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huyueming321銅蟲 (小有名氣)
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[求助]
高水分含量下微生物更容易殺死的原因 已有1人參與
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微生物在水分活度越低越難殺死,求談論這方面的原因?是不是高水分含量下微生物更容易殺死?熱處理時 我在文獻中有看到低水分時滲透壓使微生物迅速失水體積變小,然后細胞膜變厚,膜通透性和流動性降低。熱處理時跟這些變化有關(guān)系嗎,這樣對不對?大家有其他解釋嗎或者文獻? The protection of the microbial cells at low water activity can be mainly due to the osmotic pressure that induced rapid water loss from the cell. Thus result in cell shrinkage, which probably causes a thickening in the cell membrane, followed by reduced membrane permeability and fluidity, and the increase of water activity will result an opposite effect.這是我寫的原文,大家看合不合適? |
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC238580/ Title: Survival of Bacteria and Fungi in Relation to Water Activity and the Solvent Properties of Water in Biopolymer Gels Survival of bacteria (Rhizobium, Agrobacterium, and Arthrobacter spp.), fungal spores (Penicillium sp.), and yeasts (Saccharomyces sp.) was studied in relation to water activity (aw) and the presence of nutritive solutes. The cells were entrapped in polysaccharide gels, as is done to immobilize cells or enzymes, and then dehydrated. The number of living cells (1010 g of dry polymer−1) remained constant for periods of storage of >3 years at 28°C when the inocula were kept at an aw of <0.069. At aw values between 0.069 and 0.83 the number of survivors diminished more and more rapidly as the aw was raised. For a given aw and organism, there were large differences in survival rate as a function of the nutritive solutes used to culture the microorganisms. Low-molecular-weight compounds (with three or five carbon atoms) had a deleterious effect on survival, whereas compounds of higher molecular weight (C6 to C12) had a protecting effect. Thus, the aw alone was not a sufficient explanation for the deterioration of the inocula. Survival seemed to be more directly related to some properties of the water in the biopolymer. New concepts such as the discontinuity of properties of water and the point of mobilization of solutes, already proposed by Duckworth and Kelly (J. Food Technol. 8:105-113, 1973) and Seow (J. Sci. Food Agric., 26:535-536, 1975), have been taken into consideration to explain the interactions of water with the biopolymer and their specific effects on the microorganisms. |

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