|
We offer shelf-life testing services for various food products to assist with the determination of ‘sell by’ dates to ensure that a product is acceptable and meets consumer expectations.
A product reaches the end of its shelf-life when it no longer maintains the expected quality desired by the consumer. The term ‘shelf-life’ extends from when there is no acceptable change in a product, to where a predetermined degree of acceptable change has occurred in certain characteristics, such as: spoilage, flavour, texture, appearance and functionality. |  |
Product characteristics affecting shelf-life
| Spoilage
Microbial spoilage occurs in products which provide an environment that supports microbial growth, or are subjected to contamination during storage. Chemical spoilage occurs through the leaching of chemicals, or similar reactions, promoted by long-term contact with packaging materials. |
Texture
Products containing similar ingredients don’t necessarily exhibit similar textures. Water contributes greatly to a product’s texture. Staling, breakdown of gel structures, phase separation, water activity, moisture migration and crystallization all contribute to textural changes during storage. |
Appearance An unacceptable appearance in colour resulting in browning or fading, is caused by fat and/or moisture migration and chemical reactions. Other processes affecting appearance making it undesirable during storage include surface crystal formation, phase separation, syneresis and caking. |
Flavour
Off-flavours developed during storage are often due to chemical reactions or microbial growth. Rancidity occurs as a result of oxidative reactions and produces off-flavours. |
| Functionality
A product is considered unacceptable and unusable when it loses its functional properties such as a vitamin-fortified product losing its potency, or a chemical leavening agent losing its ability to produce gas. |
Storage Trials
Real time shelf-life trials are always recommended, but where a particularly long shelf-life is desired, accelerated shelf-life trials can be used to provide an indication as to whether the required shelf-life is likely to be achieved. Acceleration of storage under normal conditions is achieved by elevating the temperature above ambient. A temperature of 37°C is commonly used for accelerated trials of products normally stored at room temperature. Although this is generally effective for chemical reactions, microbial or enzymatic changes cannot be simulated in this way (see microbial prediction) and melting of fats can also be problematic at higher temperatures.
| For this reason, guarantees of actual shelf-life cannot be given based on accelerated trials due to the complexity of food products, which may not allow accurate prediction. Knowledge of the Q10 value (a measurement of the temperature sensitivity of a food product) is valuable. The Q10 value is determined by storing the product at two temperatures, usually 27°C and 37°C, and from the respective shelf-lives at the two temperatures, a Q10 value is calculated. |  |
| This value can then be used to calculate the expected shelf-life of the product at other temperatures. Full-term shelf-life trials should always be conducted on completion of product development. Freshly packaged samples are taken at Day 0 for microbial analysis and factors such as colour, viscosity and sensory attributes that may be affected by storage. Samples are then stored in temperature controlled climate cabinets and analysed for the various attributes every second or third week depending on the desired shelf-life. | |
Indicative Costs
 |
An indicative cost for a 12-week accelerated shelf-life study at one temperature (i.e. representing a year at standard storage conditions) is around R 5 000 (excluding VAT). Specific quotations are prepared for each study, as costs may vary according to the length of the trial, as well as number of products/variants being tested simultaneously. The study includes microbial prediction and use of a trained sensory evaluation panel to assess the product, but the analytical costs to track specific components of interest, e.g. vitamins, are excluded. It is also assumed that the client supplies the finished product for the testwork. |