Chapter 17: Fermentation: Desirable Effects of Microorganisms Flashcards
What is Microbiology?
Is the study of living organisms too small to be seen by the unaided human eye
What are Microorganisms?
Organisms that are only visible through a microscope are called microorganisms
What do microorganisms do?
The multiply rapidly, and transfer easily from one surface to another (Cross-contamination)
What are some positive uses for Microorganisms?
Microorganisms that have a positive use in foods are bacteria, yeasts and molds
Bacteria are part of what Kingdom?
Bacteria are members of the Monera kingdom
Yeasts and molds are part of what Kingdom?
Yeasta and molds are members of the Fungi kingdom
Microorganisms depend on what to grow?
Microorganisms depend on outside sources of food to grow and multiply
What is Bacteria?
Bacteria are single-celled organisms that multiply through cell division
What is the Cytoplasm?
Bacteria cells have no nucleus and are filled with a gelatinous liquid called Cytoplasm
What are some characteristics of Bacteria?
- Up to 3 micrometerslong
2. Classified by shape, cell wall structure, and oxygen needs
Bacteria have 3 basic shapes, what are they?
- Bacilli: a rod shape
- Cocci: have a spherical shape
- Spirilla: have a spiral shape
Bacteria have 2 types of cell wall structures, how re they identified?
They are identified by the ability to be stained by a crystal violet dye, called Gram’s stain
What are the 2 types of cell wall structures?
- Gram-positive bacteria turn violet
2. Gram-negative bacteria turn red
Bacteria can be categorized by oxygen needs?
- Aerobic: bacteria must have oxygen to function
- Anaerobic bacteria function best in an oxygen-free environment
- Facultative: bacteria can function in either type of environment
Aerobic bacteria does what to cabbage?
Aerobic bacteria spoil cabbage, but
- submerging cabbage in salt water does not allow aerobic bacteria to grow
- the anaerobic bacteria can multiply and develop the flavour and texture of sauerkraut
Bacterial growth rates depend on what?
Bacterial growth rates depend on pH, air, temperature and nutrients
What is Fungus?
A fungus is a plant that lacks chlorophyll
What are some characteristics of Fungi?
- are not single-celled
- Have a nucleus in their cells
- Are widely distributed in nature and help organic matter decay
What are some examples of Fungi?
mushrooms, molds, mildew, rust, and yeast
How are Fungi classified?
Fungi are classified by their structure and reproduction methods
What are Hyphae?
Basic structures of most fungi is made up of filaments or tubes called hyphae
What are some characteristics of Hyphae?
- Have elongated cells or chains of cells that absorb nutrients from the environment
- Intertwine and form a branched network called a Mycelium
How does Mycelium reproduce?
Mycelium reproduces by creating spores, the reproductive cells of fungi
What are some characteristics of Spores?
- Spores develop in a sac or balloon-like structure that explodes when full
- Spores are microscopic and resistant to harsh environments
What are Molds?
Molds are fungi that form a mycelium structure with a fuzzy appearance
- many produce antibiotic that kill bacteria likely to be growing in the same area
What are Yeasts?
Yeasts are fungi with a single-celled structure that produce alcohol and carbon dioxide
- They form mycelium structures on soil or plants, but reproduce in animals by budding
What are some common Characteristics of Microorganisms?
- Grow rapidly and are good sources of edible for animals
- Can enhance or add to the nutritional value of food
- Can enter a dormant or inactive state to protect themselves form a harsh environment
- Reproduce when the environment supports growth needs
What is a Pure Culture?
A pure culture is a large volume of one type of microbe grown purposely
What are microorganisms used for at Food processing plants?
At food processing plants, large volumes of microorganisms are used in the development of such foods as pickles, cheese, and beverages
What are Starter Cultures?
Starter cultures refer to pure cultures of microorganisms that are added to foods begin a fermentation
What are Microbial Enzymes?
Enzymes produced by microorganisms are the source of most changes in food products
Why do microorganisms secret digestive enzymes?
Microorganisms excrete digestive enzymes to break down large macromolecules for transport through the microbial cell wall
- Microorganisms can absorb the fragments and use them for energy
How can Microorganisms be classified?
Microorganisms can be classified by the organic molecules they use as a food source
What are Proteolytic Microorganisms?
Microorganisms release proteases that change proteins into amino acids and are used to clot milk, tenderize meat and remove pulp from cacao beans
What are Lipolytic Microorganisms?
Microorganisms produced enzymes, that digestive fats and are used to flavour cheese, remove egg yolk and clean up oil spills
Microorganisms are classified by 2 Latin names, what are they?
- Genus name:
- is always capitalized
- indicated a family of organisms that have similar characteristics - Species name:
- is never capitalized
- identifies the type of microbe within the family
An example of Scientific Names for Microorganisms?
Lactobacillus acidophilus:
- Lacto refers to milk
- Bacillus refers to bacteria with a rod shape
- Acidophilus indicates bacteria that give off acid
What is Lactobacillus acidophilus ?
a rod-shaped bacteria that lives in or feeds on milk and produces an acid
Why do microorganisms need an energy supply?
because microorganisms are composed of carbon, oxygen, nitrogen and hydrogen they need a food supply containing all 4 chemicals
The type or amount of energy supply needed for microorganisms, depends on what?
The energy supply needed on the enzyme systems the organisms can make
What else do Microorganisms need other than an energy supply?
Microorganisms also need minerals and vitamins to aid with enzyme activity
Why do microorganisms need water?
Some microorganisms can remain alive, but dormant, in dried conditions
- A safe water activity (Aw) for most food storage is considered 0.70 or lower
How can water activity be lowered?
Water activity can be lowered by removing water, adding solutes or by freezing
Microorganism grow at certain what?
Microorganisms grow at certain pH values
- Each microbe has a preferred range, but can survive at pH levels above and below it
Why do Microorganisms prefer a moderate temperature?
- Freezing slows enzyme activity and cell reproduction, while heating can kill microorganisms
- Most microorganisms die at 5-12C above the temperature for maximum growth
- Food processors balance temperatures needed to kill microorganisms against effect heating has on food quality and production costs
What is Fermentation?
is an enzymatically controlled change in a food product caused by the action of microorganisms
Changes in Fermentation results from what?
- Digestive enzymes released by the microorganisms
2. The release of by-products, such as carbon dioxide, acetic and lactic acids, and ethanol
The primary product of a microbial reaction is what?
Is energy
- By-products can change the colour, texture, flavour, aroma, and pH of a food
When does Fermentation occur?
Fermentation occurs when nutrients broken down by digestive enzymes are absorbed by microorganism for growth and energy
What is Yeast Fermentation?
Yeast is needed in all yeasts breads, alcoholic beverages, and vinegars
What is Saccharomyces cerevisiae?
it is often used
- sugar is its main source of energy
- It can utilize on honey, molasses, or corn syrup
How is Yeast affected by steps in the bread making process?
- Warm liquid activates yeast
- Mixing distributes yeast evenly
- Kneading the dough develops the gluten
- Proofing allows the yeasts to produce enzymes that break down sugars, releasing alcohol and carbon dioxide
What happens in the bread-making process?
- carbon-dioxide becomes trapped in pockets throughout the dough, gluten stretches and dough rises
- The dough continues to rise during baking and a crust forms
What do Bread products contain?
The contain flour, yeast, salt, and water
What is wine?
Wine is the fermented juice of plant products such as grapes, honey, various fruits and dandelions
What is the process of wine fermentation?
- Sulfur dioxide (SO2) or potassium metabisulfite is added to inhibit unwanted microbe growth
- Juices are held in anaerobic conditions for up to 4 weeks in oak barrels or stainless steel tanks
When is Wine Fermentation complete?
Wine fermentation is complete when bubbling from CO2 production stops
- Wine is then aged in barrels or vats to slowly develop the characteristic flavour
Yeast is used in the fermentation of other alcoholic beverages like..?
- Beers is made from corn
- Bourbon is made from corn
- Rum is made from sugar cane or molasses
- Brandy is distilled wine or fermented fruit juice
- Liqueurs have brandy base with sugars and flavouring added
What is Lactic acid fermentation?
- Is one of 3 main types of bacterial fermentation
- Refers to the many fermented foods-vegetables, meats and dairy products produced by bacteria whose by-products is lactic acid
- Produces the other by-products of acetic acid, formic acid, and carbon dioxide
What is Sauerkraut?
Sauerkraut results from the lactic acid bacterial fermentation of cabbage submerged in brine (a salt and water solution)
What does the Brine do to the cabbage?
The salt controls water activity and pulls water with dissolved sugar and nutrients to the surface
- Bacteria utilize the sugar and release carbon dioxide and lactic acid into the brine
How are cucumbers turned into pickles?
Heating them in a spiced vinegar solution, refrigerating in an acid brine, or fermenting them with lactic acid bacteria
Commercial pickling involves what?
- Washing the cucumbers in chlorine solution
2. Placing them in brine with a pure culture of Lactobacillus (starter culture)
Other foods that can be pickled are..?
Vegetables such as watermelon rinds, beets, cauliflower, okra and onions and even eggs
Lactic Acid fermentation is used to make and dry semidry sausages by.. (Bacterial Fermentation: Meats)?
- Increased acid tenderizes the meat and adds a tart flavour
- Fermentation, smoking and drying prevent spoilage
- Sugar provides energy for fermentation and lactic acid production and spices and salt add desired flavour
Bacterial Fermentation: Cheese occurs by?
Milk is pasteurized, then rennin and lactic acid bacteria are added to form curds
- Curds are cut into small cubes and heated to help the whey separate from them
- Whey is drained off and collected for use as an additive in other processed foods
- Curds are rinsed and salted
What are curds?
- mixed with cream to make cottage cheese
2. Put in presses to squeeze out excess moisture for making aged cheese
What happens to cheese during aging or ripening?
During aging or ripening, cheeses wrapped with wax are placed in curing rooms
What is responsible for the characteristic flavour of cheeses?
Different bacteria or molds are responsible for the characteristic flavours of cheeses
What does the Sharpness of Cheese mean?
the sharpness of cheese refers to the strength of flavour and aroma
- Sharpness develops as cheese ages
Cheese that age longer tend to do what?
- Have firmer consistency
- Have more crumbly textures
- Melt into sauces more readily
Molds create what a wide range of what?
Molds create a wide range of by-products
-antibiotics, flavour compounds and enzymes
Fermented foods are often used in Asian Cuisine such as..?
- Soy sauce, a fermented mix of soybeans and wheat
- Tempeh, a soybean cake of cooked, mashed soybeans pressed into blocks, inoculated with soybeans pressed into blocks, inoculated with Rhizopus molds, and wrapped in banana leaves
What is Two-step Fermentation?
uses bacteria as well as fungi to produce the product
- for cheese, lactic acid bacteria is needed to form the product, then other microorganisms develop the flavours and textures
- For sourdough bread, lactic acid bacteria ferments the product, and then a yeast starter proceeds to ferment the product
Acetic Acid fermentation follows yeast fermentation by?
- yeast release alcohol as they break down sugars, then acetic acid fermentation begins
- Acetobacter bacteria use the alcohol as energy and release acetic acid
- Vinegar is produced by acetic acid fermentation
Acetic Acid Fermentation produces?
Produces candied citron from citron lemons for use in baked goods
- Turns cacao beans into chocolate
Microorganisms help preserve some foods by?
Fermented foods tend to have a low pH and can be stored for longer periods (especially at refrigerated temperatures)
Fermentation offers a wider range of what?
Fermentation offers a wider range of food options
Nutritional Changes in Fermented foods vary depending on what?
- Microorganisms used
- Other ingredients added
- Impact of fermentation on bioavailability
In Cheese what is of higher concentration than in milk?
Fat and Calcium concentrations are higher in cheese than in milk
What does Pickling do?
Pickling adds salt through the brine, which increases the sodium content
