Two new processes, laser photoacoustic spectroscopy (PAS) and colorimetry, are outlined by Dóka et al. in the European Food Research and Technology journal.
Benefits: No extraction or chemicals
The researchers claim that these techniques offer benefits over other methods such as high-performance liquid chromatography (HPLC).
“Both techniques are inexpensive and require only a one-time calibration step versus a method capable of absolute concentration measurement (for example HPLC),” said the researchers.
“As no direct method exists to accurately assess the content of cocoa, the two approaches proposed here can turn very useful in practice since the analysis can be completed quickly (without sample preparation) and the use of chemicals.”
Standards for chocolate
Many products made from cocoa liquor carry a label denoting the cocoa percentage which is measured by weight of all ingredients.
For a product to be considered chocolate under the Codex Standard for Chocolate, it must contain at least 35% of total cocoa solids from which 18% is cocoa butter and 14% is fat-free cocoa solids.
Method & Findings
The researchers say the PAS and colorimetry methods could help to identify cocoa concentrations of between 25-50%.
To reach these conclusions they measured the cocoa content of eight commercially available dark chocolates with varying cocoa content reported on the packaging using a homemade photoacoustic spectrometer and a reflection colorimeter.
Non-fat cocoa solids were measured based on theobromine and caffeine in chocolate using an equation. They found detection rates were as effective as HPLC.
“Overall, the limit of detection values obtained in this study are better than those needed in the confectionery industry,” they concluded.
Eur Food Res Technol (2013) 236:963–968
‘Colorimetry and photoacoustic spectroscopy as a suitable tool for determination of fat-free cocoa solids in dark chocolates’
Authors: O. Dóka, E. Prágai, D. Bicanic, R. Kulcsár, Z. Ajtony