Chemical Rx of Lipids Flashcards
What are three reactions that lipids can undergo?
- Hydrolysis
- Hydrogenation
- Interesterfication
What is hydrolysis?
The splitting of a large molecule into smaller molecules by the oxidation of a molecule of water. Typically requires an energy soucre.
What are the products of hydrolysis?
FFA + Mono/DiGllyerides/Glycerol
What is Hydrogenation?
The addition of hydrogen across double bonds of unsaturated fats.
What is needed to undergo hydrogenation?
A catalyst, typically with Nickel.
Why would you hydrogenate something?
It makes the fat more saturated, leaving it more stable and less susceptible to oxidation.
What are some negative side effects of using hydrogenation?
The creation of trans double bonds.
What is interesterfication?
It a process where you remove all or some of the FA and you reattach them in a new combination.
This is used to alter the crystal formation of fats.
What are the two types of extraction?
- Cold Pressing
2. Chemical Extraction
What is cold pressing?
You take the fat (seed, fruit, bean) and you press it against a press…. LOL
How are cold pressed oils typically consumed?
They are consumed unrefined.
What is chemical extraction?
You use solvents and/or heat to extract the oil.
What has to occur to chemical extraction?
It has to be REFINED.
What does it mean to refine an oil and what are the five steps that occur in refining?
Refining an oil means making it close to pure by removing the water, resins, gums, pigments, etc.
5 Step Process:
- Degumming
- Neutralizing
- Washing and Drying
- Bleaching
- Deodorizing.
What is winterizing oil?
It is the process in which you FRACTIONATE the oil. You remove the highest melting points of the fat.
The fractions that you removed are the crystal formers @ refrigeration temperatures.
What is rancidity?
The deterioration of fats into smaller molecules that typically produce an off flavor or odor.
The longer the fat is __________ the ________ the changes of rancidity.
Stored
Greater
What are the two types of rancidity?
- Oxidative
2. Hydrolytic (Hydrolysis)
What are the two ways that rancidity can occur via Hydrolytic?
- High Heat
2. Enzymes.
How does high heat facilitate hydrolysis?
It breaks the ester bond and releases glycerol acids.
It requires an energy source (which is the heat) and it needs water (from food or suroundings)
As fat breaks down…
FFA ___
Smoke Point ___
Flashpoint ___
Fat color gets _____
FFA increases
Smoke point decreases
Flash point decreases
Fat gets darker and more viscious.
What happens to the glycerol backdown?
It gets broken down via dehydration reaction and gets converted into acrolein.
How do enzymes participate in rancidity?
The specific enzyme Lipase breaks down the fat through a process known as lipolysis.
What can lipase work?
It only work at the oil and water interface
How do to prevent hydrolytic rancidity?
Do not fry at high temps
Shake frost and water off of foods.
Change oil frequently.
Deactivate enzymes.
What is oxidative rancidity?
It is a process that requires very little energy where the double bonds of a FA reacts with oxygen from the environment.
It creates free radicals and produces small molecules that are volatile.
What are the three stages of oxidative rancidity?
- Initiation
- Propagation
- Termination
What four things are needed to trigger oxidative rancidity at the initiation stage?
- Presence of Oxygen
- Light
- Heat (Low Heat)
- Metals (Iron or Copper)
Explain the Initiation stage.
It is a slow process
There is a loss of a hydrogen atom, forming a free radical at the carbon adjacent to the double bond.
Explain the Propagation stage.
It is a quicker reaction that is irreversible and self-perpetuating.
An oxygen molecule combines with the free radical to produce a Peroxy Radical that is very reactive.
The Peroxy Radical then attracts a nearby hydrogen atom, forming Hydroperoxide and a Radical
What are the end products of oxidative rancidity?
There are so many free radicals that they start to reach with one another.
Forming non-reactive species, less reactive species, and polymerization products.
How is oxidative rancidity terminated?
It continues until all the free radicals have been reacted with or with the help of antioxidants. It continues until there are no more double bonds present.
What are seven ways you can prevent Oxidative Rancidity?
- Store in a dark place (in tins)
- Store in a cool place (refrigerator)
- Keep out of oxygen (add nitrogen)
- Add antioxidants (Vitamin E, BHT, BHA)
- Keep oils away from metals (use chelators such as citric acid or EDTA)
- Strain out impurities.
- Add new oil to old oil.
How do antioxidants work?
They donate a hydrogen to the free radical.
Once the antioxidant donates a hydrogen, what is it said to be?
The antioxidant is said to be oxidized.
What are some antioxidants?
Vitamin E or C
Betacaratenes
Flavonoids
BHT (Butylated-hydroxy toluene)
BHA (Butylated-hydroxy anisole)
What are the two ring-structured antioxidants?
BHT (Butylated-hydroxy toluene)
BHA (Butylated-hydroxy anisole)
How do the ring-structure antioxidants work?
They have a benzene ring with double bonds that can be rearranged.
What kind of fats can hydrolytic rancidity take place?
Saturated and unsaturated.
What are the requirements for hydrolytic rancidity?
High energy requirement and the presence of water.
What are two triggers or promotors of hydrolytic rancidity?
- High Heat
2. Enzymes
What is the action of hydrolytic rancidity?
Ester bond is broken by the addition of a molecule of water
What is the end product of high heat hydrolytic rancidity?
Free fatty acids
Glycerol (further deteriorates to acrolein)
Polymerization products
What is the end product of enzyme (lipase) hydrolytic rancidity?
Free fatty acids
Monoglycerides/Diglycerides
Glycerol
What is the result of hydrolytic rancidity?
Off odors and tastes
Decreased smoke point and flash point.
What kind of fats can undergo oxidative rancidity?
Only unsaturated.
What is the requirement or conditions for oxidative rancidity?
Very little energy.
What triggers or promotes oxidative rancidity?
Oxygen
Light
Heat
Metal ions (Fe and Cu)
What are the actions that take place during oxidative rancidity?
Loss of H+ ion – adjacent to double bond
Formation of a free radical
Addition of O2 forming peroxy free radical
Addition of H+ ion forming a hydroperoxide hook
This hook destabilizes the fatty acid chain causing it to break up
What are the end products of oxidative rancidity?
Alcohols
Acids
Aldehydes
Ketones
Polymerization products
What is the result of oxidative rancidity?
Off odors and tastes.
