Thermal Chlorophyll Degradation Kinetics of Mint Leaves Puree

Figures & data

Table 1 Come-up-time for desired temperature attainment in culture tubes

Processing temperature (°C)	Come-up time (min:sec)
80	8.04
85	7.15
90	7.12
95	6.52
100	6.46
105	8.48
115	7.20
125	7.06
135	7.00
145	5.02

Table 2 Computed values of coefficients of equation (2) for chlorophylls (a, b, and total) degradation

pH	Temp.(°C)	Chlorophyll-a			Chlorophyll-b			Total chlorophyll
		ka	R^2	S.E.	kb	R^2	S.E.	kt	R^2	S.E.
4.5	80	0.0116	0.977	0.2464	0.0105	0.979	0.1318	0.0111	0.941	0.2171
	85	0.0125	0.992	0.1544	0.0118	0.994	0.1460	0.0123	0.986	0.1203
	90	0.0176	0.981	0.1510	0.0172	0.997	0.0908	0.0174	0.996	0.0933
	95	0.0210	0.946	0.3083	0.0181	0.994	0.7370	0.0195	0.980	0.2146
	100	0.0267	0.989	0.1861	0.0222	0.989	0.2278	0.0228	0.958	0.2908
	MRQE		0.2690			0.2453			0.2489
5.5	105	0.0251	0.997	0.1289	0.0197	0.998	0.0729	0.0228	0.993	0.1130
	115	0.0298	0.995	0.1836	0.0240	0.999	0.0588	0.0237	0.990	0.1262
	125	0.0356	0.993	0.1616	0.0271	0.998	0.0921	0.0294	0.972	0.2205
	135	0.0423	0.992	0.1317	0.0534	0.997	0.0923	0.0449	0.991	0.0924
	145	0.0522	0.997	0.0954	0.0694	0.980	0.1879	0.0604	0.992	0.1153
	MRQE		0.1363			0.1178			0.1343
6.5	105	0.0340	0.970	0.2368	0.0476	0.973	0.2988	0.0384	0.965	0.2723
	115	0.0418	0.936	0.2095	0.0700	0.989	0.1695	0.0424	0.901	0.2619
	125	0.0441	0.931	0.2276	0.0874	0.979	0.1539	0.0453	0.940	0.2082
	135	0.0604	0.986	0.1591	0.0948	0.996	0.0661	0.0641	0.988	0.1509
	145	0.0673	0.998	0.0596	0.1665	0.968	0.1645	0.0791	0.983	0.1627
	MRQE		0.2032			0.2108			0.2315
7.5	105	0.0375	0.970	0.2597	0.0195	0.940	0.2663	0.0270	0.979	0.2211
	115	0.0394	0.979	0.2589	0.0305	0.998	0.0575	0.0371	0.986	0.1867
	125	0.0424	0.993	0.1468	0.0366	0.994	0.1195	0.0409	0.994	0.1247
	135	0.0440	0.958	0.1995	0.0414	0.858	0.3271	0.0437	0.923	0.2373
	145	0.0453	0.895	0.3067	0.0505	0.994	0.0445	0.0465	0.913	0.2508
	MRQE		0.2448			0.2231			0.2188
8.5	105	0.0277	0.970	0.1916	0.0264	0.946	0.2232	0.0274	0.969	0.1754
	115	0.0331	0.966	0.2428	0.0386	0.977	0.2429	0.0343	0.979	0.1876
	125	0.0383	0.987	0.1746	0.0460	0.971	0.2996	0.0402	0.986	0.1850
	135	0.0497	0.945	0.3594	0.0859	0.995	0.1000	0.0539	0.931	0.4009
	145	0.0573	0.988	0.1063	0.0948	0.971	0.1699	0.0654	0.979	0.1367
	MRQE		0.2690			0.2453			0.2444

Figure 1 Thermal degradation kinetics of total chlorophyll in mint puree at pH 4.5.

Figure 2 Thermal degradation kinetics of total chlorophyll in mint puree at pH 8.5.

Table 3 Activation energy and frequency factor values for thermally processed mint puree at pH 4.5–8.5 and 80°–145°C

Compound	pH	E (kJ/mol)	Intercept (ln ko )	R^2	S. E.
Ca	4.5	47.669	5733.54	0.971	0.0683
	5.5	27.683	3329.69	0.961	0.0780
	6.5	22.742	2735.37	0.960	0.0641
	7.5	06.447	0775.41	0.982	0.0215
	8.5	24.395	2934.16	0.989	0.0355
	MRQE			0.0458
Cb	4.5	41.049	4937.36	0.950	0.0789
	5.5	42.538	5116.49	0.920	0.1738
	6.5	36.753	4420.67	0.931	0.1389
	7.5	29.390	3535.05	0.951	0.0925
	8.5	44.063	5299.87	0.954	0.1344
	MRQE			0.1043
Ct	4.5	41.606	5004.29	0.966	0.0648
	5.5	33.785	4063.63	0.919	0.1398
	6.5	24.208	2911.71	0.914	0.1032
	7.5	16.569	1992.87	0.877	0.0863
	8.5	28.746	3457.52	0.991	0.0387
	MRQE			0.0749
Ca: chlorophyll-a; Cb: chlorophyll-b; and Ct: total chlorophyll.

Figure 3 The Arrhenius relationship between chlorophyll degradation rate constant and processing temperature of mint puree at a) pH 4.5; b) pH 5.6; c) pH 6.5; d) pH 7.5; and e) pH 8.5.

Table 4 Entropy, enthalpy, and free energy values of activation for chlorophylls in thermally processed mint puree

Compound	pH	ΔS^# (kJ/molK)	ΔH^# (kJ/mol)	R^2	S. E.
Ca	4.5	−0.1573	44.657	0.968	0.0682
	5.5	−0.2235	20.456	0.994	0.0214
	6.3	−0.2236	19.439	0.947	0.0639
	7.5	−0.2658	03.144	0.922	0.0127
	8.5	−0.2210	21.092	0.986	0.0352
Cb	4.5	−0.1733	39.165	0.947	0.0773
	5.5	−0.1746	40.037	0.908	0.1772
	6.3	−0.1834	33.506	0.924	0.1334
	7.5	−0.2102	25.923	0.932	0.0977
	8.5	−0.1693	40.773	0.952	0.1272
Ct	4.5	−0.1745	38.593	0.961	0.0649
	5.5	−0.1988	30.483	0.903	0.1390
	6.3	−0.2193	20.903	0.889	0.1026
	7.5	−0.2411	13.262	0.818	0.0869
	8.5	−0.2096	25.438	0.988	0.0383
Tβ = 383.99 K; ΔG°^# = 105.76 kJ/mol
Ca: chlorophyll-a; Cb: chlorophyll-b; and Ct: total chlorophyll.

Figure 4 Enthalpy-Entropy plot for chlorophylls a, b, and total for thermally-processed mint puree at pH 4.5 to 8.5.