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