Application of a new spectroscopic method and an alternative roasting process for chocolate production

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Direct analysis of chocolate components by dispersive Raman spectroscopy.

The production of chocolate involves several processing steps including the fermentation of cocoa beans, their roasting, grinding and controlled crystallization. Raman spectroscopy is a technique that provides non-destructive analysis of the chemical composition and molecular structure of samples. However, to date, excitation in the visible and near infrared (532–785 nm) is not possible for dark or milk chocolate due to the product fluorescence.

In this context, the objective of a recent study, carried out by a group of US researchers (Esmonde-White et al., 2023), was to apply this technique in a wavelength range closer to 1000 nm to reduce the fluorescence of chocolate, making the product analysable by dispersive Raman spectroscopy. In particular, the results show that the resulting spectra have sufficient background shrinkage to allow bands to be observed throughout the fingerprint region for cocoa beans and white, milky and dark chocolate.

During the trial, it was therefore possible to conduct qualitative and quantitative analyses to obtain information on cocoa butter and sugar directly from Raman spectra, without further sample preparation. In conclusion, the authors argue that the study defines the experimental basis for future insights involving a larger number of samples to analyse the polymorphism of cocoa butter directly in milk or dark chocolate, without subjecting the product to preparation or extraction steps.

Effect of fluidized bed roasting of cocoa beans on the quality of chocolate.

The extraction of butter from cocoa beans involves several processing steps, among which roasting is particularly critical, which weakens the cell walls. The aim of a recent study, carried out by a group of international researchers (Peña-Correa et al., 2023), was to evaluate the effects of two different roasting processes (forced convective oven and fluidized bed roasting) on the degree of disruption of the microstructure of cocoa nibs and the quality and aroma profile of cocoa butter.

The results show that fluidized bed roasting is 12 times faster than traditional oven roasting. In particular, the first process allowed a rapid release of steam when the parenchyma cell walls were still in a glassy state, while the second process caused gradual physical modification allowing the cell wall to become more elastic. X-ray tomographic analysis showed a total porosity in unroasted cocoa nibs of 8.5 +/- 2.0% (vol/vol), which was doubled upon oven roasting and triplicated upon fluidized bed roasting.

The higher porosity in fluidized-bed-roasted nibs was reflected in the lowest densities and highest cocoa butter yield, which showed a higher presence of pyrazine and 3-methylbutanal, and a lower concentration of hydroperoxides than conventional samples, thus enhancing the chocolate flavour and quality. In conclusion, fluidized bed roasting should be preferred over conventional roasting, for its energy-saving efficiency and for the enhanced quality of resulting products.

References: Esmonde-White et al., Applied Spectroscopy, 77, 2023, 320-326.; R.F. Peña-Correa et al., Journal of the American Oil Chemists’ Society, 100, 2023, 815-827.