Microbes, preservatives

Dehydration Processing. Dehydration is one of the oldest means of preserving food. Microbes generally do not grow below a minimum water activity, of 0.65 defined as the equiHbrium relative humidity surrounding food ia a sealed container at a given temperature, ie, no microbes can... 

In all fermented foods, microbes contribute as preservatives, ie, by lowering the pH and producing ethanol, or by making the food more palatable. The dehberate use of yeasts as food in themselves is less common. Small beer, the sediment from beer, has been traditionally used as a vitamin supplement for infants. Beginning in 1910, dried, spent brewers yeast was developed as a food, and Candida utilis was used as a food supplement in Germany during World War II. 

Since I wasn t likely to be eating it, I doubted it was for seasoning, despite the strawberry aroma of the liquid. It could have been used as a preservative, but the remaining ingredients were more likely to kill microbes than salt was. 

Prokaryotes do not synthesize sterols. Instead they create hopanotds, which have four six-membered carbon rings and one five-membered ring (Figure 22.8f). They provide rigidity to cell membranes and are very stable. Because of their widespread use by microbes and their resistance to degradation, they are well preserved in sediments and petroleum deposits, making them the most abundant natural products on Earth. 

Trans Coastal Marine Services (formerly Envirosystems, Inc.) and Louisiana State University (LSU) have developed several bioreactor systems to facihtate petroleum hydrocarbon mineralization and the bioremediation of organic wood preservatives utilizing an immobilized microbe bioreactor (IMBR) technology. These technologies can treat petroleum hydrocarbons, chlorinated solvents, pesticide-contaminated soils, and contaminated groundwater. 

FDA Guidance The specific bulk product solution filtration processes, including tandem filter units, prefilters, and bacterial retentive filters, should be described. A summary should be provided containing information and data concerning the validation of the retention of microbes and compatibility of the filter used for the specific product. Any effects of the filter on the product formulation should be described (e.g., adsorption of preservatives or active drug substance, or extractable). 

Theoretical Basis. Food preservation theory has yielded malhemadcat models for predicting the healing times and temperatures needed lo produce foods free of pathogenic or spoilage microbes. Mild heat treatments used to inactivate viruses, vegetative pathogenic bacteria such as Salmonella sp.. and certain yeasts and molds, are referred to as pasteurization operations. 

Equipment and processes for thermal preservation depend on the physical form ol the food and its pll. Foods having a pH < 4.5 often can be sterilized, for commercial purposes, at or near a temperature of I00°C. Commercial sterility lor these products means lhat the product will not spoil owing to microbial growth as long as the pH remains at or below 4.5 The spores of Bacillus <-oagulans are an important exception. This latter microbe is found in tomato products, and these products are often adjusted lo a pH of 4.0 or lower, or given an additional heal treatment. 

Freezing Preservation. The rate of loss of color, flavor, texture, and nutrients, the growth of microbes, and the aclivity of enzymes and other life forms are all functions of temperature Thus lower storage temperatures prolong the useful life of foods. 

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