Phenolic profile, color parameters and antioxidant activity of walnut kernel extracts as influenced by different time and temperature during extraction

The aim of the present study was to find the best extraction parameters to obtain the highest amounts of polyphenols and antioxidants from the walnut. Walnut kernels from ‘Alsószentiváni 117’ cultivar were used for extraction. The extraction methods were as the follows:Method 1: shaking water-bath at 50 °C for 30 min.Method 2: shaking water-bath at 50 °C for 30 min, then storing at 5 °C for 20 h.Method 3: shaking water-bath at 40 °C for 30 min.Method 4: shaking water-bath at 40 °C for 30 min, then storing at 5 °C for 20 h.According to our results Method 1 showed the highest FRAP value (34.43 mg AAE g−1), the DPPH value (52,94%) and the highest HPLC peaks for chlorogenic acid, epicatechin and rutin were also seen in extracts obtained using Method 1. TPC values of Method 3 were 26.06 mg GAE g−1 for Method 1 it was 25.65 mg GAE g−1. The results of color values, L* and ΔE* were similar in all extracts as well. In our experiments extraction Method 1 proved to be better than others.