Quality control in the fats and edible oils industry

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Submitted by azaquar on Wed, 11/05/2011 - 15:19

Introduction

To ensure the quality of oils produced, we must ensure the quality of those products through several checks using the techniques of analytical chemistry and instrumental non-instrumental.

Control of acidity

Definition

The acidity is the amount of free fatty acids expressed as a percentage% oleic acid.

Procedure

  • Taking a test.
  • Add alcohol neutralized as an indicator color.
  • Titrate with sodium hydroxide 0.1 N to turn from blue to purple.

Calculation:

The acidity is given by the following formula:

With:

  • V: volume of NaOH paid ml
  • PM: molecular weight of oleic acid = 282 g / mol.
  • PE: sample in g.

Control of soaps

Definition

It is the determination of alkalinity expressed as sodium oleate.

Procedure

  • Make a sample of oil.
  • Add a known volume of soap solution.
  • Titrate with 0.01N hydrochloric acid until the turn.

Calculation:

With:

  • S: soap content
  • TB: falls in ml burette.
  • PM: molecular weight of sodium oleate = 304 g / mol.
  • PE: sample in g.
  • N: normality

Moisture

Principle

Moisture is determined by weight loss for a sample having spent enough time in an oven set at a temperature of 105 ° C.

Procedure

  • Weigh the tare of a petri dish.
  • Doing the test oil.
  • Put the Petri dish with the sample in the oven.
  • After 2 to 3 hours, the fate of the oven, it puts it in the desiccator to cool.
  • Repeat until constant weight.

Calculation:

With:

  • m1:sample.
  • m2: weight of sample after drying.
  • T: tare

Peroxide index

Definition

In the presence of oxygen in the air, the unsaturated fatty acids in the composition of fats oxidize giving peroxides. This phenomenon occurs during the storage of body fat is rancidity.

The determination of the quantity of peroxide shows fat spoilage by oxidation.

It defines the peroxide as the number of milliequivalents of oxygen per kilogram of body fat.

Principle

The principle of the method based on processing a sample in solution in acetic acid and chloroform, a solution of potassium iodide and titration of iodine with a solution of sodium thiosulfate.

The determination of peroxide is formed indirectly in the presence of potassium iodide.

Procedure

  • Take a test portion of 5 to 10 g in a 250ml bottle.
  • Add 25 ml of mixed solvent (acetic acid + chloroform) and 1ml of potassium iodide
  • Boucher as the bottle, shake for 1 min and 5 min to abandon the dark.
  • Add 75 ml of distilled water, and titrate the liberated iodine by thiosulphate solution 0.01N waving vigorously in the presence of starch, using 0.5 to 1% freshly prepared.
  • Carry out two determinations on two tests taken from the same sample.
  • Conducting parallel and simultaneously in the same way a blank without body fat. If the result of the blank exceeds 0.05ml of 0.01N solution of sodium thiosulfate, new reagents should be prepared.

Expression of results:

The peroxide index is given by the following formula:

With:

  • IP: Peroxide (méq. O2/ kg oil).
  • V: volume of sodium thiosulphate solution used for the test;
  • V0:volume of sodium thiosulphate solution used for the blank;
  • P: sample in grams.

Saponification

Purpose

Determine the number of milligrams of KOH needed to saponifiable 1g fat. The saponification will be higher than the average length of the fatty acid chains is lower.

Procedure

  • Weigh 2 to 3 grams of anhydrous oil and filtered.
  • Add 25 ml of KOH measured.
  • Bring to slight boil, stirring occasionally for 60 minutes.
  • Add 25 ml of alcoholic solution neutralized.
  • Titrate the resulting solution with 0.5 N HCl until the turn phénophtaléine.
  • Perform at the same time a blank test without fat in the same conditions

Expression of results:

With:

  • IS: Saponification value (mg KOH / g oil).
  • V0:volume of the solution of hydrochloric acid for the blank.
  • V: volume of the solution of hydrochloric acid used for the test.
  • P: weight in grams of the test.
  • N: normality of the exact solution hydrochloric.

  Insoluble impurities

Aim

Determine the percentage of impurities from the oil.

Procedure

  • Take 20 g of liquid fat in a 250 ml Erlenmeyer.
  • Add 200 ml of light petroleum solvent.
  • Stir and let stand 30 min.
  • Filter by wattman paper and wash the residue with minimum solvent required to remove all the fat.
  • Dry at 105 ° C until constant weight.
  • The increase in weight of the filter is the amount of impurities present.

Result:

  Determination of fat in the wash water

Purpose

Quantification of fat loss caused by water washing.

Procedure

  • Take a sample of 500 ml in a graduated cylinder.
  • Quantitatively introduce the sample in a light bulb to count down, rinse the piece with a little gasoline.
  • Add a few drops of hélianthine and acidify with a slight excess of HCl or H2SO4, stirring to promote the decomposition of the soap.
  • Add 50 ml of gasoline (Hexane).
  • Stir and let stand until separation of two phases.
  • If an emulsion occurs, add a little brine.
  • Transfer quantitatively the aqueous phase in a second vial containing 50 ml of hexane.
  • Shake and let stand and separate the aqueous phase and extracted a third time with 50 ml of gasoline.
  • Shake and let stand and remove the aqueous phase.
  • Collect all three extracts the essence in a single bulb.
  • Conduct three washes and remove water.
  • Distiller most of hexane in a Soxhlet and drive the last traces in an oven at 105 ° C.
  • Cool in desiccator and weigh.
  • Repeat drying until constant weight.

Result:

With:

  • MG%:% of fat in the wash water.
  • E: Weight of sample taken.
  • M: weight of the fat after drying.

Control of the transmittance

Purpose

Ensure that the color of the oil meets the standards.

Procedure

After the zero setting of the colorimeter by distilled water, to a reading of the transmittance at 420 nm for sample

The standards are:

  • Soybean oil: 78 to 86%.
  • Sunflower oil: 85 to 93%.

Determination of Phosphorus

Definition

This method aims to determine the quantity of esters of phosphoric acid.

Procedure

Step 1:

  • Make a sample of the oil.
  • Add a pinch of magnesium oxide.
  • Set fire to total calcination.
  • Place the crucible in an oven at 570 ° C.
  • Pour 10ml of nitric acid to 7%.
  • Heat for 5 minutes.
  • Transfer the contents of the crucibles in vials of 100 ml, through a filter paper by rinsing with distilled water.
  • Complete the volume with distilled water.

Step 2:

  • Put the beakers in 10 ml reagent nitrovanadomolybdique.
  • Add 10 ml of the solution in the flask.
  • Prepare a cookie: 10 ml of reagent and 10 ml of water.
  • The determination of phosphorus is by spectrophotometry, we put the sample in 2 tanks that parallel in the spectrophotometer, after we put the sample in one of the tanks and follow the instructions given by the device.

Results: The results are obtained by spectrophotometry and expressed as ppm.