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標題: | 豆漿與豆腐之微生物分離及其特性分析 Characterization of Microorganisms Isolated from Soymilk and Tofu |
作者: | Tzu-Yun Chien 簡子芸 |
指導教授: | 羅翊禎 |
關鍵字: | 豆漿與豆腐,Rhodococcus,生長預測模式,Paenibacillus,Bacillus, soymilk and tofu,Rhodococcus,predictive growth model,Paenibacillus,Bacillus, |
出版年 : | 2019 |
學位: | 碩士 |
摘要: | 豆漿與豆腐是高水活性、低酸性且高蛋白質含量的黃豆食品,微生物容易在其中快速生長而造成腐敗或食品中毒,故殺菌條件與儲藏環境將影響產品之品質及其保存期限。本研究目的為分離並鑑定豆漿與豆腐中常見的微生物,作為製程中微生物控制、保存期限評估及品管檢驗的參考。以市售經超高溫瞬間殺菌之豆漿與商業殺菌之豆腐為樣品進行5 ℃、15 ℃、25 ℃與35 ℃儲藏試驗,結果顯示豆漿中微生物為隨機出現,而出現頻率最高者為Rhodococcus,而豆腐的微生物在儲藏過程有明顯生長,其中以Bacillus與Paenibacillus最廣泛存在且為腐敗時的優勢菌。針對上述分離之微生物進行特性分析,發現Rhodococcus、Bacillus與Paenibacillus皆可在中性食品中生長良好,高於冷藏溫度時Rhodococcus會在豆漿中生長,但其沒有致病性基因與抗生素抗性,且在低溫儲藏下會逐漸死亡。另一方面,高於冷藏溫度時Bacillus會在豆腐中快速生長,其可能在腸道中產生腸毒素且對抗生素具有抗性。然而Paenibacillus在低溫下可生長,雖然不具有致病性與抗生素抗性,仍會造成豆腐的腐敗。此外,Rhodococcus不耐巴氏德殺菌,因此推測其為殺菌後的汙染,但Bacillus與Paenibacillus在加熱後皆可存活,故其可能為殺菌前就存在原料中或在加工設備中殘留而反覆汙染。將Rhodococcus接種回豆漿與培養基中建立其生長預測模式,發現在15 ℃至35 ℃之間其生長速度隨溫度上升而愈來愈快,且豆漿為適合其生長的基質。另一方面,以16S rDNA微生物體分析豆腐在15 ℃腐敗過程的菌相變化,確認其優勢菌為Bacillus與Paenibacillus,以real-time qPCR偵測豆腐中的Paenibacillus,雖專一性與敏感度尚有改善空間,仍是一有潛力的快速檢驗方法。應用real-time qPCR配合傳統培養法檢測冷藏下腐敗的其他市售豆腐,發現Paenibacillus可能是存在於許多冷藏豆腐中,其來源與檢驗值得注意與探討。 Microorganisms in soymilk and tofu can grow fast and cause spoilage or foodborne disease because of their high water activity, low acidity and high protein content. Therefore, the condition of sterilization and storage can affect the quality and shelf-life of products. The aim of this study was to isolate, identify and characterize the common microorganisms in commercial soymilk and tofu to provide reference for microbial control during process, shelf-life evaluation and quality control test. Commercial ultra-high temperature (UHT) soymilk and tofu with commercial sterilization were conducted storage assay including 5 ℃, 15 ℃, 25 ℃ and 35℃, and the results showed occurrence of microorganisms in soymilk were random and Rhodococcus were the most often found microorganism in storage assay. On the other hand, the bacterial concentration in tofu increased during storage period, furthermore, Bacillus and Paenibacillus were the dominant genera while spoilage and widely present in tofu. The isolates from soymilk and tofu were characterized and found Rhodococcus, Bacillus and Paenibacillus could grow well in neutral environment. Although Rhodococcus could grow at room temperature, they gradually died under refrigeration and without virulence gene or antibiotic resistance. Bacillus could grow fast when the temperature higher than refrigeration and may be able to produce enterotoxin in gastrointestinal tract and have resistance to antibiotic. However, Paenibacillus could grow under low temperature and result in tofu spoilage although they didn’t have toxin gene and antibiotic resistance. In addition, Rhodococcus couldn’t survive after pasteurization consequently assuming they contaminated after UHT process. Bacillus and Paenibacillus could survive after pasteurization and had potential to form biofilm. Hence, they may exist in materials and survived after commercial sterilization or on the food-contact surface during process and cause wide contamination. Rhodococcus were inoculated to soymilk to develop predictive growth model. The results showed Rhodococcus could grow faster as temperature rose between 15 ℃ and 35 ℃ and soymilk is a suitable substrate for Rhodococcus. The microbiota succession of tofu during storage at 15 ℃ were analyzed to reconfirm Bacillus and Paenibacillus were the dominant genera in tofu. Because of the importance of Paenibacillus in tofu, a potential rapid detection method using real-time qPCR was developed though the specificity and sensitivity were still need to be improved. Tofu from other manufacturers were examined by real-time qPCR and traditional method and found Paenibacillus may present in many refrigerated tofu. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/7243 |
DOI: | 10.6342/NTU201902674 |
全文授權: | 同意授權(全球公開) |
電子全文公開日期: | 2029-08-06 |
顯示於系所單位: | 食品科技研究所 |
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ntu-108-1.pdf 此日期後於網路公開 2029-08-06 | 5.79 MB | Adobe PDF |
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