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YR2SEM1 > FOOD2150 Set 4 > Flashcards

FOOD2150 Set 4 Flashcards

1
Q

What is water used for in nutrition?

A
  • hydrolysis of large molecules
  • some produced by oxidation of small molecules and water found in foods
  • need sufficient water to dilute waste components
  • to get rid of excess electrolytes
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2
Q

What are the biological functions of water?

A
  • cellular structure (muscle, membranes, skin): healthy, turgid cells
  • nutrient transport: throughout body
  • lubrication: saliva, tears, hip, etc joints
  • metabolism: for reactions (digestion, breaks macronutrients down)
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3
Q

What happens if we do not drink water?

A
  • die in 4 days
  • can be toxic in excess (too low blood solute concentration)
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4
Q

What increases need for fluids?

A

alcohol, cold, fiber, diseases, heated environments, high altitude, medications, activity, etc

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5
Q

What is obligatory water loss?

A

amount needed to dilute solutes from diet (mainly salt and urea)

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6
Q

What is urine production like with water?

A
  • max amount we can conc.
  • kidneys filter blood, reabsorb -99% of passing water
  • osmotic and hormonal control
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7
Q

What is amazing about water?

A
  • dissolves more substances than any liquid
  • freezing point lowers as amount of salt dissolved increases
  • expands (by 9%) when frozen (why ice floats)
  • if salt is poured in water: volume decreases
  • boils at high temp (100C)
  • extremely high surface tension (non-covalent interactions with other H2O)
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8
Q

Why does methane have a lower BP compared to water?

A
  • tetrahedral (groups with 4 VE) (no dipole movement), symmetrical, weak van der waal’s forces
  • water has a large dipole moment since it has a bent molecular geometry
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9
Q

What is cohesion?

A
  • the action or property of like molecules sticking together, being mutually attractive.
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10
Q

What is adhesion?

A

tendency of dissimilar particles or surfaces to cling to one another

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11
Q

What is the uses of water in agriculture?

A
  • application of a pesticide/herbicide
  • transports nutrients
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12
Q

What is the uses of water in agriculture?

A
  • hydration
  • why we add surfactants to emulsions
  • why gels/dough exists
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13
Q

What is the uses of water in nutrition?

A
  • Water is the transport molecule of the blood
  • Allows NaCl and sugars to be soluble
  • Due of small size O2 is soluble
  • Solubilization of proteins and carbohydrates
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14
Q

Describe water and its symmetry

A
  • Bent configuration (asymmetry) of water
    (bond angle 104.5)
  • Water has no net electric charge, one side is
    positive and the other is negative
  • Strong dipole moment
  • Hydrogen Bonds (12-30 kJ/mol)
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15
Q

What is water’s high latent heat of vaporization and fusion and heat capacity used for (agr,fs,nut) ?

A

AGR: Evaporative cooling to protect enzymes in plants
FS: steam as a heating medium in processing plants, an energy intensive process to heat and cool foods
NUT: removes lots of heat energy when it evaporates

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16
Q

How does changing the temperature of water modify the dipole moment, and what does this cause?

A
  • changes the hydrogen bond length which is correlated with the hydrogen bond strength
    increase in the hydrogen bonding:
  • increased cohesion, density (down to 4oC), viscosity
  • decreased adhesion, density (from 4 to 0 oC), thermal conductivity
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17
Q

What is water’s nanostructure?

A
  • Strong Cohesion
  • Strong Adhesion
  • High Boiling and melting points
  • High latent heat of vaporization
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18
Q

What is water activity?

A

measure of the availability of water molecules to enter into microbial, enzymatic and chemical reactions
* Bound water is unavailable for reactions
* Capillary water is somewhat available for chemical reactions
* Free water is available for chemical reactions
* More predictive of shelf-life than measuring total water content of a food

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19
Q

What are the two types of water?

A
  • water binding-bound water
  • water holding-entrapped water
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20
Q

What is water binding-bound water?

A
  • molecular interaction of water with solutes (sugars) and ions
    (salts).
  • “hydration”
  • Water bound to solutes behave differently than “bulk” water.
  • molecularly immobile or unavailable
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21
Q

What is water holding-entrapped water?

A
  • entrapment of water in a gel by high-MW molecules such as
    proteins and polysaccharides in a way that prevents water from flowing and from being “exudated”.
  • Entrapped water, free or capillary water behaves, like pure
    water and maintains its molecular availability and mobility.
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22
Q

How does water’s large dipole moment disrupt electrostatic interactions between ions dissolving them?

A

-Negative ends of the water dipole (oxygen-free electron pairs) will orient themselves towards cations and positive ends of the same dipole (hydrogen atoms) will orient themselves towards anions.
- forms a “hydration sphere” about one layer deep around the ion, water in this sphere is called “bound water”.
- Bound water can form hydrogen bonds and this “structures” the
water several layers removed from the hydration sphere.

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23
Q

How can we calculate water activity?

A

measured instrumentally by determining Equilibrium Relative Humidity (ERH)
= ERH(%)/100

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24
Q

Describe hydration (bound, visceral) water

A

water molecules associated directly with food macromolecules (exchangeable, not covalently or H- bonded)
* gives macromolecules their structure
* not available for microbial growth nor chemical reactions
* it does not contribute to product deterioration
* present even in dry foods, e.g., powders

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25
Q

Why does water content vs water activity differ?

A

identity vs concentration
- 2 molecules dissociate have greater affect on Aw
- doesn’t deterioate: carb; binds water better than protein

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26
Q

Describe trapped (capillary) water

A
  • ~ 5% of the total water in a food, may be much more in tissue products like leaves
  • associated with cellular and tissue structures - not easily pressed out
  • can be removed by drying
  • does not support microbial growth but provides a“moist” texture, e.g., dried fruits or capillary water in vegetables, meats
    3) Free Water
  • can be 90% + of the water in a food (e.g. orange juice)
  • available for both microbial growth & chemical reactions
  • easy to remove (just squeeze or press) out of product
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27
Q

Describe the phase diagram of water

A

Can exist in three physical states (very
unique)
* Gaseous, Liquid and Solid
* Both pressure and temperature may
be manipulated to change the physical
state of water
* Used in evaporative drying, freeze drying,
boiling,
*phys chem supercritical fluid graph

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28
Q

How are frozen foods stable during freezing?

A

some microbial survival
- physical: ice formation
- chemical: cryo-concentration

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29
Q

How are frozen foods stable during storage?

A

no microbial growth
- physical: recrystallization, sublimation
- chemical: slow reactions

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29
Q

How are frozen foods stable during thawing?

A

some possible microbial growth
- physical: drip loss
- chemical: decompartmentalization

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30
Q

When happens to the H bonds when water freezes?

A
  • decrease in density
  • liquid water, each molecule H-bonds to 3.4 other water molecules
  • in each, each water binds to 4 others
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31
Q

What happens when water crystallizes?

A
  • preserves the tetrahedral “structure” of liquid water
  • crystallizes into an “open structure” that is less dense (91 %) than the liquid state
  • ice formation can disrupt tissue structure
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32
Q

Give examples of colligative properties

A
  • vapor pressure lowering (Raoults’ Law)
  • boiling point elevation (Candy thermometers)
  • freezing point depression (ice cream)
  • osmotic pressure (Nutrition and processing)
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32
Q

What are colligative properties of solutions?

A
  • properties that depend upon the concentration of solute molecules or ions, but not upon the identity of the solute
  • BP elevation, freeze-concentration
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32
Q

What makes water a highly structured liquid?

A

When ice melts, only 15 % of hydrogen bonds are broken which
explains why the latent heat of fusion (333kJ/kg) is small
compared to the latent heat of vaporization (2230 kJ/kg).

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33
Q

Describe the colligative property of freeze-concentration

A
  • solute concentration and molecular weight
  • Freezing causes a concentration effect of solute molecules in a reduced amount of unfrozen water
  • occurs when viscosity is so high, sugar molecules can no longer arrange in crystal lattice: become stuck: freeze
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34
Q

Describe glassy amorphous states

A
  • rapid cooling increases viscosity rapidly, crystallization is impossible
  • high viscosity makes it behave like a solid
  • metastable, supercooled liquids (not true solids)
  • difficulty of directly addressing glass behaviour (long time to attain because of high viscosities)
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35
Q

Give examples of glasses in foods

A

pasta, powders, instant coffee, hard candies, sugar in chocolate, boiled sweets
- pure sugars form a glass, pure sucrose will not form one; important in confections
- amorphous like water: disordered, no molecular order (you can see through)
- form due to high viscosity

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36
Q

What is molecular mobility

A
  • kinetic approach to food stability
  • excellent predictor of food stability
    because deteriorative reactions occur very slow
  • exceptions: reactions that do not depend on diffusion (free-radical oxidation)
37
Q

What are glass transitions characterized by?

A
  • glass transition temperature
  • higher molecular weight: higher glass transition temp
  • glass achieved by increasing concentration or lowering water content, particularly of high molecular weight materials, and/or lowering temperature
38
Q

What are the two types of emulsions

A

“dispersed phase” in “continuous phase”
- water-in-oil (butter, lard)
- oil-in-water (mayo, salad dressing)
- Hydrophobic phase is insoluble in the hydrophilic phase
- Requires an amphiphilic molecule to remain stable

39
Q

How do we destabilize oil-in-water?

A
  • hydrophobic phase is insoluble in the hydrophilic phase and without an emulsifier separation occurs spontaneously
40
Q

What are types of oil-in-water emulsion destabilization?

A

creaming, phase separation, coalescence, sedimentation, time, flocculation, Ostwald ripening, phase inversion, partial coalescence

41
Q

What is stokes’ law?

A
  • particles rise; creaming
  • particles fall; sedimentation
41
Q

How does emulsion destabilization occur?

A
  • differences in density between continuous and discontinuous phases
  • differences in droplet sizes (Laplace pressure inside droplet)
42
Q

Compare small and large droplets during destabilization

A
  • smaller droplets have greater internal pressure causing an increase in solubility of the dispersed phase
  • Large droplets grow at the cost of smaller droplets
43
Q

How can we make emulsions more stable?

A
  • adding proteins
  • proteins sit at interface (hydrophobic and hydrophilic groups)
  • when it arrives at interface, protein unfolds and exposes hydrophobic section to oil (philic to water)
43
Q

How do emulsifiers use amphiphilic molecules?

A
  • resides at interface between water and oil
  • Reduces the interfacial tension or unbalanced H-bonds
  • Stabilizes an emulsion preventing separation
44
Q

What is the HLB (hydrophilic lipophilic balance) equation?

A

HLB= 20 x Mh/M
Mh: molar mass hydrophilic portion
M: molar mass

45
Q

What are colligative carbs?

A

monosaccharides (pentose, hexose)
disaccharides (a-nomer, b-nomer)

46
Q

What are noncolligative carbs?

A
  • oligosaccharides (3-9 sugars)
  • polysaccharides (10+ sugars) (homo (same subunit), hetero (dif. subunit)
47
Q

What are the rules for the Fischer projection for linear sugars (monosaccharides)?

A
  • Draw the carbon chain vertically
    (carbonyl group at the top)
  • Vertical lines are below the plane
  • Horizontal lines are above the plane
  • Carbon numbering of the sugar always
    starts at the most oxidized group (i.e.
    the carbonyl group)
48
Q

What are enantiomers

A
  • isomers that are related by a reflection operation/mirror plane
49
Q

What are stereoisomers?

A
  • isomers that differ in the 3-dimensional arrangement of atoms (from a molecule) in space.
50
Q

What is configuration?

A
  • arrangement of stereogenic centers
  • set at synthesis and is changed during chemical reactions
51
Q

What is conformation?

A
  • arrangement in space
  • how the sugar orients itself due to the rotation of single bonds
  • physical phenomenon
  • temperature, pH dependent
  • dictates the physical properties of sugars
    and the reactions they partake in
52
Q

What occurs during the formation of a ring structure?

A
  • new chiral center
  • previously achiral carbonyl carbon is now
    chiral and can assume two configurations (α- and β-)
53
Q

What is the process of interconversion between the α- and β- forms called?

A
  • mutarotation
  • a and b are anomers
  • As long as this hemiketal or hemiacetal group remains, cyclization remains reversible (this is called a reducing sugar)
54
Q

What are reducing sugars?

A
  • preserves the hemiacetal group
  • Glucose, galactose, fructose, lactose
  • Undergoes Maillard reaction
  • Undergoes caramelization
55
Q

What are non-reducing sugars?

A
  • No hemiacetal group
  • sucrose
  • Does not undergo Maillard reaction
  • Undergoes caramelization
55
Q

What is the maillard reaction?

A
  • Reducing Sugar (glucose) + Protein (free amine) form Schiff base (shifting e- to become more stable)
  • A series of molecular rearrangements
  • Degradation productions (molecule shortens: aldehydes, carboxyls)

Important end products include:
- Melanoidins (pigment) (conjugated rings/double bonds)
- Flavours (breakdown products)

55
Q

What is acrylamide?

A
  • from Maillard reaction products
  • class 4 carcinogen
  • attempts to minimize asparagine or other proteins to prevent maillard
  • released by thermal treatment of certain AA in combo with reducing sugars and of early Maillard reaction products (N-glycosides)
56
Q

What is caramelization?

A
  • Browning reaction observed by the heating of both reducing (glucose) and non-reducing sugars (sucrose) in the absence of amine-containing compounds
  • similar to the Maillard reaction, but requires higher temperatures and low pHs
  • sucrose needs to be hydrolyzed
57
Q

What are the steps of the Maillard reaction?

A
  1. amadory rearrangement and product
  2. Strecker degradation
  3. cyclization
  4. polymerization (really dark brown: cyclic compounds from large, unordered polymers)
58
Q

Describe the steps of maltodextrin and high fructose corn syrups

A

most sugar from corn: high in amylose and amylopectin
1- liquify: viscosity reduced, (treat w alpha-amylase), breaking starch from oligosaccharides to disaccharides
2- saccharification: colligative properties develop, reduced viscosity, increased sweetness

59
Q

Describe maltodextrin

A
  • saccharification
  • DE value
  • high DE: sweet taste
60
Q

What is the DE (dextrose equivalent) value?

A
  • indicates the degree of hydrolysis of starch into glucose syrup
  • percentage of the total solids that have been converted to reducing sugars
  • higher DE: more sugars, less present dextrins
  • glucose syrups above 55 DE termed to high starch conversion
  • 35-55 DE: regular conversion (drinks)
  • below 20: products of hydrolysis are maltodextrins
61
Q

What are HFCS?

A
  • Corn starch that has undergone saccharification, High DE glucose syrup is processed by glucose isomerase to convert some glucose to fructose
  • Sweetener (cheaper than cane sugar), excellent water binding
  • Corn sweeteners control freezing point in ice cream and frozen confections, and extend shelf life by limiting microbial growth.
62
Q

Describe oligosaccharides

A
  • specific type of sugar
  • modifications to sugar
  • anomeric carbon-hydroxyl bond angle important for digestion
  • which carbons are bound together
  • no viscosity, no colligative properties: not very useful
63
Q

Describe polysaccharides

A
  • linear, branched or cross-linked biopolymers consisting of monosaccharides (>10 monosaccharide units covalently bonded together)
  • The structural diversity is limitless
64
Q

Describe homopolysaccharides

A
  • degree of polymerization from 100-100000
  • digestible: glycogen (more branched), amylopectin (less branched), amylose
  • indigestible: cellulose, b-glucan, inulin
65
Q

Describe the amylose of starch

A
  • Linked together by (1→4) bonds
  • Starch content is typically 15 to 25 %
  • Degree of polymerization can be anywhere from
    100 to 10,000
  • one reducing end, one non-reducing end
  • The unbranched nature of amylose, the –OH
    groups can form intermolecular hydrogen bonds
    with other –OH groups
  • Amylose-amylose interaction reduce solubility
66
Q

Describe the amylopectin of starch

A
  • Highly branched polymer of (1→4) bonds and
    branched by non-random, evenly spaced α-(1→6)
    bonds
  • Branch points occur every 20 to 25 glucose residues
  • Mol weight between 1 million to 1 billion g/mol
  • Branched nature makes intermolecular hydrogen
    bonding difficult.
67
Q

Describe the makeup of starch

A
  • exists as large particles called granules (2um-100um)
  • granules composed of amylose and amylopectin
68
Q

What is starch functionality attributable to?

A
  • gelatinization (loss of molecular order)
  • pasting (disruption of the starch granule)
  • retrogradation (starch polymers (amylose) forms intermolecular hydrogen bonds and may recrystallize)
  • graph
68
Q

How is starch an important food polysaccharide?

A
  • Digestible by humans (source of energy)
  • contributes to the texture of foods
  • Certain indigestible starches behave like fiber (resistant starches) and fermented by gut bacteria as a prebiotic
69
Q

What is pectin?

A
  • hemicelluloses found in the middle lamella of
    plant cell walls
  • found in fruit peels and vegetables
  • most complex hemicellulose polysaccharides ( consists of two main polymers covalently linked: smooth galacturonans t1 and hairy rhamnogalacturonans t2)
  • pKa 3.5
70
Q

What is low-methoxy pectin?

A
  • less than 50 % of galacturonic acid –COOH groups methoxylated
  • low pH- between 2.8 and 3.2
  • 65-70% sugar to bind water so it will not interfere with hydrogen bonding
71
Q

Describe extracted and graded pectin

A
  • Most pectin when extracted has a degree of
    esterification between 50-80%
  • Pectin are “graded” according to the degree of methoxylation/esterification
71
Q

What is high-methoxy pectin?

A
  • More than 50 % of galacturonic acid –COOH groups methoxylated
  • Sugar CANNOT be be added so we don’t get the dehydration of pectin
  • pH above 3.5 causing ionization (strong electrostatic repulsion
  • Add a source of Calcium (Ca2+)
72
Q

What are the challenges with pectin and the good and bad?

A
  • issue when extracting juice so pectin enzymes used to increase juice yield and to clarify juices, orange juice settles
    GOOD:
  • Pectin contributes to the viscosity of tomato products
  • Pectin stabilizes juices that exist as colloidal dispersion
    BAD:
  • Endogenous pectin enzymes break down pectin and decrease viscosity of tomato products
  • Destabilizes juices that exist as clouds
72
Q

Where are most predominant carbs?

A
  • absorbed in digestive tract:
    glucose, fructose, galactose
  • Derived from digestion of disaccharides by brush border enzymes
  • derived from digestion of glycemic polysaccharides
73
Q

What are glycemic carbs?

A
  • Are available for metabolism (provide energy and
    glucose)
  • Sugars (glucose, maltose, sucrose)
  • Starches (Amylose, amylopectin, maltodextrins,
    glycogen
74
Q

What are non-glycemic carbs?

A
  • Are not hydrolyzed/absorbed in the small intestine (Fiber)
  • Insoluble: cellulose, hemicellulose
  • Soluble: glucan, pectin, locust bean, alginates, carrageenan, guar
75
Q

What are the methods of diffusion on the surface of the microvilli?

A

facilitated (luminal side), passive (luminal side), passive (capillary side)

76
Q

Describe facilitated diffusion on the luminal side

A
  • Na+ & energy dependent (ATP) secondary active transport (SGLT-1 symporter)
  • Transports Glucose & Galactose
77
Q

Describe passive diffusion on the luminal side

A
  • Facilitated diffusion via GLUT-5
  • Transports fructose
78
Q

Describe passive diffusion on the capillary side

A
  • Facilitated diffusion via GLUT-2
  • Glucose, galactose, fructose transport
78
Q

What is GLUT4?

A
  • dominant regulator of whole-body glucose homeostasis
  • Few physiological parameters are more tightly regulated in humans than blood glucose
  • major cellular mechanism that diminishes blood glucose when carbohydrates are ingested is insulin-stimulated glucose transport (GLUT4) into skeletal muscle
79
Q

What is type 1 diabetes?

A
  • IDDM (insulin dependent diabetes mellitus)
  • “juvenile onset”
  • where absorption of glucose must be assisted with insulin
79
Q

What is type 2 diabetes?

A
  • NIDDM (Non-insulin dependent diabetes mellitus)
  • “adult onset”
  • insulin resistance, less effective
  • associated with diets high in sugars and starches, obesity.
  • fiber may have a protective role
  • 90% of diabetes incidence in Canada is Type II
80
Q

What happens on the surface of the microvilli?

A
  • absorption (transport of glucose, galactose, fructose across epithelial cells)
  • conversion (liver converts fructose and galactose to glucose)
  • regulation (insulin regulation of glucose)
81
Q

What are the steps of acid hydrolysis in carbohydrate metabolism?

A
  • The food enters stomach where it is known as chyme.
  • pH of the stomach inactivates salivary amylase
  • There are enzymes but not involved in carbohydrate digestion
  • Major morphological changes (changes the microstructure of the food)
82
Q

What does pancreatic amylase do in carbohydrate metabolism?

A
  • produces dextrin of various lengths, short oligosaccharides (maltotriose), maltose and limit dextrins, which are branch points in amylopectin
83
Q

What should be our primary carb source?

A
  • starch (amylose, amylopectin)
  • how much maltose is produced effects how much glucose can be absorbed.
84
Q

What is glycemic index?

A

area (food) / area (glucose)
- based on the blood glucose raising potential of a food
* Foods are compared to glucose at an equivalent glycemic carbohydrate concentration
- total carb composition of a food is not a good indicator of nutritional character
- GI designed to indicate the physiological function of the carbs coming from a particular food
- sucrose (92), glucose (138!!), fructose (32)

85
Q

Give a study testing glycemic index values

A
  • .Carbohydrate portions of three unprocessed foods (boiled rice, sweet corn, and potato) and six
    processed foods (instant rice, Rice Bubbles, corn
    chips, Cornflakes, instant potato, and potato crisps)
  • In six healthy volunteers who ingested 50 g
    carbohydrate portions of the above foods the
    processed foods produced a higher glycemic index (p< 0.05) in all but one instance.
  • The exception was potato crisps which gave a similar glycemic response to boiled potato.

YR2SEM1 (10 decks)

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