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 .

…

PURPOSE:

The aim of this experiment is determination of Black point, Sugar content, Color, Total soluble solids, Acidity, and Salt of tomato paste, and discussing our results.

MATERIALS:

Glasses, Refract meter, Funnel, Filter paper, Pipette, Burette, Beaker, Flask, Hunter lab, Bunsen burner,

THEORY:

The tomato is an extremely valuable raw material for a very wide range of processed foods and the demand by the food industries of the world for tomatoes continues at high level. The conversion of tomatoes into tomato paste will be examined in considerable details as this materials now forms an almost standard article of commerce and constitutes a most convenient means of shipping and storing tomato solids in a form which can be readily converted to finished product or food ingredient. In several countries and in international trade it was often referred to as tomato puree until a few years ego. During the transition stage of altering the name from tomato puree to tomato paste several canners and suppliers called the higher concentrations (say 28/32%) tomato paste and the lower concentrations (say up to 26%) tomato puree. This still continues in some circles and in several Regulations and Recommendations still in operation the expression tomato puree is used. The tomato (Lycopersicum esculentum) is, of course, a true fruit, but in view of its association with savory dishes it is seldom eaten as such. It finds major acceptance in the fresh state as a salad component, as a juice which may be consumed fresh or preserved by canning or freezing, it may be peeled and preserved either whole, peeled or even sliced, used as an ingredient in sauces and soups, or completely dehydrated to a powder which, like tomato paste, may be used as a convenient ingredient in a whole range of other food product.

The relative ease with which tomatoes could be crushed and concentrated to form a paste gave rise to some traditional methods of making this material on a domestic basis in those countries where the fruit could be grown as an outdoor crop. The simplest means of producing such tomato pastes consisted of spreading the crushed ripe tomatoes on stone slabs in the hot sunshine, and after concentration by evaporation; the product was mixed with salt and could be stored for use during the winter months. The qualities desired in a tomato to be used in the production of tomato paste may be summarized as follows:

1: It should have a high content of soluble solid.

2: It should posses an intensely red color, not only of the skin but of the entire flesh.

3: The flavor must be good and characteristic, free from scanted and other off-flavors.

During the last twenty years there has been considerable rationalization of methods and equipment employed in the preparation of tomato pulp and its concentration to form the tomato paste of commerce. At the present time the general sequence of operations in almost all factories is basically similar and consists of the following unit phases:

Reception of tomatoes from the fields, washing and sorting, breaking or crushing to form pulp, heating of the pulp, removal of skins and seeds, refining of the screened pulp, concentration of pulp to the desired solids content, filling of finished tomato paste into cans or other storage container.

PROCEDURE:

1: Testing for Black Points: First of all 1 gram of tomato paste was weighed. Then this tomato paste was placed between two pieces of glass. After, the glasses were pressed together and paste made to squash out into a thin film, which could be viewed through the glasses.

2: Determination of Sugar Content of Tomato Paste: 10 gram of sample was taken. Then the sample was diluted to 500 ml. Then 50 ml. sample was filtered from this solution and 50 ml. water was added to this filtered, final solution was completed to 100 ml. than this solution was filled into burette. After that 5 ml. of Fehling1 was placed into flask and 5 ml. of Fehling2 was placed into same flask. Than 10 ml. of solution was added from burette into flask. After, the liquid into flask was boiled. Then, 3 drops of Methylene blue was added as an indicator. And titration was made until the blue color converted to brick-red color. Finally, volume was recorded.

3: Determination of Color: This could be assessed by means of Hunter Lab. Red should be predominant over yellow. An excess of blue may indicate scorching.

4: Determination of Total Soluble Solids in Tomato Paste:

A: By oven drying:

3 gram of tomato paste placed into a dry and weighed dish. Then it was spreaded evenly over the bottom surface. Then the dish content was dried in a vacuum oven at 70°C until constant weight was attained.

B: By Refract meter:

I: Direct measurement: Undiluted tomato paste was put on a refractometer prism. Approximately total solids could be obtained by reference to the tables.

II: Measurement after dilution: One part by weight of the tomato paste was diluted with three parts of distilled water and mixed well. After filtration the refractive index was readed by one drop of filtrate. Finally, the actual solids of the sample could be calculated by multiplying the dilution factor i.e.4.

5: Determination of Acidity: Firstly a 1:3 dilution, by weight, of tomato paste, in which the solid content was known, was filtered. The first few drops may carry though some suspended matter, but this may be returned to the filter. So that, the filtrate for test was as clear as possible. Than 10 ml. of the filtrate was mixed with 50 ml. of water and using 1 ml. of 1 % phenolphthalein and 0.1 N NaOH the titration was made until a pink color persisted at least 30 seconds.

6:  Determination of Salt: First 10 gram of puree was weighed and it was put into a beaker. Then about 90 ml. of water was added to beaker, with the rod, the mixture was warmed slightly and it was transferred carefully to a 500 ml. volumetric flask. Than it was cooled, it was made up to 500 ml. after it was mixed and filtered (A).To 50 ml. of A (=1g of sample), then 5% potassium chromate solution was added. And a piece of marble was added. And this solution was titrated with 0.05Nsilver nitrate solution. Finally, volume was recorded.

CALCULATIONS:

1)   For sugar content; 34 ml. solutions was used.

34ml.→ 51.7 (invert sugar, No sucrose)

(51.7/ 34) * 100 = 152 mg sugar/100ml.

152*10=1520 mg. = 1.52 gr. For ,10 gr.

(1.52 /10) *100 = 15.20 %

Dry matter = 15.20/0.26 = 58 %

2) For total soluble solid = 6.5 Brix      Dilution factor: 4

= 6.5 * 4 = 26 %

3) For determination of acidity = (56.8 * 0.0064) /10 * 100 = 3.64 %

4) For determination of salt = (23.3 * 0.00292)/1 * 100 = 6.81

RESULTS:

Black point: It was not found.

Invert sugar: 34 ml. solutions were used.  And: 58 %

Color: a =25.67         Hunter a / b = 25.67 / 11 = 2.33

           b = 11

           L = 19.73

           Y = 201.6

Brix: 26 %

Salt: 6.81 %,   23.3 ml. solutions were used.

Acidity: 3.64 %   ,   56.8 ml. solutions were used.

DISCUSSION:

     In this experiment we made some tests. Those are determining the quality of tomato paste. In order to conform to certain quality standards the acidity should be fairly low. The NaOH solutions used in the routine examination of tomato products should be accurately standardized before use.

     The texture, size of fibres, presence of black points can be seen and the quality of the paste thereby evaluated. Excessive black rot on tomatoes, indicative of poor sorting or trimming. Black points also occurs presence of foreign matter, burn –on in heat exchangers, damaged screen or cyclone fault.

     The color of the raw tomato is an index of its maturity and this, in turn, is directly related to maximum flavor development. Tomatoes for processing are required at optimum maturity and color forms a useful means of assessment.

     Salts are added to tomato paste to give flavor and for preservation.

     The addition of sugar to tomato paste, as distributed in commerce, is not generally permitted but it may accosionally be required to determine if additional sugar is contained in the course of some manufacturing process, or if a sample has been adulterated.

     Tomato should have a high content of soluble solids for desired quality of tomato paste.

     According to TS; black point is maximum 2/g , we did not find black point, therefore our result convenient to TS. In color determination we found the ratio of a/b as a 2.33 and in TS; this value is minimum 1.8. So; our result convenient to TS. According to TS; reducing sugar is minimum 40 % we found sugar as a 58 %. In TS acidity is maximum 10% of total solid we found the acidity as a 3, 64%. In TS the salt content is 10% of total solid and we found as 6.81%. In TS the soluble solid for puree minimum 11% for double concentrated min. 28% for triple concentrated minimum 36% and we found this soluble solid content as 26%. As a result of the comparison of the values and the TS values; the data show that TAT tomato paste has a good quality and these data show us our experiment was good.

DATA

GROUP	BLACK POINT	INVERT SUGAR %	COLOR	BRIX %	SALT %	ACIDITY %
Tamek B-1	1	59.29	a = 23.33 b =10.46 L=19.18 YI=192.7	28	15.6	6.4
Tat B-2	NON	58.00	a = 25.67 b =11.0 L=19.73 YI=201.6	26	6.81	3.64
Tamek B-3	1	59.2	a = 23.33 b=10.46 L=19.18 YI=192.2	28	14.67	4.16
Tat B-4	NON	57.5	a =25.67 b=11.0 L=19.73 YI=201.6	26	14.82	4.28
Demko B-5	NON	59.30	a = 25.84 b=10.77 L=19.47 YI=203.11	29	14.07	2.7
Home Made B-6	2	67.98	a =22.68 b=10.01 L=18.49 YI=189.84	28	28.67	2.24
Demko B-7	NON	59.0	a =25.84 b=10.77 L=19.47 YI=203.11	29	14.06	2.688
Home Made B-8	2	59.0	a=15.52 b=7.35 L=16.67 YI=158.03	22	5.57	0.448
Tamek B-9	1	61.28	a =22.16 b=10.38 L=19.39 YI=185.24	28	13.76	0.5632