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  • 學位論文

評估截切木瓜微生物與化學指標之變化

Evaluation of microbiological and chemical parameters in fresh-cut papaya

指導教授 : 羅翊禎
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摘要


木瓜是熱帶更年性水果,為台灣主要的經濟農作物之一。由於木瓜是高水活性與低酸性的水果,組織經輕度加工後會被破壞,且會促進乙烯產生,加速水果之老化與熟成。不適當的加工與儲藏環境也將促使微生物容易在其中快速生長而造成食品腐敗進而影響產品品質。本研究動機為分離並鑑定截切木瓜中常見之微生物和分析各項物理與化學指標,並評估截切木瓜在儲藏期間之品質變化。以市售截切木瓜為樣品進行三批次的儲藏性試驗,一般儲藏 (5 ℃) 與加速儲藏 (15 ℃、25 ℃和35 ℃) 試驗,並分離與鑑定常見微生物,以及結果顯示所分離的菌株主要爲腸桿菌科 (Enterobacteriaceae) 菌種,且在低溫培養下分離出假單胞菌屬 (Pseudomonas spp.)。針對上述分離之微生物進行特性分析,發現腸桿菌科菌種與假單胞菌屬皆可在中性環境中生長良好。此外,在高於冷藏溫度時腸桿菌科菌種於截切木瓜中快速生長,低於7°C下則無法生長。然而Pseudomonas在低溫下,5°C可生長,且其可能在腸道中產生腸毒素且對抗生素具有抗性。由於從市售截切木瓜發現腸桿菌科菌種廣泛存在於樣品中,因此也進行自行截切木瓜之儲藏實驗。結果顯示自行截切木瓜所分離之菌種多數為腸桿菌科,推測腸桿菌科菌種為木瓜本身的原生菌群且在大自然環境中普遍存在。同時也利用自行截切木瓜接種Pseudomonas 菌株,藉由截切木瓜失重、顔色、總酚含量等指標改變,以了解菌株對截切木瓜品質之影響。另外,本研究也使用不同處理方式,如酒精處理之木瓜與不同包裝材質,探討微生物與物化學指標對於截切木瓜之影響。綜上所述,本研究希望能夠提供截切木瓜於製程中微生物控制,品管檢驗與評估保存期限之參考。

並列摘要


Papaya is known to be one of the most profitable climacteric crops in Taiwan. The market sales of fresh-cut papaya have rapidly grown in recent years as a result of consumer demand. However, the minimal processing steps such as peeling or cutting will promote the production of ethylene which accelerates tissue senescence of fruits. Besides, microbial contamination is inevitable for minimally processed fresh-cut fruits. Its high water activity and low pH favours microbial growth, leads to early spoilage of the fresh-cut papaya. Inappropriate processing and storage condition is favourable for microbial growth, fresh-cut papaya will spoil faster and shelf-life will be reduced. Hence, microbial growth and physicochemical changes will affect both the quality and shelf-life of the fruit products. Therefore, the objective of this study is to evaluate the quality changes of fresh-cut papaya in the storage test by identifying and characterizing the common microorganisms in fresh-cut papaya as well as physical and chemical parameters analysis. 3 batches of storage assay on commercial fresh-cut papaya were conducted at 5°C, 15°C, 25°C and, 35°C. The results showed that most of the isolated bacteria were mainly belonging to the family Enterobacteriaceae. While Pseudomonas spp. were isolated during storage at low temperatures. Besides, we found that the isolated strains belonging to Enterobacteriaceae and Pseudomonas grew well in a neutral environment. Different species of the family Enterobacteriaceae grew faster when the temperature is higher than the refrigeration temperature, and cannot grow below 7°C. However, Pseudomonas can grow at a low temperature of 5°C, it was resistant to certain antibiotics and might be able to produce enterotoxins in the intestines. Since the species in the family Enterobacteriaceae found widely in the samples from the commercially fresh-cut papaya. Hence, the storage assay of self-cut papaya was also carried out. The results showed that most of the strains isolated from self-cut papaya belong to the family Enterobacteriaceae. It was possible to speculate that the strains of Enterobacteriaceae were the native microflora residing in fresh-cut papaya as well as widely existed in natural environments. Nevertheless, the Influence of Pseudomonas sp. towards the quality of fresh-cut papaya was studied by analyzing weight loss, color, total phenol content, and other indicators on the fresh-cut papaya. Also, the effects of microbiological and chemical parameters on self-cut papaya were studied by developing different treatments, such as the applicability of alcohol-treated papaya and different packaging materials on ready-to-eat papaya. Lastly, the findings in this study hope to provide the benchmark information and further insights for microbial control, quality control measures, and evaluation of the shelf life of cut papaya in the manufacturing process.

參考文獻


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