EXAM 2 Flashcards
Polymers that form gels
Carbs: Amylose fraction of starch (polymer of glucose); Pectin (Polymer of galacturonic acid)
Protein: Gelatin (polymer of amino acids)
Emulsion
liquid in liquid dispersion
- dispersed or discontinuous phase= usually oil
- dispersion or continuous phase= most likely water-based
Emulsifier
- a stabilizing compound that helps keep one phase dispersed in another
- act as a surfactant: surface-active agent that reduces a liquid’s surface tension to increase its wetting and blending ability
- large molecules with hydrophilic and lipophilic ends
Thickeners
used in food preparation to improve mouthfeel of foods by increasing viscosity of liquids
Most Common thickeners
Carbs: Cereal Grains; Roots and Tubers
Proteins: egg and gelatin
Viscosity
The property of a fluid that resists internal flow by releasing counteracting forces
Coalescence
To grow together, unite into a whole
- may happen in extreme temps
Moist heat
gelatinizes starches
dry heat
caramelizes sugars
Heat application of proteins
denatures or coagulates proteins
Water
Foods have 0-95% water content
Chemically: H+ and OH- (polar)
- one oxygen atom flanked by two hydrogen atoms (H2O)
Solute
solid, liquid, or a gas compound dissolved in another substance
Dispersion system: Two Phases
Dispersed Phase: Solute
Continuous Phase: Solvent
What does the classification of solutions depend on?
- state of matter
- size of the dispersed particle
Classification of Solutions
A. True Solutions
B. Colloidal Dispersions
C. Coarse Dispersions (Suspensions)
True Solutions
- Homogeneous
- Stable
- Very Small Particle
Colloidal Dispersions
- Heterogeneous
- Less Stable
- Intermediate Particle Size
Coarse Dispersions (Suspensions) - all 3 involve a solute and a solvent [a dispersed phase (particle) and continuous phase (dispersed medium)]
- Heterogeneous
- Very Unstable
- Large Particle Size
Solution
- Common in foods
- solute (dispersed phase) very small ions or molecules
- Mixture is homogeneous due to kinetic motion of solute
- Usually very stable
- Incapable of forming gels
Types of Colloidal Dispersions
- Gel
- Foam
- Emulsion
- Sol
Gel
liquid-in-solid dispersion (somewhat rigid)
- jam, gelatin, cheese, butter
Structure:
- Long chain like polymers cross-linked randomly to produce a 3D structure
- Large particles connect loosely: Forms a network that traps liquid, liquid keeps the polymer network from collapsing
Produced mixing larger water soluble molecules in solvent
- gel
- protein
Foam
gas-in-liquid or gas-in-solid dispersion
- Air/raw egg white, whipped cream, marshmallow
Emulsion
liquid-in-liquid dispersion
- oil/vinegar, milk, butter, mayonnaise, salad dressings
Produced by mixing 2 immiscible substances
- oil and vinegar
- Fat and Water
Sol
Solid-in-liquid dispersion (pourable)
- gravy, jellies
Gels: Characteristics
- Mainly fluid, behave like rigid solids
- Soft, but resilient and elastic
- Holds the shape of its container
- Affected by temperature, pH, and concentration
Starch Thickeners
- used to increase viscosity of soups, and gravies to improve the mouthfeel of the solution
- product then becomes a coarse dispersion (suspension)
Starch
- Complex carbohydrate
- provides energy
- Well-balanced diet has 45-65% calories from carbohydrate
- Food industry uses starches widely
Characteristics of Starch
- Plants serve as source of starch granules
- granules are plant cell’s unit for starch storage
- Common sources: wheat, rice, and corn
- root starches: Potatoes, arrowroot, and cassava (tapioca)
Starch granule sizes (largest to smallest)
- Potato starch granules
- Corn
- Tapioca
- Rice
- Taro root
Cornstarch
Wet milling derives starch from corn
- major source (90%+) of starch in the United States
Starch in Food Products
- Thickening Agent
- Edible Films
- Dextrose (e.g., sweetener)
- Starch Syrups (e.g., corn syrup)
Starch Structure
- Polysaccharide
- long chains of repeating glucose molecules
- linked together in form of either:
- amylose
- amylopectin
amylose
primarily linear molecules
amylopectin
highly branched
Starch Characteristics in forming Gels
Starch Structure
- Most starches are about 75% amylopectin and 25% amylose
- High-amylose starches: 40-70% amylose
- All starches contain some amylose
- The varying content of amylose is what causes texture difference in starchy foods
waxy
starches consisting entirely of amylopectin
Starches with higher levels of amylose
tend to gel
- grain starches (corn, wheat)
starches with higher levels of amylopectin
are nongelling, still somewhat gummy
- root starches (potato, tapioca)
Starches are valuable due to their ability to undergo
- gelatinization
- gel formation
- retrogradation
- dextrinization
Concentration of amylopectin and amylose in a starch determines to which degree these processes will take place
Gelatinization definition
Increase in volume, viscosity, and transluscency of starch granules when heated in a liquid
- cells swell, absorbing water, increase volume, improve viscosity
factors influencing gelatinization
A. Water- sufficient to hydrate starch
B. Temperature- varies for starch
C. Heating time- do not go beyond temperature time
D. Stirring- to prevent lumping
E. Acid- neutral pH necessary
F. Sugar- competes with starch for water; add more water
G. Fat- delays gelatinization
Gel Formation
Viscous hot paste (sol) upon cooling becomes semi-rigid (gel)
Reversible process
Sol–Gel
Gel+Heat–Sol
Cooled Sol to gel–process is called gelation
Dependent on presence of enough amylose molecules
- amylose will gel
- amylopectin will not gel
High amylopectin starches
- thicken at lower temperatures
- are ideal for pie fillings and sauces
Include: - cornstarch
- tapioca
- potato
- wheat flour
retrogradation
As gels cool, bonds continue to form between amylose molecules, and retrogradation occurs
- phenomenon during cooling of gelled starch when amylose and amylopectin molecules “retrograde” and realign themselves
- staling in baked products and syneresis (weeping) in gels may occur
Dextrinization
breakdown of starch molecules to smaller, sweeter-tasting dextrin molecules in the presence of dry heat
- results in an increase in sweetness
- dextrinized starches lose much of their thickening power
- dry heat applied to starch
ex. toasted bread
Modified Food Starch
- manufactured product from natural starches by chemically altering molecular structure
- created to satisfy a particular food manufacturing purpose (stronger gel, freeze resistant)
- Do not separate (retrogradation or syneresis)
- Safe (FDA- just as digestible as unmodified)
pregelatinized starch
Instant or pregelatinized starches - to alter starch's gelatinization, heating times, freezing stability, cold-water solubility, or viscosity, starches can be modified - physically - enzymatically - chemically Starch cooked and dried Used in "instant" mixes
Gelatin
- Protein used in foods to form gels
- Extracted from the hides, skin, and connective tissue of all types of animals
- Obtained from hydrolysis of collagen
Preparation of gel
- Add water to gelatin powder
- disperse by heating
- Stir
- Cool
Phases of Gel Formation
- Hydration
- Dispersion
- Gelation
Hydration
- Gelatin can absorb 5x its weight in hot water
- extremely effective gelling agent
Dispersion
- hot liquid added to disperse protein molecules
- After Protein is completely dispersed, remaining liquid may be cooled
Gelation
Viscous hot paste (sol) cools to a gel
- change occurs as protein molecules form cross-linkages to trap water in a meshlike network
- water remains trapped
Factors influencing gel formation
- concentration of gelatin
- temperature
- sugar
- acid
Things to avoid in gelatin
- Salts
- Foods containing the following proteolytic enzymes
- Added Solids
Most common cereal grains
- Corn, rice, wheat, and barley (95%)
- remaining 5% of world production of grains include sorghum, millets, oats, and rye
Reasons cereal grains are consumed worldwide
- easily produce
- low cost
- nutritional value (fiber, complex CHO), especially whole grains–possessing functional food properties (lower CVD risk)
DGA’s recommend ___ of cereal intake should be ____ _____
1/2, whole grains
Structure of cereal grains
- Endosperm
- Husk “chaff”
- Bran
- Germ
Husk “chaff”
- protection from weather
- not usually consumed; can be processed into fiber supplements
Bran
- removed in the process of making white flour
- excellent source of indigestible fiber, vitamins and minerals
- Aleurone–high in protein, B-Vitamins and minerals, and some fat
- makes up 14% of the kernel
Endosperm
- makes up 83% of the grain
- contains starch
- source of complex digestible carbohydrate
Germ
- 2.5% of the grain
- rich in fat, incomplete protein, vitamins, and minerals
- susceptible to spoilage due to fat content
- Sold separately as wheat germ (excellent source of B-vitamins & Vitamin E)
Cereal Grain Processing
A. Some crack- to break kernel and cellulose into larger pieces - steel cut - rolled - ground B. Fractionation- removal of 1 or more portions of kernel to achieve specific storage or cooking properties - hulling - milling - polishing or pearling - ready-to-eat cereal
Steel cut
each grain is cut into about 3 pieces
rolled
grain is steamed and rolled flat b/w two smooth rollers
ground
often called “meal” such as flour
Hulling
hulls removed from popcorn to ease popping
milling
bran and germ removed—white flour
Polishing or pearling
bran and germ removed—-white rice
Ready-to-eat cereal
fully cooked
Cereal Grain Milling
- cereals are sent to the mill to be ground into flour
- Hull removed
- whole grain cereal is left
- contains bran, endosperm, and germ
Whole grain flour and White flour
Whole grain flour - palatability (heartier taste) - rancidity (spoils easily) Bran and germ are removed to produce White Flour - produced from endosperm of the cereal grain - ground into flour (enriched)--Bleached (UVlight or benzoyl peroxide)--enriched white flour - enriched with certain
wheat flour
~75% of all the harvested wheat is made into flour (white and whole grain flour) Remaining 25% is used for cereals, pasta products, animal feed, wheat germ and wheat germ oil
Types of wheat flour
- whole wheat
- white
- bread
- cake
- all purpose
- pastry
- instantized
- self-rising
- semolina
types of non-wheat grain flour
- garbanzo flour
- rye
- cornmeal
- soy
- triticale (hybrid of wheat and rye grains)
- potato
Bread Flour
- specialized for using in yeasted breads
- high protein content~14%, allows for more gluten development (higher rise)
Cake Flour
- fine textured wheat flour with high starch and low protein content
Instantized Flour
- mixes easily with water, readily gelatinizing without lumps
- Ideal for powdered soups, sauces, and gravies
slef-rising flour
- already has leavening agent and salt added
Durum (Semolina)
- high protein (more gluten) breed of wheat
- highest protein content (9-18%) makes it best in manufacturing of pasta products
Gluten
the protein portion of wheat flour with characteristics necessary for the structure of most baked products
Wheat flour components for structure
Starch=amylose - gelatinizes in moist heat Proteins - structure proteins - GLUTENIN - GLIADIN Glutenin+Gliadin=Gluten \+H2O \+manipulation (kneading)
Two Steps for gluten formation
- Hydration (gluten forms upon hydration, meshwork protein containing water)
- kneading (increases gluten strength by realigning protein molecules to be more parallel and encourage cross linkage sulfide bonds)
What is Responsible for the structure of Bread?
- gluten
- starch
- increased temperature during baking
gluten free flour needs…
vegetable fat, whole milk, and eggs to create structure
Batters
Pourable
- drop 1:2
- pour 1:1
Doughs
Stiff; do not flow
- stiff 1:4
- soft 1:3
Crumb
Most noticeable palatability factor in flour mixtures
- creates texture of finished products
Influenced by…
- number and size of air cells produced in batter or dough
- amount of starch gelatinization
- degree of protein coagulation
Maillard reaction
CARAMELIZATION
- reaction b/w sugar and protein resulting in formation of brown complexes on food
- starch in the flour can be partially broken down by enzymes (amylases) into dextrin, malt, and glucose
- occurs in conjunction with caramelization of sugars
Caramelization
- To caramelize=to brown
- when sucrose is heated 365 degrees, it melts
- sugars+starches+amino acids or proteins
- browning occurs through maillard reaction
- aldehyde from sugar or starch reacts with amino (N) group of proteins–development of brown complexes
- browning occurs through maillard reaction
Caramelization process
Further heating–yellow–light brown–darker brown–decomposition (“burnt” toasted marshmallow)
Flour
- starch for gelatinization
- partially responsible for crumb formation
- effected by number and size of air cells (leavening)
- degree of starch geatinization
- degree of protein coagulation
- contains amylase
- contributes to structure of finished product
- gluten
Amylase
breaks down starch to dextrin, glucose, and malt contributing to sweetness
- partially responsible for surface browning (caramelization)
Too much/too little flour?
too much=smaller volume, more tunnels
too little= coarse texture, susceptible to collapse
Liquid
- required to hydrate flour and gelatinize starch
- required for gluten development
- acts as a solvent for dry ingredients
- provides steam for leavening
- may provide flavor, nutritional value
- proteins in milk contribute to Maillard reaction
- Lactose contributes to caramelization of finished product
Eggs, if included
- flavor, color, nutritional value (e.g. protein, fat-soluble vitamins)
- Provide structure
- egg protein coagulates at baking (heating) temperatures
- Emulsifying agent
- egg yolk contains lecithin
- Fat
- Some leavening
- beaten egg incorporates air
- Egg white foam may be primary leavener in angel food cake
- egg contains water which will be converted to steam when heated
Fat or Shortening
- Delays staling
- Tenderizer
- Adds Volume
- Contributes to flakiness
- Flavor
Sugar
- Contributes sweetness
- Contributes to Volume
- Increases coagulation temperature of gluten
- Increase Moistness and Delay Staling
- Increase tenderness
- Contribute to Browning
Too much/Too little sugar?
- Too much sugar usually results in lower volume since sugar competes with gluten for water
- too little sugar reduces browning and tenderness
Salt
- Taste
- Uniformity of crumb
- Increases dough firmness
- moderates solubility and swelling capacity of gluten
- Prolong shelf-life
- Tempers the growth of yeast
Leavening Agent
- Production of gas
- Stretches gluten to achieve volume
- Heat application will denature gluten to “set” the structure of the finished product
Too much/Too little leavener
- Too much leavener causes gluten “bubble” to burst
- Too little leavener results in inadequate rising–compact, heavy flour mixture
Leavened by steam
- all flour mixtures are minimally leavened by steam
- Solely steam leavened: popovers, cream puffs
Leavened by Foam
(unshortened cakes)
- egg white foam is “folded” into flour mixture to add volume to batter
Commercial Additives
Dough conditioner
- oxidizing agent
- reducing agent (encourage gluten formation)
- emulsifying agent (if fat in recipe)
Aging or maturing agent
Antioxidant
Bread
- Flour
- Water
- Yeast
- Salt
- Sugar
- Optional: fat and/or eggs
Yeast Bread
- leavened by microorganism production of CO2
- Bagels (boiled to gelatinize starch)
Raised Donuts - sugar competes with protein for water to lessen gluten development
Characteristics of good quality bread
- symmetrical
- evenly browned
- light
- Tender
- Fine, even moist crumb
Flour mixture terms definition
- Knead: to mix, using wooden spoon, wire whisk, electric mixer
- Proof: incubation time required for yeast to produce CO2 (fermentation)
- “to let the dough rise”
- requires controlled temperatures (yeast is sensitive to temperature extremes)
Straight Dough Method
- mix all ingredients together
- knead to develop gluten
- Proof (to ferment)
- first rising - Punch down (to redistribute sugars, yeast, and gluten & allows excess gas to escape)
- Second proof
- Punch Down
- Shape and Proof third time in loaf or other form
Sponge method
- Combine yeast, water, and 1/3 of flour to create a foamy mixture
- Add remaining ingredients and continue with kneading and proofing as in straight dough method
Quick breads
Leavened predominantly by baking powder
- Muffins
- prepared from batter
- minimal gluten development - Biscuits
- prepared from dough
- Fat is cut into the dry ingredients in the finished product
Muffin method
- Sift the dry ingredients together
- In a separate bowl, combine the moist ingredients
- Stir the dry and moist ingredients together with only a few strokes, until the dry ingredients are just moistened but still lumpy
quality muffin
- evenly browned, not shiny
- rough surface
- well rounded top, not peaked - fine even texture
- free of tunnels
Biscuit
- fat is cut into all dry ingredients using a pastry knife or two table knives held in opposite hands criss-crossing the bowl into pea-sized balls
- the fat-flour mixture is mealy
- liquid added last to moisten only
quality biscuit
- evenly shaped
- straight sides
- evenly browned
- double the thickness of rolled dough
- Flakey (crumb can be pulled off in sheets)
- Tender
- Free of spots
Biscuit method (steps)
- sift dry ingredients
- add fat, blend by “cutting”
- Add liquid
- blend until like coarse meal - knead lightly ~10 times
- roll from center to outer edge
- Cut
Pancakes and Waffles- Pour Batter
- Modification of muffin method
- Characteristics–light, tender, free from tunnels, and evenly browned
- If heavy or tough–too much gluten development
- Heated grill, pan, or waffle iron
Conventional Cake method
Conventional (creaming) method
- method most frequently used for mixing cake ingredients
- produces a fine-grained, velvety texture
- 3 basic steps:
1. creaming
2. egg incorporation
3. alternate addition of the dry and moist ingredients
In conventional cake method- don’t over-stir because
it creates a viscous mass that may not be able to rise during baking, and the texture will tend to be fine but compact or lower in volume, full of tunnels, and have a peaked instead of a rounded top
In conventional cake method- don’t under-stir because
it results in a low-volume cake from an uneven distribution of baking powder or soda or an incorporation of air into the foam; texture tends to contain large pores, have a crumbly grain, and brown excessively
Conventional Sponge method
- separate egg whites
- beat egg whites into a foam
- mix dry ingredients and fold into foam to produce angel food cake
Sponge cake
similar to creaming method, but some sugar is mixed with beaten egg or egg white, folding the foam into the batter
Shiny metal pans
- reflects heat, increases time
- produces a coarse crumb, lower volume
- used for cakes, cookies
Dull metal pans
- absorbs heat
- increases browning
- used for pies, bread
glass pans
- requires oven temperature reduction of 25 degrees F
Cast iron pan
- heat slowly, retain high temperature for longer time, heat evenly
- results in thick-crusted product
Pan shapes
- round pans: more even browning
- deep pans: require lower temperature and longer time
- Fill no more than half full to allow for expansion
- greater volume is achieved if only the bottom of the pan is greased
- dry pan sides provide climbing surface for batter or dough
Silicone bakeware
- non-stick
- poor conductor
- can withstand heat up to 500 degree F
- Flexible material
Pan material
good conductors: - aluminum - copper/stainless steel combinations - Tin Poor conductors - stainless steel - glass/ceramic
Baking time/temperature
- optimum temp dependent upon pan
If temperature is too high–crust forms before gases expand–cracked product with flow of uncooked batter from the center
Winter wheat
- hard wheat–bread flour
- planted in fall, germinates before frost sending out root structure to prevent erosion during winter
- high protein content (glutenin and gliadin)
Spring Wheat
- Soft wheat–cake flour
- planted in spring, harvested in fall
- low protein content
Breakfast cereals
- arose during a vegetarian movement about a hundred years ago
- ~75% consumed in the ready-to-eat form
- shapes vary, dependent upon method of preparation
- O’s
- Flakes
- Shredded
- Puffed
Couscous/Groats
Couscous: refined wheat in a granular paste
Groats: Whole wheat kernels which are not milled
Bulgur/Farina/Farro
Bulgur: Cracked wheat partially cooked
Farina: Granulated endosperm, fine texture
Farro: ancestor of modern wheat, AKA spelt
Cracked wheat/rolled wheat
Cracked wheat: wheat berries ground into smaller pieces
Rolled wheat: flattened berries between heated rollers; process similar to rolled wheats
Pasta
- made from semolina
- specific recipe of sough for specific shape
- Prepared using moist heat to gelatinize the starch and denature the protein
- double in quantity when cooked
Corn
one of the most versatile cereals, sued in flour mixtures, processed foods, and as a cooked vegetable
- cornmeal
- cornstarch
- hominy
- grits
Corn syrup
- viscous sweetener
- domestic product
- high in fructose, glucose and other sweeteners
Popcorn
- unique variety of corn, 14% moisture
- heating vaporizes water–kernel bursts
corn oil
- extracted from germ of corn kernel
- Omega-6-polyunsaturated fat
Rice
- half of the world’s population relies on rice as the staple grain
Brown rice
- whole grain (bran, endosperm, germ)
- takes ~1 hour
Polished rice
- milled and polished
- white powdery surface (premix) added to enrich (B complex vitamins)
- proper cooking preserves vitamins
- Bring 2 cups water to boil, reduce heat,, add 1 cup rice, simmer, covered until all water is absorbed–yields 3 cups cooked rice
Short rice
arborio rice
medium rice
glutinous rice
Long
Jasmine, Basmati
Converted or parboiled rice (long grain)
- partialli cooked under pressure to force premix into grain
- common in food-service establishments
Instant Rice
- totally cooked and dehydrated
- used in instant mixes, just added water
Arborio rice
Italian variety used in making risotto (short grain)
Basmati rice
extra long grain commonly used in india
Jasmine rice
Long grain from Thailand
- very fragrant, more delicate, floral flavor
Wild rice
- wild rice is not rice, but rather a reed-like water plant
- Harvested in great lakes region and in canada
- produced in minnesota and wisconsin by a native american group granted the legal ability to grow and level
- Never served alone, mixed with other ingredients in a recipe
- mixed with dried fruits, mushrooms, or citrus
Oatmeal
Heart Healthy Food
- active agent beta glucan, a soluble fiber (dissolvable in water) in oats
- Consumed within a lowered fat diet, moderately reduces serum cholesterol
oats
- only whole grain available
- pericarp, hull, husk–in milling hull and husk are partially removed (known as groats)
- groats flattened between heated rollers are ROLLED OATS
- quick-cooking oats: cut before rolling
- Regular or old-fashioned oats: rolled without cutting
- Instant oats: rolled extremely thin
Barley
Hulled barley: enclosed by a tough hull that is removed
Pearled Barley: bran, germ, and part of endosperm is removed
Malt: sprouted barley dried to stop growth
- enzymes present convert starch to sugars (maltose)
- used in alcoholic beverages
rarer types of grain
- millet (grown in Africa)
- Sorghum (cereal grain eaten as porridge)
- rye (contains gluten, used to make breads, crackers)
- Triticale (crossed wheat with rye)
- amaranth (high-protein, gluten-free)
- Kamut (ancient grain w/rich, buttery texture)
- Quinoa (good source of plant protein)
