Abstract
Fruit juices are one of the most adulterated beverages, usually because of the addition of water, sugars, or less expensive fruit juices. This study presents a method based on Fourier transform infrared spectroscopy (FT-IR), in combination with machine learning methods, for the correct identification and quantification of adulterants in juices. Thus, three types of 100% squeezed juices (pineapple, orange, and apple) were evaluated and adulterated with grape juice at different percentages (5%, 10%, 15%, 20%, 30%, 40%, and 50%). The results of the exploratory data analysis revealed a clear clustering trend of the samples according to the type of juice analyzed. The supervised learning analysis, based on the development of models for the detection of adulteration, obtained significant results for all tested methods (i.e., support-vector machines or SVM), random forest or RF, and linear discriminant analysis or LDA) with an accuracy above 97% on the test set. Regarding quantification, the best results are obtained with the support vector regression and with partial least square regression showing an R2 greater than 0.99 and a root mean square error (RMSE) less than 1.4 for the test set.
Highlights
One of the largest sectors in the beverage industry is the production of fruit juices
The result obtained indicates a slightly higher potential for the use of the non-parametric method (SVR) in the test set (RMSE = 1.243), the second-best result (RMSE = 1.357) is obtained with a parametric approach (PLS). These results suggest that in the Fourier transform infrared spectroscopy (FT-IR) spectroscopic data of juice samples none of the strategies is superior to the other
FT-IR spectroscopy, combined with suitable machine learning methods, has been empirically proven to be a reliable analytical technique for the detection and quantification of grape juice used as an adulterant in other juices
Summary
One of the largest sectors in the beverage industry is the production of fruit juices. In Europe, there is strict regulation to guarantee the quality and origin in the manufacture of juices established by the 2012/12 EU directive [4] This directive describes that fruit juices must be 100% squeezed from healthy and ripe fruits where the addition of sugars is not allowed. It is important to be aware that adding other fruit juices and not informing the consumer entails an additional risk of allergic reactions [8]. It is food fraud for economic benefits, which could affect the health of the consumer [9]
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