Variations in Proximate Nutrients, Phytochemicals, and Antioxidant Activity of Field-cultivated Red Pepper Fruits at Different Harvest Times

Red pepper (Capsicum annuum L.), an important horticultural crop, is typically harvested several times within one season. The goal of this study was to elucidate the harvest time-dependent variation and accumulation patterns of phytochemicals and any associated antioxidant activity in red pepper. Fully matured red pepper fruits, grown in an open field, were harvested six times during the season. They were evaluated for their proximate nutrient contents, as well as their minerals, vitamins, capsaicinoids, total flavonoid, total phenols, squalene, phytosterols, and fatty acids, and for antioxidant activity. The content of most phytochemicals varied significantly at different times of harvest. Phytochemicals such as capsaicinoids, vitamin C, total phenols, total flavonoid, β-carotene, and calcium, as well as antioxidant activity, had higher values in the initial and final harvests, while P, K, and Na decreased continuously with the progression of the harvest season. Squalene content increased continuously, while vitamin E and phytosterol contents were relatively stable throughout the harvest season. Different phytonutrients exhibited different levels of harvesting time-dependent variation; capsaicinoid had the highest coefficient of variation (CV, 55.44%), followed by squalene (40.51%), total flavonoids (15.97%), and vitamin C (10.57%). Total vitamin E, phytosterols, fatty acids, and the proximate nutrients were relatively constant, with low CVs (less than 10.0%). Among the phytonutrients, total flavonoids (r = 0.841), vitamin C (r = 0.801), beta-carotene (r = 0.738), and total phenol (r = 0.705) were highly positively correlated with antioxidant activity throughout the harvesting season. These results suggest that the content of phytochemicals, and their associated health benefits, may be affected by red pepper harvest time throughout the harvest season.