Influence of harvest time on the quality of some leek cultivars grown in Italy

Four leek cultivars (Arial, Atal, HF1 Charlton and San Giovanni) were collected from 4 November every 3 weeks for 5 months with the aim to evaluate the right period of the harvest. For this goal three parameters were used: aroma compounds, yield per hectare and dry matter. Firstly, the green part of the leek was cut of leaving only the white portion. For the analysis of the volatile compounds the samples were divided longitudinally and then sliced horizontally by hand. The volatile compounds were extracted from 300 g of samples using the microwave technique and then adsorbed on KS 112 apolar resin. The aroma compounds were eluted From the resin with solvent. After completely removing the solvent, the volatile extracts were quali-quantitatively analysed by GC/MS-SIM. The results showed that the 4 cultivars had all the characteristic volatile compounds of Allium porrum spp. L.; in particular disulfides, trisulfides, trithiolanes, thiofenes, and even dithianes were detected. The comparison of the mean values of methyl propyl disulfide and the other two parameters pointed out that the optimal harvest time of the leek cultivars can occur between the 6(th) and 15(th) week from the first harvest.