Phenolic Compounds In Fruits Research Articles

A targeted metabolomics approach to understand differences in flavonoid biosynthesis in red and yellow raspberries

Phenolic compounds account for the most important class of secondary metabolites in raspberries and fulfill a broad range of biological functions in plants. Due to their presence in fruits they are also considered as important bioactive compounds in human nutrition and are closely related to fruit quality. In the present study a targeted UPLC-MS/MS method was used to screen various phenolic compounds in fruits of red and yellow raspberry cultivars. In total 50 phenolic compounds were detected above the quantification limit. Beside the obvious lack of anthocyanins, all yellow fruits analysed here lack procyanidin B1. The presence of this dimer, along with B3 dimers is described for the first time in raspberry fruits. Also for the first time, dihydrochalcone and stilbene derivatives and the quercetin metabolite, isorhamnetin with its glycosides, were identified in considerable concentrations in raspberries. Based on a PCA plot the red cultivar "Heritage" and the yellow "Alpen Gold" could clearly be separated from the other tested cultivars due to their distinct metabolite profiles/concentrations. This study allowed to obtain a comprehensive profile of the phenolic composition of the different raspberry varieties. The obtained data will lead to a better understanding of the overall biosynthetic network of polyphenols in raspberry and will help to explain responsible factors for the different metabolite profiles in ongoing studies.

Antiproliferative and cytotoxic effects of purple pitanga (Eugenia uniflora L.) extract on activated hepatic stellate cells

The presence of phenolic compounds in fruit- and vegetable-rich diets has attracted researchers' attention due to their health-promoting effects. The objective of this study was to evaluate the effects of purple pitanga (Eugenia uniflora L.) extract on cell proliferation, viability, mitochondrial membrane potential, cell death and cell cycle in murine activated hepatic stellate cells (GRX). Cell viability by 3-(4,5-dimethylthiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay was significantly decreased on cells treated with 50 and 100 µg ml(-1) of purple pitanga extract for 48 and 72 h, and the percentage of dead cell stained with 7-amino-actinomycin D was significantly higher in treated cells. The reduction of cell proliferation was dose dependent, and we also observed alterations on cell cycle progression. At all times studied, GRX cells treated with 50 and 100 µg ml(-1) of purple pitanga showed a significant reduction in cellular mitochondrial content as well as a decrease in mitochondrial membrane potential. Furthermore, our results indicated that purple pitanga extract induces early and late apoptosis/necrosis and necrotic death in GRX cells. This is the first report describing the antiproliferative, cytotoxic and apoptotic activity for E. uniflora fruits in hepatic stellate cells. The present study provides a foundation for the prevention and treatment of liver fibrosis, and more studies will be carried to elucidate this effect.

Use of image analysis to estimate anthocyanin and UV-excited fluorescent phenolic compound levels in strawberry fruit

Strawberry is rich in anthocyanins, which are responsible for the red color, and contains several colorless phenolic compounds. Among the colorless phenolic compounds, some, such as hydroxycinammic acid derivatives, emit blue-green fluorescence when excited with ultraviolet (UV) light. Here, we investigated the effectiveness of image analyses for estimating the levels of anthocyanins and UV-excited fluorescent phenolic compounds in fruit. The fruit skin and cut surface of 12 cultivars were photographed under visible and UV light conditions; colors were evaluated based on the color components of images. The levels of anthocyanins and UV-excited fluorescent compounds in each fruit were also evaluated by spectrophotometric and high performance liquid chromatography (HPLC) analyses, respectively and relationships between these levels and the image data were investigated. Red depth of the fruits differed greatly among the cultivars and anthocyanin content was well estimated based on the color values of the cut surface images. Strong UV-excited fluorescence was observed on the cut surfaces of several cultivars, and the grayscale values of the UV-excited fluorescence images were markedly correlated with the levels of those fluorescent compounds as evaluated by HPLC analysis. These results indicate that image analyses can select promising genotypes rich in anthocyanins and fluorescent phenolic compounds.

Phenolic Characterization of Sicilian Yellow Flesh Peach (Prunus persicaL.) Cultivars at Different Ripening Stages

AbstractYellow flesh peaches (Prunus persica L.) from different Sicilian areas (Leonforte, Riesi and Maniace) were investigated for the first time for their polyphenolic composition, with consideration of both peel and flesh tissues. The qualitative and quantitative polyphenolic evaluation was determined at two different maturity stages (commercial and postharvest ripening) via chromatographic separation by using reverse‐phase HPLC‐PDA‐ESI/MS 2. This technique provides a comprehensive chromatographic evaluation of 10 compounds (hydroxycinnamates and flavonols), differently distributed in the analyzed tissues. Overall, the hydroxycinnamates were present in both pulp and peel, while flavonols resulted exclusively located in the peel. Peels were found to be richest in polyphenolics with respect to the pulps, containing up to 276 mg/kg fresh weight in Riesi commercial‐ripe peaches. Generally, the peach tissues from commercial‐ripe fruits showed higher phenolics contents than postharvest‐ripe fruits.Practical ApplicationsIt is well documented that the benefits due to the consumption of fruit can be largely attributed to the elevated content of phenolic compounds. High levels of phenolic compounds in fruits are of high importance to maintain the quality of fruits and provide consumers the health benefits of fruit consumption. Thus, the assessment of the distribution of phenolic compounds in various parts of the peach fruit and any variations due at the time of collection are considered interesting from a scientific point of view. The characterization of peach phenolics could represent a useful tool in the area of food authenticity protection since some compounds could represent specific quality markers. Moreover, a study on phenolics quantification at different ripening stages could provide useful information for assessing the fruit harvest timing in order to ensure the best fruit quality.

Phenolic compounds in fruits – an overview

SummaryPhenolic compounds are secondary metabolites widely found in fruits, mostly represented by flavonoids and phenolic acids. The growing interest in these substances is mainly because of their antioxidant potential and the association between their consumption and the prevention of some diseases. The health benefits of these phytochemicals are directly linked to a regular intake and their bioavailability. Studies have shown the importance of the regular consumption of fruits, especially for preventing diseases associated with oxidative stress. In the present review, the most recent articles dealing with polyphenols in fruits are reviewed, focusing on their occurrence, main methods of extraction, quantification and antioxidant assays. In addition, the health benefits and bioaccessibility/bioavailability of phenolic compounds in fruits are addressed.

Free Radical-Scavenging Properties and Antioxidant Activity of Fractions from Cranberry Products

Lipid peroxidation inhibition capacity and antiradical activity were evaluated in HPLC fractions of different polarity obtained from two cranberry juices and three extracts isolated from frozen cranberries and pomace containing antho-cyanins, water-soluble and apolar phenolic compounds, respectively. Compounds with close polarities were collected to obtain between three and four fractions from each juice or extract. The cranberry phenols are good free radi-cal-scavengers, but they were less efficient at inhibiting the lipid peroxidation. Of all the samples tested, the intermediate polarity fraction of extract rich in apolar phenolic compounds of fruit presented the highest antiradical activity while the most hydrophobic fractions of the anthocyanin-rich extract from fruit and pomace appeared to be the most efficient at inhibiting the lipid peroxidation. The antioxidant or pro-oxidant activity of fractions increased with the con-centration. The phenol polarity and the technological process to manufacture cranberry juice can influence the antioxidant and antiradical activities of fractions.

Phenolic compounds in strawberry (Fragaria x ananassa Duch.) fruits: Composition in 27 cultivars and changes during ripening

Phenolic compounds in fruits of 27 cultivars of strawberry (Fragaria x ananassa Duch.) grown in Norway were characterised and quantified by HPLC-DAD-MSn. Total phenolic content, calculated as the sum of the individual compounds, varied 2.3-fold among cultivars, i.e., from 57 to 133mg/100g of fw. There were significant differences among cultivars in concentration of all phenolic compounds. The highest variation between cultivars was found for cinnamoyl glucose (0.6–24.9mg/100g of fw). Concentration of anthocyanins, the most abundant class of phenolic compounds in the majority of the cultivars, varied from 8.5 to 65.9mg/100g of fw. Flavan-3-ols (11–45mg/100g of fw) and ellagitannins (7.7–18.2mg/100g of fw) contributed on average 28% and 14% to total phenolic contents in the strawberry cultivars, respectively. In three cultivars harvested at three stages of ripeness, anthocyanins and cinnamic acid conjugates were the compounds most affected by ripening. The anthocyanin profile for the individual cultivars was only slightly affected by ripening and growing conditions.

Analysis by High-Performance Liquid Chromatography Diode Array Detection Mass Spectrometry of Phenolic Compounds in Fruit of Eucalyptus globulus Cultivated in Algeria

A method based on high-performance liquid chromatography coupled with diode array detection and electrospray ionization mass spectrometry (HPLC-DAD-ESI-MS) following fractionation by chromatography on a Sephadex LH-20 column has been developed to determine the phenolic composition of fruit of Eucalyptus globulus growing in Algeria. The presence of 18 gallotannins, 26 ellagitannins, and 2 flavonols was established. Tentative identification is provided for these compounds on the basis of UV-visible spectra and mass spectrometry data. Most compounds described in this study have not previously detected in fruit of E. globulus. Moreover, this is the first report of methyl digalloyl diglucose, 3,3'-O-dimethylellagic acid 4-O-β-glucopyranoside, ellagic acid hexose, methyl ellagic acid pentose, methyltetragalloylglucose, and valoneic acid isomers (sanguisorbic, flavogallic acid dilactone) in the genus Eucalyptus. Quantitatively, ellagic acid and its derivatives, including ellagitannins, are largely predominant.

Postprandial metabolic events and fruit-derived phenolics: a review of the science

There is increasing evidence that the postprandial state is an important contributing factor to chronic disease. The role of fruit phenolic compounds to protect health and lower disease risk through their actions in mitigating fed-state metabolic and oxidative stressors is of interest and the topic of the present paper. Two main questions are posed: first, what is the role of plant foods, specifically fruits rich in complex and simple phenolic compounds in postprandial metabolic management; and second, does the evidence support consuming these fruits with meals as a practical strategy to preserve health and lower risk for disease? This review provides an overview of the postprandial literature, specifically on the effect of fruits and their inherent phenolic compounds in human subjects on postprandial lipaemia, glycaemia/insulinaemia and associated events, such as oxidative stress and inflammation. Among the identified well-controlled human trials using a postprandial paradigm, >50% of the trials used wine or wine components and the remaining used various berries. Notwithstanding the need for more research, the collected data suggest that consuming phenolic-rich fruits increases the antioxidant capacity of the blood, and when they are consumed with high fat and carbohydrate 'pro-oxidant and pro-inflammatory' meals, they may counterbalance their negative effects. Given the content and availability of fat and carbohydrate in the Western diet, regular consumption of phenolic-rich foods, particularly in conjunction with meals, appears to be a prudent strategy to maintain oxidative balance and health.

Determination of oil palm fruit phenolic compounds and their antioxidant activities using spectrophotometric methods

SummaryThere is scarce information on the phenolics of oil palm fruits (Elaeis guineensis). In this study, phenolics were extracted from oil palm fruits and analysed using spectrophotometry for information on the different types of palm phenolics and their antioxidative activities. Analyses of the total phenolic content (TPC), total flavonoid content (TFC), o‐diphenols index, hydroxycinnamic acid index, flavonols index and phenol index showed ranges between 5.64 and 83.97 g L−1 gallic acid equivalent (GAE), 0.31–7.53 g L−1 catechin equivalent, 4.90–93.20 g L−1 GAE, 23.74–77.46 g L−1 ferulic acid equivalent, 3.62–95.33 g L−1 rutin equivalent and 15.90–247.22 g L−1 GAE, respectively. The antioxidant assay, 2,2‐diphenyl‐2‐picrylhydrazyl radical scavenging assay, showed antioxidative activities in all the extracts with results ranging from 4.41 to 61.98 g L−1 trolox equivalent. The high antioxidant activities of the oil palm fruit phenolics were also found to increase with increasing TPC and TFC.

Influence of pre-harvest ozone exposure on quality of strawberry fruit under simulated retail conditions

Strawberries ( Fragaria × ananassa Duch.) were grown under an ozone-enriched atmosphere, and fruit yield, quality, and postharvest behavior under simulated retail storage conditions were investigated. The more ozone sensitive cv. Korona and the less sensitive cv. Elsanta, according to previous studies, were exposed for 2 months to 156 μg m −3 ozone on average, or air without ozone, in controlled-environment chambers. The influence of ozone depended significantly on the cultivar and its susceptibility to oxidative stress. Generally, ozone decreased the contents of ascorbic acid, caused higher lipid peroxidation and lowered sweetness of the fruit. In the case of lipid peroxidation, the effect was strengthened under retail conditions. The ozone stress did not influence yield, size, antioxidative capacity, anthocyanins, or phenolic compounds of fruit. In the more sensitive cv. Elsanta, ozone-induced sepal injuries were detected and the appearance of fruit was thus impaired; glutathione content of fruit also decreased. In contrast, fruit quality of the less sensitive cv. Korona remained almost constant. In general, retail conditions impaired quality of strawberry fruit and in the case of an effect on quality by ozone during fruit development, quality was slightly worse after storage due to the high perishability of the strawberry fruit.

Changes of antioxidant activity and total phenolic compounds during storage of selected fruits

The antioxidant activity and total phenolic compounds in various fruits (common fruits—two varieties of mangoes (ripe and unripe), guava, papaya, mangosteen and banana; and two indigenous fruits—makiang and maluod) were investigated. Banana and papaya showed the lowest activity, and mangosteen, mango and guava exhibited high levels of antioxidant activity (oxygen radical absorbance capacity (ORAC), and ferric-reducing antioxidant power (FRAP)) as well as total phenolic compounds. The studied indigenous fruits (makiang and maluod) are high in both antioxidant activity (ORAC and FRAP) and total phenolic compounds. Three independent batches of selected fruits—guava ( Psidium guajava), makiang ( Cleistocalyx nervosum var paniala) and maluod ( Elaeagnus iatifolia, Linn)—were used to determine the changes in antioxidant activity (AO) and total phenolic compounds (TP) during storage at −20 °C for 3 months and at 5 °C for 10 days. The ORAC-AO during storage at −20 °C for 2 wk decreased significantly in homogenised guava (23%) and in whole fruits of maluod (62%), whereas that of makiang was constant. A continuous decrease in TP was found in homogenised guava throughout the 3-months storage period (69% retention) whereas constant levels were found in other fruits. At 5 °C, a decrease in the ORAC-AO in the whole fruits of makiang (14%) and maloud (70%) was found after a 3-days storage, whereas a gradual increase in the activity (120–190%) was found in the whole fruit of guava throughout the storage period. Among the factors which can affect the levels of antioxidant activity and total phenolic compounds in fruits could be the species, size and texture of fruits, the prepared form of the samples and the conditions of storage (e.g. time, temperature). Preliminary studies on the effect of storage in individual types of fruits are suggested before making a sampling plan for systematic analyses of their antioxidant activity.

Phenolic compounds in young developing kiwifruit in relation to light exposure: Implications for fruit calcium accumulation

The interaction between light availability and the biosynthesis of phenolic compounds in fruit of kiwifruit (Actinidia deliciosa var. deliciosa, C.F. Liang et A. R. Ferguson) was investigated. Fruits were exposed either to natural light or were artificially shaded while growing on mature vines and were analysed weekly during the first 11 weeks of development. Phenols were identified and quantified by using High Performance Liquid Chromatography (HPLC). Results showed that the predominant phenolic compounds were hydroxycinnamic acids (HCAs), flavonols and the flavan 3-ol epicatechin. Calcium (Ca2+), the main mineral nutrient involved in fruit quality was also determined. Light significantly increased the accumulation of both phenols and Ca2+ into the fruit. This work expands the list of known phenolics in kiwifruit and provides a possible explanation for the seasonal pattern of Ca2+ import into the fruit. Results on light–phenol interaction being apparently beneficial for fruit Ca2+ accumulation, suggest that accurate canopy management could enhance fruit quality.

Phenolic Compounds in Cereal Grains and Their Health Benefits

Research has shown that whole grain consumption helps lower the risk of cardiovascular disease, ischemic stroke, type II diabetes, metabolic syndrome, and gastrointestinal cancers (36,37). In addition to dietary fiber, whole grains contain many health-promoting components such as vitamins, minerals, and phytochemicals, which include phenolic compounds. Phenolic compounds have antioxidant properties and can protect against degenerative diseases (i.e., heart disease and cancer) in which reactive oxygen species (i.e., superoxide anion, hydroxyl radicals, and peroxy radicals) are involved (32,57). The general definition of a phenolic compound is any compound containing a benzene ring with one or more hydroxyl groups. Phenolic acids, flavonoids, condensed tannins, coumarins, and alkylresorcinols are examples. All plant-based foods have phenols, which affect their appearance, taste, odor, and oxidative stability (45). In cereal grains, these compounds are located mainly in the pericarp, and they can be concentrated by decorticating the grain to produce bran, which can be incorporated into a food product (i.e., breads, cookies, and tortillas) with increased dietary fiber levels and nutraceutical properties. Most of the literature on plant phenolics focuses mainly on those in fruits, vegetables, wines, and teas (33,50,53,58, 74). However, many phenolic compounds in fruits and vegetables (i.e., phenolic acids and flavonoids) are also reported in cereals. The different species of grains have a great deal of diversity in their germplasm resources, which can be exploited. Some phenols are unique to one plant species, such as the oat avenanthramides (12). Different methods of analysis for phenols and antioxidant activity are reported in the literature. Unfortunately, it is difficult to make comparisons of phenol and antioxidant activity levels in cereals since different methods have been used. The purpose of this article is to give an overview of phenolic compounds reported in whole grain cereals and to compare their phenol and antioxidant activity levels.

Regulation of inflammation and redox signaling by dietary polyphenols

Reactive oxygen species (ROS) play a key role in enhancing the inflammation through the activation of NF-κB and AP-1 transcription factors, and nuclear histone acetylation and deacetylation in various inflammatory diseases. Such undesired effects of oxidative stress have been found to be controlled by the antioxidant and/or anti-inflammatory effects of dietary polyphenols such as curcumin (diferuloylmethane, a principal component of tumeric) and resveratrol (a flavanoid found in red wine). The phenolic compounds in fruits, vegetables, tea and wine are mostly derivatives, and/or isomers of flavones, isoflavones, flavonols, catechins, tocopherols, and phenolic acids. Polyphenols modulate important cellular signaling processes such as cellular growth, differentiation and host of other cellular features. In addition, they modulate NF-κB activation, chromatin structure, glutathione biosynthesis, nuclear redox factor (Nrf2) activation, scavenge effect of ROS directly or via glutathione peroxidase activity and as a consequence regulate inflammatory genes in macrophages and lung epithelial cells. However, recent data suggest that dietary polyphenols can work as modifiers of signal transduction pathways to elicit their beneficial effects. The effects of polyphenols however, have been reported to be more pronounced in vitro using high concentrations which are not physiological in vivo. This commentary discusses the recent data on dietary polyphenols in the control of signaling and inflammation particularly during oxidative stress, their metabolism and bioavailability.

Radical scavenging activity of raspberry( Rubus idaeus L . ) fruit extracts

Thirty-one raspberry (Rubus idaeus L.) plants were collected in different natural habitats of Lithuania located in 17 districts and replanted in the experimental field. The fruits from different accessions were extracted with ethanol and the extracts were tested for their antioxidant activity (AA) by using ABTS·+radical cation decolourisation and DPPH·radical scavenging methods. All tested raspberry fruit extracts were antioxidatively active; their radical scavenging capacity at the applied concentrations varied from 52.9 to 92.6% in DPPH·reaction system and from 52.5 to 97.8% in ABTS·+system. The total amount of phenolic compounds in fruits varied from 5.6 to 13.7 mg of gallic acid equivalents in 1 g of plant extract. However, strong correlation between the radical scavenging capacity and the total amount of phenolic compounds in the fruit extracts was not observed, which indicates remarkable differences in the composition and antioxidant power of phenolic compounds present in the fruits harvested from r...

Jam Processing Effect on Phenolics and Antioxidant Capacity in Anthocyanin‐rich Fruits: Cherry, Plum, and Raspberry

ABSTRACT:Four cultivars of sour cherries (Balaton, Karneol, Kroeker and Northstar), 2 cultivars of plums (BY 8158.50 and Methley), and 1 red raspberry cv. Prelude were analyzed for total phenolics, antioxidant capacity, and total anthocyanins before and after jam production to evaluate their changes after thermal processing. Fruits had total phenolics ranging from 245.7 to 398.5 mg gallic acid equivalent (GAE)/100 g. Antioxidant capacity of fruits ranged from 354.8 to 692.3 mg/100 g, expressed as vitamin C equivalent antioxidant capacity (VCEAC). Total anthocyanins of fruits ranged from 30.9 to 67.1 mg cyanidin 3‐glucoside equivalent (CGE)/100 g. In 100 g of jam, total phenolics varied from 132.9 to 218.9 mg GAE, while antioxidant capacity ranged from 205.6 to 373.5 mg/100 g VCEAC. Jams had total anthocyanins of 5.4 to 30.4 mg CGE/100 g. On the basis of fresh fruit (100 g), the processing and heating during jam making generally decreased the contents of total phenolics, VCEAC, and total anthocyanins. Major losses occurred in anthocyanin content where overall retention varied from 89% to 21%. HPLC analysis of individual anthocyanins from cherry cv. Balaton to its jam showed that processing caused 90% decrease in anthocyanins. The results indicated that more than 73% total phenolics and more than 65% antioxidant capacity were retained after processing fruits into jams. Optimization of food processing would help to conserve the bioactive phenolic compounds in fruits.

Sample preparation in the determination of phenolic compounds in fruits

Phenolic compounds occur as secondary metabolites in all plants.1 They embrace a considerable range of substances possessing an aromatic ring bearing one or more hydroxy substituents, although a more precise definition is based on metabolic origin as those substances derived from the shikimate pathway and phenylpropanoid metabolism.2 A convenient classification of the plant phenols distinguishes the number of constitutive carbon atoms in conjunction with the structure of the basic phenolic skeleton (Table 1). The range of known phenolics is thus vast and also includes polymeric lignins and condensed tannins. Some plant phenols may be involved in primary metabolism whereas others have an effect on plant growth or protect the more vulnerable cell constituents against photooxidation by ultraviolet light by virtue of their strong UV absorption.3 Plant phenols also play an important role in disease resistance in the plant. Intense interest in fruit phenolics is also related to their physiological activity which depends on their antioxidant activity, the ability to scavenge both active oxygen species and electrophiles, the ability to inhibit nitrosation and to chelate metal ions, the potential for autooxidation and the capability to modulate certain cellular enzyme activities.4–7 Thus, knowledge of the levels of these compounds in plants is of considerable interest but is limited by problems of analysis. The structural diversity of the phenolics and its effect on physicochemical behaviour such as solubility and analyte recovery presents a challenging analytical problem. Moreover, a number of phenolic compounds are easily hydrolysed and many are relatively easily oxidized, which further complicates sample handling.8,9 This review emphasises the importance of sample preparation in the determination of phenolic compounds in plant materials particularly fruits. Fruits are an important dietary source of phenolic substances although interest is also shifting to other parts of the plant as potential commercial sources of phenols. Sample preparation is a critical step in analysis and this is even more significant with real samples where the matrix components are biologically active and the analytes represent a diverse spectrum of numerous compounds, many having an unknown identity. Thus, methods of extraction of phenols from fruits are generally dependent on several factors while the usual quantification procedures involve the separation sciences and are universally applicable. Soleas et al.10 illustrated this point. They developed a derivatization procedure for determination of 15 phenolic constituents in solid vitaceous plant materials and concluded that the method ‘should be suitable to measure polyphenols in fruit, vegetables, and other foods provided that efficient extraction techniques are employed’. Such statements are seen frequently in the analytical literature but they tend to belittle the importance of this step (or perhaps they serve to underline its critical importance). Rhodes and Price11 observed that the determination of phenolic species in foods is an important outstanding problem and reviewed methods for the extraction and purification of phenolic antioxidants as the conjugated forms that exist in plant foods. Knowledge of the extraction of phenolics is also desirable outside the analytical context for it has important practical applications in the food industry. For instance, the mechanism and kinetics of phenolic extraction from wood to wine during ageing in barrels12 has significant consequences for the production of quality wines.

Anthocyanins and other phenolic compounds in fruits of red-flesh apples

Anthocyanins and other phenolics of red-flesh apples, cv. Scugog, were extracted with acidified methanol and purified by Sephadex and by reverse phase high performance chromatography (RP HPLC). Four anthocyanins, three quercetins, two phenolic acids, two flavan 3-ols and one dihydrochalcone glycoside were characterized by HPLC, paper chromatography, spectral characteristics and colour reactions. The major phenolic compound was chlorogenic acid, and the predominant anthocyanin was cyanidin 3-galactoside, with cyanidin 3-glucoside, 3-arabinoside and 3-xyloside present in lower amounts. At 95–100 mg/kg of anthocyanin concentration, ‘Scugog’ apples are a rich source of the relatively rare cyanidin 3-xyloside.

Astringency of Fruits and Fruit Products in Relation to Phenolic Content

Publisher Summary This chapter briefly discusses the nature of the constituents responsible for the sensation of astringency and the physiology of the astringency sensation and the factors influencing it. Variety, maturity, and climate are known to influence the astringency of fruit. The chapter presents extensive data on the effect of seasonal conditions on the astringency of American grape juices, and also on apple juices. Certain fruits are astringent when they are unripe. During ripening on the tree or in storage, this astringency disappears. This loss in astringency may be accompanied by a change in the tannin fraction. The actual change in tannins, determined chemically, are small and may either increase or decrease. In astringent fruits, the main phenolic compounds found are flavanols. Both the flavanols and the flavan diols occur. Other major constituents of the phenolic fraction consist of the flavanols, kaempferol, quercetin, myricetin, chlorogenic acid, and the cinnarnic acids such as caffeic acid. Apart from environmental factors such as locality, season, stage of development, and mineral nutrition, which are known to affect the level of phenolic compounds in fruits, and hence astringency, various secondary treatments can decrease the degree of astringency in fruits, for example, treatment with carbon dioxide, ethylene; precipitation of the tannin with acetic acid, formaldehyde; and oxidation with ozone. Astringency may also be reduced by air drying, particularly in persimmons. If the fruit is chilled, astringency may increase. The various theories proposed to explain loss in astringency have been classified into three groups: binding, change in molecular size of the tannins, and a change in the hydroxylatzon pattern of the Phenolic Compound.