Hydrolysis of terpenyl glycosides in grape juice and other fruit juices: a review

Comparison of Dip-it-DART-Orbitrap-MS With Nitrogen Plasma to HPLC/Orbitrap-MS in Profiling Aromatic Glycoconjugation in White Grapes

Direct analysis of aromatic glycosidic precursors in plants has posed an analytical challenge for decades. Traditional techniques, such as SPE-GC/MS, primarily provided information on volatile aglycones released through hydrolysis. However, the application of high-resolution mass spectrometry combined with liquid chromatography has enabled the direct analysis of intact glycosides without the need for derivatization or hydrolysis. Advances in soft ionization methods, such as DART, offer a novel approach to exploring the hidden aromatic potential in grapes without chromatographic separation. In this work, we present a novel and rapid method for screening aromatic glycosidic precursors in white grapes using high-resolution mass spectrometry (Orbitrap) combined with the soft ionization DART method with nitrogen plasma. Optimization of N2-DART ionization parameters, including grid voltage, gas temperature, and Dip-it sampler speed, performed on selected synthetic glycosidic precursors, allowed the establishment of characteristic ionization patterns and evaluation of 15 groups of glycosidic precursors. The results from the profiling analysis using the N2-DART-Orbitrap-MS method are comparable to those obtained by HPLC/Orbitrap-MS method. This new analytical approach, N2-DART-Orbitrap-MS, reduces drastically analysis time by eliminating the need for chromatographic separation when screening glycoside precursors, uses a convenient Dip-it tips for sampling. It also allows for deeper exploration of ionization using nitrogen plasma, applied for the first time in the analysis of glycoside precursors, demonstrating the applicability of this method for the rapid characterization and screening of glycosidically bound aroma compounds in plants.

β-Glucosidase Activity of Lactiplantibacillus plantarum: A Key Player in Food Fermentation and Human Health

β-glucosidases are a relevant class of enzymes in the food industry due to their role in hydrolyzing different types of glycosidic bonds. This activity allows for formation of volatile compounds and release of bioactive aglycone compounds. In addition to endogenous β-glucosidase activity present in raw material, the function of β-glucosidases in fermenting microorganisms has been progressively clarified and increasingly appreciated. In this regard, several lactic acid bacteria, including Lactiplantibacillus plantarum, showed high β-glucosidase activity, which can be considered as a valid biotechnological resource in different food sectors. Here, we reviewed the huge literature in which the β-glucosidases of L. plantarum were shown to play a role, highlighting how their action results in enhancing the nutritional, sensory, and functional properties of fermented foods. To this aim, after a brief introduction of the main functions of these enzymes in several kingdoms, we critically analyzed the involvement of L. plantarum β-glucosidases in plant-based food production, with a particular insight for soy, cassava, and olive-fermented products, as well as in the production of both alcoholic and non-alcoholic beverages. We trust that the reports summarized here can be helpful in planning future research and innovative strategies to obtain pleasing, functional, and healthy foods.

The formation of volatiles in fruit wine process and its impact on wine quality

Fruit wine is one of the oldest fermented beverages made from non-grape fruits. Owing to the differences in fruit varieties, growing regions, climates, and harvesting seasons, the nutritional compositions of fruits (sugars, organic acids, etc.) are different. Therefore, the fermentation process and microorganisms involved are varied for a particular fruit selected for wine production, resulting in differences in volatile compound formation, which ultimately determine the quality of fruit wine. This article reviews the effects of various factors involved in fruit wine making, especially the particular modifications differing from the grape winemaking process and the selected strains suitable for the specific fruit wine fermentation, on the formation of volatile compounds, flavor and aroma profiles, and quality characteristics of the wine thus produced. KEY POINTS: • The volatile profile and fruit wine quality are affected by enological parameters. • The composition and content of nutrients in fruit must impact volatile profiles. • Yeast and LAB are the key determining factors of the volatile profiles of fruit wines.

Volatilomics of Fruit Wines

Volatilomics is a scientific field concerned with the evaluation of volatile compounds in the food matrix and methods for their identification. This review discusses the main groups of compounds that shape the aroma of wines, their origin, precursors, and selected metabolic pathways. The paper classifies fruit wines into several categories, including ciders and apple wines, cherry wines, plum wines, berry wines, citrus wines, and exotic wines. The following article discusses the characteristics of volatiles that shape the aroma of each group of wine and the concentrations at which they occur. It also discusses how the strain and species of yeast and lactic acid bacteria can influence the aroma of fruit wines. The article also covers techniques for evaluating the volatile compound profile of fruit wines, including modern analytical techniques.

Kinetics of aroma formation from grape-derived precursors: Temperature effects and predictive potential

This study investigates the accumulation and degradation of aroma molecules released by acid hydrolysis of aroma precursors in winemaking grapes. A first-order kinetics model effectively interprets this accumulation, including subsequent degradation. Experimentation at three temperatures categorizes specific grape-derived aroma molecules into three stability-based groups: labile molecules from labile precursors, stable molecules from labile precursors, and stable molecules from stable precursors. While many grape-derived aromas exhibit similar patterns and levels of accumulation across temperatures, reaction rates significantly increase with temperature. The analysis of 12 samples of two grape varieties hydrolyzed at 50 °C for 5 weeks and 75 °C for 24 h confirms that fast hydrolysis accurately replicates varietal and between-sample aroma compositional differences. Moreover, the accumulated levels of 21 relevant grape-derived aromas strongly correlate with those at 50 °C, indicating that fast hydrolysis at 75 °C reliably predicts grape aroma potential.

Ethylene-responsive VviERF003 modulates glycosylated monoterpenoid synthesis by upregulating VviGT14 in grapes

Terpenoids are important contributors to the aroma of grapes and wines. Grapes contain terpenoids in both volatile free form and non-volatile glycosidic form, with the latter being more abundant. Glycosylated terpenoids are deemed as latent aromatic potentials for their essential role in adding to the flowery and fruity bouquet of wines. However, the transcriptional regulatory mechanism underlying glycosylated terpenoid biosynthesis remains poorly understood. Our prior study identified an AP2/ERF transcription factor, VviERF003, through DNA pull-down screening using the promoter of terpenoid glycosyltransferase VviGT14 gene. This study demonstrated that both genes were co-expressed and synchronized with the accumulation of glycosylated monoterpenoids during grape maturation. VviERF003 can bind to the VviGT14 promoter and promote its activity according to yeast one-hybrid and dual-luciferase assays. VviERF003 upregulated VviGT14 expression in vivo, leading to increased production of glycosylated monoterpenoids based on the evidence from overexpression or RNA interference in leaves, berry skins, and calli of grapes, as well as tomato fruits. Additionally, VviERF003 and VviGT14 expressions and glycosylated monoterpenoid levels were induced by ethylene in grapes. The findings suggest that VviERF003 is ethylene-responsive and stimulates glycosylated monoterpenoid biosynthesis through upregulating VviGT14 expression.

Discovery, structural characterization, and functional insights into a novel apiosidase from the GH140 family, isolated from a lignocellulolytic-enriched mangrove microbial community

OBJECTIVES

Apiosidases are enzymes that cleave the glycosidic bond between the monosaccharides linked to apiose, a branched chain furanose found in the cell walls of vascular plants and aquatic monocots. There is biotechnological interest in this enzyme group because apiose is the flavor-active compound of grapes, fruit juice, and wine, and the monosaccharide is found to be a plant secondary metabolite with pharmaceutical properties. However, functional and structural studies of this enzyme family are scarce. Recently, a glycoside hydrolase family member GH140 was isolated from Bacteroides thetaiotaomicron and identified as an endo-apiosidase.

RESULTS

The structural characterization and functional identification of a second GH140 family enzyme, termed MmApi, discovered through mangrove soil metagenomic approach, are described. Among the various substrates tested, MmApi exhibited activity on an apiose-containing oligosaccharide derived from the pectic polysaccharide rhamnogalacturonan-II. While the crystallographic model of MmApi was similar to the endo-apiosidase from Bacteroides thetaiotaomicron, differences in the shape of the binding sites indicated that MmApi could cleave apioses within oligosaccharides of different compositions.

CONCLUSION

This enzyme represents a novel tool for researchers interested in studying the physiology and structure of plant cell walls and developing biocatalytic strategies for drug and flavor production.

Aspergillus oryzae α-l-rhamnosidase: Crystal structure and insight into the substrate specificity

The subsequent biochemical and structural investigations of the purified recombinant α-l-rhamnosidase from Aspergillus oryzae expressed in Pichia pastoris, designated as rAoRhaA, were performed. The specific activity of the rAoRhaA wild-type was higher toward hesperidin and narirutin, where the l-rhamnose residue was α-1,6-linked to β-d-glucoside, than toward neohesperidin and naringin with an α-1,2-linkage to β-d-glucoside. However, no activity was detected toward quercitrin, myricitrin, and epimedin C. rAoRhaA kinetic analysis indicated that Km values for neohesperidin, naringin, and rutin were lower compared to those for hesperidin and narirutin. kcat values for hesperidin and narirutin were higher than those for neohesperidin, naringin, and rutin. High catalytic efficiency (kcat /Km ) toward hesperidin and narirutin was a result of a considerably high kcat value, while Km values for hesperidin and narirutin were higher than those for naringin, neohesperidin, and rutin. The crystal structure of rAoRhaA revealed that the catalytic domain was represented by an (α/α)6 -barrel with the active site located in a deep cleft and two β-sheet domains were also present in the N- and C-terminal sites of the catalytic domain. Additionally, five asparagine-attached N-acetylglucosamine molecules were observed. The catalytic residues of AoRhaA were suggested to be Asp254 and Glu524, and their catalytic roles were confirmed by mutational studies of D254N and E524Q variants, which lost their activity completely. Notably, three aspartic acids (Asp117, Asp249, and Asp261) located at the catalytic pocket were replaced with asparagine. D117N variant showed reduced activity. D249N and D261N variants activities drastically decreased.

A comprehensive review of Cornus officinalis: health benefits, phytochemistry, and pharmacological effects for functional drug and food development

Introduction

Cornus officinalis sieb. et zucc, a deciduous tree or shrub, is renowned for its "Cornus flesh" fruit, which is widely acknowledged for its medicinal value when matured and dried. Leveraging C. officinalis as a foundational ingredient opens avenues for the development of environmentally friendly health foods, ranging from beverages and jams to preserves and canned products. Packed with diverse bioactive compounds, this species manifests a spectrum of pharmacological effects, including anti-inflammatory, antioxidant, antidiabetic, immunomodulatory, neuroprotective, and cardiovascular protective properties.

Methods

This study employs CiteSpace visual analysis software and a bibliometric analysis platform, drawing upon the Web of Science (WOS) database for literature spanning the last decade. Through a comprehensive analysis of available literature from WOS and Google Scholar, we present a thorough summary of the health benefits, phytochemistry, active compounds, and pharmacological effects of C. officinalis. Particular emphasis is placed on its potential in developing functional drugs and foods.

Results and Discussion

While this review enhances our understanding of C. officinalis as a prospective therapeutic agent, its clinical applicability underscores the need for further research and clinical studies to validate findings and establish safe and effective clinical applications.

Selective Wine Aroma Enhancement through Enzyme Hydrolysis of Glycosidic Precursors

Selective enhancement of wine aroma was achieved using a broad spectrum of exogenous glycosidases. Eight different enzyme preparations were added to Verdejo wine, resulting in an increase in the levels of varietal volatile compounds compared to the control wine after 15 days of treatment. The enzyme preparations studied were robust under winemaking conditions (sulfur dioxide, reducing sugars, and alcohol content), and no inhibition of β-glucosidase activity was observed. Significant differences were detected in four individual terpenes (α-terpineol, terpinen-4-ol, α-pinene, and citronellal) and benzyl alcohol in all the treated wines compared to the control wine, contributing to the final wine to varying degrees. In addition, a significant increase in the other aromatic compounds was observed, which showed different patterns depending on the enzyme preparation that was tested. The principal component analysis of the data revealed the possibility of modulating the different aromatic profiles of the final wines depending on the enzyme preparation used. Taking these results into account, enhancement of the floral, balsamic, and/or fruity notes of wines is possible by using a suitable commercial enzyme preparation.

Release of glycosidically-bound volatiles in orange juice under natural conditions

Glycosidically-bound volatiles (GBV) can be released by exogenous acid and enzymatic hydrolysis. However, the liberation of GBV in natural juice is not reported. It was found that part of the GBV in orange juice (OJ) under natural conditions can be released and the types of volatiles were considerably fewer than the ones under exogenous acid, or enzymatic hydrolysis. Seven types of aroma substances were released under endogenous enzyme, among which ethyl 3-hydroxyhexanoate and eugenol are characteristic aroma substances of OJ. Six kinds of aroma substances can be released under natural acidic conditions, none are characteristic aroma substances of OJ. Ten kinds of substances were released under endogenous enzymes in combination with the acidic condition, among which benzyl alcohol, ethyl 3-hydroxyhexanoate, citral, and eugenol are characteristic aroma substances of OJ. The results indicated that GBV may play an important role in resisting the decrease of free aroma in OJ during storage.

Unlocking Flavor Potential Using Microbial β-Glucosidases in Food Processing

Aroma is among of the most important criteria that indicate the quality of food and beverage products. Aroma compounds can be found as free molecules or glycosides. Notably, a significant portion of aroma precursors accumulates in numerous food products as nonvolatile and flavorless glycoconjugates, termed glycosidic aroma precursors. When subjected to enzymatic hydrolysis, these seemingly inert, nonvolatile glycosides undergo transformation into fragrant volatiles or volatiles that can generate odor-active compounds during food processing. In this context, microbial β-glucosidases play a pivotal role in enhancing or compromising the development of flavors during food and beverage processing. β-glucosidases derived from bacteria and yeast can be utilized to modulate the concentration of particular aroma and taste compounds, such as bitterness, which can be decreased through hydrolysis by glycosidases. Furthermore, oral microbiota can influence flavor perception by releasing volatile compounds that can enhance or alter the perception of food products. In this review, considering the glycosidic flavor precursors present in diverse food and beverage products, we underscore the significance of glycosidases with various origins. Subsequently, we delve into emerging insights regarding the release of aroma within the human oral cavity due to the activity of oral microbial glycosidases.

A review on applications of β-glucosidase in food, brewery, pharmaceutical and cosmetic industries

β-glucosidases hydrolyse glycosidic bonds to release non-reducing terminal glucosyl residues from glycosides and oligosaccharides via catalytic mechanisms. It is very well known that the β-glucosidase enzyme is used in biorefineries for cellulose degradation, where β-glucosidases is the rate-limiting enzyme for the final glucose production from cellobiose. The β-glucosidase enzyme is used as a catalyst in other industrial sectors, including pharmaceuticals, breweries, dairy, and food processing. With the aid of β-glucosidase enzymes, cyanogenic glycosides and plant glycosides are transformed into sugar moiety and aglycones. These aglycone compounds are employed as aromatic compounds in the food processing and brewing industries. They are also used as medications and dietary supplements based on their pharmacological qualities. Applications of aglycones and the microbiological sources of β-glucosidase in aglycone production have been discussed in this review.

Acuminosylation of Tyrosol by a Commercial Diglycosidase

A commercial glycosidase mixture obtained from Penicillium multicolor (Aromase H2) was found to comprise a specific diglycosidase activity, β-acuminosidase, alongside undetectable levels of β-apiosidase. The enzyme was tested in the transglycosylation of tyrosol using 4-nitrophenyl β-acuminoside as the diglycosyl donor. The reaction was not chemoselective, providing a mixture of Osmanthuside H and its counterpart regioisomer 4-(2-hydroxyethyl)phenyl β-acuminoside in 58% yield. Aromase H2 is therefore the first commercial β-acuminosidase which is also able to glycosylate phenolic acceptors.

Determination of Tea Aroma Precursor Glycosides: An Efficient Approach via Liquid Chromatography-Tandem Mass Spectrometry

Tea aroma components are often stored as glycosidically bound forms in the tea plant (Camellia sinensis). However, the determination of these glycosides in tea samples is far from optimal. In the present study, we developed a high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method for simultaneous quantification of eight primary aroma glycosides within 10 min. After systematic optimization of multiple reaction monitoring (MRM) parameters, the proposed method was highly sensitive and accurate. Optimization of the method permitted the efficient extraction of aroma glycosides. The developed method was applied to analyze the contents of aroma glycosides in different organs of tea plants, including the bud, leaves, and stem. Contents of aroma glycosides in the harvested 'Shaancha 1' ranged from 36.1 to 40454.4 μg kg^-1. Geranyl glucoside and primeveroside mainly accumulated in young leaves, while other glycosides mainly accumulated in mature leaves. The findings document a rapid, reliable, and efficient analysis method. This method will be helpful in elucidating the biosynthesis and biotransformation mechanism of tea aroma glycosides and in promoting the development of the tea industry using advanced technological control approaches during the cultivation of tea plants and tea manufacture.

Effects of glycosidase on glycoside-bound aroma compounds in grape and cherry juice

This paper reports the occurrence of six kinds of commercial enzyme hydrolysis effects for use in grape juice and cherry juice, which provide a basis for studying the bound aroma compounds in fruit juice and their application in production. Using headspace solid-phase microextraction combined with GC-MS, a reliable procedure for determining the free and glycosidic-bound volatile compounds has been established. Comparison of these free and bound aroma compounds revealed that non-volatile glycosides, known as aroma precursors, occur at high concentrations in grape and cherry juice. Using six different glycosidase enzymes, 67 volatile compounds were identified in these two juices, including terpenes, C13-norisoprenoids, higher alcohols, esters, C6-compounds, C9-compounds, and phenols. The different enzymes had significant effects on varietal aroma. Creative and AR2000 had similar hydrolysis effects, which contribute greatly to the characteristic aroma of grape juice and cherry juice, significantly enhance the floral and fruity features of fruit juice, and improve aroma complexity in the system. The Creative enzyme can be used as a new choice for studying juice-bound aroma and hydrolysis-bound aroma in fruit and wine production.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-022-05662-3.

Molecular Rearrangement of Four Typical Grape Free Terpenes in the Wine Environment

In order to analyze the molecular rearrangement of terpenes in wine during aging, the changes in linalool, α-terpineol, nerol, and geraniol in model wine were investigated in the dark at low temperature for 90 days. Headspace-gas chromatograph-mass spectrometer/olfactometry was used for qualitative and relative quantitation of terpenes. Quantum mechanical calculation was used to analyze the Gibbs free energy. The results showed that nerol was converted into d-limonene, terpinolene, linalool, and α-terpineol. Geraniol was converted into β-ocimene, terpinolene, and linalool. Linalool was converted into terpinolene. The conversion rate of nerol to terpinolene was the highest with 5.94%. α-Terpineol was not converted spontaneously into other terpenes due to its lowest Gibbs free energy, indicating that the cyclization and isomerization could occur spontaneously through an exotherm reaction. However, the dehydroxylation of linalool, nerol, and geraniol required an energy source.

Characterisation of Tannin and Aroma Profiles of Pinot Noir Wines Made with or without Grape Pomace

The contribution of grape pomace on tannin concentration, tannin composition and aroma profile of Pinot noir wine was studied using different fermentation media to make up four treatments: GJ-P, grape juice plus pomace; MJ-P, model juice plus pomace; GJ, grape juice; MJ, model juice. The MJ-P treatment showed significantly lower amounts of tannins, mean degree of polymerisation (mDP), similar amounts of anthocyanin, and a similar secondary aroma profile compared to the GJ-P treatment. Grape pomace addition significantly increased the tannin concentration in wines. This study was also revealed the importance of phenolics present in grape juice in tannin polymerisation and final tannin concentration in wines. Grape pomace addition significantly reduced some important aroma compounds such as acetate esters (except ethyl acetate), most of the volatile fatty acids, a few ethyl esters and β-damascenone but increased some primary aromas in wines due to the presence of their aroma precursors in skins. Hence, these results indicate that grape pomace may bind or delay the release of some aroma compounds and/or lose these compounds during cap management in GJ-P and MJ-P treatments compared to the respective juice treatments.

Production of Siamenoside I and Mogroside IV from Siraitia grosvenorii Using Immobilized β-Glucosidase

Siraitia grosvenorii is a type of fruit used in traditional Chinese medicine. Previous studies have shown that the conversion of saponins was often carried out by chemical hydrolysis, which can be problematic because of the environmental hazards it may cause and the low yield it produces. Therefore, the purpose of this study is to establish a continuous bioreactor with immobilized enzymes to produce siamenoside I and mogroside IV. The results show that the immobilization process of β-glucosidase exhibited the best relative activity with a glutaraldehyde (GA) concentration of 1.5%, carrier activation time of 1 h and binding enzyme time of 12 h. After the immobilization through GA linkage, the highest relative activity of β-glucosidase was recorded through the reaction with the substrate at 60 °C and pH 5. Subsequently, the glass microspheres with immobilized β-glucosidase were filled into the reactor to maintain the optimal active environment, and the aqueous solution of Siraitia grosvenorii extract was introduced by controlling the flow rate. The highest concentration of siamenoside I and mogroside IV were obtained at a flow rate of 0.3 and 0.2 mL/min, respectively. By developing this immobilized enzyme system, siamenoside I and mogroside IV can be prepared in large quantities for industrial applications.

Genetic architecture of berry aroma compounds in a QTL (quantitative trait loci) mapping population of interspecific hybrid grapes (Vitis labruscana × Vitis vinifera)

BACKGROUND

Although grapes accumulate diverse groups of volatile compounds, their genetic regulation in different cultivars remains unelucidated. Therefore, this study investigated the volatile composition in the berries of an interspecific hybrid population from a Vitis labruscana 'Campbell Early' (CE) × Vitis vinifera 'Muscat of Alexandria' (MA) cross to understand the relationship among volatile compounds and their genetic regulation. Then, a quantitative trait locus (QTL) analysis of its volatile compounds was conducted.

RESULTS

While MA contained higher concentrations of monoterpenes and norisoprenoids, CE contained higher concentrations of C6 compounds, lactones and shikimic acid derivatives, including volatiles characteristic to American hybrids, i.e., methyl anthranilate, o-aminoacetophenone and mesifurane. Furthermore, a cluster analysis of volatile profiles in the hybrid population discovered ten coordinately modulated free and bound volatile clusters. QTL analysis identified a major QTL on linkage group (LG) 5 in the MA map for 14 monoterpene concentrations, consistent with a previously reported locus. Additionally, several QTLs detected in the CE map affected the concentrations of specific monoterpenes, such as linalool, citronellol and 1,8-cineol, modifying the monoterpene composition in the berries. As for the concentrations of five norisoprenoids, a major common QTL on LG2 was discovered first in this study. Several QTLs with minor effects were also discovered in various volatile groups, such as lactones, alcohols and shikimic acid derivatives.

CONCLUSIONS

An overview of the profiles of aroma compounds and their underlying QTLs in a population of interspecific hybrid grapes in which muscat flavor compounds and many other aroma compounds were mixed variously were elucidated. Coordinate modulation of the volatile clusters in the hybrid population suggested an independent mechanism for controlling the volatiles of each group. Accordingly, specific QTLs with significant effects were observed for terpenoids, norisoprenoids and some volatiles highly contained in CE berries.

Preliminary Studies on Endotherapy Based Application of Ozonated Water to Bobal Grapevines: Effect on Wine Quality

The application of ozonated water in the vineyard is an increasingly popular tool for disease management, but the quality of grapes and resulting wines is likely to be affected. Endotherapy, or trunk injection, is a particularly useful method to apply phytosanitary products since many fungal pathogens colonize the grapevine woody tissues. Thus, the present study aimed to evaluate the effect on wine quality of the ozonated water applied to Bobal grapevines, one of the most cultivated red varieties in Spain, through endotherapy (E) or its combination with spraying (E + S). Endotherapy was carried out four times before harvest for both E and E + S treatments, and spraying was performed 2 days before and after each endotherapy application. Grapes were harvested, vinified, and the quality of the finished wines was evaluated through several enological parameters and the phenolic and volatile composition. Both treatments resulted in less alcoholic and more acidic wines. The E treatment, although it reduced the content of phenolic acids, stilbenes and flavanols, significantly increased anthocyanins, whereas E + S decreased the overall amount of phenolics, which had different implications for wine colour. In terms of aroma, both treatments, but E to a greater extent, reduced the content of glycosylated precursors and differentially affected free volatiles, both varietal and fermentative. Thus, the dose of ozonated water, frequency and/or method of application are determining factors in the effect of these treatments on wine quality and must be carefully considered by winegrowers to establish the optimum treatment conditions so as not to impair the quality of wines.

Free and glycosylated aroma compounds in grapes monitored by solid-liquid extraction and dispersive liquid-liquid microextraction combined with gas chromatography-mass spectrometry

Fifteen aroma compounds have been determined in their free and glycosylated forms in grapes using dispersive liquid‐liquid microextraction with gas chromatography‐mass spectrometry. The sample treatment includes a previous solid‐liquid extraction stage and subsequent parallel microextraction approaches to preconcentrate total aroma content and the free fraction. Thus, the extraction of the total content of analytes requires previous enzymatic hydrolysis of the bound forms. For preconcentration, chloroform (250 μl) and acetonitrile (1.5 ml) were added to 10 ml of the sample extract in the presence of 0.5 g sodium chloride. The absence of matrix effect in the samples allowed quantification against aqueous external standards. Limits of detection ranged between 5 and 30 ng/g, depending on the compound. Method accuracy was studied through recovery assays, with recoveries in the 82–115% range being obtained. Relative standard deviations for repeatability studies were lower than 12%. Four different samples of grapes were analyzed, being quantified linalool in its free form at concentrations in the 359–470 ng/g range, and benzyl alcohol, 2‐phenylethanol, and linalool oxide I and II in their bound forms between 52 and 464 ng/g.

Chemical and Sensory Characteristics of Fruit Juice and Fruit Fermented Beverages and Their Consumer Acceptance

Recent social, economic, and technological evolutions have impacted consumption habits. The new consumer is more rational, more connected and demanding with products, more concerned with the management of the family budget, with the health, origin, and sustainability of food. The food industry over the last few years has shown remarkable technological and scientific evolution, with an impact on the development and innovation of new products using non-thermal processing. Non-thermal processing technologies involve methods by which fruit juices receive microbiological inactivation and enzymatic denaturation with or without the direct application of low heat, thereby lessening the adverse effects on the nutritional, bioactive, and flavor compounds of the treated fruit juices, extending their shelf-life. The recognition of the nutritional and protective values of fruit juices and fermented fruit beverages is evident and is attributed to the presence of different bioactive compounds, protecting against chronic and metabolic diseases. Fermentation maintains the fruit's safety, nutrition, and shelf life and the development of new products. This review aims to summarize the chemical and sensory characteristics of fruit juices and fermented fruit drinks, the fermentation process, its benefits, and its effects.

Enzymatic Characterization of Purified β-Glucosidase from Non-Saccharomyces Yeasts and Application on Chardonnay Aging

The application of β-glucosidase from non-Saccharomyces yeasts to improve wine aroma has been widely explored. However, few enzymes are active under the severe conditions of wine aging (high ethanol concentration, low temperature, and low pH). Therefore, the application of β-glucosidase in wine aging needs further research. In this study, the β-glucosidases Mg-βgl and Hu-βgl extracted from Meyerozyma guilliermondii NM218 and Hanseniaspora uvarum BF345 were purified and used in young Chardonnay wines aged for 50 days. The enzyme activity of the two enzymes was measured. The effects of the two enzymes and a commercial β-glucosidase (An-βgl) on the volatile composition and sensory quality of the wine were also determined. The results showed that Mg-βgl and Hu-βgl had high specific activity of 1.95 U/mg and 2.11 U/mg, respectively, maintaining the activity of 70–80% at 20 °C, pH of 3.0–4.0, and 15% ethanol, corresponding to wine aging conditions. Analysis of volatiles with GC-MS showed a 65–70% increase in total terpenoids and new detection of C13-norisoprenoids when the wines were treated with the three β-glucosidases. In addition, wines treated with Mg-βgl and Hu-βgl had more hexanol, phenylethanol, ethyl octanoate, ethyl heptanoate, and ethyl caprate than wines treated without and with An-βgl. In sensory analysis, the judges showed a greater preference for Hu-βgl-treated wines, to which they attributed pleasant sweet, floral, honey, pomelo, and banana aromas. The results of this study not only offer a way to improve flavor complexity in wine but also provide a reference for the use of other edible sources of β-glucosidase in wine aging.

Valorization of Kiwi Peels: Fractionation, Bioactives Analyses and Hypotheses on Complete Peels Recycle

Kiwi fruit samples (Actinidia deliciosa Planch, cv. Hayward) represent a suitable and good source for fibers obtainment as well as for polyphenolic and carotenoid extraction. With this aim, in this study they were submitted to a double phase extraction to separate insoluble fibers by an organic phase containing lipophilic substances and an hydroalcoholic phase containing polyphenols and soluble fibers. Insoluble fibers could be separated by filtration and sent to be micronized and reused. Hydroalcoholic fractions were then furtherly fractionated by solid-phase extraction. Data coming from the color CIEL*a*b* and the HPLC-DAD analyses of the extracts were compared and correlate with those coming from the SPME-GC/MS analysis of either the finely shredded peels or of the extracts. The obtained extracts were also submitted to anti-radical activity evaluation and anti-Candida activity. Results show that all of the obtained residues are value added products. Hypotheses were also made about the nature and the possible recycle of the obtained purified solid residue.

Comparative Investigations on Different β-Glucosidase Surrogate Substrates

β-glucosidases are hydrolyzing enzymes which can release many aroma-active compounds from their glycoside form. Several yeasts produce these enzymes and thus are applied during the wine production process. To be able to test specific organisms for the presence of β-glucosidases and to investigate this enzyme activity, four main surrogate substrates have been described. The properties and applicability of these compounds, named arbutin (hydroquinone-β-D-glucopyranoside), esculin (6-O-(-D-glucosyl)aesculetin), 4-nitrophenyl-β-D-glucopyranoside (pNPG) and 4-methylumbelliferyl-β-D-glucopyranoside (4-MUG), are discussed after comparing their advantages and disadvantages. Although all four substrates were found suitable for photometric assays, 4-MUG has proven to be most appropriate due to high sensitivity, high robustness and simple processing. Furthermore, the investigation of β-glucosidase product accumulation is described, which could be used to give indications about β-glucosidase localization.

Localization, purification, and characterization of a novel β-glucosidase from Hanseniaspora uvarum Yun268

β-Glucosidase is a key enzyme that hydrolyzes nonvolatile glycosylated precursors of aroma compounds and enhances the organoleptic quality of wines. In this study, a novel β-glucosidase from Hanseniaspora uvarum Yun268 was localized, purified, and characterized. Results indicated that β-glucosidase activity was mainly distributed within the cells. After purification via ammonium sulfate precipitation combined with chromatography, β-glucosidase specific activity increased 8.36 times, and the activity recovery was 56.90%. The enzyme had a molecular mass of 74.22 kDa. It has a Michaelis constant (K_m ) of 0.65 mmol/L, and a maximum velocity (V_max ) of 5.1 nmol/min under optimum conditions; and K_m of 0.94 mmol/L, and V_max of 2.8 nmol/min under typical winemaking conditions. It exhibited the highest activity at 50°C and pH 5.0 and was stable at a temperature range of 20-80°C and pH range of 3.0-8.0. The enzyme has good tolerance to Fe³⁺ , especially maintaining 93.68% of its activity with 10 mmol/L of Fe³⁺ . Ethanol (<20%) and glucose (<150 g/L) inhibited its activity only slightly. Therefore, β-glucosidase from H. uvarum Yun268 has excellent biochemical properties and a good application potential in winemaking. PRACTICAL APPLICATION: Winemaking is a biotechnological process in which exogenous β-glucosidase is used to overcome the deficiency of endogenous β-glucosidase activity in grapes. By localizing, purifying, and characterizing of β-glucosidase from Hanseniaspora uvarum Yun268, it is expected to reveal its physical and chemical characteristics to evaluate its oenological properties in winemaking. The results may provide the basis for promoting the release of varietal aroma and improving wine sensory quality in the wine industry.

Identification of new glycosidic terpenols and norisoprenoids (aroma precursors) in C. arabica L. green coffee by using a high-resolution mass spectrometry database developed in grape metabolomics

Grape aroma precursors have been extensively studied and many glycosidically-bound terpenols and C₁₃-norisoprenoids were identified. Instead, these compounds were scarcely investigated in green Coffea arabica where just few glycosidic compounds were identified so far. By resorting to knowledge of glycoside aroma precursors in grape and the possibility to identify their structures using a high-resolution mass spectrometry database constructed for grape metabolomics, targeted investigation of glycoside precursors in green C. arabica from different geographical origins, was performed. High linalool hexose-pentose was found in all the investigated samples and hexosyl-pentoside derivatives of geraniol, linalooloxide and another linalool isomer, were identified. Moreover, two putative norisoprenoid glycosides were characterized. β-Damascenone was detected in the volatile fraction of the examined C. arabica coffees only after acid addition, however no signals of β-damascenone glycosides, were found. Findings suggests that this important aroma compound could form by hydrolysis and dehydration of a putative 3-hydroxy-β-damascone glycoside precursor identified for the first time in coffee. Aglycones released during the roasting process contribute to enrich the coffee aroma with their positive sensory notes and the identification of these glycosides can contribute to disclose the coffee biology including biochemical, physiological and genetic aspects.

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Glycoside aroma precursors in green C. arabica coffee are poorly known.

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A grape database was used to investigate aroma precursors in green C. arabica.

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Geraniol and linalooloxide glycosides were identified for first time in coffee.

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Linalool hexosyl-pentoside was particularly abundant in samples from Ethiopia.

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Putative 3-hydroxy-β-damascone and vomifoliol glycosides were characterized.

Characterization of Free and Bound Monoterpene Alcohols during Riesling Fermentation

The isomeric nature of monoterpenyl glycosides makes unambiguous identification of intact glycosides difficult. As a result, it is challenging to relate the changes in free monoterpenol concentrations to the corresponding glycosides during wine fermentation and storage. In this study, we isolated and identified linalool, nerol, and geraniol monoterpenyl glycosides fromVitis viniferacv. Riesling grapes through fractionation followed by acid or enzyme hydrolysis. Changes in the composition of identified monoterpenyl glycosides and their respective free volatiles were then monitored during alcoholic fermentations of Riesling juice with four different yeast strains across two successive years. The relative concentrations of the volatiles were monitored by solid-phase microextraction gas chromatography mass spectrometry, while ultrahigh-performance liquid chromatography quadrupole time-of-flight mass spectrometry was used for intact glycosides. Glycoside hydrolysis during fermentation could be related to relative concentrations of the corresponding free aglycones. However, other sources of free monoterpenols were also observed. Differences in glycoside hydrolysis among yeast strains and across years were observed and may be related to grape maturity and/or nutrient levels.

Structure-function relationship of terpenoid glycosyltransferases from plants

Covering: up to 2021Terpenoids are physiologically active substances that are of great importance to humans. Their physicochemical properties are modified by glycosylation, in terms of polarity, volatility, solubility and reactivity, and their bioactivities are altered accordingly. Significant scientific progress has been made in the functional study of glycosylated terpenes and numerous plant enzymes involved in regio- and enantioselective glycosylation have been characterized, a reaction that remains chemically challenging. Crucial clues to the mechanism of terpenoid glycosylation were recently provided by the first crystal structures of a diterpene glycosyltransferase UGT76G1. Here, we review biochemically characterized terpenoid glycosyltransferases, compare their functions and primary structures, discuss their acceptor and donor substrate tolerance and product specificity, and elaborate features of the 3D structures of the first terpenoid glycosyltransferases from plants.

Effects of Traditional and Modern Post-Harvest Withering Processes on the Composition of the Vitis v. Corvina Grape and the Sensory Profile of Amarone Wines

In the Valpolicella area (Verona, Italy) Vitis vinifera cv. Corvina is the main grape variety used to produce Amarone wine. Before starting the winemaking process, the Corvina grapes are stored in a withering (i.e., dehydrating) warehouse until about 30% of the berry weight is lost (WL). This practice is performed to concentrate the metabolites in the berry and enrich the Amarone wine in aroma and antioxidant compounds. In compliance with the guidelines and strict Amarone protocol set by the Consorzio of Amarone Valpolicella, withering must be carried out by setting the grapes in a suitable environment, either under controlled relative air humidity (RH) conditions and wind speed (WS)—no temperature modification is to be applied—or, following the traditional methods, in non-controlled environmental conditions. In general, the two processes have different dehydration kinetics due to the different conditions in terms of temperature, RH, and WS, which affect the accumulation of sugars and organic acids and the biosynthesis of secondary metabolites such as stilbenes and glycoside aroma precursors. For this study, the two grape-withering processes were carried out under controlled (C) and non-controlled (NC) conditions, and the final compositions of the Corvina dried grapes were compared also to evaluate the effects on the organoleptic characteristics of Amarone wine. The findings highlighted differences between the two processes mainly in terms of the secondary metabolites of the dried grapes, which affect the organoleptic characteristics of Amarone wine. Indeed, by the sensory evaluation, wines produced by adopting the NC process were found more harmonious, elegant, and balanced. Finally, we can state how using a traditional system, grapes were characterised by higher levels of VOCs (volatile compounds), whilst wines had a higher and appreciable complexity and finesse.

Contribution of Grape Skins and Yeast Choice on the Aroma Profiles of Wines Produced from Pinot Noir and Synthetic Grape Musts

The aroma profile is a key component of Pinot noir wine quality, and this is influenced by the diversity, quantity, and typicity of volatile compounds present. Volatile concentrations are largely determined by the grape itself and by microbial communities that produce volatiles during fermentation, either from grape-derived precursors or as byproducts of secondary metabolism. The relative degree of aroma production from grape skins compared to the juice itself, and the impact on different yeasts on this production, has not been investigated for Pinot noir. The influence of fermentation media (Pinot noir juice or synthetic grape must (SGM), with and without inclusion of grape skins) and yeast choice (commercial Saccharomyces cerevisiae EC1118, a single vineyard mixed community (MSPC), or uninoculated) on aroma chemistry was determined by measuring 39 volatiles in finished wines using headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography–mass spectrometry (GC-MS). Fermentation medium clearly differentiated the volatile profile of wines with and without yeast, while differences between EC1118 and MSPC wines were only distinct for Pinot noir juice without skins. SGM with skins produced a similar aroma profile to Pinot noir with skins, suggesting that grape skins, and not the pulp, largely determine the aroma of Pinot noir wines.

Beta-glucosidase activity of wine yeasts and its impacts on wine volatiles and phenolics: A mini-review

Beta-glucosidase is an important enzyme for the hydrolysis of grape glycosides in the course of winemaking. Yeasts are the main producers of β-glucosidase in winemaking, therefore play an important role in determining wine aroma and flavour. This article discusses common methods for β-glucosidase evaluation, the β-glucosidase activity of different Saccharomyces and non- Saccharomyces yeasts and the influences of winemaking conditions, such as glucose and ethanol concentration, low pH environment, fermentation temperature and SO₂ level, on their activity. This review further highlights the roles of β-glucosidase in promoting the release of free volatile compounds especially terpenes and the modification of wine phenolic composition during the winemaking process. Furthermore, this review proposes future research direction in this area and guides wine professionals in yeast selection to improve wine quality.

Glycosidically-Bound Volatile Phenols Linked to Smoke Taint: Stability during Fermentation with Different Yeasts and in Finished Wine

When wine grapes are exposed to smoke, there is a risk that the resulting wines may possess smoky, ashy, or burnt aromas, a wine flaw known as smoke taint. Smoke taint occurs when the volatile phenols (VPs) largely responsible for the aroma of smoke are transformed in grape into a range of glycosides that are imperceptible by smell. The majority of VP-glycosides described to date are disaccharides possessing a reducing β-d-glucopyranosyl moiety. Here, a two-part experiment was performed to (1) assess the stability of 11 synthesized VP-glycosides towards general acid-catalyzed hydrolysis during aging, and (2) to examine whether yeast strains differed in their capacity to produce free VPs both from these model glycosides as well as from grapes that had been deliberately exposed to smoke. When fortified into both model and real wine matrices at 200 ng/g, all VP-disaccharides were stable over 12 weeks, while (42–50 ng/g) increases in free 4-ethylphenol and p-cresol were detected when these were added to wine as their monoglucosides. Guaiacol and phenol were the most abundantly produced VPs during fermentation, whether originating from natural VP-precursors in smoked-exposed Pinot Noir must, or due to fortification with synthetic VP-glycosides. Significant yeast strain-specific differences in glycolytic activities were observed for phenyl-β-d-glycopyranoside, with two strains (RC212 and BM45) being unable to hydrolyze this model VP, albeit both were active on the guaiacyl analogue. Thus, differences in Saccharomyces cerevisiae β-glucosidase activity appear to be influenced by the VP moiety.

Encapsulation of Combi-CLEAs of Glycosidases in Alginate Beads and Polyvinyl Alcohol for Wine Aroma Enhancement

The aromatic expression of wines can be enhanced by the addition of specific glycosidases, although their poor stability remains a limitation. Coimmobilization of glycosidases as cross-linked enzyme aggregates (combi-CLEAs) offers a simple solution yielding highly stable biocatalysts. Nevertheless, the small particle size of combi-CLEAs hinders their recovery, preventing their industrial application. Encapsulation of combi-CLEAs of glycosidases in alginate beads and in polyvinyl alcohol is proposed as a solution. Combi-CLEAS of β-d-glucosidase and α-l-arabinofuranosidase were prepared and encapsulated. The effects of combi-CLEA loading and particle size on the expressed specific activity (IU/gbiocatalyst) of the biocatalysts were evaluated. Best results were obtained with 2.6 mm diameter polyvinyl alcohol particles at a loading of 60 mgcombi-CLEA/gpolyvinyl alcohol, exhibiting activities of 1.9 and 1.0 IU/gbiocatalyst for β-d-glucosidase and α-l-arabinofuranosidase, respectively. Afterwards, the stability of the biocatalysts was tested in white wine. All the encapsulated biocatalysts retained full activity after 140 incubation days, outperforming both free enzymes and nonencapsulated combi-CLEAs. Nevertheless, the alginate-encapsulated biocatalysts showed a brittle consistency, making recovery unfeasible. Conversely, the polyvinyl-encapsulated biocatalyst remained intact throughout the assay. The encapsulation of combi-CLEAs in polyvinyl alcohol proved to be a simple methodology that allows their recovery and reuse to harness their full catalytic potential.

Oenological Potential of Autochthonous Saccharomyces cerevisiae Yeast Strains from the Greek Varieties of Agiorgitiko and Moschofilero

Nemea and Mantinia are famous wine regions in Greece known for two indigenous grape varieties, Agiorgitiko and Moschofilero, which produce high quality PDO wines. In the present study, indigenous Saccharomyces cerevisiae yeast strains were isolated and identified from spontaneous alcoholic fermentation of Agiorgitiko and Moschofilero musts in order to evaluate their oenological potential. Random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) recovered the presence of five distinct profiles from a total of 430 yeast isolates. The five obtained strains were evaluated at microvinifications trials and tested for basic oenological and biochemical parameters including sulphur dioxide and ethanol tolerance as well as H2S production in sterile grape must. The selected autochthonous yeast strains named, Soi2 (Agiorgitiko wine) and L2M (Moschofilero wine), were evaluated also in industrial (4000L) fermentations to assess their sensorial and oenological characteristics. The volatile compounds of the produced wines were determined by GC-FID. Our results demonstrated the feasibility of using Soi2 and L2M strains in industrial fermentations for Agiorgitiko and Moschofilero grape musts, respectively.

Use of Kluyveromyces marxianus to Increase Free Monoterpenes and Aliphatic Esters in White Wines

An increasing interest in novel wine productions is focused on non-Saccharomyces yeasts due to their potential in improving sensory profiles. Although Kluyveromyces marxianus has been originally isolated from grapes and its enzymatic activities are used in oenology, rarely it has been used as co-starter. The K. marxianus Km L2009 strain has been characterized here and selected as a co-starter both at laboratory- and winery-scale fermentation. The Km L2009 strain showed growth of up to 40 (mg/L) of sulfites and 6% (v/v) of ethanol. Gas chromatographic analysis demonstrates that wines produced by mixed fermentation contain remarkably higher quantities of free monoterpenes and aliphatic esters than wines produced only by commercial strains of Saccharomyces cerevisiae. Differences in the volatile organic compound composition produced sensorially distinct wines. In light of these results, it is possible to state that even within the K. marxianus species it is possible to select strains capable of improving the aromatic quality of wines.