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food chem 1 > 4 Polymorph Conversion > Flashcards

4 Polymorph Conversion Flashcards

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1
Q

what are the methods for converting beta to beta-prime?

A
  • interesterification
  • interesterification & hydrogenation
  • winterization (destearinization)
  • addition of cottonseed oil/tallow flakes (beta-prime)
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2
Q

what is intEResterification?

A

exchange of acyl groups on the glycerol backbone between triglycerides w/a catalyst (eg Sn, Pb, Zn, alkali earth metals)

1,2,3 –> 2,3,1

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3
Q

what’s the purpose of interesterification?

A
  • randomize FA distribution to change properties without forming trans FAs
  • removes graininess in lard
  • enzyme catalyzed can make mono/diglycerides used as emulsifiers
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4
Q

how is interesterification carried out?

A
  • under low temps

- more saturated long chain FAs will fractionally crystallize out

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5
Q

what is the process in which fats are interesterified to result in random distribution of FAs called?

A

randomization

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6
Q

what catalyst should be used to create a FA with a SPECIFIC composition when doing interesterification?

A

enzyme (lipase)

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7
Q

how can human milk structure be replicated artificially?

A

interesterification using sn-1,3 specific lipase

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8
Q

what is intRAesterification?

A
  • acyl groups transferred WITHIN triglycerides

- can change the FAs present on an individual TG

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9
Q

what catalysts are used for low/high temp interesterification?

A

low: KOH, NaOH
high: NaOCH3 (sodium methanoxide)

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10
Q

what are the steps of the interesterification mechanism?

A

1) formation of enolate ion
2) formation of beta-keto ester
3) interesterification

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11
Q

how is randomized interesterification achieved?

A

rxn is carried out to an equilibrium condition

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12
Q

how is directed interesterification achieved?

A

fat must be crystallized during the reactions. trisaturated glycerides crystallize first

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13
Q

what are the products of interesterification of lard called?

A
  • CML: crystal-modified lard (intRAmolecular)
  • PML: partially modified lard (random dist)
  • DIL: direct interesterified lard (directed)
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14
Q

what properties of oils can be altered through changing polymorphs?

A
  • air incorporation
  • plasticity
  • consistency
  • solid-liquid ratio
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15
Q

what’s the air incorporation and consistency of BETA PRIME polymorphs like?

A
  • lots of small bubbles

- smooth

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16
Q

what’s the air incorporation and consistency of BETA polymorphs like?

A
  • large air bubbles

- grainy/waxy

17
Q

which polymorph is most preferred in baking?

A

beta prime

  • most small air bubbles = largest volume & consistency
  • promotes tenderness
18
Q

what’s responsible for “cocoa bloom?”

A

the conversion of beta-prime FAs to beta FAs

19
Q

what is tempering?

A

transformation of FAs to a desired polymorph. accomplished through meticulously controlling temperature during melting/cooling

20
Q

does randomization improve or worsen the plastic range of lard?

A

improve

21
Q

define plasticity

A

changes in consistency as a function of temperature

22
Q

define consistency

A

apparent hardness at a temperature

23
Q

how is it possible that we can make margarine high in PUFAs and free of trans fats?

A

interesterifying a blend of liquid oil and completely hydrogenated oil

24
Q

what commodities are of greatest interest to a food science when working with fats?

A
  • shortening
  • margarine
  • confectionery fat
25
Q

what do shortenings do?

A
  • reduce elasticity of dough (cuts gluten)

- increases flakiness

26
Q

shortening power increases as degree of unsaturation:

A

increases

27
Q

does hydrogenated veggie oil or lard make better shortening?

A

functionally, they’re about the same. however, lard is grainier but this can be fixed with interesterification

28
Q

what can margarines be made of?

A
  • hydrogenated fats
  • mixture of hydrogenated fats & unhydrogenated oils
  • mixture of interesterified fats & unhydrogenated oils
  • mixture of unhydrogenated fats
29
Q

what are the 3 most stable margarine blends?

A

1) 75% co-randomized (40% coconut oil, 60% palm oil)
2) 10% co-randomized (50% coconut, 50% hydrogenated canola oil)
3) 15% hydrogenated soybean oil

30
Q

how is margarine made?

A
  • mixture is plopped into a SSHE which partially solidifies the material
  • mixture is then tempered for optimal plasticity/spreadability
31
Q

what must be done during tempering to avoid melting and a later conversion to beta crystals?

A

removal of heat of transformation

32
Q

what’s the TG composition of the cocoa butter?

A
  • 20% SOS
  • 50% POS
  • 5% POP
s = stearic
o = oleic
p = palmitic
33
Q

cocoa butter has a (narrow/wide) melting point range

A

narrow

34
Q

randomizing palm kernel oil does what to its melting point and texture?

A
  • decreases melting point (from 46°C to 35°C)

- less waxy

food chem 1 (12 decks)

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