- 學位論文
探討Pantoea spp.對截切香瓜品質影響
Effect of Pantoea spp. on the quality of fresh-cut melons
摘要
近年來因消費者追求方便性及健康的飲食，截切蔬果類產業成長迅速，但產業常因截切處理場域之衛生條件及微生物之汙染，導致保存期限縮短，其中網紋香瓜為常見之高價格截切水果，且具有較高的pH值及水活性使微生物容易於其中生長，導致生產者經濟上的損失及消費者健康上的疑慮，因此本研究目的為 (1) 分析香瓜中成分之變化，作為評估截切香瓜儲藏過程中品質變化之指標。(2) 鑑定於截切香瓜可能造成腐敗相關之微生物，並針對菌株進行特性分析。以網紋香瓜作為實驗樣品進行5℃、15℃、25℃及35℃之儲藏性試驗，並從品質指標中發現當截切香瓜儲藏於較高溫度下，其蔗糖、葡萄糖、果糖、檸檬酸及蘋果酸之含量下降較多，反之儲藏在低溫時，含量下降較少。從微生物實驗中發現Pantoea spp.及Enterobacter spp.為截切香瓜中主要存在之微生物，其中Pantoea spp.於5℃仍能生長 (世代時間為5.68 ± 1.60小時)，而Enterobacter spp.則明顯受到抑制 (14.11 ± 5.83小時)。另外，Pantoea spp.在5℃時具有較強的表面移行能力(移動距離由0.40 ± 0.69公分經7天儲藏至3.43 ± 0.63公分)，這項特性有助於菌株在食品上生長及生物膜的產生，進而影響香瓜品質指標。後續將分離出之Pantoea sp.接種回截切香瓜中進行5℃儲藏性試驗，以驗證菌株與截切香瓜腐敗之關係，當截切香瓜接種Pantoea sp.後儲藏至第216小時表面會佈滿黏液，於對照組並未觀察到此現象，且接菌對截切香瓜之葡萄糖及蘋果酸含量具有影響，而可滴定酸及D-乳酸含量變化為上升趨勢，並從接菌之截切香瓜中再次分離出Pantoea sp.。綜合上述，截切香瓜於儲藏過程中Pantoea spp.及Enterobacter spp.為主要存在之菌株，當Pantoea sp.於截切香瓜中大量存在時，會影響葡萄糖、蘋果酸、可滴定酸及D-乳酸之變化，提供作為評估Pantoea sp.對截切香瓜品質影響之參考依據。
並列摘要
In recent years, as consumers are persuing convenience and healthy diets, fresh-cut fruits and vegetables industry has grown rapidly, but the hygienic conditions and microbial contamination of the fresh-cut treatment field often shorten the shelf life. Among fresh-cut fruits, netted melon is a common high-priced fruit, and microorganisms can easily grow within fresh-cut melons due to their high pH value and water activity, which may cause economic losses to producers as well as public health issues. Therefore, the aims of this study are to (1) analyze the changes in the composition of the melon as an indicator to evaluate the quality changes of the fresh-cut melon during storage. (2) Identify the possible indicator bacteria that may cause spoilage in the fresh-cut melons and characterize the bacteria. Netted melon was used as the experimental sample to conduct the storage assay at 5℃, 15℃, 25℃ and 35℃. It was found that the contents of sucrose, glucose, fructose, citric acid and malic acid decrease more when fresh-cut melons stored at a high temperature compared to those when stored at a low temperature. From microbiological experiments, the results showed that Pantoea spp. and Enterobacter spp. are the main microorganisms in fresh-cut melons and Pantoea spp. can grow at 5℃ (doubling time is 5.68 ± 1.60 hr), while Enterobacter spp. were significantly inhibited. In addition, Pantoea spp. has a strong swarming motility on the 7th day at 5℃, the range of swarming from 0.40 ± 0.69 to 3.43 ± 0.63 cm which may help the bacteria grow on food and produce biofilm, and it has been found that the bacteria may affect the quality of fresh-cut melons. Subsequently, inoculation of the Pantoea sp. into to the fresh-cut melons was to verify the relationship between the bacterium and the quality of fresh-cut melons. It was found that the fresh-cut melons inoculated with Pantoea sp. were covered with slime on the surface at 216th hours. This phenomenon was not observed in the control group. On the other hand, the physicochemical analysis of the fresh-cut melons inoculated with the Pantoea sp. indicated that the inoculation has an effect on the contents of glucose and malic acid, while the contents of titratable acidity and D-lactic acid showed an upward trend. Besides, Pantoea sp. was reisolated from the fresh-cut melons which were inoculated with the strain, in order to comply with Koch's postulate. Based on the above findings, Pantoea spp. and Enterobacter spp. are important microorganisms that exit in fresh-cut melons during storage. When a large amount of Pantoea sp. exit in fresh-cut melons, it will affect the changes of glucose, malic acid, titratable acidity and D-lactic acid, and provide a reference basis for evaluating the effect of Pantoea sp. on the quality of fresh-cut melons.
參考文獻
延伸閱讀
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