Alternative atmosphere treatments for keeping quality of ‘Autumn seedless’ table grapes during long-term cold storage

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Abstract

White seedless table grapes (Vitis vinifera cv. Autumn seedless) were stored under several gas treatments for up to 60 days at 0 °C followed by 7 days in air at 15 °C. To generate a modified atmosphere packaging (MAP) of 15 kPa O2 and 10 kPa CO2, a 35 μm thick microperforated polypropylene (PP) film with and without 0.7 g Na2S2O5 kg−1 was used. A controlled atmosphere (CA) of 5 kPa O2+15 kPa CO2 and continuous exposure to 0.1 μl l−1 O3 enriched air were also tested. As a control, macroperforated PP film was used. After shelf life, control berries showed the highest decrease in lightness and greenness while slight changes for gas-treated berries were found. At any time, no noticeable changes in firmness, SSC, pH, titratable acidity, maturity index, aroma and softness were detected. At the end of the experiment, severe browning of the rachis in control clusters occurred, due to the high weight losses reached (9.65%). Control clusters showed the highest fungal infection (over 9%), mainly caused by Botrytis cinerea. Visual appearance and eating texture of berries under gas treatments were higher after shelf life than in control fruit, with no differences among treatments except for CA-treated grapes. A progressive increase in the total sugar contents in all treatments was found. Glucose and fructose, in almost equal quantity, were the main sugars. Principal organic acids were tartaric and malic, and compared to values at harvest, no differences for any treatment at any sampling time were found. As a main conclusion, the gas treatment could be an alternative to replace the use of SO2 for keeping quality of ‘Autumn seedless’ grapes. MAP with 15 kPa O2+10 kPa CO2 provided the best results and also had a lower cost.

Introduction

Table grape (Vitis vinifera L.) is an important crop produced in the Mediterranean coastal area of Spain, and is well adapted to these growing conditions. The development of new table grape cultivars with high value because of seedlessness and precocity has stimulated market interest. The table grape is a non-climacteric fruit with low physiological activity and is sensitive to water loss and fungal infection (mainly caused by Botrytis cinerea Pers) during postharvest handling. The most common method to control decay during cold storage of clusters is fumigation with SO2 (Harvey and Uota, 1978, Luvisi et al., 1992, Crisosto et al., 1994). However, SO2 is highly corrosive to metals, injurious to most other fresh fruit and causes injuries to rachis and berries if used excessively (Nelson, 1985). Also, SO2 residues are dangerous to people allergic to sulfites, 10 μl l−1 being the maximum tolerance to sulfite residues in fruit established by the U.S. Food and Drug Administration (Crisosto et al., 1994).

Nowadays some alternative techniques to SO2 seem to be useful to prevent decay in table grapes, such as controlled atmospheres (CA) (Yahia et al., 1983, Cimino et al., 1987, Eris et al., 1993, Kader, 1997, Basiouny, 1998, Crisosto et al., 2002), modified atmosphere packaging (MAP) (Yamashita et al., 2000, Artes-Hdez et al., 2000b) and the use of O3 (Sarig et al., 1996, Artes-Hdez et al., 2002, Palou et al., 2002).

‘Autumn seedless’ is one of the latest seedless table grapes grown in Spain, with white flesh and green skin colour, harvested from the middle of August to the middle of September. Much is known about the postharvest behaviour of many cultivars of Vitis, although there is little information on ‘Autumn seedless’ reported.

The aim of the present work was to study the postharvest behaviour of ‘Autumn seedless’ table grapes under alternative gas treatments for keeping quality during long-term cold storage. From the best of our knowledge studies on the influence of these treatments on chemical constituents and quality attribute changes during cold storage and shelf life of this cultivar have not been reported.

Section snippets

Plant material and experimental design

‘Autumn seedless’ table grapes were harvested on 9 September in Cieza (Murcia), close to the Mediterranean coast of Spain. Clusters were transported about 40 km by car to the laboratory and were immediately forced-air precooled at 0 °C. The following day, clusters were selected on the basis of uniform size, colour, firmness and freedom from evident defects or diseases. Clusters were randomly distributed into batches with five replicates of one cluster per treatment. Clusters of about 500 g each

Gas analysis

As expected, MPP conditions maintained an air atmosphere during all the experiment of 20.9 kPa O2 and 0.03 kPa CO2. CA treatment maintained 5 kPa O2 and 15 kPa CO2 levels during cold storage, while MAP treatments reached a steady-state atmosphere of 15 kPa O2 and 10 kPa CO2 by about 21 days (Fig. 1). Levels of O3 during cold storage ranged from 0.08 to 0.12 μl l−1 throughout cold storage with a mean value of 0.1 μl l−1.

Colour

Compared to values at harvest, a slight decrease in lightness (L*) occurred in all

Conclusions

Some gas treatments may be a commercial alternative to the use of SO2 generators for keeping quality of ‘Autumn seedless’ grapes, in cold storage for up to 2 months at 0 °C followed by 1 week at 15 °C in air.

MAP of 15 kPa O2 and 10 kPa CO2 may be useful for commercial application and consumer satisfaction, due to being the cheapest and easiest technique. This treatment was the best for maintaining fruit quality close to that at harvest, with few differences from results obtained by adding 0.7 g Na2S2

Acknowledgements

The authors are grateful to Spanish CICYT-FEDER (1FD-0760-C03-01) for financial support, to J. Carreño for providing table grapes, and to CEBAS-CSIC (Murcia, Spain) and to Centro de Capacitaciones Agrarias (Molina de Segura, Murcia, Spain) for providing facilities.

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