文档介绍：Chapter 10 Food deterioration caused by microbes
SectionA Grain deterioration
of grain microbial flora
flora: groups of microbes existed in a certain ecological conditions
major sources of grain micobes
Soil, water, air, transportation, processing, storage ,appliances
existent position of grain microbes
Mainly on the surface , some in the cortex layer.
2. Major microbial groups in the grain and their detrimental effects
bacterial
Newly cropped grain has the largest amount of bacteria.
Don’t endanger the grain quality under conventional storage condition
actinomyces
Mostly indwell grains carry the mud
Mainly endanger those grains with high water content
yeasts
Little quantity in the grains
Endanger the grains with high water content and stored in a sealed condition
moulds
Major groups are aspergillus, peniicillium,镰刀菌
The major detrimental microbes in the grain.
Environmental condition
Ecological types
Typical moulds
water activity
<
干生型
灰绿曲霉(Aspergillus glaugus) 局限曲霉(Aspergillus restrictus)
~
中生型
黄曲霉(Aspergillus flavus)
棕曲霉(Aspergillus ochraceus)
大多数青霉(Penicillium sp.)
>
湿生型
黑根霉(Rhizopus nigricans)
高大毛霉
temperature(℃)
< 20℃
低温型
枝孢霉(Cladosporium sp.)
20℃~40℃
中温型
大多数青霉(Penicillium sp.)
大多数曲霉(Aspergillus sp.)
> 40℃
高温型
烟曲霉(Aspergillus fumigatus)
O2content(%)
Normal O2 content(21%)
好氧型
大多数青霉(Penicillium sp.)
大多数曲霉(Aspergillus sp.)
Low O2 content (< 1%)
耐低氧型
灰绿曲霉(Aspergillus glaugus)
changing rules of grain microbial flora under traditional storage
bacterial amount
The total amount rapidly dropped
The amount of spore-bearing bacteria keeps
stable
The total moulds amount has a tendency to drop
Field-type dropped
Storage-type moulds keep stable
moulds
、 surface (external) moulds
moulds
moulds dwell inside the grain
Similar to the changing rules of surface moulds, but within a small extent
4、basic rules when stored grain get mouldy
grain