Food Microbiology

Fermentation shapes the taste, texture, and shelf life of many foods. Microorganisms change carbohydrates into organic acids, alcohols, and other metabolites. These products can slow spoilage microbes, improve digestibility, and create the flavors people expect in baked and dairy foods.

Bread making depends on yeast fermentation and the starch in flour. Amylases in flour break starch into simple sugars such as glucose. Saccharomyces cerevisiae then ferments these sugars without oxygen. During...

Microbes shape the production of wine, beer, and spirits by turning sugars into ethanol and flavor compounds. Yeasts and bacteria carry out these fermentations. Producers select and control these microbes to create the desired traits in each beverage.

Wine production starts with crushing grapes to make a must, which is the juice and pulp mixture. This must can be contaminated by wild microorganisms, so sulfur dioxide is added as an antimicrobial agent. The process then begins with...

Lactic acid bacteria and molds help turn plant foods into stable fermented products. They change plant sugars into organic acids and other compounds. These changes slow spoilage organisms and also shape the taste and texture of the final food.

Sauerkraut shows how fermentation can change over time. It starts with cocci, which are round bacteria such as Leuconostoc mesenteroides. These microbes make lactic acid and CO2, which helps create an anaerobic, or oxygen-free, environment. As the food...

Probiotics are live, non-pathogenic microorganisms that support health by helping balance the gut microbiota. The gastrointestinal tract contains a complex community of microbes, and keeping that community in balance is important for digestive health and overall health. Many of the best-studied probiotics were formerly classified in the genera Lactobacillus and Bifidobacterium.

These microbes are found naturally in the human gut and are also taken in foods such as yogurt, kefir, cheese,...

Microbes can spoil food by breaking it down during growth and metabolism. Bacteria, yeasts, and molds all play a role in food spoilage. Their activity depends on moisture, nutrients, and storage conditions, which affect how well they grow on different foods.

Bacteria are a major cause of spoilage in foods with lots of water and nutrients, such as meat, milk, and vegetables. Species such as Pseudomonas, Clostridium, and lactic acid bacteria break down proteins, fats, and carbohydrates. This...

Pasteurization is a heat treatment used to make food and drinks safer and help them last longer. It works by heating a product for a set time to kill disease-causing microbes and reduce enzymes that cause spoilage. It is especially important for perishable items like milk, fruit juices, beer, and vinegar.

Different pasteurization methods use different temperatures and times. Low-temperature-long-time, or LTLT, heats products to about 63 °C (145 °F) for 30 minutes. This method is often used for...

Food contamination can happen at many points from the field to the table. Microbes and natural toxins may enter the food supply through the environment, processing, or storage. Knowing these routes helps explain how food safety is protected.

Seafood is especially vulnerable because it can pick up hazards from the water. Harmful algal blooms can leave toxins in marine organisms, and Vibrio bacteria can colonize shellfish. These foods can then spread foodborne illness.

Poultry and red meat can...

Food preservation slows spoilage by limiting microbial growth, enzyme activity, and environmental damage. These changes protect a food’s taste, nutrients, and safety for a longer time. The main goal is to keep food quality stable before it breaks down.

A key idea in food microbiology is the microbial growth curve. It has four phases: lag, exponential or log, stationary, and death. In the lag phase, bacteria adjust to their new environment but do not multiply much. Extending this phase through...

Food preservation uses temperature, moisture control, preservatives, and packaging to slow spoilage and keep food safe. Food spoils because microbes grow, or because chemical and physical changes alter taste, texture, and safety.

Refrigeration and freezing are key temperature-based methods. Refrigeration at 0–4 °C slows microbial growth and enzyme activity, so it works well for short-term storage. Some spoilage organisms, such as psychrotrophs like Listeria monocytogenes, can still grow at...

Good Manufacturing Practices (GMP) help keep products safe, consistent, and high quality. These guidelines are used in industries such as pharmaceuticals, biotechnology, and food processing. They cover every step of production, from the raw materials to the final distribution of the finished product.

A major part of GMP is hygiene and sanitation in the production area. Work surfaces, equipment, and tools are cleaned and disinfected on a regular schedule to reduce microbial contamination.

HACCP is a science-based food safety system that helps control biological, chemical, and physical hazards during food production. It is used around the world to prevent unsafe food from reaching consumers. The system was first developed by NASA and the Pillsbury Company for astronaut food, and it is now a key part of the Codex Alimentarius.

Before HACCP is used, food producers rely on prerequisite programs. These include Good Manufacturing Practices, sanitation procedures, and supplier...