Profiles of Sugar and Organic Acid of Fruit Juices: A Comparative Study and Implication for Authentication

Jiaxiu Li,Zhonggao Jiao,Jiechao Liu,Chunling Zhang,Hui Liu

doi:10.1155/2020/7236534

Jiaxiu Li, Zhonggao Jiao + Show 3 more

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https://doi.org/10.1155/2020/7236534

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Abstract

A comparison of sugar and organic acid profiles among different fruit juices (including apple, pear, peach, grape, sweet cherry, strawberry, and blueberry with various varieties) was performed to assess the possibility for authentication coupled with chemometrics. It was found that the distribution of each sugar and organic acid in juices showed some specific characteristics related to fruit species, despite the fact that great differences in the content existed among different varieties. Sucrose was the most abundant sugar in peach juice, accounting for 58.26–77.11% of the total sugar content. However, in grape, blueberry, and sweet cherry juice, glucose and fructose were the predominant sugars. Pear juice contained the highest level of sorbitol, which contributed to 15.02–43.07% of the total sugar content. Tartaric acid was detected only in grape juice among the seven species of fruit juice, with a proportion of 57.95–89.68% in the total acid content. Malic acid was the predominant organic acid in apple and sweet cherry juice, accounting for 69.92–88.30% and 97.51–98.73% of the total acid content of each species. Citric acid was the predominant organic acid in strawberry and blueberry juice, which contributed to 62.39–83.73% and 73.36–89.56% of the total acid content of each species. With the aid of principal component analysis and linear discriminant analysis (LDA), the juice samples could be successfully classified according to fruit species by using the sugar and/or organic acid composition as analytical data. Combination of sugar and organic acid composition gave the best differentiation of these seven species of juices, with a 100% correct classification rate for both the original and the cross-validation method in LDA. Adding malic/citric into the dataset of the organic acid content may also improve the differentiation effect. Furthermore, the adulteration of sweet cherry juice, blueberry juice, raspberry juice, and grape juice with apple juice, pear juice, or peach juice could also be distinguished from their corresponding pure juices based on sugar and organic acid composition by LDA.

Highlights

Sugars and organic acids are the main nutrients and taste components in fruit juices, which contribute to the main soluble solid content and sensory properties of fruit juices [1, 2]
As the data of sugar composition were subjected to linear discriminant analysis (LDA), the correct classification rate for the original and the cross-validation method achieved 98.8%, in which only one apple juice sample was misclassified in the strawberry juice group. ese results indicate that the combination of sugar and organic acid composition is superior to other datasets which comprise sugar or organic acid composition alone. e combination of different datasets for LDA was performed in differentiation of cherries according to the cultivar, and a more excellent separation of cultivars was achieved as compared with those using an individual dataset of conventional quality parameters, volatile compounds, or minerals [40]
Except for grape juice adulterates with 20% of apple juice and pear juice, all other adulteration of sweet cherry juice, blueberry juice, raspberry juice, and grape juice with the addition of apple juice, pear juice, or peach juice could be distinguished from their corresponding pure juices. ese preliminary results confirm the idea that the sugar and organic acid profiles may be a useful approach for detecting adulteration of higher-cost fruit juices with cheaper alternatives

Summary

Introduction

Sugars and organic acids are the main nutrients and taste components in fruit juices, which contribute to the main soluble solid content and sensory properties of fruit juices [1, 2]. E differentiation of fresh Greek orange juice made from the Merlin cultivar according to the geographical origin was achieved by using linear discriminant analysis based on composition of sugar and organic acid [8]. High-performance liquid chromatography (HPLC) is a popular method for the analysis of food composition due to its high precision and analytical selectivity. It can provide rapid quantitative separation of many components in various food matrices, such as carbohydrates [9], organic acids [10], phenolics [11], and vitamins [12]. Several researches have revealed the compositions of sugars or organic acids in fruit juices by using the HPLC technique owing to its ability to determine and quantify the main sugars and organic acids in fruit juices [8, 13,14,15,16]

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