Protein fraction producing off-flavor headspace volatiles in peanut seed

The free amino acids involved in the sugar-amine nonenzymatic reaction are believed to originate following thermal breakdown of unknown protein(s) during roasting. This study was conducted to identify the seed protein(s) involved in the production of off-flavor volatiles, especially the n-methylpyrrole, in roasted peanuts. Peanut (Arachis hypogaea L. cv. Florunner) seed proteins were separated into 10 fractions by gel filtration on a Sephacryl S-300 column. These fractions were heated, and the resulting headspace gasses were tested for flavor volatiles. The data showed that of the 10 protein fractions evaluated, only the peak I fraction produced the headspace volatiles. The volatile compounds included the ones responsible for off-flavors, as well as some unknown compounds. Peak I was found to be protein in nature and to contain sulfur. Further fractionation of peak I showed that the cryoprecipitate and dialysis-precipitate produced mainly hexanal, while the cryosupernatant and dialysis-supernatant produced a complex mixture of headspace volatiles. The data suggested that some of the peak I proteins appear to be responsible for the production of off-flavor roasted volatiles in peanut.