Food Microbiology: Preservation, Safety, and Industrial Applications
Preserved foods, often produced from aerobic fermentation using Aspergillus genus fungi, include supplements and food additives. Highlights include vitamins such as B12 and the amino acid ASPAT, as well as glutamine, phenylalanine, etc. 2.1.2. Preservation of Food Against Microorganisms: Food can be broken down and altered by microorganisms. Several preservation methods exist, including: A) Regulation of Humidity: Controlling water content prevents microorganism proliferation. Methods include: – Drying or dehydration (naturally or via lyophilization/vacuum drying). – Adding salt or sugar (e.g., salted meats or jams). – Adding preservatives (ranging from compounds from smoked food to citric acid and antibiotics). Storage at Low Temperatures: Around 4°C (cooling) or below 0°C (freezing). Rapid freezing prevents cellular damage. Rising Temperatures: To kill microorganisms. – Pasteurization: Uses temperatures below boiling point, destroying some organisms, but others may survive and grow later; pasteurized food requires refrigeration and has a short shelf life. – Sterilization: Uses very high temperatures and airtight containers, allowing for long-term storage. 2.1.3. Foodborne Diseases: Food Poisoning (caused by toxins produced by microorganisms): – Botulism: Caused by toxins from Clostridium botulinum bacteria, found in various environments. Improperly cooked food can be fatal. – Staphylococcal Poisoning: Caused by toxins from Staphylococcus sp. Symptoms (nausea, vomiting, diarrhea) appear 1-6 hours after ingestion. Often linked to improperly cooled cooked foods. Food Infections (caused by microorganism growth in the human body): – Salmonellosis: Caused by Salmonella sp. Symptoms include sudden pain, headache, chills, vomiting, diarrhea, and fever. Often linked to raw eggs (mayonnaise, meringues, custards). – Gastroenteritis: Some strains of pathogenic Escherichia coli. – Peptic Ulcers: Caused by Helicobacter sp. – Hepatitis A: Caused by a retrovirus; often transmitted through raw shellfish.
2. Microorganisms in Industry: Industrially used microorganisms are selected for specific biochemical changes and product creation. Requirements include: – Production of a substance of interest. – Rapid growth and cultivation. – Utilization of low-cost carbon sources (e.g., waste products). – Easy removal of cells. – Capability of genetic manipulation. (Industrial fermentation, often aerobic, is conducted in large tanks (fermenters) up to 50,000 liters.) 2. Microorganisms and the Food Industry: Food of Microbial Origin: Food from Microorganisms: Organisms cultured as food (e.g., yeast as a protein supplement, algae and cyanobacteria for animal feed). Dairy Products: Fermented milk (Streptococcus and Lactobacillus), butter (Streptococcus sp.), and various cheeses (mold species). Alcoholic Beverages: Using Saccharomyces yeasts (e.g., S. cerevisiae in beer) for anaerobic fermentation of sugar-rich juices into CO2 and ethanol: – Wine (grape juice fermentation). – Beer (S. cerevisiae, from malt). – Cider (apple juice fermentation). Baking Industry Products: Vinegar: Ethyl alcohol converted to acetic acid by vinegar bacteria. Citric Acid: Used as a preservative in beverages and foods.