水産動物内臓油利用に関する研究-I

Abstract

The author, having reported in his previous papers10)-15) extraction, refining, molecular distillation and concentration by saponification of vitamin oil and esterification of vitamin A alcohol studied in the aspect of fundamental conditions influencing their results as well as in that of important points taken care of in practicing them on industrial scales, now gives a description of the experiments he carried out to determine the stability of vitamin A contained in vitamin oils subjected to these various kinds of treatment, the stability being evaluated in accordance with the length of time in which a sample of vitamin oil is reduced by half in respect of its vitamin A content. In the first place, the stability of vitamin A was compared among liver oil samples obtained from different sources but equally by alkali digestion. As seen from the results of experiment presented in Table 1, liver oil preparations obtained from sharks come out top and those from cods and pollacks, tunas, giant bass and whales follow them in this order in respect of the stability of vitamin A content. It seems likely that the stability order here found is the reflexion of the readiness of undergoing the alkali digestion or in other words the difficulty in removing the natural antioxidative accompaniment of these sources of vitamin A. In the second place, the influence of refining method on vitamin A stability of refined vitamin oil was examined with liver oil specimens obtained by subjecting a crude sample of pollack liver oil to various refining schemes illustrated in Fig. 1, the results being presented in Table 2. As obvious from the table, as for the stability of vitamin A content to be assigned to different methods of refining vitamin oil here examined, crude liver oil comes out top and a liver oil sample subjected merely to filtration, that refined by means of alkali, that treated with acid, that processed with alcohol and that treated with diatom earth come in this order in succession to crude liver oil, the order being again suggestive of the difference in strength of removing natural antioxidant among these types of refining method. In the third place, the effect of molecular distillation as a means of concentrating the vitamin A in liver oil on the stability of this vitamin in distillate oil was inquired by examining the stability of vitamin A with samples of raw oil before distillation, those of distillate fractions respectively obtained at different temperatures and those of residual oil remaining after distillation, the results being shown in Tables 3 and 4. It is seen from these results that, irrespective of whether the source of liver oil is shark or whale, a vitamin oil fraction distilled at the lower temperature has the greater stability of vitamin A, while raw oil shows a value in respect of the stability of vitamin A content, which falls between the stability values for Fractions 1 and 2 both distilling at rather low temperatures. Although the stability of residual oil could not accurately estimated from some reasons, the above-mentioned results for distillate fractions and raw oil seem to be sufficient to suggest that natural antioxidant in liver oil can distill rather earlier than vitamin A. In the fourth place, the products respectively obtained in different working stages of the process wherein a vitamin oil previously concentrated by molecular distillation is subjected to concentration by saponification and the vitamin A alcohol thereby produced is further esterified were examined of their stability of vitamin A content, the results shown in Table 5 being obtained. As seen from the table, concentrated products of vitamin A alcohol prepared from different sources equally show values of stability as good as those found for a pollack liver oil obtained by the alkali digestion method.