Improvement of nutritional quality of Basella alba (spinach) by altering circadian rhythms during post-harvest storage

Abstract

Leafy vegetables, highly perishable and prone to rapid senescence after harvest, experience a decline in both their longevity and nutritional quality during postharvest storage, as they remain biologically active and undergo metabolic and biological processes that are influenced by entraining internal circadian clocks with external environmental stimuli. The present study was aimed to investigate the effect of circadian rhythms on the nutritional quality of Basella alba (spinach) during postharvest storage. The effect of light and dark treatments on the nutritional quality of spinach leaves was studied by determining chlorophyll, carotenoid, vitamin C and Fe contents during the storage of 1-6 days under different light / dark regimes, i.e., 24h light (LL), 16h light/8h dark (16L/8D), 12h light/12h dark (12L/12D), 10h light/14h dark (10L/14D), constant 24h dark (DD) at 20 oC and constant 24h dark at 4 oC (RDD). Results showed that there was a considerable change in the nutrient contents of spinach leaves at the end of the storage period compared to the initial nutrient content. Initial chlorophyll, carotenoid, vitamin C and Fe contents of the spinach leaves were enhanced at the end of the storage period under 16L/8D treatment by 7.0%, 6.2%, 5.6%, and 14.8%, respectively. In LL and DD treatments, nutrient content decreased significantly at the end of the storage period. Declining of nutrient content was greatest in spinach leaves stored under DD. In 12L/12D treatment, initial nutrient content was relatively maintained 6-day storage period. During the storage period under 16L/8D, 12L/12D, 10L/14D treatments nutrient contents were increased compared to DD and LL treatments. The storage temperature had significant contribution to the preservation of nutrients in spinach leaves. The nutrient contents of spinach leaves were maintained under low temperature storage. Chlorophyll, carotenoid, vitamin C and Fe contents were increased by 29.6%, 12.4% 6.5%, 9.5%, respectively under constant dark at 4 oC (RDD) compared to constant dark at 20 oC (DD). The results exhibited that altering circadian rhythms during the postharvest storage under light/dark cycles and low temperature contributes to maintain nutritional value of spinach after harvest.