TOTAL ANTIOXIDANT TOTAL ANTIOXIDANT ACTIVITY (TAA) OF BELL ACTIVITY (TAA) OF BELL

PEPPER PEPPER DURING PROLONGED DURING PROLONGED

STORAGE ON LOW STORAGE ON LOW TEMPERATURETEMPERATURE

Zoran ILIC.,Zoran ILIC.,11 Avital BEN-YOSEF., Yaccov PARTZELAN., Avital BEN-YOSEF., Yaccov PARTZELAN., Sharon ALKALAI-TUVIA and Elazar FALLIK ²Sharon ALKALAI-TUVIA and Elazar FALLIK ²

11Faculty of Agriculture, Zubin Potok., Kosovska Mitrovica, Faculty of Agriculture, Zubin Potok., Kosovska Mitrovica, SerbiaSerbia

²ARO- ²ARO- ТТhe Volcani Center, Postharvest Science of Fresh he Volcani Center, Postharvest Science of Fresh Produce, Israel Produce, Israel

Bell pepper is one of the commercially important vegetable crops and may be green, purple (unripe), red, yellow, orange, or brown when ripe. Peppers are rich in both hydrophilic antioxidants, such as vitamin C, and lipophilic ones, such as carotenoids and vitamin E and in potassium, and are low in calories.

Red sweet pepper (Capsicum annuum L.) cultivars have been identified as potential vegetables with high antioxidant activity. Fresh sweet pepper have exceptionally high ascorbic acid (0,15 to 2,0 mg.g-1fresh weight) compared to other fruit and vegetables. Ascorbic acid was the main form of vitamin C, and its content increased as the pepper reached maturity. For green mature, breaker and red peppers values of 107,3, 129,6 and 154,3 mg/100g edible portion were found, Martinez et al., 2005.

The attractive red colour is due to the various carotenoid pigments. The red ripe stage had a relevant impact on the carotenoids content of polyphenols, while red ripe fruits had the highest content of vitamin C and provitamin A.

Stored red ripe peppers showed a significant loss in vitamin C content, around 25%.

INTRODUCTION INTRODUCTION

MATERIAL AND METHODSMATERIAL AND METHODS

Red bell pepperRed bell pepper ( (Capsicum annuum L.),Capsicum annuum L.), cv. cv. SelicaSelica was grown in the plastic house (Jordan Valley - Israel) was grown in the plastic house (Jordan Valley - Israel) under winter conditions. under winter conditions.

Fruit were harvested in Fruit were harvested in MarchMarch at the ripe stage at the ripe stage (11,4% (11,4% D.M.) D.M.) of uniform size and colour. After harvest of uniform size and colour. After harvest fruit were placed on commercial machines for cleaning fruit were placed on commercial machines for cleaning and disinfecting pepper fruit. A unique and rapid and disinfecting pepper fruit. A unique and rapid method, method, Fallik et al., Fallik et al., 1996 for simultaneously rinsing 1996 for simultaneously rinsing and disinfecting sweet pepper using hot water with and disinfecting sweet pepper using hot water with 5555C for C for 1212ssecec. .

Control-unheated fruits wash only in cold Control-unheated fruits wash only in cold water were either placed at 2ºC. Half of this water were either placed at 2ºC. Half of this fruits were individually shrink-wrapped with fruits were individually shrink-wrapped with Cryovac D-955 film and stored also at 2ºC Cryovac D-955 film and stored also at 2ºC and relative humidity of 90% (R.V.) during and relative humidity of 90% (R.V.) during three weeks.three weeks.

Weight loss was Weight loss was expressed as expressed as percentage of weight percentage of weight loss from the initial loss from the initial weight of five fruits. weight of five fruits. Total soluble solid was Total soluble solid was measured using a measured using a digital refractometer. digital refractometer. Fruit color was Fruit color was assessed by Minolna assessed by Minolna colorimeter, firmness colorimeter, firmness was reassured non-was reassured non-destructively with destructively with CI- chilling injury CI- chilling injury measured visually as measured visually as surface lesion on the surface lesion on the fruits. Fruit was fruits. Fruit was considered decaconsidered decayed yed once fungal mycelia once fungal mycelia appeared on the peel appeared on the peel or calyx.or calyx.

Quality parameters were evaluated immediately Quality parameters were evaluated immediately after harvest after harvest and at the end of 21 days storage atand at the end of 21 days storage at 7C and 2C 7C and 2C ++ 33days at 20C days at 20C (shelf life(shelf life))

Total antioxidants activity (hydrolytic and lipophilic) was evaluated as scavenging capacity towards by measuring the decolorization of the cation radical of 2,2|-azino-bis-(3-ethylbenthiazoline-6-sulphonic acid) (ABTS+) and expressed as Trolox equivalent antioxidant capacity (TEAC) Vinokur and Rodov, 2006.

The extraction procedure was The extraction procedure was developed to allow isolation of hydrophilic developed to allow isolation of hydrophilic and lipophilic fractions from fresh fruits and lipophilic fractions from fresh fruits or vegetables without preliminary drying. or vegetables without preliminary drying. The procedure was based on stepwise The procedure was based on stepwise extraction of the plant material with extraction of the plant material with acetate buffer, acetone and hexane and acetate buffer, acetone and hexane and repeated partition of water-soluble and repeated partition of water-soluble and water-insoluble portions. At first stage, the water-insoluble portions. At first stage, the fresh plant material was homogenized in fresh plant material was homogenized in acetate buffer pH 4,3 and the homogenate acetate buffer pH 4,3 and the homogenate extracted/dehydrated with three successive extracted/dehydrated with three successive portions of acetone, each step followed by portions of acetone, each step followed by centrifugation and collection of the centrifugation and collection of the supernatant. The acetone-water supernatant. The acetone-water supernatant fractions from the three supernatant fractions from the three extractions were pooled. After the acetone extractions were pooled. After the acetone extraction, the dehydrated pellet was extraction, the dehydrated pellet was extracted three times with hexane and extracted three times with hexane and supernatants collected and pooled. The supernatants collected and pooled. The traces of lipophilic compounds were traces of lipophilic compounds were extracted from the pooled acetone-water extracted from the pooled acetone-water extract by partitioning with hexane. The extract by partitioning with hexane. The non-polar fraction obtained from this non-polar fraction obtained from this operation was subjected to another operation was subjected to another partition with water in order to extract the partition with water in order to extract the traces of hydrophilic compounds. After traces of hydrophilic compounds. After pooling the fractions, two samples were pooling the fractions, two samples were obtained, hydrophilic (water/acetone obtained, hydrophilic (water/acetone extract), and lipophilic (hexane extract). extract), and lipophilic (hexane extract). Until the partition stage, all the extraction Until the partition stage, all the extraction steps for one plant sample were performed steps for one plant sample were performed in a single centrifuge test tube; the in a single centrifuge test tube; the partition required two test tubes per plant partition required two test tubes per plant sample. sample.

The discoloration test was performed in plastic cuvettes by adding 10µL of test sample to 1mL of acidified ethanolic solution of ABTS+ and measured as optical density at 734nm after 15 min of incubation at room temperature in comparison with blank sample. The 1mM solution of 6-hydroxy -2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox a water-soluble derivate of the vitamin E) was used as a standard, and the radical-scavenging activity of samples was expressed as Trolox equivalent antioxidant capacity (TEAC).

After pooling the fractions, two samples were obtained, After pooling the fractions, two samples were obtained, hydrophilic (water/acetone extract), and lipophilic (hexane hydrophilic (water/acetone extract), and lipophilic (hexane extract). Until the partition stage, all the extraction steps for one extract). Until the partition stage, all the extraction steps for one plant sample were performed in a single centrifuge test tube; the plant sample were performed in a single centrifuge test tube; the partition required two test tubes per plant sample.partition required two test tubes per plant sample.

The antioxidant activity of the measured extract in Trolox equivalents (TE,mM) is calculated as follows :

TE = Cstandard . (Asample – A blank) / (Asample – A blank)

where Cstandard is standard concentration (usually equal 1mM), Asample , Ablank and Astandard are absorbance values of the samples, blank and standard, accordingly.

For example, if obtained TE value is equal 0,5mM it means that 1ml of the measured extract has the same antioxidant activity as 1ml of Trolox solution of the concentration 0,5mM. For calculating Trolox equivalent antioxidant capacity (TEAC) in plant tissue per weight unit, the extract volume V and the weight of the extracted tissue M should be taken into consideration in the :

TEAC (mM TE/g) = (TE. V) / (1000 . M)

Total antioxidant activity (TAA)Ukupna antioksidativna aktivnost

µmol TE/g fresh weighLIPOPHYLIC HYDROPHYLIC TOTAL

TE TEAC TE TEAC TEAC

Start T0 0,06 0,84 0,34 4,05 4,89

AFTER 3WEEK STORAGE ON 70C

70C T21 0,10 1,55 0,29 3,45 4,00

70C T 21+3 0,15 2,31 0,31 3,76 6,07

AFTER 3 WEEKS STORAGE ON 20C

20C Cold Water -T21 0,09 1,30 0,29 3,42 4,72

20C C.W +shrink -T21 0,09 1,40 0,26 2,99 4,39

20C HWRB - T21 0,080,08 1,151,15 0,30 3,53 4,684,68

20C HWRB+shrink-T21 0,08 1,08 0,29 3,44 4,61

AFTER 3 WEEKS ON 20C + 3 DAY ON 200C (Shelf life)

20C Cold Water -T21+3d. shelf life 0,14 2,04 0,33 3,93 5,97

20C C.W +shrink -T21+3 0,14 1,961,96 0,26 3,20 5,165,16

20C Hot.Water.R.B -T21+3 0,14 2,06 0,32 3,82 5,88

20C HWRB+shrink-T21+3 0,11 1,87 0,30 3,57 5,44

22ººC C 7 7ºº

3 weeeks storage3 weeeks storage

HWRB + shrink HWRB + shrink Contol Contol

Content of carotenoides in pepper fruit Content of carotenoides in pepper fruit after 3weeks storage on 2after 3weeks storage on 2ººC +3days on 20C +3days on 20ººC(shelf C(shelf

life)life)Content of carotenoides mg/g

Start T0 0,10

70C T21 0,17

70C T 21+3 0,29

20C Cold Water -T21 0,13

20C C.W +shrink -T21 0,12

20C HWRB - T21 0,11

20C HWRB+shrink-T21 0,10

20C Cold Water -T21+3d. shelf life 0,22

20C C.W +shrink -T21+3 0,21

20C Hot.Water.R.B -T21+3 0,22

20C HWRB+shrink-T21+3 0,21

WaterLoss %

Firmness < 2 soft2-3 firm

> 2 very firm

Decayfruit %

DecayCalyx %

Color 1-4

Chillinginjury - CI

HWRB – 70C 3,31 3,2 18,2 6,0 3.5 0

Cold water – 20C 3,95 2,6 30 23.6 3.25 78,5

HWRB 4,24 2,5 28,3 25,2 3.5 53,5

Cold water +shrink 0,47 2,2 14,5 7,2 3.25 9,2

HWRB+shrink 0,56 2,0 13 7,9 3.0 8,1

Quality parameters after 3 weeks storage on 7Quality parameters after 3 weeks storage on 7ººC or C or 22ººC+ 3 dayson 20C+ 3 dayson 20ººCC

Chilling injury Chilling injury Decay calyxDecay calyx

Harvest, transport, packing house, postharvest Harvest, transport, packing house, postharvest treatment ,sorting, packaging, storage and treatment ,sorting, packaging, storage and

distribution – exportdistribution – export pepper fruit from Israelpepper fruit from Israel

Prevoz, distribucija i prodaja paprike u okolini Prevoz, distribucija i prodaja paprike u okolini KruševcaKruševca septembar 2007 septembar 2007

Zar mora baš ovako ?Zar mora baš ovako ?