Optimization of the β-glucan extraction conditions from different waxy barley cultivars

The purpose of this work is to provide a complete study of the influence of several operational parameters on the aqueous extraction of β-glucan from barley, and to find an optimal combination of factors that maximize the extraction yield. Temperature, pH, extraction time, particle size, stirring rate and solvent:flour ratio were identified as the critical factors affecting the extraction process. Preliminary experiments were useful to set the extraction temperature at 55 °C (maximum extractability of β-glucan below gelatinization temperature of starch), and pH close to neutrality. In order to determine the optimal combination of the other four factors, a Taguchi experimental design approach was used: four variables (three levels) in L9 orthogonal array. Nine different trials were conducted in duplicate for two different waxy barley cultivars: D24 (hulled; 6.02% β-glucan) and H13 (hulless; 4.64% β-glucan). The optimal conditions obtained from the signal to noise ratio analysis were: particle size, 100 μm; solvent:flour ratio equal to 5; stirring rate, 1000 rpm and extraction time, 3 h. The confirmatory experiment conducted with the optimal conditions provided an extraction yield of 73.4 ± 1.2% for D24 and 62.3 ± 1.8% for H13, corresponding to the maximum and showing that these conditions are valid regardless the composition of the used barley.