Extraction, purification and characterization of durian (Durio zibethinus) seed gum

This study was carried out to determine the characteristics of pure durian seed gum in terms of moisture and ash content, mineral content, effect of temperature and pH on viscosity and sugar composition of the gum. Durian seed gum isolated from defatted local durian seeds yielded about 18% of light brown crude gum powder. Further purification of durian seed gum was carried out by barium complexing to give a yield of 1.2% of pure air-dried gum or 0.5% of freeze-dried gum. The purified durian seed gum had 17.9% moisture and 29.8% total ash. Mineral content of durian seed gum was comparable to commercial gum except for zinc content which was quite high in durian seed gum. The viscosity of 1% durian seed gum solution was 65 mPa s at a shear rate of 1000 s(-1) at 29.8 degrees C. The viscosity of fully hydrated gum solutions decreased as temperature increase. It was found that increasing the temperature from 10 to 70 degrees C causing the viscosity to decrease about 34% at shear rate 1000s(-1) and 42% at shear rate 0.93s(-1). The pH of 1% gum solution at room temperature was 6.93, which is quite similar to guar gum. The viscosity of the durian seed gum was found to be highest at the neutral state. Generally, the gum solutions were fairly stable over a wide range of pH (2.0-10.0). Sugar analysis by PC and HPLC revealed the presence Of L-rhamnose, glucose and D-galactose sugars in the hydrolyzed durian seed gum. The gum contained L-rhamnose, glucose and D-galactose in the ratio of 3:9:1. The results indicated that durian seed gum is not a galactomannan. (c) 2006 Elsevier Ltd. All rights reserved.