Quality assessment/Quality control of edible/cooking oil.

Quality control/Quality assessment of raw materials and products use in edible/cooking oils:

Qualitative analysis :

A qualitative analysis determines the presence or absence of a particular compound, but not the mass or concentration. By definition, qualitative analyses do not measure quantity.

Quantitative analysis :

Gravimetric analysis

Gravimetric analysis involves determining the amount of material present by weighing the sample before and/or after some transformation. A common example used in undergraduate education is the determination of the amount of water in a hydrate by heating the sample to remove the water such that the difference in weight is due to the loss of water.

Volumetric analysis

Titration involves the addition of a reactant to a solution being analyzed until some equivalence point is reached. Often the amount of material in the solution being analyzed may be determined. Most familiar to those who have taken chemistry during secondary education is the acid-base titration involving a color changing indicator. There are many other types of titrations, for example potentiometric titrations. These titrations may use different types of indicators to reach some equivalence point.

CRUDE OIL QUALITY

Crude oil is normally defined in terms of moisture and dirt, phosphatide content normally expressed as ppm phosphorus, free fatty acids (FFA) or acid value and also in terms of color, oxidation characteristics, and trace components such as iron and copper.

*Moisture contents

Temperature 105C and sample 60ml

Initial weight of empty beaker? (W1)

Beaker + sample weight? (W2)

Sample weight =   W2-W1=W?

Weight after heating =W2-W3=W*

Moisture content =    W*/W *100= ?%

Procedure:

Weigh in a previously dried and tared dish about 5 - 10g of oil or fat which has been thoroughly mixed by stirring.

Loosen the lid of the dish and heat, in an oven at 105±10C for 1 hour. Remove the dish from the oven and close the lid.

Cool in a desiccator containing phosphorus pentoxide or equivalent dessicant and weigh.

Heat in the oven for a further period of 1 hour, cool and weigh.

Repeat this process until change in weight between two successive observations does not exceed 1 mg.

*MELTING POINT :

·        Take a sample (oil%Ghee) in capillary  two tubes.

·        Cool the capillary tube with ice.

·        First heat the sample in a beaker and take the sample in capillary tubes.

·        Take cold water in a beaker and put the capillary tube and thermometer in cold water beaker.

·        Start the sprit lamp and turn the light.

·        Shake continuously the water by stirrer when the first bubbles appear in the capillary tubes the sample start motion note the temperature at that point it will be its MP.

*FREE FATTY ACID (FFA*)

Titration method:

·        Take 40ml spirt in flask.

·        Add few drops of 1% phenolphthalein indicator.

·        Start the burette in which the solution of NaOH is present till the color become pink.

·        Then put 11ml sample in the flask and shake the flask well that the pink color disappear.

·        Then heat the flask for 3mint up to 22C in steam bath.

·        Again start the burette in which the (0.01N) NaOH is present till the color become pink  note the length of burette used (ml)

·        FFF% = ml used *0.288 =?

    Or

FFA= (V*N(NaOH)*25.6)/W

Where

V is the volume of NaOH used in the blank sample until the pink color persisted(mL)

N(NaOH is the normality of NaOH

W is the weight of the cooking oil sample(g).

NOTE :    FFA% <0.22.

RANCIDITY TEST :

In routine work apart from the free fatty acids determination, the analysis should include the determination of peroxide value, Kries test and ultra-violet absorption at 234 nm and 268 nm to establish rancidity.

PRESECENCE OF RANCIDITY INDICATION

·        5mL oil sample in flask or test tube

·        5mL conc HCl (hydrochloric acid).

·        0.1% phloroglucinol solution in diethyl ether.

·        Shake the 5ml sample with 5ml of 0.1% phloroglucinol solution in diethyl ether and then add 5mL conc HCl (hydrochloric acid).

·        Alow to stand for 10minutes.

·        A pink color indicates incipient rancidity means if pink color appear the rancidity present and if not appear than not present.

*Per oxide value (PV) :

This is an indication of the extent of oxidation suffered by an oil.

Reagents:

i)                    Acetic acid - chloroform solvent mixture (3: 2). Mix 3 volumes of glacial acetic acid with 2 volumes of chloroform.

ii)                    Freshly prepared saturated potassium iodide solution.

iii)                   0.I N and 0.0I N sodium thiosulphate solutions. Weigh 25 g of sodium thiosulphate and dissolve in 1 L of distilled water. Boil and cool, filter if necessary. Standardise against standard potassium dichromate solution.

iv)                   Starch solution - 1% water-soluble starch solution

 Procedure:

·        Weigh 5 g (±50 mg) sample into a 250 ml stoppered conical flask.

·        Add 30 ml acetic acid chloroform solvent mixture and swirl to dissolve.

·        Add 0.5 ml saturated potassium iodide solution with a mohr pipette.

·        Let stand for 1min in dark with occasional shaking, then add about 30 ml of water.

·        Slowly titrate the liberated iodine with 0.1 N sodium thiosulphate solution, with vigorous shaking until yellow colour is almost gone.

·        Using Add about 0.5 ml starch solution as indicator and continue titration shaking vigorously to release all I 2 from CHCl3 layer until blue colour disappears.

·        . If less than 0.5 ml of 0.1 N Na2S2O3 is used repeat using 0.01 N Na2S2O3. Conduct blank determination ( must be less than 0.1 ml 0.1 N Na2S2O3).

 OR

·        20ml sample of ghee/oil

·        20ml solvent mixture ( 2 vloume (100ml) of glacial acetic acid + 01 volume(50ml) of chloroform

·        10ml of 5% KI solution is given shake before heat

·        Heat for few minutes

·        Few drops of starch solution is added

·        Black color appear

·        In titration flask (burette ) there is Na2S2O3 5H₂O is used till the original (white) color appear

·        The volume used in titration is the Peroxide Value (initial reading  of burette –final reading)

OR

Calculation:

Peroxide value expressed as milli equivalent of peroxide oxygen per kg sample (meq/kg):

Peroxide value = Titre X N X 100/ Weight of the sample

Where,

Titre = ml of Sodium Thiosulphate used ( blank corrected)

N = Normality of sodium thiosulphate solution.

Fresh oils usually have peroxide values well below 10 meq/kg. A rancid taste often begins to be noticeable when the peroxide value is above 20 meq/kg. (between 20 – 40 meq / Kg). In interpreting such figures, however, it is necessary to take into account the particular oil or fat.

Mixture preparation for PV test

(1)              Solvent mixture

2 volume 100ml glacial acetic acid and 1 volume  50ml chloroform.

(2)              5% KI solution

100ml distill water and 5 gm of KI is taken

(3)               Starch solution

500ml distill water (heated) after cooling

Nasheshta or floor(atta) 1to2 spoon is added

(4)              Sodium thio sulfate  (Na2S2O3 5H₂O) solution

3.19gm of sodium thio sulfate

250ml distill water.

*Nickel test :

Reagents

·        Cocentrated HCL  

·        Saturated Bromine Water  

·        0.1% Dimethly glyoxime soluction in 95% alcohol /2% furfural solution in alcohol

·        Nickel Sulphate

Procedure

·        5ml sample oil and ghee.

·        Heat the sample on flame  and ventilation.

·        Some amount of Cocentrated HCL  is added to the sample.

·        Add few drops of furfural solution.

·        Shake the mixture  2 to 3 minutes.

·        Allow the mixture to settle down for about 2 minutes.

·        If pink color appear show that nickel is present.

*SOAP TEST /Saponification test for lipids

*  5mL sample in test tube (oil and ghee)

* Few drops of phenopthlene indicator  .

* Give heat to sample

* If pink color appears soap is present in the sample

               OR

Requirements

Glass ware, test tubes2 ,popette4, beaker 5

Apparatus

Heating mantle, test stand ,watch glass

Chemical

Ethanol NaOH/KaOH 20%w/v

Given sample oil ghee etc.

Procedure

·        Take 0.5ml/0.5gm(soild) of sample.

·        Add 1ml NaOH(20%w/v) to the sample.

·        Add 0.5ml ethanol to sample(ethanol is used to dissolve the fats in the sample).

·        Keep in boiling(hot @100C) water bath for 15 minutes.

·        Take out the test tube after 15 minutes.

·        Keep in test tube stand.

·        Than add 5ml of distil water to test tube.

·        Shake the test for few seconds.

·        The bubble for indicate the soaps.

 Determination of Colour :

Principle:

The method determines the colour of oils by comparison with Lovibond glasses of known colour characteristics. The colour is expressed as the sum total of the yellow and red slides used to match the colour of the oil in a cell of the specified size in the Lovibond Tintometer.

Apparatus:

(a) Lovibond Tintometer

 (b) Glass cells (cell size 0.25 inch, 0.5 inch. 1.0 inch, 5.25 inch or 1.0 cm, 2.0 cm, 5.0 cm as required)

Procedure:

Melt the sample if it is not already liquid and filter the oil through a filter paper to remove any impurities and traces of moisture.

Make sure sample is absolutely clear and free from turbidity

. Clean the glass cell of desired size with carbon tetrachloride and allow it to dry.

Fill it with the oil and place the cell in position in the tintometer.

Match the colour with sliding red, yellow and blue colours.

Report the colour of the oil in terms of Lovibond units as follows :-

Colour reading = (a Y + 5 b R) or ( a Y + 10 b R) in ( * cell)

Where, a = sum total of the various yellow slides (Y) used

 b = sum total of the various red (R) slides used

 Y + 5R is the mode of expressing the colour of light coloured oils; and

 Y + 10 R is for the dark-coloured oils

Although the yellow and red slides required to match the colour shade of an oil in a tintometer are assessed separately, it is found that to a certain extent these slides are mutually compensatory.. Consequently different workers may report different values for the yellow and red units for the same oil and the same workers may report different values for the yellow and red units for the oil examined at different times. To obviate such personal errors a composite factor is used for checking the colour comprising the sum total of the yellow(Y) units and 5 or 10 times the total of red units as specified for the oil or fat.

*Vitman test:

·        Take 100ml oil or ghee sample

·        Give heat for some time

·        Add  few drops of antiamonia trichloride (SBCl3) made in chloroform

·        Blue color indicate the presence of vitamin

Solution:

20%SBCl3 in 100ml chloroform.

*CHEMICAL USED IN EDIBLE OIL lab:

·        Acetic acid glacial (CH₃SO₄).

·        Sulphuric acid (H₂SO₄).

·        HCl.

·        Chloroform (CHCl₃).

·        Ethanol(C₂H₅OH).

·        Ammonium solution 32% (ammonium hydroxide).

·        Potassium hydroxide (pellet).

·        Sodium carbonate (Na₂CO₃) or natrium carbonate.

·         Sodium hydroxide ( NaOH) also called caustic soda (solid form).

·        Sodium thiosulfate (Na₂S₂O₃.5H₂O).

·        Phenolphthalein indicator.

·        Oxalic acid (C₂H₂O₄).

·        Pholoroglucinal( powder form).

·        Methyl orange (C₁₄H₁₄N₃NaO₃S).

·        Antimony trichloride (SbCl₃).

·        Methyl red (C₁₅H₁₅N₃O₂).

·        Potassium iodide (KI).

·        Sprit.

·        Vitamin ( A &D) (0.18ml/T).

·        Starch solution.

Di ethyl ether.