Inactivation of Microorganisms and Enzymes in Foxtail Millet Yakju by High Hydrostatic Pressure Treatment

High hydrostatic Pressure was applied to Foxtail Millet Yakju to investigate the effects of high pressure on inactivation of microorganisms and enzymes. Total bacteria, lactic acid bacteria and yeast in untreated Yakju were $1.5{\times}$10$^4$,1.9${\times}$10$^4$ and 1.4${\times}$10$^4$ CFU/mL, respectively. Total bacterial count was reduced to 4.1${\times}$l0$^2$ CFU/mL, while lactic acid bacteria and yeast were sterilized completely in Yakju heated at $65^{\circ}C$ for 15 min. Lactic acid bacteria and yeast decreased greatly with the increase of treatment pressure, and were sterilized completely in Yakju treated at more than 300 ㎫ for 10 min/$25^{\circ}C$. Total bacteria were not completely sterilized with pressurization of even 600 ㎫ at room temperature and reduced to 2 log cycle even at $65^{\circ}C$. Total bacteria decreased by 2∼3 log cycle with the increase of treatment time from 10 to 60 min at $25^{\circ}C$/300 ㎫. Pressurization of Yakju caused a partial inactivation of $\alpha$ -amylase and glucosamylase, and the activities of $\alpha$ -amylase and glucoamylase decreased by 18.1% and 21.1%, respectively at $25^{\circ}C$/600 ㎫/10 min. Activities of $\alpha$ -amylase and glucoamylase decreased with the increase of temperature, and 22.2% and 32.1% of the original activity were remained with the treatment at $65^{\circ}C$/300 ㎫/10 min, respectively. Enzyme activities decreased slightly with the increase of treatment time at $65^{\circ}C$/300 ㎫.

초고압 처리에 의한 좁쌀약주의 미생물 살균 및 효소 불활성화

좁쌀약주를 초고압으로 처리하여 미생물 살균 및 효소불활성화 효과를 측정하였다. 무처리 좁쌀약주의 세균수는 $1.5{\times}$$10^4$ CFU/mL, 젖산균수는 1.9${\times}$$10^4$ CFU/mL, 효모수는 1.4${\times}$$10^4$ CFU/mL이었다. 좁쌀약주를 상압에서 열처리($65^{\circ}C$/15분)하였을 때 젖산균과 효모는 완전히 사멸되었으나 세균은 4.1${\times}$l0$^2$ CFU/mL이 잔존하였다 좁쌀약주를 초고압으로 처리한 결과 젖산균수와 효모수는 처리압력의 증가에 따라 급격히 감소하였으며 300 ㎫이상에서는 완전히 사멸되었다. 세균은 상온에서 압력을 600 ㎫로 높여도 멸균되지 않았으며, 300 ㎫/10분에서 처리온도를 $65^{\circ}C$까지 증가시켜도 2 log cycle밖에 감소되지 않았으며, $65^{\circ}C$/300 ㎫에서 처리시간을 50분까지 증가시켰을 때 2∼3 log cycle이 감소되었다 좁쌀약주를 초고압으로 처리하였을 때 $\alpha$-amylase와 glucoamylase의 활성은 처리 압력의 증가에 따라 다소 감소하여 상온/600 ㎫10분에서 각각 18.1%와 21.1%가 불활성화되었다. 300 ㎫/10분에서 처리온도의 증가에 따라 $\alpha$-amylase와 glucoamylase 모두 활성이 감소하였는데, $65^{\circ}C$에서 $\alpha$-amylase는 22.2%, glucoamylase는 32.1%만이 잔존하였다. 효소활성은 $65^{\circ}C$/300 ㎫에서 처리시간의 증가에 따라 다소 감소하는 경향을 보였다.