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ndfs 251 Flashcards

1
Q

5 aspects of food quality

A

appearance, texture, flavor, nutrition, safety

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2
Q

subjective vs objective tests

A

subjective: use people, more variation, more time consuming and expensive, more for the consumer
objective: use instruments, quality control, faster and cheaper

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3
Q

food science

A

multidisciplinary study of food using chemistry, physics, and biology

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4
Q

3 ways food science is an applied science

A
  1. the development of food products and processes
  2. the preservation and storage of food
  3. the assurance of food safety and quality
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5
Q

academic subjects food science draws upon

A

chemistry, biology, physics, math, statistics

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6
Q

potential careers in food science

A

food product development, research, quality assurance, food analytical labs

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7
Q

how food science differs from nutrition and dietetics

A

-food science: effect of food and nutrients on the body
-dietetics: medical nutrition therapy, food service administration, public health

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8
Q

3 categories of sensory evaluation

A
  1. discrimination or difference tests
  2. descriptive tests
  3. affective or preference tests
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9
Q

discrimination/difference tests

A

untrained panelists asked to assess differences
ex. paired comparison, duo-trio, triangle

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10
Q

descriptive tests

A

trained panelists asked to describe sensory properties
ex. descriptive analysis

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11
Q

affective or preference tests

A

consumers asked to determine degree of liking
ex. hedonic scale, ranking

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12
Q

purpose of standardized testing procedures

A

allow for confirmation of results via repetition and comparisons between laboratories

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13
Q

quality assurance vs research

A

-quality assurance: quick, less accurate, simple to perform, precise
-research: more accurate, slower process, sensitive (measure small differences), and precise

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14
Q

roles of water in food

A
  1. allows for mobility of reactants
  2. solvent for ingredients
  3. allows for microbial growth
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15
Q

water molecule

A

oxygen and hydrogen are covalently bonded, dipole nature (unequal sharing of electrons)

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16
Q

phase changes

A

-endothermic reactions: heat input (solid>gas)
-exothermic reactions: gives off heat, heat removal (gas>solid)
-temperature doesn’t change during a phase change because energy is expended

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17
Q

latent heat

A

heat absorbed or released by a substance during a change in state

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18
Q

sensible heat

A

heat that results in a temperature change in the substance without a phase change

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19
Q

elevation and boiling point

A

for every 960 feet above sea level, the boiling point decreases 1 degree celsius

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20
Q

calculating boiling point

A
  1. covert the amount of each solute to moles
  2. add to get total number of moles
  3. adjust for amount of water, find moles per 1000g
  4. multiply moles by 0.52 or -1.86
  5. adjust boiling point for elevation
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21
Q

true solutions

A

ions or small molecules, pass through membranes, very stable, transparent, cannot gel
ex. sugars, salts, vitamins

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22
Q

colloidal dispersions

A

macromolecules or small groups of molecules, pass through filters, moderately stable, translucent, gels
ex. cooked starch, proteins, pectin, cellulose, gums

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23
Q

suspensions

A

large groups of molecules, doesn’t pass through filters, unstable, opaque, cannot gel
ex. uncooked starch, fats/oils

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24
Q

water activity

A

measure of free or available water, more bound water means a lower water activity, determines food stability

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25
glass transition
temp at which a substance changes from a rubbery state to a glassy state, food is more stable
26
importance of acids in foods
taste, appearance, safety, emulsions and foams, gel formation, carbohydrate hydrolysis, leavening, buffering
27
acids and bases
-acids: proton donor (H+) -base: proton acceptor (OH-)
28
pH
negative log of the hydrogen ion concentration pH= -log[H+], [H+]=10^-pH
29
pH of foods
2-3: limes, lots of fruits, vinegar 5-6: meat, lots of vegetables, bread, potatoes, flour, rice 7-8: muscle tissue, egg white
30
weak vs strong acids
weak acids (CH3COOH) have at least one H+ that don't completely ionize and strong acids (HCl) have at least one H+ that completely ionizes
31
total acidity
concentration of ionized and unionized H+, normality, measured by titration with a base
32
active acidity
concentration of ionized H+ at a given time, also known as current pH
33
buffer system
helps to maintain a certain pH, gives you "wiggle room" despite changes in H+ concentration ex. weak acid and its salt
34
carbohydrate structure
if the highest numbered asymmetric carbon has an OH on the left, it's an L-sugar. if there's an OH on the right, it's a D-sugar (most common)
35
alpha vs beta
if an OH is pointing down it is an alpha bond, if an OH is pointing up it is a beta bond
36
disaccharides
sucrose: glucose and fructose maltose: glucose and glucose lactose: glucose and galactose
37
reducing sugars
carbohydrate that can reduce (donate an electron), most simple sugars are reducing sugars except sucrose -browning
38
oligosaccharides
raffinose, stachyose, inulin
39
amylopectin
branched chain, a1-->4 and a1-->6 linkages
40
amylose
straight chain, a1-->4 linkages
41
cellulose
B1-->4 linkages, cannot be digested
42
pectin
a1-->4 linkages, cannot be digested
43
gums
complex polysaccharides that typically impart high viscosity at low concentrations ex. thickener, gel former, source of fiber, starch replacer
44
dietary fiber
non-starch polysaccharides and lingin than cannot be broken down by human digestive enzymes -pectin, cellulose, hemicellulose -also gums and oligosaccharides
45
starch cells
starchy plants have cells with plastids, which contain one or more starch granules -starch granules are microscopic packages of starch molecules
46
birefringence
indicators of crystals in a starch granule, disappears when heated
47
waxy starch
only contains amylopectin, thickens at lower temps, less retrogradation, doesn't gel
48
gelatinization
disruption of the starch granule ex. tea packet reacting with heat and moisture
49
sugar on gelatinization
-granule swelling limited, sugar competes for H2O -decreases thickness, increases gelatinization temp -more resistant to rupture
50
acid on gelatinization
-hydrolyze starch which reduces viscosity -thicker paste
51
salts on gelatinization
not much effect, may increase gelatinization temp
52
fats/surfactants on gelatinization
they can "waterproof" the granules so water can't penetrate, increase gelatinization temp
53
starch retrogradation
partial re-crystallization of starch molecules after gelatinization and cooling -water escaping (staling) -happens more with amylose
54
syneresis
drainage of water from a gel
55
modified starch
-acid modified: prepared below gelatinization temp in dilute acid, low viscosity when heated -cross linked: starch molecules have been cross linked which minimizes breakdown of starch in acid, good for canned/frozen foods -pre-gelatinized starch: starch precooked and dried, used in instant pudding
56
gelation
liquid trapped within a solid network -junctions zones are formed which allows water to be trapped
57
pectic substances and methylation
-protopectin: 100% methylation, water insoluble -pectin: water soluble, varying amounts of acid and methyl esters, methyl groups acting with water, good for gels -pectic acid: 0% methylation, only acid, water soluble
58
methylation
jams: >70% methylation jellies: 50-70% methylation
59
pectin gel formation
1. hydrogen bonding and hydrophobic interaction entraps water to form gel 2. charged groups keep polymers from interacting too closely, which would prevent water from being trapped
60
key pectin gel components
1. pectin: junction zones, forming network, continuous phase 2. water: trapped in pockets within network, dispersed phase 3. acid: protonates carboxyl group, permits pectin-pectin attraction (need 2.8-3.4 pH) 4. sucrose: competes for water, decreases water and pectin interactions (needs 40-70%)
61
sugar free gels
formed with calcium instead, this may need a higher pH
62
gelatin
comes from collagen, a protein in animal tissue -it's solubilized/dispersed in hot water -molecule motion slows as it cools, viscosity increases
63
wheat kernel structure
bran aleurone germ endosperm
64
bran
5% of kernel, cellulose and hemicellulose, removed during milling
65
aleurone
single layer of cells separating the bran layer from endosperm, high in protein and amylase, removed during milling
66
germ
embryo, unsaturated fats, protein, iron, niacin, thiamine, riboflavin
67
endosperm
83% of kernel, starch granules embedded in protein matrix
68
type of wheat depends on
texture, kernel surface color, planting season, end product
69
flour milling
blend > clean > temper (water makes it easier to separate) > break > purify (removes bran) > reduction (flour) > sift
70
flour treatments
1. aging/oxidation: increases S-S bonds so dough becomes stronger and less sticky 2. bleaching: removes yellow xanthophylls 3. enrichment: adds thiamin, riboflavin, niacin, iron, and folate
71
straight vs patent flour
straight has the entire endosperm and typically 72% of kernel. patent has fractions of the endosperm removed and typically 30% of kernel (higher quality)
72
flour classification
1. whole wheat flour: very coarse (bran/germ/endosperm) 2. bread flour: coarse (long patent of hard wheat) 3. all-purpose flour: intermediate (long patent of soft or hard wheat) 4. pastry flour: fairly fine (short patent of soft wheat) 5. cake flour: fine (short patent of soft wheat)
73
pasta
durum wheat milled into semolina, combined with water to make a paste, paste placed in extruder

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