Phenolic Content , Antioxidant Capacity and Quality of Chokeberry ( Aronia melanocarpa ) Products

Increased consumption of fruits and vegetables is recommended in dietary guidelines worldwide (1). Among diff erent fruit species, berries have att racted great att ention for their bioactivity. In addition to nutritive dietary components (vitamins, minerals, sugars, organic acids, dietary fi bres and unsaturated fats), berries are also a good source of diff erent classes of phytochemicals such as fl avonoids (anthocyanins, fl avonols and fl avanols), tannins (proanthocyanidins, ellagitannins and gallotannins), stilbenoids (e.g. resveratrol), phenolic acids (hydroxybenzoic and hydroxycinnamic acid derivates) and lignans (2). Berry fruits are popularly consumed not only in fresh and frozen forms but also as processed and derived products including canned fruits, yogurts, beverages, jams and jellies. In addition, there has been a growing trend in the intake of berry extracts as ingredients in functional foods and dietary supplements, which may or may not be combined with other colourful fruits, vegetables and herbal extracts (1,2). In Croatia, berries like red raspberries, blackberries, blueberries and strawberries are commonly used in diet, but black chokeberry is almost unknown fruit (3). ISSN 1330-9862 original scientifi c paper


Introduction
Increased consumption of fruits and vegetables is recommended in dietary guidelines worldwide (1).Among diff erent fruit species, berries have att racted great att ention for their bioactivity.In addition to nutritive dietary components (vitamins, minerals, sugars, organic acids, dietary fi bres and unsaturated fats), berries are also a good source of diff erent classes of phytochemicals such as fl avonoids (anthocyanins, fl avonols and fl avanols), tannins (proanthocyanidins, ellagitannins and gallotannins), stilbenoids (e.g.resveratrol), phenolic acids (hydroxyben-zoic and hydroxycinnamic acid derivates) and lignans (2).Berry fruits are popularly consumed not only in fresh and frozen forms but also as processed and derived products including canned fruits, yogurts, beverages, jams and jellies.In addition, there has been a growing trend in the intake of berry extracts as ingredients in functional foods and dietary supplements, which may or may not be combined with other colourful fruits, vegetables and herbal extracts (1,2).In Croatia, berries like red raspberries, blackberries, blueberries and strawberries are commonly used in diet, but black chokeberry is almost unknown fruit (3).
Black chokeberry (Aronia melanocarpa (Michx.)Elliott ) belongs to the Rosaceae family, subfamily Maloideae, and is a deciduous shrub originating from the eastern part of North America (4,5) where it has been used for the treatment of cold by native Americans (Abnakians and Potawatomians).Today, chokeberry is also cultivated in Eastern European countries and Russia (6), where it is used for production of homemade or commercial juices, jams, fruit tea, wine and natural food colourants (5,7).It shows high resistance to frost, mechanized harvesting, damage during transportation and cold storage.Due to these advantages, popularity of chokeberry has increased recently (8).Chokeberries have very high contents of polyphenols, namely phenolic acids, proanthocyanidins, anthocyanins, fl avonols and fl avanones (9)(10)(11)(12).In a study where 143 different plant samples were analysed for polyphenols, the highest contents of these compounds were found in chokeberry (13).The high content and composition of the phenolic constituents of Aronia melanocarpa seem to be responsible for the wide range of the fruit's potential medicinal and therapeutic eff ects.Chokeberries have one of the highest in vitro antioxidant activities among fruits.The mechanisms of the in vivo antioxidant activity of their phenolics aft er absorption spread out far beyond radical scavenging and include suppressing the formation of reactive oxygen species (ROS) and reactive nitrogen species (RNS), inhibition of prooxidant, and restoration of antioxidant enzymes, and probably also cellular signalling to regulate the level of antioxidant compounds and enzymes (14).Although recent studies have pointed out diff erent positive eff ects of chokeberry juices and extracts (15)(16)(17)(18)(19)(20)(21), current evidence of eff ectiveness does not yet meet the accepted standards that would secure chokeberry products an indisputable place in therapy.Promising indications from laboratory and clinical data need to be confi rmed in more rigorous studies before putative therapeutic uses can be confi dently recommended for chokeberry products (22).
There are no studies on compositional and physical properties of Aronia melanocarpa products present on the Croatian market.Therefore, in this study 22 chokeberry products are evaluated.The objective of this study is to evaluate the physicochemical properties, the content of phenolics (total phenolics, fl avonoids, nonfl avonoids and anthocyanins) as well as antioxidant properties of diff erent chokeberry products present on the market.

Materials and Methods
Chokeberry products (Table 1) were purchased on Croatian markets during February 2014.There was only one requirement: they had to contain only chokeberry, without added sugar or other fruits.Products were stored at 4 °C until analysis.

Determination of physicochemical parameters
Total solid content of the chokeberry products was determined using a gravimetric method.A mass of (2± 0.0001) g of chokeberry sample was mixed with about 5 g of sea sand and dried at 105 °C until constant mass.Solu-ble solid content was determined with a digital refractometer (Atago PAL-3, Tokyo, Japan) and expressed as °Brix.Sample pH was determined at room temperature using an MA 5740 pH meter (ISKRA, Kranj, Slovenia).Two-point calibration was obtained using buff ers at pH=7.0 and 4.0.Titratable acidity was determined by titration of the water solution of chokeberry product with 0.1 M NaOH to end point of neutral pH (8.1).The volume of 0.1 M NaOH required to reach pH=8.1±0.2 was determined.The total titratable acidity was expressed as percentage of citric acid using a conversion factor of 0.070 (23).

Determination of juice colour
The colour of the chokeberry juices was mea sured in a transmitt ed mode through Konica Minolta CM-3500d spectrophotometer (Konica Minolta, Inc., Tokyo, Japan).Measurements were conducted in CIE L*a*b* system.L* is a measure of lightness, where values range from completely opaque (0) to completely transparent (100), a* is a measure of redness (or −a* of greenness) and b* of yellowness (or −b* of blueness) on the hue circle.The hue angle, h°, (Eq. 1) describes the relative amounts of redness and yellowness where 0°/360° is defi ned for red/magenta, 90° for yellow, 180° for green and 270° for blue colour: /1/ Chroma (C*) gives further information on the saturation or intensity of colour (24,25):

Extraction of phenolics
Phenolics were extracted according to the modifi ed method by Benvenuti et al. (26).Exactly 6 g of samples were weighed out and mixed with 20 mL of methanol/2 % HCl (95:5, by volume).Aft er 60 min the solution was fi ltered under vacuum in a 50-mL volumetric fl ask.Extraction of the residue was repeated using the same conditions.The fi ltrates were combined and adjusted to 50 mL in a volumetric fl ask with methanol/2 % HCl (95:5, by volume).The obtained extract was used for determination of total phenolic content (TPC), total nonfl avonoids (TN), total anthocyanins (TA) as well as for antioxidant capacity assay by DPPH method and reducing power assay using FRAP method.

Determination of total phenolics
For determination of TPC, a method with Folin-Ciocalteu reagent was used (27).An aliquot (20 μL) of diluted chokeberry extract or standard solutions of gallic acid (25-500 mg/L) was mixed with 1580 μL of distilled water and 100 μL of Folin-Ciocalteu reagent.A volume of 300 μL of sodium carbonate solution (200 g/L) was added to the mixture which was then shaken.Aft er incubation at room temperature for 2 h, the resulting absorbance was measured by the spectrophotometer Pye Unicam SP6-500 (Pye Ltd., Philips, Cambridge, UK) at the wavelength of 765 nm against the blank sample, which was used as reference.The results were calculated according to the calibration curve for gallic acid as follows: y=0.00103x-0.01128/3/ where y is the absorbance at 765 nm and x is the concentration of gallic acid in mg/L; R 2 =0.9973.Total phenolics were expressed as mg of gallic acid equivalents (GAE) per L of chokeberry juices and as mg of GAE per 100 g of dry matt er (dm) of other chokeberry products.

Determination of total fl avonoid and nonfl avonoid contents
Determination of total fl avonoid (TF) content was performed by the indirect method using formaldehyde to precipitate these compounds, as described by Ough and Amerine (28).A mixture of 3 mL of chokeberry extract solution, 1.5 mL of aqueous solution of hydrochloric acid (1:4, by volume) and 3 mL of formaldehyde was prepared in a 25-mL fl ask.In order to remove air, nitrogen gas was injected and the stoppered fl ask was left in the dark for 24 h at 22 °C.The next day it was fi ltered and the clear liquid was used in the same procedure (27) as the one used to prepare samples for TPC determination.The amount of TF was calculated as the diff erence between total phenolics and total nonfl avonoids (TN).The results were expressed as mg of GAE per L and as mg of GAE per 100 g of dm for chokeberry juices and other products, respectively.

Determination of total anthocyanins
Total anthocyanin (TA) content, calculated as cyanidin-3-glucoside, was determined by the pH diff erential method of Giusti and Wrolstad (29).Two dilutions of each chokeberry extract were prepared, one with potassium chloride buff er (pH=1.0),and the other with sodium acetate buff er (pH=4.5).Aft er 15 min of incubation at room temperature, the absorbance was measured simultaneously at the wavelengths of 510 and 700 nm.The content of TA was calculated using Eqs. 4 and 5 with molar absorption coeffi cient of cyanidin-3-glucoside of 26 900 L/ (mol•cm) and molar mass of 449.2 g/mol: /4/ /5/ where A is absorbance, ε is molar absorption coeffi cient of cyanidin-3-glucoside equivalents (CGE) (L/(mol•cm)), L is cell pathlength (1 cm), M r is molecular mass of CGE, DF is dilution factor, V is fi nal volume (mL), and m is mass of the sample (mg).Results were expressed as mg of CGE per L of chokeberry juices and as mg of CGE per 100 g of dm of other products.

Determination of total antioxidant capacity by DPPH method
The eff ect of chokeberry products on 2,2-diphenyl-2picrylhydrazyl (DPPH) radical was determined according to the method of Brand-Williams et al. (30).The method was based on the reduction of stable DPPH radical in the presence of antioxidants.A volume of 2 mL of diluted chokeberry extract or methanol solution of Trolox (25-200 μmol/L) was mixed with 2 mL of methanol and 1 mL of 0.5 mM DPPH methanolic solution.The mixture was vortexed and kept in the dark for 20 min.Aft er incubation, the absorbance was measured at the wavelength of 517 nm against a blank of methanol without DPPH.The results were calculated according to the calibration curve for Trolox: y=-0.62525x+1.33117/6/ where y is the absorbance at 517 nm and x is the concentration of Trolox in μmol/L; R 2 =0.9817.DPPH values were expressed as mmol of Trolox equivalents (TE) per L and mmol of TE per 100 g of dm for chokeberry juices and other products, respectively.

Determination of FRAP
The ferric reducing antioxidant power (FRAP) assay was conducted according to Benzie and Strain (31).The method is based on the reduction of the Fe 3+ -2,4,6-tripyridyl-s-triazine (TPTZ) complex to the ferrous form at low pH.This reduction is monitored by measuring the absorbance change at 595 nm.The FRAP reagent was prepared from 5 mL of TPTZ solution (10 mmol/L) in hydrochloric acid (40 mmol/L) and 5 mL of FeCl 3 solution (20 mmol/L) mixed with 50 mL of acetate buff er (0.3 mol/L, pH=3.6).For the determination of the antioxidant capacity, the FRAP reagent (2.08 mL) was mixed with 240 μL of water and 80 μL of the appropriately diluted sample or standard solution of FeSO 4 •7H 2 O (0.125-2.000 mmol/L).The mixture was allowed to stand for 5 min at 37 °C before the absorbance was measured at 595 nm.FRAP values were calculated according to the calibration curve for FeSO 4

Statistical analysis
The data were analysed using STATISTICA v. 12.0 (Statsoft Inc, Tulsa, OK, USA).Analysis of variance (ANOVA) was used to establish signifi cant diff erences between and within groups of chokeberry products.Diff erences were considered signifi cant at p≤0.05.Values were expressed as means (N=3).For comparison of the contents of TPC, TF, TN, TA and DPPH or FRAP assays and also for comparison of colour parameters and TPC, TF, TN or TA contents, the coeffi cients of correlation were determined for each combination.

Results and Discussion
Chokeberry fruits are not popular as table fruits but they are generally consumed as processed chokeberry products including juice, jam, syrup and nutritional supplements.Data on the phenolic contents of chokeberry have been reported in several studies (3,6,26,(32)(33)(34)(35), and the present study contributes to the existing knowledge by providing new data on diff erent chokeberry products such as powders, capsules, fruit tea and dried berries.

Physicochemical parameters and juice colour
The analysis of chokeberry samples indicated diff erent physicochemical properties among groups of products as well within groups (Table 2).In case of chokeberry juices, the total solid content ranged from 13.42 % in juice sample J10 to 21.54 % in juice sample J2, while in the other samples it was much higher.Chokeberry capsules had the highest total solid content among groups (mean value 93.78 %) followed by chokeberry powders (mean value 92.35 %), fruit tea (mean value 91.49%) and dried berries (mean value 83.31 %).In research of Mayer-Miebach et al. (36) the dry matt er content of berries ranged from 17.9 to 26.0 %, in juices from 11.1 to 17.4 % and in pomace from 44.6 to 50 %.The mean value of total solid content of chokeberry capsules (93.78 %), fruit tea (2.35 %) and powders (91.49%) present on the market is very similar to the results of Sójka et al. (37), who investigated chokeberry pomace obtained in an industrial-scale processing of fruit into juice.The lowest value of soluble solid content (13.70 °Brix) was in juice sample J10, while the highest value characterised capsules, i.e. sample C1 (83.71 °Brix).The soluble solid content in chokeberries depends on numerous factors: weather, environmental conditions, crop period and variety, and it amounts to 12.4 or 18.3 % (5).Chokeberry products had a mean pH value of 3.90 ranging from 3.54 (sample J10) to 4.28 (sample DB1).The mean total titratable acidity (TTA) of all products was 1.42 (as percentage of citric acid) ranging from 0.29 (sample J2) to The °Brix/TTA ratio is a quality att ribute used by the fruit industry to indicate the tartness of fruits and fruit juices (38).This ratio increases with maturity of the fruit and is used to identify the optimum maturity for harvesting to produce maximum product quality (39).The mean °Brix/TTA ratio was 20.42 and ranged from 11.24 in the fruit tea sample FT2 to 78.54 in the juice sample J2 (Table 2).ANOVA showed signifi cant diff erences of physicochemical properties among juices, powders, fruit tea, capsules and dried berries and also among individual samples within groups, with the exception of total solid content and total titratable acidity of samples of dried berries.
Since the colour of the product, especially juices, is extremely important feature that contributes to the overall quality, one of the aims of this paper was to determine colour parameters of chokeberry juices (Table 3).Values of variable L* were low in all samples, from 0.52 (juice sample J10) to 15.00 (juice sample J7), which indicates that samples were very dark since the variable L* varies from 0 representing black to 100 representing white.Similar values of the parameter L* of chokeberry juices were observed by Ochmian et al. (5).The a* value, providing information of the position in the colour gamut between green and red, measured on the juice surface ranged from 3.74 (juice sample J10) to 46.42 (juice sample J7).The juice surface colour defi ned by the b* parameter, in dicating the location on the axis between yellow and blue colours, ranged from 0.88 (juice sample J10) to 25.84 (juice sample J7), which means that yellow colour is present.Positive a* values were also observed in chokeberry juices, pulp and fruit by Ochmian et al. (5) and in chokeberry powders by Horszwald et al. (40).In a research of Horszwald et al. (40) yellow colour was present in chokeberry powders, while in the work of Ochmian et al. (5) b* values were negative, which indicates the presence of blue colour.Parameters L*, C* and h° are related to the physiological att ributes of visual response (41).Hue describes the visible colour and chroma describes the brightness or intensity of the hue.Indices of L*, C* and h° are usually useful for tracking colour changes (42).The decrease in chroma means an increase in the tonality of the fruit colour (43).
Table 4 shows the correlation coeffi cients between the colour parameters and TPC, TN, TF and TA, from which a negative correlation of colour parameters with the content of total nonfl avonoids and of colour parameters with the content of total anthocyanins is evident.

Total phenolics, fl avonoids, nonfl avonoids and anthocyanins
The content of total phenolics (TPC), total fl avonoids (TF) and total nonfl avonoids (TN) in twenty-two chokeberry products is given in Table 5. TPC ranged from 1494 mg of GAE per 100 g of dm in fruit tea sample FT3 to 5292 mg of GAE per 100 g of dm in capsule sample C2.Comparing the results of our research with the results of other authors, the mass fraction of TPC in chokeberry juices was lower than in the fi ndings of others (3,14,35,43).Some authors noticed higher values of phenolics in black chokeberry fruit in comparison with our results (14,26,(32)(33)(34), while Jurgoński et al. (44) reported much higher values of total phenolics in commercial chokeberry extract.Diff erent cultivars of chokeberries were analysed and total phenolic values ranged from 8563.8 to 12055.7 mg of GAE per kg of fresh mass (fm) (34).Lower or higher values reported in the literature might have resulted from diff erent extraction methods used for analysis, diff erences in analytical procedures applied, diff erent processing technologies and storage conditions, or diff erences in chokeberry cultivars (14).It was demonstrated that the total phenolics in hot-air-dried tomatoes increased up to 29 % compared to the corresponding levels in fresh tomatoes (45).In comparison with other products, chokeberry juices had lower phenolic content, which might be related to the diff erences in their moisture content (46).In total phenolic content, fl avonoids were predominant, and their amounts varied from 867 mg of GAE per 100 g of dm in DB1 sample to 3317 mg of GAE per 100 g of dm in P2 sample.Average total fl avonoid content in chokeberry juices was 3180 mg of GAE per L. It was calculated that percentages of TF in signifi cant at p≤0.05 and p≤0.001, respectively Contents of total phenolics (TPC), total nonfl avonoids (TN), total fl avonoids (TF) and total anthocyanins (TA) are expressed as mg per L. TPC, TN and TF are expressed as mg of gallic acid equivalents (GAE), while TA is expressed as mg of cyanidin-3-glucoside equivalents (CGE) TPC varied between 36.06 and 80.46 %.The obtained results suggest that fl avonoids were the most abundant phenolics in chokeberry products.Chokeberries are a rich source of anthocyanins, proanthocyanidins and hydroxycinnamic acids (14).Oszmianski and Wojdylo (35) showed that polymeric proanthocyanins are the major class of polyphenolic compounds in chokeberry and represent 66 % of polyphenols in fruits.Their content ranged between 1578.79 mg per 100 g of dm of chokeberry juice up to 8191.58 mg per 100 g of pomace.In a research of Kapci et al. (47) the content of total fl avonoids was higher in chokeberry juices and in dried chokeberries.According to the literature, the main contributor of total fl avonoid content is quercetin.Quercetin and several quercetin glycosides (quercetin-3-galactoside, quercetin-3-glucoside and quercetin-3-rutinoside) were also detected in chokeberries but in relatively low mass fractions of about 71 mg per 100 g of fm (14).
All samples had lower content of TN (808 to 1527 mg of GAE per L and 479 to 2300 mg of GAE per 100 g of dm) and TA (150 to 1228 mg of CGE per L and 141 to 2468 mg of CGE per 100 g of dm).Chlorogenic and neochlorogenic acids are the major non-fl avonoid polyphenolic compounds in chokeberries, and according to Oszmianski and Wojdylo (35) they represent about 7.5 % of chokeberry fruit polyphenols.The hydroxycinnamic acids are represented by signifi cant amounts of chlorogenic (61 to 193 mg per 100 g of fm) and neochlorogenic acids (85 to 123 mg per 100 g of fm) (14).Higher contents of TA in chokeberry juice were reported by Jakobek et al. (34) and others (26,47), while Horszwald et al. (40) reported higher content of TA in chokeberry powders.Results of all chokeberry samples were found to be lower, which can be explained by using pH diff erential method instead of HPLC method.Anthocyanins represented signifi cant fraction of total phenolics in powder and capsule samples (from 27.53 in P3 to 54.72 % in C1 sample).Chokeberries contain relatively higher amounts of anthocyanins compared to other fruits including blueberry, blackberry, raspberry, grape and cherry, which are known as rich sources of anthocyanins (14).In research of Jakobek et al. (3) the fraction of anthocyanins in chokeberry was 41 %, which was much higher compared to the fraction in red raspberry (19 %) and strawberry (23 %).Similar to total phenolic content, Jurgoński et al. (44) reported considerably higher concentration of anthocyanins.Compared to other berries, the aronia anthocyanin profi le is very simple, consisting almost exclusively of cyanidin glycosides, namely cyanidin-3-arabinoside, cyanidin-3-galactoside, cyanidin--3-glucoside and cyanidin-3-xyloside.Cyanidin-3-galactoside and cyanidin-3-arabinoside are predominant in the berries with a cumulative content >90 % (14).Lower levels of total anthocyanins in chokeberry products can be the result of factors such as pH, chemical composition, temperature, light and oxygen.These factors may change easily during processing of fruits into juice and other products.It was reported that anthocyanins are aff ected at several steps of juice processing, namely pressing, clarification and pasteurisation (47,48).

Total antioxidant capacity and reducing power
The total antioxidant capacity (TAC) and reducing power (RP) of diff erent chokeberry samples are shown in Table 6.Examined products possess high antioxidant capacity (12.09 to 40.19 mmol of TE per L and 58.49 to 191.31 mmol of TE per 100 g of dm) and reducing power (38.71 to 79.86 mmol of Fe 2+ per L and 13.50 to 68.60 mmol of Fe 2+ per 100 g of dm).Highest TAC was reported in dried berries (mean value 187.41 mmol of TE per 100 g of dm), followed by fruit tea (mean value 144.54 mmol of TE per 100 g of dm) and powder (mean value 110.58 mmol of TE per 100 g of dm) samples.The reducing power (FRAP assay) in this study was determined as reduction of Fe 3+ to Fe 2+ .The highest RP was observed in P2 sample (68.60 mmol of Fe 2+ per 100 g of dm), followed by C1 sample (65.82 mmol The values are presented as mean±standard deviation (S.D.).The same lett er in the superscript in the same column indicates no signifi cant diff erences (p>0.05).J1-J11=chokeberry juices, P1-P3=chokeberry powders, C=choke berry capsules, FT=chokeberry fruit tea, DB=chokeberry dried berries.Contents of TPC, TN, TF and TA are expressed as mg per 100 g of dry matt er (dm) in powder, capsule, fruit tea and dried berry samples.Contents of TPC, TN, TF and TA in juice samples are expressed as mg per L. TPC, TN and TF are expressed as mg of gallic acid equivalent (GAE), while TA are expressed as mg of cyanidin-3-glucoside equivalents (CGE) of Fe 2+ per 100 g of dm), P1 sample (60.66 mmol of Fe 2+ per 100 g of dm) and C2 sample (60.35 mmol of Fe 2+ per 100 g of dm).High antioxidant activity of chokeberry fruit and products has been reported in numerous studies (3,6,14,34,35).Walkowaik-Tomczak (48) showed that antioxidant activity of chokeberry juices is under the infl uence of pasteurisation and storage.Oxygen availability rate during pasteurisation and storage and storage temperature were found to have the biggest eff ect on the antioxidant activity of chokeberry juices.Reducing power is generally linked to the presence of reducing substances, which have been shown to exert antioxidant activity by breaking the free radical chain by donating a hydrogen atom (49).Antioxidant activity of chokeberry juice concentrate against DPPH radical was stronger than that of black currant, elderberry, red currant, strawberry, red raspberry and cherry concentrate (3,26).
The correlation between the antioxidant activity measured by DPPH and FRAP method and total phenolics is presented in Table 7. Diff erent groups of polyphenolic compounds may contribute diff erently to total antioxidant activity and, therefore, it is necessary to observe the existence of a correlation between the antioxidant activity and individual groups of polyphenolic compounds.The antiradical activity was mostly aff ected by the content of phenolic compounds.To see the relationship between the phenolic compounds in chokeberry products and their antiradical activity, TAC and RP values were correlated with the amount of phenolic compounds.This showed that the highest correlation of phenolic compounds and total antioxidant acitivity was between TA and TAC, and between TN and TAC in powder samples, followed by TN and TAC in fruit tea samples.High correlation was also found between TF and RP in powders and between TN and RP in fruit tea.These results imply that fl avonoids and nonfl avonoids were the major contributors to the antioxidant capacity of the investigated chokeberry products, especially in the case of powders, fruit tea and capsules.Acording to the data presented by others, TPC of various small fruits correlates bett er with the antioxidant activity than TA does (3,9).ANOVA showed significant diff erences between TAC and RP values between groups of chokeberry products and also among individual samples within groups, with the exception of the RP of samples of capsules.

Conclusion
In this investigation, very high contents of phenolic substances and high values of antioxidant properties were observed in diff erent chokeberry products.The presented data show diff erences in the quality and phenolic composition of chokeberry juices, powders, capsules, fruit tea and dried berries found on the market.Chokeberry capsules and powders have considerably higher amount of total phenolics and total anthocyanins in comparison with other products.Diff erent levels of antioxidants might be related to the diff erences in the variety and growing conditions of the fruits.To fully understand the eff ect of processing, research focused on diff erent processing techniques starting from the same material should be done.Chokeberry products can become a valuable source of nutritionally important substances in human nutrition.Due to the high content of natural antioxidants, their consumption could bring health benefi ts.Besides studies focusing on diff erent processing techniques, future studies should include additional analyses to obtain a complete evaluation of the quality of chokeberry products and also in vivo and in vitro bioavailability studies.Data from these studies will be helpful to understand the bioaccessibility and bioavailability of nutritive compounds of chokeberry and its products.

Table 1 .
Producer, country of origin, fruit content and composition of chokeberry products

Table 2 .
(5)sicochemical properties of chokeberry products Comparing the groups of products, it is evident that capsules have the highest total titratable acidity and juices the lowest.Ochmian et al.(5)reported similar values for titratable acidity in the range from 0.75 to 1.05 g of citric acid per 100 g of berries.

Table 4 .
Correlation coeffi cients (R) between phenolics and colour parameters of chokeberry juices

Table 6 .
Total antioxidant capacity (TAC) and reducing power (RP) of chokeberry products of dry matt er (dm) for powder, capsule, fruit tea and dried berry samples.Contents of TPC, TN, TF and TA for juice samples are expressed as mg per L. TPC, TN and TF are expressed as mg of gallic acid equivalent (GAE), while TA is expressed as mg of cyanidin-3-glucoside equivalents (CGE).TAC and RP are expressed as mmol per 100 g of dm for powder, capsule, fruit tea and dried berry samples.TAC and RP for juice samples are expressed as mmol per L. TAC is expressed as mmol of Trolox equivalent (TE), while RP is expressed as mmol of Fe 2+ equivalents (FE)