As a part of studies on a method to prevent low-temperature deterioration of hardened coconut oil series, examinations were made on the addition of various surfactants as a means of preventing such phenomenon and it was found that these agents were classified into kinds, i.e., those that are really effective, those that have no effect and those that rather promote deterioration.
1) Addition of 0.52% of monostearin, monopalmitin or monolaurin, irrespective of the kind of glyceride and the amount added, showed increase in A.V. in the same degree as well the control samples of without addition, indicating that they have practically no effect of preventing deterioration. Uneven surface of the crystals was almost the same as that of the control samples.
2) Addition of 0.51% of sorbitan mono-fatty acid ester, polyoxyethylene sorbitan mono-fatty acid ester or lecithin indicated no increase of A.V. even when allowed to stand at 15°C for 6 months. The crystal surface, though with some difference according to the agent used, was composed of fine crystals, some being almost amorphous and the surface was smooth. Consequently, addition of a small amount of this kind of surfactants will be able to prevent deterioration completely.
3) Addition of sucrose fatty acid ester was almost in effective in preventing deterioration, although A.V. increase remained small in some. The crystal surface was indefinite but well grown and uneven.
4) Addition of malic acid monoglyceride ester resulted in a more marked increase of A.V. than the control sample. A large single crystal was formed on the surface which was highly uneven, showing that this agent rather promoted deterioration.
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