This requires using a pressurized container since water can't be heated above boiling. A generation ago, cooks who didn't have pressure cookers would boil foods in jars to kill most of the bacteria. Then they cooled the jars for a few hours to allow the remaining spores to germinate. Then they boiled the foods again, killing the now vulnerable bacteria. If someone is cooking in an unsealed container like a saucepan, new microorganisms will quickly replace the killed ones.
Food additives Spices such as cinnamon and cloves have been used for centuries as preservatives.
Other spices had little effect on microbes but were used to cover up the taste and smell of foods that no longer tasted and smelled fresh. Nitrites are added to bacon, ham and other meats to prevent the growth of Clostridium botulimum , the bacterium that causes a deadly form of food poisoning. Propionate, sorbate and benzoates are added to many commercially prepared foods to increase their shelf life. Smoking Smoking dries out meat or fish at the surface and that stops some microbial growth. The smoke also contains a variety of compounds that limit microorganism's growth.