Food product shelf life is dependent of several factors e.g. water activity, pH, temperature, nutrition, oxygen, storage conditions and packaging etc. This is also depends on composition of product, methods of preservation and handling practices.

Shelf life determination is a complex process and it requires good food science knowledge and knowledge of that particular product.

It is really a challenge to extend shelf life of a product.

What is Best Before and Use by date?

The best-before date is the last date on which you can expect a food to maintain all of its quality attributes, provided it has been stored at recommended storage conditions and the package is unopened. These quality attributes include colour, taste, texture, and flavour and quality for which you make claims, such as the freshness of the food.

The use-by date is the last date on which the food may be eaten safely, provided it has been stored according to any stated storage conditions and the package is unopened. After this date, the food should not be eaten for health and safety reasons. It is illegal to sell a food product with past use by date.

A food business must ensure that product is capable retaining its characteristics till the use by date or best before date. Nav Labs (Aus) offers expertise in food product shelf life testing, validation and verification. We have network of independent experts who can analyse the test results and make recommendations on shelf life of a product.

Unless a food has undergone a commercial sterilisation process (e.g. canning) or has a water activity which will not permit microbial growth, the rate of growth of spoilage microorganisms is the major factor for determining shelf life of a food product.

The rate of spoilage depends on a number of factors like:

• Food properties (e.g. pH, total acidity, water activity, presence of preservatives either natural or added)
• Environmental factors (temperature, relative humidity, gaseous atmosphere, light)
• Any process designed to kill or retard growth of microorganisms (thermal processing, freezing, packaging)
• The type of microflora present on the food, and the initial population of this.

Moisture and water vapour transfer:

Not only is water (measured as water activity) a critical factor which determines which, if any, microorganisms will grow in a food, many foods are sensitive to loss or gain of water.

This in turn can be affected by the choice of packaging and in many instances will determine which packaging is used.

Many biscuits and savoury snacks including nuts suffer in quality as a result of moisture gain. Some baked foods such as cakes may suffer from moisture loss.

Chemical or biochemical changes:

Numerous possible reactions which could limit shelf life fall into this category. The most important are oxidation, non-enzymic browning, enzymic browning and, in some cases, food and packaging interaction. Oxidation of fats and oils leads to the development of rancidity marked by off odour and flavour. This may limit the shelf life of fats and oils but can also limit the shelf life of many other foods containing fats and oils. Examples of foods stored at ambient temperatures which can develop rancid off flavours are nuts, potato crisps and biscuits.

Many frozen foods can also have their shelf life limited by fat oxidation.

While freezing arrests microbial activity, chemical reactions proceed at a much reduced rate even at recommended storage temperatures. In general, hard frozen food products are given shelf life of 12 months or more.

A number of different vitamins are sensitive to oxygen including vitamin C (ascorbic acid) and vitamin B (thiamine). When vitamins are added to fortified foods such as breakfast cereals or sports drinks and a label declaration made, then shelf life determinations will have to take account of any vitamin degradation which will occur with time in addition to any other changes in quality.

NSW Food Authority has complied information on shelf life testing Click here for more information.