Odor, tastes, nutritional compounds and antioxidant activity of fresh-eating walnut during ripening

The effect of ripening stages on odor, tastes, nutritional ingredients (fatty acid compositions and protein), antioxidant activities, and total phenols content (TPC) of fresh-eating walnut were detected in this study. Fruits which were harvested at 121, 128 and 135 days after full bloom were tagged as stage I, stage II and stage III, respectively. The result indicated that the samples in stage Ⅰ showed the most pleasant tastes and odor. Additionally, stage Ⅰ had the highest antioxidant activities and TPC (0.78 g kg−1). Moreover, stage Ⅱ presented the lowest reducing power (0.295), DPPH scavenging activity (62.19%) and TPC (0.47 g kg−1), however, the highest polyunsaturated fatty acids percentage (75.88%) was also observed in it. Walnut samples of stage Ⅲ was an ideal source of protein (16.28%), though the lower acceptability of odor and tastes were observed in it. Taken together, we concluded that ripening stages greatly affected the green walnuts quality attributes. Our study provides new ideas for choosing suitable ripening stages to meet the different quality demands of walnuts.