Application of FT-MIR spectroscopy for fast control of red grape phenolic ripening

The content of phenolic compounds determines the state of phenolic ripening of red grapes and is a key criterion in setting the harvest date to produce quality red wines. In this study, the feasibility of Fourier transform mid-infrared (FT-MIR) spectroscopy combined with partial least-squares (PLS) regression to quantify phenolic compounds is reported. The reference methods used for quantifying these compounds (which were evaluated as total phenolic compounds, total anthocyanins, and condensed tannins) were the usual ones used in cellars that employed UV-vis spectroscopy. To take into account the high natural variability of grapes when building the calibration models, fresh grapes from six varieties, at different phenolic ripening states were harvested during three vintages. Destemmed and crushed grapes were subjected to an accelerated extraction process and used as calibration standards. A total of 192 extracts (objects) were obtained, and these were divided into a training set (106 objects) and a test set (86 objects) to evaluate the predictive ability of the models. Among the different MIR regions of the extract raw spectra, those that provided the highest variability on the absorption were selected. The results showed that the best PLS regression model was the one obtained when working in the region of 1168-1457 cm(-1) because it gave the most accurate and robust prediction for total phenolic compounds (RMSEP%=4.3 and RPD=4.5), total anthocyanins (RMSEP%=5.9 and RPD=3.5), and condensed tannins (RMSEP%=5.8 and RPD=3.8). Therefore, it can be concluded that FT-MIR spectroscopy can be a fast and reliable technique for monitoring the phenolic ripening in red grapes during the harvest period.     

Effect of different winemaking technologies on phenolic composition in Tinta Miúda red wines.

The influence of different types of winemaking technology on the contents of catechins, proanthocyanidins, and anthocyanins in Tinta Miúda red wines was studied. The Tinta Miúda red wines were made by fermentation with carbonic maceration, fermentation with stem contact, and fermentation without stem contact, respectively. The analysis of individual catechins, procyanidins, and anthocyanins in these wines was performed by HPLC, and quantification of total catechins, total oligomeric proanthocyanidins, total polymeric proanthocyanidins, and total anthocyanins was carried out by spectrophotometric methods. The wine made by carbonic maceration contained the highest amounts of both catechins and oligomeric and polymeric proanthocyanidins, followed by the wine made by fermentation with stem contact, whereas the wine made by fermentation without stem contact contained the lowest of these compounds. On the other hand, the concentrations of total anthocyanins and nearly all individual anthocyanins in the carbonic maceration wine were lower than those in the wines made by fermentation with stem contact and fermentation without stem contact. These results indicated that, although the carbonic maceration technique could retain higher amounts of catechins and proanthocyanidins in wine, it did not favor retaining or stabilizing anthocyanins in wine.     

Evolution of phenolic compounds and antioxidant activity during malting

Two barley varieties, Gan4 and Hamelin, were malted to investigate the evolution of phenolic compounds and antioxidant activity during malting. The antioxidant activity was evaluated with DPPH radical scavenging activity, ABTS radical cation scavenging activity, reducing power, and metal chelating activity. Results showed that malting had significant influences on individual and total phenolic contents as well as antioxidant activities of two barley varieties. The contents of some phenolic compounds and the antioxidant activities decreased significantly during steeping and the early stages of germination and then increased remarkably during the later stages of germination and subsequent kilning. The most phenolic compounds identified in barley were (+)-catechin and ferulic acid, which both changed significantly during malting. Moreover, results from the Pearson correlation analysis showed that there were good correlations among DPPH radical scavenging activity, ABTS radical cation scavenging activity, reducing power, total phenolic content and sum of individual phenolic contents during malting.     

干红葡萄酒发酵中的固液浸取分析

干红葡萄酒浸取与发酵同时进行.浸取效果直接影响葡萄酒的质量.干红葡萄酒浸取是在特定的浸取剂、特定的颗粒度及固-液比、特定的发酵温度及工艺条件下的浸渍,在整个浸取过程中溶剂对溶质的浸取是一个动态变化过程.为了能够在发酵条件下有利于葡萄中各种有益成分的充分浸取,该文章用工程传质学的理论分析了干红葡萄酒浸取体系,提出了干红葡萄酒体系是由以单宁、天然色素等酚类物质为溶质、以葡萄汁及发酵液为溶剂(浸取剂)、以葡萄果皮、果籽、果梗等为载体组成的三元物系的观点;对浸取剂、溶质及载体进行了分析;结合葡萄酒生产实际,从葡萄原料(品种及果粒大小、成熟)、发酵工艺(浸取温度、浸取时间、发酵液中SO2浓度等)、生产操作因素(葡萄颗粒的破碎程度、外力强化传质措施如搅拌、倒罐)、设备结构(发酵罐长径比等)等方面探讨了影响浸取效果的因素.     

Study of low molecular weight phenolic compounds during the aging of sparkling wines manufactured with red and white grape varieties

Thirty-two phenolic compounds of low molecular weight were identified in 36 white, blanc de noir, and rosé sparkling wines by using HPLC with photodiode array and mass spectrometry detection. Some of the identified compounds, such as cis- and trans-ethylcaftaric, cis- and trans-ethylcaffeic, and cis- or trans-ethyl-p-coumaric acids, 2R,3R-dihydroquercetin, 2R,3R-dihydrokaempferol 3-O-beta-d-glucoside, and a lignan derivative are described for the first time in sparkling wines manufactured with grapes of red varieties. This is also the first time that cis- or trans-diethylfertaric acids have been identified in wines. When cluster analysis was applied to the data of 19 of the 32 identified compounds, the greatest differences found in the low molecular weight phenolic compounds in sparkling wines were due to the grape variety from which they were manufactured, whereas aging time did not significantly influence phenolic composition. Nine phenolic compounds, that is, trans-p-coumaric and trans-caftaric acids, trans-resveratrol glucoside, cis-coutaric, trans-coutaric, cis-p-coumaric, and cis-caftaric acids, tryptophol, and syringic acid, permit the wines to be classified correctly in accordance with the grape variety from which they were manufactured.     

Metabolism of phenolic compounds during loquat fruit development.

Phenolic compounds in loquat fruit were identified as 5-caffeoylquinic acid (chlorogenic acid), neochlorogenic acid, hydroxybenzoic acid, 5-p-feruloylquinic acid, protocatechuic acid, 4-caffeoylquinic acid, epicatechin, o-coumaric acid, ferulic acid, and p-coumaric acid. Neochlorogenic acid was found to be dominant in the early stages of loquat fruit development. Both the concentrations and types of phenolic compounds were high in young fruit but then decreased steadily during growth. However, the concentration of chlorogenic acid increased during ripening and became predominant in ripe fruit. The large rise in chlorogenic acid concentration appears to be a characteristic of loquat fruit ripening. In all of the cultivars tested, the types of phenolic compounds were similar but the total phenolic content varied from 81.8 to 173.8 mg/100 g of fresh pulp. In the biosynthetic pathway of chlorogenic acid, the enzyme activities of phenylalanine ammonia-lyase (PAL), 4-coumarate:CoA ligase (CL), and hydroxycinnamoyl CoA:quinate hydroxycinnamoyl transferase (CQT) were high at the early stage of growth, diminished to low levels approximately 3 weeks prior to harvest, but then rose to a peak at 1 week before harvest. The changes of these enzyme activities seemed to be associated with variations in chlorogenic acid concentration during development, maturation, and ripening of loquat fruit.     

GC-ITMS determination and degradation of captan during winemaking

Captan and its metabolite tetrahydrophthalimide (THPI) were determined in grapes, must, and wine by GC-ITMS. Pesticides were extracted with acetone/petroleum ether (50:50 v/v). Because of the high selectivity of the ITMS detector, no interferent was found and cleanup was not necessary. Recoveries from fortified grapes, must, and wines ranged between 90 and 113% with a maximum coefficient of variation of 11%. Limits of quantitation were 0.01 mg/kg for both compounds. In model systems, captan and its metabolites, THPI, cis-4-cyclohexene-1,2-dicarboxylic acid, and 1,2,3,6-tetrahydrophthalamic acid, were determined by HPLC. The degradation of captan during winemaking was studied. Captan degraded in must, giving 100% THPI, and at the end of fermentation, only THPI was found in wine. The degradation of captan to THPI was due to the acidity in must and wine. This metabolite was present at low levels on grapes, and, unlike captan, it had no negative effect on the fermentative process. Model systems showed that the mechanism of disappearance of captan in grapes was due to photodegradation and codistillation.     

Quantification of phenolic compounds in olive oil mill wastewater by artificial neural network/laccase biosensor

In this paper is considered a new computerized approach to the determination of concentrations of phenolic compounds (caffeic acid and catechol). An integrated artificial neural network (ANN)/laccase biosensor is designed. The data collected (current signals) from amperometric detection of the laccase biosensor were transferred into an ANN trained computer for modeling and prediction of output. Such an integrated ANN/laccase biosensor system is capable of the prediction of caffeic acid and catechol concentrations of olive oil mill wastewater, based on the created models and patterns, without any previous knowledge of this phenomenon. The predicted results using the ANN were compared with the amperometric detection of phenolic compounds obtained at a laccase biosensor in olive oil wastewater of the 2004-2005 harvest season. The difference between the real and the predicted values was <0.5%. biosensor; olive oil mill wastewater; chemical analysis; phenolic compounds.     

Separation, characterization and quantification of phenolic compounds in blueberries and red and black currants by HPLC-DAD-ESI-MSn

The phenolic profile of four blueberry varieties (Vaccinium corymbosum L., cv. Toro, Legacy, Duke and Bluecrop) and two varieties (Rosenthal and Rovada) of red currants (Ribes rubrum L.) and black currants (Ribes nigrum L.) cultivated in Macedonia have been analyzed using HPLC coupled to diode-array detection and tandem mass spectrometry with electrospray ionization. A complex profile of anthocyanins, flavonols, flavan-3-ols and hydroxycinnamic acid derivatives has been assayed in acetone-acetic acid (99:1, v/v) extracts. Anthocyanins comprised the highest content of total phenolic compounds in currants (>85%) and lower and variety dependent in blueberries (35-74%). Hydroxycinnamic acid derivatives comprised 23-56% of total phenolics in blueberries and 1-6% in currants. Chlorogenic acid was the major hydroxycinnamic acid in blueberries, only in the Legacy variety, two malonyl-caffeoylquinic acid isomers were major components. Flavonols, mainly quercetin and myricetin glycosides, were a minor group, but glucosides of laricitrin and syringetin were also detected in the blueberry varieties counting for 10-34% of total flavonols. From flavan-3-ols, catechin was detected in most samples; the dimer B2 was specific for blueberries whereas epigallocatechin was detected in currants.     

Detection of the presence of hazelnut oil in olive oil by FT-raman and FT-MIR spectroscopy

The detection of the presence of refined hazelnut oil in refined olive oil at low percentages is still a challenge with the current official standards. FT-Raman and FT-MIR spectroscopies have been used to determine the level of detection of the presence of hazelnut oil in olive oil. Spectroscopic analysis has been made not only with the entire oil but also with its unsaponifiable matter. Univariate and multivariate statistical models have been designed with this objective. This study shows that a complete discrimination between olive and hazelnut oils is possible and that adulteration can be detected if the presence of hazelnut oil in olive oil is >8% and if the blends are of Turkish olive and hazelnut oils. The limit of detection is higher when the blends are of edible oils from diverse geographical origins.     

Protein-lipid interactions during liposome oxidation with added anthocyanin and other phenolic compounds

Oxidation of bovine serum albumin, casein, and lactalbumin and the effect of different procyanidins, anthocyanins, and their aglycons (10 and 20 microM) on lactalbumin oxidation were investigated in a liposome system. Samples were incubated in the dark at 37 degrees C with copper, and the extent of oxidation was measured by determining the loss of tryptophan fluorescence and the formation of protein carbonyls, conjugated diene hydroperoxides, and hexanal. The correlation between different protein and lipid oxidation measurements was good and statistically significant. Casein was the most stable protein in the liposome model, and it was also the best inhibitor of liposome oxidation. All tested anthocyanins and other phenolic compounds inhibited both lipid and protein oxidation. There were no systematic differences with anthocyanins and their aglycons in relation to the concentrations used or glycosylation with either glucose or rutinose. Procyanidins B1 and B2 and ellagic acid were potentially better antioxidants than anthocyanins due to their several hydroxyl groups as measured by both protein and lipid oxidation. In conclusion, oxidative deterioration of liposomes due to protein-lipid interaction is inhibited by anthocyanins, procyanidins, and ellagitannin present, for example, in berries.     

Changes occurring in phenolic compounds and alpha-tocopherol of virgin olive oil during storage

Changes occurring in the concentrations of alpha-tocopherol, total phenols, and complex phenols linked to 3,4-dihydroxyphenylethanol (fractions FII and FIV) and p-hydroxyphenylethanol (FIII) during storage of virgin olive oil under environmental conditions were studied. Under diffused light, alpha-tocopherol was decomposed by 79% in 4 months, whereas <45% of the phenols were lost during the same period. Among the phenols, FII showed the least stability, and decreased by 72% in 6 months. Total phenols, FIII, and FIV recorded reductions in the range of 57-63% in 6 months. When the oil was stored in the dark, alpha-tocopherol, total phenols, FIII, and FIV exhibited similar profiles of degradation, reducing by 39-45% in the first 6 months and 50-62% in 12 months. FII was the least stable compound in the dark and recorded a loss of 64% in 6 months and 79% in 12 months. The levels of the above antioxidants were further related to peroxide formation. Remaining levels of these compounds at PV = 20 meq/kg ranged between 50 and 73% under diffused light and between 40 and 62% in the dark.     

Estimation of scavenging activity of phenolic compounds using the ABTS(*+) assay

Observations on the applicability of the ABTS(*+) assay to define structure-activity relationships (SARs) among phenols (AH) were based on experimental data and theoretical calculations. All AH examined (hydroxycinnamic derivatives, simple polyphenols, polyhydroxybenzoates, and flavonoids) were found to be active toward ABTS(*+). Moreover, known weak radical scavengers (i.e., coumaric and isoferulic acids) were found to be efficient or comparatively active to caffeic or rosmarinic acids in contradiction to the AH classification based on 1,1-diphenyl-2-picrylhydrazyl (DPPH) data or the bond dissociation enthalpy values. This behavior was observed both in ethanol and in buffered (pH 7.4) environment. Resorcinol and phloroglucin were found to be more active than catechol and hydroquinone, whereas, among polyhydroxybenzoates, 2,4-dihydroxybenzoic acid was the least active, in line with the DPPH and theoretical data. Therefore, it can be argued that the ABTS(*+) assay may give an indication for the presence of antioxidants in a certain system but SARs cannot be readily inferred.     

Rapid method for the discrimination of red wine cultivars based on mid-infrared spectroscopy of phenolic wine extracts

Mid-infrared spectroscopy and UV-vis spectroscopy combined with multivariate data analysis have been applied for the discrimination of Austrian red wines, including the cultivars Cabernet Sauvignon, Merlot, Pinot Noir, Blaufr?nkisch (Lemberger), St. Laurent, and Zweigelt. Both authentic wines and their phenolic extracts were investigated by attenuated total reflectance (ATR)-mid-infrared spectroscopy. Phenolic extracts were also investigated by UV-vis spectroscopy. The wine extracts were obtained by solid-phase extraction with C-18 columns and elution by methanol containing 0.01% hydrochloric acid. Hierarchical cluster analysis was performed with mid-infrared spectra of both wines and extracts, as well as with UV-vis spectra of the phenolic extracts. Data processing involved vector normalization and derivation of the spectra. Due to varying concentrations of main components including sugar and organic acids, satisfactory classification of untreated wines was not achieved. However, when using mid-infrared spectra of the phenolic extracts, almost complete discrimination of all cultivars investigated was achieved. The use of UV-vis spectroscopy for cultivar discrimination was found to be limited to the authentication of the Burgundy species Pinot Noir. In addition, soft independent modeling of class analogy was applied to the mid-infrared spectra of the extracts. It was possible to establish class models for five different wine cultivars and to classify test samples correctly.     

Effect of some phenolic compounds and beverages on pepsin activity during simulated gastric digestion

The effect of some polyphenols (resveratrol, catechin, epigallocatechin-3-gallate, and quercetin) and beverages (red wine and green tea) on the enzymatic activity of pepsin during the digestion of three different substrates (pork meat, insoluble azocasein, and denatured hemoglobin) has been investigated. The tested polyphenols and beverages increase the initial velocity of the reaction, and the activating effect is concentration dependent. The order of effectiveness of polyphenols in increasing the initial velocity of the reaction is resveratrol > or = quercetin > epigallocatechin-3-gallate > catechin. The kinetic data obtained with soluble denatured hemoglobin show that the K(m) for the substrate is not changed, whereas the V(max) of the reaction is increased. Pepsin activity follows a simple Michaelis-Menten kinetic suggesting that k(3) is increased by polyphenols. To the authors' knowledge, the present study is the first demonstration that some polyphenols and related beverages are able to enhance the enzymatic activity of pepsin.     

Evolution of phenolic compounds during an experimental aging in wood of Sherry vinegar

Changes in the physicochemical composition of wine vinegars produced by submerged culture system and aged in wood were followed. Five Sherry wine vinegars and a model vinegar solution were aged in six new American oak butts of 16.6 L capacity. A total of 24 phenolic compounds were monitored during the maturation study (24 months), along with other physicochemical parameters (total extract, acidity, residual alcohol and total phenolic index). Multivariate statistical analysis was applied to the data. From the sixth month on, significant changes were produced in most of the phenolic compounds, mainly aromatic aldehydes and 5-(hydroxymethyl)-2-furaldehyde. When all the phenolic compounds were considered as variables, cluster analysis grouped samples according to the wine substrate employed in the elaboration of vinegars under study. Within each subcluster, samples are arranged according to their aging status when phenolic compounds accounting significative changes at 180 days of aging are considered. Discriminant functions were constructed from the phenolic compounds data set. The validity of these functions was tested using 13 samples of aged commercial Sherry wine vinegars and 25 unaged vinegars. A total of 97.4% of the test samples was correctly classified within its respective group.     

Biological activity of acetylated phenolic compounds

In recent years an effort has been made to isolate and identify biologically active compounds that are included in the Mediterranean diet. The existence of naturally occurring acetylated phenolics, as well as studies with synthetic ones, provide evidence that acetyl groups could be correlated with their biological activity. Platelet activating factor (PAF) is implicated in atherosclerosis, whereas its inhibitors seem to play a protective role against cardiovascular disease. The aim of this study was to examine the biological activity of resveratrol and tyrosol and their acetylated derivatives as inhibitors of PAF-induced washed rabbit platelet aggregation. Acetylation of resveratrol and tyrosol was performed, and separation was achieved by HPLC. Acetylated derivatives were identified by negative mass spectrometry. The data showed that tyrosol and its monoacetylated derivatives act as PAF inhibitors, whereas diacetylated derivatives induce platelet aggregation. Resveratrol and its mono- and triacetylated derivatives exert similar inhibitory activity, whereas the diacetylated ones are more potent inhibitors. In conclusion, acetylated phenolics exert the same or even higher antithrombotic activity compared to the biological activity of the initial one.     

Effect of enzyme treatment during mechanical extraction of olive oil on phenolic compounds and polysaccharides

The effect of the use of cell-wall-degrading-enzyme preparations during the mechanical extraction process of virgin olive oil on the phenolic compounds and polysaccharides was investigated. The use of the enzyme preparations increased the concentration of phenolic compounds in the paste, oil, and byproducts. Especially, the contents of secoiridiod derivatives such as the dialdehydic form of elenolic acid linked to 3,4-dihydroxyphenylethanol (3,4-DHPEA-EDA) and an isomer of oleuropein aglycon (3,4-DHPEA-EA), which have high antioxidant activities, increased significantly in the olive oil. Furthermore, the use of an N(2) flush during processing strongly increased the phenolic concentration. Analyses of the pectic polymers present in the paste showed that the use of pectinolytic enzyme preparations increased the yield of the buffer soluble pectins and the proportion of molecules with a lower molecular mass. Also, the content of uronic acids in the buffer soluble extract increased considerably due to the use of the enzyme preparations. Analysis of the polymeric carbohydrates in the vegetation waters showed the presence of mainly pectic polymers. The addition of commercial enzyme preparations increased the uronic acid content of the polysaccharides in the vegetation water substantially compared to the blank. This study showed that the addition of cell-wall-degrading enzymes did improve the olive oil quality; however, mechanisms remained unclear.     

Influence of micro-oxygenation treatment before oak aging on phenolic compounds composition, astringency, and color of red wine

Micro-oxygenation is usually applied to red wines as a cheaper alternative to oak aging. It has been suggested, however, that micro-oxygenation can also be used to complement oak aging in order to improve the quality of very astringent and herbaceous red wines. In this paper we study how applying the micro-oxygenation technique before oak aging affects the composition and quality of astringent red wines. When this technique is applied prior to oak aging, the wines have a slightly less intense red color and significantly higher levels of combined and free anthocyanins and ethyl-bridged anthocyanin-flavanol pigments. On the other hand, no differences in other newly formed pigments are found. Applying micro-oxygenation before oak aging does not affect the total proanthocyanidin concentration, but it produces wines with a slightly (though significantly) higher mean degree of proanthocyanidin polymerization and a drastically lower astringency. These wines also present a clearer impact of wood aromas.