Deterioration microbial

Ethanol and 2-propanol have also found use ia disinfecting clinical thermometers, and as preservatives to prevent microbial deterioration of cosmetics and mediciaals. They are sometimes combiaed with other disiafectants, namely formaldehyde (69), phenoHcs (70), chlorhexidine (71), hypochlorite (72), and phenols (70). 

Microbial deterioration of plastics is intimately involved with the moisture problem, especially with regard to plastics in electronic equipment. For this reason much of the literature treats the two problems together. Furthermore, there is often confusion between the deterioration of the electrical properties of plastics, more often than not a moisture phenomenon, and actual deterioration of the substance of the polymer. 

Abiotic spoilage is produced by different physical and chemical changes such as hydrolytic action of enzymes, oxidation of fats, breakdown of proteins, and a browning reaction between proteins and sugars. However, in this chapter we focus on microbial deterioration and their effects on bioactive compounds. 

Microbiological Quality of Tofu. Tofu is a protein-rich substrate with pH around 6, hence it is quite susceptible to microbial growth. Traditionally, tofu has been made and consumed in the same day. However, in the United States, tofu may be held at the supermarkets for many days on produce counters before consumption where temperatures are usually 10-15°C. Thus, microbial deterioration becomes a serious problem (23-25). 

Tofu can be kept frozen or freeze-dried to prevent microbial deterioration. However intemolecular interactions occur during frozen storage. As a result, the texture of tofu is changed from soft, smooth to sponge-like with a meat-like chewiness. 

The storage condition of raw materials, particularly hygroscopic substances, is important, and as a minimum water activity (Aw) of 0.70 is required for osmophilic yeasts, 0.80 for most spoilage moulds and 0.91 for most spoilage bacteria, precautions should be taken to ensure that dry materials are held below these levels. Some packaging used for raw materials, such as unlined paper sacks, may absorb moisture and may itself be subject to microbial deterioration and so contaminate the contents. For this reason polythene-lined sacks are preferable. Some liquid or semi-solid raw materials contain preservatives, but others such as syrups depend upon osmotic pressure to prevent the growth of os-mophiles, which are often present. With this type of material it is important that they are held at a con-... 

The acute bacterial toxins associated with food poisoning episodes are not commonly reported in pharmaceutical products, although aflatoxin-producing aspergilli have been detected in some vegetable ingredients. However, many of the metabolites of microbial deterioration have quite... 

Pectin methyl esterase in juices requires processing times of 10 min combined with pressures of 600 and 1000 MPa and temperatures of 57 and 20°C, respectively. These combinations prevent microbial deterioration, but must be combined with a mild blanching, refrigerated storage and addition of inhibitory enzymes to achieve a stable product with respect to pectin methyl esterase (Cheftel, 1992). Guava puree samples were treated with pressures of 400 and 600 MPa looking for pectinesterase and pol)q)henoloxidase inactivation. The residual activity of the former was greater than 76%, while of the latter was above 63% at the lower pressure. 

Products used for the preservation of films or eoatings by the control of microbial deterioration in order to protect the initial properties of the surface of materials or objects such as paints, plastics, sealants, wall adhesives, binders, papers, art works. 

To sum up, the microbiological quality of water may change during distribution to the consumers. This may be due to many factors and can present health problems. Factors responsible for microbial deterioration of water quality are summarized in Table 4.3. 

Table 4.3. Microbial deterioration of water quality during distribution [61]...

The most important requirement in cellar work is cleanliness in the winery and hygiene in all containers (Peynaud, 1975). Wine gives the impression of a certain stability, due to the presence of alcohol and relatively high acidity. In fact, it is sensitive, not only to microbial deterioration but also to various types of contamination that may give the wine unpleasant odors and off-flavors that are impossible to eliminate. Cleanliness in all winemaking operations, from fermentation to bottling, is an indispensable prereqnisite for qnality. 

SOB are being used in industry to make it profitable These bacteria are being anployed in bioleaching. As bioleaching can be regarded as preplanned microbial deterioration process, it will be briefly introduced here with more emphasis on the use of SOB. 

In the following section, microbial deterioration of concrete will be studied in more detail. 

The possible influence of cross-link density on the microbial deterioration of vulcanized NR has been obscured by the microbiocidal activity of the curing agent. In the curing system of CBS-sulphur, however, it was observed that the resistance of the vulcanizates is in good correlation with the cross-link density, regardless of the content of sulphtir or CBS (Figure 2) [42]. 

Up till now, the purpose of most studies has been to protect rubber products from microbial deteriorations. Waste disposal of used rubber and estimation of the degradation rate in the natural environment will become more important subjects from now onward. 

The microbial deterioration and oxidation of foods are the major problans that arise in increasing the shelf life of foods. However, food preservation has been achieved snccessfully with the chemical preservatives. The growing consumer demand toward foods without ch ical preservatives has received attention due to natural preservatives, including chitin, chitosan, and COS. The special properties such as antimicrobial activity and antioxidative activity allow the chitin, chitosan, and especially COS to get successful as natural preservatives in the food indnstry. 

Ideally, mature fruit should be harvested in a manner that produces the least mechanical damage. At issue here is premature expression of juice leading to uncontrolled enzymatic and microbial deterioration. Because both are influenced by temperature, effort has been made, particularly in the case of machine harvesting, to utilize nighttime and early morning harvest, thereby taking advantage of lower ambient temperatures. 

Blanchette, R.A. (2000) A review of microbial deterioration found in archaeological wood from different environments. International Biodeterioration Biodegradation, 46,189-204. 

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