Copigmentation effects and thermal degradation kinetics of purple sweet potato anthocyanins with metal ions and sugars

Applied Biological Chemistry

Table 1 The spectroscopic parameters including hyperchromic effect (expressed as (A − A ₀)/A ₀) and bathochromic shift (Δλ _max) of PSPAs (0.1 g L⁻¹) on complex formation with metal ions in pH 4 buffer

Metal ions	Concentration (mol L⁻¹)	Hyperchromic effect (%)	Bathochromic shift (nm)	Metal ions	Concentration (mol L⁻¹)	Hyperchromic effect (%)	Bathochromic shift (nm)
K⁺	0.002	−1.21 ± 0.26^a	0	Ca²⁺	0.002	−1.61 ± 0.22	0
	0.01	−0.60 ± 0.49	0		0.01	0.60 ± 0.27	0
	0.0 5	0 ± 0.48	0		0.05	3.42 ± 0.25*	−1
	0.1	0 ± 0.63	0		0.1	9.45 ± 0.91***	−1
Mg²⁺	0.002	−2.41 ± 0.36	0	Zn²⁺	0.002	0.20 ± 0.11	0
	0.01	−1.81 ± 0.17	0		0.01	2.99 ± 0.32*	0
	0.05	4.43 ± 0.55**	−1		0.05	8.58 ± 0.97***	0
	0.1	8.65 ± 0.87***	−1		0.1	16.77 ± 1.03***	−1
Cu²⁺	0.001	−0.88 ± 0.49	0	Fe²⁺	0.001	0.26 ± 0.17	0
	0.005	0.88 ± 0.36	0		0.005	4.98 ± 0.78*	0
	0.025	7.65 ± 0.83***	1		0.025	9.17 ± 0.92***	0
	0.05	13.46 ± 0.94***	3		0.05	18.16 ± 1.07***	0
Al³⁺	0.001	2.99 ± 0.83*	2	Fe³⁺	0.0001	−4.59 ± 0.89**	1
	0.005	5.39 ± 0.97**	4		0.0005	−2.59 ± 0.53	1
	0.025	15.37 ± 1.28***	4		0.0025	8.78 ± 0.95***	−1
	0.05	25.95 ± 1.56***	4		0.005	25.15 ± 1.39***	−3

^aNegative values mean hypochromic effect or hypsochromic shift
*, **, *** Significance levels of p < 0.05, 0.01, 0.001, respectively, by comparing the absorbance (A) of copigmented PSPAs solution with the value (A ₀) of corresponding solution without adding metal ions by multiple comparison analysis