UHT cream. Raw material quality
1996
Kosinski, E. (Dairy Crest Limited, Shropshire (UK))
Raw material quality of the highest standard is required in the manufacture of good quality Ultra High Temperature (UHT) cream. This chapter looks at the importance of raw milk quality and investigates the factors that may affect it. The term 'quality' refers to the composition, freedom from pathogenic organisms and toxic substances, acceptable sensory characteristics and meaningful nutritive value of the raw milk. High quality raw milk for UHT cream manufacture must therefore be of acceptable composition and free from taints, antibiotics, blood and visible sediment. It must be held at less than 5 degrees between milking and processing to prevent the rapid growth of spoilage and pathogenic organisms and must be processed as quickly as possible to prevent the formation of proteinases, lipases and spores. The following key factors that affect the quality of raw milk used in the manufacture of UHT cream are discussed in detail: (1) Good hygienic practice: with particular reference to animal health, hygiene of the holding, hygiene of the dairy, microbiological standards and temperature during storage ; (2) Off-flavours: particularly those resulting from feed, chemical reaction, absorption and development during storage ; (3) Physical handling: and especially the effects of dissolved, bound or dispersed air on the milk components and especially the fat ; (4) Enzymes: and predominantly the effects of lipases, proteinases and lactoperoxidase on milk components ; (5) Heat stability: and factors that affect it. Details of tests that may be used to indicate the suitabily of raw ingredients to withstand the UHT process are included ; (6) Spore formers: such as Clostridium perfringens and Bacillus cereus which are usually present due to poor farming practices and can cause sweet curdling or bitty cream.
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