A delicate balance needs to be achieved when formulating or reformulating food and drink products. Naturally taste and texture are paramount.
With their direct link to consumer satisfaction, these factors should remain as constant as possible for the duration of shelf-life. Then there is the important issue of food safety.
How do manufacturers walk the line between maximising shelf-life and minimising the risk of people consuming food that is unsafe or of inferior quality?
Over the past 10 years, there have been significant advancements in methods for extending and validating shelf-life. Rather than hypothesising the likely shelf-life based on similar products, then ‘short dating’ to provide a margin for error, manufacturers can conduct more robust scientific trials.
Indeed, shelf-life determination now performs a critical function at the front end of the product development cycle. Used strategically, it can facilitate more informed decision-making surrounding formulation, processing techniques and packaging.
Objectives and timescales for shelf-life testing can vary hugely. The focus may be food safety criteria, micro-structural assessment of changes during storage (separation, graining or alterations in texture, colour and rheology) or a combination of the two. Many interconnected factors can impact shelf-life, making it a complex area.
Selecting The Best Method
There are two core shelf-life testing techniques: real-time and accelerated. In addition, challenge testing is recommended as an essential step for most foods which have a significant risk of containing pathogens or spoilage microorganisms.
Real-Time Microbiology Shelf-Life TestingFor products where microbial stability is the limiting factor, real-time testing is the only option. This covers perishable products with high water activity such as salads, ready-to-eat meals and refrigerated products.
During assessment, changes in the smell, taste and appearance of the product are monitored as spoilage microorganisms develop. Real-time testing plays a critical role in determining the shelf-life of goods produced using the just-in-time systems adopted by many chilled food manufacturers in the UK.
Accelerated Shelf-Life Testing
Food and drink specimens are subjected to stability tests under a range of controlled temperature/ humidity and light conditions. Exposure to extreme conditions accelerates the changes that the product would undergo in normal circumstances.
This predictive method assesses microbiologically stable products for deterioration in sensory characteristics caused by chemical and physical changes.
For ambient stable products and those with low water activity, sensory and physicochemical changes can determine the shelf life. Criteria might include staling, rancidity development, breakdown of texture, loss of flavour, colour changes or loss of functionality.
Findings are used as a benchmark from which to calculate actual shelf life. For long life products which remain safe to consume for weeks, months or even years, ascertaining a value for shelf-life through accelerated testing is hugely advantageous.
Foods at high risk of containing pathogens or spoilage microorganisms usually need to undergo challenge testing as well as shelf-life testing.
This takes microbiological evaluation a stage further, simulating what might happen during production, processing, distribution or subsequent handling by consumers, should the product be contaminated.
The process involves monitoring the growth of inoculated bacteria to establish critical factors that may enable the elimination of pathogens or slow the growth of spoilage bacteria.
Challenge testing can be applied to many different food products using validated methods and it is important to have a broad selection of natural purified cultures of microorganisms to ensure that a wide range of eventualities are considered.
If challenge testing reveals that a product does not have the required level of stability, findings can be used to aid reformulation and obtain a better shelf-life.
Understanding Relevant Factors
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Tight control of ingredient quality and process integrity is vital to ensure shelf-life remains constant across multiple production runs.
Many food manufacturing processes are carefully designed to maximise safety through mechanisms such as microbial inactivation. For instance, if a product has a higher microbial load than expected, heat processing may not be sufficient to reduce the contamination to an acceptable level.
Nevertheless, it is important to minimise variations in the raw materials as far as possible. An ingredient that has been overexposed to air and oxidation processes, for example, may be more susceptible to chemical reactions such as rancification.
By spotlighting weak points in the manufacturing process or the supply chain, from ingredient quality to hygiene issues, it is possible to minimise factors that could compromise shelf-life.
Keep Up With Innovation
Shelf-life extension techniques are continually progressing, and scientific methods to ascertain ‘use by’ or ‘best before’ dates have also evolved significantly.
One area that has changed the face of supermarket shelves in recent years is the interplay of packaging with shelf-life.
Vacuum-packed meats that are good for six months, fresh year-round produce regardless of the season, chilled juice and milk products with weeks or months of shelf-life—all of these are relatively new developments that seemed inconceivable a decade ago.
In order to realise the potential commercial benefits of this trend, manufacturers need to complement in-house knowledge and facilities with specialist third party expertise and services.
External assistance can be invaluable when it comes to optimising a concept or collaborating over complex areas such as product reformulation for shelf-life extension.