Scanning electron microscopic and texture studies on characteristic consistency of Nordic ropy sour milk.
The characteristic consistency of Nordic ropy sour milk was studied. Skim milk, reconstituted from non-fat dry milk, was fermented at 20 degrees C for 24 h by addition of 5% (v/v) inoculum of slime-producing (ropy) strain of Lactococcus lactis ssp. cremoris SBT 0495, isolated from Finnish ropy sour milk 'viili' starter culture, and its non-ropy variant SBT 1275. Measurements of texture showed that milk gel prepared by the ropy strain exhibited remarkably increased adhesiveness as compared to that by the non-ropy variant. Milk gel prepared by the ropy strain also exhibited decreased syneresis (wheying-off) as compared to that by the non-ropy variant. Scanning electron micrographs of milk gel prepared by the ropy strain showed that slime was in the form of a network attaching the bacterial cells to the protein matrix. A thick network of slime attached the casein micelle clusters to each other to make casein conglomerates, which is likely to result in the characteristic consistency of 'viili'.
Toba
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Laboratory of Animal Products Technology, Faculty of Agriculture, Tohoku University, Sendai, Japan.
Nakajima
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H
Tobitani
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Adachi
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D000818:Animals; D005285:Fermentation; D005516:Food Microbiology; D013294:Lactococcus lactis / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D008892:Milk