Food Fermentation Basics

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Questions and Answers

What is the primary benefit of food fermentation regarding the shelf life of products?

Enhances flavors through chemical reactions

Decreases the nutritional value of food

Increases the production of synthetic preservatives

Extends the shelf life of food (correct)

Which of the following is NOT an example of fermented food derived from plants?

Oolong tea

Fermented bean curd (correct)

Kimchi

Sauerkraut

What role does Lactobacillus bacteria play in fermented food production?

They preserve food through dehydration

They enhance the color of the food

They act as artificial flavors

They convert lactose into lactic acid (correct)

Which of the following fermented foods is made from grains?

Beer Signup and view all the answers

What is one of the primary outcomes of food fermentation concerning nutritional value?

It synthesizes probiotic compounds Signup and view all the answers

What is the primary purpose of curing salts in fermented meat products?

To contribute to taste, color, safety, stability, and texture Signup and view all the answers

Which types of bacteria are primarily used as starter cultures in fermented meats?

Lactic acid bacteria Signup and view all the answers

Which ingredient is essential for yeast growth in yeast bread production?

Sugar for energy Signup and view all the answers

What occurs to the gas bubbles produced by yeast when dough is heated?

They expand and help rise the dough Signup and view all the answers

What effect does cold temperature have on the fermentation process of bread dough?

Slows down the rising process Signup and view all the answers

What is the purpose of adding starter culture during cheese processing?

To convert lactose into lactic acid Signup and view all the answers

What role does rennet play in cheese production?

It coagulates the milk protein casein Signup and view all the answers

What is the primary function of probiotics in the human body?

To maintain a healthy digestive system and strengthen the immune system Signup and view all the answers

Why is it necessary to cut curds into smaller pieces?

To allow whey to be released more effectively Signup and view all the answers

Which of the following bacteria is commonly found in probiotic yoghurt?

Lactobacillus Signup and view all the answers

What is the function of salt in cheese making?

To enhance flavor and act as a preservative Signup and view all the answers

What type of food ingredient are probiotics classified as?

Live microbial food ingredients Signup and view all the answers

What is the role of L.Acidophilus in the food products mentioned?

To provide live cultures in yoghurt Signup and view all the answers

What is whey in the context of cheese production?

A by-product of cheese production Signup and view all the answers

Which of the following is NOT a characteristic of probiotics mentioned?

They are only beneficial for children Signup and view all the answers

What is the primary product of lactic acid fermentation?

Lactate Signup and view all the answers

Which enzyme is not involved in lactic acid fermentation?

Alcohol dehydrogenase Signup and view all the answers

What type of fermentation is used in the production of beer and wine?

Alcoholic fermentation Signup and view all the answers

Which of the following is a common use of bacteria in food production?

Producing yogurt Signup and view all the answers

Which microorganism is primarily responsible for producing ethanol during fermentation?

Yeast Signup and view all the answers

Which fermentation process does NOT produce carbon dioxide?

Lactic acid fermentation Signup and view all the answers

What is the direct result of glycolysis in both lactic acid and alcoholic fermentation?

2 Pyruvate molecules Signup and view all the answers

Which of the following products results from alcoholic fermentation?

Carbon dioxide Signup and view all the answers

What is the purpose of pasteurising milk in yoghurt processing?

To kill harmful bacteria Signup and view all the answers

At what temperature is milk cooled to promote the growth of the starter culture in yoghurt production?

40-43ºC Signup and view all the answers

What do the lactic acid bacteria do to the lactose in the milk during fermentation?

They convert it into lactic acid Signup and view all the answers

Which type of yoghurt involves adding fruit at the bottom of the cup before fermentation?

Set yoghurt Signup and view all the answers

What is a key characteristic of stirred yoghurt compared to set yoghurt?

It is fermented in bulk and then stirred Signup and view all the answers

What role does acetaldehyde play in plain yoghurt?

It gives the yoghurt its characteristic flavor Signup and view all the answers

What is the main difference between drinkable yoghurt and stirred yoghurt?

Drinkable yoghurt is homogenised for a smooth texture Signup and view all the answers

What is the primary purpose of homogenisation in yoghurt processing?

To blend the pasteurised milk for consistency Signup and view all the answers

Study Notes

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

Time	Fermentation Product	Place
Antiquity	Bread, vinegar, soy sauce, wine, beer	Assyria, Caucasia, Mesopotamia, Sumer
7000 BC	Beer and wine
6000 BC	Winemaking	Georgia
5000 BC	Wine jars	Zagros Mountains, Iran
3000 BC	Fermented beverages, beer, and fermented milk products	Babylon
2600 BC	Fermented milk products	Babylon
1000 BC	Bread, soy sauce, miso, and cheese	Egypt, China, Asia
600 BC	Cheese	Asia
500 BC	Meat preservation
100 BC	Bread	Ancient Rome
1700's	Vinegar from fruit pomace
1800's	Yeast-induced fermentation, bacteria-produce lactic acid	Erxleben, Germany; Louis Pasteur, France
End of 1800s	Yeast+grape juice → wine/beginning of food fermentation
	Composting

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.

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Description

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!