Measurement of Deterioration of Frying Oil Using Electrical Properties

本研究では, 電気的物性(比誘電率, コンダクタンス)と複数の劣化指標(酸価, 重合物量, 色度)との関係について検討を行った. 実験試料には, フライ食品の製造現場において採取したフライ油を使用し, フライ油の電気的物性および劣化指標を測定した. 実験の結果, 以下のことが明らかとなった. (1)フライ油の劣化度が増加するに従い比誘電率およびコンダクタンスは増加する傾向を示した. 特に, フライ油の劣化度とコンダクタンスとの間には明瞭な相関関係が認められた. (2)フライ油のコンダクタンスの温度依存性の傾き(dG/dT)と劣化度との関係を検討したところ, 酸価, 重合物量, 色度ともdG/dTとの間に極めて良好な相関関係が認められた. (3)以上の結果より, コンダクタンスの温度依存性を利用することにより, フライ油の劣化度を容易に把握できる可能性が示唆された.In this study, the relationship between the electrical properties of frying oil (relative dielectric constant and conductance) and its deterioration indicators (acid value, amounts of polymerized triacylglycerols and chromaticity) were examined, focusing on the changes in electrical properties that accompany deterioration. The samples of frying oil used in this experiment were collected from fried food processing sites (school, hospital and factory feeding centers) and were collected at closing time every day for a maximum of ten days. An LCR meter was used for measurement of the electrical properties of the oil, and the relationships between the deterioration indicators and the electrical properties of samples used for various lengths of time were examined. It was found that more deterioration in the frying oil resulted in a greater relative dielectric constant and conductance. In particular, a clear correlation between the degree of deterioration and the conductance of the frying oil was observed. In addition, the obtained gradient (dG/dT) of conductance temperature dependence of frying oil used in this experiment showed a strong correlation with all deterioration indicators (acid value, amounts of polymerized triacylglycerols and chromaticity). From the above results, it is clear that the degree of deterioration of frying oil can easily be determined based on the conductance temperature dependence