Food Fermentation Basics

Food Microbiology - Beneficial Microbes in Food Processing

• Food processing utilizes beneficial microbes for various purposes, including preservation, enhancing flavor, improving digestion, and altering texture.
• Microorganisms have been utilized in food production for millennia, evident in the preparation of cheese, yogurt, bread, wine, and beer.
• Early forms of beer production date back to 7000 BC, while cheese production dates back to 3000 BC.
• Modern techniques in food processing are more advanced and controlled, yet the underlying principles of fermentation remain largely consistent.

Lesson VIII: Beneficial Microbes in Food Processing

• Analyze the advantages and disadvantages of emerging food preservation technologies and their impact on microbial food safety and food quality.
• Detail the use of beneficial microbes in food processing.

History of Food Fermentation

• Microorganisms have been utilized in food production for thousands of years.
• Historical examples include bread, vinegar, soy sauce, wine, beer, fermented beverages, and fermented milk products (like yogurt and cheese)

Summary of Fermentation Products & Timelines

Louis Pasteur and Fermentation

• Hypothesized that bacteria spoil wine.
• Suggested that wine could be heated to kill bacteria.
• Resulted in pasteurization.

Processes for Microbial Growth Prevention

• Refrigeration
• Freezing
• Drying
• Control of water activity (adding salt, sugar, polyols, etc.)
• Pasteurization
• Sterilization (canning)
• Cleaning and sanitizing
• Membrane processing

Fermentation Definition

• Fermentation is a metabolic process where carbohydrates and related compounds are partially oxidized, releasing energy in the absence of external electron acceptors.
• In food processing, it's the conversion of carbohydrates to alcohols and/or carbon dioxide or organic acids using a combination of yeasts, bacteria or both, under anaerobic conditions.

Fermentation - Pros and Cons

• Pros:*

• Extended shelf life (e.g., cheese).

• Improved digestibility (e.g., wild rice).

• Enhanced flavors (e.g., chocolate).

• Detoxification and softening.

• Cons:*

• Can be unpredictable (e.g., undesirable bacteria).

• May produce unwanted flavors (e.g., mouldy bread).

• Fermentation technologies can be complex and sensitive.

• Careful control is necessary.

Lactic Acid Fermentation

• A metabolic process where six-carbon sugars (or disaccharides) are converted into cellular energy and lactate (lactic acid).
• Takes place under anaerobic conditions.

Alcoholic Fermentation

• A metabolic process where sugars are converted into alcohol (ethanol) and carbon dioxide.
• Takes place under anaerobic conditions.

Types of Microorganisms in Food Production

• Bacteria
• Fungi (including yeasts and molds)
• Algae

Use of Microorganisms in Food Production

• Bacteria are used as starter cultures in cheese, yogurt, and other fermented foods.
• Molds are used for ripening cheese (e.g., blue cheeses) and in soya sauce production.
• Yeasts are used in bread, alcoholic beverages, and other fermented foods.
• Algae are used directly as food sources (e.g., seaweed, nori).

Benefits of Food Fermentation

• Develops flavors, aromas, and textures.
• Extends shelf life.
• Improves nutritional value.

Examples of Fermented Foods

• Foods using various ingredients: milk, meats, grains, plants, legumes, fruits, and fish.

Functions of Bacteria in Fermented Foods

• Lactobacillus bacteria (lactic acid bacteria) converts lactose into lactic acid, which plays a key role in preserving and altering food.

Functions of Yeasts in Fermented Foods

• Yeasts (like Saccharomyces cerevisiae) are used to produce alcohol and carbon dioxide in bread and beverages, driving fermentation.

Functions of Molds in Fermented Foods

• Molds (like Aspergillus oryzae) produce specific flavors and textures in some foods (like soy sauce and miso).

Cheese Production

• Cheese is a cultured milk product rich in casein and milk fat.
• Cheese varieties are differentiated by flavor, texture, milk type, seasoning added and the specific bacteria and molds used in ripening.

Cheese-Making Process

• Milk treatment (heating, pasteurization, cooling)
• Acidification (adding starter culture to convert lactose into lactic acid)
• Rennet (or acid) addition to coagulate the milk protein, forming curds.
• Pressing (removing the whey and compacting the curds)
• Salting (enhancing flavor, preservation)
• Ripening (allowing bacteria and/or molds to further affect flavor and texture).

Examples of Cheese Ripened by Bacteria

• Cheddar cheese uses Lactobacillus bacteria.

Examples of Cheese Ripened by Molds

• Blue cheeses (e.g., Stilton) use Penicillium Roqueforti.
• Camembert and Brie use Penicillium camemberti.

Yogurt Production

• Yoghurt is a cultured milk product.
• A starter culture (a mixture of Lactobacillus and Streptococcus bacteria) is used to ferment milk, converting lactose into lactic acid.
• Coagulation of milk protein occurs due to lactic acid production, setting the texture of yogurt.
• The bacteria are responsible for the taste and thickening.

Yogurt-Making Process

• Milk treatment (heating, pasteurization, cooling to optimal temperature)
• Addition of starter culture.
• Fermentation to create lactic acid and change the texture.
• Packaging

Fermented Vegetables

• General steps often involve preparing vegetables, salting, storing/fermenting, and packaging resulting in diverse flavors.

Fermented Meat

• Meat fermentation extends shelf life to allow products like sausage to age and develop.
• Curing salts contribute to taste and safety.
• Lactic acid bacteria are common starter cultures, but other microorganisms may also be used.
• Examples: salami, ham

Yeast Bread

• Fresh or dried yeast is used producing carbon dioxide and alcohol.
• The gas produced expands causing the dough to rise.
• The alcohol evaporates during baking.
• Ingredients often include flour, sugar, butter, salt, yeast, water.

Yeast Bread - Growth Requirements

• Yeast is a living organism requiring specific conditions for growth.
• Sugar is a food source for yeast in many fermentations.
• Warmth is necessary for yeast growth; temperatures must be controlled to avoid denaturing the yeast.
• Water is needed to bind flour and give dough structure.

Beer and Wine

• Alcoholic beverages (beer and wine) are produced by using yeast to ferment grains (for beer) or fruits (for wine).
• Enzymes in yeast convert sugars to alcohol and carbon dioxide within their processes.

Beer Production - Yeast Functions

• Barley is the primary grain used.
• Enzymes (created during malting) convert starches within the barley into soluble sugars which yeast can utilize for fermentation.
• Hops are added for flavor, aroma and act as preservatives.
• Different yeast strains create the varied flavors and types of beer.

Key Points in Wine Production

• Wine production is generally from fruits (especially grapes).
• Sugar and starches in fruit/grains provide fermentable sources.
• Yeast strains determine the specific flavors of the wine.

Microorganisms Added to Foods to Enhance Nutritional Value (Probiotics)

• Probiotics are live microbial food ingredients with health benefits.
• Probiotics maintain a healthy digestive system and improve the immune system.
• Yogurt frequently contains Lactobacillus and bifidobacterium as probiotics.

Direct Use of Microorganisms as Food Sources

• Cyanobacteria (like Spirulina) and algae (like seaweed or nori) are used directly in some foods as they have high nutritional value.

Test your knowledge on food fermentation and its benefits. This quiz covers essential processes in the production of fermented foods, including the roles of bacteria and yeast. Discover how fermentation impacts shelf life, nutritional value, and more!