Effect of Soaking in Water, Alkali and Acetic Acid to Remove Polyphenol from Kernel of Two Iranian Acorn Varieties

Abstract

The acorn is an edible nut of oak trees (Quercus spp.) that had been used for human nutrition for a long time. Besides nutritious components, acorn contains considerable amounts of phenolic substances. At present study, two different varieties of Iranian oak acorns, namely, Q. branti var. persica (Qb) and Qcastaneifolia var. castaneifolia (Qc) were used. The total polyphenol content measured in two varieties were 9.11 and 4.33 (gr TAE/ 100 gr d.b), respectively. The effects of various processing methods such as soaking in water (at 25 and 50°C), acetic acid and sodium hydroxide (0.1, 0.5 and 1M) and sodium chloride (1, 5 and 10%) for 6, 12, 18 and 24 hours on the polyphenol removal from acorns were investigated. Repeated measures analysis of variance (ANOVA) was applied (P<0.005). All processes caused a significant (P≤0.05) decrease in the polyphenol contents as compared to the raw samples. In water soaking, the percentage of reduction increased for two varieties as the soaking time and temperature increased. In soaking treatments of Qb samples, maximum reduction of the polyphenols was observed in 0.5M NaOH solution for 12h. On the other hand, in Qc samples, soaking in 0.1M NaOH solution, for 18h resulted in significant (P<0.05) decrease in polyphenol compounds. Keywords: Acetic Acid -Acorn Fruit- Hydroxide Sodium- Polyphenol Compound- Soaking