Scholarly article on topic 'Effect of ascorbic acid treatment on some quality parameters of frozen strawberry and raspberry fruits'

Effect of ascorbic acid treatment on some quality parameters of frozen strawberry and raspberry fruits Academic research paper on "Agriculture, forestry, and fisheries"

CC BY-NC-ND
0
0
Share paper
Academic journal
Annals of Agrarian Science
OECD Field of science
Keywords
{Strawberry / Raspberry / Freezing / Antioxidant / Polyphenols}

Abstract of research paper on Agriculture, forestry, and fisheries, author of scientific article — Tamar Turmanidze, Merab Jgenti, Levan Gulua, Vazha Shaiashvili

Abstract Strawberry (Red Dream and Camarosa varieties) and raspberry (Nova and Killarney varieties) fruits were harvested in the middle summer in eastern part of Georgia. After harvesting average samples were immediately dipped into 0%, 1% or 2% ascorbic acid solution at 20 ± 1 °C temperature with exposure time of 2.5 min. Then, the samples were frozen at −40 °C and stored in plastic containers at −20 °C for 6 months. After 3 months storage period Total soluble solids (TSS) of strawberry and raspberry fruits decreased by 10–14% in both treated and untreated samples. TSS changes in the next three months were not statistically significant. pH values of the samples also decreased by 10–13% after 3 months regardless treatment with ascorbic acid. In the next three months pH values continued decreasing approximately with the same rate for all the samples. Due to the treatment of the fruit samples by 1% and 2% ascorbic acid, content of the last one in fruits after three months storage was increased approximately by 30% and 100% respectively and was kept practically at the same level for the next six months. In the untreated fruits of Red Dream and Camarosa of strawberry varieties during the first three months storage Total phenolic compounds (TPC) reduced by 20%. In both untreated varieties of raspberry TPC reduced by 14%. Ascorbic acid treatment increased polyphenol retaining in all frozen samples of strawberry and raspberry fruits. For Camarosa treated with 2% ascorbic acid this effect was the highest – 15%; for Red Dream the effect was the lowest – 5%. The next three months storage practically did not affect TPC in Red Dream variety of strawberry fruits neither untreated nor treated ones. In the rest varieties of berries TPC decreased maximum by 29% (Camarosa 2% treated) and minimum by 9% (Nova untreated). Antioxidant potential of the fruits was in good correlation (R2 = 0.93) with TPC for all six months of storage.

Academic research paper on topic "Effect of ascorbic acid treatment on some quality parameters of frozen strawberry and raspberry fruits"

Annals of Agrarian Science xxx (2017) 1—5

Acoca&ks ß@iaai3DÄC3

•w ^ S

Contents lists available at ScienceDirect

Annals of Agrarian Science

journal homepage: http://www.journals.elsevier.com/annals-of-agrarian-

science

Effect of ascorbic acid treatment on some quality parameters of frozen strawberry and raspberry fruits

Tamar Turmanidze*, Merab Jgenti, Levan Gulua, Vazha Shaiashvili

Department of Food Technology, Agricultural University of Georgia, David Aghmashenebeli Alley 240, Kakha Bendukidze Campus, Tbilisi, Georgia ARTICLE INFO ABSTRACT

Article history: Received 22 December 2016 Accepted 9 February 2017 Available online xxx

Keywords:

Strawberry

Raspberry

Freezing

Antioxidant

Polyphenols

Strawberry (Red Dream and Camarosa varieties) and raspberry (Nova and Killarney varieties) fruits were harvested in the middle summer in eastern part of Georgia. After harvesting average samples were immediately dipped into 0%, 1% or 2% ascorbic acid solution at 20 ± 1 °C temperature with exposure time of 2.5 min. Then, the samples were frozen at -40 °C and stored in plastic containers at -20 °C for 6 months. After 3 months storage period Total soluble solids (TSS) of strawberry and raspberry fruits decreased by 10—14% in both treated and untreated samples. TSS changes in the next three months were not statistically significant. pH values of the samples also decreased by 10—13% after 3 months regardless treatment with ascorbic acid. In the next three months pH values continued decreasing approximately with the same rate for all the samples. Due to the treatment of the fruit samples by 1% and 2% ascorbic acid, content of the last one in fruits after three months storage was increased approximately by 30% and 100% respectively and was kept practically at the same level for the next six months. In the untreated fruits of Red Dream and Camarosa of strawberry varieties during the first three months storage Total phenolic compounds (TPC) reduced by 20%. In both untreated varieties of raspberry TPC reduced by 14%. Ascorbic acid treatment increased polyphenol retaining in all frozen samples of strawberry and raspberry fruits. For Camarosa treated with 2% ascorbic acid this effect was the highest — 15%; for Red Dream the effect was the lowest — 5%. The next three months storage practically did not affect TPC in Red Dream variety of strawberry fruits neither untreated nor treated ones. In the rest varieties of berries TPC decreased maximum by 29% (Camarosa 2% treated) and minimum by 9% (Nova untreated). Antioxidant potential of the fruits was in good correlation (R2 = 0.93) with TPC for all six months of storage. © 2017 Agricultural University of Georgia. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Introduction

Strawberry (Fragaria x ananassa) cultivars Red Dream and Camarosa, Raspberry (Rubus idaeus L.) cultivars Nova and Killarney fruits belongs to the Rubus genus in the Rosacea family. in Georgia because of a good agro-climatic condition in Georgia for cultivation of berry fruits they are widely grown in the country [1]. Berries play important role in human nutrition and hence are very significant from the point of view of food security problems [2]. Berries are excellent sources of phytochemicals that are believed to have significant biological activity. Berry containing elevated levels of bioactive compounds, is attracting considerable attention due to their potential to lower the risk of chronic diseases and their

* Corresponding author. E-mail address: tturm2010@agruni.edu.ge (T. Turmanidze). Peer review under responsibility of Journal Annals of Agrarian Science.

associated huge healthcare costs [3—12]. Phenolic compounds may contribute to this protective effect. Berries are very rich in health-promoting phytochemicals [13]. Many of these phytochemicals have antioxidant activity and may help protect cells against the oxidative damage caused by free radicals [14—18].

However, berries are also highly perishable fruits due to their soft texture, high softening rate and high sensitivity to fungal attack. Enzymes, namely polyphenoloxidase (PPO), peroxidese (POD) are involved in the fast deterioration of fruit during post-harvest handling and processing [19]. Freezing is one of the most important methods for the quality preservation of fruits and vegetables during long-term storage [20]. There is mainly antibrowning additives such as ascorbic acid, which is applied by dipping the fruit in different solution before freezing [21—23]. The freezing process reduces the rate of the degradation reactions and inhibits the microbiological and enzymatic activity [19]. Freezing processes have only a slight effect on the initial vitamin C content of fruit [24]. The destruction of vitamin C occurs during freezing and frozen

http://dx.doi.org/10.1016/j.aasci.2017.02.017

1512-1887/© 2017 Agricultural University of Georgia. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).

T. Turmanidze et al. / Annals of Agrarian Science xxx (2017) 1—5

storage and this parameter has been employed to limit the frozen storage period of frozen fruit. The main cause of loss of vitamin C is the action of the enzyme ascorbate oxidase [19].

The vitamin C content, besides being an indicator of nutrient value, is, in the case of frozen fruits and vegetables, a reliable index for estimating the quality deterioration at any point of the marketing route of a product to its final destination, the consumer [25,26].

The objective of this work was to study effect of application of ascorbic acid on the quality parameters such as content of TSS, TPC, vitamin C, also on pH and antioxidant activity of frozen strawberry and raspberry fruits during storage.

Material and methods

Chemicals

Ascorbic acid and Potassium dihydrogen phosphate were purchased from Sigma - Aldrich (Steinheim, Germany), TPTZ-2,4,6-Tris (2-pyridyl)-s-triazine (Sigma - Aldrich, Switzerland), Folin - Cio-calteu reagent (Appli Chem, Germany), hydrochloric acid, formic acid and phosphoric acid were provided by Merck (Darmstadt, Germany), Sodium carbonate was purchased from Chem Cruz (Chem Cruz Biochemicals, USA), Ethyl acetate and methanol (Sigma - Aldrich Steinheim, Germany) were HPLC grade. All other reagents were commercially available at the local market and were of analytical grades.

Sample collection

Berry fruits were harvested in the middle summer in eastern part of Georgia (GPS coordinates: Latitude: 41° 57' 59.99" N, Longitude: 44° 05' 60.00" E). After harvesting average samples of fruits were immediately dipped into 0%, 1% or 2% ascorbic acid solution at 20 ± 1 °C temperature with exposure time of 2.5 min. Then, the samples (275 g) were frozen at -40 °C and stored in plastic containers at -20 °C for 6 months.

Sample preparation for chemical analyses

Preparation of sample for ascorbic acid determination by HPLC (Varian - Prostar - 500, USA, detector - UV Varian Prostar, Auis-tralia, column - 250 mm x 4.6 mm, dp = 5 mm, Symmetry, Waters, Ireland) method was done according to Koyuncu et al. (2010) [27]. Briefly, sample (10 g) was extracted in 10 mL water adjusted to pH 1.5 with 10 mL phosphoric acid-water (2%, v/v). The extracts were filtered through filter paper 45 mm (Whatman, UK). Then, 1.5 mL buffer (0.01 M KH2PO4, pH 8.0) was added to 1.5 mL sample extract, 1 mL (vitamin C) of preferred mixtures were loaded on to C 18 cartridges (Agilent, Bond Elut, USA). After loading, 3.0 mL water adjusted to pH 1.5 with 2.0 mL phosphoric acid-water (2%, v/v) were passed through the cartridges.

Samples for antioxidant analysis were prepared according to Rodriguez - Saona et al. (2001) [28]. About 40 g of berries were cryogenically milled in liquid nitrogen. Chilled test tubes were filled with milled fruit powder and weighed (5 g), and then the powder was extracted with acetone (200 mL). The acetone was removed under vacuum in a rotary evaporator at < 30 °C and then 250 mL, 70% methanol was added to the powder. Total methanol extract was examined for antioxidant activity.

The frozen samples were defrosted during 3 h at 18 °C.

Measures TSS

TSS was measured by digital refractometer (WYA - 2 S China) according to Brix reading [29].

Determination of pH

pH value of the berry fruits was measured using a pH-meter (PHS-3C, Shanghai Rotech Pharmaceutical Engineering Co., Ltd, China) [30].

Determination of vitamin C

Determination of vitamin C was performed by HPLC method as described by Koyuncu et al. (2010) [27]. The columns used were 250 mm x 4.6 mm, dp = 5 mm (Symmetry, Waters, Ireland), The mobile phases were water adjusted to pH 3.0 with phosphoric acid. The UV detector (Varian pro Star, Australia) was set at 215 nm. Quantitation was based on the peak area measurement. For HPLC (Varian-Prostar - 500, USA), 20 mL of the sample were injected.

Determination of total phenolic compounds (TPC)

Determination of TPC was performed by Bond et al. (2003) [31]. An aliquot of 1.0 mL of diluted sample extract was vortexed with 10 mL DI water and 1.0 mL Folin-Ciocalteau reagent, and 1.0 mL deionized water was used as control. After equilibration at room temperature for 8 min, the solutions were mixed with 4 mL of 7.5% (w/v) Na2CO3. The samples and standards (Gallic acid dilute working standard solutions: 10-50 mg mL-1) were equilibrated at room temperature for 60 min. The absorbance of the samples and standards were measured spectrophotometrically (UV/Vis spec-trophotometer, A&E Lab Co LTD, UK) at 765 nm, with a 10 mm path length cell. TPC was calculated as mg of gallic acid equivalents per 100 g fresh weight of sample.

Ferric reducing ability of plasma (FRAP) assay

The antioxidant capacity was determined following the procedure described by Benzie et al. (1996) [32]. with modifications. The FRAP reagent was freshly prepared by adding 10 mM 2,4,6-tripyridyl-s-triazine (TPTZ) (dissolved in 40 mM of HCl), 20 mM of FeCl3 in water and 300 mM of acetate buffer (pH 3.6) in the ratio of 1:1:10. The FRAP reagent was warmed to 37 °C for 15 min. Then, 100 mL of sample was added to 3.0 mL reagent blank. The absor-bance was recorded at 593 nm. The reaction was monitored for 4 min. FRAP values of samples were compared to that of ascorbic acid and expressed as vitamin C equivalents per 100 g of fresh fruits.

Statistical analysis

The data represents the mean of three replicates ± standard deviation (SD). Data were subjected to the two-way ANOVA and Tukey's HSD tests. All calculations were performed with Microsoft Excel 2007 (Microsoft Corp., Redmond, WA, USA) with PHstat 2 version 3.11add-in assistance.

Results and discussion

After 3 months storage period TSS of samples of strawberry and raspberry fruits decreased by 10-14% in both treated and untreated samples, probably because of respiration process (Table 1.) But difference between the treated and untreated samples was not statistically significant (p < 0.05). TSS changes in the next three months were not statistically significant.

T. Turmanidze et al. / Annals of Agrarian Science xxx (2017) 1—5 3

Table 1

Effect of ascorbic acid treatment on quality parameters of berries after 3 months frozen storage (at -20 ± 0.5 °C). Berry Variety Treatments % with ascorbic acid TSS % pH Vitamin C mg 100 g-1 TPCmg100g-1 FRAP mg equivalents vitamin C 100 g-1

Strawberry Red Dream fresh 8.55 ± 0.15 3.50 ± 0.02 45.17 ± 0.24 150.14 ± 2.45 413.10 ± 3.52

0 7.42 ± 0.43 3.16 ± 0.10 43.30 ± 0.75 120.81 ± 2.15a 290.25 ± 4.12

1 7.67 ± 0.16 2.95 ± 0.23 45.32 ± 0.23 126.73 ± 2.05a 340.83 ± 2.58

2 7.73 ± 0.32 2.82 ± 0.17 50.80 ± 0.33 128.80 ± 2.78a 386.35 ± 3.13 Camarosa fresh 7.50 ± 0.32 3.41 ± 0.02 52.14 ± 1.92 160.41 ± 3.17 584.00 ± 3.91

0 6.15 ± 0.23 2.87 ± 0.11 35.21 ± 0.14 130.80 ± 4.28b 400.00 ± 3.17

1 6.57 ± 0.35 2.79 ± 0.21 44.45 ± 0.44 147.73 ± 2.16b 468.12 ± 2.56

2 6.60 ± 0.18 2.50 ± 0.13 48.63 ± 0.20 150.12 ± 3.15b 490.20 ± 4.18

Raspberry Nova fresh 11.67 ± 0.45 2.92 ± 0.01 19.24 ± 1.19 106.52 ± 2.1 190.12 ± 2.15

0 10.12 ± 0.26 2.43 ± 0.12 12.10 ± 0.47 90.10 ± 1.95b 110.28 ± 3.18

1 10.20 ± 0.09 2.21 ± 0.31 23.35 ± 0.20 102.22 ± 2.16b 137.18 ± 2.42

2 10.22 ± 0.16 2.15 ± 0.16 42.18 ± 1.00 107.16 ± 3.17b 172.00 ± 2.88 Killarney fresh 11.00 ± 0.08 2.45 ± 0.02 23.87 ± 0.35 116.01 ± 1.25 220.00 ± 3.56

0 9.56 ± 0.33 2.07 ± 0.12 13.78 ± 0.55 97.56 ± 4.16b 122.07 ± 2.13

1 9.87 ± 0.35 1.95 ± 0.18 30.39 ± 1.23 103.25 ± 2.11b 153.18 ± 3.17

2 9.80 ± 0.21 1.72 ± 0.19 45.52 ± 1.33 109.38 ± 3.52b 157.23 ± 3.12

a Difference between treated and untreated samples were not statistically significant (p < 0.05). b Difference between treated and untreated samples were statistically significant (p < 0.01).

pH value

pH values of the samples also decreased by 10-13% after 3 months regardless treatment with ascorbic acid. The reason of reduction may be a partial hydrolyses of proteins into amino acids during storage period. Though, no statistically significant difference was observed between treated and untreated samples (Table 1.) In the next three months pH values continued decreasing approximately with the same rate for all the samples. Again, difference between the treated and untreated samples was not statistically significant (p < 0.05) (Table 2).

Ascorbic acid content

Ascorbic acid is an important nutrient and is very sensitive to degradation due to its oxidation compared to other nutrients during food processing and storage [33].

Ascorbic acid content in the untreated fruit samples after three months storage decreased by 37.1 and 42.3% in case of raspberry of Nova and Killarney varieties respectively, and by 32.5 and 4.1% - in case of strawberry of Camarosa and Red Dream varieties respectively (Table 1.). Reduction in ascorbic acid content of untreated fruit samples continued for the next three months as well; maximum drop (28%) was observed for untreated Red Dream

strawberry, and minimum drop (24.6%) was observed for Nova raspberry (Table 2).

Due to the treatment of the fruit samples by 1% and 2% ascorbic acid, content of the last one in fruits after three months storage was increased approximately by 30% and 100% respectively for both varieties of raspberry and was kept practically at the same level for the next six months.

Strawberries seem to be much less able to absorb exogenic ascorbic acid. For instance, content of ascorbic acid in Red Dream fruits treated by 1% ascorbic acid solution did not change after three months storage and remained at the same level as in fresh fruits. 2% treatment resulted in increasing of ascorbic acid content of Red Dream fruits by 11% after three months storage.

For fruits of Camarosa variety the content of vitamin C even decreased by 15% (in case of 1% treatment) and 7% (in case of 2% treatment) after three months frozen storage.

In the next three months content of ascorbic acid in frozen strawberry fruits did not change practically.

TPC and antioxidant potential

Berry fruits are good source of polyphenolics [34]. Phenolic compounds are the main bioactive compounds that contribute to the antioxidant characteristics of fruit [19]. Hence, TPC and

Table 2

Effect of ascorbic acid treatment on quality parameters of berries after 6 months frozen storage (at -20 ± 0.5 °C).

Variety

treatments % with ascorbic acid

Vitamin C mg 100 g

TPC mg 100 g~

FRAP mg equivalents vitamin C x 100 g_1

Strawberry

Raspberry

Red Dream 0 7.05 - 0.13 2.83 0.18 31.12 ± 1.12 119.30 ± 2.52 260.30 ± 2.45

1 7.21 - t0.16 2.71 0.11 43.35 ± 1.52 123.20 ± 3.18a 309.20 ± 4.15

2 7.27 0.52 2.53 0.12 47.32 ± 2.13 126.05 ± 4.51a 345.27 ± 3.58

Camarosa 0 5.83 - 0.31 2.63 0.22 28.15 ± 1.31 120.33 ± 3.72 355.50 ± 4.17

1 5.93 - 0.30 2.45 - 0.17 42.43 ± 2.12 132.20 ± 2.86b 420.20 ± 3.16

2 5.95 - 0.11 2.41 - 0.25 46.31 ± 1.18 140.02 ± 3.50b 445.10 ± 3.51

Nova 0 9.52 t 0.18 2.18 t 0.16 9.12 ± :0.92 82.35 ± 4.54 97.00 ± :2.50

1 9.71 0.22 2.05 0.22 19.18 ± 1.12 84.51 ± 3.35a 105.07 ± 1.88

2 9.78 0.28 2.00 0.12 39.32 ± 2.15 85.50 ± 3.35a 126.80 ± 2.38

Killarney 0 9.12 0.52 1.83 0.20 8.05 ± 0.54 86.25 ± 2.26 103.51 ± 2.77

1 9.27 0.18 1.71 0.31 27.52 ± 1.86 90.10 ± 3.30a 122.27 ± 2.18

2 9.29 0.25 1.62 0.13 40.31 ± 1.12 95.20 ± 3.50a 147.18 ± 2.46

a Difference between treated and untreated samples were not statistically significant (p < 0.05). b Difference between treated and untreated samples were statistically significant (p < 0.01).

T Turmanidze et al. / Annals of Agrarian Science xxx (2017) 1—5

Table 3

Two-way ANOVA analyses of effect of fruit variety and ascorbic acid treatment on the TPC in the first three months storage.

Treatment Variation 315.46 Berries varieties Variation 854.13

Within Variation 0.328 Interaction Variation 30.73

Treatment F-Statistic 958.95 P-Value 0.0005

Berries varieties F -statistic 2596.44 P-Value 0.0005

Interaction F-Statistic 93.43 P-Value 0.0005

Table 4

Two-way ANOVA analyses of effect of fruit variety and ascorbic acid treatment on the TPC in the last three months storage.

Treatment Variation 125.32 Berries varieties Variation 268.87

Within Variation 0.127 Interaction Variation 19

Treatment F-Statistic 980.27 P-Value 0.0005

Berries varieties F -statistic 2103.06 P-Value 0.0005

Interaction F-Statistic 148.64 P-Value 0.0005

antioxidant potential are well correlated in most cases [35].

In the untreated fruits of Red Dream and Camarosa of strawberry varieties during the first three months storage TPC reduced by 20%. In both untreated varieties of raspberry TPC reduced by 14% (Table 1.). In general, ascorbic acid treatment increased polyphenol retaining in all frozen samples of strawberry and raspberry fruits. For Camarosa treated with 2% ascorbic acid this effect was the higher — 15%; for Red Dream the effect was the least — 5%.

The next three months storage practically did not affect TPC in Red Dream variety of strawberry fruits neither untreated nor treated ones. In the rest varieties of berries TPC decreased maximum by 29% (Camarosa 2% treated) and minimum by 9% (Nova untreated) (Table 2).

In order to estimate an effect of fruit variety and ascorbic acid treatment on the TPC, a two-way ANOVA analyses was performed separately for the first and the last three months storage. The results are represented in Tables 3 and 4.

Two-way ANOVA analyses showed that there was a strong ev-

idence (p = 0.0005) to suggest an interaction between fruit variety and ascorbic acid treatment. Also, there was a statistically significant difference (p = 0.0005) between mean values of TPC of the groups. Hence, Tukey's HSD analyses inside fruit variety groups were carried out to find out the groups with different TPC mean values. Such analyses showed that in the first three months there was a statistically significant difference (p < 0.01) between mean values of TPC in the groups of Camarosa, Nova and Killarney treated with 0, 1 and 2% ascorbic acid, whereas there was not statistically significant difference between mean values of TPC in groups of Red Dream.

In the last three months statistically significant difference between mean values of TPC of fruits treated with 0,1 and 2% ascorbic acid was observed only in Camarosa fruits, in the all other varieties there was not statistically significant effect of ascorbic acid treatment.

Antioxidant potential was in good correlation with TPC for all six months of storage (R2 = 0.93, Fig. 1). So, in general, ascorbic acid treatment increased retaining of antioxidant potential in all frozen samples of strawberry and raspberry fruits.

Fresh fruits of Camarosa characterized with the most antioxi-dant potential — 584.00 mg equivalents vitamin C per 100 g fruits. Fresh fruits of Nova revealed the least antioxidant potential — 190.12 mg vitamin C per 100 g fruits. This tendency was kept during storage period as well.

Conclusions

1. Ascorbic acid treatment did not affect TSS content in frozen raspberry and strawberry fruits.

2. pH values of the frozen samples of raspberry and strawberry fruits during storage decreased by the same rate regardless treatment with ascorbic acid.

3. Strawberries and raspberries absorb exogenic ascorbic acid used for treatment of the fruits.

4. Ascorbic acid treatment increases polyphenol retaining in frozen strawberry and raspberry fruits.

700 600 500 a. 400 300 200 100 Correlation between TPC and FRAP

y = 6.2611x-453.61 ♦ R2 = 0.9336 /

/Z /♦

0 50 100 150 200 TPC

Fig. 1. Correlation between TPC and FRAP.

T. Turmanidze et al. / Annals <

5. TPC and FRAP are in good correlation (R2 = 0.93) in both fresh and frozen fruits of strawberry and raspberry during all time of storage period.

Acknowledgements

The research was carried out in the framework of the research

project financed by Shota Rustaveli National Science Foundation, no. 216736.

References

[1] I. Kruashvili, K. Bziava, I. Inashvili, M. Lomishvili, Determination of optimal irrigation rates of agricultural crops under consideration of soil properties and climatic conditions, Ann. Agrar. Sci. 14/3 (2016) 217-221, http://dx.doi.org/ 10.1016/j.aasci.2016.08.006.

[2] I.E. Meskhia, Food Security problems in post-Soviet Georgia, Ann. Agrar. Sci. 14/2 (2016) 46-51, http://dx.doi.org/10.1016/j.aasci.2016.08.006.

[3] S. Skrovankova, D. Sumczynski, J. Mlcek, T. Jurikova, J. Sochor, Bioactive compounds and antioxidant activity in different types of BerriesInt, J. Mol. Med. Sci. 16 (2015) 24673-24706.

[4] B.L. Halvorsen, K. Holte, M.C. Myhrstad, I. Barikmo, E. Hvattum, S.F. Remberg, A.B. Wold, K. Haffner, H. Baugerod, L.F. Andersen, A systematic screening of total antioxidants in dietary plants, J. Nutr. 132 (2002) 461-471.

[5] V.R. De Souza, P.A. Pereira, T.L. Da Silva, L.C. De Oliveira Lima, R. Pio, F. Quiroz, Determination of the bioactive compounds, antioxidant activity and chemical composition of Brazilian blackberry, red raspberry, strawberry, blueberry and sweet cherry fruits, Food Chem. 156 (2014) 362-368.

[6] A. Slatnar, J. Jakopic, F. Stampar, R. Veberic, P. Jamnik, The effect of bioactive compounds on in vitro and in vivo antioxidant activity of different berry juices, PLoS One 7 (2012) 10.

[7] J. Namiesnik, K. Vearasilp, A. Nemirovski, H. Leontowicz, M. Leontowicz, P. Pasko, A.L. Martinez-Ayala, G.A. Gonzalez-Aguilar, M. Suhaj, S. Gorinstein, In vitro studies on the relationship between the antioxidant activities of some berry extracts and their binding properties to serum albumin, Appl. Biochem. Biotech. 182 (2010) 2849-2865.

[8] Z. Diaconeasa, F. Ranga, D. Rugina, L. Leopold, O. Pop, D. Vodnar, L. Cuibus, C. Socaciu, Phenolic content and their antioxidant activity in various berries cultivated in Romania, J. Agr. Food Chem. 72/1 (2015) 99-103.

[9] M.A. Surguladze, M.G. Bezhuashvili, Impact of wine technology on the variability of resveratrol and piceids in Saperavi (Vitis vinifera L.), Ann. Agrar.Sci. 14/3 (2016) 1-4. http://dx.doi.org/10.1016/j.aasci.2016.10.002.

[10] J. Beattie, A. Crozier, G. Duthie, G, Potential health benefits of berries, Curr. Nutr. Food Sci. 1 (2005) 71-86.

[11] A. Karlund, U. Moor, M. Sandell, R.O. Karjalainen, The impact of harvesting, storage and processing factors on health-promoting phytochemicals in berries and fruits, Processes 2 (2014) 596-624.

[12] G.E. Pantelidis, M. Vasilakakis, G.A. Manganaris, G. Diamantidis, Antioxidant capacity, phenol, anthocyanin and ascorbic acid contents in raspberries, blackberries, red currants, gooseberries and Cornelian cherries, Food Chem. 102 (2007) 777-783.

[13] S. Fortalezas, L. Tavares, R. Pimpao, M. Tyagi, V. Pontes, P.M. Alves, G. McDougall, D. Stewart, R.B. Ferreira, C.N. Santos, Antioxidant properties and neuroprotective capacity of strawberry tree fruit (Arbutus unedo), Nutrition 2 (2010) 214-229.

[14] L. Wada, B. Ou, Antioxidant activity and phenolic content of Oregon cane-berries, J. Agr. Food Chem. 50 (2002) 3495-3500.

■avian Science xxx (2017) 1-5 5

[15] R.L. Prior, Fruits and vegetable in the prevention of cellular oxidative damage, Am. J. Clin. Nutr. (2003) 570s-578s.

[16] T. Ichiyanagi, Y. Hatano, S. Matsuo, T. Konishi, Simultaneous comparison of relative reactivities of twelve major anthocyanins in bilberry towards reactive nitrogen species, Chem. Pharm. Bull. 52 (2014) 1312-1315.

[17] W. Zheng, S.Y. Wang, Oxygen radical absorbing capacity of flavonoids and phenolic acids in blueberries, cranberries, chokeberries and lingonberries, J. Agr. Food Chem. 51 (2003) 502-509.

[18] A.M. Panico, F. Garufi, S. Nitto, R. Di Mauro, R.C. Longhitano, G.A. Magri, A. Catalfo, M.E. Serrentino, G. De Guidi, Antioxidant activity and phenolic content of strawberry genotypes from Fragaria x ananassa, Pharm. Biol. 47/3 (2009) 203-208.

[19] B. De Antos, C. Sanchez -Moreno, S. De Pascual-Teresa, M.P. Cano, Fruit freezing principles, in: Y.H. Hui (Ed.), Handbook of Fruit and Fruit Processing, Blackwell Publishing, Iowa, USA, 2006, pp. 59-80.

[20] M.A. Marin, M.P. Cano, Patterns of peroxidase in ripening mango (mangifera indica, L.) fruits, J. Food Sci. 57/3 (1992) 690-692.

[21] G. Skrade, Fruits freezing effects on food quality, in: L.E. Jeremiah (Ed.), Marcel Dekker, New York, USA, 1996.

[22] D.S. Reid, Fruit freezing, in: L.P. Somogyi, H.S. Ramaswamy, Y.H. Hui (Eds.), Processing Fruits: Science and Technology, Technomic Publishing, Lancaster, Ca, 1996, p. 169.

[23] Y.H. Hui, P. Comillon, I. Guerrero, M. Lim, K.D. Murrel, Nip Wai-Kit, Handbook of Frozen Foods, Marcel Dekker Inc, New York, 2004.

[24] M.P. Cano, M.A. Marin, Pigment composition and colour of frozen and canned kiwi fruit slices, J. Agric. Food Chem. 40 (1992) 2141-2146, http://dx.doi.org/ 10.1111/j.1365-26211992.tb08073.x.

[25] O. Fennema, Loss of vitamins in fresh and frozen foods, Food Tech. 31/12 (1977) 32-37.

[26] M. Ciannakouron, P. Taoukis, Kinetic modelling of vitamin C loss in frozen green vegetables under variable storage conditions, Food Chem. 83/1 (2003) 33-41.

[27] M.A. Koyuncu, T. Dilmagunal, Determination of vitamin -C and organic acid changes in strawberry by HPLC during cold storage, Not. Bot. Hort. Agrobot. 38/3 (2010) 95-98.

[28] L.E. Rodriguez-Saona, R.E. Wrolstad, Unit F1.1.1-11, anthocyanins. Extraction, isolation and purification of anthocyanins, in: R.E. Wrolstad (Ed.), Current Protocols in Food Analytical Chemistry, John Wiley & Sons, New York, USA, 2001.

[29] ISO 2173, Fruits and Vegetable Products - Determination of Soluble Solids -Refractometric Method, 2003.

[30] I. Tosun, N.S. Ustun, B. Tekguler, Physical and chemical changes during ripening of blackberry fruits, Sci. Agric. 65 (2008) 87-90, http://dx.doi.org/ 10.1590/S0103-90162008000100012.

[31] T.J. Bond, J.R. Lewis, A. Davis, A.P. Davis, Analysis and purification of catechins and their transformation products, in: C. Santos-Bulga, G. Williamson (Eds.), Methods of Polyphenols Analysis, The Royal Society of Chemistry, USA, 2003.

[32] I.F.F. Benzie, J.J. Strain, The ferric reducing ability of plasma (FRAP) as a measure of "antioxidant power: the FRAP assay, Anal. Biochem. 239 (1996) 70-76.

[33] R.H. Veltman, R.M.A. Kho, C.R. Van-Schaik, M.G. Sanders, J. Oosterhaven, Ascorbic acid and tissue browning in pears under controlled atmosphere conditions, Post. Biol. Tech. 19 (2000) 129-137.

[34] N.M.A. Hassimotto, R.V. Mota, B.R. Cordenunsi, F.M. Lajolo, Physico-chemical characterization and bioactive compounds of blackberry fruits (Rubus sp.) grown in Brazil, Cienc. Tecnol. Aliment. 28/3 (2008) 702-708.

[35] J. Balik, M. Kyselakova, N. Vrchotova, L. Triska, M. Kumsta, J. Veverka, P. Hic, J. Totusek, D. Lefberova, Relations between polyphenols content and antiox-idant activity in vine grapes and leaves, Czech J. Food Sci. 26 (2008) S25-S32.