FE 376 FOOD QUALITY CONTROL
DETERMINATION OF ACIDITY,PEROXIDE AND COLOR TEST OF FRIED OIL
PREPARED BY: ŞEYMA MARANGOZ
İREM DEMET KODAŞ
SUBMITTED TO:PROF.DR.FAHRETTİN GÖĞÜŞ
WHAT IS THE FRYING?
WHAT ARE THE QUALITY TESTS IN FRIED OIL?
Frying is the cooking of food in oil or another fat, a technique that originated in ancient Egypt around 2500 BC.
Frying is used to improve quality of taste and consummability of the food.
Deep frying is a cooking method in which food is submerged in hot fat, most commonly oil.
Deep-frying is a cooking process, with which water containing foodstuff is immersed into edible oils or fats at temperatures between 140 – 180 °C.
In the first phase, within a few seconds, a thin crust forms, whose structure crucially affects the deep-frying process and the quality of the food with regards to fat absorption and crispness.
Factors Affecting the Quality of Oil during Deep Frying
Replenishment of fresh oil
Frying time and temperature
Quality of frying oil
Types of foods
Types of fryer
Dissolved oxygen contents in oil
PHYSICAL AND CHEMICAL PARAMETERS OF FRYING OIL
DETERMINATION OF ACIDITY OF FRIYING OIL
WHAT IS THE ACIDITY?
Acidity is a result of hydrolysis of oil from the triglyceride structure.
WHY DOES ACIDITY INCREASE ?
Free fatty acid is an important index for oil quality and shelf life of the oil
Acidity increases as free fatty acids occur from the hydrolysis of oil.
The increase in free fatty acids means that oxidation stability decrease
It is one of the important indicators for that rancidity of oil will start
PROCEDURE OF ACIDITY
Weigh 5 g of oil and transfer it into 300 ml conical flask
Add 50 ml of alcohol -ether solution to the oil solution
At the end of the dissolution add 1 or 2 drops of phenolphthalein indicator.
Titrate this against the 0.1 N KOH solution from the
The appearance of pink color indicates the end point
CALCULATION OF ACIDITY EXPERIMENT
Vol. of KOH*2.8
wt of sample (g)
DETERMINATION OF PEROXIDE IN FRYING OIL
The most common test for the determination of oil oxidation is peroxide value (PV).
It is a parameter representing the extent of oxidation
WHAT IS THE PEROXIDE ?
Peroxide is a compound that formed from triglyceride and not stable.
Oil oxidation is an undesirable series of chemical reactions involving oxygen that degrades the quality of an oil.
WHICH PARAMETERS EFFECT PEROXIDE VALUE?
PROCEDURE OF PEROXIDE VALUE
Weigh 3,5 g of oil and transfer it into 250 ml erlenmayer flask
Add 30 ml of chloroform-acetic acid solution to the oil solution
Add 1 ml of KI into solution
Wait 5 min this solution at dark environment
After waiting,add 75 ml of distilled water and 1 ml starch
solution.(If dark color is observed,solution has peroxide)
Titrate this against the 0.002 Na2S2O3solution from the burette
until the red color observed.(brick red)
Peroxide value =
wt of the sample (g)
V:Consumed 0,002 N Na2S2O3
Color formation in oils during frying is one of the most noticeable degradation reactions that occur in the frying oil.
To control the condition of the natural color of the pigment in the composition of the oil.
To control the bleaching process perform correctly.
Different oils darken at different rates
Oils with more natural anti-oxidants will darken more than oils with lower levels of natural anti-oxidants
Protein products caused both the fastest darkening and thermo-oxidative deterioration of the frying oil.
HOW TO COLOR MEASURED?
The HunterLab L*,a*,b* commonly used in the food industry.
The systems measure the degree of lightness (L),
The degree of redness or greenness (+/-a), and
The degree of yellowness or blueness (+/-b).
ACIDITY AND PEROXIDE VALUES ACCORDING TO TSI
Acidity increases depending on the frying time which causes the rancidity in oil. Result of the rancidity unpleasant odor and flavour occurs.
Peroxide shows variability depending on the time.
L value of color is different for standards.This may stem from added some sunflower oil during frying process.
EFFECTS ON HEALTH
Reusing oil is that can create free fatty acids, ketones, aldehyde etc. which cause ailments in the long run
This type of frying oil indicate mutagenic and carcinogenic effects which are caused the health problems .