Carob seed protein hydrolysates combined with pectin protect microencapsulated linseed oil against oxidative degradation while maintaining in vitro lipolysis

This study evaluated the oxidative stability and in vitro digestibility of linseed oil microencapsulated as spray-dried emulsions. Emulsions were prepared using carob protein concentrate (CPC) or its enzymatic hydrolysate (CPH) as primary emulsifier, either as single-layer systems (SE) or multilayer systems with pectin (ME). After spray-drying of the emulsions, oxidative stability was monitored for 28 days at 37 °C by measuring oxygen consumption, conjugated dienes, thiobarbituric acid reactive substances, and protein modifications via tryptophan fluorescence quenching. Microparticles containing CPH oxidized less over the first 14 days of incubation compared to the samples based on CPC. After 28 days, CPHME microparticles exhibited the highest oxidative stability among the four systems, as evidenced by the lowest levels of primary and secondary lipid oxidation products in surface, total, and encapsulated oil, together with the lowest tryptophan fluorescence quenching. In vitro digestion of the reconstituted linseed oil emulsions revealed gastric and intestinal lipolysis degrees between 16 and 24% and 59–66%, respectively, for all four systems. Although multilayer emulsions slightly promoted gastric lipolysis, the intestinal lipolysis profiles remained relatively similar among the formulations. Overall, CPHME provided enhanced protection of the encapsulated oil against oxidation without substantially affecting lipid digestion. These findings highlight carob protein hydrolysates as a promising plant-based emulsifier for the development of functional foods rich in polyunsaturated fatty acids.