Identification of Volatile Compounds in Pennycress Protein Isolates Produced by Both Alkaline and Salt-Based Processes

Abstract

Volatile off-notes in ground pennycress seeds, ground defatted pennycress seed, and the final protein isolates (produced from the defatted seeds by alkaline or salt extraction) were identified and “quantified” relative to an internal standard. Volatiles contributing off-notes were identified based on mass spectra, retention indices, and aroma descriptors. The compounds that produced the strongest odors based on gas chromatography:olfactometry were identified as potential aroma impact compounds. In ground pennycress seeds, sinigrin degradation products (e.g., allyl isothiocyanate) and other sulfur-containing volatile compounds were most potent. The primary odorants found in pennycress defatted meals were similar to the seeds but uniquely contained additional aldehydes associated with lipid degradation. The volatile profile of the final alkaline-based isolate contained substantial quantities of aldehydes, isothiocyanates/thiocyanates, and other sulfur compounds. The volatile profile of the salt-extracted protein isolate contained fewer volatiles and was much milder in aroma than that of the alkaline-based protein isolate. The aroma of this latter protein isolate was dominated by aldehydes from lipid degradation as opposed to volatiles arising from sinigrin degradation (e.g., thiocyanates).