Yeast breads Flashcards
1
Q
5 key ingredients yeast bread
A
- flour
- water
- salt
- yeast
- optional ingredients: shortening/fat, milk- or other liquid, sugar, eggs
2
Q
3 categories of leaveners
A
- chemical (bakin soda, bakin powder)
- physical/mechanical
- air (egg whites, creaming sugar + butter…)
- steam (liquids, eggs) - biological (yeast, bacteria)
3
Q
yeast: what is produce + 3 basic functions
A
- produce zymase, and enzyme that ferment sugars:
glucose = ethanol+ CO2+ other by-product (which are flavor compunds + help develop the dough) - 3 basic functions:
1. CO2 leavens the dough
2. variety of by products contribute to bread flavor
3. fermentation process develops the dough
4
Q
what is saccharomyces cerevisiae + 3 qualities that are important for baking
A
- baker’s yeast used in breadmaking
- 3 good qualities:
1. good CO2 production
2. development of desirable flavour
3. adequate keeping qualities
5
Q
3 types of yeast you can buy
A
- compressed yeast: fresh, requires refrigeration unless it is frozen (very perishable)
- active dry yeast (dehydrated, rehydrated in water at 43-46degree :
- high temp= inactivated
- low temp= leaching of cells into liquid, which soften bread dough (gluthaonine is leaked) - instant yeast: added directly to dry ingredients
6
Q
3 things to consider when you do yeast bread (yeast activity)
A
- sugar, moisture and temperature
1. temperature
optimal temperature for dough fermentation : 30-35 degree
2. sugar - high osmotic pressure (too much salt/sugar) inhibits the activity (because it keeps the water out and you need to rehydrate the yeast)
- must have enough food (sugar) to permit growth of microorganisms
3. moisture
hydration activates dormant yeast - pH sligtly acidic (4-6) is optimal
7
Q
reaction to produce yeast (substrate, enzymes)
A
- sucrose, starch = glucose = ethanol + CO2 (so yeast needs glucose)
- subsrate (sucrose, starch)
- added to the dough (sucrose)
- naturally in flour (1-2% sucrose; starch) - enzymes hydrolyse longer chains
- flour amylase
- a-amylase catalyzes: starch = random , smaller pieces
- b-amylase catalyzes: starch= maltose - yeast
- maltase catalyzes: maltose= glucose+ glucose
- invertase catalyze: sucrose= glucose + fructose
* * there are a multide of enzymes in yeast: the smaller are the carbohydrates, the bigger will be the flavour
8
Q
role of sugar + 3 consequences of larger amount
A
- small amount added (less than 8% of weight of flour):
provide a readily available substrate for immediate gas production by yeast - larger amount:
1. inhibits yeast activity
2. tenderized by interfering with gluten development (because gluten needs water so sugar will compete with it)
3. browning due to Maillard reaction
9
Q
what wheat flour provides
A
it provides the proteins (glutenin and gliadin) from which gluten is developped during hydration and mixing
* hat gives that nice structure, does not crumble.. gluten has a lot of great things for that
10
Q
flour: what is it, sources (7) and non-cereal sources (7)
A
- fine powder derived from endosperm of seeds or from other starchy food
- main source = wheat, but also come from oat, rye, barley, rice, corn, triticale (wheat and rye hybrid)
- non-cereal sources: potato, soy, chickpea, taro, cattail,arrowroot, coconut
** basis for all bakek good like yeast and quick breads
11
Q
7 types of wheat flours
A
- Whole wheat *bran, germ, endosperm
- White (endosperm only)
- Gluten flour (milled in a way to retain gluten)
- All-purpose (gluten potential= in between cake and bread)
- Bread flour (high gluten)
- Pastry and cake (lower protein)
- Durum (semolina= high in proteins but not that much in glucose)
12
Q
proteins in flours: 5 solubles, one insoluble in wheat
A
- Insoluble proteins in wheat: Gliadin and glutenin - Soluble flour proteins (in dilute salt solutions) 1. Albumins 2. Globulins 3. Glycoproteins 4. Nucleoproteins 5. Lipid-protein complexes 6. Enzymes: amylases and proteases
** quantity and quality of proteins in flour affect baking quality
13
Q
3 types of flour with 0% gluten potential + order of flour with less to the most gluten potential
A
- rice, quinoa, buckwheat (0%)
- barley (3-4%)
- rye (6%)
- cake flour (6-8%)
- pastry flour (7-9%)
- the most: all type of wheat flours and alsor bread, yeast flour)
14
Q
characteristics of gliadin (3) and glutenin (5) which represent 85% of the wheat flour protein
A
- gliadin:
1. Hydropholic, single spherical polypeptide chains
2. Fold onto themselves, bonding weakly with each other
3. Fluid and sticky
glutenin:
- Hydrophobic, longer than gliadin
- Largest component of gluten complex
- Bond more strongly with each other
- Form strong S-S bonds at the end of teh chains
- Contributes to elastic properties of flour dough
15
Q
gluten controls what + forms what
A
- it control the rheological (flow) properties of dough: elasticity and plasticity (stability)
- it forms a continuous, 3-dimensional network of hydrated proteins in which starch granules are embedded
16
Q
2 steps of gluten formation
A
** need moisture and manipuation
- Hydration
- Distributes air bubbles
- Gliadin and glutenin absorb 2x their weight in water and become gluten
- Other proteins (albumin and globulin) become main part of dough
- Result- a complex of gluten with water in the spaces - Kneading (it will unfolds and align the long initially gluten molecules crosslinked by S-S. Shhets of gluten gives dough a smooth fine texture)
- Used extensively in bread making
- Working dough into elastic mass by pushing, streching, folding
- Expand gluten strands
- Distributes yeast
- Warms doughs; increases fermentation
Helps distribution of CO2
** can replace the step of kneading only by letting the dough rests
17
Q
what do sugar and fat to gluten
A
- sugar: binds water- prevent gluten formation
- fats coat gluten molecules; prevents clumping
18
Q
what happens to the dough when we put under cold water
A
water soluble proteins and starch freed: only gluten remains
cake has less gluten then all-purpose and then bread
19
Q
gluten = ?
and 4 cereal prolamins toxic in ciliac disease
A
- gluten = general name given to the storage proteins (prolamins or peptide fractions) present in wheat, rye or barley
- cereal prolamins toxic in CD:
1. gliadin in wheat
2. secalin in rye
3. hordein in barley
4. (avenin in oats?)
20
Q
7 points between gluten and ciliac disease (symptoms, risks,..)
A
- Immune system reaction to gluten
- Affects GI tracts- malabsorption
- Genetic transmission
- Estimated prevalence in Canada: 1:133
- Symptoms: abdominal bloating, diarrhea, fatigue, weigh loss..
- Non-gluten forming grains include: millet, teff and rice
- Oats apperas to be safe but use limited by potential contamination with gluten
21
Q
7 gluten substitutes
A
- Xantham gum (Polysaccharide very common: stabilizers, prevent ingredients from separating
Helps to give the dough stickiness to help trap CO2, it comes from a strain bacteria)- Guar gym (seed of a plant, create a gel-like structure to trap CO2)
- Psyllium seed husk
- Chia seeds (high in soluble fibers)
- Flax seed meal
- Gelatin
- Agar agar
22
Q
4 characteristics starch
A
- Strengthens through gelatinization
- Dextrins contribute to colour ans sweetness
- Contributes to crumb
- Texture of baked products interior
1. FINE= small, densely packed air cells- COARSE= large, irregular holes
23
Q
liquid (milk = most popular) its role
A
- Liquid in bread is necessary to hydrate proteins and starch and for gluten development
- Milk most common liquid used in breadmaking:
1. Adds nutrients
2. Gives a finer texture
3. Improves crust and crum color and flavor
4. Whey softens the dough and decrease volume, therefore molk must be heated before using to denature whey pro
- Milk most common liquid used in breadmaking:
24
Q
role of salt
A
- Small amount (less than 2% of weight of flour)
Roles:- Improves taste of bread
- Stabilizes yeast fermentation (slows its activity)
- Changes rheological properties of the dough
- Has a firming effect on gluten:
- Increases water holding capacity of dough
- Cl ions help gluten proteins stick together
25
fat and eggs- optionnal
- Small amount (less than 3% of weight of flour)
1. Increases loaf volume
2. Gives a more uniform and tender crumb
3. Improves slicing properties (less crumbly)
Enhances keeping quality (decreases staling)
eggs= optionnal
26
6 additives/dough conditioners
1. Calcium and ammonium salts
- Supply nutrient need of yeast cells
- Provide a slight buffering action (keep the ph at a cetain level to optimize texture of the dough)
- Ca has a firming effect on gluten
2. Oxidizing agents (K et Ca bromates and iodates)
- Set the strcuture of the protein network in the dough (help strenghten the gluten)
3. Surface active agents
- Dough conditioners (polyethylene monostearate and polysorbate 60)
(strengthen the gluten structure and improve its gas-retaining ability)
Dough softeners (monoglycerides, sodium stearyl-2 lactate)
(increase the shelf life of bread by retarding firming of crust)
4. Enzymes (proteases)
- Improve dough handling and extensibility
5. Antimolding agents (sodium and calicum propionate)
- Inhibit growth of spore forming organisms
6. Fibers (from cellulose or bran)
Antioxidants (BHA,BHT)
27
role of corn syrup, malt extract and vinegar in bread
Add these things to preserve bread for a long time, give a better texture and flavor
- Corn syrup: help to make the bread fluffy (texture) and volume
- Malt extract: give nice flavor, some browning
Vinegar: make it more delicious, add flavor and texture
28
5 steps of breadmaking
1. During mixing and kneading: numerous cells of air are incorporated and development of the gluten structure in dough
2. During fermentation/rising: decrease in pH (production of CO2 and lactic acid)
3. After fermentation: gas vacuoles are formed in the mixture
4. After dough has risen: punched down to permit a uniform distribution of gas cells throughput the dough
5. After punching down: proofing allows dough to rise in the pan after fermentation and before baking
29
what happens during fermentation
As the yeast ferments, the dough will double in size as CO2 is produced by the yeast and as enzyme and pH changes take effect
30
why doing punching down (put le poing in the dough)
allows excess gas to escape and redistribute the ingredients
31
3 things happen during baking
1. Within the first few minutes
- Yeast activity stimulated - CO2 (until inactivated at 60degree)
- Volume increases markedly= oven spring
2. Adequate volume is dependent until the ability of the gluten mass to:
- Expand
- Produce thin cell walls that hold gas up to the point of setting the structure
3. Brown color of crust
- Maillard reaction
Caramelization of sugar
32
6 changes in baking
1. Changes apperance, texture, favour, aroma
2. Yeast killed
3. Protein coagulates
4. Starch swells and gelatinizes
5. Fat melts
6. Crumb development
33
oven spring and after baking
- Oven spring: the quick expansion of dough during the first 10 minutes of baking, caused by expanding gases
- afterbaking: - Much of the starch is gelatinized
Gas vacuoles are dispersed throughout the strcture
34
bread flavor and staling
1. Characteristic flavor of freshly baked bread related to volatile and nonvolatile subtsnaces produced during fermentation (alcools, organic acids, esters and various carbonyl compunds)
- Begins to change within a matter of hours after baking (staling begins!)
2. Staling
- Involves mainly the amylopectin fraction of starch which undergoes retrogradation (crystallization)
- Causes:
1. Change in taste and aroma
Increased hardness, opacity and crumbliness of crumb
35
how bread stales
- Fresh baked: immediately out of the oven, both amylose (straoght chains) and amylopectin (branched structures) are swollen and randomly oriented
- Fresh bread: during cooling (1 hr), the amylose molecules begin to align and crystallize
Stale bread: during staling (several days), amylopectin realigns and reforms crystallites
36
varieties of yeast brea
- The simplest yeast bread is made from: flour, water and yeast
- This basic formula has evolved into more complicated varieties
Varieties thta include loaf breads:
1. White
2. Whole-wheat
3. Sourdough (use yeast and particularly bacteria to create lactic acid that create particular flavor)
Malt bread
Other varieties
1. Rolls
2. Pita bread
3. Bagels
4. English muffins
5. Pizza crust
6. Raised doughnuts
7. Specialty breads
