The antioxidant acitivity of synthetic tocopherol (α-T), natural mixed tocopherols concentrate (m-T) and butylated hydroxyanisole (BHA) have been investigated for various types of margarines; soft and hard types with or without skim milk, respectively. Margarines were preserved at 5°C, 25°C for 6 months and compared with development of acid value (AV), peroxide value (POV) and remaining ratio of β-carotene, vitamin A (V.A) and α-tocopherol. Margarines containing skim milk and preserved in cooler place (5°C) were stable for 6 months without antioxidant. However, preserving them at 25°C, hard type margarines were more stable than soft type ones. Those added with skim milk (1.6%) showed relatively high antioxidative effect. m-T and BHA showed nearly the same antioxidant effect, but α-T showed slightly lower effect than these former two. The synergistic action for antioxidative effect was observed between skim milk and other antioxidants. The higher POV and AV, the lower the remaining ratioes of β-carotene, V.A, and α-T were. The degradative ratio of β-carotene and V.A, was recognized to be the same but that of α-tocopherol was higher than the former nutrients.
Overlaps of glutamine and asparagine with threonine in aminogram were proved when the samples prepared by the Stein and Moore's procedure were analyzed with Technicon amino acid analyzer by means of gradient elution technique. A simple procedure was developed to remove these acid amides. Biological samples for amino acid assay, prepared by routine procedure, were dissolved in citrate buffer (pH 2.2) and heated at 120°C for 15 minutes. This procedure results in the conversion of asparagine into aspartic acid and of glutamine into ninhydrin-negative pyrrolidone carboxylic acid. The heated samples are could be served for analysis without any further treatment. Precautions have to be taken to keep the strict heating conditions, otherwise glutamic acid in samples also converts into pyroglutamic acid.