Graduate Thesis Or Dissertation
 

Effect of high hydrostatic pressure and temperature on volatile off-flavors formation in milk

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/00000244g

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  • The aroma of milk has been often defined as bland and pleasant, yet characteristic. Conventional thermal processing of milk can certainly extend shelf life, but inevitably changes its flavor. High pressure processing has been suggested as an alternative for milk pasteurization with improved fresh flavor retention. The objective of this project was to study off-flavor volatile formation in milk subjected to high hydrostatic pressure combined with moderate heating. Two sensitive and accurate new techniques were developed for the analysis of off-flavor compounds. Solid-phase microextraction/gas chromatography with flame ionization detection was used for the analysis of aldehydes, ketones, and dimethyl sulfide. Solid-phase microextraction/gas chromatography with pulsed flame photometric detection was used for the selective analysis of trace sulfur compounds. Milk subjected to different treatment combinations of pressure, temperature and time showed that aldehydes formation is promoted during high pressure processing, while that of methyl ketones and sulfur compounds is inhibited. It was also observed that at the same temperature, off-flavor formation under high hydrostatic pressure differed from that observed under atmospheric pressure. The formation of aldehydes under high pressure followed first order reactions with rate constants increasing with temperature and pressure. Methyl ketones and most sulfur compounds concentrations showed no increase for all treatment combinations. Added food antioxidants significantly inhibited the formation of aldehydes in high pressure treated milk. This suggested that the aldehyde formation pathway under high pressure is not different from that observed under atmospheric conditions. The results obtained in this research work gave new insights on the flavor formation under high hydrostatic pressure, while offering the possibility of designing high pressure processes for milk with extended shelf life and improved flavor.
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