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|標題:||The Application of Intermittent Far-Infrared Radiation Heating on the Freeze-Drying and Controlled Low-Temperature Vacuum Drying of Lactic Acid Bacteria: Ⅰ. Lactobacillus rhamnosus BCRC 10940|
間歇性遠紅外線加熱應用於乳酸菌控低溫真空乾燥及冷凍乾燥的探討Ⅰ. Lactobacillus rhamnosus BCRC 10940
Controlled low-temperature vacuum drying
|摘要:||Lactobacillus rhamnosus對於人體生理具有多項保健功效，但是在乾燥狀態下，菌株的存活率及貯存安定性並不佳，若能改善乾燥操作，縮短乾燥所需時間，而且同時具有良好的乾燥處理後之菌株活性及貯存安定性，則必定能夠更加具備競爭力。冷凍乾燥為一種普遍使用於菌種保存的方法，但是乾燥所需時間過長及能量消耗過大是其主要的缺點，而控低溫真空乾燥是將乾燥樣品保持在非凍結的低溫狀態下進行真空乾燥，樣品可以避免凍結之傷害，可得到類似於冷凍乾燥操作之高品質產品。遠紅外線輻射加熱具有傳熱效率高、裝置簡單、操作方便、成本低廉等優點。此外配合間歇性的遠紅外線輻射加熱方式，亦可藉以改善產品品質。本研究擬將遠紅外線輻射與間歇加熱應用於冷凍乾燥及控低溫真空乾燥操作，來對L. rhamnosus進行乾燥處理，並探討乾燥後之存活率、貯存安定性以及不同基質復水之比較。結果顯示，0℃預冷一個小時、-30℃冷凍一天以及-60℃冷凍一天對於L. rhamnosus存活率無顯著差異，但0℃預冷一個小時對於細胞膜之傷害最小。遠紅外線加熱與間歇條件可有效縮短乾燥所需的時間。乾燥後之存活率則以遠紅外線冷凍乾燥(-60℃凍結)最佳。在間歇加熱部份，以α=0.5之遠紅外線控低溫真空乾燥可有效提昇L. rhamnosus乾燥後之存活率，而對於遠紅外線冷凍乾燥(-30℃、-60℃凍結)則以α=0.25之間歇加熱可改善L. rhamnosus乾燥後的存活率。關於復水試驗，利用2% peptone進行復水可有效提昇遠紅外線控低溫真空乾燥樣品之存活率，而不同基質對於冷凍乾燥樣品則沒有顯著影響。在貯藏實驗方面，低溫貯藏下之菌株的存活率較高。乾燥之後L. rhamnosus以遠紅外線控低溫真空乾燥樣品具有較佳之產酸能力。總而言之，間歇性遠紅外線加熱(α=0.75、α=0.5、α=0.25)配合控低溫真空乾燥對於L. rhamnosus以2% peptone進行復水可得到類似冷凍乾燥之存活率，但其在5℃之貯藏安定性以及產酸能力則優於冷凍乾燥。膠體電泳分析結果發現不同的乾燥模組中並未發現新蛋白質的產生。掃描式電子顯微鏡觀察則發現受傷之L. rhamnosus會改變其大小、形狀。|
Freeze-drying (FD) is a popular method used in the culture preservation of microorganisms. However, it possesses the major defects of lengthy drying time and large amount of energy consumption. Lactobacillus rhamnosus has lots of important physiological functions beneficial to human health. However, low numbers of active L. rhamnosus cells were found in the dried products. Therefore, competitiveness could be enhanced by means of the improvement of the drying operation, such as reduction in drying time, enhancement of the viability and storage stability after drying. Controlled low-temperature vacuum drying (CLTVD) is a method to dry products as cold as possible without freezing. Freezing damage could be avoided and high quality products as those produced by freeze-drying might be manufactured. Far-infrared radiation (FIR) possesses many advantages, such as high thermal transmission, simple design, easy operation, and low cost, etc., and is frequently used in dehydration operation. Besides, intermittent heating is also often used in far-infrared heating in order to reduce drying time and improve product quality. The goals of this study are to combine FIR and CLTVD in order to reduce drying time and improve the viability and storage stability of dried L. rhamnosus. Results indicated that there were no significant difference in viabilities of L. rhamnosus among cooling at 0℃ for 1-hr, freezing at -30℃ for 1-day and freezing at -60℃ for 1-day, but cooling at 0℃ for 1-hr had much less damage for cell membrane. Treatment with FIR and different intermittences could reduce drying time. The highest survival of L. rhamnosus was obtained when treated with FD with far-infrared and frozen at -60℃. For intermittent heating, there was significant increase in viabilities of L. rhamnosus after CLTVD at intermittence α=0.5, and after freeze-drying frozen at -30℃, -60℃ at intermittence α=0.25. For rehydration test, the best rehydration medium to obtain the hightest viability after controlled low-temperature vacuum drying was 2% peptone, and there was no significant difference between rehydration media used after FD. During storage, cultures stored at lower temperatures possessed higher survival. The higher acidification activity was obtained by CLTVD compared to FD. In short, treatment with different intermittences (α=0.75, α=0.5, α=0.25) for CLTVD and rehydrated with 2% peptone could gain higher survival same as FD, but CLTVD had better acidification and storage stability at 5℃ compared to FD. In SDS-PAGE analysis, there was no new protein production after CLTVD and FD. Scanning electron microcopy examination indicated that the injury of L. rhamnosus would cause the variation in size and shape of the cells.
|Appears in Collections:||食品暨應用生物科技學系|
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