Effect of Fluctuating Storage Temperatures on Quality of Frozen Foods

Abstract

LUCTUATING temperatures due to many different condi-F tions may be encountered in the storage of frozen foods. Temporary breakdown of facilities or equipment, improper response of temperature controlling devices, excessive loads during freezing, lack of a separate compartment for freezing, and frequent opening of the cabinet (particularly a side-opening box) all may lead to a temporary rise in the temperature of the stored food.Statements in the literature (1, 3, 10) stress the point that temperature fluctuations should be minimized, either because excessive desiccation may result or because fluctuations may lead to excessive growth of ice crystals in the food. None of these statements is accompanied by data to prove that undue desiccation or crystal growth necessarily is encountered in such cases, or to prove that the food quality is appreciably impaired.Work a t Purdue ( 9 ) indicated that temperature fluctuation over the range -5" t o -15" F. was not deleterious to frozen pork. Workers at Minnesota (4) stated that for frozen fruits and vegetables, constant storage temperature is not important if the storage temperature is 5" F. or less. In their study, the temperature fluctuated from 0 " $0 -20" F. with no impairment in food quality in a 6-month period. DuBois and Colvin (8) studied ascorbic acid in frozen peaches subjected to smell temperature fluctuation three or four times daily, and reported that, as a result of fluctuating temperatures between 5" and -5" F., 50% of the originally added ascorbic acid was lost in 1 year, whereas like packs stored at a relatively constant temperature of 0" F. lost but 32% of the vitamin C during stomge. Their data, however, dispute the significance of this statement.If undesirable effects from varying temperatures are to be expected, they will be found in the freezing range above 0" F., the usually recommended storage temperature. Furthermore, this is the range most likely to be encountered in freezer cabinets or lockers subject t o temperature fluctuation. No data are at hand, to evaluate the effects on frozen food of temperature variations in the range of 0 " to 20 ' F. PROCEDURES STORAUE TEMPERATURES. Three conditions of storage were maintained. A standard temperature of 0 " * 2 " F. and a control of 10 " * 2 " F. were maintained as representing constant temperature conditions. A third freezer, equipped with two thermostatic control switches, was carried through a temperature cycle between 0" and 20' F. For 36 hours out of every &day period, the control was set at 20" F.; for the remainder of the period (108 hours), the other control, a t 0" F., was in operation. This cycle was such that the food temperature rose from 0 " to 20 " F. and remained there for several hours before again being lowered to 0 " F. The 6-day cycle was' automatically repeated during the entire course of the 1-year storage period. The cycle represents a magnitude and frequency of fluctuations that may be encountered during frozen food storage without actual exposure t o thawing. on Quality of Frozen ...

Effects of Freeze Preservation on Nutrients

“…Gortner et al (1948) stored pork loin roasts at constant and comparable conditions of fluctuating subfreezing temperatures and found that thiamin stability did not differ between these two conditions. Moleeratanond et al (1981) stored seven types of beef products for 1 year at three different temperature conditions: (1) constant _23°C, (2) fluctuating _23° to _21°C with 12 hr at each temperature, and (3) fluctuating -21 ° to _18°C with 12 hr at each temperature.…”

“…With respect to frozen green peas (Boggs et at. 1960;Gortner et at. 1948), frozen cauliflower (Dietrich et at.…”

“…1948), frozen cauliflower (Dietrich et at. 1962), and green beans (Gortner et at. 1948), losses of vitamin C do not differ significantly between the two conditions.…”

Quality of Frozen Foods — A Review

“…A b o u t 80% of the packages contained an appreciable amount of frost, and 14% contained an excessive amount of frost within the retail packages of frozen vegetables studied. The effect of temperature fluctuation upon the rate of in-package frost and cavity ice formation has been found by Gortner et al (1948) and Klose et al (1955). The conclusions of their studies were that frost formation increased with temperature, and for the -23.3"C to -122°C fluctuation frost formation was considerably greater than for the highest, -12.2"C, constant temperature.…”

Freezing/Thawing

“…Some authors consider temperature fl uctuations to have the same effect on the quality of the product as storage at an average constant temperature (Dawson 1971 ); others consider that fl uctuations may have an additive effect (Van Arsdel 1969 ; Bech -Jacobsen and B ø gh -S ø rensen 1984 ). There is evidence that exposure to temperatures warmer than − 18 ° C rather than temperature fl uctuations may be the major factor infl uencing quality deterioration (Gortner et al 1948 ). of meat.…”