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.
How is the inside of the bread kept cooler while in the oven compare to the outside?
Continuous outflow of gas counter-acts the conduction of heat to the inside make the inner part of the bread to never exceed 80 C and does allow it to not loose so much moisture and remain flexible.
What is the structure of bread formed? Hint: the networks that are formed
The protein network by gluten through kneading and the starch network through retrogradation and formation of small crystals that incorporate other starch molecules.
What is the continuous phase in bread
Gluten
Why some particles produces spherical shapes and others irregulars shapes after spray drying.
After spray drying, particles are let on a fluidized bed with warm air flowing upwards. The particle will become to evaporate and loose moisture. Globular proteins will tend to maintain their rigid structure and produce hollow particles. On the other hand, maltodextrin is more flexible and can deform upon volume loss due to evaporation. Maltodextrin indeed will become only rigid close to Tg.
What is the difference between spherical and irregular particles in their bulk density and flowability.
Spherical particle show low bulk density and high flowability and the opposite is true for irregular particles.
How does caking relate to Tg?
Caking is parallel to the line of Tg.
What are fats/oils, antioxidants, flavors, prebiotics and probiotics sensitive to and thus essential to encapsulate them?
Oxidation, oxidation, volatile + interaction with packaging, pH and enzyme hydrolysis and low/high pH respectively.
What are the requirements for spray drying encapsulation?
Active component must be dissolved in a concentration solution of the material for the barrier. Usually, we want the concentration to be as high as possible to reduce evaporation. However, too high concentration can lead to too high viscosities which would not be possible for spray drying. When working with components that are oil soluble the matrix need to be able to stabilize and emulsion. Protein and starch are good option but viscosity would be too high. Therefore, intermidate options like maltodextrin with low Mw than protein/starch can lower viscosity. However this is not a great emulsifier. For this reason emuslfiers are added. However, this lead to lower Tg.
How can a gas be encapsulated?
With pressure. E.g. nitrogen is force into glassified matrix which will retain the nitrogen until dissolve. Nitrogen will be then release and produce foam for cappuccino like.
What is the advantage of extrusion encapsulation over spray drying encapsulation?
You can process more viscous solutions and more suitable for volatile components as less evaporation occurs. However, encapsulates are larger.
What is a drawback of encapsulation by fluid bed drying or drum drying?
Encapsulates are large and not suitable for volatile components as exposed to air for long time.
Which encapsulation method is suitable for hydrophobic components?
Congealing (= co-freezing)
How is Bi and Fo related to thickness?
Bi is proportional (increase with increase size) while Fo become smaller with increase size by square root.
What does Bi show?
The internal resistance over the external resistance
