Title : Analysis of isoflavone content in processed soybean products
Abstract:
Isoflavones, a class of phytoestrogens predominantly found in soybeans, have been widely studied for their potential health benefits, including antioxidant, anti-inflammatory, and estrogen-like activities. As interest in functional foods continues to grow, understanding the distribution and composition of isoflavones in commonly consumed soybean-based processed foods has become increasingly important. This study analysed the total isoflavone content and the composition ratios by form in 71 soybean processed products distributed in Gyeonggi Province and through online markets in Korea. To better evaluate the influence of processing methods on isoflavone profiles, the samples were categorized into tofu products, fermented products, and other processed products. Isoflavones were extracted using 80% methanol prior to analysis, and their contents were determined using high-performance liquid chromatography (HPLC). Individual isoflavones were quantified and classified into glucoside (including malonyl and acetyl conjugates) and aglycone forms. The results showed that the average total isoflavone content was highest in soy powder, followed by bean curd stick, roasted soy powder, soybean, roasted soybean, natto, cheonggukjang, paper tofu, tofu, soybean curd residue, soft tofu, and soybean water. The ratio of glucoside isoflavones to total isoflavones was highest in soybeans (97.84%) and soy powder (97.52%), whereas the ratio of aglycone isoflavones was highest in cheonggukjang (38.49%). Since isoflavones must be hydrolysed to aglycone forms in the human body to exhibit physiological activity, the findings of this study may help consumers and food developers choose soybean-based products with higher nutritional value and functional potential.
