Benders'dictionary of nutrition and food technology

202The ice sublimes off as water vapour without melting. Freezedriedfood is very porous, since it occupies the same volume asthe original and so rehydrates rapidly.There is less loss of flavour,texture and nutrients than with most other methods of drying.Controlled heat may be applied to the process without meltingthe frozen material; this is accelerated freeze drying.freezerburn A change in the texture of frozen meat, fish andpoultry during storage due to the sublimation of ice.freezer, cryogenic Freezer using evaporating solid carbon dioxideor liquid nitrogen directly in contact with the food; the latentheat of sublimation or vaporisation comes from the food beingtreated.freezer temperatures For long-term storage of frozen foods (upto 2–3 months), domestic freezers run at −18 °C (0 °F); in UK thisis a three star rated deep freeze. A freezing compartment of arefrigerator (for short-term storage of frozen foods) is between−11 °C (12 °F), two star rated, for storage up to four weeks and−4°C (25 °F), one star rated, for storage up to a week. A threestar deep freeze with a snowflake symbol is one that is suitablefor freezing foods, as opposed to storing ready-frozen food; it hasa higher cooling capacity than a simple storage cabinet.See also date marking.freezing In blast freezing the food is frozen by a blast of coldair; small particle foods may be frozen as a fluidised bed, whenit is supported on an upwards blast of cold air. Plate freezinginvolves contact of the food with vertical or horizontal plates ofrefrigerant-cooled metal. Cryogenic freezing involves directcontact of the food with the refrigerant, which is commonlyliquid nitrogen or solid carbon dioxide.freezing agents Compounds that reduce the temperature of foodsthrough direct contact.freezing plateau The period during freezing when the temperatureof a food remains almost constant as the latent heat ofcrystallisation is removed and ice is formed.freezing time, effective Time required to lower the temperatureof the centre of a food to a predetermined final temperature.frenching Breaking up the fibres of meat by cutting, usually diagonallyor in a criss-cross pattern.freshFor food labelling and advertising purposes, the US Foodand Drug Administration has defined fresh to mean a food thatis raw, has never been frozen or heated and contains no preservatives.(irradiation at low levels is permitted.) ‘Fresh frozen’and ‘frozen fresh’ may be used for foods that are quickly frozenwhile still fresh, and blanching before freezing is permitted.freshening See debrining.