Enzyme Activity and Nutritional Quality of Peach (Prunus persica) Juice: Effect of High Hydrostatic Pressure

Figures & data

Table 1 Kinetic parameters of PPO and PME inactivation by HHP

Enzymes	Pressure (MPa)	k (min^−1) × 10^−3	D (min)	R^2
PPO	400	23.96	961.2	0.754
	500	72.94	315.7	0.984
	600	128.4	179.4	0.961
PME	400	0.1829	12,590	0.295
	500	22.02	1046	0.976
	600	54.40	423.4	0.973
k (min^−1) indicates the inactivation rate constant.
D (min) means time to inactivate 90% of the enzyme at a given pressure.
R^2 represents the degree of model fit.

Figure 1 Pressure inactivation of PPO and PME in peach juice at 25°C. (a) Residual activity of PPO, (b) residual activity of PME, (c) pressure inactivation kinetics of PPO, and (d) pressure inactivation kinetics of PME. (▪) 400 MPa, (•) 500 MPa, and (▲) 600 MPa. The solid straight lines represent the model (Eq. (3)) fitting.

Table 2 Change of color and L-ascorbic acid content in fresh peach juice and their thermal and HHP processed counterparts over storage at 4℃

Treatment	Storage					L-ascorbic acid
conditions	(days)	L*	a*	b*	ΔE	(mg/100 mL)
Fresh juice	−	48.45 ± 0.33^a	0.12 ± 0.80^abc	3.81 ± 0.21^d	0.00	38.20 ± 0.48^a
600 MPa, 10 min	0	48.85 ± 0.18^a	−0.27 ± 1.98^bc	3.73 ± 0.41^d	0.56	32.62 ± 0.67^b
	15	46.53 ± 0.51^b	0.37 ± 0.58^abc	4.00 ± 0.40^cd	1.95	30.23 ± 0.45^c
	30	44.83 ± 0.42^c	0.80 ± 0.48^abc	4.69 ± 0.27^bcd	3.71	28.88 ± 0.53^d
	60	42.80 ± 0.29^d	1.89 ± 0.36^ab	4.04 ± 0.26^cd	5.93	27.47 ± 0.86^e
	90	41.40 ± 0.92^de	2.36 ± 0.46^a	4.69 ± 0.41^bcd	7.45	26.34 ± 0.95^e
90℃, 1 min	0	48.14 ± 0.20^ab	−1.47 ± 1.04^c	4.94 ± 0.27^abc	1.98	26.23 ± 1.12^e
	15	44.99 ± 0.86^c	0.42 ± 0.75^abc	5.30 ± 0.29^ab	3.78	22.72 ± 0.93^f
	30	42.33 ± 1.12^de	0.83 ± 0.30^abc	5.05 ± 0.32^ab	6.28	19.53 ± 0.48^g
	60	40.52 ± 0.58^ef	1.10 ± 0.40^ab	5.52 ± 0.43^ab	8.17	16.45 ± 0.61^h
	90	38.81 ± 0.66^f	1.99 ± 0.40^ab	5.75 ± 0.43^a	10.01	15.01 ± 0.92^i
^x Means in the same column followed by different letters imply a significant difference (p < 0.05) according to Turkey Test.
All data were the means ± SD, n = 3.

Table 3 Rheological parameters of peach juice

Treatment conditions	K(mPa^.S^n)	n	R ^2
Fresh juice	6.93	0.99	0.83
600 MPa,10 min	7.44	0.98	0.94
90°C, 1min	8.53	0.96	0.96
K is the consistency index; n is the flow behaviour index; R ^2 is the regression coefficient by Power law model.

Figure 2 Effects of HHP and thermal treatment on viscosity (a) and sensory properties (b) of peach juice. (▲) 90°C, 1 min; (▪) 600 MPa, 25°C, 10 min; (◆) untreated. The solid lines represent the model (Eq. (2)) fitting.