Food preservation science is the branch of food science concerned with understanding and controlling the microorganisms — and the enzymes — that spoil food or make it unsafe. It studies how bacteria, yeasts, and moulds grow in different foods, what kills them or stops them multiplying, and how processing and storage conditions affect their survival. From this knowledge come the practical tools of preservation: thermal processes such as pasteurisation and sterilisation, refrigeration and freezing regimes, water activity and pH control, preservatives, packaging atmospheres, and predictive models of microbial behaviour. The discipline also covers the validation of shelf life and the investigation of spoilage and food poisoning outbreaks. It is the scientific backbone of the food industry’s safety systems, including HACCP.