety.

If a product intended to be commercially sterile has spoiled, it is critical for the manufacturer to investigate the root cause. A canned food spoilage analysis can be performed by a reputable laboratory with this testing capability to help identify the cause of spoilage. Sometimes, the integrity of a container is compromised and post-process contamination results in product spoilage. In more serious cases, spoilage could be attributed to under-processing. Depending on the type(s) of microorganisms found in the product, spoilage arising from container leakage may be not be a safety concern, but under-processing is a severe public health hazard. Since there is no way to tell without determining the cause, it is vitally important for the manufacturer to perform a spoilage investigation.

Even with a solid foundation of a process authority evaluation, comprehensive shelf life studies and good manufacturing practices, the continuous monitoring of processing, product suitability and quality fortifies ongoing consumer safety and satisfaction.

Need help determining if your product should undergo a process authority evaluation prior to your shelf life study? Mérieux NutriSciences offers Process Authority Evaluation services for a wide range of FDA and USDA regulated products as well as canned food spoilage analysis and commercial sterility testing. Our biosafety level 2 laboratories can also provide custom-designed shelf life, challenge and process validation studies to understand quality, safety and stability of your product. Contact us to get started today!


Meet The Author

Heather Hart, CFS
Research Microbiology Manager, Mérieux NutriSciences

Heather Hart is the Research Microbiology Manager at Merieux NutriSciences’ Gainesville, FL laboratory, where she designs and oversees shelf life and microbial challenge studies, process validations and antimicrobial efficacy evaluations for food manufacturing, ingredient and sanitizer industries.

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