Chapter 11 Flashcards
1
Q
yeasts
A
- unicellular fungi that reproduce by budding
- have no taxonomic standing, simply denotes a growth form
2
Q
Dimorphic species of yeast
A
- shift from filamentous to yeast under certain environmental conditions (e.g. some jelly fungi, some human pathogens, some mushrooms, etc.)
3
Q
What are Saccharomycetales
A
- “True yeasts” that undergo fermentation
4
Q
What is fermentation?
A
- sugar + yeast= CO2, energy and alcohol
- Anaerobic respiration of food by microorganisms
- Release of energy from substrate/sugars in the absence of oxygen
5
Q
What are the products of fermentation?
A
- Carbon dioxide, energy, and alcohol or various organic acids
6
Q
What are the age old applications of yeast?
A
- Bread
- Wine/ Beer/ Spirits
- Cheese and Yogurt
7
Q
What did Louis Pasteur hypothesize?
A
- that bacteria spoils wine
- Suggested that wine be heated to kill bacteria
- Hence: pasteurization of milk
8
Q
Fermentation pros
A
- Extended shelf life (ex. Cheese)
- Eases Digestion (ex. Wild rice)
- New [better] flavors (ex. Chocolate)
9
Q
Fermentation cons
A
- Can be unpredictable (i.e. bad bacteria win the battle)
- New [worse] flavours (ex. Mouldy bread)
10
Q
Types of Fermentation
A
- Yeast fermentation
- Mold and enzyme fermentation
- Bacterial fermentation
11
Q
Yeast fermentation
A
- Metabolic process that converts sugar to acids, gases, and/or alcohol
- it is anaerobic and takes place in the absence of oxygen
12
Q
What is the formula for baking with yeast?
A
- flour + sugar + water + yeast = ethyl alcohol +CO2
- best temperature is at 27’C (warm)
- too much salt will ruin the process
13
Q
What is the earliest processed foods?
A
- bread
14
Q
Baking with yeast is a $__________ industry in the US.
A
- 16 billion dollar
15
Q
Saccharomyces cerevisiae
A
- bakers yeast
16
Q
Properties and characteristics for bread making
A
- Gassing power
- Flavor development
- Stable to drying
- Stable during storage
- Easy to dispense
- Ethanol
- Cryotolerant
17
Q
How to make wine?
A
- fermentation of grapes that dates back to the Middle East
18
Q
When does fermentation of grapes begin?
A
- after the grapes are crushed and yeast is added to it, once the yeast begins to digest the sugars present in the grape juice
19
Q
Botrytis cinerea
A
- Latin for “grapes like ashes”
- bunching of the fungal spores and “ashes” the grayish color of the spore mass
- aka Noble Rot
20
Q
Where is Noble Rot found?
A
- This species is ubiquitous
- it is found virtually everywhere plants are grown.
21
Q
How does Noble Rot affect grapes?
A
- fungus causes grapes to lose water thus increase sugars, impart flavor, increase etoh = noble rot!
- more expensive wines
22
Q
What is sake made from?
A
- made from rice, rather than from grapes, barley or corn
23
Q
How is sake made?
A
- First koji mold such as Aspergillus oryzae, is used to convert starch in the rice to sugars
- Then fermented by other microorganisms, such as yeast (Saccharomyces) and lactic acid bacteria.
24
Q
What is beer?
A
- An alcoholic beverage produced by the fermentation of sugar-rich extracts derived from cereal grains or other starchy materials.
25
How long has beer been made?
- since the dawn of civilization, where grain was grown beer was made
26
The first places to make beer were
1. Sumaria
2. Egypt
3. India
4. China
27
What does beer resemble?
- liquid bread
28
How did ancient brewers domesticate yeast?
- Selected yeast that made good beer
| - Found it was important to make beers
29
Antonie van Leeuwenhoek
- Observed yeast in beer
30
Cagniard Latour
- found that the microbe is responsible for alcoholic fermentation
31
Justus von Liebig and Friedrich Wohler
- found that alcohol is produced by a chemical process in which dead and decaying yeast participated.
- Satired Latour’s theory in Annalen der Chemie
32
Latour’s theory in Annalen der Chemie
- was that a small animal which sips sugar through its snout, and excretes alcohol from its gut and carbonic acid from its urinary organ.
33
Louis Pasteur
- Discovered yeast was responsible for alcoholic fermentation
34
Emil Christian Hansen
- Developed pure culture technique
| - Isolated pure cultures of brewing yeasts
35
Two types of brewing yeasts
1. Top-fermenting (ale yeast, weiss yeast)
| 2. Bottom-fermenting (lager yeast)
36
Ingredients in beer
- Malted barley, cereal adjunct, hops, water, yeast
37
Hops
- Gives the spice of the beer, a flavoring agent that provides aroma and bitterness
- Flower (cone) of vine-growing plant, can come from Humulus lupulus, lupulin or Canabaceae
38
Mold and Enzyme Fermentation
- Break down cellulose thus grains easier to chew
| - Add flavor and texture to cheeses (ex. blue)
39
Bacterial Fermentation
1. Lactic Acid Bacteria (pickles, sauerkraut) 2. Acetic Acid Bacteria (vinegar)
3. Carbon Dioxide Bacteria (Edam, Gouda, Swiss)
4. Proteolytic Bacteria (cocoa, chocolate)
