Vegetative micro-organisms

At that time few micro-organisms capable of using methanol as sole source of carbon methylotrophs and energy (methylotrophs) had been isolated, and so steps were taken to isolate such organisms from samples of soil, water and vegetation. 

Relatively stable substances that resist degradation at high temperatures (>140°C) are suitable candidates for dry heat sterilization. A 2-h exposure at 180°C or 45 min at 260° C kills spores as well as vegetative forms of micro-organisms. These exposure periods do not include the lag time from loading of the oven until sterilization temperature is reached. The lag time depends on the geometry and operating features of the oven and the characteristics of the load. 

Ethylene oxide (bp, 10.8°C) is a gaseous alkylating agent. It alkylates proteins and ribonucleic and deoxyribonucleic acid in micro-organisms. It replaces labile hydrogen with hydroxyethyl groups. Ethylene oxide is utilized as a surface sterilant. Bulk crystalline materials can occlude vegetative bacterial cells or spores with crystals. Consequently, ethylene oxide does not reach them. The final step prior to sterilization is an aseptic recrystallization step. 

The reduced decay at 98-100% relative humidity as compared to that at 90-95% for carrots and possibly several other vegetables is at least in part caused by a lower production of pectolytic enzymes by the pathogenic micro-organisms at the higher humidity level. 

It is difficult to be specific about microbial damage in fruit and vegetables because there is usually a succession of micro-organisms and each commodity will differ. However, numerous different types of spoilage can be recognised. 

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