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

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.

Chemical Composition of Juices Made from Cultivars and Breeding Selections of European Pear (Pyrus communis L.)

“…No significant differences in total quantified sugar contents were found between apples and pears, whereas the total quantified organic acid contents of pears were significantly lower than those of apples. 16 Pear has been reported to contain the highest amount of sorbitol among certain fruit juices (apple, pear, peach, grape, sweet cherry, strawberry, and blueberry). 16 Aroma compounds also played an important role in affecting overall flavor of pear fruits, which determined the consumer perception and acceptability of the final pear products.…”

Changes in the Content of Organic Acids and Expression Analysis of Citric Acid Accumulation-Related Genes during Fruit Development of Yellow (Passiflora edulis f. flavicarpa) and Purple (Passiflora edulis f. edulis) Passion Fruits

“…Organic acids, being the important constituent of fruit taste along with sugars, strongly influence the organoleptic quality of fruits [4,5]. The sugar-acid ratio is one of the important indicators to measure the flavor and maturation of fruit and is mainly affected by organic acid contents [6][7][8][9]. Many studies have been reported to ascertain compositional changes in passion fruit, and most of these studies have focused on the volatile compounds [10][11][12].…”

Nutritional and flavor properties of grape juice as affected by fermentation with lactic acid bacteria

“…HPLC analysis of soluble sugars in grape juice was performed by using an e2695 HPLC system coupled with a 2414 refractive index detector (Waters Corp., Wilford, MA, USA) according to the method described in a previous research. [30] A Waters Sugar-Pak I column (6.5 × 300 mm) was used to separate the sugars under the temperature of 80°C with EDTA-Na 2 -Ca solution (50 mg/L) as elution solvent. Chromatograms were recorded and compared with those of sucrose, glucose, and fructose standards.…”

“…HPLC analysis of organic acids in grape juices was performed by using an e2695 HPLC system coupled with a 2489 UV/Vis detector (Waters Corp., Wilford, MA, USA) according to the method described in a previous research. [30] A Welch Ultimate AQ-C18 column (4.6 × 250 mm, 5 µm, Welch Science &Technology Co., Ltd, Shanghai, China) was used to separate the organic acids with (NH 4 ) 2 HPO 4 solution (0.02 mol/L, pH 2.4) as elution solvent. Chromatograms were recorded at 210 nm and compared with those of standards.…”