RELATIONSHIP BETWEEN RELATIVE HUMIDITY AND MOISTURE ABSORBED IN DRIED FISH PRODUCTS

A dried fish left in a humid place absorbs moisture and is consequently spoiled. Theoretically, the relation between the relative humidity ( ?? ) and the saturated amount of moisture absorbed (We) in dried fish is drawn in a sigmoid curve. Inclination of the curve is dependent on such factors as the ratio (c) of dissolved substance in the absorbed moisture to unsolved substance in the moisture, maximum amount of the moisture (Wn), pressure of saturated humidity (F) at a temperature θ, and a factor (a) depending on a type of dried products. Then, the relation may be written as ?? =(c+1)We/c+We+a/FWe/Wn(Wn-We) Generally speaking, when c, F, or Wn gets the smaller, or when a is the larger, the lower We becomes. The amount of moisture absorbed in the dried products under different humidities started increasing as the relative humidity increased above the level of 0.70 (Fig. 1). Little or no effect was produced for controlling the moisture absorption by keeping the dried products at a specific temperature, or treating the materials in boiling water or in formaldehyde before drying (Figs. 2 ?? 5).