Optimization of deacidification for concentrated grape juice

Analysis of untargeted metabolites of natural ingredient spine grape (Vitis davidii Foex) juices and provides new insights into biological activities

BACKGROUND

Consumer demand for natural products is driving innovation in clean label ingredients. Spine grape (Vitis davidii Foex), a wild East Asian species, and its fresh juice show great promise as versatile ingredients because of their rich composition. The present study assessed the physicochemical properties and metabolite profiles of fresh juices from four spine grape cultivars, exploring their application.

RESULTS

The physicochemical properties of spine grape juices highly depended on the cultivar. Total soluble solids ranged from 12.43% to 14.27%, whereas organic acid content varied between 5.35 and 6.85 g L-1. The phenolic content ranged from 520.17 to 611.68 mg L-1, and the anthocyanin content fluctuated from 72.70 to 155.54 mg L-1. Metabolite identification using ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry revealed a total of 116 compounds, including flavonoids, phenolic acids, stilbenes, coumarins, amino acids, peptides, lipids and vitamins. Among these, 68 compounds including well-known phenolics and 11 bioactive peptides that are less extensively researched, contributed to the biofunctions of spine grape juices. The white juice 'Baci' exhibited the highest levels of bioactive compounds, including catechin, procyanidines, resveratrol and antioxidant peptides. This resulted in a significantly higher DPPH (i.e. 2,2-diphenyl-1-picrylhydrazyl) value (8481.78 μmol Trolox equivalents L-1) compared to other red spine grape juices.

CONCLUSION

This study provides comprehensive insights into spine grape juices, offering valuable guidance for commercial applications. The 'Tianci' and 'Ziqiu' red grape juices stand out as ideal sensory ingredients because of their favorable physicochemical properties, whereas the 'Baici' white spine grape juice, which contains higher levels of bioactive compounds, emerges as a promising functional ingredient. © 2025 Society of Chemical Industry.

Research Progress on Methods for the Deacidification of Small Berry Juice: An Overview

As some of the richest sources of natural antioxidants, small berry fruits have attractive colors and special tastes, with recognized benefits for human health. However, sour tastes in small berry juices result in a poor flavor and low acceptance among consumers, greatly limiting their marketability. Among the most commonly used deacidification methods, chemical deacidification methods can neutralize fruit juice via the addition of a deacidification agent, while physical deacidification methods include freezing deacidification, ion-exchange resin deacidification, electrodialysis deacidification, and chitosan deacidification. All of these methods can markedly improve the pH of fruit juice, but they introduce new substances into the juice that may have an influence on its color, taste, and stability. Biological deacidification can effectively remove malic acid from fruit juice, reducing the content from 15 g/L to 3 g/L; additionally, it maintains the taste and stability of the juice. Therefore, it is widely applied for fruit juice deacidification. On this basis, some compound deacidification technologies have also emerged, but they also present problems such as high costs and complicated working procedures. This review of deacidification methods for small berry juice provides a foundation for the industrial development of such juices.

Electrodialysis Desalination with Simultaneous pH Adjustment Using Bilayer and Bipolar Membranes, Modeling and Experiment

A kinetic model of the bipolar electrodialysis process with a two-chamber unit cell formed by a bilayer (bipolar or asymmetric bipolar) and cation-exchange membrane is proposed. The model allows describing various processes: pH adjustment of strong electrolyte solutions, the conversion of a salt of a weak acid, pH adjustment of a mixture of strong and weak electrolytes. The model considers the non-ideal selectivity of the bilayer membrane, as well as the competitive transfer of cations (hydrogen and sodium ions) through the cation-exchange membrane. Analytical expressions are obtained that describe the kinetic dependences of pH and concentration of ionic components in the desalination (acidification) compartment for various cases. Comparison of experimental data with calculations results show a good qualitative and, in some cases, quantitative agreement between experimental and calculated data. The model can be used to predict the performance of small bipolar membrane electrodialysis modules designed for pH adjustment processes.

Changes in quality parameters of orange juice deacidified by ion exchange resins

In this study, the effectiveness of five different ion exchange resins (Amberlite-IRA96,-FPA51,-FPA53,-FPA54 and Lewatit-S4528) in reducing the acidity of Valencia orange juice and effects on juice quality were determined. The greatest decrease in titratable acidity (65%) and increase (23%) in pH were determined in the juices deacidified using Amberlite-FPA51. The greatest color change (ΔE*=4.89) was identified by treatment of Lewatit-S4528. Ascorbic acid contents were decreased between 12 and 28% by deacidification. Changes ((-4.43)-(+8.18)%) in the carotenoid contents were also assessed in juices treated with different resins. The changes in amount of hydroxycinnamic, hydroxybenzoic acids, flavanones, flavonol and flavone were determined. The largest decrease (ca.28%) in total phenolics was observed with Amberlite-FPA54. The most abundant organic acids in juices were citric acid followed by quinic, malic, ascorbic, tartaric, succinic and oxalic acid, which were decreased after deacidification. Lowest color change and highest carotenoid content were obtained with Amberlite-FPA54.

Effects of leaf removal on hexose accumulation and the expression of sugar unloading-related genes in syrah grapes

Leaf removal (LR) around the cluster zone is a common practice for regulating grape quality. The purpose of this study was to assess the effects of cluster-zone leaf removal, applied at the pea-size stage of berry development, on berry soluble sugar, organic acid and phenolic compound, sugar unloading-related gene expression of Vitis. vinifera L. Syrah. Four different severities of leaf removal were applied: no leaf removal (Control), removing 2 leaves above the cluster (LR1), removing 4 leaves above the cluster (LR2), and removing 6 leaves above the cluster (LR3). The three leaf removal treatments (LR), especially removing 4 leaves (LR2), resulted in significantly higher reducing sugar, soluble sugar (glucose, fructose and sucrose), total anthocyanin and citric acid contents as compared to the control group during ripening for both vintages. At harvest, the LR treatments increased the transcript abundance of most sugar unloading-related genes. In addition, VvHT3, VvHT5, VvSUC11, VvSUC12, VvSS and VvcwINV were positively correlated with both reducing sugar contents and soluble sugar contents. Our results suggest that removing 4 leaves above the cluster is useful for improving the quality of Syrah (Vitis vinifera L.) grapes in cool climate regions with excessive leaves. These findings provide insights into the molecular basis of the relationship between leaf removing and hexose (glucose and fructose) accumulation in the grape berries.

Optimization of debittering and deacidification parameters for Pomelo juice and assessment of juice quality

Bitterness and tartness are one of the crucial reasons for the poor commerciality of Pomelo fruits. The present study intends to optimize the process variables such as resin concentration (Amberlite IRA-400) (3-10 g), time exposure (10-60 s), and stirring speed (300-1000 rpm) for removal of naringin content and tartness using response surface methodology. All the independent variables have shown a significant effect on naringin content, titrable acidity, and vitamin C content of pomelo juice. The optimized process variables for debittering and deacidification were 3.27 g resin concentration, 60 s time and 1000 rpm stirring speed, and the naringin content and titrable acidity at these optimized conditions were 0.22 mg ml^-1 and 0.64% citric acid equivalent respectively. The treated juice under optimum conditions was analyzed for physicochemical properties where pH, clarity, and L* value of juice increased. In contrast, total soluble solids, vitamin C content, and a* value decreased slightly. The finding of present investigation will be helpful to improve the commercial acceptability of the sour variety of citrus fruit juice.

Whole, concentrated and reconstituted grape juice: Impact of processes on phenolic composition, "foxy" aromas, organic acids, sugars and antioxidant capacity

The concentration and reconstitution processes of grape juices can result in losing compounds associated with beverage quality. In this context, three tanks containing 50,000 L of grape juice were individually concentrated up to 68 °Brix using a triple vacuum concentrator. The concentrated juice was reconstituted up to the original °Brix of the whole juice (18.4). Phenolic compounds, sugars and organic acids were quantified by high-performance-liquid-chromatography. "Foxy" aromatic compounds were also quantified by gas-chromatography/mass-spectrometry. The concentration and reconstitution process resulted in significant losses (Tukey test, p < 0.01) of trans-caftaric acid, decreasing from 397.08 to 159.14 mg/L, chlorogenic-acid from 34.97 to 8.44 mg/L, aromatic furaneol compound from 9.06 to 1.93 mg/L, as well as total losses for gallic-acid, caffeic-acid, p-coumaric-acid, syringic-acid, hesperidin, pelargonidin-3-glucoside and epicatechin compounds. The concentration and reconstitution of grape juice preserved the antioxidant capacity and most of the quantified compounds, with the reconstituted juice having good nutritional quality.