Heat shock reduces browning of fresh-cut celery petioles

Preparation of 5 mm segments of celery petioles induced an increase in the activity of phenylalanine ammonia-lyase (PAL, EC 4.3.1.5), and subsequent tissue browning potential (absorbance of a 70% methanol tissue extract at 320 nm g(-1) FW). The level of constitutive and wound-induced PAL activity was higher in vascular than in cortex tissue, and lowest in epidermal tissue. Heat shocking excised petiole segments (e.g. 50 degreesC for 90 s) significantly reduced the rise in wound-induced PAL and browning potential. Pithiness of the petiole segments did not alter the effectiveness of the heat shock treatments, nor was pithiness enhanced by the treatments. As storage life was extended, however, decay and the protrusion of vascular bundles from the cut ends of the segments became important factors in limiting shelf-life. (C) 2002 Elsevier Science B.V. All rights reserved.