Abstract :
[en] Côte d’Ivoire, the world’s leading producer of cashew nuts with an estimated output of 1.5 million tons in 2025, aims to strengthen its local processing capacity and enhance the value of this strategic agro-resource. While cashew nuts receive significant industrial attention, the cashew apple remains largely underexploited despite its considerable nutritional, functional, and nutraceutical potential, and a biomass nearly ten times greater than that of the nut. The solid residue generated from cashew apple juice extraction known as cashew apple bagasse (CAB) is one of the most abundant by-products of the cashew industry, particularly in tropical regions. This makes CAB a promising raw material for the development of high-value natural ingredients.
The general objective of this thesis is to develop an innovative valorization strategy for CAB through the fractionation of its natural constituents, with a particular emphasis on the protein-rich fraction and its interactions with polysaccharides. This approach aims to uncover the techno-functional potential of these components while elucidating their structure–function relationships within complex natural extracts. The research was structured around four aims: (i) optimizing protein extraction, (ii) identifying and understanding a native protein–polysaccharide complex (PPC), (iii) establishing the impact of process on a novel native PPCs and (iiii) characterizing its structural, physicochemical, and techno-functional properties using a multi-analytical approach.
The first part of this study led to a major discovery: the identification, for the first time, of a native arabinogalactan–protein (AGP)-type complex in CAB. Converging evidence from monosaccharide profiling, FTIR spectra, ¹H NMR signals, as well as HPSEC coupled to RI and UV detection, collectively demonstrated the systematic co-extraction of proteins and polysaccharides and confirmed the existence of an intimately associated molecular complex. This fundamental finding redirected the research toward an in-depth structural and functional characterization of this natural PPC because of its scientific originality and potential industrial relevance.
The second part investigates process intensification using ultrasound. This green extraction technology significantly increased extraction yield while inducing controlled structural modifications within the PPC. Ultrasound treatment promoted disaggregation, exposure of functional groups, and molecular rearrangements, which together enhanced key functional properties, particularly long-term emulsion stability.The final part of the thesis examines the combined effect of temperature and ultrasound. A comparative analysis of PPCs extracted at 40 °C and 55 °C, with or without ultrasound, revealed a clear shift in dominant mechanisms. At 40 °C, ultrasound induced moderate physical rearrangements, leading to partial protein unfolding and increased exposure of reactive hydrophobic groups, resulting in a flexible and amphiphilic PPC with excellent emulsifying performance. At 55 °C, however, the combination of heat and ultrasound intensified hydrophobic and covalent interactions such as polyphenol oxidation and cross-linking producing a more rigid and reticulated network with thermo-resistant gel-like behavior. These contrasting structures highlight the ability to fine-tune PPC functionality through process conditions.
Overall, this thesis provides four major contributions: (i) the first identification of a natural, functionally active protein–polysaccharide complex from CAB; (ii) the demonstration that moderate ultrasound optimizes the balance between extraction yield, structural integrity, and interfacial performance; (iii) the mapping of synergistic or antagonistic thermo-sonication effects on PPC composition, structure, and functional properties; and (iv) the establishment of a “process–structure–function” conceptual framework to guide the integrated valorization of CAB into high-value multifunctional natural ingredients.
Beyond its original scientific contribution, these findings open promising perspectives for the development of sustainable bio-based ingredients and contribute to strengthening a circular bioeconomy within the cashew value chain in West Africa.
