Abstract
In order to study the oxidative deterioration of fats contained in dried foods, model systems consisted of soybean oil or methyl linoleate with casein were incubated under three different humidities, that is, relative humidity (RH) 0% (low), 48% (middle), and 83% (high). Kori-tofu was also incubated in the similar manner.
The changes in lipids and proteins were examined.
1) Incubating soybean oil with various supporting materials, such as, proteins, amino acids, starch, synthetic polymers, etc., at 50°C, the oxidation of soybean oil was depressed when proteins were used as supporting materials.
2) When methyl linoleate (ML) adsorbed on casein was incubated at 37°C, the oxidation of ML was markedly depressed. Formation of polymers occured when they were incubated at 50°C under high RH.
3) When Kori-tofu was incubated under high RH, recovery of extractable lipids was lowered, and polymers were formed accompanied by the loss of linoleic acid, linolenic acid and tocopherols.
4) On the other hand, the residues of ethyl ether extracts of ML-casein and Kori-tofu incubated under high RH showed the decrease in digestibility and the loss of amino acids.
5) The damage of lipids and proteins were considerably suppressed by incubating under middle RH.
