ABSTRACT
Experiments with lard show that the addition of 10% crude soya bean oil gives a protective index approaching that obtained by the addition of 0.005% of either propyl gallate or tetrahydroxyl-dimethyl-biphenyl (TDBP). In the presence of cupric or ferric salts, however, the percentage of soya bean oil has to be raised in order to obtain satisfactory protection of the lard against oxidation.Dry mixed rations prepared from wheat flour, soya flour, egg powder, dried carrot powder, sesame seeds, sucrose, salt and a suitable concentration of either crude soya bean oil, refined soya bean oil, lard, or lard plus 10% crude soya bean oil, have been kept at 30℃ for over three years without fat deterioration. The rations containing lard or lard plus crude soya bean oil did not give any indication of rancidity even after 160 weeks at 40℃. Under temperatures of 50? and 60℃, they only became rancid after 90 and 52 weeks respectively. Addition of either propyl gallate or TDBP gives only slight improvement in the keeping quality of the rations compounded with crude soya bean oil or refined soya bean oil, and somewhat greater improvement in the ration made with lard.The wrapping material has been shown to exert a profound influence on the keeping quality of the dry rations. Of the 9 different wrapping materials tested, cellophane has been found to be the best; aluminium foil and gum guaiac-treated paper were found also to be excellent, while waxed paper, propyf gallate-treated paper and ordinary untreated wrapping paper greatly accelerate the appearance of rancidity of the rations.