4 Polymorph Conversion Flashcards
what are the methods for converting beta to beta-prime?
- interesterification
- interesterification & hydrogenation
- winterization (destearinization)
- addition of cottonseed oil/tallow flakes (beta-prime)
what is intEResterification?
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
what’s the purpose of interesterification?
- randomize FA distribution to change properties without forming trans FAs
- removes graininess in lard
- enzyme catalyzed can make mono/diglycerides used as emulsifiers
how is interesterification carried out?
- under low temps
- more saturated long chain FAs will fractionally crystallize out
what is the process in which fats are interesterified to result in random distribution of FAs called?
randomization
what catalyst should be used to create a FA with a SPECIFIC composition when doing interesterification?
enzyme (lipase)
how can human milk structure be replicated artificially?
interesterification using sn-1,3 specific lipase
what is intRAesterification?
- acyl groups transferred WITHIN triglycerides
- can change the FAs present on an individual TG
what catalysts are used for low/high temp interesterification?
low: KOH, NaOH
high: NaOCH3 (sodium methanoxide)
what are the steps of the interesterification mechanism?
1) formation of enolate ion
2) formation of beta-keto ester
3) interesterification
how is randomized interesterification achieved?
rxn is carried out to an equilibrium condition
how is directed interesterification achieved?
fat must be crystallized during the reactions. trisaturated glycerides crystallize first
what are the products of interesterification of lard called?
- CML: crystal-modified lard (intRAmolecular)
- PML: partially modified lard (random dist)
- DIL: direct interesterified lard (directed)
what properties of oils can be altered through changing polymorphs?
- air incorporation
- plasticity
- consistency
- solid-liquid ratio
what’s the air incorporation and consistency of BETA PRIME polymorphs like?
- lots of small bubbles
- smooth
what’s the air incorporation and consistency of BETA polymorphs like?
- large air bubbles
- grainy/waxy
which polymorph is most preferred in baking?
beta prime
- most small air bubbles = largest volume & consistency
- promotes tenderness
what’s responsible for “cocoa bloom?”
the conversion of beta-prime FAs to beta FAs
what is tempering?
transformation of FAs to a desired polymorph. accomplished through meticulously controlling temperature during melting/cooling
does randomization improve or worsen the plastic range of lard?
improve
define plasticity
changes in consistency as a function of temperature
define consistency
apparent hardness at a temperature
how is it possible that we can make margarine high in PUFAs and free of trans fats?
interesterifying a blend of liquid oil and completely hydrogenated oil
what commodities are of greatest interest to a food science when working with fats?
- shortening
- margarine
- confectionery fat
what do shortenings do?
- reduce elasticity of dough (cuts gluten)
- increases flakiness
shortening power increases as degree of unsaturation:
increases
does hydrogenated veggie oil or lard make better shortening?
functionally, they’re about the same. however, lard is grainier but this can be fixed with interesterification
what can margarines be made of?
- hydrogenated fats
- mixture of hydrogenated fats & unhydrogenated oils
- mixture of interesterified fats & unhydrogenated oils
- mixture of unhydrogenated fats
what are the 3 most stable margarine blends?
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
how is margarine made?
- mixture is plopped into a SSHE which partially solidifies the material
- mixture is then tempered for optimal plasticity/spreadability
what must be done during tempering to avoid melting and a later conversion to beta crystals?
removal of heat of transformation
what’s the TG composition of the cocoa butter?
- 20% SOS
- 50% POS
- 5% POP
s = stearic o = oleic p = palmitic
cocoa butter has a (narrow/wide) melting point range
narrow
randomizing palm kernel oil does what to its melting point and texture?
- decreases melting point (from 46°C to 35°C)
- less waxy
