Physio-chemical quality attributes of ‘Italia’ grapes from organic and conventional farming at harvest and during storage

This study was aimed to investigate the quality at harvest and during storage of organically and conventionally grown ‘Italia’ grapes, collected from 2 different locations in Southern Italy. Four vineyards were chosen in order to have an organic and a conventional farm in each location. Before harvest, six plants per vineyard were randomly selected and considered as treatment replicate. Three bunches were harvested and labelled from each plant. In laboratory each bunch was weighed and thirty berries per bunch were detached and used for initial determination which included morphological (berry weight and dimension, peel thickness) and physical (berry color and firmness) attributes, maturity indices (respiration rate, soluble solids content and titratable acidity), and nutritional composition (phenol content, antioxidant activity, sugar and organic acid composition, ascorbic acid content). Then, the bunches from each replicate were kept in individual 15-L jars at 0°C and connected to a humidified air flow throughout the whole experiment. After 7 and 14 days of storage, respiration rate, weight loss, physical and nutritional attributes were also monitored on 20 berries per bunch. Location and agricultural practices affected to a different extent several grapes quality attributes, both at harvest and during storage. Maturity stage, sugar content and berry color were significantly affected by the location, while antioxidant-related compounds were significantly higher in organic grapes. Plant production and bunch weight were significantly higher for conventionally grown grapes, which also received the highest evaluation of external appearance, in terms of stalk dehydration and berry general aspect.  Differences among conventional and organic grapes were maintained, for each location, during storage at 0°C. Conventional grapes maintained a higher visual quality during storage, resulting after 14 days below the limit of marketability (score 3) but above the edibility limit (score 2); whereas in one location organic grapes were judged not edible. Results showed a higher nutritional value in grapes obtained with the organic farming system although in terms of visual quality, storability and yield, conventional fruit had a better performance.