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Validation of a qualitative and quantitative method to determine non-cocoa butter vegetable fats in chocolate

Project Code: Q01094

31/03/2006

Central Science Laboratory
Crews, C

Limits to the composition of chocolate are prescribed in EC Directives which specify the permitted level of addition of non-cocoa vegetable fats and the composition of these fats. The addition of hydrogenated fats to chocolate is not permitted. The level of permitted fats is limited to 5% of the product. Determination of the permitted fats in milk chocolates required accurate and precise knowledge of both the quantity of milk fat and total fat.
This report describes a new method for the detection of hydrogenated fats in chocolate by quantitative determination of the hydrogenated sterol degradation product stigmast-5-ene. The method has been subjected to limited in-house testing which suggested a limit of 0.1 mg/kg for stigmast-5-ene in chocolate fat as evidence of the absence of hydrogenated fats.
Milk fat can be measured by determination of butyric acid, which is found at elevated levels in milk fat compared to most vegetable fats. An alternative method based on the determination of pentadecanoic acid was compared with the butyric acid method. The results showed that the butyric acid method is better than the alternative for measuring milk fat in cocoa butters.
Four procedures for the extraction and determination of the total fat content of chocolate were compared. These were (1) acid digestion followed by Soxhlet extraction, (2) a simple solvent extraction, (3) accelerated solvent extraction, and (4) a destructive automated method based on a fatty acid analyser. The results showed all methods to be variable with the acid digestion/Soxhlet extraction method having the best performance. Each of the non-destructive methods produced equivalent data when the triglyceride profiles were compared.
In-house validation of a method for the detection and quantification of non-cocoa fats in milk chocolate showed that with limited practice non-cocoa fats could be detected with certainty at the 5% limit but could not be quantified with certainty.

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