Crystallization Kinetics of Low-Melting Point Vegetable Oils

Abstract

Refrigerating or freezing foods in the form of O/W emulsions, such as mayonnaise, in which fine oil droplets (vegetable oil with a low melting point) are dispersed, may bring about oil-water separation. The separation deteriorates the appearance and quality of foods. However, the mechanism has not been fully understood. In this context, the crystallization behavior of vegetable oils with low melting points was investigated to elucidate the destabilization mechanism of the O/W emulsions containing such oils. In particular, focusing on the crystallization induction period, which is defined as the time it takes for vegetable oils to cr ystallize during the freezing process, the phenomena occurring during the period was examined from the viewpoints of temperature, stress, volume, crystal structure, and so on. Although the induction period of crystallization depended on the storage temperature and the type of vegetable oil, a method was proposed for predicting the period by considering the degree of supercooling of vegetable oil and the chemical structure of its constituent triacylglycerols (TAGs). It was also suggested that the destabilizing behavior of the O/W emulsions can be explained based on the properties of the TAGs constituting the vegetable oil and the degree of supercooling of the oil.