Inactivation of polyphenol oxidase from watermelon juice by high pressure carbon dioxide treatment

Abstract

The inactivation of polyphenol oxidase from watermelon juice with high pressure carbon dioxide (HPCD) treatment was investigated. The maximum reduction of polyphenol oxidase (PPO) activity inactivated by HPCD treatment was 95.8% at 30 MPa and 50°C for 30 min, which was far higher than 50.9% of control treatment at 50°C for 30 min. The inactivation of PPO was adequately described by a two-fraction model, which indicated that a labile and stable fraction might present in PPO from watermelon juice. The kinetic rate constants k L and k S of labile and stable fractions were 1.976 and 0.041 min −1 by HPCD treatment of 30 MPa and 50°C. And the labile fraction was easier to be inactivated by kinetic analysis. HPCD treatment with the combined effects of pressure, temperature, pH reduction, and time was stronger to inactivate PPO from watermelon juice than control treatment at the same temperature.

Ohmic heating assisted polyphenol oxidase inactivation of watermelon juice: Effects of the treatment on pH, lycopene, total phenolic content, and color of the juice

“…The results have been shown in Table 1, the R 2 and v 2 values were found to be in the range of 0.93-0.97 and 0.002-0.01, respectively, which indicate a good fit. Liu et al (2013) reported the D 50 of 12.7 min whereas in present study the D 90 was found 1.92 and 0.63 min for PPO in water melon juice by HW and OH treatment respectively, Chutintrasri and Noomhorm (2005) studied the PPO in pine apple puree and found a D 90 of 11.4 min, such difference could be attributed due to the variation in the product and properties of the product. Hence the present study found that 90% of the PPO could be inactivated by OH treatment in a very short time as compared to the HW treatment.…”

Kinetics of the inactivation of polyphenol oxidase and formation of reducing sugars in sugarcane juice during Ohmic and conventional heating

“…On increasing the EFS, the effect of the EFS proceeded in opposing directions for both the fractions such that the labile fraction was easily disrupted while the stable fraction regained its stability; such observations are yet to be reported for OH treatment. However, Liu et al () reported an increase in the susceptibility of the stable fraction of PPO in water melon juice at high pressures. The possibility of the same phenomenon in sugarcane juice during OH processing was possible.…”

“…Limited reports are available on the inactivation kinetics of enzymes by OH. However, a few studies have reported first‐order inactivation kinetics of PPO in apples (Castro, Macedo, Teixeira, & Vicente, ) and a biphasic order of urease inactivation in soymilk (Liu, Hu, Zhao, & Zhang, ). As per the reported literature, PPO inactivation generally followed the first‐order kinetics during application of various technologies like pulsed electric field (medium: buffered solution) and supercritical carbon dioxide in apple juice (Gui et al, ; Zhong et al, ).…”

“…The two‐fraction kinetics was used only to explain the inactivation of pectinesterase in orange juice by thermal treatment (Chen & Wu, ) and for combined pressure and temperature treatments (Broeck, Ludikhuyze, Loey, & Hendrickx, ). The distinct isozyme model was used to describe the thermal inactivation of enzymes like peroxidase in broccoli and lipoxygenase in asparagus (Morales‐Blancas, Chandia, & Cisneros‐Zevallos, ), high pressure inactivation of PPO in watermelon (Liu et al, ) and Ohmic inactivation of urease in soymilk (Li, Chen, Ren, Wang, & Wu, ). Both these models differ from each other in a way that the two‐fraction model specifies the presence of two fractions of PPO where one fraction ( a ) is thermally resistant while the remaining (1 – a ) is thermally stable as opposed to the existence of isozyme forms in the distinct isozyme model.…”

“…such observations are yet to be reported for OH treatment. However, Liu et al (2013) reported an increase in the susceptibility of the stable fraction of PPO in water melon juice at high pressures. The possibility of the same phenomenon in sugarcane juice during OH processing was possible.…”