褐变指数(BI,ABS520nm/ABS420nm)是富含花青素的果汁色素沉着质量的量度。这项研究试图确定BI描述果汁中花色苷质量和降解的程度。测定了商业果汁的单体花青素(MA)含量,聚合物颜色百分比(%PC),pH值,还有BI。BI多种多样,0.29到1.72,在蔓越莓中,樱桃,葡萄,aronia,还有石榴汁.主成分分析(PCA)显示,BI与%PC呈强烈负相关,与MA的正相关程度较小。在pH调节的果汁中,葡萄汁和樱桃汁的BI随pH从2.0到4.0线性变化。将pH约2.0至4.0的樱桃汁和葡萄汁在50°C下孵育以诱导汁褐变。BI和MA下降,和%PC增加,但MA降解量不能用%PC解释。在陈年的果汁中,使用PCA,BI和MA密切相关。在陈年的葡萄汁中,色谱分析用于表征花色苷,原花青素,和花青素分裂产品。花青素的损失和在420nm处吸收的未解决成分的增加降低了BI。原花青素和具有不同BI的共洗脱颜料在老化过程中降低。切割产品没有考虑花青素的损失。因此,在葡萄汁加速老化过程中,MA损失比与果汁原花青素相关的色素增加更多,这有助于增加%PC和降低BI。因此,BI是相同pH和花色苷组成的果汁中果汁质量的有用标记。
■果汁色素沉着取决于花青素,pH值,和其他矩阵组件。测定色素沉着的分光光度法包括褐变指数(ABS520nm/ABS420nm),单体花色苷(MA)含量的pH差分法,和亚硫酸氢盐漂白以测定聚合物颜色百分比(%PC)。在这项研究中,富含花青素的果汁褐变指数强烈依赖于pH和MA含量。MA损失,在较小程度上,在420nm处新形成的颜料的增加导致了老化过程中褐变指数的变化。因此,褐变指数与MA含量密切相关,可用于评估果汁质量。
Browning index (BI, ABS520 nm /ABS420 nm ) is a measure of anthocyanin-rich fruit juice pigmentation quality. This study sought to determine the extent to which BI describes anthocyanin quality and degradation in fruit juices. Commercial fruit juices were assayed for monomeric anthocyanin (MA) content, percent polymeric color (%PC), pH, and BI. BI varied, 0.29 to 1.72, among cranberry, cherry, grape, aronia, and pomegranate juices. Principal component analysis (PCA) revealed that BI was strongly inversely associated with %PC, and positively correlated with MAs to a lesser extent. The BI of grape and cherry juices varied linearly with pH from 2.0 to 4.0 in pH-adjusted juices. Cherry and grape juices at pH approximately 2.0 to 4.0 were incubated at 50 °C to induce juice browning. BI and MA decreased, and %PC increased, but the amount of MA degradation was not explained by %PC. In the aged juices, BI and MA were strongly correlated using PCA. In aged grape juice, chromatographic analysis was used characterize anthocyanins, proanthocyanidins, and anthocyanin scission products. Anthocyanin loss and a gain of unresolved components absorbing at 420 nm decreased BI. Proanthocyanidins and co-eluting pigments with varying BI decreased during aging. Scission products did not account for anthocyanin loss. Thus, MA loss more so than the gain in pigments associated with juice proanthocyanidins contribute to the increase in %PC and decline of the BI during accelerated aging of grape juice. Thus, BI is a useful marker of fruit juice quality within juices of the same pH and anthocyanin composition.
UNASSIGNED: Fruit juice pigmentation depends on anthocyanins, pH, and other matrix components. Spectrophotometric methods to determine pigmentation include the browning index (ABS520 nm /ABS420 nm ), pH differential method for monomeric anthocyanin (MA) content, and bisulfite bleaching to determine percent polymeric color (%PC). In this study, anthocyanin-rich fruit juice browning index was strongly dependent on pH and MA content. MA loss, and to a lesser extent, a gain in newly-formed pigments at 420 nm contributed to the browning index change during aging. Therefore, browning index is strongly associated with MA content and is useful for assessing fruit juice quality.