| The anthocyanin pigments extracted from black rice, red raspberry and cabbage were chosen to study their characterization. The methods of p H-differential and LC-MS were used to determine the content and composition of the anthocyanin respectively. The qualitative and quantitative changes of the copigmentation between Tannin acid and the anthocyanins were investigated by UV-vis and CIELab color space assay. The mechanism of the interaction between bovine serum albumin(BSA) and anthocyanin was also studied in this dissertation through UV-vis, fluorescence,circular dichroism(CD) and FT-IR. The study was aim to provide more theoretical basis for the application of the natural pigments in the food processing and healthcare industries. The main findings and results were summarized as follows:1. The content and composition of the anthocyanins from the natural pigments.The concentrations of anthocyanins from the commercial products of black rice, red raspberry and cabbage were 23.9%, 26.3%, 12.3% respectively. The anthocyanin purity of red raspberry product was the highest, followed by black rice and then cabbage. LC- MS results showed the types of anthocyanins from red raspberry and black rice were relatively single, predominated by Cyanidin-3-glucoside, whereas the types of anthocyanins from cabbage is more complicated, mainly composed by acylated anthocyanins, suchas Cyanidin-3-(sinapoyl)-diglucoside-5-glucoside, Cyanidin-3-(feruloyl)-diglucoside-5-glucosideand Cyanidin-3-(p-coumaroyl)-diglucoside-5-glucoside.2.The copigmentation effects between natural pigments and tannin acid.The copigmentation of natural pigments with tannin acid was beneficial. The results showed that the maximum absorption wavelengths of red raspberry and black rice pigments had a red shift as the increase of molar ratio(copigment/pigment), whereas no deviation was found in cabbage pigments. Along with the increase of p H value from 2.0 to 6.0, the values of lightness, chroma and hue differences changed with the addition of Tannin acid,especially the lightness made the main contribution of copigmentation to the total color. At p H4.0, the cabbage and red raspberry exhibited the greatest magnitude of total color difference with Tannin acid, while at p H 3.0 and 5.0 for black rice.3.The interaction between bovine serum albumin with different natural pigments.The UV-vis data showed that the absorbance of the BSA at 220 nm was increased by the accessorial dose of the anthocyanins, and at the same time the shift of the maximum absorbance wavelength exhibited that the structure of BSA changed. The fluorescence quenching spectra of BSA- anthocyanin indicated the quenching process was a static quenching mechanism with lower concentration of anthocyanins. The KSV Values of the pigments extracted from black rice, red raspberry and cabbage were 1.574, 1.449, and 2.144 respectively. The binding constant(K) of the pigments extracted from black rice, red raspberry and cabbage were 1.432×105 L/mol, 1.156×105 L/mol, and 2.602×106 L/mol, and the binding sites(n) of these three pigments were all approximately equal to 1-2. The main interaction forces between anthocyanin pigments and BSA were electrostatic force, hydrophobic interaction, and electrostatic force for black rice, red raspberry, and cabbage respectively. The CD results showed the changes of secondary structure of BSA was mainly caused by the α-helix content for the black rice anthocyanins(decreased from 37.3% to 36.2%) and the red raspberry anthocyanins(decreased from 37.3% to 35.9%),whereas the cabbage was caused by the β-folding content(increased from 15.4% to 17.5%). The FT-IR results has the same tendency with the CD spectra. |
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