Effect of grinding size and inoculation rates on barley nuruk quality characteristics and volatile compounds of makgeolli

This study aimed to assess the quality characteristics of barley nuruk and makgeolli based on grinding size and inoculation rates, with a focus on identifying key aroma compounds contributing to nuruk off-flavors. Barley was hulled to 30%, using coarse (5 mm) and fine (1 mm) ratios, and inoculated with Aspergillus luchuensis 34-1 at 0.1% and 1% rates. Quality parameters such as moisture, pH, acidity, amino acidity, organic acids, and free amino acids were analyzed. At the same time, enzyme activities like saccharogenic power, α-glucosidase, glucoamylase, α-amylase, and carboxypeptidase were measured. Microbial contamination was assessed, and volatile aroma compounds were quantified using gas chromatography. Results indicated that finer milling (1 mm) and higher inoculation (1%) significantly increased enzyme activity and free amino acid content in nuruk, leading to a higher concentration of fruity volatile compounds in makgeolli. Thus, adjusting the grinding size and inoculation rates in nuruk production is key to enhancing makgeolli flavor quality.