Effects of blanching and drying on the production of polyphenols rich cocoa beans and product quality

The high potential of health beneficial polyphenols and antioxidants in cocoa beans has been a major topic for research in recent years. The large-scale application of cocoa beans for health beneficial compounds is relatively unexplored and it needs to be widely utilized by pharmaceutical and nutraceutical industries. Processing methods such as fermentation and drying are major deterrents for recovering high polyphenols in cocoa beans. Hence, it was the intention of this work to introduce the application of hot water blanching pre-treatment and various drying methods for producing polyphenols rich cocoa beans by using unfermented beans. The studies incorporated the application of various drying methods such as oven, adsorption, vacuum, freeze and sun drying methods on cocoa beans. The studies compared the ability of these drying methods to preserve the bioactive capacities namely, total polyphenolic contents and antioxidants activity after hot water blanching. The potential of adsorption, vacuum and freeze drying methods for recovering high polyphenols content are useful in comparing it with the conventional cocoa drying methods such as oven and sun drying methods. For the studies on oven drying of cocoa beans, the drying parameters (T= 60°C, 70°C and 80°C) used were similar to the conventional hot air drying parameters used in industries. The total polyphenolic contents of fermented cocoa beans dried at 70°C was found to be the highest. The polyphenols degradation kinetics for oven drying method of cocoa beans was determined using first-order reaction kinetics model based on various drying temperatures and durations of drying. The studies on drying kinetics of fresh cocoa beans dried using oven, vacuum, adsorption and sun drying methods were successfully analysed. It was found that adsorption drying and vacuum drying methods dried cocoa beans faster than oven and sun drying methods. Two respective falling rate periods were recorded by adsorption and vacuum drying. The effective diffusivities were determined and were found to be in accordance to that of published literatures. Hot water blanching pre-treatment were performed for fresh and fermented cocoa beans (whole beans and half cut). Blanching pre-treatment method was found to show significantly higher total polyphenolic contents when compared with unblanched cocoa samples. The optimal blanching parameter (90°C for 5 min) obtained for fresh beans were subsequently used for experiments involving fresh cocoa beans. The total polyphenolic contents and antioxidant activity of blanched and unblanched cocoa beans were analysed. Results showed that both adsorption and vacuum drying methods showed high recovery of polyphenolic compounds and antioxidants on comparison with freeze dried cocoa samples, which was used as a benchmark in quality analysis of food products. High polyphenols contents were achieved after the blanching and drying treatments and were noted to be significantly higher on comparison with published literatures. Sensory analysis of both blanched and unblanched cocoa beans were analysed after drying using various drying methods. The results for unfermented cocoa beans showed high astringency flavour attributes which further confirmed the high contents of polyphenols in cocoa beans. The cocoa and acidic flavour attributes were recorded to be less owing to the unfermented nature of cocoa beans. The results obtained provides a gateway towards the use of advanced drying technology in cocoa industry. The potential of blanching pre-treatment to mediate high recovery of cocoa polyphenols after drying has been proven through this work. The processing methods used in the current study can be implemented in on-farm cocoa processing, making it a more sustainable farming option.