ARI REVIEW FOR 2016-2017

POSTHARVEST TECHNOLOGY Configuration of watermelon fruit quality in response to rootstock-mediated harvest maturity and postharvest storage The configuration of watermelon fruit quality was analysed in a multi-factorial approach accounting for the effects of grafting, harvest maturity and postharvest storage. Diploid, seeded, hybrid cv. Pegasus, cultivated as scion on interspecific hybrid squash rootstock TZ148 and as non-grafted control, was stored at 25°C following sequential harvests from the onset of ripening to over-maturity. Delayed rootstock-mediated climax in pulp lycopene and chroma was observed, while both were heightened by postharvest storage when harvest preceded full maturity. Pulp firmness was increased by 46.5% on TZ148, while postharvest decrease in firmness was non- significant. Non-grafted fruits attained their peak in pulp carbohydrate content earlier during ripening. Monosaccharide content declined and sucrose content increased both preharvest and postharvest; overall sugar content declined by 4.3% during storage. Pulp acidity decreased steadily with ripening but was moderately increased by grafting. Citrulline content increased by 12.5% on TZ148; moreover, it climaxed with ripening and declined with storage only in grafted fruit. Grafting enhances pulp texture and bioactive composition. Potential suppression of sugar content as a result of grafting is minimised at full commercial maturity. Brief postharvest ambient storage enhances pulp lycopene and chroma, especially in early-picked fruit, notwithstanding the depletion of monosaccharides and citrulline and a limited deterioration of texture. ( M. Kyriacou, G. Soteriou ) The occurrence of nitrates and nitrites in Mediterranean fresh salad vegetables and its modulation by preharvest practices and postharvest conditions Winter and summer NO 3 - /NO 2 - levels of eleven Mediterranean salad vegetables were surveyed using a validated HPLC-DAD method. Nitrates were highest in rocket both in winter ( x̅ =3974 mg/kg) and summer ( x̅ =3819 mg/kg). High NO3 - accumulators included purslane, chards, dill, coriander and parsley in winter, and dill, chards, coriander, spinach and parsley in summer. Wide intraspecific variability and excess of allowable NO3 - levels (rocket and spinach) highlight the importance of production methods. Occurrence of NO2 - (14-352 mg/kg) was most frequent in winter head cabbage. Three experiments examined the seasonal effects of N rate, application method, formulation and postharvest storage on NO3 - /NO2 - levels of lettuce, rocket and spinach. Nitrogen top-dressing renders spinach and rocket particularly prone to violation of current NO3 - legal limits, especially when total N- supply exceeds 200 kg/ha. Postharvest NO3 - reduction is unlikely before visible signs of quality deterioration and seems to require the exogenous enzymatic activity of microbial nitrate reductase. ( M. Kyriacou, G. Soteriou ) 30 Vegetable Crops