Changes in extract viscosity, amino acid content, and soluble and insoluble β-glucan and dietary fibre content of barley during different high moisture storage conditions

Two experiments were conducted to investigate changes in barley during anaerobic high moisture storage of whole barley. To study the effect of micro-organisms and enzymes present in the grain, samples were irradiated or steamed prior to storage. The effects of enzyme addition and gibberellic acid addition were also investigated. When micro-organisms were not inhibited, considerable lactic acid, acetic acid, and ethanol production occurred, and the numbers of lactic acid bacteria were high. Soluble β-glucan content was lower (P < 0.05) and dietary fibre content was reduced in the high moisture barley stored for 35 or 90 days compared with the dry control barley, regardless of pretreatments or additives. Correspondingly acid extract viscosity was also greatly (P < 0.05) reduced. Insoluble β-glucan content was higher (P < 0.05) in high moisture barley than in dry barley, other than when enzymes with β-glucanase activity were added to the samples. Enzyme addition enhanced fibre breakdown and reduction in acid extract viscosity, while gibberellic acid addition had no effect. Regardless of additives or pretreatments, the reduction in β-glucan content and acid extract viscosity was largest in the first days of storage, and generally only small changes occurred after the sixth day. A correlation of 0.55 to 0.81 (P < 0.05) was found between soluble β-glucan content and acid extract viscosity, while a significant (P < 0.05) negative correlation (−0.74 to −0.90) was found between soluble and insoluble β-glucan content. The correlation between total β-glucan content and acid extract viscosity was of the order of 0.51 to 0.63 (P < 0.05), while the correlation between dietary fibre content and acid extract viscosity was low (0.23 to 0.33) and not significant (P > 0.05). Amino acid content was only slightly affected by high moisture storage. These results demonstrate that high moisture storage of barley results in a rapid change in the fibre content, and that viscosity is reduced due to a reduction in soluble β-glucan content. It appears that this process is not related to activity of enzymes in the grain, or activity of lactic acid bacteria during storage.