A dimeric oxidation product (5-y-tocopheroxyy-tocopherol) has been isolated from soybean oil and identified. The dimer content in extracted oil was increased by elevating the moisture level in raw soybeans. With moisture increase, no change in the quantity of a-tocopherol was observed, but y-and 8-tocopherol contents were greatly decreased and two kinds of dimer were formed from Y-and 8-tocopherols. When the moisture level in moistened beans was lowered, these dimers reverted to their corresponding original toeopherols. The same results were obtained by treating pulverized soybeans with various reducing agents. y-Tocopherol added to autoxidizing soybean oil was oxidized more easily in the presence of oxidation products derived from tocopherols and turned into the dimeric product.

Tocored as a precursor of color reversion of soybean oil has been isolated and identified. We have found that the moisture of raw soybeans is closely related to the tocored content in crude oil and the yield of tocored is maximum when the moisture of soybeans is 15~18%. It seemed that tocored in crude oil were completely removed by the refining processes, but 30% of it remained in the colorless form in refined and deodorized oil and turned into tocored during storage or on heating the oil to a higher temperature. Tocopherols are relatively stable in refined oil and are not oxidized to tocored under a milder condition, such as the oxidation with air. Neither tocopherol nor tocored but "tocored in colorless form" is reall y the precursor of color reversion in soybean oil.

Tocored, an oxidation product of tocopherol and its model, 2,2,7,8-tetramethyl-5,6-chromanquinone reacted with methyl linoleate at an elevated temperature to form an adduet with isomerized linoleate. Oxidation of tocored in fatty esters produced a variety of products, depending on the degree of unsaturation of the esters. With methyl palmitate no addition product was detected but tocopurple and tocoreddimer were identified as minor products irrespective of the degree of saturation. A mechanism involving the interaction of tocored with lipid radicals to yield an adduct as the consequence of antioxidative action of tocored is postulated.

Properties and minor constituents were examined for soybean oils obtained from soybeans with various moisture contents. Yields of crude oils by extraction process of experimental scale anotocopherol content in the extracted oil were found to be correlated to the. , . moisture content in soybeans (moisture range, 8_18%). When moistened raw soybeans (moisture 18%) are dried (moisture 8%), the tocopherol content in the extracted crude oil from the dried beans increased. This phenomenon can be observed only in the case of drying whole beans and not in the case of drying crushed raw soybeans. When soybeans with ordinary moisture (moisture 13%, tocopherol 1.25 mg/g) are dried to reduce the moisture to 1.9%, the tocopherol content in the extracted crude oil increases (1.90 mg/g), but it decreases (0.33 mg/g) again when the dried soybeans are moistened (moisture 18%).

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