Determination of Cytolytic Malt Modification – Part I: Influence of Variety Characteristics

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 rms / r 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).

Influence of the malting conditions on the modification and variation in the physicochemical properties and volatile composition of barley (Hordeum vulgare L.), rye (Secale cereale L.), and quinoa (Chenopodium quinoa Willd.) malts

The traditional malted cereal used primarily for beverages is barley (Hordeum vulgare L.), while rye (Secale cereale L.) is mainly used in baked goods. In contrast, quinoa (Chenopodium quinoa Willd.) is a gluten-free pseudocereal, rich in starch and high-quality proteins, that can be used similarly to cereals. Their physicochemical properties and volatile compositions (e.g., aroma compounds) directly influence the finished food products. The sharp bitterness of unprocessed rye and the earthy aroma of native quinoa can interfere with the development and acceptance of food products. Malting is known to improve the processing and sensory properties of barley. A face-centered, central composite design was used to investigate the individual and interactive effects of three malting parameters (i.e., steep moisture (SM), germination temperature (T), and germination time (t)) on malt quality indicators (e.g., extract) and volatile formation (e.g., 3-methylbutanal) in rye and quinoa, and were compared to barley. The malt modification predictive models were then used to determine standard malting regimes for brewing quality malts. The malting parameters for the steeping and germination stages were: 43 %, 15 °C, and 6 d for barley; 45 %, 12 °C, and 8 d for rye; and 46 %, 16 °C, 6 d for quinoa. Malt modification and volatile formation were primarily associated with the interactive effect of germination temperature and time. Conversely, steep moisture had limited impact on malt modification but strongly regulated the formation of 34 known (pseudo)cereal volatile compounds. Principal component analysis (PCA) of the volatile data identified (pseudo)cereal specific volatile patterns. Aldehydes were characteristic in the cereal malts, particularly barley, whereas phenyl compounds and pyrazines were abundant in rye and quinoa malts, respectively. Controlling (pseudo)cereal modification and volatile development through the malting process could help deliver targeted sensory properties and improve the acceptance of malt-based food products.