ABSTRACT:The objective of this study was to compare the effects of adding lactic acid and pectinase, and chaptalization for the quality of apple wine and the production of hazardous compounds (methanol and acetaldehyde). The pH of all of the samples was below 4; therefore, mash seemed to be fermented without any issue. Total acidity was the highest in sample A due to lactic acid addition. Pre-treated groups (samples B, C, and D) showed higher total acidities than that of the control (P＜0.05). Pre-treatments might influence the production of organic acids in apple wines. The control and pectinase added sample (sample B) had the lowest alcohol contents. Adding lactic acid produced more alcohol, and chaptalized samples produced more alcohol due to the addition of sugar. Adding pectinase with and without chaptalization was not effective for producing more alcohol. The control sample had significantly higher acetaldehyde content (2.39 mg/L) than the other samples (1.00∼2.07 mg/L); therefore, pre-treatments for apple wine fermentation produced a lower amount of acetaldehyde. Among the pre-treated samples, samples C and D showed the lowest acetaldehyde content of 1.00 mg/L and 1.16 mg/L, respectively. On the other hand, a significantly higher amount of methanol was generated for sample A (1.03 mg/L) and sample D (1.22 mg/L) than that of the control (0.82 mg/L) (P＜0.05). Adding lactic acid or chaptalization was effective in reducing methanol and acetaldehyde in apple wines.

The objective of this study was to investigate the influence of yeast strains on the physicochemical characteristics, methanol and acetaldehyde profiles, and volatile compounds of Korean rice distilled spirits. Ten yeast strains were employed for the brewing of distilled spirits and the resulting products were filtered and distilled twice. The amounts of methanol and acetaldehyde for the ten yeasts showed different profiles. Higher amounts of methanol were detected for strains CL, CY, DV, BD, ED and LP, while EC, D2, D4 and RH had <2 mg L À1 methanol content. Strains D2, BD and ED produced the lowest amounts of acetaldehyde. The head portions of the spirits, which started in the fraction that contained <5 mg L À1 of acetaldehyde, were between 7.7% (BD) and 18.2% (LP) of the total fractions. Strains D2, CL and CY produced more alcohol in the body fraction than the other yeasts. The major volatile compounds were esters in the form of fatty acid ethyl esters, such as ethyl palmitate, ethyl myristate and ethyl oleate. Isoamyl alcohol, which is an important volatile compound for rice wine, occupied 0.91-2.24% of the relative peak areas. Strain D2, of the strains tested, appeared to be the most appropriate yeast for Korean distilled spirit based on alcohol production and the high relative peak area of volatile compounds, except for ethanol. Strains CL and CY could also be considered for producing high-quality Korean rice distilled spirits with efficiency and flavour.

We investigated the brewing and fermenting characteristics of makgeolli produced from high-yielding rice varieties. We used the high-yielding indica rice varieties, Anda and Dasan 1, and the japonica varieties, Deuraechan and Boramchan. Our results showed that the rice protein level was the highest in makgeolli produced from Anda (7.5±0.2%), while the amylose level was the lowest in makgeolli produced from the mid-to late-maturing japonica varieties (Deuraechan, 18.9±0.7%; Boramchan, 18.9±1.4%). Samples of makgeolli produced from Anda, Deuraechan, and Boramchan by using the Ipguk (Koji) method had an alcohol content of 16.6-17.4% on completion of fermentation. By contrast, makgeolli produced from Dasan 1 had an alcohol content of 14.3%; further, the makgeolli differed significantly in the sensory test and was scored as excellent regarding comprehensive preference. For makgeolli produced by using the uncooked rice fermentation method, samples produced from the indica varieties, Anda and Dasan 1, had lower alcohol contents (17.2% and 17.0%, respectively) and higher total acidity levels (0.33% and 0.31%, respectively) than did samples produced from the japonica varieties, Deuraechan and Boramchan (0.28% for both). In the sensory test, samples produced from Anda and Dasan 1 performed significantly better regarding scent, swallowing, and comprehensive preference.

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