Qualitative and quantitative prediction of volatile compounds from initial amino acid profiles in Korean rice wine (makgeolli) model

In Korean rice wine (makgeolli) model, we tried to develop a prediction model capable of eliciting a quantitative relationship between initial amino acids in makgeolli mash and major aromatic compounds, such as fusel alcohols, their acetate esters, and ethyl esters of fatty acids, in makgeolli brewed. Mass-spectrometry-based electronic nose (MS-EN) was used to qualitatively discriminate between makgeollis made from makgeolli mashes with different amino acid compositions. Following this measurement, headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry (GC-MS) combined with partial least-squares regression (PLSR) method was employed to quantitatively correlate amino acid composition of makgeolli mash with major aromatic compounds evolved during makgeolli fermentation. In qualitative prediction with MS-EN analysis, the makgeollis were well discriminated according to the volatile compounds derived from amino acids of makgeolli mash. Twenty-seven ion fragments with mass-to-charge ratio (m/z) of 55 to 98 amu were responsible for the discrimination. In GC-MS combined with PLSR method, a quantitative approach between the initial amino acids of makgeolli mash and the fusel compounds of makgeolli demonstrated that coefficient of determination (R(2)) of most of the fusel compounds ranged from 0.77 to 0.94 in good correlation, except for 2-phenylethanol (R(2) = 0.21), whereas R(2) for ethyl esters of MCFAs including ethyl caproate, ethyl caprylate, and ethyl caprate was 0.17 to 0.40 in poor correlation.

PRACTICAL APPLICATION

The amino acids have been known to affect the aroma in alcoholic beverages. In this study, we demonstrated that an electronic nose qualitatively differentiated Korean rice wines (makgeollis) by their volatile compounds evolved from amino acids with rapidity and reproducibility and successively, a quantitative correlation with acceptable R2 between amino acids and fusel compounds could be established via HS-SPME GC-MS combined with partial least-squares regression. Our approach for predicting the quantities of volatile compounds in the finished product from initial condition of fermentation will give an insight to food researchers to modify and optimize the qualities of the corresponding products.

Evaluation of antioxidant capacity and aroma quality of anthograin liqueur

Moderate consumption of wine, beer, whisky or liqueur is known to be beneficial for improving health because of the radical scavenging action of antioxidants present in them. Thus, antioxidant and aroma properties of anthograin liqueur made from purple wheat grain were evaluated for the added-value processing purpose of that grain. Anthograin liqueur showed the highest 2,2-diphenyl-1-picryhydrazyl (DPPH) free radical scavenging activity, total phenolic content (TPC) and oxygen radical absorbance capacity (ORAC) in comparison with three control samples Canadian iceberg vodka (CIV), Hiram walker special old rye whisky (HWSORW) and Wiser's De Luxe Canadian whisky (WDLCW). Only anthograin liqueur contained anthocyanins and its total anthocyanin content (TAC) was 81mg/l. In lipid-soluble phase, TPC and ORAC were 241.1 and 998.6mg/l for anthograin liqueur, 40.0 and 93.6mg/ld for WDLCW, 23.1 and 63.6mg/l for HWSORW, and 1.1 and 12.4mg/l for CIV, respectively. In water-soluble phase, TPC and ORAC were 685.5 and 1467.7mg/l for anthograin liqueur, 29.0 and 96.0mg/l for WDLCW, 36.4 and 99.2mg/l for HWSORW, and 2.0 and 42.8mg/l for CIV, respectively. Eight types of phenolic acids in anthograin liqueur, four types of phenolic acids in WDLCW and three types of phenolic acids in HWSORW were found and no phenolic acid was detectable in CIV. Total phenolic acids in anthograin liqueur, WDLCW and HWSORW were 28.8, 10.3 and 5.7mg/l, respectively. Similarity in aroma quality was found between anthograin liqueur and CIV by using the electronic nose. Purple wheat grain may have potential as a novel material for liqueur brewing.