Variation of iron, copper, free fatty acid content and lipoxygenase activity in peanut kernels subjected to various pretreatments and roasting.

Peanut kernels subjected to pretreatment including rehydration, blanching and dehydration, and untreated kernels were roasted at 160 degrees C for times ranging from 0 to 90 min. For both peanuts, the iron content in oil and specific lipoxygenase activity in defatted peanut flour decreased, free fatty acid content increased and copper content changed insignificantly with roasting time. Changes of iron content, lipoxygenase activity and free fatty acid content were more significant in untreated peanuts than in pretreated peanuts. At each roasting time, iron, copper and free fatty acid contents in the oils and lipoxygenase activities in the defatted flours prepared from untreated peanuts were higher than in the oils and flours prepared from pretreated peanuts.