Research Group of Food Engineering, Faculty of Engineering, National Univ. of Mar del Plata, Buenos Aires, Argentina.
Argentinean Agency for the Scientific and Technological Promotion (ANPCyT), Argentina.
J Food Sci. 2018 Mar;83(3):631-638. doi: 10.1111/1750-3841.13994. Epub 2017 Dec 6.
In this work, a Fourier transform mid-infrared spectroscopy (FTIR)-based method was developed for simultaneously quantifying simple sugars and exogenously added fructooligosaccharides (FOS) in strawberry juices preserved for up to 14 d using nonthermal techniques (geraniol and vanillin+ultrasound). The main spectral differences were observed in the 1200 to 900 cm region. The presence of FOS was identified by the typical bands at 1134, 1034, and 935 cm . During storage, a significant decrease of sucrose was concomitant to an increase of glucose and fructose in juices stored without any previous preservation treatment, as determined by high-performance liquid chromatography (HPLC). A principal component analysis was performed on the FTIR spectra corresponding to the different treatments. The groups observed explained more than 94% of the variance and were related to changes in the carbohydrate composition during storage. Then, different partial least square models (PLS) were defined to determine the concentrations of glucose, sucrose, fructose, and those of exogenously added FOS with degrees of polymerization within 3 and 5. The carbohydrates' concentrations determined by HPLC were used as reference method. The models were validated with independent sets of data. The mean of predicted values fitted nicely those obtained by HPLC (correlation and R > 0.97), thus supporting the use of the PLS models to monitor the quality of strawberry juices in unknown samples. In conclusion, FTIR spectroscopy appears as an adequate analytical tool to quick assess whether juice formulations meet specifications in terms of authenticity, contamination and/or deterioration.
FTIR spectroscopy provided a method potentially transferable to the food industry when associated with the multivariate analysis. The robust 21 PLS models defined in this work provided reliable tools for the rapid monitoring of juices' authenticity and/or deterioration. In this regard, FTIR associated to multivariate analysis enabled the determination of different sugars in a single measurement without the need of pure sugars as standards. This experimental simplicity supports the use of FTIR at the production line, and also contributes to save time in determining carbohydrates' composition and stability, in an environmentally friendly way.
本工作采用傅里叶变换中红外光谱（FTIR）法，结合非热技术（香叶醇和香草醛+超声），开发了一种同时定量草莓汁中简单糖和外源添加的果寡糖（FOS）的方法，草莓汁的保存期长达 14 天。主要光谱差异出现在 1200 至 900 cm 区域。通过在 1134、1034 和 935 cm 处的典型谱带识别出 FOS 的存在。在没有任何先前保存处理的情况下，果汁中蔗糖的显著减少伴随着葡萄糖和果糖的增加，这是通过高效液相色谱（HPLC）确定的。对不同处理对应的 FTIR 光谱进行主成分分析。观察到的组解释了超过 94%的方差，与储存过程中碳水化合物组成的变化有关。然后，定义了不同的偏最小二乘模型（PLS），以确定聚合度为 3 和 5 的葡萄糖、蔗糖、果糖和外源添加 FOS 的浓度。HPLC 确定的碳水化合物浓度用作参考方法。用独立数据集验证模型。预测值的平均值与 HPLC 获得的值拟合良好（相关性和 R ＞0.97），因此支持使用 PLS 模型监测未知样品中草莓汁的质量。总之，FTIR 光谱似乎是一种合适的分析工具，可以快速评估果汁配方在真实性、污染和/或变质方面是否符合规格。
FTIR 光谱与多元分析相结合，为食品工业提供了一种潜在的方法。本工作中定义的 21 个稳健的 PLS 模型为快速监测果汁的真实性和/或变质提供了可靠的工具。在这方面，FTIR 与多元分析相结合，使得在单次测量中能够确定不同的糖，而无需使用纯糖作为标准。这种实验的简单性支持了 FTIR 在生产线中的使用，并且还有助于以环保的方式节省确定碳水化合物组成和稳定性的时间。
