Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

FDSC251 (Food chem 1) > Lipids lecture 4 + 5 > Flashcards

Lipids lecture 4 + 5 Flashcards

1
Q

what is knowing the solid fat content important for?

A

to obtain consistent textural characteristics for a fat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

2 ways to determine solid fat content?

A
  1. dilatometry

2. nuclear magnetic resonance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is dilatometry

A

technique based on the measurement of the change in specific
volume (the inverse of density) per unit temperature.

expansion of fat is measured as the temp is changed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

how to calculate the solid fat index?

A

SOLIDS (%) AT 25OC = (X(25)/Y) × 100

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is NMR spectroscopy?

A

nuclear magnetic resonance.

based on the alignment of nuclei that have a spin in an applied magnetic field

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is polymorphism?

A

occurrence of several different crystal forms for a single compound).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are the most common polymorphic forms in order of stability?

A

alpha

beta prima

beta

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is the best TG for chocolate?

A

1-palmito-2-stearo-3-olein and 2-palmito-1-stearo-3-olein

because the temperature for beta prime is closet to body temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

describe crystal forms of different polymorphic forms

A

refer to slides

crystal:
beta = triclinic = no angles or lengths are equal = no symmetry

beta prime = orthorhombic = same angles but different lengths

hexagonal alpha = same angles and lengths

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

describe chain length of polymorphic forms

A

alpha: vertical tuning fork. longest distance

beta prime: tilted tuning fork

beta: stacked chair. shortest distance (most compressed)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

2 transformation of crystal structures?

A
  1. simple collapse
  2. cataclysmic chain shift

(refer to slides)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

2 types of space arrangements of TG crystals?

A
  1. tuning fork form

2. chair form (most likely to be beta)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what are the 4 analytical methods for study of polymorphism?

A
  1. x ray diffraction analyses
  2. microscopic analyses
  3. infrared (IR) spectroscopic analyses
  4. thermal analyses
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

x ray diffraction analyses of characteristics of TG polymorphs?

A

Alpha:

  • hexagonal
  • tuning fork
  • acyl groups oriented at 90 deg to plan of glyceryl group
  • certical chain orientation
  • longest long spacing
  • randomly ordered
  • most loosely packed
  • platelet
  • 5 um

beta-prime:

  • orthorhombic
  • tuning fork
  • acyl groups are tilted 70deg from plane
  • tilted chain orientation
  • intermediate long spacing
  • in between
  • more closely packed
  • fine needle
  • 1 um

beta

  • triclinic
  • chair form
  • acyl groups tilted about 60deg from plane
  • tilted chain orientation
  • shortest long spacing
  • highly ordered
  • most closely packed
  • long needle
  • 25-50 um
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

thermal analyses of TG polymorphs?

A

alpha

  • thermodynamically most unstable
  • lowest mp
  • translucent

beta prime

  • thermdynamically unstable
  • intermediate mp

beta

  • most stable
  • highest mp
  • opaque
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

describe formation of TG polymorphs?

A

alpha
-rapid cooling of liquid fat

beta prime

  • slow cooling of liquid fat
  • polymorphic transformation of alpha form

beta

  • very slow cooling of liquid fat
  • polymorphic transformation of beta-prime
17
Q

steps of conversion from beta to beta-prime of lard

A

interesterification

interesterification and hydrogenation

winterization

addition of cottonseed oil/tallow flakes

[?]

18
Q

why is lard solid even though it has similar composition to veg oils

A
  • high levels of FA in Gs2U and GS3 configuration
  • GS2U = oleoplamitostearin = forms large crystals = grainy texture

-texture can be overcome by interesterification

19
Q

what is interesterification?what is it used for?

A

exchange of FA on the glycerol backbone using heat and a catalyst (ie tin, lead,zine, alkali earth metals)

causes complete randomization of the fatty acid on the glyceride = changes physical properties of the fat/oil WITHOUT forming TRANS FA

use: to remove graininess from lard and to change characteristics of other fats/oils to give other properties

20
Q

what happens if interesterification is carried out at lower temps?

A

more sat long-chain glycerides will fractionally crystallize out

= oil portion becomes more unsaturated = fat portion becomes more saturated

21
Q

what interesterification methods are better for producing highly specific lipids?

A

enzymatic interesterification (using sn-1,3 specific lipase as catalyst)

22
Q

intraesterification vs interesterification?

A

intra: acyl groups exchange positions WITHIN a TG molecule
inter: exchange of acyl groups AMONG TG molecules

23
Q

what are examples of high temp base catalysts?

low temp catalysts?

A

high temp base: KOH and NAOH

low temp: sodium methoxide (NaOCH3)

24
Q

3 steps of the rxn mechanism for interesterification?

A
  1. formation of enolate ion
  2. formation of beta-keto ester
  3. interesterification
25
Q

how is the enulate anion formed in interesterification?

A
  1. alpha proton is removed by base catalyst (ie KOH or NAOH)

2. charge delocalized enulate anion is formed

26
Q

random vs directed interesterification?

A

random:
- carried out at equilibrium conditions
- FA have random distribution among the TG

direct

  • rxn temp is low = when sat TG are produced, they crystallize and are removed from the reaction
  • more saturated glycerides crystallize first
27
Q

what are 3methods of interesterification of lard? what do each of them favor?

A
  1. CML:
    - crystal modified lard
    - favors intramolecule interchange
  2. PML
    - partially modified lard
    - favors random distributions
  3. DIL
    - direct interesterified lard
    - favors directed interesterification
    - can control GS2 content
28
Q

what is enzyme catalyzed interesterification in presence of water used for?

A

manufactor of di and mono GC

emulsifiers

FDSC251 (Food chem 1) (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions