Effect of edible coatings on some quality characteristics of sweet cherries

Gelatine (G), carboxy-methylcellulose (CMC) and soy protein isolate (SPI) edible films were prepared at three different concentrations (1, 3,5%; 2, 3, 4%; and 3, 5,7% respectively) and heated at two different application temperatures (60 and 80°C) before coating sweet cherry (Prunus avium L., cv. 'Sweetheart') fruit. Glycerol was used as a plasticiser, and each film was characterised for their resistance to water, acid and alkali. Standard fruit quality characteristics including changes in stem colour, moisture loss, fruit soluble solids content (SSC) and titratable acidity (TA) were monitored during storage at 2°C. The SPI films were more resistant to water and alkali, while the most resistant to acid were gelatine films. CMC and SPI films showed increased resistance with increasing concentrations, while no concentration effect was observed for G films. Amongst the different films heated at 60°C, the gelatine film ensured the lowest moisture loss during storage, while amongst films heated at 80°C CMC was the most effective at reducing water loss. Fruit SSC for all coated cherries decreased during storage for two weeks, irrespective of the coating. The TA of the fruit coated with CMC and SPI decreased during cold storage and also with increasing concentration. However, there were no significant trends observed for gelatine coated samples. Results obtained in this study indicate that there is great potential to counteract moisture loss, the main parameter associated with quality loss in cherries by application of simple films after harvest.