The mechanism of color reversion in soybean salad oil

An enzymatic reaction might be the major cause of color reversion in soybean oil. During the soybean flaking process, enzymatic reactions take place to convert γ ‐tocopherol to 5‐(tocopheryloxy)‐ γ ‐tocopherol ( γ ‐TED), and then further convert γ ‐TED to the precursors which are the cause of color reversion. The variations of γ ‐tocopherol and γ ‐TED contents in soybean oil are accompanied by an inverse change in the precursors’ concentration. Therefore, the contents of γ ‐tocopherol or γ ‐TED in crude soybean oil could be used as an index for predicting the color quality (color reversion) of soybean salad oil. Almost all the precursors (such as tocored) were converted to color‐reverted substances under catalysis after bleaching treatment, and they were converted back to the precursors during deodorization. Those precursors might be gradually reconverted into the color reverted substances during storage to cause the color reversion in soybean salad oil.