Application of Multivariate Regression and Artificial Neural Network Modelling for Prediction of Physicochemical Properties of Grape-Skin Compost

The reusability of by-products in the food industry is consistent with sustainable and greener production; therefore, the aim of this paper was to evaluate the applicability of multiple linear regression (MLR), piecewise linear regression (PLR) and artificial neural network models (ANN) to the prediction of grape-skin compost's physicochemical properties (moisture, dry matter, organic matter, ash content, carbon content, nitrogen content, C/N ratio, total colour change of compost samples, pH, conductivity, total dissolved solids and total colour change of compost extract samples) during in-vessel composting based on the initial composting conditions (air-flow rate, moisture content and day of sampling). Based on the coefficient of determination for prediction, the adjusted coefficient of determination for calibration, the root-mean-square error of prediction (RMSEP), the standard error of prediction (SEP), the ratio of prediction to deviation (RPD) and the ratio of the error range (RER), it can be concluded that all developed MLR and PLR models are acceptable for process screening. Furthermore, the ANN model developed for predicting moisture and dry-matter content can be used for quality control (RER >11). The obtained results show the great potential of multivariate modelling for analysis of the physicochemical properties of compost during composting, confirming the high applicability of modelling in greener production processes.

Dual Application of Waste Grape Skin for Photosensitizers and Counter Electrodes of Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs), a powerful system to convert solar energy into electrical energy, suffer from the high cost of the Pt counter electrode and photosensitizer. In this study, the dual application of waste grape skin is realized by employing the grape skin and its extract as the carbon source of the carbon-based counter electrode and photosensitizer, respectively. The ultraviolet–visible absorption and Fourier transform infrared spectroscopy verify the strong binding between the dye molecules (anthocyanins) in the extract and the TiO₂ nanostructure on the photoanode, contributing to a high open-circuit voltage (V_OC) value of 0.48 V for the assembled DSSC device. Moreover, the waste grape skin was subjected to pyrolysis and KOH activation and the resultant KOH-activated grape skin-derived carbon (KA-GSDC) possesses a large surface area (620.79 m² g⁻¹) and hierarchical porous structure, leading to a high short circuit current density (J_SC) value of 1.52 mA cm⁻². Additionally, the electrochemical impedance spectroscopy reveals the efficient electron transfer between the electrocatalyst and the redox couples and the slow recombination of electrolytic cations and the photo-induced electrons in the conduction band of TiO₂. These merits endow the DSSC with a high photovoltaic efficiency of 0.48%, which is 33% higher than that of a common Pt-based DSSC (0.36%). The efficiency is also competitive, compared with some congeneric DSSCs based on other natural dyes and Pt counter electrode. The result confirms the feasibility of achieving the high-value application of waste grape skin in DSSCs.

Comparative Study on Inhibition of Pancreatic Cancer Cells by Resveratrol Gold Nanoparticles and a Resveratrol Nanoemulsion Prepared from Grape Skin

Resveratrol, a phenolic compound possessing vital biological activities such as anti-cancer, is present abundantly in grape skin, a waste produced during the processing of grape juice. The objectives of this study were to prepare resveratrol-gold nanoparticles and a resveratrol nanoemulsion from grape skin and study their inhibition effects on pancreatic cancer cells BxPC-3. The spherical-shaped citrate gold nanoparticles (GNPs) and resveratrol-gold nanoparticles (R-GNPs) were, respectively, prepared with a surface plasmon resonance peak at 528 and 538 nm, mean particle size of 20.8 and 11.9 nm, and zeta-potential at −32.7 and −66.7 mV, by controlling an appropriate concentration of citrate/resveratrol and gold chloride as well as stirring time and temperature. The resveratrol nanoemulsion, composed of soybean oil, Tween 80, and sucrose fatty acid ester in glycerol and water, possessed a high storage stability with a mean particle size of 14.1 nm, zeta-potential of −49.7 mV, and encapsulation efficiency of 95.5%. An antiproliferation study revealed that both R-GNPs and resveratrol nanoemulsion could effectively inhibit the growth of pancreatic cancer cells BxPC-3, with the latter showing a higher inhibition effect. Western blot analysis implied that both can down-regulate expressions of cyclin A, cyclin B, CDK1, and CDK2 and up-regulate expressions of p53 and p21, accompanied by enhancing cytochrome C expression, decreasing BcL-2 expression, increasing Bax expression, and leading to the elevation of caspase-8, caspase-9, and caspase-3 activities for cell apoptosis execution. Future research is needed to study the inhibition of pancreatic tumors in vivo by R-GNPs and resveratrol nanoemulsions.

Grape skin extract modulates neuronal stem cell proliferation and improves spatial learning in senescence-accelerated prone 8 mice

In recent years, the number of patients with neurodegenerative illness such as Alzheimer’s disease (AD) has increased with the aging of the population. In this study, we evaluated the effect of Grape skin extract (GSE) on neurotypic SH-SY5Y cells as an in vitro AD model, murine neurospheres as an ex vivo neurogenesis model and SAMP8 mice as an in vivo AD model. Our in vitro result showed that pre-treatment of SH-SY5Y cells with GSE ameliorated Aβ-induced cytotoxicity. Moreover, GSE treatment significantly decreased the number of neurospheres, but increased their size suggesting reduced stem cell self-renewal but increased proliferation. Our in vivo Morris water maze test indicated that GSE improves learning and memory in SAMP8 mice. To detect proliferation and newborn neurons, we measured BrdU+ cells in the dentate gyrus (DG). GSE treatment increased the number of BrdU+ cells in the DG of SAMP8 mice. Finally, we showed that GSE induced a decrease in inflammatory cytokines and an increase in neurotransmitters in the cerebral cortex of SAMP8 mice. These results suggested that GSE increased neurogenic zone proliferation and memory but decreased oxidative stress associated with pro-inflammatory cytokines in aging, thus protecting neurons.

Feeding Broiler Chickens with Grape Seed and Skin Meals to Enhance α- and γ-Tocopherol Content and Meat Oxidative Stability

Grape seeds (GS) and grape skins (GK) are natural sources of polyphenols with featured antioxidant capacity. An experiment was conducted to investigate the effect of these polyphenol sources in diets formulated to contain the same total extractable grape polyphenol content on growth performance, protein and extractable polyphenol digestibility, plasma and meat α- and γ-tocopherol and thigh meat oxidation in broiler chickens. Five experimental diets were formulated: control, control + vitamin E (200 mg/kg), 30 g/kg GS diet, 110 g/kg GK diet, GS + GK diet (a mixture of 24.4 g/kg GS and 13.1 g/kg GK designed to simulate a reconstituted grape pomace). Feeding chickens with 110 g/kg GK reduced (p < 0.001) daily weight gain, worsened (p < 0.001) feed conversion ratio, increased (p < 0.001) non-extractable polyphenol content in the ileum and in the excreta and decreased (p < 0.05) ileal protein digestibility. Regardless of the grape polyphenol source used, the inclusion of grape byproducts in the diets led to an increase of total extractable polyphenol contents in the ileum (p < 0.01) and the excreta (p < 0.001), which resulted (p < 0.001) in a decrease of extractable polyphenol digestibilities. Alpha- and gamma-tocopherol concentrations increased (p < 0.001) in plasma and in seven-day stored meat in birds fed the diet combining GS and GK with respect to the control group. As it happened with the vitamin E supplementation, feeding the combination of GS and GK also reduced (p < 0.001) the concentration of the lipid peroxidation marker (malondialdehyde) in the stored meat of chickens.

The Potential of Grape Pomace Varieties as a Dietary Source of Pectic Substances

Grape pomace is one of the most abundant solid by-products generated during winemaking. A lot of products, such as ethanol, tartrates, citric acid, grape seed oil, hydrocolloids, bioactive compounds and dietary fiber are recovered from grape pomace. Grape pomace represents a major interest in the field of fiber extraction, especially pectin, as an alternative source to conventional ones, such as apple pomace and citrus peels, from which pectin is obtained by acid extraction and precipitation using alcohols. Understanding the structural and functional components of grape pomace will significantly aid in developing efficient extraction of pectin from unconventional sources. In recent years, natural biodegradable polymers, like pectin has invoked a big interest due to versatile properties and diverse applications in food industry and other fields. Thus, pectin extraction from grape pomace could afford a new reason for the decrease of environmental pollution and waste generation. This paper briefly describes the structure and composition of grape pomace of different varieties for the utilization of grape pomace as a source of pectin in food industry.

Health Effects of Grape Seed and Skin Extracts and Their Influence on Biochemical Markers

This review is focused on the study of the effects of grape seed and skin extract (GSSE) on human health. GSSE contains high concentrations of important polyphenolic substances with high biological activity. This review is a summary of studies that investigate the effects of GSSE on diabetes mellitus, cardiovascular disease and cancer, its neuroprotective effect, and its effects on the gastrointestinal tract and other health complications related to these diseases. The results of the studies confirm that the anti-inflammatory, antiapoptotic, and pro-proliferative effects of “Vitis vinifera L.” seed extract reduce the level of oxidative stress and improve the overall lipid metabolism.

Analysis of Phenolic Content in Grape Seeds and Skins by Means of a Bio-Electronic Tongue

A bio-electronic tongue has been developed to evaluate the phenolic content of grape residues (seeds and skins) in a fast and easy way with industrial use in mind. A voltammetric electronic tongue has been designed based on carbon resin electrodes modified with tyrosinase combined with electron mediators. The presence of the phenoloxydase promotes the selectivity and specificity towards phenols. The results of multivariate analysis allowed discriminating seeds and skins according to their polyphenolic content. Partial least squares (PLS) has been used to establish regression models with parameters related to phenolic content measured by spectroscopic methods i.e., total poliphenol content (TPC) and Folin–Ciocalteu (FC) indexes. It has been shown that electronic tongue can be successfully used to predict parameters of interest with high correlation coefficients (higher than 0.99 in both calibration and prediction) and low residual errors. These values can even be improved using genetic algorithms for multivalent analysis. In this way, a fast and simple tool is available for the evaluation of these values. This advantage may be due to the fact that the electrochemical signals are directly related to the phenolic content.

In Vivo Effects of Polymerized Anthocyanin from Grape Skin on Benign Prostatic Hyperplasia

Benign prostatic hyperplasia (BPH) is a common chronic disease of the urinary system among elderly men. Especially, the metabolic imbalance of androgen in elderly men is one of the leading causes of BPH. Dihydrotestosterone (DHT) and converted testosterone by 5-α reductase type 2 (5AR2), binding with androgen receptor (AR), affect prostate proliferation and growth. In BPH, levels of androgen signaling-related protein expression are shown highly. Androgen signaling induces the overexpression of prostate-specific antigen (PSA) and cell proliferation factor such as proliferating cell nuclear antigen (PCNA) and cyclin D1. Grape skin anthocyanins are well known for their antioxidative, anti-cancer, anti-diabetes, anti-inflammatory, antimicrobial, and anti-aging activities. Polymerized anthocyanin (PA) downregulated the expression of androgen signaling-related proteins such as 5AR2, AR, and PSA in LNCaP cell lines. Furthermore, we investigated the effects on PA in testosterone propionate-induced BPH rat experiments. The oral administration of PA decreased the prostate weight in rats with TP-induced BPH. PA decreased the AR, 5AR2, SRC1, PSA, PCNA, and cyclin D1 expression in prostate tissues and the serum DHT levels, ameliorated the BPH-mediated increase of Bcl-2 expression, and increased the Bax expression. These results suggest that PA may be a potential natural therapeutic agent for BPH treatment.

Evaluation of Volatile Metabolites Emitted In-Vivo from Cold-Hardy Grapes during Ripening Using SPME and GC-MS: A Proof-of-Concept

In this research, we propose a novel concept for a non-destructive evaluation of volatiles emitted from ripening grapes using solid-phase microextraction (SPME). This concept is novel to both the traditional vinifera grapes and the cold-hardy cultivars. Our sample models are cold-hardy varieties in the upper Midwest for which many of the basic multiyear grape flavor and wine style data is needed. Non-destructive sampling included a use of polyvinyl fluoride (PVF) chambers temporarily enclosing and concentrating volatiles emitted by a whole cluster of grapes on a vine and a modified 2 mL glass vial for a vacuum-assisted sampling of volatiles from a single grape berry. We used SPME for either sampling in the field or headspace of crushed grapes in the lab and followed with analyses on gas chromatography-mass spectrometry (GC-MS). We have shown that it is feasible to detect volatile organic compounds (VOCs) emitted in-vivo from single grape berries (39 compounds) and whole clusters (44 compounds). Over 110 VOCs were released to headspace from crushed berries. Spatial (vineyard location) and temporal variations in VOC profiles were observed for all four cultivars. However, these changes were not consistent by growing season, by location, within cultivars, or by ripening stage when analyzed by multivariate analyses such as principal component analysis (PCA) and hierarchical cluster analyses (HCA). Research into aroma compounds present in cold-hardy cultivars is essential to the continued growth of the wine industry in cold climates and diversification of agriculture in the upper Midwestern area of the U.S.

Flavanol Quantification of Grapes via Multiple Reaction Monitoring Mass Spectrometry. Application to Differentiation among Clones of Vitis vinifera L. cv. Rufete Grapes

The determination of the detailed flavanol composition in food matrices is not a simple task because of the structural similarities of monomers and, consequently, oligomers and polymers. The aim of this study was the development and validation of an HPLC-MS/MS-multiple reaction monitoring (MRM) method that would allow the accurate and precise quantification of catechins, gallocatechins, and oligomeric proanthocyanidins. The high correlation coefficients of the calibration curves (>0.993), the recoveries not statistically different from 100%, the good intra- and interday precisions (<5%), and the LOD and LOQ values, low enough to quantify flavanols in grapes, are good results from the method validation procedure. Its usefulness has also been tested by determining the detailed composition of Vitis vinifera L. cv. Rufete grapes. Seventy-two (38 nongalloylated and 34 galloylated) and 53 (24 procyanidins and 29 prodelphinidins) flavanols have been identified and quantified in grape seed and grape skin, respectively. The use of HCA and PCA on the detailed flavanol composition has allowed differentiation among Rufete clones.

Extraction of Proanthocyanidins and Anthocyanins from Grape Skin by Using Ionic Liquids

In this study, eight different types of imidazolium-based ionic liquids (ILs) were applied as new solvents in the extraction of flavonoids from grape skin, and compared to the conventional organic solvent extraction that was not reported earlier. The structure of anions, cations and concentration of ILs significantly affected extraction yields. The highest mass fractions of proanthocyanidins and anthocyanins were obtained with 2.5 mol/L of 1-butyl-3-methylimidazolium bromide [C₄mim][Br] and 2.5 mol/L of 1-ethyl-3-methylimidazolium bromide [C₂mim][Br], respectively. The studied ILs provided an excellent preliminary result in the extraction of anthocyanins. Significantly higher mass fractions of total and all free anthocyanins were extracted with 2.5 mol/L of [C₂mim][Br] and 2.5 mol/L of 1-methylimidazolium hydrogen sulfate [mim][HSO₄] than with conventional solvent with the exception of anthocyanin-3-O-acetylmonoglucosides in the latter. On the other hand, 2.5 mol/L of [C₄mim][Br] and 2.5 mol/L of 1-(4-sulfobutyl)-3-methylimidazolium hydrogen sulfate [sC₄mim][HSO₄] showed significantly higher selectivity towards anthocyanin-3-O-acetylmonoglucosides and anthocyanin-3-(6-O-p-coumaroyl)monoglucosides.

Grape skin extracts from winemaking by-products as a source of trapping agents for reactive carbonyl species

BACKGROUND

Clinical evidence supports the relationship between carbonyl stress and type II diabetes and its related pathologies. Methylglyoxal (MGO) is the major dicarbonyl compound involved in carbonyl stress. Efforts are therefore being made to find dietary compounds from natural sources that could exert an MGO trapping response.

RESULTS

The in vitro MGO trapping capacity of six red and seven white grape skin extracts (GSE) obtained from winemaking by-products was investigated. Methanolic GSE exhibited a promising MGO trapping capacity that was higher in red GSE (IC50 2.8 mg mL(-1)) when compared with white GSE (IC50 3.2 mg mL(-1)). The trapping ability for red GSE correlated significantly with total phenolic content and antioxidant capacity. However, no correlations were observed for white GSE, which suggests that other compounds were involved in the trapping activity.

CONCLUSION

GSE may be considered a natural source of carbonyl stress inhibitors, thus opening up its possible utilization as a nutraceutical ingredient. Further investigations are required to understand the mechanism involved in the carbonyl trapping ability of red and white grape skin samples and their relationship with glycation.

Following the compositional changes of fresh grape skin cell walls during the fermentation process in the presence and absence of maceration enzymes

Cell wall profiling technologies were used to follow compositional changes that occurred in the skins of grape berries (from two different ripeness levels) during fermentation and enzyme maceration. Multivariate data analysis showed that the fermentation process yielded cell walls enriched in hemicellulose components because pectin was solubilized (and removed) with a reduction as well as exposure of cell wall proteins usually embedded within the cell wall structure. The addition of enzymes caused even more depectination, and the enzymes unravelled the cell walls enabling better access to, and extraction of, all cell wall polymers. Overripe grapes had cell walls that were extensively hydrolyzed and depolymerized, probably by natural grape-tissue-ripening enzymes, and this enhanced the impact that the maceration enzymes had on the cell wall monosaccharide profile. The combination of the techniques that were used is an effective direct measurement of the hydrolysis actions of maceration enzymes on the cell walls of grape berry skin.