Determination of Acidity, Peroxide and Color Test of Fried Oil

FE 376 FOOD QUALITY CONTROL

DETERMINATION OF ACIDITY,PEROXIDE AND COLOR TEST OF FRIED OIL

PREPARED BY:   ŞEYMA MARANGOZ           

MEHTAP KEKLİK

İREM DEMET KODAŞ

DUYGU KÖKALP

EMİNE KÜÇÜKOĞLU

ŞEYMA KURTBEYOĞLU                                                              

SUBMITTED TO:PROF.DR.FAHRETTİN GÖĞÜŞ

WHAT IS THE FRYING?     

WHAT  ARE THE  QUALITY TESTS IN FRIED OIL?

FRYING

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

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

  • Antioxidants

  • 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

burette.

The appearance of pink color indicates the end point

CALCULATION OF ACIDITY EXPERIMENT

                                    Vol. of KOH*2.8

Acidity(%oleic acid)=

                                    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?

Temperature

Oxygen exposure

Light

Moisture

Transition metals,

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)

CALCULATION

                                        V*2.8

Peroxide value =

                               wt of the sample (g)

   V:Consumed 0,002 N Na2S2O3
Color

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.

COLOR

  • 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

CONCLUSION 

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 .


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