Color, ethylene production, respiration, and compositional changes in broccoli dipped in hot water

Abstract

Color, ethylene production and respiration of broccoli (Brassica oleracea L. var. italica) dipped in hot water (45°C, 10 minutes; 47°C, 7.5 minutes; and 20°C, 10 minutes as control) were measured. Hot-water treatment (HWT) delayed yellowing. Compared to the control, ethylene production and respiration in broccoli dipped at 45°C decreased but recovered, and rates of both were enhanced after 24 and 48 hours, respectively, at 20°C in darkness. There was no recovery of ethylene production or respiration in broccoli dipped at 47°C. Following HWT of 47°C for 7.5 minutes, respiration, starch, sucrose, and soluble protein content of florets and stems decreased dramatically during the first 10 to 24 hours after harvest. At the same time, fructose contents in florets and stems increased. Glucose increased in the florets but decreased within 24 hours in stems. Thereafter, glucose and fructose in florets and stems decreased. Sucrose content in florets and stems increased dramatically within a short period of treatment (<10 hours) and then declined. Protein in HWT florets and stems decreased during the first 24 hours and then increased until 72 hours. Ammonia content was lower in HWT broccoli during the first 24 hours and then increased above the level in the controls.