The effects of consumer freezing of food on its use-by date

Abstract

The current Food Standards Agency consumer guidance states that consumers can freeze pre-packed food right up to the “use-by” date and, once food has been defrosted, it should be consumed within 24 hours. This strategic review has collated relevant data to determine whether there is an increased risk in relation to freezing ready-to-eat and non-ready-to-eat foods on the use-by date compared to the day before the use-by date. The review has focused on how the shelf-life of a food is determined and the effects of freezing, thawing and refrigeration on foodborne pathogens, including Bacillus spp., Campylobacter spp., Clostridium botulinum, Clostridium perfringens, Listeria monocytogenes, Salmonella, pathogenic Escherichia coli and Shigella spp. In the UK, food business operators are responsible for setting the safe shelf-life of a food which, in practice, should take into consideration the consumer habits, as well as the factors affecting shelf-life, such as food product characteristics, food processing techniques, transport, retail and domestic food storage temperatures, and type of packaging. Some countries, such as Ireland, New Zealand and Canada specifically recommend including safety margins within shelf lives. This is used to maintain brand integrity because it ensures that the food is consumed in its optimum condition. The FSA has collaborated with other organisations in the production of several guidance documents; however, there is no explicit requirement for the consideration of a margin of safety when setting shelf-life. There is also no legal requirement in the UK to consider a safety margin when setting shelf-life. According to regulations, pathogens should not be present in sufficient levels to cause foodborne illness on the use-by date, as food should still be safe to eat on that day. Given that these requirements are met, the risk assessed in this report arises from the processes of freezing, thawing and subsequent refrigerated storage for a further 24 hours, and the potential for these to increase pathogen levels. In this review, it was found that there is a risk of additional growth of certain pathogens during the refrigerated storage period although the impact of freezing and thawing on the extent of this growth was not readily evident. This risk would relate specifically to ready-to-eat foods as cooking of non-ready-to-eat foods after defrosting would eliminate pathogens. This report explores the potential issues related to consumer freezing on the use-by date and identifies additional information or research required to understand the risks involved. Overall, there is little evidence to suggest a significant change in risk between consumers freezing ready-to-eat food on the use-by date compared to freezing the food on the day before the use-by date. Specific areas that merit further research include the risks due to low temperature survival and growth of L. monocytogenes. There is also a lack of research on the effects of freezing, defrosting and refrigeration on the growth and toxin production of non-proteolytic C. botulinum, and the growth of Salmonella during domestic freezing and thawing. Finally, more information on how food business operators set shelf-life would enable a better understanding of the process and the extent of the safety margin when determining shelf-life of ready-to-eat and non-ready-to-eat foods.