The current study focuses on the fabrication of a mixed chemical colorimetric pH dye-based indicator to monitor the freshness of ready-to-cook (RTC) idli batter stored under ambient conditions. The base of the indicator label was created using Acetobacter xylinum culture for the fabrication of a bacterial cellulose (BC) membrane film, and the characteristics of the developed film were analysed. Scanning electron microscopy identified the presence of a cellulose fibrils network and Fourier Transform–infrared spectroscopy indicated the presence of an amine group at wavenumber 1642 cm⁻¹ on the developed BC film. Differential scanning calorimetry analysis identified the glass transition, onset, melting and end set melt temperatures as −30.3, 42.2, 85.6 and 105.9°C, respectively, and enthalpy as 209.2 Jg⁻¹. The tensile strength of the developed base layer was found to be low at 27.11 ± 0.05 MPa. The developed base layer was coated with mixed colorimetric pH dyes of bromothymol blue and methyl red in a ratio of 2:3. The fabricated mixed colorimetric indicator label reacted as the carbon dioxide concentrations in the headspace increased from 0.15% ± 0.05% to 17.64% ± 0.11% (v/v) for up to 24 hours, and displayed a colour change of yellow for fresh to reddish orange for spoiled RTC idli batter stored under ambient conditions.

中文翻译：

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开发涂有混合比色指示剂的细菌纤维素膜，用于跟踪即食 idli 面糊的新鲜度/变质

目前的研究重点是制造一种基于混合化学比色 pH 染料的指示剂，以监测在环境条件下储存的即食 (RTC) idli 面糊的新鲜度。使用木醋杆菌培养物制作指示标签的基底，用于制作细菌纤维素（BC）膜膜，并对显影膜的特性进行分析。^{扫描电子显微镜确定了纤维素原纤维网络的存在，傅里叶变换红外光谱表明在波数 1642 cm -1}处存在胺基团在显影的 BC 胶片上。差示扫描量热分析确定玻璃化转变温度、起始温度、熔化温度和最终凝固温度分别为-30.3、42.2、85.6和105.9°C，焓为209.2 Jg ^-1。发现开发的基层的抗拉强度较低，为 27.11 ± 0.05 MPa。显影的基层用溴百里酚蓝和甲基红的混合比色 pH 染料以 2:3 的比例涂覆。当顶部空间中的二氧化碳浓度从 0.15% ± 0.05% 增加到 17.64% ± 0.11% (v/v) 长达 24 小时时，制造的混合比色指示标签会发生反应，并显示从新鲜到微红色的黄色变化橙色表示在环境条件下储存的损坏的 RTC idli 面糊。