Chemical composition and effect of thermal processing methods on polyphenol content of two Iranian acorn varieties

In the present study, chemical composition and the effects of different processing treatments including boiling, autoclaving, roasting on the reduction of polyphenol compounds of two acorns varieties namely Quercus branti var. persica and Quercus castaneifolia var. castaneifolia were investigated. There were significant (P < 0.05) differences among the acorn varieties in terms of crude protein, oil, fiber, ash, carbohydrates, fatty acids and mineral content. Polyphenol content in Q.castaneifolia and Q.branti were 9.11 and 4.33 (gr/100gr d.b), respectively. Except roasting treatment, other investigated processes caused a significant (P≤0.05) decrease in the polyphenol contents as compared to the raw samples. In roasting treatment, the polyphenol content increased for two varieties as the roasting time and temperature increased. Boiling reduced the concentrations of polyphenols of Q.branti by 14-52% and of Q.castaneifolia by 47-52% while in autoclaving treatment 51.33-62.94% and 46.4 49.94% of poluphenol content were decreased, respectively. Boiling for 60 min and autoclaving for 30 min caused the highest reduction in polyphenol content for Q.castaneifolia and Q.branti, respectively.