Evaluation of Mass Exchange During Osmotic Dehydration of Plum Using Response Surface Methodology

Figures & data

Table 1 Central Composite Rotatable Design for the independent variables (actual and coded levels)

Run #	Independent variables
	Actual level			Coded level
	Temperature (°C)	Sucrose concentration	Time (min)	Temperature (°C)	Sucrose concentration	Time (min)
1	50	45	150	0	0	0
2	60	30	240	1	−1	1
3	50	45	150	0	0	0
4	50	70.2	150	0	1.682	0
5	50	19.8	150	0	−1.682	0
6	50	45	150	0	0	0
7	40	30	60	−1	−1	−1
8	50	45	150	0	0	0
9	50	45	301.4	0	0	1.682
10	60	60	240	1	1	1
11	50	45	150	0	0	0
12	40	60	240	−1	1	1
13	33.2	45	150	−1.682	0	0
14	66.9	45	150	1.682	0	0
15	60	30	60	1	−1	−1
16	60	60	60	1	1	−1
17	40	30	240	−1	−1	1
18	50	45	150	0	0	0
19	40	60	60	−1	1	−1
20	50	45	0	0	0	−1.682

Table 2 ANOVA table showing the variables as a linear, quadratic and interaction terms on each response variable and coefficients for the prediction models

Source	DF	WL (%)		WR (%)		SG (%)		Shrinkage (%)
		Coefficient	Sum of squares	Coefficient	Sum of squares	Coefficient	Sum of squares	Sum of squares	Coefficient
b0	9	+65.72***	2662.14	+61.53***	2627.01	+4.06***	6.76	+55.3***	1795.58
Linear
b1	1	+6.6***	595.66	+6.3***	541.55	+0.44***	2.63	+5.44***	403.43
b2	1	+2.5***	85.53	+2.62***	93.94	+0.09*	0.1	−7.55***	777.5
b3	1	+10.29***	1440.77	+10.17***	1407.5	+0.34***	1.53	+0.71	6.76
Quadratic
b11	1	−1.34**	25.94	−1.08**	16.83	−0.16**	0.39	−0.82*	9.59
b22	1	−3.2***	147.9	−3.56***	182.22	+0.24***	0.81	−4.35***	272.95
b33	1	−5.29***	397.02	−5.4***	414.31	−0.09*	0.11	+1.14*	18.51
Interaction
b12	1	+0.42	1.41	+0.38	1.13	−0.08	0.05	+0.88	6.13
b13	1	+0.44	1.55	+0.13	0.13	+0.28***	0.63	−4.13***	136.13
b23	1	+2.27**	41.31	+2.37***	45.13	−0.21**	0.36	−4.38***	153.13
Residual	10		14.69		11.19		0.19		19.37
Lack of fit	5		11.43		7.69		0.14		14.03
Pure error	5		3.25		3.5		0.05		5.33
Total	19		2676.82		2638.2		6.95		1714.95
R^2		0.994		0.995		0.972		0.989
Adj- R^2		0.989		0.991		0.947		0.979
CV		2.05		1.93		3.43		2.65
Subscripts: 1 = temperature; 2 = sucrose; 3 = time. *Significant at 0.05 level. **Significant at 0.01 ***Significant at 0.001 level.

Figure 1 Response surface for WL (a), WR (b), SG (c), and shrinkage (d) during osmotic dehydration of plum as function of sucrose concentration and temperature (at constant immersion time, 150).

Figure 2 Response surface for WL (a), WR (b), SG (c), and shrinkage (d) during osmotic dehydration of plum as function of immersion time and temperature (at constant sugar concentration, 45 g/100 g sample).

Figure 3 The optimum region by overlaying contour plots of the four responses evaluated (WL, WR, SG, and shrinkage) as function of sucrose concentration and temperature (at constant immersion time, 240 min).

Figure 4 The optimum region by overlaying contour plots of the four responses evaluated (WL, WR, SG, and shrinkage) as function of immersion time and temperature (at constant sugar concentration, 60 g/100 g sample).