RU1825423C - Method of finding acid value of oils and fats - Google Patents

Abstract

Purpose: oil and fat industry, determination of acid numbers of oils and fats under technochemical control in the food industry. A portion of the oil or fat is mixed with an organic solvent containing a weak base in a 10-30 fold excess, and the pH is measured. the standard is added and the pH is re-measured, the difference in measured pH values is set. The acid number is determined by the formula. A 70-85% aqueous ethanol solution is used as an organic solvent. Moreover, the pH of the latter, equal to 8.7-8.9, is provided by the introduction of a 0.20-0.25 M solution of urotropia and 0.1-0.2 M solution of lithium chloride. As a standard, a fixed aqueous solution of acetic or oxalic acid is used. 4 tab.

Description

with

WITH

The invention relates to methods for determining the acid numbers of oils and fats and can be used in process control in the food industry, for example, in the production of vegetable oils.

The aim of the invention is to simplify the method for determining the acid numbers of fats by replacing toxic volatile non-aqueous solvents with a water-ethanol solvent, which at the same time allows the use of an aqueous (fixed) acid solution. At the same time, there is no need to determine the concentration of the standard and its periodic monitoring.

Simplification of the method allows working in laboratory conditions without exhaust devices, and in production conditions it is easy to automate the quality control of vegetable oils.

The proposed method is as follows. A portion of the oil is dissolved in a water-ethanol (75-85% ethanol) solution of urotropine (0.20-0.25 M) + LICI (0.1-0.2 M) under the condition of pH 8.8 ± 0. 1. Measure the pH of the solution (pH i) with constant stirring. Then, a metered amount of a fixed aqueous acid solution is added to the same solution and the pHg is measured. The difference in DR is determined.

The acid number is calculated by a known formula (prototype)

00 ND SP N N3 СО

With

ki

Seth Ust -56.11

g (10 DrN -1)

mg KOH / g

where Set is the concentration of a standard acid solution,

VCT - volume of a standard acid solution, cm3;

g is the mass of a portion of fat, g;

56.11 - mass of mole KOH, g;

And pH is the difference in the pH of the solution before and after entering the fatty acid.

It was established that comparable results with GOST can be obtained using water-ethanol 70-85% ethanol (urotropine solution 0.20-0.25 M) + LIC (0.1-0.2 M) with a conditional value of 8 ± 0.1.

A 0.20-0.25 M concentration of urotropine provides a 10-30 fold excess with respect to the determined acids.

The pH of the initial water-ethanol (70-85% ethanol) solution of urotropine depends on the presence of acidic impurities in the reagent due to the absorption of carbon dioxide from air and varies in the range of 2-8.5. The presence of impurities leads to an overestimation of the result of the analysis, which especially affects low acid numbers. However, due to the use of the water-ethanol system and the urotropin reagent, it was found that the working interval is 8 ± 0.1 and it is much lower than in the prototype method (, 8-12.2). The proposed reagent solution is stable during storage.

The data are given in table. 1, 2 and 3.

From the table. 2 that the use of a solvent with an ethanol content of less than 70% does not allow obtaining comparable results with the standard method due to incomplete extraction of fatty acids from oil.

The choice of the upper limit of ethanol concentration is related to the solubility of the LICI salt added to the reagent solution in order to carry out the complete extraction of fatty acids from vegetable oils. At the same time, salt addition is necessary to maintain a constant ionic strength in the solution during analysis.

, 8 ± 0.1. Ethanol concentration of 80%.

The method is carried out as follows.

Example. 0.51 g of sunflower oil with an acid value of 5.1 mg KOH / g, determined according to GOST, is mixed with 50 cm of water-ethanol (ethanol concentration of 75%) 0.20 M solution of urotropine 0.1 M LICI in a pH meter cell with stirring. Measure pHi. In an example of a pH meter reading after 2 minutes, the pH is 1-7.30. Then, 0.5 cm 30.1 N aqueous fixed solution of acetic acid was added to the same mixture with stirring. Measure pH2. 99

10

pHi-pH2-7.30-6.994), 31

0.5 0.1

0.52 - (100.31 -1)

 5.2mgKOH / g

Data acid numbers are given in table. 4.

The results shown in the table indicate that the error of the method does not exceed ± 10 rel.%. The method is simple in

implementation. Time spent on one definition. 3-4 minutes The method makes it easy to automate quality control of fat in a continuous process using microprocessor technology

Claims (1)

The claims A method for determining the acid number of oils and fats, which involves mixing a sample of the test product with an organic solvent containing a weak base in a 10-30-fold excess, measuring the pH of the resulting mixture, then introducing the standard into it and measuring the pH again, setting the difference the measured pH and determination of the acid number of the test product, depending from the set difference value, characterized in that, for the sake of simplicity, before mixing a sample of the sample of the test product with an organic solvent is introduced into the last 0.20-0.25 M solution of urotropine and 0.1-0.2 M solution of lithium chloride until the organic solvent reaches a pH of 8.7-8.9, whereby a fixed aqueous solution of acetic or oxalic acid is used as the standard, and from a number of organic solvents 70- 85% aqueous ethanol solution. Table 1 table 2 Table 3 Table 4