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The aim of this study was to establish the relationship between the number of lipolytic bacteria, the season of the year, and susceptibility of goat milk fat to lipolysis. The study was carried out on 60 Polish White Improved goats. The animals were divided into two groups (30 goats in each) according to the number of lactations. Goats were maintained in pens and fed diets according to the INRA-system. Milk samples were taken once a month and analysed for fat, total protein and lactose content and somatic cell count. Moreover, each milk sample was analysed for the number of lipolytic bacteria and free fatty acids (FFA) immediately after milking and subsequently after 72 hours (storage in temperature 4°C). The levels of FFA in milk directly after milking in each season of the year were almost equal (the differences were insignificant). However after 72 hours the concentration of FFA tripled during the spring and the summer, while during the autumn the increase of level of FFA was negligible in comparison to the level at milking time. In the stored milk samples the number of lipolytic bacteria increased 460, 70 and 6-fold during the spring, the summer and the autumn, respectively. The obtained results indicate that there is no strong relationship between the increase of the number of lipolytic bacteria and the level of FFA. In the milk from primiparous goats the number of psychrotrophic bacteria and the level of FFA was significantly lower in comparison to milk of goats in the 2nd lactation. The authors suggest the need for further investigations concerning the identification of individual strains of lipolytic bacteria, proliferate rate and scale of lipolysis of fat in goat’s milk during storage at 4°C.
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Metabolizm lipidow w zwaczu

75%
The sources of lipids and fatty acids in feeds for ruminants were specified. Digestion of lipids in ruminants is singular because of ruminal digestion. Rumen has a powerful lipase system, which is responsible for rapid hydrolysis of the dietary lipids to unesterified fatty acids. Then, they are hydrogenated by microbes to more saturated final products, mainly stearic acid. The consequences of increase in dietary lipids for structural carbohydrates and protein digestion are discussed.
Omówiono zmiany lipolityczne towarzyszące procesowi technologicznemu wyrobu masła. Przedstawiono zagrożenia lipolizą na etapie pozyskiwania i wirowania mleka, pasteryzacji i dojrzewania śmietanki, a także obserwowane w procesie zmaślania i końcowych etapach produkcji masła. Wykazano wpływ WKT na cechy organoleptyczne produktu. Przytoczono główne sposoby ograniczania zakresu lipolizy w wyniku właściwego doboru i przestrzegania parametrów technologicznych.
World production of goat milk has increased In the last 20 years, especially in developed countries. Goat milk is differentiated from cow milk in many parameters, among others in size of fat globules and fatty acid profiles. Milk fat is one of the main milk components and decides about its nutritive, energetic and technological values. The components of goat milk fat are triglicerides (ca. 95%), diglicerides (2%), monoglicerides (0.08%), phospholipids (1%), free fatty acids (0.28%), total cholesterol (0.5%) and fat soluble vitamins (A, D, E, K). The fatty acid profile of goat milk differs from those of cow milk mainly because goat milk contains twice as much of short chain fatty acid (C6:0; C8:0; C10:0) as does milk from cows. Those fatty acids decide about its sensory and organoleptic and health-promoting parameters. The content of cholesterol in goat milk depends of many factors, primarily the feeding system and secondary stage of lactation. It can reach values between 2 and 24 mg/100ml of milk. Cholesterol is mainly connected to fat globules. The lipolitic phenomenon, which occurs in the fat fraction, is connected with an increase of the free fatty acid concentration and other substances that have an undesirable influence on milk quality and its products.
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