Relationship Between Physical Characteristics of Cereal Polysaccharides and Soft Tribology-The Importance of Grain Source and Malting Modification

Starch and non-starch polysaccharides ((N)SPs) are relevant in cereal-based beverages. Although their molar mass and conformation are important to the sensory characteristics of beer and non-alcoholic beer, their triggering mechanism in the mouth is not fully understood. Soft tribology has emerged as a tool to mimic oral processing (drinking). The contribution of each (N)SPs to the friction coefficient can be determined when they are enzymatically isolated and characterized by chromatography techniques. Thus, this work aimed to study the relationship between the physical characteristics of isolated (N)SPs and their possible contribution to oral processing through soft tribology (friction). To accomplish this, this research analyzes the effect of grain source (barley, wheat, and oats) and its modification (by steeping degree at two levels) to the (N)SPs´ physical characteristics in wort produced on a laboratory scale. Different characteristics were present in the (N)SPs due to the grain source and the degree of modification. When comparing the impact of the grain source, the malted oats showed the highest molar masses. A higher modification degree produced smaller and more compact structures except for wheat's arabinoxylans and dextrins. The conformation ratio ( $r_{\mathrm{rms}}/r_{\mathrm{hyd}}$ ) values indicate the existence of sphere and micro-gel structures within each (N)SPs, with branches in arabinoxylans and dextrins. Subsequently, soft tribology was measured on all the worts and their correlation to the (N)SPs' data was performed by multivariate analysis. The wort produced with high modification grains generated higher friction responses. However, this was only statistically significant in barley samples. The multivariate analysis showed that within the mouth (tongue) velocity, the apparent density of the (N)SPs, and the molar mass of arabinoxylans and β-glucans may influence the friction response and, hence, the oral processing in the mouth during oral processing (drinking).