Protection of antioxidants in pitaya (<i>Hylocereus undatus</i>) peel: effects of blanching conditions on polyphenoloxidase, peroxidase and antioxidant activities

MAI, Thi Hai Anh; TRAN, Thi Thu Tra; LE, Van Viet Man

doi:10.1590/fst.112921

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Food Science and Technology

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Original Article • Food Sci. Technol 42 • 2022 • https://doi.org/10.1590/fst.112921 copy

Protection of antioxidants in pitaya (Hylocereus undatus) peel: effects of blanching conditions on polyphenoloxidase, peroxidase and antioxidant activities

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Abstract

Pitaya peel is a by-product of the fruit processing, rich in phytochemicals and has great potential for application in food industry. In this study, blanching was applied to the pitaya peel treatment for inactivation of the polyphenoloxidase (PPO) and peroxidase (POD) which caused the antioxidant loss in the material during the processing and preservation. The effects of blanching temperature and time on the PPO and POD activities as well as the stability of betacyanins and phenolics of pitaya peel were investigated. At the blanching temperature of 98 ± 2 ^oC, the inactivation rate constants and half-life values of PPO and POD were 6.6 × 10^-3.s^-1 and 105 s and 16.6 × 10^-3.s^-1 and 42 s, respectively. During the blanching, betacyanins and phenolics were partially destroyed, their degradation rate constants and half-life values were 9.3 × 10^-4.s^-1 and 744 s and 3 × 10^-4.s^-1 and 2310 s, respectively. During the storage of dried pitaya peel powder (PPP), the degradation rate constants of betacyanins and phenolics of the blanched PPP were 1.4 and 1.8 times, respectively lower than those of the unblanched PPP. In addition, reduction in DPPH radical scavenging and ferric reducing antioxidant power of the blanched PPP was significantly lower than that of the unblanched PPP.

Keywords:
antioxidant activity; betacyanins; redox enzyme; phenolics; pitaya peel

Blanching temperature (^oC)	Polyphenoloxidase			Peroxidase
Blanching temperature (^oC)	k (×10^-3 s^-1)	t_1/2 (s)	Activation energy (E_a) (kJ/mol)	k (×10^-3 s^-1)	t_1/2 (s)	Activation energy (E_a) (kJ/mol)
70	1.80 ± 0.06^d	378^a	43.63 ± 0.54	5.00 ± 0.06^d	138^a	39.75 ± 1.17
80	3.70 ± 0.06^c	186^b		8.40 ± 0.10^c	83^b
90	4.40 ± 0.17^b	158^c		10.80 ± 0.06^b	64^c
98	6.60 ± 0.10^a	105^d		16.60 ± 0.12^a	42^d

Blanching temperature (^oC)	Betacyanins			Phenolics
Blanching temperature (^oC)	k (×10^-4 s^-1)	t_1/2 (s)	Activation energy (E_a) (kJ/mol)	k (×10^-4 s^-1)	t_1/2 (s)	Activation energy (E_a) (kJ/mol)
70	2.00 ± 0.00^a	3466^a	54.72 ± 0.44	0.67 ± 0.06^a	10452^a	59.70 ± 0.33
80	3.00 ± 0.00^b	2310^b		0.95 ± 0.05^b	7188^b
90	5.50 ± 0.71^c	1271^c		2.00 ± 0.00^c	3466^c
98	9.33 ± 0.35^d	744^d		3.00 ±0.00^d	2310^d

	Degradation rate constants (k) and half-lives (t_1/2) of betacyanins		Degradation rate constants (k) and half-lives (t_1/2) of phenolics
	k (×10^-3 week^-1)	t_1/2 (weeks)	k (×10^-3 week^-1)	t_1/2 (weeks)
Unblanched sample	4.70 ± 0.28^a	148^a	27.40 ± 0.42^a	25^a
Blanched sample	3.30 ± 0.10^b	207^b	15.00 ± 0.20^b	46^b

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[1] *Corresponding author: lvvman@hcmut.edu.vn