Comparison of Light-Colored Soy Sauce (Usukuchi) with Regular Soy Sauce (Koikuchi) on Rheological Properties of Various Boiled Vegetables

Abstract

Effects of light-colored (Usukuchi) and regular soy sauces (Koikuchi) on rheological properties of boiled foods were determined using a rheometer. The amounts of soy sauces were added to the ingredients with the same levels as those providing the highest and best scores for the sensory test. A taro corm, potato tuber, pumpkin fruit, Japanese radish root and carrot root were boiled according to a recipe in an electric cooker. Firmness of taro, potato and Japanese radish boiled with Usukuchi was significantly softer than that boiled with Koikuchi. The cooking time of taro with Koikuchi was longer than that with Usukuchi, but the tissue of taro boiled with Usukuchi was still softer. In a boiling test at the same NaCl concentration of 2.0% (w/w), the firmness of boiled potato decreased in order of NaCl alone solution, Usukuchi and Koikuchi solutions. Therefore, the taste or food texture of food boiled in Usukuchi might be due to the cooking property of this sauce, which softened the firmness of the boiled food as compared with that of Koikuchi. The cooking property of Usukuchi might be influenced by its higher concentration of NaCl, and also the co-existence of organic acids, amino acids and browning products.