workshop 7

Question 1

role of yeast + 4 different types

Answer 1

• yeast= leavening agent in bread by producing the enzyme zymase which converts glucose + fructose = CO2, alcohol and other flavor components
• yeast produces also other chemical thta contribute to the unique flavor of the dough + brings about changes (maturing or ripening) in the strucutre of gluten
• CO2= leavens the dough + produces a light, airy baked product

1. TRADITIONAL ACTIVE DRY YEAST:
   - it needs to be dehydrated in warm water (43-46C) with sugar before use
   - presence of sugar foam= indication of viability
   - temp. higher than 60C kill yeast and lower than 38C cause glutathione to be leached from the yeast cells (dont want in bread making cause it limits gluten development)
   - activity is decrease by exposure to O2, heat or humidity so need to be refrigerated after open
2. INSTANT YEAST:
   - more soluble form of ry yeast that dont have to be rehydrated before use
   - appears finer
   - add directly to dry ingredients
   - temp. of the liquid can be as high as 50C because the flour mxture quickly cools the mixture
   - use in breads machines
   - last ingredient added on top to protect from the liquid that is heated at the bottom

** Traditional and instant yeast are the most popular because of their long storage life

3. COMPRESSED YEAST:
   - softened for a short period in water (27-30C) before combining with dry ingredients
4. SOURDOUGH STARTER:
   - mixture use to make bread prior to the reliable availability of yeast.
   - starter (sponge): living culture of acid-tolerating yeast + lactobacillus bacteria in a symbiotic relationship. Its made by mixing yeast, water and flour + left at room temp. for couple days to ferment
   * lactobacillus : uses saccharides in flour to produce lactic and acetic acids (create low pH which is favorable for yeast to produce CO2)
   * a portion of the starter can be used for bread recipe and the rest is refrigerated but resplenished at least weekly or each time some is removed (add flour and water and let sit at room temp. for the night)
   - coarser texture because acidity break gluten strands
   - sour and flavourful taste because of the activity of acetic acid and acid lactic

Question 2

fermentation of yeast

Answer 2

• depend on the environment temp. and food source
• optimal temp. for yeast growth= 30-35c BUT 35-37C are more practical at home
• below 24C: fermentation is slow
• higher than 37C: the dough may rise before it has a chance to mellow
• food of yeastL sucrose, fructose, maltose, glucose (nt lactose) and if absence of sugar, yeast can slowly hydrolyzed glucose from flour
• sugar : provide flavor, tenderizing + browning but too much = decrease gluten formation + draws water away from yeast

Question 3

steps for bread making (1-2)

Answer 3

1. HYDRATING AND SOLUBILIZING FLOUR AND YEAST: - when water= added, a sticky plastic mass is formed, so the sponge method only add parts of the flour at this point and lets the mixture stand= improves final flavour and texture
2. MANIPULATION VIA STIRRING, BEATING, OR KNEADING:
   - important to keep the dough on the soft side and not add too much flour
   - dough= becomes stiffer and less sticky
   - dough develop storn network of gluten (glutenin and gliadin proteins) + takes on a silken elasticity capable of retaining gas and water vapor during fermentation
   - gluten forming proteins absorb more water + form better network when cold (this is why some bakers add a small amount of crushed ice just before kneading)
   - max gas retainingcapability: make a dough with optimal balance of extensibility and resistance
   - extra ingredients (nuts and raisins)= add at the end of kneading to not interfere with gluten development
   - when indentation is made with 2 fingers= dough’s shape returns quickly
   * under-mized or ocer-mixed= oo extensible or too resistant= compact bread

Question 4

steps for bread making (3-4)

Answer 4

3. FERMENTATION:
   - yeast cells use available sugars for enery and produce CO2 and ethyl alcohol.
   - gluten becomes more elastic + acidity and volume increase
   - high in temperature= sticky dough that is hard to handle + facilitate growth of bacteria that produce undesirable flavors
   - under-fermented breads= coarse + small + compact
   - over-fermented = coarse + small + pale in color (due to depletion of sugar by yeast) + sour odor (overproduction of lactic acid)
   - fermentation depends on:
4. type of flour
5. room temperature
6. type of yeast used (instant results in shorter time for fermentation)
7. concentration of sugar and salt
   ** usually 1-1.5 hours but 10 minutes for instant yeast
   - deal fermentation= 26-30C (pan of hot water in the oven with the light on= good environment)
   after that, the dough should not regain its shape after you make 2 fingers
8. PUNCHING DOWN
   - pushing down and folding the dough after it has doubled in bulk during fermentation:
9. releases excess gas
10. prevents the air holes from becoming too big and forming an uneven grain.
11. prevents the film of gluten from over-stretching
12. redistribute yeast (which has reproduced in clumps), nutrient and heat so that yeast is surrunded by a new food supply

Question 5

steps for bread making (5-6)

Answer 5

5. PROOFING:
   - it is a final shorter rising period after the dough has been shaped (it should have doubling in size)
   - INSUFFICIENT PROOFING= the product will tear along its sides during the first few minutes of baking during oven spring
   - OVER-PROOFING= creates a bread with large holes and crumbly texture
   * when proofing is done= dough should partially regain its shape when pressed with 2 fingers
   * bread dough can be frozen before the final rise : some yeast will die so a little extra could be added to the recipe + need to be thawed for about 3 hours before proofing
6. BAKING:
   - surface may be slached in few places to prevent steam from becoming trapped under the surface of the crust
   - baking French bread: oven is filled with steam to form a soft crust. steam applied after baking evaporates quickly and causes the crust to be drier
   * top of bread is no higher than center of the oven

Question 6

steps for bread making (7)

Answer 6

7. OVEN SPRING:
   - it is the considerable increase in volume that occurs during the first 10-12 minutes of baking
   some results:
8. rapid expansion of gases
9. evaporation of alcohol into gas
10. increased yeast fermentation and enzyme activity
11. softening of the gluten as the temperature rises
    - inedequate fermentation= poor oven spring and a small loaf
    - too much oven-spring= a loaf with a flap top that balloons over the sides of the pan, and a crumb with a moth-eaten appareance
    causes: low oven temp. , insufficient salt or over-fermentation
    - at 60C: starch granules that are between gas bubbles begin to gelatinize and yest is killed
    as temp. increases, enzyme activity increase due to denaturation and gluten proteins coagulate
    semir rigid/self-supporting structure of bread: combination of coagulated protein and partially gelatinized starch
    - at 93C (thermomether in the center): it is done (golden brown and sounds hollow when tapped on the bottom and comes away from the edge of the pan) so have to remove from the pan

Question 7

effects of some selected ingredients

Answer 7

1. BARLEY AND MALT SYRUP: provides enzymes that help break down flour into food for yeast
2. COARSE GRAINS AND SEEDS: need to be added after kneading or may damage gluten strands
3. DRIED GROUND BEANS: like chickpea flour increase yeast growth, dough performance, flavor, nutritional quality
4. MILK: provide minerals that increase yeast activity, protein, tenderizes, enchances crust color, acts as a buffer preventing change in acidity that could damage baker’s yeast; scalding is important because there is a protein in whey that can cause reduced loaf volume. Lactose= not used by yeast so provide sweetness
5. GRAPE JUICE CONCENTRATE: contaisn propionic acid (mold inhibitor)
6. SALT: tightening effects on gluten, slows yeast activity, contributes flvor, control bacterialgrowth; sea salts contains more minerals which promote gluten development
7. SPICES: small amounts of it increase yeast activity: caraway,cardamom,cinnamon,ginger,mace,nutmeg
   - cinnamon and cloves contain cinnamic aldehyde and eugenol, which act as preservatives, inhibiting molding growth
   - dry mustards inhibits yeast activity
8. VITAMIN C: enhances gluten development, may be added as a crush tablet
9. FAT: if added to flour before liquid, coats gluten-froming proteins and reduces gluten formation, otherwise increases gluten’s gas holding ability
10. EGGS: whole and whites leaven; yolks hold things together and emulsify; keeping fat and mositure together, softening and decreasing staling
11. HONEY: contains fructose, which is more hygroscopic than sucrose or glucose, therefore helping bread retain moisture

Question 8

artificial sweetener why we use them

Answer 8

• reduce caloric content of foods prepared by using them instead of sugar
• negligible effects on blood glucose levels and are therefore acceptable for moderate use in diabetic and weight loss diets
• not all of them are heat stable (lose sweetness at high temp. for long period) ex: take sucralose (stevia) and sugar win instead of aspartame (equal)
• should only replace a portion of the sugar but does not only have the role of sweetener but also role texture (ex: baked goo may be very dense, less tender, or not brown but crispy)

the ones approved in Canada:

1. acesulfame-potassium
2. aspartame
3. erythritol
4. neotame
5. stevia
6. sucralose
7. sugar alcohols (sorbitol, mannitol…)
8. thaumatin
9. saccharin

Question 9

acesulfame-potassium, aspartame (equal), stevia and sucralose

Answer 9

1. acesulfame-potassium:
   - 200 times sweeter than sugar
   - can tolerate baking temp.
   - it is neither carcinogenic nor mutagenic
   - approves fro tabletop sweeteners, chewing gum, puddings, gelatin…
2. aspartame (equal)
   - 200 times sweeter than sugar + clean taste
   - break down at normal baking temp. + no longer sweet
   - most widely used artifical sweetener available
   - used for soft frinks, desserts, breakfast cereals chewing gum…
   - people with phenylketonuria (PKU) need to avoid it because it is a methyl ester of aspartate/phenylalanine dipeptide
3. stevia
   - 300 times sweeter than sugar
   - calorie-free
   - refered to the leave of the plants Stevia rebaudiana
   - no toxicity, use all over the world ex: japanese diet coke
4. sucralose (splenda)
   - 600 times sweeter than sucrose
   - may be used in cooking and baking
   - when consumed, it is excreted unchanged

Question 10

3 functions that sucrose have but not artificial sweeteners

Answer 10

1. BROWNING
   - with heat + acidic ingredients, sucrose breaks down into GLU and FRU to provide browning through maillard reaction (enhance color and flavor)
2. TENDERIZING
   - sucrose combines with flour proteins to prevent gluten formation
   - sugar can substitutes fat for sugar as a tenderized, very important in fat-reduced baked goods
3. LEAVENING
   sugar is a major contributor to leavening by helping to incorporate fine air bubbles into the batter in the creaming step

Question 11

what the recipe 100% whole wheat bread shows

Answer 11

• allowing the flour to stand with the liquid for 20 minutes hydrates the flour proteins and give good gluten with less kneading
• milk contributes minerals provinding for good yeast growth. protein and sugar in the milk make better crust color, add flavor, and keep the loaf moist
• sugars from the milk and honey provide plenty of food for the yeast for a better rise
• honey adds flavors, feed the yeast and absorbs moistture from the air for good keeping qualities

Question 12

what the recipes country rye bread shows

Answer 12

• the colour of rye flour depends on the amount of branch that is removed in the milling process. the less bran that is removed= darker and denser the flour
• rye flour is high in fiber but low in gluten = its low gluten means breads made with rye flour does not rise well
• to compensate, many cooks often mix rye flour with wheat flour, which better allow yeast to develop and the bread to rise