Method for measuring edible oleic acid value based on conductivity

Abstract

The invention discloses a method for measuring an edible oleic acid value based on conductivity, which utilizes a conductivity meter as a detection tool. The method comprises the following steps: when in measurement, fully mixing alkali liquor having a certain low concentration with an oil sample according to a certain mixing proportion; standing for delamination; and then measuring the conductivity of the alkali liquor layer, and predicting the edible oleic acid value through the change of the conductivity of the alkali liquor layer and by using a model. The measuring step is divided into modeling, model verifying, blind sample verifying, model predicting application and the like. The method has simple application without poisonous organic solvents. An oil-alkali mixing proportion can be regulated according to the practical detection requirements so as to meet different acid value measuring scopes and different precision requirements. The method is a novel method for measuring the edible oleic acid value.

Description

technical field [0001] The invention belongs to the field of chemical analysis and detection, and in particular relates to a method for measuring the acid value of edible oil based on electrical conductivity. Background technique [0002] Acid value is an important indicator of edible oil hygienic standards and its quality changes during processing and storage, and it is also a measure for evaluating the content of free fatty acids in edible oil. [0003] At present, the national standard method for the determination of the acid value of edible oil in my country is the acid-base neutralization titration method, including GB / T 14489.3-1993, GB / T5009.37-2003 and GB / T5530-2005. The titration method is to dissolve the oil sample with a neutral ether-ethanol mixed solvent, then titrate the free fatty acids in the oil with a potassium hydroxide standard solution, and calculate the acid value of the oil according to the amount of potassium hydroxide consumed and the quality of the ...

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Problems solved by technology

[0006] ② The amount of oil sample is large, and the titration takes a long time;

[0007] ③ When detecting low acid value oil, its sensitivity and accuracy are low;

[0008] ④ The titration method requires a lot of chemical reagents, and the solution preparation process is cumbersome, which is difficult to meet the needs of rapid on-site detection, and organic solvents are easy to cause environmental pollution;

[0009] ⑤ Potassium hydroxide standard solution is more likely to absorb carbon dioxide in the air, and the generated carbonate will affect the concentration of potassium hydroxide standard solution and cause errors in the measurement results

The colorimetric method is simple and easy to operate, with fast determination speed and good precision, and does not require complex and expensive instruments, but the relative error of the determination results is relatively large

The test paper method has poor stability and low measurement accuracy, which cannot meet the requirements of the national standard

Potentiometric titration analysis is fast and human error is small, but this method is highly dependent on the accuracy of the instrument itself, requiring a large number of oil samples for tedious titration and calibration procedures

Although voltammetry is simple and requires only a small amount of sample to achieve accurate measurement, it needs to select an additive that is sensitive to acidity and easy to measure, and also needs to use flow injection analysis technology, which requires high skill for the measurer

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