Natural colorimetric indicators have been fabricated using annatto and pomegranate extract powder and compared with chemical colorimetric indicator fabricated using bromophenol blue (BPB) to monitor the freshness of ready‐to‐cook (RTC) idli batter. The fabricated colorimetric indicator labels work on increasing headspace carbon dioxide (CO₂) concentration and decreasing pH of stored batter, where indicators showed visible color change from lightest to darkest for spoiled samples. The headspace CO₂ concentration of RTC idli batter increased from 0.15 ± 0.05 to 18.07 ± 0.21% (v/v) and pH decreased from 6.7 ± 0.06 to 4.5 ± 0.06 at optimum storage condition (35 ± 1°C) up to 24 h. The percent titratable acidity (% TA) increased from 0.44 ± 0.02 to 0.90 ± 0.02% up to 24 h. The viable lactic acid bacteria count (LABC) and total bacterial count (TBC) increased while yeast and mold count (YMC) was decreased with increasing fermentation time up to 24 h for batter stored at optimum condition. The color change of indicators was quantitatively measured with captured red, green, and blue (RGB) images. Pixel intensity for natural and chemical colorimetric indicators were decreased with increasing fermentation time. The leaching of chemical dye was observed on stored batter, and natural colorimetric indicators are nontoxic and successfully used as “on package sticker” for monitoring freshness of RTC idli batter.

中文翻译：

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天然比色指示剂的制造，用于监控即煮型面团的新鲜度

天然比色指示剂是使用安纳托和石榴提取物粉末制成的，与使用溴酚蓝（BPB）制造的化学比色指示剂进行了比较，以监控即煮（RTC）面团的新鲜度。制成的比色指示剂标签可提高顶空二氧化碳（CO ₂）的浓度并降低储存的面糊的pH，其中指示剂显示变色样品的可见颜色从最亮变为最暗。顶空CO ₂在最佳储存条件下（35±1°C）长达24小时，RTC电池的浓度从0.15±0.05增加到18.07±0.21％（v / v），pH从6.7±0.06减小到4.5±0.06。在24小时内，可滴定酸度百分比（％TA）从0.44±0.02增加到0.90±0.02％。对于在最佳条件下储存的面糊来说，随着发酵时间的延长，存活的乳酸菌数量（LABC）和总细菌数量（TBC）会增加，而酵母菌和霉菌数量（YMC）则会降低，直至最多24小时。使用捕获的红色，绿色和蓝色（RGB）图像定量测量指示器的颜色变化。天然和化学比色指示剂的像素强度随发酵时间的增加而降低。在储存的面糊中观察到化学染料的浸出，