Identification of Volatile Compounds Contributing to the Aroma of Pennycress and Camelina Seeds and Protein Extracts

Abstract

Pennycress (Thlaspi arvense L.) and camelina (sativa) are two oilseed crops from theBrassicacea family. They can be planted as cover crops and offer agricultural and economic benefits when used in rotation with other common crops. These crops are being investigated for potential uses in the food industry due to their high protein contents. Minimal knowledge is known about their inherent volatile compounds and how they change during processing to yield a food ingredient. One variety of both pennycress and camelina, bred by Dr. David Marks and affiliates at the University of Minnesota, were analyzed to identify volatile compounds that could impact overall aroma. Plant seeds were ground, defatted, and then optimized alkaline and saline- solubilization protein extraction protocols produced a high protein isolate. The seeds, defatted meal, alkaline-solubilized protein isolate, and saline-solubilized protein isolate of each crop were analyzed using a purge and trap flavor extraction method. Gas chromatography-olfactometry- mass spectrometry analysis was used to identify volatile compounds and address their potential impact on overall aroma of the products during selected processing steps. Compounds were identified based on mass spectra, retention indices, and aroma descriptors. Volatile compounds that produced the strongest odors based on olfactometry were identified as potential aroma impact compounds. In pennycress seeds, compounds that produced an overwhelmingly intense odor were sinigrin degradation products (allyl isothiocyanate) and other sulfur-containing volatile compounds that produced a pungent garlic or radish odor. The compounds that produced an intense odor in the defatted meal of pennycress were similar to the seeds, but also contained aldehydes associated with lipid degradation. The identified compounds that produced an intense 4odor in the alkaline extracted protein isolate were some sinigrin degradation compounds, but largely other volatile sulfides that produced an intense garlic odor. Few compounds produced an intense odor in the saline extracted protein isolate and typically were aldehydes derived from lipid degradation, while the other volatile sulfur-containing compounds were in much lower concentrations. The overall odor of the saline extracted protein isolate was very mild in comparison to the seeds, defatted meal, and pH extracted protein isolate. The camelina seeds and defatted meal had fewer and less intense mustard aroma compounds compared to pennycress seeds and defatted meal. Intense odor producing compounds in the seeds were mainly aldehydes and alcohols, along with allyl isothiocyanate. The defatted meal contained similar compounds to the seeds, but had a wider variety of compounds that produced a mustard aroma. The alkaline extracted and saline extracted protein isolates were much more similar in overall odor and identified volatile compounds compared to the pennycress protein isolates. Intense odor producing compounds in both the alkaline and saline isolates were lipid derived alcohols and aldehydes as well, with the alkaline extracted isolate producing more compounds with an intense odor. This analysis shares some insight on aroma profiles of the crops, but also shows how protein extraction processing changes the overall aroma. The results could be used to further breed crop varieties by removing aroma precursor compounds and identify processing conditions that affect the overall flavor of a protein isolate obtained from these crops.