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第三部份:食品保存與微生物. 乾燥保存 Preservation by Control of Moisture. 黃顯宗 東吳大學 M202. http://hi2100.com/Memory/diwha/diwha02.htm. http://www.sankung.com.tw/product_content.aspx?ProdId=039. 教學目標. 瞭解微生物需求水分的特性 瞭解低水活性對微生物的影響 瞭解食品乾燥過程與濕度的變化與測量 瞭解乾燥食品的製作 瞭解乾燥後食品的微生物. 微生物需求水分的特性. 微生物的耐乾性 Xer o philes

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slide2

http://hi2100.com/Memory/diwha/diwha02.htm

http://www.sankung.com.tw/product_content.aspx?ProdId=039

slide3
教學目標
  • 瞭解微生物需求水分的特性
  • 瞭解低水活性對微生物的影響
  • 瞭解食品乾燥過程與濕度的變化與測量
  • 瞭解乾燥食品的製作
  • 瞭解乾燥後食品的微生物
slide4
微生物需求水分的特性
  • 微生物的耐乾性
    • Xerophiles
    • Xerodurics
    • Osmophiles
    • Osmodurics
    • Halophiles
slide5
微生物最低水分需求

Ayres et al., 1980

sarcina and staphylococcus
Sarcina and Staphylococcus

http://www.towson.edu/~gekpenyo/images/sarcina.gif

http://www.avma.org/onlnews/javma/nov03/031115a.asp

aspergillus niger
Aspergillus niger

http://www.sci.muni.cz/mikrob/Miniatlas/asp-ni.htm

http://www.cbs.knaw.nl/ICPA/ASPNIG2.JPG

http://res2.agr.ca/winnipeg/storage/images/lo-res/mould/aspe06-l.jpg

aspergillus glaucus
Aspergillus glaucus
  • http://www.ukneqasmicro.org.uk/ag.htm

http://res2.agr.ca/winnipeg/storage/images/lo-res/mould/aspe02-l.jpg

xeromyces bisporus
Xeromyces bisporus
  • 世界上最耐乾的菌水活性可以在0.6
  • 常現都是在0.80 以上
    • Xeromyces spp.一種黴菌
slide11
低水活性對微生物的影響
  • 減慢/抑制孢子發芽
  • 減慢生長速度
  • 降低產毒
  • 提高抗熱性
  • 體內累積 free amino acids and poly-alcohol (glycerol, mannitol,arabitol)
slide13
食品乾燥過程與濕度的變化與測量
  • Water activity
  • Water content
  • Hysteresis
water activity
水活性 Water Activity
  • 水活性Water Activity
  • 微生物可以自由利用的水
  • Aw=ERH/100=p/p0
  • 食品中「水活性」不等於「水含量 Water Content」
sorption isotherm
Sorption Isotherm
  • Adsorption Isotherm
  • Desorption Isotherm
  • Hysteresis
  • “Flask” hypothesis
slide16
測量Aw的方法
  • Gravimetric methods
  • Hygroscopicity of Salts
  • Hygrometric instruments
    • 如LiCl的導電度改變, Dew point的偵測

http://www.graintec.com.au/food_industry_analysers.htm

water content
Water Content的測量
  • Direct Method
    • Thermogravimetric analysis
    • Azeotropic distillation
    • Karl-Fisher method
    • GC
    • Refractometry
  • Indirect Method
    • 利用含水量對 Conductivity, sonic, ultrasonic waves的反應等
method of drying
Method of Drying
  • Sun-drying
  • Kiln , tunnels
  • Drum drying
  • Spray drying
  • Foam-mat
  • Vacuum drying
  • Freeze drying
  • Smoking : “ Case hardening “ phenolics
  • Hydrophilic :糖、鹽等
spray drier
Spray Drier

http://www.mansol-preforms.com/images/bigwashingmachine.jpg

slide21
問答
  • 煉乳算不算乾的食物?
slide22
問答
  • 蜜餞算不算乾的食物?

http://www.ipeen.com.tw/comment/133557

slide23
各類乾品的微生物
  • 穀物
  • 米,麵粉
  • 年糕
  • 月餅
  • 咖啡、tea mix
  • 果乾
  • 果醬,表面長黴菌
  • 濃縮果汁
  • 蜜糖
slide24
食物含水量的分類
  • Dry food , 20%
  • Intermediate-moisture food , 20~40%
  • Wet Food > 40%
slide26
加工後的處理
  • 抗濕
  • 抗氧化
slide27
安全之水活性
  • 0.725為較安全之水活性

Ayres et al., 1980

dried foods
Dried Foods 的微生物
  • 考慮因素
    • 原料種類與成份
    • 原來微生物量
    • 加工的過程
    • 事後的保存
  • 黴菌、酵母菌
  • 細菌:Spore formers , lactic acid , bacteria , micrococci , Coliforms , staphylococci 等
slide29
請思考
  • 如何準確計數乾燥食品裡的微生物量?
  • 如何減少速食麵裡調味包的微生物量?

http://www.ipeen.com.tw/comment/90907

slide30
請思考
  • 為何乾香菇和新鮮的香菇味道等感官上很不相同?

http://taiwanmurphs.pixnet.net/blog/post/94028174-%E5%AF%B6%E5%AF%B6%E5%89%AF%E9%A3%9F%E5%93%81%E9%A3%9F%E8%AD%9C%EF%BC%8C%E6%B3%A1%E6%B3%A1%E5%AA%BD%E7%9A%84%E5%AF%B6%E5%AF%B6%E9%A3%9F%E5%A0%82-~-%E9%A6%99%E8%8F%87%E8%8A%8B

http://zh.wikipedia.org/wiki/