Quality evaluation of grape juice concentrated by reverse osmosis

Method for Glucose and Fructose Quantitation in Beverages Using an Off-the-Shelf Glucose Test Strip

A method was developed for quantifying both glucose and fructose in solutions and grape juice using commercially available glucose test strips connected to a mini-potentiostat. The first step of this sensing approach involved exposing the sample solution to an Accu Chek Aviva glucose test strip, which allowed for the direct quantitation of glucose. To quantify fructose, the solution was exposed to glucose isomerase, which led to the conversion of glucose to fructose and vice versa until an equilibrium was reached. Once equilibrium was reached, the solution was exposed to another glucose test strip; the signal obtained was shown to be related to the total amounts of glucose and fructose in solution. Finally, fructose was quantified by subtracting the glucose concentration (from the initial measurement) from the total concentration of glucose and fructose (from the second measurement after the reaction with glucose isomerase). The method yielded a limit of detection of 0.047 g L-1 for glucose and 0.49 g L-1 for fructose. Importantly, this method was shown to work well for analyzing glucose and fructose concentration in grape juice, which contains >60 g L-1 glucose and fructose. Since the ratio of glucose and fructose concentration in ripe grapes is close to 1, this method can be used to aid in the determination of grape ripeness to guide harvesting times.

Influence of the Processing Parameters on the Aroma Profile and Chemical Composition of Conventional and Ecological Cabernet Sauvignon Red Wines during Concentration by Reverse Osmosis

Wine aroma represents one of the most important quality parameters and it is influenced by various factors, such as climate conditions, viticulture and vinification techniques, storage conditions, etc. Wines produced from conventionally and ecologically grown grapes of the same variety have different chemical compositions and aroma profiles. The composition of wine can also be influenced by the additional treatment of wine, such as the concentration of wine by reverse osmosis (RO). The aim of this study was to investigate the influence of four different pressures (2.5, 3.5, 4.5 and 5.5 MPa) and two temperature regimes (with and without cooling) on the aroma profile and chemical composition of conventional and ecological Cabernet Sauvignon red wine during concentration by reverse osmosis. The results showed that different processing parameters influenced the permeate flux, the retentate temperature and the compounds retention. Higher working pressures (4.5 and 5.5 MPa) and the regime, with cooling, resulted in a higher retention of the total aroma compounds than the opposite processing parameters. The retention of individual compounds depended also on their chemical properties and their interactions with the membrane surface. The reverse osmosis membranes proved to be permeable for ethanol, acetic acid or undesirable 4-ethylphenol and 4-ethylguaiacol that made them applicable for their correction or removal.

Influence of Reverse Osmosis Process in Different Operating Conditions on Phenolic Profile and Antioxidant Activity of Conventional and Ecological Cabernet Sauvignon Red Wine

Red wine polyphenols are responsible for its colour, astringency, and bitterness. They are known as strong antioxidants that protect the human body from the harmful effects of free radicals and prevent various diseases. Wine phenolics are influenced by viticulture methods and vinification techniques, and therefore, conventionally and ecologically produced wines of the same variety do not have the same phenolic profile. Ecological viticulture avoids the use of chemical adjuvants in vineyards in order to minimise their negative influence on the environment, wine, and human health. The phenolic profile and antioxidant activity of wine can also be influenced by additional treatments, such as concentration by reverse osmosis. The aim of this study was to investigate the influence of four different pressures (2.5, 3.5, 4.5, and 5.5 MPa) and two temperature regimes (with and without cooling) on the phenolic profile and antioxidant activity of conventional and ecological Cabernet Sauvignon red wine during concentration by reverse osmosis. The results showed that retention of individual phenolic compounds depended on the applied processing parameters, chemical composition of the initial wine, and chemical properties of a compound. Higher pressure and retentate cooling favoured the retention of total polyphenols, flavonoids, and monomeric anthocyanins, compared to the opposite conditions. The same trend was observed for antioxidant activity.

Blueberry juice: Bioactive compounds, health impact, and concentration technologies-A review

Blueberries are a popular fruit with an attractive flavor and color, as well as health benefits. These health benefits have been attributed to the important number of bioactive compounds in blueberries with activities such as antioxidant, antitumor, antimutagenic, and antidiabetic effects and the prevention of cardiovascular diseases. Despite these advantages, blueberries are only obtained fresh in certain seasons; therefore, the food and beverage industry transforms them into jelly, puree, or juice. However, the concentration process could help preserve the bioactive compounds of blueberry byproducts. Concentration technologies focus on the removal of excess water to increase the product stability and reduce storage and transportation costs by causing them to take up less space or as a pretreatment before dehydration. These technologies include evaporation, reverse osmosis, and freeze concentration, and each one has different effects on the efficiency, quality, and nutritional value of the final concentrates. However, freeze concentration and reverse osmosis produce a higher-final quality concentrate than evaporation due to the use of low temperatures, which prevents the loss of thermolabile components such as bioactive compounds. Therefore, this review summarizes the impact of concentration technologies on the bioactive compounds and health benefits of blueberry juice.

The chemical composition of two kinds of grape juice with medicinal plant addition

The safety of plant-based food with an herbal origin is a priority for producers and final consumers these days. The interest in the high biological value of the final food products enriched with herbal ingredients is rising. We focused on the study of physico-chemical composition and antioxidant activity of two kinds of grape juice with medicinal plant addition in our study. We used 2 varieties of grapes - Welschriesling and Cabernet Sauvignon, six species of medicinal plants - Calendula officinalis L., Ginkgo biloba, Thymus serpyllum, Matricaria recutita, Salvia officinalis L., and Mentha aquatica var. citrata in our experiment. There were14 samples prepared, two of them were control samples and 12 samples were treated with medicinal plants. We tested each of the selected parameters triplicate with an interval of one week. We evaluated the results statistically in 4 levels of significance p <0,01, p <0,001, p <0,0001 and p <0,00001. The content of fructose, glucose, dry matter, density, malic acid, pH, potential alcohol, total acids, and total sugars in the treated samples was significantly lower compared to the control sample, which was probably due to the degree of dilution of grape juice with extracts gained from medicinal plants. The antioxidant effect was demonstrably higher in the samples enriched with medicinal plants than in the control samples. The highest antioxidant effect was measured in the second test in the samples with the addition of Thymus serpyllum (80.93 % - white grape must, 82.33 % - blue grape must), Calendula officinalis L. (79.29 % - white grape must, 80.49 % - blue grape must) and Ginkgo biloba (79.10 % - white grape must, 83.3 % - blue grape must). Generally, we found out that the selected medicinal plants increase the biological quality of grape juice.

Evaluation of Biochemical Juice Attributes and Color-Related Traits in Muscadine Grape Population

Biochemical juice attributes and color-related traits of muscadine grape genotypes have been investigated. For this study, 90 muscadine genotypes, including 21 standard cultivars, 60 breeding lines, and 9 Vitis x Muscadinia hybrids (VM), were evaluated. The biochemical properties of total soluble solids (TSS), titratable acidity, and TSS/Acid (T/A) ratio showed modest diversity among genotypes with a range of 10.3 °Brix, 2.1 mg tartaric acid/L, and 4.6, respectively. Nonetheless, the pH trait exhibited a tight range of 0.74 among the population with a minimum and maximum pH of 3.11 ± 0.12 and 3.85 ± 0.12. Color-related traits showed more deviation between individuals. Total anthocyanin content (TAC), luminosity index (L*), hue angle (h°), and chroma index (C*) displayed a range of 398 µg/g DW, 33.2, 352.1, and 24, respectively. The hierarchical clustering map classified the population into two large groups of colored and non-colored grapes based on L* and h°, suggesting the predominance of these two characters among the population. The colored berries genotypes clade was further divided into several sub-clades depending on C*, TAC, and TSS levels. The principal component analysis (PCA) separated the four-color characteristics into two groups with a negative correlation between them, L* and C* versus TAC and h°. Further, PCA suggested the positive influence of acidity in enhancing the different nutraceutical components. Despite the nature of anthocyanins as a member of phenolic compounds, a lack of significant correlation between TAC and nutraceutical-related traits was detected. The dissimilatory matrix analysis highlighted the muscadine individuals C11-2-2, E16-9-1, O21-13-1, and Noble as particular genotypes among the population due to enhanced color characteristics.

Concentration with Nanofiltration of Red Wine Cabernet Sauvignon Produced from Conventionally and Ecologically Grown Grapes: Effect on Phenolic Compounds and Antioxidant Activity

The aim of this study was to investigate the influence of different operating conditions (four pressures: 2.5, 3.5, 4.5 and 5.5 MPa; two temperature regimes: with and without cooling) and wine type on phenolic compounds retention during the nanofiltration process of two Cabernet Sauvignon red wines (conventionally and ecologically produced). The nanofiltration process was conducted on Alfa Laval LabUnit M20 with plate module and six NF M20 membranes. In initial wines and obtained retentates, total polyphenol and flavonoid contents, monomeric anthocyanins content, antioxidant activity, individual phenolic compounds and CIELab colour parameters were determined. A loss of total phenolic compounds and decrease in antioxidant activity was observed in all retentates comparing to initial wine. However, retentate cooling and higher pressure increased their retention. Besides processing parameters, individual phenolic compound retention depended on several factors, such as the wine type, chemical properties of compounds and membrane type, and their combinations. Different chemical composition of initial conventional and ecological wine influenced the retention of individual compounds.

Concentration with Nanofiltration of Red Wine Cabernet Sauvignon Produced from Conventionally and Ecologically Grown Grapes: Effect on Volatile Compounds and Chemical Composition

Ecological viticulture represent an upward trend in many countries. Unlike conventional viticulture, it avoids the use of chemical fertilizers and other additives, minimizing the impact of chemicals on the environment and human health. The aim of this study was to investigate the influence of nanofiltration (NF) process on volatiles and chemical composition of conventional and ecological Cabernet Sauvignon red wine. The NF process was conducted on laboratory Alfa Laval LabUnit M20 (De Danske Sukkerfabrikker, Nakskov, Denmark) equipped with six NF M20 membranes in a plate module, at two temperature regimes, with and without cooling and four pressures (2.5, 3.5, 4.5 and 5.5 MPa). Different processing parameters significantly influenced the permeate flux which increased when higher pressure was applied. In initial wines and obtained retentates, volatile compounds, chemical composition and elements concentration were determined. The results showed that the higher pressure and retentate cooling was more favourable for total volatiles retention than lower pressure and higher temperature. Individual compound retention depended on its chemical properties, applied processing parameters and wine composition. Nanofiltration process resulted in lower concentrations of ethanol, acetic acid (>50%), 4-ethylphenol and 4-ethylguaiacol (>90%). Different composition of initial feed (conventional and ecological wine) had an important impact on retention of elements.

Influence of Processing Parameters on Phenolic Compounds and Color of Cabernet Sauvignon Red Wine Concentrates Obtained by Reverse Osmosis and Nanofiltration

In this study, Cabernet Sauvignon red wine was subjected to reverse osmosis and nanofiltration processes at four different pressures (25, 35, 45, and 55 bar) and two temperature regimes (with and without cooling). The aim was to obtain concentrates with a higher content of phenolic compounds and antioxidant activity and to determine the influence of two membrane types (Alfa Laval RO98pHt M20 for reverse osmosis and NF M20 for nanofiltration) and different operating conditions on phenolics retention. Total polyphenol, flavonoid, monomeric anthocyanin contents, and antioxidant activity were determined spectrophotometrically. Flavan-3-ols and phenolic acids were analyzed on a high-performance liquid chromatography system and sample colour was measured by chromometer. The results showed that the increase in applied pressure and decrease in retentate temperature were favorable for higher phenolics retention. Retention of individual compounds depended on their chemical structure, membrane properties, membrane fouling, and operating conditions. Both types of membranes proved to be suitable for Cabernet Sauvignon red wine concentration. In all retentates, phenolic compounds content was higher than in the initial wine, but no visible color change (ΔE* < 1) was observed. The highest concentrations of phenolic compounds were detected in retentates obtained at 45 and 55 bar, especially with cooling.

Integral use of Isabel grapes to elaborate new products with nutritional value and functional potential

Abstract The benefits of grape consumption are widely recognized and mostly due to phenolic compounds. These beneficial effects will depend on the bioaccessibility of these compounds on grape and its derivatives. This study elaborated two formulations of Isabel grape preparation: PAX (with agave and xylitol) and PS (with sucrose); and two formulations of Isabel grape flour: FAX (from the PAX process residues) and the FS (from the PS process residues). The products were analyzed regarding their nutritional and antioxidant properties; their phenolic compounds’ bioaccessibility was also verified through a simulated digestion model. The preparation and flour exhibited relevant sugars levels (10.83-49.71 g 100 g-1). Those produced with natural sweeteners had a reduction in sugar concentration of 51% and 29% for preparation and flour, respectively, compared to formulations with sucrose, with the high fiber content in the flour is being further highlighted (20.14-21.95 g 100 g-1). The catechin (2.37-28.11 mg 100 g-1) was the most bioaccessible compound (22% to 168%), which together with the caftaric acid (2.31-69.43 mg 100 g-1) and malvidin 3-glucoside (8.65-16.47 mg 100 g-1) represent the compounds observed in greater quantity. The preparations showed higher bioaccessibility regarding grapes and flours for most of the phenolic compounds. Furthermore, the products elaborated presented higher values of anthocyanins and antioxidant activity than the in natura grape, highlighting the beneficial effect of grape processing.

Improving quality and quantity attributes of grape juice concentrate (molasses) using ohmic heating

The effect of ohmic heating method (OHM) on quality and quantity attributes of black grape molasses was investigated and compared with the conventional heating method (CHM). Results showed that the samples prepared by OHM had the highest antioxidant activity than CHM. Increasing of voltage gradient had a positive effect on the saving of antioxidant activity. Changes in pH for OHM were lower than CHM. Heating methods had no significant effect on phenol content. Antioxidant capacity and phenol content of treated samples were lower than the fresh sample at the same water content. The titratable acidity of treated samples using CHM was higher than the OHM. The OHM saved about 2.4-7.2-fold of processing time and 6.3-fold of energy consumption than the CHM. Heat generation and electrical conductivity depended on sample moisture content. OHM provides minimal damage to the sensory characteristics. As a final result, the OHM significantly improved the quality and saved the quantity parameters of the grape molasses processing than the CHM.

Combined Osmotic and Membrane Distillation for Concentration of Anthocyanin from Muscadine Pomace

Bioactive anthocyanins from aqueous extracts of muscadine grape pomace were concentrated using osmotic distillation (OD) and direct contact membrane distillation (DCMD) using polypropylene (PP) and poly(ethylene chlorotrifluoroethylene) (ECTFE) membranes. The driving force for OD is created by using a high concentration brine solution while the driving force for DCMD is generated by elevating the feed temperature relative to the permeate temperature. The brine concentration used was 4 M. The lowest fluxes were obtained for OD. Given the temperature sensitive nature of anthocyanins, the maximum temperature difference during DCMD was limited to 30 °C. The feed temperature was 40 °C and the permeate at 10 °C. Consequently, the maximum flux during DCMD was also limited. A combination of OD and DCMD was found to give the highest fluxes. High-performance liquid chromatography (HPLC) and HPLC-electrospray mass spectrometry were used to identify and quantify anthocyanins, cyanidin-3,5-O-diglucoside, delphinidin-3,5-O-diglucoside, petunidin-3,5-O-diglucoside, peonidin-3,5-O-diglucoside, and malvidin-3,5-O-diglucoside. The results obtained here suggest that, though water fluxes for DI water feed streams for PP and ECTFE membrane were similar, the fluxes obtained for the two membranes when using muscadine pomace extracts were different. Concentration factors of close to 3 was obtained for anthocyanins. Membranes also showed slightly different performance in the concentration process. Membrane surfaces were analyzed using scanning electron microscopy and Fourier-transformed infrared spectroscopy. The results suggest that adsorption of these anthocyanins on the membrane surface lead to performance differences. In an actual operation, selection of an appropriate membrane and regeneration of the membrane will be important for optimized performance. PRACTICAL APPLICATIONS: Anthocyanins are valuable therapeutic compounds, which are found in the solid residue left following fruit juice pressing. However, recovery and concentration of these therapeutic compounds remains challenging due to their stability. Here, a novel membrane-based unit operation has been investigated in order to concentrate the anthocyanins that have been extracted into aqueous solutions. The unit operation investigated here use mild processing conditions. Insights into the factors that need to be considered when optimizing of the unit operation for commercialization are discussed.

Recovery of Anthocyanins Using Membrane Technologies: A Review

Anthocyanins are naturally occurring polyphenolic compounds and give many flowers, fruits and vegetable their orange, red, purple and blue colors. Besides their color attributes, anthocyanins have received much attention in recent years due to the growing evidence of their antioxidant capacity and health benefits on humans. However, these compounds usually occur in low concentrations in mixtures of complex matrices, and therefore large-scale harvesting is needed to obtain sufficient amounts for their practical usage. Effective fractionation or separation technologies are therefore essential for the screening and production of these bioactive compounds. In this context, membrane technologies have become popular due to their operational simplicity, the capacity to achieve good simultaneous separation/pre-concentration and matrix reduction with lower temperature and lower operating cost in comparison to other sample preparation methods. Membrane fractionation is based on the molecular or particle sizes (pressure-driven processes), on their charge (electrically driven processes) or are dependent on both size and charge. Other non-pressure-driven membrane processes (osmotic pressure and vapor pressure-driven) have been developed in recent years and employed as alternatives for the separation or fractionation of bioactive compounds at ambient conditions without product deterioration. These technologies are applied either individually or in combination as an integrated membrane system to meet the different requirements for the separation of bioactive compounds. The first section of this review examines the basic principles of membrane processes, including the different types of membranes, their structure, morphology and geometry. The most frequently used techniques are also discussed. Last, the specific application of these technologies for the separation, purification and concentration of phenolic compounds, with special emphasis on anthocyanins, are also provided.

Membrane Technologies in Wine Industry: An Overview

Membrane processes are increasingly reported for various applications in wine industry such as microfiltration, electrodialysis, and reverse osmosis, but also emerging processes as bipolar electrodialysis and membrane contactor. Membrane-based processes are playing a critical role in the field of separation/purification, clarification, stabilization, concentration, and de-alcoholization of wine products. They begin to be an integral part of the winemaking process. This review will provide an overview of recent developments, applications, and published literature in membrane technologies applied in wine industry.

Membrane processing technology in the food industry: food processing, wastewater treatment, and effects on physical, microbiological, organoleptic, and nutritional properties of foods

Membrane processing technology (MPT) is increasingly used nowadays in a wide range of applications (demineralization, desalination, stabilization, separation, deacidification, reduction of microbial load, purification, etc.) in food industries. The most frequently applied techniques are electrodialysis (ED), reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), and microfiltration (MF). Several membrane characteristics, such as pore size, flow properties, and the applied hydraulic pressure mainly determine membranes' potential uses. In this review paper the basic membrane techniques, their potential applications in a large number of fields and products towards the food industry, the main advantages and disadvantages of these methods, fouling phenomena as well as their effects on the organoleptic, qualitative, and nutritional value of foods are synoptically described. Some representative examples of traditional and modern membrane applications both in tabular and figural form are also provided.

Improvement on the concentrated grape juice physico-chemical characteristics by an enzymatic treatment and Membrane Separation Processes

ABSTRACT In this work, the improvement on the concentrated grape juice physico-chemical characteristics by using an enzymatic treatment followed by Membrane Separation Process (MSP) has been investigated. By using Novozym 33095(r) and Ultrazym AFP L(r) enzymes varying three operating parameters, the best result on the grape pulp characteristics was attained for the Novozym 33095(r) performed at 35oC, 15 min. and 50 mgL-1. In micro/ultra filtration processes after enzymatic pretreatment, the best performance of the MSP with high permeate flux value and suitable grape juice characteristics was attained using 0.05 mm membrane pore size, 1 bar pressure and 40 oC treatment temperature. When reverse osmosis process is operated at 40 bar and 40oC, high soluble solid and low turbidity values are attained. An enzymatic treatment along with MSP has shown an alternative and efficient grape juice processing system, being possible to extend to other foods.

Reverse osmosis as a potential technique to improve antioxidant properties of fruit juices used for functional beverages

Reverse osmosis (RO) as a potential technique to improve the antioxidant properties of cranberry, blueberry and apple juices was evaluated for the formulation of a functional beverage. The effects of temperature (20-40 °C) and trans-membrane pressure (25-35 bars) on physico-chemical and antioxidant properties of fruit juices were evaluated to optimize the operating parameters for each fruit juice. There was no significant effect on any quality parameters of fruit juices under studied operating parameters of RO. However, total soluble solid, total acidity and colour (a(∗)) of the concentrated juices increased in proportion to their volumetric concentrations. Antioxidant capacity measured by FRAP assay of concentrated apple, blueberry and cranberry juice was increased by 40%, 34%, and 30%, respectively. LDL oxidation inhibition by concentrated blueberry and cranberry juice was increased up to 41% and 45%, respectively. The results suggest that RO can be used for enhancing the health promoting properties of fruit juices.