Antioxidant Content and Quality of Fruits as Affected by Nigari, an Effluent of Salt Industries, and Fruit Ages of Sweet Pepper (Capsicum annuum L.)

Summary

This two-year greenhouse trial assessed the use of nigari—a low-cost salt industry effluent—as a fertiliser for sweet pepper cultivation. Application of nigari at 2 mL L⁻¹ increased capsaicin, β-carotene, and ascorbic acid content compared to control, with optimal antioxidant status and fruit quality achieved at 45–55 days after fruit set. The findings suggest nigari is a viable, cost-effective fertiliser option for soilless pepper production, though ascorbic acid peaked at 45 days before declining.

Regional applicability

This research was conducted in Japan and employed soilless (greenhouse) cultivation systems, limiting direct applicability to United Kingdom field conditions or outdoor horticultural practice. However, the findings may be relevant to UK protected cultivation systems (glasshouses, polytunnels) producing sweet pepper, particularly regarding optimisation of harvest timing for phytonutrient density.

Key measures

Capsaicin, β-carotene, ascorbic acid, total soluble solids (°Brix), titratable acidity, fruit quality attributes, mineral composition in fruits and leaves, yield

Outcomes reported

The study evaluated antioxidant compounds (capsaicin, β-carotene, ascorbic acid), fruit quality attributes, yield, and mineral contents in sweet pepper fruits at different maturity stages under varying nigari concentrations. Results showed that nigari application increased antioxidant content and fruit quality, with optimal harvest window identified at 45–55 days after fruit set.

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