Determination of acid value in food

Acid value is a sign of free fatty acid content in fat. During the long-term preservation process, fat is slowly hydrolyzed by the action of microorganisms, enzymes and heat to produce free fatty acids. Therefore, acid price can be used as one of the criteria for measuring fat quality. The acid value can be used as an indicator of the degree of hydrolysis in fat production, and can also be used as an indicator of rancidity during food preservation.

GB5009.229â€”2016 The determination of acid value in foods stipulates three methods for determining the acid value of various foods. Let us look at the different scope of application of these three methods :

|The first method: cold solvent indicator titration

Applicable to edible oil samples that can be completely dissolved into a clear solution by cold solvent at normal temperature

7 kinds of edible vegetable oil (except chili oil), edible animal oil, edible hydrogenated oil, shortening, margarine, creamer and vegetable oil

| Second method: automatic solvent potentiometric titration

An edible oil sample that can be completely dissolved into a clear solution by a cold solvent at room temperature, and a fat sample extracted from an oil-containing food

Edible vegetable oil (including chili oil), edible animal oil, edible hydrogenated oil, shortening, margarine, butter cream, vegetable oil, fried snack food, puffed food, baked food, nut food, pastry, bread, biscuit, oil Fried instant noodles, sauces for nuts and seeds, dried fish products, cured meat products, chili sauce with edible oil, 19 categories

|The third method: hot ethanol indicator titration

Edible oil sample that cannot be completely dissolved into a clear solution by cold solvent at normal temperature

There are 6 types of edible vegetable oil, edible animal oil, edible hydrogenated oil, shortening, margarine and vegetable butter.

Due to the variety of grease samples, the standard appendix describes the steps and requirements for sample preparation:

Sample category	Sample status	Approach
Edible fat	Liquid at room temperature and clear liquid	Direct sampling
	Liquid at room temperature, with impurities, non-clarified, moisture content	Appendix A: Removal and Dehydration Drying
	Normal temperature solid state	Appendix B: placed in a water bath or a constant temperature drying oven about 10 Â° C higher than its melting point, heated to complete melting and sampled
	Emulsified processed edible oil	Appendix C: Solvent Leaching - Rotating Evaporation
Vegetable oil	NA	Grinding according to Appendix D - Soxhlet Extraction - Rotary Evaporation
Oily food	Less hardness (such as fried foods, puffed food, bread, cakes, etc.	D.1 ordinary crushing
	Soft or have some fluidity (such as stuffing, peanut butter, sesame sauce, etc.)	D.2 ordinary minced
	High hardness (such as animal aquatic products, cured meat products, etc.)	D.3 freeze smash
	Prepackaged food with seasoning oil package (fried instant noodles)	D.4 Smashing of prepackaged foods containing seasoning oil packets