Effects of cooking methods on the β-carotene levels of selected plant food materials.

In the present study, the β-carotene contents of 14 plant food materials prepared by boiling, steaming, or baking or when they are raw were analyzed and compared. After boiling three pulse species, namely, peas, kidney beans, and dried mung beans, β-carotene contents of peas and kidney beans increased significantly, whereas that of mung beans (dried material) decreased. True retention factors of β-carotene contents in the cooked kidney beans, peas, and mung beans after boiling were 174.2, 128.3, and 91.8%, respectively. After steaming, the β-carotene content of regular millets significantly decreased but that of taros increased, in which the true retention factors were observed with β-carotene contents of 72.4% in the steamed regular millets and 160.9% in the steamed taros. Moreover, β-carotene contents in yellow-fleshed sweet potato (raw: 896.2 μg/100 g) decreased by baking (786.4 μg/100 g) and steaming (steaming: 553.1 μg/100 g). These results suggest that β-carotene contents in the selected plant food materials markedly depend on the cooking method and plant food materials classification.