Estimation of water intake from food moisture in the Japanese diet using a cooking-based conversion factor for water content

摘要

This study aimed to estimate the water intake of Japanese people from food moisture. For this purpose, we described a water conversion factor for cooking (WCFC) that focuses on how cooking changes the water content of complete dishes and not food ingredients, and investigated methods for calculating the water content of cooked dishes. In this study, we utilized 129 dishes commonly consumed by Japanese people. We measured the water content of the dishes before and after cooking and calculated the percentage of residual water after cooking. The dishes were divided into staple foods or side dishes, and categorized based on residual percentage in water content and cooking method. The percentage of residual water after cooking change in water content in each category was expressed in terms of the WCFC, which is the water content of the cooked dish relative to the uncooked dish. In total, there were 43 categories with a WCFC range of 0.40 to 1.33. Our results revealed that the water content of food is not simply changed by heating-based cooking methods, but by a complex combination of cooking operations. Furthermore, by fitting WCFC to a culinary structuralism theory, it can potentially be utilized for all cuisines and not just dishes in Japan. Additionally, we found that the water content of a day's worth of food calculated using WCFC and actual measurements barely differed, indicating that WCFC could potentially be used to estimate water intake from food moisture.