Emerging approaches to improve barley malt processing and quality: Ultrasound-assisted hydration and ethanol pre-treatment to drying

Abstract

This work aimed to evaluate how two emerging technologies impact the malting process and the quality of barley malt: ultrasound-assisted hydration and ethanol pre-treatment to drying. All three steps of malting (hydration, germination, and drying), as well as the resulting malt's quality indicators, were evaluated. Conventional and ultrasound-assisted (25 kHz; 91 W/L, 20 °C) hydration were carried out, followed by germination, ethanol (99.5%) pre-treatment (immersion 30 min, 25 °C), and convective drying (50 °C, 1 m/s). Texture analysis demonstrated that the different stages of the malting process modify the structure and composition by increasing or decreasing the compression force in the grain. The ultrasound-assisted hydration improved the second hydration stage, where hydration resistances were greater, reducing hydration time by 38%; moreover, ultrasound accelerated the germination step with root growth 1.17 times greater. During drying, ultrasound-assisted hydration followed by ethanol pre-treatment, reduced drying time by 38.5% (barley) and 17.8% (malt). Both evaluated technologies, therefore, intensify the malting process. In addition, it was demonstrated that their use increased the alpha (9%) and beta-amylase (7%) activity in malt and modified paste and gel-forming properties of barley and malt flours. Therefore, these results suggest that the use of ultrasound improved hydration and germination processes, and ethanol pre-treatment accelerated the drying process because of improved mass transfer, both without negative impact on malt quality.