Unmalted Rice, Wheat, and Sorghum Modulate Antioxidant Capacity, Nitrogen Metabolism, Alcohol Profile, and Sensory Quality of Craft Ale Beer

The use of unmalted cereal adjuncts represents a strategy to diversify craft beer and modify its functional properties. This study evaluated the effects of partially replacing barley malt with unmalted rice, wheat, and sorghum (20% and 40%) on the chemical composition, antioxidant capacity, free amino acid profile, alcohol profile, and sensory characteristics of Ale beer. Kolbach index (KI), international bitterness units (IBU), total phenolic content (TPC), antioxidant capacity (ORAC and ABTS), free amino acids, ethanol and higher alcohols, and sensory attributes were determined, and principal component analysis (PCA) was performed to explore the relationships among the evaluated variables. Cereal type, substitution level, and their interaction significantly affected most variables, indicating that the effect of increasing the substitution level depended on the cereal. All adjunct formulations produced less ethanol than the control (8.758%, v v−1), with the lowest value at 40% rice (4.561%); isoamyl alcohol was lower in all adjunct beers, whereas isobutanol did not differ significantly among formulations. The 40% sorghum formulation (T6) showed the highest TPC (316.66 μg gallic acid equivalents (GAE) 100 mL−1) and ORAC (oxygen radical absorbance capacity; 11.59 mmol trolox equivalents (TE) L−1), and, together with 20% sorghum (T5), the highest ABTS (2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)) values (up to 7.64 mmol TE L−1). In contrast, 40% rice markedly reduced TPC and antioxidant capacity, whereas the wheat formulations showed values similar to or lower than the control. The residual free amino acid profile (L-serine, arginine, cysteine, aspartic acid, threonine, and alanine, among others) also differed among formulations; because wort amino acids were not measured, these differences cannot be attributed specifically to amino acid release during mashing or to yeast assimilation. PCA explained 63.5% of the total variance and separated the beer formulations according to cereal type and substitution level. Among the formulations evaluated, 40% unmalted sorghum showed the highest antioxidant capacity while its overall acceptability did not differ from that of the control, although its ethanol content was lower than that of the control.