Superchilling, ice fraction and quality
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The scope of the current experiments was to superchill a selection of fresh food by two superchilling methods followed by extensive storage studies and monitoring of quality during superchilled storage. Several methods for superchilling have been implemented at fish processing sites, but to a very limited extent and not adjusted to automated production lines. The current study presents measurements of the efficiency and precision of two methods for superchilling (liquid CO2 injection and air chilling) as well as their applicability for the expected development towards automated production lines in fresh food manufacturing. Secondly, as a precision index, the effect of the amount of ice caused by superchilling was investigated with respect to prolonged shelf-life and end product quality. Superchilling by means of liquid CO2 injection (LIC) and air chilling both gave an acceptable and reproducible ice fraction within a short period of chilling time (1-2 minutes). Analyses of drip loss, liquid loss and microbiological quality during storage showed that superchilling improved the shelf life of salmon and chicken fillets significantly - being an important contribution to food safety of fresh food. However, within the tested boundaries for ice fraction, the level of ice stored inside the fillets did not seem to considerably influence on the physical and microbiological quality of the products.