Today I tried to review one of Food chemistry Journal due to my preparation for presentation. I found something interesting about Fat Rancidity. Sometimes we dont relized and Put shortenning product like margarine and butter in Kichen without any proper treatment. After few days we found that butter already rancid and cant be used anymore. Based on the Literature that I found, there are 2 kind of Rancidity process which usually happen:
1. first is Hydrolitic Rancidity>>> usually happen when trigliceride react with water andliberate its free fatty acid. this reaction is catalized by lipase enzyme and heat.
example of this reaction is when we put butter in warm kitchen without any special treatment. smell rancid characteristic is resulted from liberation of short chain butiric acid
when we deep fried food with high content of water, rancidity also can happen in oil that we used for friying.
2. Autooxidation or Oxidative rancidity
Autooxidation or oxidative rancidity is predominant type of rancidity. It happen in 3 step (initiation, propagation and termination state) with help from heat, light, metal (iron and copper), enzyme like lipoxigenase. formation one free radical will lead oxidation of many unsaturated fatty acid. this reaction will result volatile compound like aldehyde, volatile fatty acid and ketones. this kind of volatile substance is responsible for rancid odor of fats and oil.
for preventing or delaying rancidity we can avoid situation that catalyst the reaction like:
1. we have to keep fat and oil in cool and dark environment (controlling temperature and light exposure)
2. put or store fat and oil in closed container (minimize oxygen availability)
3. vacuum packaging fat product
4. colour or dark glass storage
5. store away from metal
6. Free copper or ion in cooking utensile
7. inactivity lipoxigenase
Thanks to Allah that make presentation today success…
2012년 5월 8일
영양화학 실험실…