Application of various methods for determination of the color of cocoa beans roasted under variable process parameters

Dorota Żyżelewicz,Ewa Nebesny,Wiesława Krysiak,Grażyna Budryn

doi:10.1007/s00217-013-2123-6

Dorota Żyżelewicz, Ewa Nebesny + Show 2 more

Open Access

https://doi.org/10.1007/s00217-013-2123-6

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Abstract

Cocoa beans of Forastero variety from Togo were subjected to roasting under either constant or variable process parameters. The variable process parameters were roasting air flow rate, temperature and relative humidity. The color of roasted cocoa beans was determined by pigment extraction under various conditions followed by either their spectrophotometric assays or CIE L*a*b measurements. Also the Maillard compounds index and total polyphenols content correlated with progress of the browning of beans were determined. It was found that an increase in the roasting air relative humidity stimulated formation of brown pigments, while elevated temperature caused worsening of color parameters of roasted cocoa beans. The most suitable method of color characterization of roasted cocoa beans was found to be pigments extraction combined with either separation of their fractions or CIE L*a*b measurements. These assays revealed that cocoa beans roasted under variable roasting air flow rate were characterized by improved color parameters. The relatively simple and inexpensive CIE L*a*b measurements ensured fast analysis of color parameters, while total polyphenols in roasted cocoa beans were quickly estimated by using F–C reagent. Furthermore, quantification of melanoid pigments in roasted cocoa beans can be based on determination of the index of nonenzymatic browning products content, which is relatively simple and inexpensive.

Highlights

Fermentation of cocoa beans followed by their roasting are the two key processes in chocolate manufacturing that decide of its quality
Physicochemical processes that are initiated during fermentation and continued during roasting cause a substantial change in contents of water, volatile acids, tannins and polyphenols as well as in the color, aroma and texture of cocoa beans [15, 18, 31]
Presented in this work methods of color determination have been used to estimate the progress of browning of cocoa beans during their roasting

Summary

Introduction

Fermentation of cocoa beans followed by their roasting are the two key processes in chocolate manufacturing that decide of its quality. Physicochemical processes that are initiated during fermentation and continued during roasting cause a substantial change in contents of water, volatile acids, tannins and polyphenols as well as in the color, aroma and texture of cocoa beans [15, 18, 31]. The roasted unfermented cocoa beans were deprived of the characteristic chocolate aroma and were bitter and astringent mainly due to high concentrations of polyphenols and tannins. The brown and purple color of the unfermented cocoa bean was attributed to the complex alteration products of catechin and tannin [2, 14, 26]. The characteristic brown color of cocoa beans and of chocolate is developed due to the enzymatic oxidation of polyphenols. Too fast drying rate would result in high acidity (retaining an excessive amount of acids, mainly acetic acid), while too slow drying rate would result in low acidity, poorer color and high presence

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