Impact of cooking methods on folates, ascorbic acid and lutein in green beans (Phaseolus vulgaris) and spinach (Spinacea oleracea)

Folates, ascorbic acid (vitamin C) and lutein (antioxidant carotenoid) concentrations were determined after cooking (boiling and steaming) fresh, frozen and canned green beans (Phaseolus vulgaris) and spinach (Spinacea oleracea). The aim of this study was to qualify and quantify the loss of water soluble (folates and ascorbic acid) and lipid soluble (lutein) micronutrients in the cooked products and liquids and the canning liquor. In canned products, folates were found in the canning liquor. Boiling regardless of product reduced plant tissue folates and ascorbic acid but not lutein concentrations. Loss of folates during boiling occurred due to leaching (diffusion) and ascorbic acid due to temperature (heating). Steaming reduced ascorbic acid but not folate or lutein concentrations. ► We studied the impact of home cooking treatments on folate, ascorbic acid and lutein in green beans and spinach. ► We measured the amount of those nutrients after boiling and steaming fresh green beans and spinach. ► We measured the amount of those nutrients after boiling frozen green beans and spinach. ► We measured the amount of folate in the cooking liquid used for boiling fresh and frozen green beans and spinach. ► Finally, we measured the amount of folate in cans of green beans and spinach and in the covering juice.