Drying and Fermentation of Cocoa Pod Husk for Increasing Total Crude Protein Content

Abstract

Cocoa bean harvesting for chocolate or cocoa powder yields substantial waste, mainly cocoa pod husk (CPH), 70-80% of total cocoa fruit. Traditionally, CPH is composted at tree bases. Recent analysis shows CPH contains 5.0-6.2% protein, 1.5% fat, 6.7% ash, and 36.6% dietary fiber. CPH can be cheap, protein-rich animal feed, rivaling maize. This study's objective is to elevate the value of cocoa husks, necessitating a focus on their processing to increase utility. To achieve this, a crucial aspect is the drying process, ensuring the final moisture content is suitable for prolonged storage and consumption during periods of scarce animal feed. Additionally, fermentation plays a role in reducing theobromine content, an active compound akin to caffeine in cocoa. This process not only increases crude protein and antioxidants but also renders cocoa husks more fitting for immediate animal consumption. The initial segment delved into cocoa pod drying, commencing with an initial moisture content of 5.40 ± 0.05 kg water/kg dry matter. The CPH underwent drying at temperatures of 50, 60, and 70 °C, employing a ventilation rate of 3 L/mins. To predict moisture alteration rates across temperatures, 12 semi-theoretical mathematical models were utilized. Optimal model selection hinged on statistical values, encompassing reduced chi-square, root mean square error, and sum of squared errors. Among the models, the model by Midilli et al. emerged as the most adept, demonstrating superior response variable variation and the lowest reduced chi-square, mean square error, and sum of squared errors. The effective diffusion coefficient of moisture transfer, as per the Arrhenius equation, ranged from 7.979 x 10–10 to 13.298 x 10–10 m2/s across drying temperatures of 50, 60, and 70 °C. Furthermore, the activation energy for cocoa pod shells was determined to be 70.48 kJ/mol. The subsequent phase involves an experimentation to diminish theobromine content. Fermentation conditions were optimized to augment overall protein composition. A comparison between a molasses-based mixture and an alkaline fermentation process supplemented with Aspergillus N. microorganisms was undertaken. The condition yielding the lowest theobromine content while effectively suppressing antioxidant activity was the incorporation of molasses during fermentation. Through response surface methodology, encompassing fermentation period (7 to 21 days), molasses percentage (0 to 10%), and liquid to solid ratio (0 to 15 ml/g), an experimental design of 17 conditions was established. Mathematical equations provided reliable insights into responses, validated by ANOVA with R2 = 0.9878, R2adj = 0.9804, and p-value < 0.0001. The optimized conditions yielded a peak total crude protein content of 7.93% after 21 days of fermentation, utilizing 10% molasses, and adhering to an anhydrous condition (L/S = 0). Aspergillus.N microorganisms proved instrumental, augmenting digestion, and resulting in elevated crude protein content compared to unfermented cocoa pods. Furthermore, these optimal conditions reduced the theobromine content to 0.58 ± 0.02 mg/100 g dry mass, concurrently heightening antioxidant properties. This renders the fermentation process suitable for the creation of nutritious animal feed. This experimental endeavor successfully heightens the value of cocoa husks through the establishment of a suitable mathematical model for drying and the enhancement of protein content via fermentation. This approach increases beneficial constituents while curbing harmful substances, contributing to both eco-friendly cocoa husk utilization and the potential economic betterment of cocoa farmers.