Effect of Incubation, Enzymes and Thermal Pre-treatments on the Quality of Pumpkin Juice

Abstract

Incubating fresh pumpkin (Cucurbita pepo L.) vegetable slices treated with thermal pre-treatments and a commercial exogenous enzyme preparation cellulase and α-amylase produced a pumpkin juice. HPLC was also carried out to fractionate the major sugar component found in fresh and treated pumpkin juice. Sucrose was the major sugar of the pumpkin juice which hydrolysis during water and steam blanching and cellulase enzyme pre-treatments to glucose and fructose. Results concluded that the incubated pumpkin have the lowest WIS and water content compared to the fresh pumpkin juice without treatment. No pectin-methyl-esterase (PME) activity was found in water, steam and enzymes pre-treatments of pumpkin juice compared with the fresh pumpkin juice without treatment. It was found that the yield was increased in water blanching, followed by cellulase addition and then steam blanching. The inhibitory effect of various thermal and enzymes pre-treatments based on a*-values measurements at their high time and maximum concentrations for pumpkin juice treated in the following decrease order steam blanching > microwave > water blanching > α-amylase enzyme > cellulase enzyme. This research proved that pumpkin can be used as a pumpkin juice with thermal and enzymes pre-treatments after incubated fresh pumpkin vegetable slices at 55°C for 3 hours.