Studies on the Deterioration of Frying Oils in Continuous Water-sprying and Heating System. VIII

Frying Quality of Kapok Seed Oil

Abstract

To characterize kapok seed oil as frying oil, stabilities of the oil against thermal oxidative and hydrolytic deterioration and some related deteriorations were examined in the continuous waterspraying and heating system (Fig.-24).
In this experiment, practical increase of acid value was not observed, and the oil showed verygood stability against hydrolytic deterioration, whereas it was very unstable against thermal oxidative deterioration, that is, rapid increase of viscosity and forming tendency was observed. When the fat surface was protected from air by means of metal float, these thermal oxidative deterioration was remarkably prevented, and in addition, the oil after heating maintained its light colour and good stability against autoxidation at room temperature.
As shown in Fig.-5, in the case of addition of refined kapok seed oil to soybean oil, remarkable improvement was observed in the hydrolytic deterioration of soybean oil.
The high stability against hydrolytic deterioration of kapok seed oil may depend on the high content of cyclopropenoid fatty acid in the oil. As proved by Nunn et al. cyclopropene group reacts with carboxyl group easily (Fig.-1). Free fatty acid which occurs during treatment may combine with cyclopropene group and thus the free fatty acid concentration in the oil may be kept very low and the autocatalytic action of free fatty acid to hydrolysis is prevented. On the other hand, the high sensibility against thermal oxidative deterioraton may also depend on the cyclopropenoid fatty acid in the oil.
Accordingly, when fat surface is protected from air during frying, kapok seed oil is considered as a stable frying oil and also as a very effective stability improver against hydrolysis of other frying oils.