Quality Indices Changes in Petioles of Celery (Apium graveolens L.) Harvested at Different Physiological Stages

Celery is a vegetable highly appreciated for its fiber content and nutritional value; petioles are preferred for consumption over the leaves. The aim of this study was to determine quality changes in petioles of self blanching celery (Apium graveolens L. 'Golden Boy') harvested at different maturity stages. Total weight (TW), total length (TL), total leaves number (LN) and petiole length (PL) were evaluated at eight physiological stages: 80, 87, 94, 101, 108, 115, 122 and 129 days post-transplanting (dpt). Petiole quality of three zones (external, middle or internal) was analyzed in terms of: colour (hue angle), texture (cutting force), total soluble solids content and titratable acidity. From 80 to 129 dpt, TW and TL of plants increased from 309 to 2094 g and from 47.6 to 81.2 cm, respectively. TW reached a peak of 1.1 kg at 101 dpt. Weight continued increasing after 115 dpt, coinciding with the onset of flowering. Similar results were found for TL. Leaves development was detected until the fourth physiological stage; the number of internal leaves grew to a greater extent than in other zones, with values of 5.0, 4.7 and 7.3 leaves in external, middle and internal zone, respectively. Hue and cutting force were similar in external and middle petioles and were higher than values for internal petioles until the 5th and 6th harvests, respectively. Inflorescence differentiation was detected at 115 dpt, causing an increase in force to cut, TSS and TA. Under the conditions of this study, optimum quality was achieved at 122 dpt, given that yield and petiole quality reached a balance. Delayed harvest increased plant size but could be also associated with lower quality petioles, mainly due to an increase in fibrosity.