EFFECT OF DIFFERENT COVERING EFFECT OF DIFFERENT COVERING MATERIALS USED AT PRE-MATERIALS USED AT PRE-

HARVEST STAGE ON QUALITY HARVEST STAGE ON QUALITY AND STORAGE LIFE OF SULTANA AND STORAGE LIFE OF SULTANA

SEEDLESS GRAPESSEEDLESS GRAPESAssoc. Prof. Fatih ŞEN1 Aşkın ALTUN1 , MScMetin KESGİN2 Yüksel SAVAŞ2

1 Ege University, Faculty of Agriculture, Department of Horticulture, İzmir-TURKEY2Viticulture Research Station, Manisa-TURKEY35th World Congress of Vine and

Wine 19th June 2012, İzmir-TURKEY

INTRODUCTION

Grape is one of the most produced and well-known fruit crop all around the world

68 M tonnes

4.2 M tonnes

Source: FAOSTAT, 2011

Table grapes are mostly exported to Russian Federation followed by Germany, Ukraine and Bulgaria..

In the Aegean Region Sultana Seedless variety has been widely cultivated for both table and raisin production. Nearly 1.5 million tonnes of grapes is being produced in the Aegean provinces.

Source: Aegean Exporters Association

In the region, Sultana Seedless prices are at the lowest level when the supply peaks for the fresh market.

In November table grape prices are about 10-30% higher than the prices in September.

Thus supplying Sultana Seedless grapes for longer periods is needed for exportexport and domestic markets. There are two convenient solutions:

On-vine storageCold storage

In recent years, producers delay harvest time by covering vines with various covering materials.

Polypropylene cross-stitch is the common covering material in the Aegean Region.

AIM OF THE RESEARCH

The research work was carried out with different covers to examine their effects on grape quality and storage life.

Additionally, the effect of delayed harvest on fresh table grapes was assessed as continued with cold storage.

Material and MethodThe study was conducted on grapes cv. ‘Sultana Seedless’ in vineyard of Viticulture Research Station located in Manisa province between 2009 and 2011.

Cultural treatments were performed as recommended for the table grapes.

Covering materials were covered on vines in the first week of September in both years.

Polypropylene cross-stitch (PK) •made of polypropylene, •white coloured, •fabric covering material

Lifepack (LP) •has three layers •water-resistant •8% UV additive top layer

Mogul (MG)•made of polypropylene•white coloured, •light transmittance: 70% •3% UV additive

Transparent polyethylene (PE) •made of polypropylene•transparent coloured •light transmittance: 95% •3% UV additive

Grapes under cover were harvested nearly one month after than those maturing under open conditions.

Harvested grapes were placed in plastic boxes and later packaged into bags before pre-cooling.

Packaged grapes

E.U.Z.F. Storage Unit

Pre-cooling24h, -0.5°C %95 RH

Storage(-0.5 ± 0.5°C %90-95

RH)

Placing SO2-generating pads and closing off PE

bags

In the first year, the grapes were kept for 90 days and in the second year for 120 days in storage.

Grapes were sampled at harvest, and on 60th, and 90th days and in the second year also on the 120th day of storage.

Quality parameters analyzed

Berry removal force: Penetrometer (Somyf tec, N)

Color: Minolta colorimeter (CIE-L*, a*, b*)Total soluble solids (TSS, %)Titratable acidity (TA, g tartaric

acid/100ml), (Karaçalı, 2009)Maturity index Sensory analysisDecay incidence (Anonymous, 1996)

Temperature and Humidity

Under cover tempature and relative humidity was measured and saved with data loggers.

Results and DiscussionBerry Removal Force

• MG covering material has given higher results than others.

• After 90 days berry removal forces began to decrease.

ColourEffects of covering materials on colour values seemed similar in both years of the study.

PK, 90th day

LP, 90th day

MG, 90th dayPE, 90th day

Total soluble solids (%)

• Non significant in the first year.

• In the second year PE was found enhancing TSS compared to other covering materials.

Titratable acidity (TA)

• In the first year, no significant effect on TA.

• PK has given higher results than others.

• At the end of the storage, TA has a decrease trend comparing to pre-storage results.

Maturity Index

• Limited changes in the first year.

• PE has showed higher results in all cover materials in the second year.

Sensory analysis

• Higher scores resulted from good looking.

• Low flavour and crunchiness values.

No SO2 damage, odor or taste has been observed during cold storage phase.

Decay incidence

LP, 90th day

PE, 90th day

MG, 90th day

Moderate deterioration observed in grapes covered with PK covering material on the 120th day of storage.

PK, 120th day

Stem Browning

MG

PE

PK

LP

Using dual release SO2-generating pads and convenient pre-cooling and storage conditions were effective in non-existence of stem browning.

CONCLUSIONGrapes can be stored for 4 months

successfully with the combination of covering materials (1 month) and cold storage (3 months).

After 120 days of storage grapes seem good in shape but not in flavour and crunchiness.

There are not prominent differences in effects of covering materials on berry colour.

PE covering material is not recommended because of causing damages on grapevine leaves.

MG covering material can be preferred because of yielding higher berry removal force values.

Teşekkürler

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