Physicochemical and morphological changes in corn grains and starch during the malting for Palomero and Puma varieties

Abstract

Background and objective: Although corn is the most consumed and studied cereal in Mexico as food, its potential in fermented beverage production is less considered. The objective was to study the morphological and physiochemical changes during malting for Palomero and Puma corns, and to compare them with malted barley to determine the potentials of this cereal in the beer industry. Findings: The SEM images of the malted starches showed a selective enzymatic attack and germination rate and reducing sugars behaved as S-shape (logistic curve). The X-ray diffraction patterns showed that the process did not modify the crystalline structure of these starches. The pasting profile showed changes in the peak viscosity and final viscosity, associated with amylose degradation, debranching of amylopectin, and the increase in reducing sugars. The IR analysis showed that during the malting time, the lipids had a drastic change. Conclusions: Significant changes were found in the nutrimental composition after malting such as loss in fat and carbohydrates, while no significant differences were found in protein and ashes. The SEM images of the malting showed a selective enzymatic attack, and X-ray diffraction patterns showed that process does not modify the crystalline structure of this starch. Changes in the pasting profile indicate that the malting decreases the peak and final viscosity. Significance and novelty: The X-ray results clearly showed that the enzymatic attack takes place on the amorphous component of the starch, while in the case of corn the crystalline A-type orthorhombic structure does not suffer any change. These results indicate that corn malt can be suitable for brewing purposes.