Effect of crop maturity stages and lactic acid fermentation on nutrient absorption properties, and bioaccessibility of Fe, Zn and Ca in Spinacia oleracea L

This study explores the variability in nutritional composition of spinach at different maturity stages and assesses the effects of fermentation on reducing oxalates and enhancing minerals bioaccessibility. Spinach harvested at the age of 4th to 6th weeks was processed as raw, blanched, and fermented to develop freeze-dried powders. The growth stages of spinach from the 4th to the 6th week showed a significant (p < 0.05) increase in crude fiber (12.1 – 16.1 g/100 g), protein (6.6 – 12.1 g/100 g), inorganic residues (9.7 – 12.3 g/100 g), total carbohydrates (75.0 – 65.4 g/100 g), Fe (150 – 297 mg/kg), Ca (147 – 236 mg/kg), vitamin C (96 – 111 mg/100 g), and total oxalates (1.46 – 2.35 g/100 g) on a dry weight basis (d.w.). The lowest levels of oxalates were recorded in 4 week-old raw, blanched and fermented spinach, i.e., 1.46, 1.07 and 1.01 g/100 g d.w., respectively. The bioaccessibility of Fe, Zn, and Ca were the lowest in 6th week old spinach, while fermentation with Lactiplantibacillus plantarum v299® improved the bioaccessibility of Fe, Zn and Ca from 19.6 % to 26.7 %, from 32.4 % to 41.6 %, and, from 19 % to 33.9 %, respectively. In conclusion, the findings showed that blanching in combination with lactic acid fermentation in spinach was effective in reducing antinutrients, specifically oxalates, and increasing mineral bioaccessibility.