[The hygiene of refrigerated and frozen foods]

Abstract

Health and spoilage hazards arising from refrigerated and deep frozen foods may be due to - raw materials, e.g. pathogenic microorganisms which come from infected living animals or contaminate raw foods during handling. Psychrotrophic organisms have particular significance as pathogens or spoilage organisms as they can multiply also during refrigeration; - improper processing. Temperature abuse and incorrect time/temperature relations are main causes for microorganisms being not destroyed at the expected rate or even getting a chance of multiplying. Proper handling after refrigeration or frozen storage of foods ("hygiene of thawing") deserves also particular attention. - contamination, i.e. initial contamination of raw products which are ready for consumption without further processing (fruits, raw salads). Recontamination which follows a heat process is much more important and occurs before, during and after application of cold. In those cases, again, one has to distinguish between products which (a) are ready for consumption without a process (bakery and confectionary goods, ice cream, drinking milk) and (b) have to pass a process which reduces the bacterial load before consuming the food (ready to eat dishes or other foods ready for reheating in the home). Sites of increased hygienic hazard are a) lack of partitioning "clean" and "unclean" areas and processes, b) defects of sanitation and hygiene of personnel, c) defects of packaging, d) leakage during aseptic filling. Hazards are controlled through product and plant specific analysis of the process flow followed by continuous monitoring the "Critical Control Points". As an example, a report is given on a study on random samples taken from 180.000 prepackaged deep frozen menus which had been produced for a mass meeting. Microbiological monitoring of the process revealed time/temperature relations as critical control points of primary importance. Particular problems arose from any stoppage at the production line. Reliable means to assure food safety and protect consumer's health are HACCP concept based in plant control programs rather than sporadic microbiological monitoring of end products.