Chapter 2 Flashcards
Is a glass a vitrified liquid?
Yes
Does water crystallize faster than carbs?
Yes, because water is smaller than carbs. Smaller molecules require less time to orient to form a crystal lattice. Oils and proteins also take long.
Can gelatinized starch crystallize?
Partly. Indeed, gelatinized starch is considered a biopolymer, and like other biopolymers, it can partly crystallize.
What are the y-axis and x-axis of a phase diagram?
Y= temperature and x= water or solid content (%)
is the eutectic point found in food
no
If a carb is heat at high temperature can it form a gel?
No because the granules break and starch has dissolved.
Are carbs more soluble at high or low temp.
High temp.
What is the effect of alcohol on water freezing point?
It reduce the freezing point of water, that is why you can store limoncello in the freezer or any high alcohol percentage liquors.
Is a liquid dense or does it contain ‘holes’?
It contains holes or free volume which are spaces in between molecules which are larger than average and cause by random motion.
Effect of reduce temperature on viscosity
Number of sufficiently energetic jumps is reduce and the amount of space to accommodate molecules that have jumped has become less. So increased.
What that the WLF equation show?
The change in viscosity compare with the viscosity at the glass transition temperature. This is mainly applicable for sugar solution of 30%> as for lower the glass transition is so far that Arrhenius equation is better.
Will a short or long chain have a higher glass transition temperature?
Longer the chain the higher the molecular weight and the less freedom of movement there is resulting in higher Tg temperature.
How are the WLF and the diffusion coefficient related?
As the viscosity rises very quickly in the WLF area the diffusion coefficient decreases to extremely low values approx 0 in the glassy state.
What does the Gordon-Taylor equation tell?
Describes the new glass transition obtained from a mixture as long as K is known.
What is meant by plasticization?
Plasticization is the large reduction in glass transition temperature upon the addition of a low molecular weight product (with low Tg) to a product with high Tg.
Why some product semi-crystallize and others do not?
The once that do not have their melting temperature very close to the glass transition temperature and therefore cannot reach crystallization point without being vitrified first.
Can globular protein semi-crystallize
Yes and no, but since they do not unfold and expose the groups that should crystallize then they must crystallize as a whole. This can take a very long time. So technically we do not experience proteins to be able to crystallize
What are the three types of crosslinking that can occur?
Small crystal connect different chains in semi-crystalline biopolymers, chemical as S-S bridges and physical e.g entaglement.
Effect of a filler at low conc and at high conc. on the packaging density?
At low it will be linear following Einstein equation while at high it will start to interact and will not be linear any more resulting in maximum packaging capacity.
What is the difference between making fondant and hard candy?
Fondant -> sucrose solution is heated to 110-120 and gently cooled down to 45 giving a creamy sugar paste.
Hard candy -> sucrose solution and corn syrup. Dissolve sugar with heat and then heat to 140 degrees. This when cooled down enters glassy state.
Are crystal made by more than one component?
No, they are made by pure components.
Is a crystalline or glass structure more stable at higher relative humidity?
A crystal, as glass is very hygroscopic.
Why are crystals not good to encapsulate flavors?
Because crystals expel flavor which would then reside in between the crystals and therefore would be experience at the start of the tasting. However, once all flavors are gone the experience of the sweet is unpleasant.
Why is corn syrup used in the making of hard candies?
Corn syrup, which is ultimately, fructose, has higher Tg compared to sucrose and lower crystallization temperature compared to sucrose. This allows crystallization to be prevented.
