Study Of Water-solubility And Stability Of β-carotene Improved By Soy Protein Isolate

β-carotene is a precursor of vitamin A, it can lower the risk of cancer and is able to act as an antioxidant. But, the application of β-carotene in food industry is limited by its sensitivity to light, heat, and air/oxygen and by extremely poor solubility in water. In this paper, with the soybean protein isolated(SPI) as the mainly encapsulation material of β-carotene, the spray drying technolody and molecular complex were used to prepare high stability β-carotene. To known well about the encapsulation properties of SPI and the bioavailability of β-carotene, The solubility, storage stability and morphology of microencapsulation and complex particles were evaluated, respectively. In addition, a more in-depth discussion on the formation mechanism of the SPI/β-carotene complex had been done. The main results are as follows:1. Spray drying microcapsule technology can significantly improve the storage stability of β-carotene:β-carotene in the microcapsules were very stable at low temperatures(e.g., 4 ℃), almost no degradation in 35 days; under high humid or temperature environment, the β-carotene encapsulated by SPI/MS 1:1 mixture, suffered more loss upon storage than the encapsulations with SPI or MS alone as wall material. The encapsulation efficiency(NE) of SPI/MS 1:1 mixture was 38.8%, larger than the NE of MS or SPI alone as the wall materials. The solubility of β-carotene spray-drying microcapsules were also obviously improved by SPI/MS 1:1 mixture.2. The complex of SPI/β-carotene, significantly improve the solubility and thermal stability of the β-carotene, but the storage stability of β-carotene in complex at room temperature weakened as the ratio of β-carotene/SPI increasing(1% ~ 6%). The loading efficiency of complex with 6% ratio of β-carotene/SPI was the highest, which was 62.5%. The formation of complex would quench the internal fluorescence intensity of SPI, which was the binding-related quenching. It was indicated that hydrophobic interaction was the dominant mechanism involved in their fomation and stabilization.3. Freeze drying accelerated the degradation of β-carotene in complex, but compared to β-carotene crystalline powder, the complex with low ratio of β-carotene/SPI(1%, 2%) obviously protected the binded β-carotene from degradation. Particles were of good solubility and dispersion. Fresh or Dried, the complex with the 2% ratio of β-carotene /SPI showed excellent thermal stability(80 ℃ and 60 ℃ respectively), and the β-carotene in dried powde can fully release from comples within 3 h in vitro digestion. Under the effction of pepsin and trypsin, SPI in the complex was hydrolysis incompletely, because the α and β subunits of 7S conglycinin were hardly sensitive to the enzymes. The possible cause was that some oxide generated when β-carotene binded to the SPI molecule, reducing the enzyme hydrolysis ability of some subunits in th protein.