Protein and Amino-acid Contents in Backtae, Seoritae, Huktae, and Seomoktae Soybeans with Different Cooking Methods

Purpose: The objective of this study was to provide nutritional information (protein and amino-acid contents) of soybeans (Baktae, Seoritae, Huktae, and Seomoktae) with different cooking methods. Methods: Raw, boiled (in 100±15∘C of water for 4 hr), and fried (in a pan at 110±15∘C for 20±5min ) soybean samples were prepared. Contents of protein and amino acids were determined. Results: Protein content in raw Baktae, Seoritae, Huktae, and Seomoktae soybeans ranged from 361.0 to 386.8 mg/g. Protein contents differed according to cooking methods. They were higher in pan-fried beans (107.9-113.5%) than in raw or boiled soybeans (48.2-49.5%). A total of 18 amino acids were analyzed. Amino acid data sets were subjected to principle component analysis (PCA) to understand their differences according to soybean types and cooking methods. Bean samples could be distinguished better according to cooking method in comparison with bean types by principle component (PC1) and PC2. In particular, fried soybeans contained much higher levels of cystein. Other amino acids were the dominant in raw and boiled ones. On the other hand, the amounts of threonine, histidine, proline, arginine, tyrosine, lysine, tryptophan, and methionine were higher in raw bean samples than in cooked ones. Conclusion: The contents of amino-acids and proteins are more effected by different cooking methods in comparison with soybean types.