Chocolate Flashcards
What is the continuous phase of chocolate
fat is the continuous phase
T or F : chocolate is an emulsion
true, an emulsion of solid particles in a fat continuous phase
What is the goal of the milling step in cocoa processing?
the goal is to reduce the particle size
What is the goal of the conching step of cocoa processing
the goal is to reduce the viscosity by adding fat that will reduce the contact between the particles by coating them
what is the effect on viscosity of too small particles from the conching step
increasing the viscosity because there will be contact between the cocoa particles
what is the state of sugar inside the cocoa bars
both crystalline and amorphous sugars are present
What is the glass transition temperature
temperature at which there is a transition of the sugars from the glassy to the rubbery state
T or F : the amourphous state of sugar in chocolate bars is unwanted
false, the amourphous state as place for the flavour particles
When there is a decrease in the heat flow in DSC this means that the process is :
endothermic (requires energy)
When there is an increase in the heat flow in the DSC this means that the process measured is :
exothermic (releases energy)
What is the enthalpy of transition
the amount of heat needed to melt the crystalline state and gives indication on the volume fraction of crystalline state sugar
What is the heat capacity ?
it is the heat needed to from the glassy state to the rubbery state
What is the form of sugar crystal that you want in your chocolate bar
the amorphous state is wanted because it retains the flavour particles and because it can take some water
what can happen to the sugar when the temperature is above 70˚C
the sugar can go from amrphous retaining the water to crystalline and so this results in a release of the water
What are the main TG of cocoa butter
- Oleic 38% (unsaturated)
- Stearic 35% (saturated)
- Palmitic 24% (saturated)
why would a chocolate manufacturer add milk fat to is chocolate
to make the chocolate softer because lower melting point of milk fats
why are milk fast softer than cocoa butter fats
because they are between 4C to 16C while cocoa butter has most of his TG with chains over 16C
In chocolate, whey proteins of milk will ___ the viscosity
increase because they stay in the continuous phase
in chocolate, casein proteins will ___ the visocisty
decrease because they are surrounding the sugar particles and so they give.a lubrification effect of the sugar particles
what are the various crystal form of cocoa butter and what ar their shape
When the unsaturated FA is in the middle of the TG, the mp will be ___
decreased
What is the eutectic temperature
temperature at which there is both crystals osf A and B at the same melting temperature
what are the polymorph of cocoa butter
T or F : the beta prime (Bv) is the most stable polymorph of cocoa butter
false, it i the BVI but the transition from beta prime (BV) to BVI is really slow
what are the different properties of the various polymorps of cocoa butter
describe the temperature cycle in tempering
What is undertempering ?
when the temperature is changed too fast leading to fast crystal formation and so unstable crystals
What is over temper?
heating is not sufficient and or cooling not fast enough and so formation of too much crystlas and decreases the strenght of the network
T or F : the compositiion of a chocolate doesn’t tell you anything about the rheology of the chocolate
true, ti is more abiout the processing steps and conditions
What are the two models to explain the flow behaviour of chocolate
- Casson
- Herschel-Bulkley
What will determine the flow behavior of a chocolate
- The amount of particles
- The connectivity between the particles
What is a the yield stress of a chocolate
the yield stress determinate the moment that the choco starts to flow and so it is the heat or the stress you need to apply to have a flow.
Yield stress is ____ (not affected / affected ) by the fat content
not affected (1 is 30% fat and 2 is 32% fat)
Viscosity is ___ (affected / not affected) by the fat content
affected
Yield stress is ___ (affected/not affected) by the particle size
affected (1 = small particle and 2 = coarser particles)
Viscosity is ___ (affected/not affected) by the particle size
not asffected
What are the different factors important for the flow properties of chocolate
- Tempering
- Amount and type of fat
- Particle size
- Particle size distribution
Why is lecithin used in chocolate?
to increase the flowability of the particles inside the continuous phase : reduce the viscosity
What is the problem you can encouter if you add to much lecithin to a chocolate
Making the particle hydrophilic because of a bilayer of surfactant this would increase the viscosity because the particles are larger
What happens with time if you have a filled chocolate that with a center of hazelnut or liquid oil
softening of the hard layer because of melting point of fat reduced by the mixing and hardening of the center because of oil migration
What are the strategies to prevent fat bloom?
- Addition of hard fat between the inside and the outer layer
- Addition of an anti-bloom fat with a high melting point (stearine)
- Addition of high melting milk fat fraction
- Addition of fat crystal of the same shape as polymorph V (behenic acid)
- Addition of amorphous sugar.
What are the various possibilities reason you could have fat bloom
- Incorrect precrystallization
- By age (form V to VI)
- Melted (in sun) and recrystalized
- Migration of soft fats
For dipping chocolate you want ____ yield stress and ___ viscosity
low yield stress
high viscosity to prevent driping
For enrobing, you want ___ yield stress and ___ viscosity
low yield stress
viscosity should be low so that you have the enrobing effect
What can you do to make a chocolate more enrobing
low viscosity is wanted so you could add more fat
What can you do in order to make a chocolate good for dipping
adding lecithin because it decreases the yield stress without changing too much the viscosity
What is the trick to have nice freezable chocolate
using chocolate that are untempered so that it is in form I and II which are softer or increase the fat content to reduce the melting point
Why cna you see some water particles on top of chocolate in the frezer
because f the contracting effect pushing water molecule outside
T or F : SL is less for a bonbon with alcohol center
yesbecause it can migrate more since less hydrophobic
what are the various form of micelles you can have?
surfactants / emulsifiers with small tails and big head are suitable for ___ emulsion
oil in water because more water and head is hydropholic
When a surfactant / emulsifier has a long tail, it is more suitable for ___ emiulsions
water in oil because the tail is hydrophobic
a high HLB number means that the emulsifier is hydro__
hydrophilic, more suitaable for oil in water
a Low HLB number means that the emulsifier is hydro__
hydrophobic so more suitable for a water in oil emulsion
Lecithin has a ___ HLB number and it is suitable for ___ emulsions
low, so it is hydrophobic and so more suitable for water in oil emulsions
Lecithin has a preference of (w/o or o/w) emulsions while proteins have a preference of oil in water emulsions
lecithin : water in oil
proteins : oil in water
What are the two ways to induce a phase transition
- addition of an emulsifier
- change of the continuous phase fraction (water or oil content)
Can you explain the phase transition diagram
When you are at the first line and then you add little bit more water (second red line) were you will go depends on the ingredients you have : if you have a lot of lecithin you would still be in a water in oil emulsion but if you have a lot of proteins than you would be in a oil in water emulsion because the proteins are high HLB meaning that they are hydrophilic.
Can you explain the microstructure of ganache
in a ganache, the cocoa particles are not disolved so they are still in the dispersed phase and now the water and sugar are the continuous phase because the sugar is soluble. Now the fat is dispersred and the so rheological porperties like viscosity depends on the volume fraction of fat.
