Isoflavones (IFs) are important bioactive compounds which offers several benefits to human health. Despite the importance of IFs content, there are still some deficiencies in the existing methods. The objective of this study is to optimize key parameters of alkaline hydrolysis method for enhancing both reliability and accuracy of quantitative analysis of IFs contents in soybeans and soy protein products. Solvent type, extraction temperature, heating mode, alkaline concentration, hydrolysis temperature, hydrolysis time and some details are key points to target analytes which yield determining parameters. The biggest IFs content was obtained by extraction using methanol (MeOH)/water (80:20, v/v) in a 75 ℃ oven for 2 h, and hydrolyzation with 3 M NaOH solution at a room temperature for 10 mins. The total IFs content obtained by the improved method has increased by 16.4% compared with AOAC Official Method 2001.10. The accuracy of the method was evaluated using the relative standard deviation (RSD). Intraday accuracies in the total amount of isoflavones of four samples were 0.03%-0.63% (n = 3). Interday accuracy in the total amount of isoflavones was 2.71% (n = 6). LOD of IFs ranged from 0.1$\mathrm{\mu }$g/mL for aglycones to 0.2$\mathrm{\mu }$g/mL for glucosides. LOQ of IFs ranged from 0.3$\mathrm{\mu }$g/mL for aglycones to 0.5$\mathrm{\mu }$g/mL for glucosides. The improved method was proven to be a more accurate way to determine IFs contents in soybeans and soy protein products and thus making it useful for quality control and systematic in-depth study of soybeans and soy products; even to further assess the dietary soy exposure and the soy-health association.

异黄酮 (IF) 是重要的生物活性化合物，对人类健康有多种益处。尽管IF内容很重要，但现有方法仍然存在一些缺陷。本研究的目的是优化碱解方法的关键参数，以提高大豆和大豆蛋白产品中IFs含量定量分析的可靠性和准确性。溶剂类型、萃取温度、加热模式、碱浓度、水解温度、水解时间和一些细节是目标分析物的关键点，从而产生确定参数。使用甲醇（MeOH）/水（80:20，v/v）在75℃烘箱中提取2小时，并在室温下用3M NaOH溶液水解10分钟获得最大IFs含量。改进方法得到的IFs总含量比AOAC官方方法2001.10提高了16.4%。使用相对标准偏差（RSD）评估该方法的准确性。四个样品异黄酮总量的日内准确度为 0.03%-0.63% (n = 3)。异黄酮总量的日间准确度为 2.71% (n = 6)。 IF 的 LOD 范围为 0.1 g/mL 糖苷配基至 0.2 g/mL 为糖苷。 IF 的 LOQ 范围为 0.3 g/mL 糖苷配基至 0.5 g/mL 为糖苷。 改进后的方法被证明可以更准确地测定大豆和大豆蛋白制品中IFs的含量，从而有助于大豆和豆制品的质量控制和系统深入研究；甚至进一步评估饮食中大豆的摄入量和大豆健康关联。