28.1 Food Microbiology

• The Hazard Analysis and Critical Control Point (HACCP) system is designed to prevent contamination by identifying points at which foods are most likely to be contaminated with harmful microbes.

• Industrially canned goods undergo commercial sterilization by steam under pressure in a large retort, which operates on the same principle as an autoclave.

• Thermophilic anaerobic spoilage is therefore a fairly common cause of spoilage in low-acid canned foods.

  • When thermophilic spoilage occurs but the can is not swollen by gas production, the spoilage is termed flat sour spoilage.

• The use of aseptic packaging to preserve food has been increasing.

• This product, called malt, contains starch-degrading enzymes (amylases) that convert cereal starches into carbohydrates that can be fermented by yeasts.

  • These bacteria convert the malic acid to the weaker lactic acid in a process called malolactic fermentation.

28.2 Industrial Microbiology and Biotechnology

• The word biotechnology was first used in 1918 to describe the use of living organisms to produce products—in reference to combining agriculture and technology.

• A primary metabolite is formed essentially at the same time as the new cells, and the production curve follows the cell population curve almost in parallel, with only minimal lag.

  • Secondary metabolites are not produced until the microbe has largely completed its logarithmic growth phase, known as the trophophase, and has entered the stationary phase of the growth cycle.

• Prominent among these is biomass, the collective organic matter produced by living organisms, including crops, trees, and municipal wastes.

• Microbes can be used for bioconversion, the process of converting biomass into alternative energy sources.

• Biofuels are energy sources produced from living organisms, rather than from fossils of organisms that lived over 300 million years ago.

• The initial interest has focused on ethanol, which is already widely used as a supplement to gasoline, and the technology is well established.

• In microbial fuel cells, exoelectrogens are grown in a nutrient medium such as soil or wastewater.