Pressure, enzyme activity microorganism

Knorr, D. Bottcher, A. Domenburg, H. Eshtiaghi, M. Oxen, R Richwin, K. Seyderhelm, I. High pressure effects on microorganisms, enzymes activity and food functionality. In High Pressure and Biotechnology Balny, C. Hayashi, R. Heremans, K. Masson, R, Eds. John Libbey Eurotext, London, 1992 pp. 211-218. 

Microorganisms and enzymes need water in order to be active preservation of foods can be sought by reducing their moisture content to a point where the food-spoilage of pathogenic microorganisms are inhibited. Scott [ 1,2] called the equilibrium relative humidity (ERH), which is the availability of water in a food medium. Water Activity (a, ). a, is defined as the ratio of vapour pressure (p) of solution to the vapour pressure (Po) of the solvent, usually water ... 

This turpentine is then distilled at a pressure of around 50 Torr and temperatures of up to 150°C into heads (volatile compounds with almost no commercial value), and a-pinene (bp 156°C) and P-pinene (bp 164°C). Of these, P-pinene is sold as is and a-pinene is further processed to make pine oil. The conversion of a-pinene to pine oil (Figure 3B.5), of which the major component is the tertiary alcohol a-terpineol, involves hydration catalyzed by aqueous sulfuric acid with simultaneous ring-opening and formation of a carbenium carbocation intermediate when the double bond is protonated to give crystalline terpin monohydrate (combustible, efflorescent, lustrous crystals, soluble in alcohol, and ether, mp 117 °C,bp 265 °C), followed by partial dehydration to a-terpineol. Suitable catalysts for this are weak mineral acids or acid-activated silica gel. ° Inversely, terpineol can be synthesized by acid catalysed hydration or enzyme catalysed addition of water to limonene using a wide range of microorganisms as catalyst. The bioconversion of (R.)-(+)-limonene catalyzed by limonene hydratase selectively forms (R)-(+)-a-terpineol. 

The application of high pressures can inhibit the growth of microorganisms and the activity of enzymes. This allows the protection of sensitive nutrients and aroma substances in foods. Some products preserved in this gentle way are now marketable. Microorganisms are relatively sensitive to high pressure because their growth is inhibited at pressures of 300-600 MPa and lower pH values increase this effect. However, bacterial spores withstand pressures of >1200 MPa. 

FUNCTIONS OF CHLORINE. Chlorine, in the form of the chloride ion which is negatively charged, plays a major role in the regulation of osmotic pressure, water balance, and acid-base balance. The chloride ion is also required for the production of hydrochloric acid by the stomach. This acid is necessary for proper abrsorption of vitamin B-12 and iron, for the activation of the enzyme that breaks down starch, and for suppressing the growth of microorganisms that enter the stomach with food and drink. 

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