da Silva Gabriela Fioravante, Botelho Bruno Gonçalves
Chemistry Department, ICEx, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
J Food Sci. 2025 Aug;90(8):e70433. doi: 10.1111/1750-3841.70433.
The growth of the global kombucha market highlights the importance of quality control in production, a crucial factor to ensure consumer safety, regulatory compliance, and product consistency. This study aimed to develop and validate rapid, direct multivariate methods based on Fourier transform infrared (FTIR) spectroscopy combined with partial least squares (PLS) regression to simultaneously quantify alcohol content and acidity. The method requires minimal sample preparation, with no need for extraction or derivatization, allowing spectral acquisition in about 30 s-ideal for high-throughput analysis and aligned with green chemistry principles. Infrared spectra were recorded in the range of 4000-650 cm⁻¹. Reference values were obtained by gas chromatography with flame ionization detection (GC-FID), following validated protocols. Thirty kombucha brands from different regions of Brazil were analyzed, all labeled with an alcohol content of up to 0.5% v/v. However, 60% of the samples exceeded this limit, with levels ranging from 0.10% to 1.70% v/v. Acidity ranged from 17 to 71 mEq/L, with only 50% of the samples meeting the recommended specifications (30-130 mEq/L). The PLS model showed RMSEC and RMSEP values of 0.09% and 0.07% v/v for alcohol, and 3.2 and 3.9 mEq/L for acidity, respectively. Metrics such as precision, bias, and RPD > 2.4 confirmed the robustness of the models. The results reveal discrepancies between declared and measured values, especially for alcohol content, emphasizing the need for stricter regulatory oversight. The method is reliable, efficient, and suitable for routine analyses and regulatory monitoring. PRACTICAL APPLICATIONS: The FTIR-PLS method developed in this study offers a rapid, accurate, and environmentally friendly alternative for routine monitoring of alcohol content and acidity in kombucha. Its application facilitates verification of regulatory compliance and strengthens quality control in the beverage industry, contributing to consumer safety. Moreover, the method can be adopted by regulatory agencies and producers to ensure the conformity of products available on the market.
全球康普茶市场的增长凸显了生产过程中质量控制的重要性，这是确保消费者安全、符合监管要求以及产品一致性的关键因素。本研究旨在开发并验证基于傅里叶变换红外（FTIR）光谱结合偏最小二乘法（PLS）回归的快速、直接多变量方法，以同时定量酒精含量和酸度。该方法所需的样品制备最少，无需萃取或衍生化，大约30秒即可完成光谱采集，非常适合高通量分析，并且符合绿色化学原则。红外光谱在4000 - 650 cm⁻¹范围内记录。参考值通过气相色谱 - 火焰离子化检测（GC - FID）按照经过验证的方案获得。对来自巴西不同地区的30个康普茶品牌进行了分析，所有品牌标注的酒精含量最高为0.5% v/v。然而，60%的样品超过了这个限制，含量范围为0.10%至1.70% v/v。酸度范围为17至71 mEq/L，只有50%的样品符合推荐规格（30 - 130 mEq/L）。PLS模型显示酒精含量的RMSEC和RMSEP值分别为0.09%和0.07% v/v，酸度的RMSEC和RMSEP值分别为3.2和3.9 mEq/L。精密度、偏差和RPD > 2.4等指标证实了模型的稳健性。结果揭示了宣称值与测量值之间的差异，特别是酒精含量方面，强调了加强监管监督的必要性。该方法可靠、高效，适用于常规分析和监管监测。实际应用：本研究开发的FTIR - PLS方法为康普茶中酒精含量和酸度的常规监测提供了一种快速、准确且环保的替代方法。其应用有助于验证法规合规性并加强饮料行业的质量控制，保障消费者安全。此外，监管机构和生产商可以采用该方法确保市场上产品的合规性。
