Influence of High-Pressure Blanching on Polyphenoloxidase Activity of Peach Fruits and its Drying Behavior

Figures & data

Table 1 Thin-layer drying models

Equation	Name	References
MR = exp (−kt^n)	Page	Zhang and Litchfield[28]
MR = exp (−(kt)^n)	Modified Page	Overhults et al.[29]
MR = a exp (−kt)	Henderson and Pabis	Henderson and Pabis[30]
MR = a exp (−kt) + c	Logarithmic	Yaldiz et al.[31]
MR = a exp (−k0t) + b exp (−k1t)	Two-term	Sharaf-Eldeen et al.[32]
k, k0,k1 a, b, c, and n are model constants.

Table 2 Effect of pretreatments on polyphenoloxidase (PPO) activity

Pretreatments	Without carrier fluid	Dipped in citric acid (1.0%)		Dipped in citric acid (1.2%)		Dipped in citric acid (1.4%)
Non-pressurized samples
Control (10 min)	+
Hot water blanched ( 3 min)	−
Citric acid pretreatment (10 min)		+		−^1		−
Pressurized samples
Level of pressure	10 min	5 min	10 min	5 min	10 min	5 min	10 min
50 MPa	+	+	+	+	−^1	−^1	−^1
100 MPa	+	+	+	+	−^1	−^1	−^1
300 MPa	+	−^1	−^1	−	−	−	−
500 MPa	+	−	−	−	−	−	−
700 MPa	+	−	−	−	−	−	−
+, presence of polyphenol oxidase; −, absence of polyphenol oxidase; −^1, slow development.

Figure 1 Comparison of drying rate of peach fruits subjected to various combined pressure-pH pretreatments.

Figure 2 Moisture ratio of peach fruits subjected to various pressure-pH pretreatments.

Table 3 Values of statistical parameters of the logarithmic model

Pretreatment	Correlation coefficient, r^2	χ^2	RMSE	MBE
Control	0.99	0.0004	0.0169	5.2 × 10^−6
300 MPa	0.99	0.0017	0.0358	−9.7 × 10^−6
300 MPa with 1.2% citric acid	0.99	0.0011	0.0295	−6.2 × 10^−6
500 MPa	0.99	0.0007	0.0221	−1.8 × 10^−6
500 MPa with 1.0% citric acid	0.99	0.0011	0.0295	−9.9 × 10^−6

Table 4 Moisture diffusivity of peach slices

Pretreatment	Deff, m^2/s	r^2
Control	6.56 × 10^−10	0.90
300 MPa	7.35 × 10^−9	0.91
300 MPa with 1.2% citric acid	7.41 × 10^−9	0.91
500 MPa	7.61 × 10^−9	0.94
500 Mpa with 1.0% citric acid	7.65 × 10^−9	0.92

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