Short communication

Results of preliminary studies on the utilization of cocoa-pod husks in fish production in south-west Nigeria

The extract from Theobroma cacao L, pod husk served as the immunostimulant to enhance the immunity and resistance against Lactococcus garvieae of Macrobrachium rosenbergii. In this study, we employed the injection method and dietary administration method to determine the effect of cocoa pod husk (CPH) on M. rosenbergii. The non-specific immune parameters and disease resistance were evaluated after the prawn injected with 1 μg prawn⁻¹ CPH extract (C1), 3 μg prawn⁻¹ CPH extract (C3), and 5 μg prawn⁻¹ CPH extract (C5) for 1, 3, and 7 days. The results showed a significant increase of total haemocyte count (THC), differential haemocyte count (DHC), phenoloxidase (PO) activity, respiratory bursts (RBs), and phagocytic activity and clearance efficiency to L. garvieae. The non-specific immune parameters, physiological parameters, and disease resistance and growth performance were evaluated after the prawn fed with 1 g kg⁻¹ CPH extract diet (CD1), 3 g kg⁻¹ CPH extract diet (CD3) and 5 g kg⁻¹ CPH extract diet (CD5). The results showed a significant increase in all immune parameters and showed a significant decrease in physiological parameters. No significant difference was observed in growth performance of prawn fed with the CPH containing diet. Both injection and dietary method showed a significant increase in disease resistance against to L. garvieae. We therefore recommend that CPH extract can be used as a immunostimulant for prawn by dietary administration to regulate immune responses, and carbohydrate metabolism lead to enhance resistance against pathogen.

After cellulose, pectin is the most abundant plant polysaccharide. For decades pectins have been industrially produced from two types of raw material (citrus peel and apple pomace, by-products from juice industry). However, it has been demonstrated that several unutilised and discarded wastes from agricultural, agroindustry and food industry have potential to produce gelling pectins in accordance with the purity criteria set by FAO and EU. The increasing demand for natural-based ingredients for materials, food and health pointed out for the need of growing the pectin production.

Cocoa husks were used as the source for the pectin extraction by sugar acid treatment. A full factorial design was applied to screen the independent variables influencing the yield and uronic acid content. Followed by response surface methodology (RSM) was conducted using central composite design to optimize the extraction conditions. The optimized extraction condition was denoted as pH 2.5/95 °C/45 min. The yield and the uronic acid content of the extracted pectin was determined as 4.2 ± 0.12% and 74.5 ± 0.3% respectively. The extracted pectin was proved to be low methoxy pectin (LM pectin) with an 8.1% degree of esterification (DE). The pectin solutions showed shear thinning behaviour which was explicated by Williamson model. This work promotes environmentally friendly technology for pectin isolation.

Variables that influence the citric-acid extraction of pectins from cacao pod husk were examined. A screening study tested the main parameters influencing pectin yield and uronic acid content by a factorial fractional 3³⁻¹ design. Further, response surface methodology was applied using a central composite design to examine the effect of a greater region of variable values on pectin yield and uronic acid content. The yield was optimized by increasing the temperature and time. None of the variables had a significant effect on the uronic acid content, and there was lack of fit of the model to the uronic acid content. From the fitted model, extraction conditions with aqueous citric acid at pH 3.0 for 95 min at 95 °C provided a predicted yield of approximately 9.0 g/100 g dry cacao pod husks. The obtained experimental value for the yield was 10.1 ± 0.3 g/100 g dry cacao pod husks, with the pectins containing 65.1 ± 0.8 g uronic acid/100 g fraction, DE 40.3% and DA 15.9%. At 5 g/100 g aqueous solution, the fraction behaved as a concentrated solution and presented a non-Newtonian shear-thinning behavior, well described by Cross Model. Additionally, the fraction formed gels at acidic pH and high sucrose content.

This study examined variables that influence the nitric acid-extraction of pectins from cacao pod husks. An initial screening study tested the main parameters influencing yield and uronic acid content by a factorial fractional 3³⁻¹ design. Additional studies used response surface methodology using a central composite design. Yield was optimized by increasing temperature. Uronic acid content was higher when pH is decreased and temperature is increased, or when pH is increased and temperature is decreased. To optimize both parameters, extraction conditions of pH 1.5 at 100 °C for 30 min provided a predicted yield and uronic acid content of approximately 9.5% and 80%, respectively. The obtained experimental value for the yield was 9.0 ± 0.4%, the pectin presenting 66.0% uronic acid. Chemical and spectroscopic analyses showed that this pectin is mainly a homogalacturonan highly esterified and acetylated (DE 56.6%; DA 17.1%) with some rhamnogalacturonan insertions.

The influence on growth performance and digestibility of cocoa-pod husks mixed ration at either 100 or 300 g kg⁻¹ was studied using growing French White rabbits. Except for feed consumption, results indicate there was no significant difference in final body weight, weight gain and feed conversion efficiency among rabbits receiving both levels of cocoa-pod husks in their rations. A slight decrease in energy digestibility, however, was observed when crude fiber contents increased, especially, in the ration incorporated with 300 g kg⁻¹ cocoa-pods husks.