The shelf life of food is the length of time in which a product is acceptable and meets consumer expectations regarding its quality, according to Graf and Saguy, in the Food Product Development, From Concept to Marketplace. However, the quality of almost all foods decreases over time, and there is a natural need to evaluate how long these products will be able to maintain their commercial value. Shelf-life testing is well designed to provide an objective measure of the quality factors that define the food and the point at which failure occurs. This failure is when the food exhibits physical, chemical, microbiological, or sensory characteristics that are unacceptable to the consumer.
Shelf life testing can be quite a difficult, daunting, and expensive task. Quality parameters must be monitored periodically for as long as the test is conducted. Such trials usually last at least as long as the required shelf life of the product. Sometimes, this may be as long as a year or more. Such an extended test does not coincide with a three-month product development cycle. The amount of sample required can be very substantial, as well as the costs of the analysis.
Most shelf life testing is microbiological or sensory evaluation. With some food products, however, the product developer can be analytically determined by an index of deterioration throughout the shelf life, that is, a chemical or physical property that corresponds to the sensory quality of the product. Examples include moisture, water activity, peroxide value, headspace oxygen content, redox potential, malondialdehyde, trimethylamine in decomposing fish, water-holding capacity, and loss of ascorbic acid.
If it is impossible to establish an analytical test index of shelf life, a variety of techniques have been offered to reduce the testing effort in some fashion. Statistically, experimental designs that minimize the required samples may reduce the testing cost while still providing reliable and valid results. The extrinsic factors that do affect the shelf life of the food are those that present in the process, packaging, and storage of the product. Mainly include:
- Exposure to sunlight
- Damage to packaging
- Distribution and places of sale
During the different manipulation processes of the product, it is vital to control its interaction with the components of the external system. To efficiently maintain this method, every little detail counts: the light permeability of the packaging, distribution of humidity, and relative temperature, both in storage and in transportation, are the main external factors to be monitored and optimized.
Various accelerated shelf life testing methods have been developed. They include:
The methods most used today to estimate the shelf life of foods are:
These real-time studies consist of storing the product under conditions similar to those it will face and monitoring its evolution at regular intervals. The main advantage of the method is that it accurately estimates the time it takes for a product to deteriorate; however, they are studies that usually take a long time and do not consider the fact that the storage conditions of a product are not always stable over time.
This method consists of experimentally introducing pathogens or microorganisms into the food during the production process so that the product does get exposed to the conditions it will suffer in real life. The main con of this type of test is that the effects caused by the studied parameters are the only things analyzed, and the fact that the product can be faced with multiple factors simultaneously is not addressed. In addition, they are studies that are pretty complex and difficult to implement.
This methodology studies the different microbial responses of foods to all varying environmental conditions based on mathematical and statistical models to predict the behavior of the microorganisms in the product. This type of study is widely used when developing a new product, and does consider the possible changing of conditions of a product. However, its main limitation is that it implies greater complexity for the manufacturer and that the results correspond to a simulation, which may be inaccurate.
Accelerate shelf-life tests
In these tests, conditions that include temperature, oxygen pressure, or moisture content are modified to accelerate spoilage reactions of a food. These predictions allow one to predict the behavior of foods in certain conditions and estimate how they will evolve under certain storage conditions. Accelerated tests include changing environmental conditions and concentration variations of the ingredients they are composed of. These studies are versatile, low cost for the manufacturer, and allow for comparing different scenarios. Since it is not an exact representation of reality, there is some margin of error in the obtained results.
It is a type of study based on the consumer’s opinion about the product’s physical characteristics. It consists of knowing people’s attitudes towards the same product with different dates of manufacture to determine if they would consume it or not. This method seeks to establish a relationship between the shelf life and the product’s perceived quality. Although it is not a method to accurately estimate the shelf life, it is essential to do it in a complementary way in order to establish the best by date of a product.
The interest in preserving food does go very far back in time. People used methods such as Salting, pickling, or drying in the sun and air were the first attempts to extend the shelf life of food. Today, thanks to food industrialization, companies are responsible for determining the shelf life of their products and providing good quality food. The search for the quality leads producers to conduct studies and learn the factors that cause the deterioration of their products to have a sustainable basis for making decisions, from the type of packaging, distribution, or use of antioxidants to protect food against oxidation.
Shelf life testing is important for any business in the food manufacturing industry. Shelf-life testing helps companies understand how long their products will maintain an acceptable degree of quality after they are manufactured. This then helps companies establish accurate expiration dates for their food products to ensure the best experience for their end consumers.