The Formation and Release of Odor Active Compounds During Oxidation of Vegetable Oils

Abstract

Autoxidation of unsaturated fatty acids causes deterioration of the quality of edible oils and lipid-containing foods. An important problem is the formation of volatile secondary lipid oxidation products during storage and/or processing (Mistry and Min, 1992). The Majority of these volatile compounds are lipophillic and therefore mostly present in the lipid phase of foodstuff. The release of volatiles in the mouth is controlled by diffusion into and mixing with saliva (McNulty, 1987). This process is affected by the physical state of lipids and by the temperature (Kinsella, 1990). In preparation of low-fat foods decrease of the fat content can affect the release of volatile off-flavors (Roozen et al. 1994). It has been demonstrated that lowering of the oil fraction in emulsions increases the relative amount of hexanal released from emulsions.

The formation of volatile secondary lipid oxidation products during storage and processing has detrimental effects on the quality of lipid containing foods. Release of volatile compounds is diffusion controlled, and is affected by temperature and physical state of lipids. In this study, the development of odor active compounds was investigated in sunflower and olive oils, and their I and 50% oil-in-water emulsions during storage at 55’C. Volatile compounds were analyzed by dynamic headspace analysis, and their odor activity was determined by a trained GC sniffing port panel. The number of odor active compounds detected in the I and 50% o/w emulsions was higher than in the bulk oils. The amounts released of pentanal (buttery note) and hexanal (grassy note) were highest in the 1% o/w emulsions.