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Food Science Unit 4-2 Leavening Agents and Fermentation
Transcript of Food Science Unit 4-2 Leavening Agents and Fermentation
Leavening is the key to fluffy baked goods
Heat is added & bubbles cause the mixture to inflate.
Air, steam, and carbon dioxide are all used to leaven bread
Carbon dioxide requires a biological or chemical process
Steam and air occur naturally
Air is added by:
beating fat with sugar
Not usually main leavening agent.
Can you name a product we have made that does have air as the main leavening agent?
All baked goods include liquids
When heated the liquids produce steam
Batter expands around steam, with eggs and gluten (a protein) providing structure.
Baking in a hot oven (204 degrees C) is required to coagulate the protein
By a chemical process From yeast
Baking products (usually baking soda or baking powder)
react with other ingredients to cause a chemical reaction with carbon dioxide as the byproduct.
Yeast is involved in a biological enzymatic reaction that produces carbon dioxide.
Baking Soda vs. Baking Powder
2NaHCO3 CO2 + Na2CO3 + H2O
Requires an acid to prevent sodium carbonate from forming
Results in bad taste & yellow color
Acid examples: buttermilk, lemon juice, honey, fruit juice, or cream of tatar
Leavening compound that contains baking soda, dry acids, and starch
Single Acting or Double Acting
Carbon dioxide is produced as soon as liquid is added
Contains two acids; one reacts with heat, another with cold liquids. Some gas is produced when liquid is added, however, the rest of the carbon dioxide is produced in the oven when the batter is heated.
Lets discuss similarities
Baking powder varies in amount of carbon dioxide released
Excess amounts cause walls of mixture to stretch, resulting in them breaking or collapsing
Too little causes a compact product
Must be stored air tight. Why?
carbon dioxide is produced by decomposition
Used in crackers & certain cookies because ammonia gas changes flavor of the product.
Thin crackers (e.g. surface area), allow gas to escape
Produces carbon dioxide through fermentation
an anaerobic biological reaction that splits sugar (glucose) into simpler substances (alcohol, acids) and releases carbon dioxide.
Yeast = killed off during baking, stopping process
Evaporates during baking
causes product to rise
Making leavening products
batters vs doughs
Pour batters: equal ratio of flour to liquid
steam is leavening agent
Drop Batters: 2 parts flour to 1 part liquid
Baking powder & steam are leavening agents
Soft dough: 3 parts flour to 1 part liquid
Need excess mixing to develop gluten
Stiff dough: 6-8 parts flour to 1 part liquid
Yeast bread is a soft dough
Granular or compressed forms
Stable for long time at room temp
Contains more water
Must be refrigerated or frozen
Provides starch & protein (becomes gluten)
Strong gluten quality produces high volume & fine texture
Gluten traps starch when mixed
As bread bakes starch surrounds gas cells and forms solid structure.
Usually water or milk
Milk causes bread to stay fresher
Liquid is a medium that dissolves other ingredients & transports them to yeast
Steam from liquid combines with CO2 from yeast to help bread expand & rise.
Prevents enzymes from breaking down protein
dough is sticky & hard to work with
Salt Carbon Dioxide
Makes bread tender
Helps crust brown
Makes bread richer in texture
No time to rise
Steam & CO2 (from where?) to rise
All have flour, liquid, salt
May have sugar, fat, eggs, other ingredients
Mixing is important!
Over mixing too much gluten
Tunnels in final product
Use any of the leavening agents
Shortened cakes: LA & shortening
Pound cake: LA= air, steam
Unshortened cake (sponge, chiffon, angel food) : air beaten into eggs for leavening.
1. What are the three main leavens in baked goods?
2. How do each of the two natural leavens work?
3. What would happen if you left out the lemon juice in a recipe that calls for 2 teaspoons of baking powder?
4. Describe how yeast produces carbon dioxide for leavening.
Fermentation in History
In use since before recorded history
Alcohol is from fermenting fruit juice
Prevented bacteria from turning wine to vinegar
process of using heat treatment to destroy bacteria
Extends shelf life of food
Makes certain foods more enjoyable
Certain foods become more useable
All organisms do
Glucose is broken apart and resulting energy is harnessed.
An aerobic process: oxygen must be present for the entire cellular respiration process to occur.
The process can not be completed without oxygen
Fermentation results when respiration is performed in an
anaerobic environment (environment lacks oxygen)
carbon dioxide alcohol organic acids
Yeast, bacteria, mold all perform fermentation
We will be discussing micro organisms a great deal
lets review binomial nomenclature
Organisms are named and grouped with like organisms
Names are in latin
Must be italicized or underlined
First letter of Genus name is capitalized
First letter of Species name is lowercase
- Kingdom Archaebacteria
- live in extreme environments
- glacers, hot springs, salt lakes
- Kingdom Eubacteria
- common bacteria
Both are prokaryotic - mean they lack a nucleus
Pairs of two
Lactic Acid bacteria:
pickles, sauerkraut, others
Acetic Acid bacteria:
break down protein; used in cocoa, chocolate found in candy and beverages
Indigenous: found naturally or as part of the environment
Cultured: added to the product for favorable results
Lactic Acid Bacteria
Reaction is occuring in your muscle cells!
Also used to make sour cream, cottage cheese, dill pickles, olives, saueurkraut, and vanilla
Glucose Lactic Acid + Energy
During lactic acid fermentation, pH lowers
Fermentation stops when there is no glucose left
Bacteria die (making food edible) at pH of 4.5
Pickles use a brine:
a water and salt mixture that has high levels of salt
Vegetable remains in brine for several week
Fermentation of lactic-acid bacteria continues to lower pH
Changes to food's appearance & texture
Fermentation doesn't not occur
Vegetable is placed in brine for several hours
Then drained and placed in boiling vinegar and spices to kill bacteria and give flavor.
Fermented by lactic-acid bacteria
Salt is mixed with cabbage, bacteria already present on cabbage makes sauerkraut.
1. Cabbage is rinsed to promote growth of lactic-acid bacteria & destroy other bacteria.
2. Salt releases fluids that are used as growth medium. Salt pulls water and sugar from cabbage, and sugar provides food for lactic-acid bacteria. This is what gives sauerkraut it's sour taste.
3. Bacteria produces enough lactic acid to lower pH to 3.0, nothing survives past pH of 4.6 other than fermenting bacteria.
Acetic Acid Bacteria
1. Sugar from fruit is fermented with yeast into ethyl alcohol.
2. Acetic-acid attack bacteria.
3. Oxidation occurs when alcohol combines with oxygen, producing acetic acid.
Yeast converts glucose into ethyl alcohol and carbon dioxide.
Can only ferment maltose, sucrose, and fructose.
Goal is to create best food product:
27 degrees C: too hot and yeast dies, too cold and no fermentation occurs, too much change causes no CO2 to be produced.
Too much salt slows fermentation & release of CO2. Too little weakens gluten, breaking cells.
Mold and Enzyme Fermentation
Humans have no enzymes to metabolize cellulose
Molds can break down cellulose, then the body can utilize nutrients.
Wild rice, oats, nuts, seeds, aged cheeses, and soy sauce are due to mold fermentation.
Fermented Beverages & food
Design an advertising campaign for a new food or beverage. The campaign needs to describe how the product is made. Come up with a visual to show the class as well as a catchy jingle or slogan for your campaign. Each group must research a different topic. You will present starting January 24.
Possible options: coffee, tea, bread, root beer, chocolate, sausages, salami, cheeses, bologna, etc.