Wir gratulieren Dr. rer. nat. Rolando Cesar Moreno Ravelo herzlich zur erfolgreich abgeschlossenen Promotion!
Seine Dissertation mit dem Titel „From structure to function — the role of (non-)starch polysaccharides on palate fullness and mouthfeel of cereal-based beverages“ leistet einen wertvollen Beitrag zum Verständnis der sensorischen Eigenschaften getreidebasierter Getränke.

Durch seine engagierte wissenschaftliche Arbeit am Lehrstuhl für Brau- und Getränketechnologie hat Herr Dr. Moreno Ravelo wichtige Impulse für die Forschung gesetzt und unser Team fachlich wie menschlich bereichert.

Wir danken ihm herzlich für die gemeinsame Zeit und wünschen ihm für seine weitere berufliche und persönliche Zukunft alles Gute und viel Erfolg.

Inhalt

In seiner Dissertation beschäftigte sich Rolando Moreno mit den physikalischen Eigenschaften von Polysacchariden in getreidebasierten Getränken und deren potenziellem Einfluss auf Vollmundigkeit und Mundgefühl, zwei Sensorik-Attribute, die insbesondere bei alkoholfreien Bieren relevant sind. Er identifizierte molare Masse und Konformation von Bierpolymeren als zentrale Parameter, die die Wahrnehmung dieser Attribute erklären könnten.

Moreno führte ein Screening alkoholfreier Biere durch und zeigte, dass die hochmolekulare Polysaccharid-Fraktion (HN-SP) – bestehend aus Arabinoxylanen, β-Glucanen und Dextrinen – entscheidend für Vollmundigkeit und Mundgefühl sein kann. Außerdem konnte er nachweisen, dass der Mälzungsprozess diese Polysaccharide modifiziert und dadurch deren physikalische Eigenschaften verändert.

Zur detaillierten Charakterisierung der einzelnen Polysaccharide entwickelte er eine Methode zur Isolation und Analyse der molaren Masse und Konformation von AXs, BGs und DXs. Er fand, dass unterschiedliche Getreidearten und Mälzgrade zu variierenden molaren Massen und Konformationen führen. Auf Basis dieser physikalischen Daten ließ sich ableiten, dass Dextrine vor allem mit Vollmundigkeit assoziiert sind, während Arabinoxylane und β-Glucane wässriges oder schleimiges Mundgefühl begünstigen könnten.

Seine Arbeit verdeutlicht, dass die physikalische Form der Polysaccharide ein Schlüsselfaktor für die sensorische Wahrnehmung ist und bietet Ansatzpunkte für die gezielte Entwicklung von Rohstoffen, die Vollmundigkeit und Mundgefühl in getreidebasierten Getränken positiv beeinflussen können.

Mehr Informationen finden Sie auf mediaTUM: https://mediatum.ub.tum.de/?id=1767397

Wissenschaftliche Veröffentlichungen am BGT

Moreno Ravelo, R. C., Neugrodda, C., Gastl, M., Becker, T.: Contribution of (non-)starch polysaccharides to distinctive sensory perception in beer – Significance of their physical and friction characteristics. Current Research in Food Science 11, 2025

doi:10.1016/j.crfs.2025.101118

The palate fullness (body) and mouthfeel are important sensory attributes influencing the consumers’ beer preference. Among the several parameters affecting these attributes, recent research suggests that the physical characteristics (molar mass and conformation) of starch (dextrins) and non-starch polysaccharides (arabinoxylans and β-glucans) play a critical role. However, the lack of information regarding the physical state of these polysaccharides in beer hinders the sensory evaluation of each component. A method was recently introduced to isolate and solely characterize the molar mass and conformation of beer’s starch and non-starch polysaccharides in solution by AF4-MALS-DRI. Therefore, this research evaluated the relationship between the molar mass and conformation of arabinoxylans, β-glucans, and dextrins with the palate fullness and mouthfeel sensorial perception. Additionally, friction, assessed by soft tribology, was analyzed as a triggering mechanism during oral processing. Grains from different sources modified at a low level (steeping degree as parameter) were used to produce bottom-fermented beers with diverse physical characteristics. Regarding the friction response, the variation of correlation behavior at different sliding velocities suggests that the human sensory panel might perceive the palate fullness and mouthfeel at different stages during oral processing. The multivariate analysis suggests that the conformation ratio, r(rms)/r(hyd) rrms/rhyd„>, from each polysaccharide triggers a distinctive sensory response, being dextrins related to palate fullness while arabinoxylans and β-glucans to mouthfeel. Furthermore, the beer sample substituted with barley modified at a low level presented an increase of branched dextrins in comparison to the (unsubstituted) control, which was related to its increase in palate fullness intensity.

Moreno Ravelo, R.C., Gastl, M., Becker, T.: Relationship Between Physical Characteristics of Cereal Polysaccharides and Soft Tribology—The Importance of Grain Source and Malting Modification. Food Science & Nutrition 13 (1), 2025

doi:10.1002/fsn3.4699

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).

Moreno Ravelo, R. C., Gastl, M., Becker, T.: Characterization of molar mass and conformation of relevant (non-)starch polysaccharides in cereal-based beverages. International Journal of Biological Macromolecules 261 (Part 2), 2024

doi:10.1016/j.ijbiomac.2024.129942

Moreno Ravelo, R. C., Gastl, M., Becker, T.: Influence of dextrins and β-glucans on palate fullness and mouthfeel of beer. European Food Research and Technology 250 (2), 2024, 495-509

doi:10.1007/s00217-023-04394-8

Palate fullness (PF) and mouthfeel are important sensory attributes influencing beer quality. The molar mass of starch (dextrins) and non-starch (β-glucans) polysaccharides may influence PF (pleasant) or mouthfeel (sliminess, unpleasant), respectively. Therefore, this research aims to generate beer with wide physico-chemical responses based on various raw material characteristics to study its relation to PF and mouthfeel. To accomplish this, ten barley varieties (two harvest locations and years) were classified into three groups based on their modification characteristics. To intensify response variation, barley was malted at two modification levels (parameter steeping degree), generating 55 independent malts used to brew the same number of standardized bottom fermented beers. A trained sensory panel evaluated PF (intensity and quality) and mouthfeel (e.g., slimy) descriptors. Additionally, beers were fractionated by asymmetrical flow field-flow fractionation (AF4) in three different fractions and their molar masses were determined. The average molar mass of big size (> 10 nm) dextrins and β-glucans AF4 fraction increased analogously to barley modification characteristics. For sensory data evaluation, only beer samples brewed with malts inside the recommended brewing specifications were considered (β-glucan content in malt < 350 mg/L, ISO 65 °C). PF quality was lower on samples with β-glucan content < 100 mg/L. This group also contained fewer dextrins (attenuation > 87.4 ± 1.5%), suggesting that the balance of β-glucans and dextrins is important for PF quality. This work indicates that molar mass of starch and non-starch polysaccharides, affected by barley variety and its modification level, influences sensory perception, and hence, beer quality.

Moreno Ravelo, R. C., Masch, J. D., Gastl, M., Becker, T.: Effect of molar mass and size of non-alcoholic beer fractions and their relevance toward palate fullness intensity. Food Research International. 170 (2023): 112725
https://doi.org/10.1016/j.foodres.2023.112725

Palate fullness intensity and mouthfeel descriptors are essential sensory characteristics of non-alcoholic beers (NABs). The descriptor’s perception might be influenced by the molar distribution of the non-volatile matrix in cereal-based beverages like NABs. However, only limited information is available on the molar mass of different substances in NABs. This study investigated the role of weight average molar mass ( Mw) and size of NABs fractions and their relation to sensory perception. Industrialized bottom-fermented NABs (n = 28) from the German market and NABs produced by different methods were used in this study. A trained sensory panel evaluated palate fullness intensity, mouthfeel, and basic taste descriptors (as additional quality parameters). Asymmetric flow field-flow fractionation was used to fractionate NABs, while Mw was determined by multi-angle light scattering and differential refractive index detectors. The NABs were fractionated into three groups containing different substances: proteins, proteins-polyphenol complexes (P-PC) and low molar mass (non-)starch polysaccharides (LN-SP), and high molar mass (non-)starch polysaccharides (HN-SP). The Mw range of proteins was 18.3–41 kDa, P-PC and LN-SP 43–122.6 kDa, and HN-SP 0.40–2.18·103 kDa. Harmony, defined as the sweet and sour ratio, influenced the palate fullness intensity perception. In the harmonic samples (sour/sweet sensory balanced), the size of HN-SP (> 25 nm) showed a positive correlation to palate fullness intensity. The results suggest the importance of dextrins, arabinoxylan, and β-glucan in modulating the sensory characteristics of harmonic bottom-fermented NABs.

13. August 2025

Fabian Lauck

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