Effect of Carbon Source Supplement on the Gel Production from Citrus Juice by Gluconacetobacter hansenii TL-2C

This study was conducted to determine the minimum concentration of citrus juice for basal medium and also to search for an additional carbon source for the best production of the gel. A concentrate of citrus fruit juice of 65$^{\circ}$Brix, it was diluted to be used as a basal medium. Static cultivation of Gluconacetobacter hansenii TL-2C for 14 days at 3$0^{\circ}C$ produced the best gel with 7.5$\pm$0.4 mm thickness in the 6-fold diluted citrus Juice concentrate without any additional nutrient. However, the same thickness could be obtained with 60 to 100-fold diluted juice concentrate when refined white sugar was added at appropriate concentrations. Glucose was the most effective sugar for the both of gel and acid production, and optimal concentration of the sugar was 10$^{\circ}$Brix. Ethyl alcohol at 1.0% had synergistic effects in combination with refined sugar and increased the gel thickness up to 15.1 mm which was 1.85 times thicker than that of refined sugar alone. However, acetic acid was not effective. Gel productivity with supplement of ethanol was 172.6$\pm$8.4 g wet/L, and it was approximately equal to 4.7 g of dry gel/L.

Gluconacetobacter hansnii TL-2C에 의한 감귤과즙 발효시 겔 생성에 미치는 탄소원의 영향

Gluconacetobaacter hansenii TL-2C를 사용하여 3$0^{\circ}C$에서 14일간 정치발효하면서 감귤과즙 희석배율 및 탄소원의 종류와 농도가 겔 생성에 미치는 영향을 검토하였다. 감귤과즙으로는 제주개발공사에서 제조한 당도 65$^{\circ}$Brix의 서귀포산 온주밀감 농축액을 사용하였다. 농축과즙만으로 발효한 경우에는 과즙 6배 희석액에서 가장 두꺼운 7.5$\pm$0.44 mm의 겔이 생성되었으며, 정백당을 $10^{\circ}$Brix로 보당한 경우에는 100∼120배 희석액이 가장 적합하였다. 농축과즙 100배 희석액을 사용하여 당의 종류를 달리한 경우에는 glucose $10^{\circ}$Brix에서 가장 두꺼운 7.5$\pm$0.61 mm의 겔이 생성되었다. 정백당 $10^{\circ}$Brix를 함유한 과즙 희석액에 1.0%의 주정을 첨가한 경우에는 겔의 두께가 평균 15.1mm로 대조구에 비하여 약 1.85배로 증가되었으나 acetic acid 첨가는 효과가 없었다. 1.0%의 주정을 첨가하고 발효한 경우의 겔 수율은 평균 172g wet/L(4.7 g dry/L)로 확인되었다.