低溫保存 Preservation by Low Temperature

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1 低溫保存 Preservation by Low Temperature
第三部份：食品保存與微生物 低溫保存 Preservation by Low Temperature 黃顯宗 東吳大學 M202

2 冷凍冷藏在台灣的重要性 農業生產，季節性，以高麗菜生產為例 都市化 生活形態改變，以冷凍水餃為例

3 桂冠，金吉利

4 教學目標 認識低溫保存（冷藏與冷凍）的重要性 認識低溫保存的考慮因素 認識低溫保存對微生物的影響

5 基本原理 抑制生鮮食品的代謝速率 抑制微生物的生長 延長Shelf-life 低溫保存
冷藏 Refrigerating （cold）storage 冷凍 Frozen storage

6 冷藏考慮的因素 Temperature Relative Humidity Ventilation 空氣流通
Composition of Atmosphere Stored for longer time Higher relative humidity Higher storage temperature Irradiation

7 不同食品需要不同溫度與濕度

8 問題 甚麼蔬果適合冷凍？

9 Forzen Storage 考慮的因素 食物的選擇 前處理：殺菁 blanching Inactivate enzyme
Reduction of microorganisms Enhancement of green color Wilting of leaf Displacement of entrapped air

10 冷凍過程 Slow freezing Quick freezing Jay, 2000

11 冷凍期間 脫水：freezer burn Oxidation 溫度變化

12 解凍 Thawing 解凍方法 注意事項 Drip (bleeding) from meat
Leakage from fruit / vegetable Growth of microorganisms

13 冷凍食品的分類 Frozen raw foods Half-fixed foods Ready-to-eat foods

14 微生物依照不同適應溫度劃分 Ayres et al., 1980

15 食品微生物最低生長溫度

16 食品微生物最低生長溫度 Jay, 2000

17 食品中毒菌最低生長溫度 Frazier and Westhoff, 1988

18 低溫對微生物生長的影響 Frazier and Westhoff, 1988

19 低溫下菌相的改變 Frazier and Westhoff, 1988

20 Effect of Low Temp. on Microorganisms
微生物不同反應 Cocci耐冷，G+ rods次之 G- rods最差 Lethal Effects Sublethal Effects Cryoinjury 如何計數冷傷後的菌數？

21 微生物對低溫的反應 微生物與其狀態 Freezing rate Freezing temperature
Time of forzen Storage Kind of food Influence of defrost 儲存期中溫度的變化

22 Cold shock proteins Cold shock proteins (Csps) comprise a family of small proteins that are structurally highly conserved and bind to single-stranded nucleic acids via their nucleic acid binding motifs RNP1 and RNP2. Bacterial Csps are mainly induced after a rapid temperature downshift to regulate the adaptation to cold stress, but are also present under normal conditions to regulate other biological functions. The structural unit characteristic for Csps occurs also as a cold shock domain (CSD) in other proteins and can be found in wide variety of organisms from bacteria to vertebrates CspA, the major cold-shock protein of Escherichia coli

23 討論 香蕉是否可以放到冰箱冷藏？