Kinetic Considerations of Texture Softening in Heat Treated Root Vegetables

Figures & data

Figure 1 Steps in sample preparation of root vegetables.

Figure 2 Typical plot of compression-decompression test used to calculated texture parameters.

Figure 3 Typical force-deformation curves for beet and turnip before and after cooking at 100°C.

Figure 4 Measured textural parameters as a function of heating time at 80°C.

Figure 5 Softening curves for turnip at selected temperatures.

Figure 6 Typical plot for characterization of softening behaviour in root vegetables.

Figure 7 Typical heat penetration curve for the beet root during come-up time.

Table 1 Kinetic parameters for thermal softening of beet root

Property	Temperature (°C)	Mechanism 1			Mechanism 2
		K (min^−1)	D (min)	R^2	K (min^−1)	D (min)	R^2
A. Firmness	70	0.134	17.2	0.95	0.00126	1826	0.82
	80	0.157	14.6	0.95	0.00348	662	0.99
	90	0.355	6.48	0.91	0.00638	360	0.90
	95	0.621	3.71	0.76	0.00784	293	0.95
	100	1.42	1.61	0.75	0.0190	120	0.97
B. Stiffnes
	70	0.114	20.0	0.92	0.00168	1373	0.84
	80	0.150	15.3	0.99	0.00316	728	0.99
	90	0.374	6.15	0.92	0.00557	413	0.95
	95	0.615	3.74	0.75	0.00746	308	0.93
	100	1.77	1.29	0.75	0.0228	101	0.98
C. Springiness
	70	0.142	16.1	0.98	0.00255	902	0.75
	80	0.157	14.6	0.78	0.00459	501	0.86
	90	0.399	5.76	0.98	0.0154	149	0.82
	95	0.908	2.54	0.75	0.0167	137	0.96
	100	1.86	1.23	0.87	0.0343	67	0.91

Table 2 Kinetic parameters for thermal softening of turnip

Property	Temperature (°C)	Mechanism 1			Mechanism 2
		K (min^−1)	D (min)	R^2	K (min^−1)	D (min)	R^2
A. Firmness	70	0.17	13.28	0.83	0.00333	692	0.98
	80	0.29	7.94	0.75	0.00486	474	0.91
	90	1.23	1.87	0.76	0.01049	219	0.95
	95	3.10	0.74	0.83	0.2203	104	0.97
	100	11.70	0.20	0.93	0.0321	71	0.91
B. Stiffness
	70	0.169	13.6	0.81	0.00332	693	0.98
	80	0.288	7.99	0.77	0.00480	479	0.91
	90	1.25	1.84	0.75	0.01048	219	0.96
	95	2.25	1.02	0.92	0.0226	102	0.98
	100	10.87	0.212	0.80	0.0322	71	0.91
C. Springiness
	70	0.136	16.9	0.78	0.00395	582	0.84
	80	0.330	6.97	0.75	0.00841	273	0.90
	90	1.17	1.95	0.88	0.01407	163	0.75
	95	2.42	0.953	0.93	0.1719	133	0.94
	100	25.9	0.088	0.83	0.03065	75	0.99

Table 3 Calculated activation energies (Ea) and temperature dependence of softening rate (z value) for turnip and beet root

Property →	Firmness				Stiffness				Springiness
Product ↓	Ea (kJ/mole) (k100)	R^2	z (C°) (D100)	R2	Ea (kJ/mole) (k100)	R2	z (C°) (D100)	R2	Ea (kJ/mole) (k100)	R2	z (C°) (D100)	R2
Turnip Mech. 1	146 (1.6862)	0.92	17 (1.33)	0.93	141 (1.6916)	0.91	17 (1.32)	0.92	167 (1.6829)	0.87	22 (1.26)	0.98
Turnip Mech. 2	83 (0.0279)	0.95	29 (80)	0.96	83 (0.0281)	0.95	29 (79)	0.95	60 (0.0256)	0.97	36 (84)	0.98
Beet Mech. 1	81.7 (0.7088)	0.88	30 (3.16)	0.92	92 (0.8225)	0.89	30 (2.71)	0.93	92 (0.8279)	0.88	26 (2.70)	0.89
Beet Mech. 2	87 (0.0150)	0.96	28 (148)	0.96	82 (0.0146)	0.90	29.6 (152)	0.91	92 (0.0301)	0.97	27 (74)	0.97

Figure 8 Change in z vale before and after correction for thermal lag for turnip.

Table 4 The log mean thermal firmness values for root vegetables

Temperature (°C)	Turnip			Beet
	Firmness	Stiffness	Springiness	Firmness	Stiffness	Springiness
70	1.70	1.70	1.86	1.74	1.75	1.70
80	1.67	1.67	1.85	1.73	1.73	1.69
90	1.68	1.68	1.85	1.74	1.71	1.74
95	1.72	1.72	1.84	1.72	1.72	1.73
100	1.69	1.69	1.80	1.77	1.75	1.71