Dissolution of (1-3),(1-4)-β-Glucans in Pressurized Hot Water: Quantitative Assessment of the Degradation and the Effective Extraction

The purpose of this work was to study the behavior of (1-3)(1-4)- β -D-glucan in pressurized hot water. For this purpose, solid β -glucan (450 kDa) was put in water and heated at different temperatures (120, 150, and 170°C) for different times (5 to 360 minutes). At 120°C it was found that the highest soluble β -glucan concentration was measured after 60 minutes; at 150 and 170°C optimal times were 45 and 20 minutes, respectively. The maximum amount of β -glucan dissolved in each of the optimal conditions was 1.5, 2.2, and 2.0 g/L, respectively. Under those conditions an important reduction was observed in the molecular weight: at 120°C and 60 min it was 63 kDa; at 150°C and 45 min it was reduced down to 8 kDa; and at 170°C and 20 min it was only 7 kDa. Besides this reduction in the MW some hydrolysis products, such as glucose and HMF, were observed. These results revealed the convenience of using PHW to dissolve β -glucans since the operation times, compared to the conventional process (55°C, 3 h), were reduced despite the fact that the MW was significantly reduced once the β -glucan was dissolved; therefore, PHW can be used to extract β -glucans from barley under controlled conditions in order to prevent severe degradation.