Characterization of the phenolic profile of cocoa (Theobroma cacao L.) processing by-products for their possible use in animal feed

The food value chain is responsible for significant resource and environmental pressures and it is estimated that around 20% of the total produced food is lost or wasted in the EU. The European Circular Economy Action Plan provides a future-oriented agenda for achieving a cleaner and more competitive Europe and in this context, it’s essential to reduce waste and ensure high-quality secondary raw materials [1]. The valorization of cocoa (Theobroma cacao L.) processing waste is arising great interest from both nutritional and functional points of view; through processing, about 80% of the cocoa fruit is discarded [2] and this waste includes cocoa pod shells, mucilages, and bean shells, which contain compounds of interest for various industries, such as the food, cosmetics and chemicals producers [3]. Cocoa beans by-products contain numerous biocompounds, including polyphenols (flavonols, phenolic acids), methylxanthines, dietary fibres and an interesting lipid profile. These compounds make cocoa processing waste an interesting matrix for reuse also in animal feed, in line with the circular economy aim of optimizing available resources and reducing food waste [4]. In this study, we evaluated the possible use of these matrices as ingredients in animal nutrition. The analysis were performed on three samples, S1 (flakes form), SK1 (flakes form) and S2 (pellets), supplied by a Swiss former foodstuff processor and obtained from cocoa bean processing waste, by the application and comparison of some in vitro methods: the Folin- Ciocalteu assay for the evaluation of the total polyphenol content, the DPPH (2,2-Diphenyl-1- picrylhydrazyl) assay for the evaluation of the overall antioxidant capacity of the samples and the vanillin test for the determination of flavan-3-ols; moreover, the antioxidant capacity was evaluated by HPTLC, following derivatization with the DPPH and Fast Blue B Salt reagents. From the comparison of the data obtained with the spectrophotometric methods, the sample showing the greatest antioxidant activity is sample S2 (pellets). This result can be explained by the high concentration of phenolic compounds, measured by the Folin-Ciocalteu assay. This sample also showed a higher content of flavan-3-ols. The S1 and S1K samples showed comparable values in terms of antioxidant activity, total polyphenols and flavan- 3-ols, but lower than sample S2. The results related to flavan-3-ols obtained with the vanillin test show that sample S2 is the richest source of these compounds compared to the other samples. The characterization of the phenolic profile was also evaluated by HPTLC, showing a higher concentration of antioxidant molecules for sample S2 than for samples S1 and S1K, when derivatized with Fast Blue B Salt. These considerations are in line with the results obtained by spectrophotometric methods. By comparing the results, it was possible to obtain an in-depth characterization of the phenolic profile and the antioxidant activity of the cocoa processing waste and to evaluate the potential of these matrices in animal feed. Nevertheless, further approaches will be applied to integrate the results obtained so far and to obtain a more complete characterization of the samples under examination.