Effects of postharvest piling up in bulk on qualities of Camellia oleifera seeds

The study investigated the effects of postharvest piling up in bulk on Camellia oleifera seed qualities, including moisture content, oil content, fatty acid composition, soluble sugar, soluble protein content, acid value, peroxide value, lipase activity, lipoxygenase activity, and mold colony, under varying relative humidity (60%, 80%, 98%) and time durations (1–8 days). Additionally, it examined the impact of piling temperature and diverse postharvest treatments. The results revealed that piling up in bulk promoted the post-ripening of Camellia oleifera seeds, leading to a gradual decrease in seed moisture content while initially increasing oil content before stabilizing. After 2 days of piling, seed oil content increased by 5.65%, 4.40%, and 1.06% under RH conditions of 60%, 80%, and 98%, respectively. However, after 4 days, the oil content declined by 8.36%, 6.06%, and 4.14%, respectively. The proportions of saturated and polyunsaturated fatty acids declined gradually, while monounsaturated fatty acids increased significantly. The acid value decreased, correlating positively with lipase activity. Mold colonies on seeds increased minimally with piling duration, while those on fruit shells increased sharply by 1–4 logarithmic units after the 4th day. When examining the effect of temperature, higher piling temperatures were found to gradually increase the seed oil content. Based on the order of oil content, the different treatment methods were ranked as follows: piling up in bulk-sun drying > piling up in bulk-drying > shelling-sun drying > direct sun drying > shelling-drying. Therefore, these findings advance our understanding of postharvest piling up in bulk of Camellia oleifera seeds and provide valuable insights for selecting treatment methods and parameters.