I D Food science & nutrient composition: starches, crystals, gelatin, coffee, additives Flashcards
purpose of amylose
gelation in cooked, cooled pastes
composition of starch
amylose + amylopectin
waxy starches only have ____**
AMYLOPECTIN (corn, rice, sorghum)
purpose of amylopectin***
NON-GELLING, STABLE TO FREEZING AND THAWING
what is the most effective starch thickener (most to least)?***
POTATO –> waxy corn –> waxy rice –> waxy sorghum –> tapioca –> wheat
why is wheat flour not an effective thickener?
b/c of the protein content
which is more effective- a starch itself or a waxy starch?
waxy starches
pastry & cake flour - thickening ability
less gluten, BUT more starch –> thicken better
what is gelatinization?
swelling that occurs when starch is heating in watch close to the boiling point
science/process of gelatinization –>
heat dissociates bonds, water moves in and swells granules –> friction is created causing paste to thicken
role of sugar in gelatinization
competes with starch for the water needed for gelatinization
what happens if too much sugar is used in gelatinization?
consistency is thin –> the water needed to dissolve excess sugar is not available for the gelatinization of starch (b/c the sugar took up all the water already)
when should you add an acid to a starch? why?**
when COOKING IS COMPLETE b/c ACID BREAKS DOWN STARCH = RUNNY product (if added too early) [ex: if lemon juice is added to lemon meringue pie before cooking is complete, filling will be runny]
what is retrogradation?***
HARDENING OF STARCH MOLECULES, RECRYSTALLIZATION = GRITTY texture
retrogradation occurs in what types of starches?***
those with a high proportion of AMYLOSE (more linear one)
cause of retrogradation?
freezing, aging
is retrogradation desirable?
NO- reduces quality of the food
example of retrogradation?***
staling of starch products (stale), such as bakery goods**; separation when a gravy thaws; old pudding; stale bread
what does heat do to starch bonds?
breaks the bonds holding the amylose together
retrogradation is accelerated by? what occurs?
freezing - when a starch gel is thawed, water is lost b/c it can’t re-bind to the fragile spongy mass
bread & staling (201 notes) –>
- FRESH BAKED BREAD = starch molecules, amylose and amylopectin, found in bread taken right out of the oven are swollen and randomly positioned
- FRESH BREAD = as the bread cools, the amylose molecules start to come together and crystallize; this crystallization changes the texture of the bread
- STALE BREAD = several days later, the amylopectin molecules come together and crystallize, further changing the texture of the bread; reheating reverses this process to some degree
what should you do with starch products you are going to freeze?
prepare with a starch or flour from a waxy cereal (better thickeners) - waxy corn, sorghum, rice
what is a modified starch?
chemical modification by acids and enzymes to change viscosity and ability to gel
example of a physical modification starch –>
pre-gelatinized starch used in instant puddings
when making gravy, what type of heat is used?
dry heat, no water –> temperature increases, degrading the starch, molecules break into fragments called dextrins
dry heat - color of starch
changes color (ex: browning of toast)
what happens with starch granules in cold water?
do not dissolve- form a suspension
when starch is heated with moist heat, what happens?
molecules swell, thicken, become translucent due to gelatinization
what happens if starch is not mixed in with cold liquids or is added directly to hot liquid?
lumps form = decreased thickening, outside granules swell and inside granules remain dry (think: when you try to add cornstarch to your hot stir fry sauce, always gets lumpy)
how to prevent lumps of starch in moist heat?
mix starch with fat, cold liquid, or sugar
composition of white sauces; AKA?**
- melt fat, add flour
- Roux = half fat, half flour
how can you get a clear, shiny, translucent white sauce?***
add CORNSTARCH for a thickener
what did you do wrong if a white sauce product is starchy tasting and grainy?
uncooked flour
what is an example of a thick white sauce?
souffle
how to make crystalline candies?
heat sugar and liquid (water or corn syrup or cream of tartar) to dissolve; heat further
crystalline candies crystallize under what conditions?***
conditions that produce SMALL CRYSTALS = SMOOTH, CREAMY FEELING
what do crystal inhibitors do?***
keep crystals SMALL AND SMOOTH; more that is added, more it is inhibited (help to control the size)
types of crystal inhibitors
- acid = cream of tartar, vinegar
- fat = chocolate, milk
- protein = milk, egg whites, gelatin
what happens to candies with further beating?
cools and stiffens rapidly
types of candies
1) crystalline sugar = fixed orderly pattern
2) non-crystalline sugar = amorphous, glasslike
examples of crystalline sugar candies
- large crystals = rock candy
- small crystals = fondant, fudge (fudge has more crystal inhibitors - chocolate, milk, corn syrup)
examples of non-crystalline sugar candies
hard candies, brittles, chewy candy, gummy candies, sourballs, butterscotch, taffy, caramel, marshmallows, jellies, gumdrops
crystallization can be prevented by adding interfering substances OR?
increasing concentration of sugar
corn syrup and candies
corn syrup retards crystallization, increases viscosity and chewiness
what is overrun?***
increase in ice cream volume from freezing and whipping
overrun is determined by ______; should be what #?**
WEIGHT- 70-80%
what does homogenization do?
makes ice cream smooth by making it easier to beat in air during freezing
___________ is necessary to keep ice crystals small and to incorporate air
agitation
for ice cream, ________ interferes with crystal formation, making crystals small and smooth**
FAT
what happens if you don’t add enough fat to ice cream?***
GRAINY with LARGE crystals
what should you do to produce a smoother ice cream?***
INCREASE FAT (more fat…more crystals…more smooth)
what is mellorine?
imitation ice cream- butterfat replaced by hydrogenated vegetable oil
nutrition of gelatin?***
INCOMPLETE PRO- NO tryptophan, LOW in methionine and lysine
properties and uses of gelatin –>
- changes liquid into an elastic solid
- acts as a foaming agent - marshmallows
- keeps sugar and ice crystals small in candy and ice cream by interfering with the union of small crystals to make larger ones
what should you do to promote gel formation when:
- making a large mold
- it will stand at room temperature for a long time
- acid content is high
- making a whip
increase gelatin or decrease liquid
what is bromelin?
an enzyme in fresh or frozen pineapple that breaks down protein and prevents gelation
coffee should be brewed at ____F for best flavor***
185-203
what happens to coffee when brewed at higher temperatures?***
tannin is extracted = bitter (NO boiled coffee)
percolator**
single contained, covered basket with stem, gives stronger and bitter coffee; water is hotter and repeatedly passes through grounds
dripolator***
three separate components; add boiling water to top and let drip through; brief contact with grounds; free of bitterness
vacuum brewed coffee***
higher temperatures than recommended
what substance decaffinates coffee?***
methylene chloride
who controls food additives?***
FDA
monoglycerides, diglycerides, lecithin, disodium phosphate are all examples of?
emulsifiers
glycerol monostearate is a?
humectant - retains moisture
carrageenan, pectin, cellulose, gelatin, vegetable proteins are all examples of?
stabilizers
sodium stearate is a?
anti-caking agent
what do nitrites do?
fix color, inhibit spores of clostridium botulinum
what is proprionate?***
preservative & MOLD INHIBITOR
what does ascorbic acid do?
enhances appearance by preventing browning
what are functional foods?***
provide more benefits than the basic nutritional benefits
functional foods: grape juice & red wine***
reservatrol (reduces platelet aggregation)
functional foods: omega 3 fatty acids***
in fatty fish, reduce TG levels
functional foods: tomatoes**
lycopene - may reduce prostate cancer risk
functional foods: fermented dairy products***
probiotics- support GI health
functional foods: fortified margarine***
plant sterols and stanol esters, reduce total and LDL cholesterol
functional foods: orange juice is fortified with?***
calcium
what are phytochemicals?***
biologically active, naturally occurring COMPOUNDS IN PLANT FOODS (help with chronic diseases, drugs, blocking carcinogens, CHD?)
examples of phytochemicals***
- thiols
- soy foods
- others: carotenoids, lycopene, phenols, favonoids, isoflavones, etc.
what are thiols? where are they found? what do they do?***
a PHYTOCHEMICAL found in CRUCIFEROUS VEGETABLES (SULFUR) - DETOXIFIES CARCINOGENS
what is food synergy?***
ADDITIVE INFLUENCE of FOODS and CONSTITUENTS which when eaten, HAVE A BENEFICIAL EFFECT ON HEALTH (group of things is greater than only one thing)
