Impact of sample preparation on physical quantification of filling fats and oils in fresh and stored chocolate
Filling fat and oil migration in filled chocolate products often cause quality loss, such as fat bloom or changes in texture. Therefore, and due to legal restrictions, the detection and quantification of filling fats and oils in chocolate is of interest. Common methods are fatty acid or triacylglycerol (TAG) analysis by GC or HPLC. Additionally, NMR and DSC are used to evaluate migration especially in stored products. Using DSC, the melting and crystallization peak of a filling oil can be detected directly, while NMR turns the reduction of solid fat content (SFC) caused by filling fats and oils to account. However, fat and oil migration is not the only effect during storage, which might affect NMR and DSC measurements. Post-crystallization is also of interest. Therefore, DSC and NMR methods were used to observe and to evaluate the detectable amount over time. Dark chocolate was mixed with hazelnut oil, butterfat, and coconut oil. Samples were stored and analyzed using NMR and DSC. Additionally, methods to destroy thermal history of the sample were investigated. We found that post-crystallization, which occurs during the first 2 wk after production, has a major impact on detectability of filling fats and oils using physical methods. However, standardized sample preparation was successfully applied and amounts below 1 g per 100 g sample were detectable and amounts above 1-2 g were quantifiable with slender time and effort.