No abstract

No abstract

This study investigated the kinetics of drying and polyphenol degradation during hot air and sun drying of cocoa beans. Hot air drying was carried out using a constant humidity-controlled (50% relative humidity) oven at temperature range of 60-80C, and sun drying was carried out by exposing the beans under direct sunlight. Several semi-theoretical models were used to model the kinetics of moisture diffusion and it was found that the Page and Logarithmic models were able to provide good prediction. A first-order reaction kinetics was used to predict the polyphenol degradation process with rate constants ranging from 0.011/h to 0.052/h. Activation energy for polyphenol degradation was determined at 8.97 kJ/ mol using the Arrhenius equation. Effective diffusivity during drying was found within the order of magnitude (10 PRACTICAL APPLICATIONSThe understanding of moisture diffusion is important in dryer design especially in the determination of effective diffusivities during drying. Polyphenols are important antioxidants that are beneficial to human health. By investigating the polyphenol degradation kinetics, this helps to link the reactions with moisture diffusion kinetics.

Cocoa beans are widely used in the manufacturing of various food and beverage products such as chocolates, powdered drink, cookies, confectioneries, and others. Processing plays a vital role in governing the final flavor profile of cocoa beans especially during roasting. The current studies aimed to determine the transport properties of cocoa nibs during roasting and also to investigate the quality of roasted cocoa nibs. Cocoa nibs were roasted at temperatures of 120, 130, and 140 8C inside a hot air convective oven. Kinetics analyses showed that overall rates of sensible heating (from T 5 27 to 100 8C) were in the range of 5.1-9.5 8C/min as compared to overall rates of effective roasting (from T 5 100 8C onwards) in the range of 0.9-1.4 8C/min. The observed moisture content profiles followed the typical exponential decay as commonly explained by the Fick's second law of diffusion. The dependency of thermal and moisture diffusivities with temperatures could be described using quadratic and Arrhenius models, respectively. It was determined that the average order of magnitude for moisture diffusivity was 10 210 m 2 /s as compared to 10 29 m 2 /s for thermal diffusivity. High roasting temperature had a negative impact on cocoa polyphenols where greater degradation was observed. Sensory evaluation showed that cocoa liquor produced from the higher temperature treatment (T 5 140 8C) had the highest cocoa flavor. Practical applicationsInformation on the roasting kinetics and moisture/thermal diffusivities are important design parameters for cocoa roaster. Changes in flavor quality during roasting are important in governing the development of flavor in the finished chocolate products. Therefore, the current studies contribute knowledge to the cocoa industry for both equipment and chocolate manufacturers. K E Y W O R D S cocoa roasting, diffusivity, flavor, polyphenols