Encapsulation of bioactive nutraceutical compounds in donkey and bovine milk β-casein-based carriers

The use of self-assembled -caseins from bovine origin as nanocarriers for the delivery of nutraceutical compounds or drugs has been widely investigated. Concerning β-caseins from other milk sources, the use of hypoallergenic donkey β-CN as a potential delivery vehicle for nutraceutical hydrophobic compounds is beginning to generate interest. Therefore, the purpose of this study was to characterize the self-assembly properties and structural changes of purified β-CN obtained from hypoallergenic donkey milk under different conditions of pH, temperature, and ionic strength, with the comparison of commercial bovine β-CN. Based on this knowledge, the interaction mechanisms between donkey β-CN with vitamin D2, and resveratrol, were studied, as well as the encapsulation efficiency of resveratrol within β-CN micelles. These data can provide a theoretical basis for promoting the enrichment and bioavailability of hydrophobic bioactive compounds in food products. This thesis work has been structured as follows: CHAPTER 1 delves into the structure and attributes of casein micelles while highlighting bovine β-CN's favored role as an encapsulation material due to its unique structure. Intriguingly, similarities in self-assembly patterns between donkey and bovine β-CN were detected, seen through comparable CMC and CMT behaviors. It is interesting to further explore donkey milk-derived β-CN with hypoallergenic properties as nanocarriers for bioactive substances. Therefore, CHAPTER 2 examined the self-assembly, secondary structure, and surface hydrophobicity of isolated donkey β- CN under varying pH, temperature, and buffer concentration conditions, then was compared with commercial bovine β-CN. The results offer valuable insights into the factors that influence molecular interactions driving donkey β-CN self-association, which could be applied to the development of nanocarriers for bioactive compound encapsulation in pharmaceutical and nutraceutical contexts. Based on this concept, CHAPTER 3 studied the interaction mechanisms between both donkey and bovine β-CN, and vitamin D2 (VD2) were explored using fluorescence and Dynamic Laser Light Scattering (DLS) techniques at elevated vitamin/protein ratios. Furthermore, the mechanism of interaction between both β-CNs and resveratrol, as well as the ability of these protein micelles to encapsulate resveratrol are studied in CHAPTER 4. Lastly, CHAPTER 5 imparts the general discussion to declare the main findings of this thesis, and their potential applications in donkey β-CN encapsulating or delivering bioactive substances with the purpose of enhancing their stability and bioactivity.