Food Lab Exam Flashcards
1
Q
approx how much is a: pinch dash jigger scant
A
pinch: 1/16tsp
dash: over 1/16tsp but less than 1/8tsp
jigger: 3tbsp
scant: slightly less than measure
2
Q
how many mL is 1 cup imperial
how many g is 1 ounce imperial?
how many g in i pound?
A
1 cup: 230 mL
1 ounce: 28g
1 pound: 450g = 16 oz
3
Q
1 tbsp = x tsp?
A
1tbsp = 3 tsp
4
Q
conversion from F to C? C to F?
A
c= (F-32)/1.8
F=(Cx1.8)+32
5
Q
what is the detection threshold
A
the point at which a person can sense that a solution is different than water
6
Q
3 common tests used in taste panels
A
- preference and acceptance tests:
- comparative (which sample is preferred)
- monadic (rank liking on astandard scale of 5 or 9 points)
- consumer ranking tests - difference tests:
paired comparison, triangle, duo-trio, ranking tests (ask if a difference exists between samples) - descriptive tests: use structured or unstructured scaling
7
Q
what are 3 types of discriminative tests
A
- duo-trio tests: uses 3 samples. 2 are the same and one is different. one sample is designated as the reference. must identify which sample is the same of diff from the reference
- triangle test:
3 samples. 2 are the same, one is different
muwst determine which one of the 3 samples is different. no reference sample - paired comparison:
uses 2 samples. must determine which sample has the greater amount of a specific characteristic (ie. saltiest)
8
Q
3 classes of textural characteristics
A
- mechanical
- geometrical
- others
9
Q
5 primary and 3 secondary parameters in mechanical characteristics?
A
primary:
hardness: fore to cause deformation
cohesiveness: extent to which a material can be deformed before rupturing
viscosity: rate of flow per unit force
elasticity: rate at which a deformed material goes back to undeformed state
adhesiveness:
secondary:
factorability:
chewiness
gumminess
10
Q
what occurs when green veg are cooked?
what happens with exposure to alkali (ie. baking soda)?
exposure to zinc or copper?
A
plant cells rupture = releases organic acids = chlorophyll become permeable to acid = H+ from acids displace the central Mg atom in the chlorophyll =f formation of pheophytin (gren-green) or pheophytin b (yellow-green)
baking soda: can split off the phytl group to from chlorophyllin (bright green color). Destruction of thiamin, bitter taste, mushy texture
zinc or copper changes its color to bright green
11
Q
what color are anthocyanins in acid or basic environment?
A
acidic: red
basic: blue/black
12
Q
good source of flavanols
A
green tea
13
Q
good source of flavanols
A
greentea
14
Q
why are cereals cooked?
what happens during cooking?
A
to soften the outer shell(hull) allows starch grains to swell and gelatinize improve digestibility lose raw starchy flavor dextrin formation = enhances grain lavor
15
Q
what parts of the rice are removed? what contains the rice’s nutritional value?
what is the most nutritious rice? why?
A
outer inedible husk is removed a the bran and germ remains (contains rice’s nutritional value)
most nutritious white rice: parboiled or converted ice (has been soaked and steamed under pressure before milling. More nutrients are preserved in the grain)
16
Q
what influences the stickiness of rice?
A
higher amylose (long chains) and lower in amylopectin (short branched chain) will be LESS sticky
17
Q
why does high amylose rice harden when cooled?
A
the long amylose molecules bond together
18
Q
2 methods to separate rice grains
A
- soak in cold water and rinsing (gets rid of excess starch)
- sauteing in fate: seals the starch in the grains
19
Q
what is triticale
A
hybrid from crossing wheat and rye
nutty flavour
20
Q
2 ancient strains of wheat
A
manut and spelt
21
Q
types of wheat
A
bulgur, cracked wheat, rolled wheat, wheat berries, farina (cream of wheat)
22
Q
gluten-free grains
A
rice corn millet sorghum amaranth buckwheat quinoa teff
23
Q
what are 3 grain-like products
A
quinoa
amaranth: has gelatenous textrure
buckwheat: strong nutty flavour
24
Q
plant alternative to gelatin?
A
agar flakes
carrageenan (from algae and seaweed)
25
how to use gelatin
soften in cold water before dispersing in another liquid
| avoids clumping
26
what are factors that affect gelatin setting power
1. gelatin concentration
2. sugar: sugar decreases gel strength by competing with water for binding sites on gelatin molecules
3. acid: more tender when acidic (most rigid between ph5 and 10). acidity decreases thickening power of starches by hydrolyzing starch molecules. acid should be added once the starch mixture is cooked and thickened wha
4. salts: salt results in a firmer gel
5. physical interference: pieces of fruit or veg interferes with bond formation. should be added after thickening has occured
6. enzymes: from some raw fruits and veg can denature gelatin
7. temp and time. if boiled, gelatin loses its setting ability.. if cooled quickly, a weak gell would be formed.
27
how are emulsions classified?
based on degree of stability (stability increases with thickness)
1. temporary emulsion: thin viscosity and stability
2. semi-permanent emulsions: thick cream viscosity. more stable.
3. permanent emulsion: very thick viscosity. very stable
28
what is the purpose of starches in food prep?
to thicken
ex: wheat flour, cornstarch, tapioca, arrowroot, sago starch, etc
29
what determines starch's characteristics
ratio of amylose and amylopectin
30
what problems occur because starches tend to clump? how to prevent?
only starch granules on the outside of the lump can absorb water and gelatinize. this creates a water-proof gel coating while granules on the inside stay dry
prevention: separate or disperse granules before liquid is added (ie. coating with starch with fat)
31
describe the process of gelatinization
1. starch and liquid mix = reversible swelling of the starch
2. heat mixture = more h20 is absorbed = more swelling = starch softens = irreversible breakdown (gelatinization) = becomes more translucent
3. pasting: starch granules swell enormously = starch leaks out of the granule (amylose) = evaporation of water = starch loses raw flavour
4. thinning: overcooking = starch granules rupture
5. cooling of starch paste with high amylose content = gel forms quickly = cloudiness
cooling of starch with lower amylose = remains translucent = doesn't gel as well (but thickens due to amylopectin)
32
what is syneresis
leakage or separation of liquid from the gel
occurs when a cooled starch gel is left standing for some time because amylose molecules continue to form bonds which forces water out
33
what are white sauces?
what do designated numbers mean?
(bechamel)
made with milk, thickened with flour dispersed in fat (roux)
designated as 1,2,3,4: thin, medium,thick, very thick. (numbers refer to the number of tablespoons of butter and flour used per cup of liquid
34
what is a veloute? creamy veloute? mornay sauce?
white sauce.
uses a white stock as the liquid (poultry, fish or veg based stock)
creamy veloute uses cream in addition to the stock
mornay: has cheese
35
what is a brown sauce
made with a brown roux and brown stock.
36
what is a reduction sauce? how is it made?
has no flour.
developed from simmering a liquid until most has evaporated and liquid has thickened to a syrup consistency
37
what are pastry cream and pie fillings
starch and egg-based
38
what is pre-gelatinized starch?
what are the consistency categories? what is used to measure it?
what affects thickening capacity?
used in instant and canned puddings so that puddings will thicken without cooking or will not retrograde
used for people with dysphagia (swallowing disorder common in elderly). Thickening a beverage reduces speed of transport of the bolus from the oral cavity to the esophagus and prevents choking
a consistometer is used to obtain the consistency categories:
1. nectar
2. honey
3. pudding
thickening capacity depends on:
1. ph
2. mixing method
3. consumption delay
4. temperature of holding and service
39
describe pureed and blenderized diets:
have modified tetures to accommodate chewing or swallowing difficulties (ie. dysphagia)
purred foods: consistency similar to applesauce or mashed potatoes
blenderized diets: food products must be able to pass through a straw
40
what are the stages of egg white foams?
soft peak
stiff peak
dry stages
usually recipes require soft or stiff
used to reduce caloric content in a volume of food (can incorporate high air volume)
41
what are factors that affect formation and stability of egg-white foams
1. copper bowl
2. temp
3. concentration
4. acid
5. sugar
6. fat
7. over beating
42
how does using a copper bowl affect egg-white foams?
copper reacts with conalbumin = increases volume and firmness of the egg white
43
how does temp affect egg-white foams?
egg whites at room temp reach volume more quickly because it has lowered surface tension of the warmer egg whites
44
how does concentration affect egg-white foams?
dilution with water = inc volume = decr stability
45
how does acid affect egg white foams?
acids decreases the ph near the isolectric point = proteins are more sensitive to denaturation = increases beating time but increases stability
46
how does sugar affect egg white foams? how should it be added?
sugar increases the time needed for development of foam, but the foam is more stable.
sugar should be added when the eggs begin to foam. should be added little at a time and beaten after each addition
if sugar is added before beating = need more beating to produce foam = more stability but reduced volume
if foam is beaten too stiff after each sugar addition, it will be dull after baking
47
how does fat affect egg white foams?
fat interferes with the formation of foam
egg yolks, dirty utensils and bowls are common for fat contamination
48
how does over beating affect egg white foams?
| when is the peak of stability in foam?
peak of stability: before max volume occurs
thus over beating produces an unstable foam. Easily collapses and becomes coarse
49
describe the use of egg yolks in custards?
- has a greater thickening ability than whites
| - custard: gels formed from the enmeshment of milk by coagulated egg protein
50
how are soft and baked custards cooked?
what if starch is present?
what if overbaked?
soft custards: double boiler
-ex: creme anglaise, pastry cream, lemon curd, zabaglione
baked custards: baked in the oven with a bain-marie (water bath) to equalize the temp to obtain a homogeneous texture. If starch is present, starch prevents curdling by limiting rejoining of proteins after they denature
-ex: cheesecake, flan, quiche
if overbaked: custard will curdle and weep (syneresis)
51
uses of oils
```
cooking medium
to brown
fry or saute
binding agent in baking
preserving agent (ie. sun dried tomatoes)
ingredient (ie. salad dressings)
```
52
what are MCTs
medium chain triglyceride
processed from coconut oil to contain medium chain fatty acids
more easily hydrolyzed and absorbed than long chain FA in conventional fats
MCT oil often used for fat malabsorption
53
what are oils with low smoke points
olive oil and sesame oil and coldpressed oils
should not be overheated
54
oils with high smoke points?
peanut canola sunflower clarified butter
55
what happens when fat is heated to its smoke point?
triacylglycerols break down into free FA and acrolein is formed
acrolein: substance that is irritating to eyes, nostril, lungs and digestive system
smoke indicates the oil could ignite (flashpoint)
oils should be discarged if it has reached the smoke point
56
what are factors that decrease smoke point of fats
emulsifiers
length of number of times the fat is used: causes deterioration
presence of food particles:
shallow pan: exposes larger surface area to o2
copper, bronze, iron or brass pans/utensils: metals accelerate oxidative rancidity and deterioration of fats. (Stainless steel is best)
heating above smoke point (cold pressed oils have low smoke points. best for cooking purposes)
57
how should foods be fried?
what increases fat absorption?
should be dried to avoid water and fat from spattering
- should be fried in small batches to avoid drop in temp of oil
- fat should be as high temp as possible but below smoke point (limits fat deterioration and greasiness). cooking at a lower temp would take longer = higher fat absorption
- fat absorption increases as proportion of sugar, liquid, leaving agent and fat in the food increases
58
what causes surface crispness in frying?
due to moisture loss (creates steam produced during frying). void left is filled with fat. once the steam has escaped, browning occurs
59
what causes browning in food during frying? what affects the degree of browning
maillard reaction (involves sugars, proteins and caramelization)
degree of browning depends on time, temp, chemical composition of the food (type of fat used doesn't matter)
60
what does the degree of aging of meat affect?
muscle stretching
| softening and changes in collagen struture
61
how does age of the animal affect tenderness of meat?
younger animals = less muscle development = more tender collagen
62
role of acid and salts and polyphosphates in marinades
tenderizes by causing meat to retain water
63
how does mechanical manipulation affect meat tenderness?
breaks muscle fibres and connective tissues
catalyzes hydrolysis of proteins
increases moisture retention
64
what is the effect of heat during cooking on proteins in meat?
-heat activates enzymes in the meat = degrades muscle proteins until they are denatured and inactivated
cooking meat at low temp for long times: allows for more protein degradation = meat shrinks and toughens = dehydration from water loss = decreases juiciness = further toughens meat
65
connective tissues in meat?
1. collagen: white connective tissue.
- triple-stranded coils
- surrounds muscle fibres, binding them into bundles
- surrounds whole muscles and makes up tendons and ligaments
- more predominant in muscles that are used more because strands form cross links with maturity
2. elastin is not softened during cooking
66
describe dry heat cooking methods
used for tender cuts of meat because smaller amount of connective tissue. cooking is not needed to hydrolyze the collagen
67
describe moist heat cooking methods
used for less tender cuts of meat
from moist heat from liquids. tenderizes meat through collagen hydrolysis
68
where do least, medium and most tender cuts of meat come from?
least tender: front of the animal
medium: hip and chuck:
most: least exercised muscles of the back of the animal
69
3 types of liquid milks?
ultra high pasteurized milk (UHT): put at very high temps. contains no bacteria
lactose-reduced milk: treated with lactase (converts lactose into glucose and galactose). tastes slightly sweeter
evaporated milk: approx 60& water content removed. slight caramel taste from the maillard reaction due to exposure to high temp of processing
70
what is buttermilk
traditionally: by product of butter making,= which separated from the cream
today: bacterial cultures are added to low/non-fat milk = transforms some lactose into lactic acid = sour taste
71
what is acidophilus milk
fermented milk with lactobacillus acidophilus (naturally present in the digestive system)
helps replenish normal intestinal flora following antibiotic treatment
72
what is sour cream
made from pasteurized cream soured with lsteptococcus lactis (bacteria that produces lactic acid)
73
what is yogurt
milk product fermented with lactic bacteria
bacteria: lactobacillus bulgaricus and streptococcus thermophilus
gelatin, pectin or carrageen can be used as stabilizers so whey is less likely to separate
74
what is kefir
milk product fermented with yeast
fizzy, frothy bitter drink
75
what happens if fermented milk products are pasteurized with UHT?
UHT = ultra heat system
bacterial culture will no longer be active = no more benefits to the digestive system
76
what is cheese?
what influences flavour, body and texture?
made from coagulating or curdling milk and separating curd from the whey
high in: protein, Ca, riboflavin, vit A, Na
influenced by:
- type of milk used
- quantity of salt,
- seasonings
- bacterial specis and mold used for inoculation
- processing method
- environmental conditions (temp, humidity, curing time)
77
2 classifications of cheese?
1. unripened:
- high moisture conent
- soft and fragile
- coagulated by acid
2. ripened:
- low moisture
- ripened for over 3 months
- tough and rubbery
- coagulated by rennin
- enzymes hydrolyse the casein curds to amino acids and ammonia, fat to fatty acids and acetate and the lactose to lactic acid
78
how does heat cause milk proteins to coagulate?
whey proteins?
casein?
lactoglobulin and lactalbumin (whey proteins) are denatured by heat and coagulates at 66deg C. precipitates form along sides and bottom of the pan and forms a skin on the top
casein: the predominant milk protein, is mostly unaffected by cooking but can curdle if concentration of protein is high
heat will accelerate coagulation in an already unstable milk emulsion
79
how does acid cause milk proteins to coagulate?
describe curds formed by acid
when ph of milk falls below 5.2, casein begins to coagulate because the neg charges that stabilize calcium phosphocaseinate micelles are neutralized by the pos charges of the H ions (from the acid)
casein salts form = milk curdles
curds formed by acid are soft with a high moisture content. low in Ca because mot of the Ca stayed in the whey
80
how do enzymes cause milk proteins to coagulate?
rennin is added to milk. curdling occurs in a 2 step reaction
1. rennin cleaves a bong with casein to expose chem groups
2. exposed chem groups react with Ca to form a curd
rennin optimal activity at 40deg C and pH 6.7
81
factors that affect milk and cream foams?
viscosity: incr viscosity = dec tendency of foam to collapse
conc of fat: more fat = more stability of foam
temp: lower temp = fat droplets harden and clump easier
sugar: helps prevent over beating by delaying curdling
82
what happens when cheese is overheated?
proteins coagulate and become tough and rubbery and fat emulsions may break = fat separates
83
what is yogurt cheese
made by suspending yogurt within a cheesecloth
84
why is fish more tender than meat
less connective tissue
85
what are factors that affect egg protein coagulation?
temp: egg white and yolk coagulate at differ temps.
conc: dilution of egg proteins raise the coagulation tep
acid: decreases stability = decreases coagulation temp
salt: lowers coagulation temp
sugar: increases coagulation temp
86
what causes the grey-green film at the yolk/white interface in hard cooked eggs?
reaction between Fe in yolk and S in white = iron sulfide
reaction is favoured in older eggs (more alkaline pH)
can be minimized by cooling quickly
