Development of a process for producing ethyl caproate- and ethyl lactate-rich riceshochu

Abstract

To increase the popularity of rice shochu, a process was developed to produce ethyl caproate-and ethyl lactate-rich rice shochu. On a laboratory-scale, there was a shochu production trial with Saccharomyces cerevisiae Y-E. Caproic acid added in the secondstage fermentation was esterified to ethyl caproate. Both ethyl caproate and ethyl lactate were produced by adding a caproic acid-producing bacterial (CAPB) consortium and lactic acid bacterium (LAB) to the shochu production process. Yellow koji was more appropriate for producing a flavour-rich shochu with the addition of a CAPB consortium and LAB than white koji. Optimal addition time for the CAPB consortium and LAB was on the first day of the second-stage fermentation, judging from concentrations of ethyl caproate and ethyl lactate produced. Additional dosages of CAPB consortium and LAB positively affected the formation of ethyl caproate and ethyl lactate, respectively. Shochu production with the addition of 2% and 4% CAPB consortium led to ethyl caproate concentrations of 27.3 mg/L and 47.9 mg/L in genshu, respectively, and the shochu achieved the best sensory test score from the Japanese shochu brewery panellists.

Behaviour of ethyl caproate during the production and distillation of ethyl caproate-rich riceshochu

“…In our previous study, the changes in ethanol and ethyl caproate concentrations during shochu production with addition of caproic acid or the cultured broth of CAPB consortium on the first day of the second‐stage fermentation were reported . The flavour compounds and their concentrations in genshu (containing 300–315 g/L ethanol) after vacuum distillation were also reported . According to eqn , the distillation efficiency of each flavour compound, E , was calculated.…”

“…As described in our previous study on producing ethyl caproate‐rich and ethyl lactate‐rich rice shochu , Saccharomyces cerevisiae Y‐E, Aspergillus oryzae and CAPB consortium were used for shochu production. The CAPB consortium was obtained from the pit mud at a Chinese liquor distillery and maintained by subculturing.…”

“…The obtained filtrate was adjusted to 10°Brix (AR200; Reichert Inc., NY, USA) and sterilized before use. The CAPB consortium was subcultured using sterilized basal liquid medium consisting of yeast extract (10 g/L), sodium acetate (20 g/L), K 2 HPO 4 (0.4 g/L), MgSO 4 ·7H 2 O (0.2 g/L), (NH 4 ) 2 SO 4 (0.5 g/L), CaCO 3 (5 g/L, separately sterilized and added) and ethanol (20 g/L, separately added at a clean bench after sterilization) .…”

“…The supernatant was filtered through a 0.45 μm membrane filter (SYT0116, Jinteng, China) before analysis. The concentrations of ethanol and flavour compounds were measured using gas chromatography (GC353B; GL Sciences, Tokyo, Japan), as previously described . Yeast numbers were counted using a hemocytometer.…”

“…In our previous study, a process was developed to produce rice shochu rich in both ethyl caproate and isoamyl acetate . Ethyl caproate was produced by adding cultured broth of the caproic acid‐producing bacterial (CAPB) consortium isolated from the Chinese liquor pit mud to shochu mash on the first day of the second stage of fermentation, and its concentration increased with the amount of CAPB consortium broth.…”