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Red and purple grape juices (GJs) have long been consumed worldwide for their unique taste and nutritive value. Moreover, grape is postulated to play an important role in the improvement of cardiovascular risk factors owing to its rich polyphenol content. Little is known regarding GJ's holistic chemistry and functionality as compared to those of other fruit juices. This review aims to compile the state-of-the art chemistry of colored grape juices and in context to its analysis and nutritional values. Further, a review of potential contaminants to be introduced during manufacturing and other factors that influence juice quality and or health effects are presented to help maximize GJ's quality. A comparison between analytical methods for juice QC establishment is presented employing hyphenated platforms versus direct spectroscopic techniques. The enrichment of the colored skin with a myriad of phenolics poses it as a functional beverage compared to that of skinless juice. [ABSTRACT FROM AUTHOR]

The effects of concentrated fruit juices on mass transfer and enhancement of health-promoting properties of apple slices treated by an osmotic dehydration process with (PVOD) and without (OD) a vacuum were investigated. Hot air-drying (AD) was used as the finish drying process to produce apple chips. The apple chips obtained by OD + AD and PVOD + AD with grape juice had a total phenol content (TPC) of 81.54 ± 3.66 and 86.09 ± 1.23 mg GAE/100 g of dry matter, respectively, significantly higher than that (24.99 ± 0.46 mg GAE/100 g dry matter) of the chips from fresh apples (control). Similarly, DPPH radical–scavenging activity values of the OD + AD and PVOD + AD chips treated with grape juice were 78.44 ± 3.02% and 81.13 ± 2.47%, respectively, significantly higher than that of the control (26.06 ± 0.53%). The dehydration rate in the OD and PVOD processes was positively correlated with the osmotic pressure difference (Δπ) between the osmotic solution and the apple tissue following an exponential relation, and thus, Δπ has functioned as the driving force for mass transfer in the OD and PVOD processes. Concentrated fruit juices are shown to be effective osmotic solutions to produce colorful apple chips with enhanced health-promoting properties. [ABSTRACT FROM AUTHOR]

A laboratory-scale ultraviolet (UV-C) reactor based on Dean vortex technology was designed and tested for its capability to inactivate microorganisms in apple and red grape juices in relatively low doses of UV-C. Experiments were carried out with freshly squeezed apple juice (AJ) and freshly squeezed grape juice (GJ) inoculated with Lactobacillus plantarum NRIC1749 and Saccharomyces cerevisiae NCIB4932. Furthermore, physicochemical properties, antioxidant activity, total phenolic content, 5-HMF and colour analysis were performed in freshly squeezed apple (AJ) and grape juices (GJ). A UV-C treatment with 1668 mJ cm−2 led to an approximately 4.07-log inactivation of Lactobacillus plantarum NRIC1749 and 1.79-log inactivation of Saccharomyces cerevisiae NCIB4932 in AJ. A 0.69-log and 0.46-log reduction could be achieved for the inactivation of L. plantarum and S. cerevisiae in GJ at 1232 mJ cm−2, respectively. DPPH radical scavenging activity and total phenolic content of UV-C treated apple juice significantly increased, whereas total phenolic content remained constant in GJ. However, UV-C treatment had no significant effect on 5-HMF content of both juices. An effect of the treatment on the colour of both juices was observed. No significant change in the quality attributes (appearance, colour, odour, taste) was determined in the both UV-C treated juices. [ABSTRACT FROM AUTHOR]

In this study, carboxymethyl chitosan (CMCS) was combined with epigallocatechin gallate (EGCG), a natural antioxidant polyphenol, by a free radical grafting procedure to enhance its application potential on the preservation of fruit juice. The successful formation of EGCG-grafted CMCS (EGCG-CMCS) was confirmed by ultraviolet–visible absorbance, Fourier transform infrared spectroscopy, and proton nuclear magnetic resonance. The optimal molar ratio of EGCG to CMCS monomer was 0.5:1, which led to a grafting ratio of 47.8 mg/g in EGCG-CMCS. The X-ray diffraction patterns and thermal behavior showed that EGCG-CMCS had a lower crystallinity and thermal stability than CMCS, which is probably due to the reduction in hydrogen bonds caused by grafting. Then, EGCG-CMCS was used as an additive for the preservation of grape juice. After storage at 4 °C for 7 days, the EGCG-CMCS–treated juice remained 90.6% of vitamin C, which was much higher than that of the CMCS-treated juice and the control. Similar results were also achieved for total phenolic content, total soluble solids, and titratable acidity. Moreover, EGCG-CMCS effectively maintained the antioxidant capacity and sensory color quality of the juice and inhibited microbial growth during storage. Our results suggest that ECGC-CMCS could be a promising biopreservative for fresh fruit juice. [ABSTRACT FROM AUTHOR]

Zygosaccharomyces rouxii is the most frequent spoilage yeast species detected in concentrated grape juice. In order to reduce Z. rouxii populations and consequently extend the microbiological shelf life of this product, different programs of thermal pasteurization and high hydrostatic pressures processing were evaluated. Results showed that pasteurization temperatures higher than 75 °C are necessary to reduce Z. rouxii population in concentrated grape juice. Reduction of 7 logarithms can be reached after 90 s at 75 and 80 °C, and 5 s at 85 °C of pasteurization treatment. High hydrostatic pressure treatment above 500 MPa for 2 min are necessary to reduce 7 logarithms of Z. rouxii population and to significantly extend the shelf life of concentrate grape juice. Extension of holding times from 3 to 5 min, at the different high hydrostatic pressures evaluated, did not improve the Z. rouxii population reduction, nor the shelf life extension of concentrate grape juice. In conclusion, thermal pasteurization and high hydrostatic pressure could be suitable treatments to achieve the reduction of Z. rouxii population below the recommendation limit (102 CFU/g) and extension of the microbiological shelf life of concentrate grape juice. [ABSTRACT FROM AUTHOR]

The consumption of apple chips is increasing in the last decades because of the consumer’s preferences towards healthy snacks. However, the enzymatic browning, which is attributed mainly to polyphenol oxidase (PPO, EC 1.10.3.1) activity, negatively affects the sensory, nutritional, and antioxidant properties of dried apples as a consequence of the oxidation of phenolic substrates during post-harvest stages. The antibrowning and antioxidant effects of dipping pre-treatments with unripe grape juice as well as reference formulations including a mixture of 1% w/v ascorbic acid and 1% w/v citric acid, 6% w/v NatureSeal®, and 0.1% w/v sodium metabisulfite were evaluated by spectrophotometric and colorimetric assays on dried “Golden Delicious” apple slices. Based on HPLC analysis, the treated apple slices were enriched with bioactive compounds which effectively improved antioxidant capacity and limited enzymatic browning by increasing lightness, reducing color change, and inhibiting PPO activity. Hence, the juice of unripe grapes recovered as agricultural wastes during bunch thinning of vineyards could be proposed as a safe, inexpensive, and eco-friendly alternative to conventional antibrowning treatments in apple processing. [ABSTRACT FROM AUTHOR]

Ultraviolet (UV) light-assisted titanium dioxide (TiO2) photocatalysis is an emerging technology in food safety that utilizes TiO2 photocatalysts to accelerate the generation of reactive oxygen species during UV illumination. In this work, we studied the use of immobilized TiO2-SiO2 photocatalysts illuminated with UVA radiation (350 nm; 14.8 mW/cm2) for the inactivation of Escherichia coli ATCC 25922 in white grape juice, and compared the effectiveness of the photocatalytic disinfection with respect to the quality attributes of white grape juice against those of thermal and UVC (254 nm; 19.7 mW/cm2) treated samples. To obtain a 5-log reduction of the target microorganism, treatment durations of UVA in the absence and presence of the photocatalyst were 60 and 40 min, respectively. A 5-log reduction with UVC radiation led to the loss of health-related compounds such as vitamin C, total phenolic content, and total antioxidant capacity at 92.0 ± 1.1%, 19.4 ± 5.6%, and 54.3 ± 10.0%, respectively. However, the same level of reduction with UVA led to a loss of 74.2 ± 2.3%, 7.1 ± 3.6%, and 39.7 ± 2.5%, and with UVA-assisted photocatalytic method resulted in a loss of 75.8 ± 6.1%, 13.6 ± 5.8%, and 45.6 ± 4.4% of vitamin C, total phenolic content, and total anti-oxidant capacity, respectively. Given its efficacy in deactivating E. coli while retaining a relatively higher level of health-related constituents in the fruit juice compared to other common pasteurization techniques, the photocatalyst developed in this study provides a promising technology for food disinfection. [ABSTRACT FROM AUTHOR]

Red and white grape musts were enriched with 7-hydroxymatairesinol (HMR), which is the main lignan contained in spruce knots. Lignan enrichment was achieved by adding a spruce knot ethanol extract. Enriched musts were stored for 12 months and during storage must samples were periodically analyzed for HMR and alpha-conidendrin content, antioxidant activity, total polyphenols, and anti-mutagenicity. The data were statistically evaluated in order to determine the influence of grape type, quantity of added lignan extracts, addition of sugar, method of preservation and storage time on the quantity of lignans added, antioxidant activity, total polyphenols, and anti-mutagenicity. Lignan content was significantly influenced by the addition of lignan extracts. After storage, lignan content had changed only moderately and the added lignans were stable in the stored musts. Total polyphenol content and antioxidant activity of grape musts were significantly increased by the type of must grape and by thermomaceration. Thermomacerated red musts exhibited higher anti-mutagenicity compared to thermomacerated white musts, independent of lignan addition. [ABSTRACT FROM AUTHOR]

Grape juice quality can be substantially influenced by different processing methods and their parameters. This study deals with the influence of thermomaceration temperature and its holding time on important juice quality parameters such as the content of trans-resveratrol, trans-piceid, trans-ε-viniferin, and 2,4,6-trihydroxyphenantrene-2- O-glucoside. All the aforementioned compounds together with antioxidative capacity, total polyphenols, and antimutagenic activity were measured. This study used the following grapes: Blaufränkisch, Blaufränkisch bio, Saint Laurent, Grüner Veltliner, Grüner Veltliner bio, and Müller-Thurgau. For all tested grape varieties, the most important processing parameters were temperature and thermomaceration holding time. There were no significant differences in the content of the studied compounds. Three preservation technologies, freezing, bottle pasteurization, and high-pressure treatment, were also studied regarding the content of abovementioned biologically active compounds. Results of this study can be immediately applied to grape juice production. [ABSTRACT FROM AUTHOR]

In this work, the effects of eight different enzymatic preparations were compared in terms of the extraction of bioactive compounds as well as the yield and quality of grape juice from Vitis labrusca L. variety Concord. Juices were prepared by enzymatic treatment and the used preparations were characterized through five enzymatic activities: total pectinase (PE), polygalacturonase (PG), pectinlyase (PL), pectin methyl esterase (PME), and cellulase (CE). Quality parameters such as color, total soluble solids (°Brix), reducing sugars, titratable acidity, pH, and antioxidant capacity were determined for all samples. Phenolic compounds and anthocyanins were identified and quantified by HPLC-DAD-MS. Juice yield was improved by preparations with high activities of PG, PME, and PL, up to 9 % higher than the control, when used Pectinex Ultra Clear. For the extraction of bioactive compounds, the highest values were found for preparations with high CE activity. Regarding the phenolic compounds, 15 compounds were identified. The content of caftaric acid and total anthocyanins was improved up to 300 and 60 %, respectively, using Lallzyme Beta. It was possible to understand the role of each enzyme in the extraction of yield, quality parameters, and bioactive compounds. Pectinex Ultra Clear was the preparation that provided the highest yield and Lallzyme Beta the highest bioactive compounds concentration. For a good quality juice and high yields for the industry, it is important to have a good balance of pectinases and cellulases. [ABSTRACT FROM AUTHOR]

Pimaricin-loaded poly( N-isopropylacrylamide) nanohydrogels with and without acrylic acid, were evaluated as food-spoilage inhibitors in a model system and a real food product: grape juice. Pimaricin was proposed as a non-allergenic alternative to sulphites for protecting juices against recontamination. However, pimaricin may degrade under conditions and treatments (heating, acidification, lighting) commonly applied in producing fresh juices. Nanohydrogel encapsulation may be a feasible procedure to avoid pimaricin degradation, improving its antimicrobial activity. Pimaricin-free nanohydrogels did not affect the growth of the indicator yeast either in the food model system or in grape juice. Conversely, pimaricin-loaded nanohydrogels effectively inhibited the growth of the indicator yeast. In some cases, the inhibition was extended even further than using free pimaricin. For instance, in the food model system, pimaricin-loaded nanohydrogels with acrylic acid (NP) prevented the yeast growth for more than 81 h while free pimaricin was only effective for 12 h. Despite pimaricin-loaded nanohydrogels without acrylic acid (NP) were able to reduce maximum yeast growth, as in all treatments with pimaricin, the extent of the inhibitory effect was not significantly ( p > 0.05) different to that achieved with free pimaricin. In grape juice, both free pimaricin and NP treatment completely inhibited the growth of the indicator yeast until the end of the bioassay. However, the latter provided similar inhibition levels using a smaller amount of pimaricin due to PNIPA-20AA(5) protection and its controlled release from the nanohydrogel. Therefore, nanohydrogel encapsulation may help to optimise antifungal treatments and decrease the incidence of food allergies. [ABSTRACT FROM AUTHOR]

In the present work, the stability of grape marc powder was evaluated during its storage at room conditions for 6 months. Grape juice marc from Vitis labrusca cv. 'Isabel' was dried to 8.8 ± 0.9 % moisture content (wet basis) in forced convection drying equipment at 70 °C, crushed and stored aseptically in dark polyethylene bags and kept at 25 ± 2 °C for up to 6 months. Grape marc powder was microbiologically safe, free of Salmonella sp., Bacillus cereus, and fecal coliforms. Total phenolic compounds with 1,1-diphenyl-2-pic-ryl-hydrazyl (DPPH) scavenging capacity and ferric reducing antioxidant power (FRAP) were stable, although monomeric anthocyanins and compounds with the capability of scavenging 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radicals showed to be susceptible to degradation through the storage period. Moisture sorption isotherm at 25 °C for the powder material was determined by static gravimetric methodology. The sorption isotherm of the grape marc powder showed a sigmoidal shape (type II), typical of food materials. The experimental data was satisfactorily fitted by the GAB (Guggenheim-Anderson-de Boer) model, giving a monolayer moisture content ( X) of 6.75 % (dry basis). Results indicate that grape marc powder can be considered as a potential functional ingredient with an acceptable stability. [ABSTRACT FROM AUTHOR]

Grape juice is a natural source of polyphenols with potential health benefits. The aim of this study was to assess the optimized basis of the pectinolytic activity through a multivariate design for the bioactive enrichment of polyphenols in grape juices and to evaluate the effect of pectinases on the extraction of minerals by ICP-MS and FAAS. Grape juices were treated with pectinases Everzym® Color and Rapidase® Smart at different conditions of enzyme concentration (0.16-1.84 g L), temperature (14.8-83.6 ºC), and incubation time (9.6-110.5 min), and the effect on total phenolics, anthocyanin content, and antioxidant activity of juices were determined by employing a second-order central composite design in combination with response surface methodology. The different conditions showed significant variations in polyphenol levels of grape juices. For both of the enzymes, the increase of temperature and enzyme concentration led to a higher extraction of polyphenols, with a significant effect. Estimated effects depict a good correlation among dependent variables. For Rapidase, the optimized extraction of polyphenols was determined at an enzyme concentration of 1.57 g L and at a temperature of 54.8 ºC. For Everzym, higher concentrations of polyphenols were obtained at the enzyme concentration of 1.30 g L at 46.8 ºC. The extraction using the Rapidase enzyme significantly increased the levels of Na, K, Mg, and Fe in grape juices ( p < 0.05). The pectinolytic activity increased the polyphenol and mineral concentrations in grape juices. In addition, the optimal conditions of the pectinolytic treatment comprise a feasible alternative to improve the bioactive potential of grape juices. [ABSTRACT FROM AUTHOR]

Pulsed electric field (PEF) is a promising nonthermal food preservation technology that is based on the use of electric field to eradicate spoilage and pathogenic microorganisms in food products. The effect of various biological factors on the transmembrane potential of different microorganisms ( Staphyloccocus aureus, Escherichia coli DH5α, and Saccharomyces cerevisiae) was investigated by means of both numerical simulation and experimental method. The PEF resistance of different microorganisms in grape juice was compared by applying field strength of 12-24 kV/cm, treatment time of 30-180 μs, and an initial temperature of 30 ºC. The results showed that S. cerevisiae exhibited the least resistance to PEF treatment, E. coli DH5α the second, and S. aureus the third. The simulation results indicated that larger cells like S. cerevisiae presented the higher values of transmembrane potential and induced field strength around the cells compared to E. coli DH5α and S. aureus, which led to a less resistance to PEF treatment. The effect of cell orientation on the induced transmembrane potential was very slight (1.67 % for E. coli DH5α and 3.43 % for S. cerevisiae). The thicker cell membrane caused concentrated electric field in the cell membrane, which enhanced the sensitivity of microorganism to PEF treatment. However, both transmembrane potential and electric field strength decreased with the thickness of cell wall increasing. According to both experimental and simulation results, it was evident that there was significant difference in the inactivation rate between different microorganisms, which could be largely attributed to the biological factors of different microorganisms. [ABSTRACT FROM AUTHOR]

Pinot noir grapes have a unique phenolic profile which can impinge on the extraction and stabilisation of compounds such as anthocyanins and tannins which contribute to the colour and mouthfeel of red wine. This study examined the concentration of phenolic compounds in Pinot noir grape must and wine following application of a novel microwave maceration treatment for red grape must. Microwave maceration was shown to be highly effective for extraction of phenolics from grape solids into grape juice. When juices were fermented to wine, ultraviolet-visible spectrophotometry showed microwave maceration was associated with significantly higher concentrations of total phenolics, anthocyanin, tannin and pigmented tannin in wine at 18 months bottle age, compared with control wine. Mean tannin concentration in microwave treatment wine was 0.60 gm/L at 18 months, compared with 0.14 gm/L in control wine. The microwave treatment was also associated with a substantial and rapid decrease in the grape-associated yeast population, compared with control maceration, and a shorter lag phase at the outset of alcoholic fermentation. Based on this study, microwave maceration warrants further investigation as a potential industrial-scale application in red winemaking. [ABSTRACT FROM AUTHOR]

The influence of ultraviolet-visible irradiation on some quality attributes (pH, soluble solids content, color parameters, absorption spectrum, vitamin C, total acidity, total phenolics, formol index, and total and reducing sugars) and polyphenol oxidase, peroxidase, and pectinmethylesterase activities of fresh grape juices was investigated. Grape juice was made from two varieties of white grapes (Victoria and Dauphine) and two varieties of pink grapes (Emperor and Red Globe). Each juice was irradiated for 140 min with a high-pressure mercury lamp of 400 W that emits in a range between 250 and 740 nm. Polyphenol oxidase was not completely inactivated during irradiation, reducing only 80% of its initial activity in juices from white grapes and only 50% in those from pink grapes. On the contrary, peroxidase was completely inactivated. A slight or nonexistent variation was observed in most of the measured physicochemical parameters, showing high stability during irradiation. Only vitamin C and color had a significant variation, with an average decrease of 30% for vitamin C in all varieties and a more important variation of color parameters in the pink varieties than in the white ones. [ABSTRACT FROM AUTHOR]

The work was aimed at comparing the effect of pulsed electric field (PEF) and thermal technologies on physical, chemical, microbiological, and nutritional properties of freshly squeezed grape juice of different varieties when they are applied using continuous flow systems. It has been evidenced that grape variety is a factor to be taken into account when comparing the processing effects of PEF and heat treatments. Nevertheless, results of general and specific microbial populations were not affected by it and followed a very similar trend with each processing treatment. Soluble solids, pH, acidity, and the electrical conductivity of grape juice were not affected by PEF processing. On average, PEF treatment reduced the radical scavenging activity a 9% in front of the 13% of the heat treatment whereas both treatments halved the protein content. Data of vitamin C, total polyphenol, cinnamic acid, free catechin and non-flavonoid content were not enough to show differences between both treatments. However, all these nutritionally related properties share the same behaviour, PEF processing yielded milder values than heat processed samples. Information comparing PEF and thermal processes on food products help to clarify the advantages and disadvantages of each technology even though the disparity in development and use of each one. [ABSTRACT FROM AUTHOR]

White and red grape juices (GJs) were subjected to ultraviolet C (UV-C) light as a non-thermal preservation technology using a coiled tube UV-C reactor with nine lamps. The effects of UV-C light on microbial (total aerobic count and yeast and mould count) and some chemical quality characteristics (total phenolics, antioxidant capacity, anthocyanin and polymeric colour, etc.) of white and red GJs were investigated. The results were compared with control (untreated) and heat-treated juice samples. Single-pass UV-C treatment (12.6 J/mL) of white and red GJs resulted in 3.51 and 3.59 log reductions in total aerobic count and, 2.71 and 2.89 log reductions in yeast and mould counts, respectively. The microbial loads of both GJs were completely eliminated after two passes through the reactor (25.2 J/mL). After UV-C and heat treatments, there were no significant changes in antioxidant capacity, total phenolics, titratable acidity, soluble solids and pH of white and red GJs ( P > 0.05). The losses in monomeric anthocyanins were 6.1% and 8.7% after UV-C treatment of 12.6 and 25.2 J/mL doses, respectively. However, anthocyanin level of red GJ was significantly affected by the heat treatment with an 11.8% loss ( P < 0.05). The percent polymeric colour of the red GJ with heat treatment was significantly higher compared to the colour with the UV-C treatment. [ABSTRACT FROM AUTHOR]

Pekmez is a concentrated and shelf life extended form of grape juice. We investigated the material behavior and the effect of processing factors during its solidification using in situ rheometry and color measurement by computer vision. Rheologically, pekmez (45.3 to 75 °Brix) is a Newtonian product. As expected, its viscosity increased with increasing solid content and decreasing temperature. A simplified model was proposed to describe the combined effect of concentration and temperature on pekmez viscosity. The color of pekmez changed from dark brown to white depending on the processing conditions such as the type and amount of whitener added and the rate and duration of mixing. [ABSTRACT FROM AUTHOR]

Incorporation of sucrose and raisin juice (in concentrated or in dried form) at 3 and 5% of flour weight to commercial wheat starch (Codex Alimentarius) gluten-free flour was carried out to examine the effects on baking, textural, and sensory properties of bread. Breads made with gluten-free flour are usually characterized by poor color and baking characteristics, as well as short shelf life. The current study was conducted to help solve these problems by using raisin juice, a natural sweetener that contains no preservatives, has lower caloric content than sucrose, and includes a number of important vitamins and minerals that are very important for the coeliac disease patients. The study showed that 3% raisin juice in concentrated form contributes to a great improvement in loaf volume, color, and hardness characteristics of gluten-free bread during the first day after baking but a higher staling rate because of its high moisture content. Dried raisin juice gave bread higher loaf volume and better color compared to the control gluten-free bread and also increased its shelf life because of its moisture absorption properties. Sensory analysis revealed a preference for breads containing concentrated raisin juice because of its fruity flavor, whereas all the samples that contained 5% raisin juice had very dark color. [ABSTRACT FROM AUTHOR]