Effects of temperature fluctuation on moisture loss of fresh foods in household refrigerator

Abstract

Household refrigerator which is commonly used, operates the temperature rise and drop of ±2.0℃ distribution inside the fridge. It is well known that food can be deteriorated by a high storage temperature, but temperature fluctuation in fridge also can cause severe quality loss in foods. In this study, the effects of temperature fluctuation on storage quality of fresh foods including eye of round (meat), mackerel (fish), spinach and pak-choi (leafy vegetables) in refrigerator was investigated. According to the samples, mean temperatures were set to -2.5℃ or 0.5℃ (code L) and -1.0℃ or 2.5℃ (code H) and temperature fluctuations were designated in ±0.5℃, ±1.0℃, ±2.0℃ (code 0.5, 1.0, 2.0). Changes of storage quality were identified by measuring protein decay, lipid rancidity and moisture loss of food during the storage period. As a result, there was no significant difference in the degree of protein decay, fat rancidity of eye of round and mackerel between temperature fluctuations condition during storage. However, eye of round was frozen only at L2.0 condition during the storage and mackerels were frozen from the day of 3, 6 and 8 at L2.0, L1.0 and L0.5, respectively. Also, both weight loss of spinach and pak-choi were accelerated as the temperature fluctuation increased. In addition, model food, daikon, was introduced to investigate freezing and evaporation phenomena of stored food according to the temperature fluctuation condition. Freezing phenomenon as larger temperature fluctuation had relevance to that more chance to pass through the freezing point. Thus, ice nucleus could be formed and once nucleation occurred, freezing accelerated. Also, each temperature condition was expressed in terms of periodic sine function with constant amplitude and phase in order to interpretation of evaporation, and the amount of evaporation was calculated according to the temperature fluctuation through cumulative time data. As a results, the larger the temperature fluctuation was, the greater the driving force as partial pressure difference, more heat escaped from the food. In this study, it was verified that relatively constant temperatures had advantages in maintaining moisture on foods. It is expected that this research will be used as a basis for the effects of temperature fluctuation control on fresh food in the domestic refrigerator and it could be used as a valuable reference for refrigerator technology research.