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UHT Processing of Milk

Milk is a highly perishable food so to enable it to be stored and distributed for consumption without spoilage, and without being a health risk through growth of pathogenic bacteria, it is heat treated. The most common type of heat treatment in many parts of the world is pasteurisation, which is performed at a minimum of 72°C for 15 seconds. This is the least heat treatment needed to destroy most pathogenic microorganisms and it also destroys most spoilage organisms. However, a small number of bacteria remain after pasteurisation and packaging, and can grow during storage. Such growth is slow at low temperature and consequently pasteurised milk is always kept refrigerated. Even under refrigeration, pasteurised milk only keeps for about two weeks. There are two ways in which this can be carried out: in-container sterilisation and ultrahigh- temperature (UHT) processing. Both produce a ‘commercially sterile’ product which means the milk does not contain microorganisms which can grow un...
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TCA Cycle

TCA CYCLE 18.1 Introduction The citric acid cycle, also known as the TCA (tricarboxylic acid) cycle or Krebs cycle (after its discoverer in 1937), is used to oxidize the pyruvate formed during the glycolytic breakdown of glucose into CO 2  and H 2 O. The cycle is a major energy source in the form of ATP and also produces precursors for many biosynthetic pathways. The citric acid cycle operates in the mitochondria of eukaryotes and in the cytosol of prokaryotes. Succinate dehydrogenase, the only membrane-bound enzyme in the citric acid cycle, is embedded in the inner mitochondrial membrane in eukaryotes and in the plasma membrane in prokaryotes. 18.2 The cycle The cycle forms the central part of a three-step process which oxidizes organic fuel molecules into C O 2 with the concomitant production of ATP. 18.2.1 Step 1 – Oxidation of fuel molecules to acetyl CoA A major source of energy is glucose which is converted by glycolysis into pyruvate. Pyruvate dehydrogenase (a comple...
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