Studies of the Variation of the Stored Lactobacillus casei CCRC 14023 Treated with Different Protective agents and Drying Methods

• Main Authors: Chia-Chun Su, 蘇家俊
• Other Authors: V. An-Erl King, Ph. D.
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/63934921705655542302

碩士 === 國立中興大學 === 食品科學系 === 89 === Lactobacillus casei was applied in the dairy industry extensively because of the special flavor produced with the process of its fermentation. According to the convenience of industrial application, dehydration is a popular way to preserve bacteria cells. Due to the survival of cells changed with factors which cause damage to cells based on the dehydration and storage conditions, protective agents were added to decrease the damage of cells during dehydration and storage. In addition, the effects of protective agents and their concentrations were varied with different species of bacteria. Therefore, the purpose of this study was to compare the effect of different concentrations of various protective agents, storage temperatures and processing treatments on the survival of L. casei and its storage stability during storage, and try to find out their protective effects by the sensitivity of dried cells to sodium chloride and oxgall and the change of β-galactosidase activity in dried cells. Results showed that the survival of cells was lower at higher storage temperature (25℃) and the best concentration of those tested protective agents were all at 10% instead of 15%. At low storage temperature (-40℃), there was no significant difference among the survival of dried cells with three kinds of protective agents. There was significant difference between the survival of dried cells with 10% nonfat dry milk solids (NFDMS) at higher storage temperature (4℃) and that at lower storage temperature (-40℃) during storage, but there was a significant decrease in the survival of dried cells with maltodextrin (MD) and trehalose at higher storage temperature (4℃) compared to that at lower storage temperature (-40℃). It was found that the damage on cytomembrane was more seriously than that on cell wall caused by drying, and the damage from vacuum-drying was more seriously than that from freeze-drying based on the sensitivity of dried cells to sodium chloride and oxgall. Although the protection of NFDMS was worse than MD and trehalose to dried cells’ cytomembrane during storage at low storage temperature (-40℃), there was no significant difference among the survival of dried cells with three kinds of protective agents. Therefore, it was suggested that the protection of NFDMS to dried L. casei’s cytomembrane was not good during storage. Although it could be found that the difference of damage to cytomembrane among different drying treatments caused by the change of β-galactosidase activity, it was not a good indicator to compare the protection effect among different protective agents. Keywords: Lactobacillus casei, β-galactosidase, freeze-drying, vacuum-drying, nonfat dry milk solids, maltodextrin, trehalose, storage