Week 8 Flashcards
Amylose
Amylose is a molecule that comprises starch molecules. It is not branched unlike amylopectin. It is linear and forms helices. Strong association of hydrogen bonds causes recrystallize when amylose is leached out of a gel and cooled. This creates a stronger gel.
The more amylose in a starch, the darker blue the starch will dye with iodine
Amylopectin
Amylopectin is a highly branched polysaccharide that forms a soft gel upon starch heating. It is a component of starch molecules
Starch granules
A starch granule is comprised of an outer hull or shell with starch molecules inside. The starch molecules, namely amylose and amylopectin, arrange themselves into some form of crystallization bound with hydrogen bonds. These granules are able to take on water and swell as heat is added and the hydrogen bonds break. The outer shell is able to swell to a critical point, after which the granule bursts and it releases some of the amylose starch into solution. Different starch granules have different shapes and swelling behaviors. Some starches like tapioca, can absorb water and swell to the critical point in just cold water without any heat. Other starches like potato starch require heat to absorb water but they create a very viscous solution.
Waxy starch
Waxy starches have lower amounts of amylose in them. They are able to form high paste viscosities but weak gels because there is little to no starch retrogradation.
Normal starch
Normal starches contain mostly amylopectin and 15-30% amylose. These starches usually require heat to swell and paste and can retrograded to form a stiffer gel.
Birefringent
This is the property of polarized light to shine through a starch granule that has not yet burst. When the starch granule does burst, the polarized light behaves differently and refracts off of the broken shell, leaving a shadowed cross on the granules.
Gelatinization
This refers to the phenomenon of polysaccharides, especially starches, forming a solid matrix which traps large amounts of liquids in the interstitial spaces. Some very specific conditions may be requires such as a heated solution, high sugar, low pH, more cations, etc. The process of gelatinization can be thermo sensitive meaning the gel can break down when heat is added after the gel is formed.
Retrogradation
This happens when amylose which has been leached out during the gelatinization process begins to recrystallize as the solution cools. The amylopectin creates a soft gel initially, but the amylose comes in afterwards and can create quite a firm gel. The amylose retrogradation happen quite quickly and soon after a product is made. Amylopectin however can also retrograde but does so much more slowly. This is what happens in break. The junction zones on the amylopectin continually get larger and larger as time goes on and this squeezes out water and dehydrates the product, causing things like bread to go stale.
Gelation/gel
The gelling property of a starch happens first when friction is increased between the swelling granules. This creates an increase in viscosity. The second stage of gelation occurs after the granules begin to burst. The amylose is released and begins to retrograde. The amylopectin also reacts and creates junction zones that form a gel.
Syneresis
This happens during retrogradation where the starch molecules try to recrystallize and cause the junction zones to grow longer and longer; zipping up like a zipper. This causes water molecules to be squeezed out in the process and they then evaporate. This causes the product to dehydrate and separation can occur like with yogurt. It is not usually desirable
freeze-thaw stability
The freeze-thaw stability of a gel refers to its ability to to be frozen and then thawed and still retain its gel structure. Xanthan gum is an example of a polysaccharide that has good structural integrity even after it has been thawed and frozen. this stability relates to the gums ability to retain bonds with itself and other polysaccharides rather than bind with water molecules.
cross-linked starch
+++Cross linked starches are modified starches that have improved thermal stability and strength. The cross linking happens when a polysaccharide polymer is bonded to another polymer.
Stabilized starch
+++A stabilized starch is a starch that has been stabilized using food modification processed. The stabilization is essentially pretreating the starch hull to make sure that it wont break as quickly and unpredictably when it is heated. this leads to predictable swelling and hydration behavior
Acid-thinned starch
+++Acid thinned starches have been hydrolyzed using acids. This results in a starch with less viscosity
Pregelatinized/cold-water swelling starch
Pregelatinized starches are made by swelling the starch granules to the the point where they have become nearly fully hydrated and swollen and then drying them down to a powder. This allows them to take on water when added to cold water and they will thicken those mixtures.
Resistant starch
A resistant starch is a starch that is resistant to being digested. it is insoluble fiber
Fat
Fat is a lipid that is solid at room temperature
oil
Oils are lipids that are liquid at room temperature
Lipid
Lipids are molecules that are hydrocarbons which are hydrophobic. They come in an array of shapes and makeups
Fatty acid
Fatty acids are hydrocarbon chains that contribute to the structure of a lipid. Fatty acids have a methyl end (omega end) and a carboxylic acid end (delta). Can have double bonds within chain to be unsaturated with hydrogens
Monoglyceride/ monoacylglyceride
A monoacylglyceride is a glycerol backbone with one fatty acid
Diglyceride/ diacylglyceral
A diglyceride is two fatty acids on a glycerol backbone. These could be things like phospholipids or hydrolyzed triglycerides
Triglyceride/ tiracyglyceride
Triglycerides are the most common type of lipid. They are a glycerol backbone with three fatty acids. The order of the fatty acids is important to absorption in the body and behavior of the triglyceride.
Glycerol
Glycerol is the backbone that fatty acids area attached to. It is made up of three carbons and adjoining hydrogens. Lone glycerol can polymerize or make a solution more viscous
Phospholipid
Phospholipids are diglycerides which have a phosphate group on the 3 position on the glycerol backbone. The phosphate group makes one half of the glyceride polar and the other two fatty acids make a tail which is non-polar. This allows them to be great emulsifiers.
Saturated
Saturated means there are no double bonds, each carbon is saturated with two hydrogens.
Unsaturated
Unsaturated means that there are one or more double bonds on the fatty acid. These double bonds can have a cis or trans bond angle
Monounsaturated
These have one double bond
Polyunsaturated
These have two or more double bonds. More at risk for lipid oxidation
cis
Bond angle that kinks the fatty acid. This makes the lipid more likely to be a liquid at room temperature and have a lower melting point. They are said to be healthier for the body because they don’t build up as much
trans
Bonds that take on nearly the same structure as a saturated fatty acid. This means they are able to pack tightly together and form a solid fat. The hydrogens are bonded adjacently from one another and that is how the linear form is able to be maintained.
Solid fat content
This related to the amount of saturated or trans fatty acids there are in a product. The ratio of polyunsaturated fats to saturated fats has a large impact on how the fat behaves at room temperature. If there is a high ratio of saturated or trans fatty acids, then the fat will be stiff, firm, and be less susceptible to lipid oxidation than polyunsaturated fats would.
plasticity
This relates to solid fat content, the ratio of solid fat to liquid oil in a fat determines how it will behave and the strength of the emulsion and fat at room temperature.
polymorphism
This describes lipids ability to aggregate in a number of different ways to result in various structures or phases.
crystal morphology
This describes how a lipid will crystalize when it is cooled past its melting point and the behavior of the crystals at that point. The melting point of the crystals, the size, and the tendency to change forms are all important factor to consider with crystal morphology. Another crucial factor for crystal morphology and considering how a crystal with form is the thermal history of the lipid. If the lipid was tempered to have a certain crystal size but is then melted and reformed hastily, the lipid will crystalize into the most stable form which is beta. This is not usually desirable as beta crystals are large and can has negative texture
alpha
Alpha is the smallest crystal form, it is what happens first in the process but it doesn’t last very long. Somewhere in the magnitude of minutes. It will change to beta prime very readily
beta prime
Beta prime is the optimal crystallization morphology to have in food because it is the smallest sustainable crystal size that can be achieved. It does morph into beta after a while but that is on the magnitude of years rather than minutes. The food product can be kept within this crystal morphology for a decent amount of time.
beta
This is the most stable crystal type. It is also the largest and can last the longest.
