Oxidation of Food Flashcards
What is oxidation and reduction in Organic Chemistry?
Oxidation - To add oxygen and/or remove hydroden (Higher O:H indicates oxidation)
Reduction - To remove oxygen
Reduction - Gain of hydrogen or loss of oxygen (Higher H:O indicates reduction)
What oxidising agents can be used on primary and secondary alcohols?
Acidified Potassium Dichromate (Orange to green)
Hot Copper Oxide (PH paper - Red to Orange)
What happens to primary alcohols when they are oxidised?
They turn into aldehydes and then carboxlylic acids.
What happens to secondary alcohols when they are oxidised?
They turn into ketones. Thes cannot be oxidised further.
Which one of these can be oxidised further?
Aldehydes. To test, orange acidified dichromate solution turns green
Which oxidising agents can be used on aldehydes and ketones and what do they do?
Acidified Potassium Dichromate - ald- or-gr - ke - N/C
Fehlings Solution - ald - blu-ora - ke - N/C
Tollen’s solution - ald - Silver mirror - ke - N/C
Where does oxidation take place on Oils and Fats?
Along the carbon to carbon double bond.
What does oxidation do to the fats and oils?
It causes degration of long fatty acid chains, leading to the formation of shorter chained products. This leads to fats and oils becoming rancid, which effects the taste. This mainly is due to a free radical process.
How can the rate of oxidation be lowered?
By:
Reducing temp - refridgeration
Reducing O2 exposure - vaccume/insert gas in package
adding antioxidants - most common.
What is a fee radical?
A free radical is a highly reactive species containing an unpaired electron in their outer shell. They are formed by oxidation and result in a chain reaction.
How do free radicals cause food to oxidise?
It removes one electron from another atom in order to become stable, leaving that atom one electron short, so that atom removes an electron fromanother atom in order to achieve stability.
How are free radicals formed?
Formed when a covalent bond is broken by energy supplied by UV light, each side keeps one electron.
What are the three main steps in a free radical chain reaction, and what happens in each?
Step 1 - Initiation - no radicals to two radicals
Step 2 - Propagation - one radical to one radical
Step 3 - Termination - two radicals to no radicals.
