Impact of critical high‐intensity pulsed electric field processing parameters on oxidative enzymes and color of broccoli juice

Abstract

This research evaluated the influence of high‐intensity pulsed electric field (HIPEF) processing parameters, electric field strength, treatment time, and polarity on color difference (∆E*), polyphenol oxidase (PPO), and lipoxygenase (LOX) activities in broccoli juice. An optimization of HIPEF processing was accomplished and compared with thermal treatment (90°C/60 s). The lowest RALOX (68.71%) and RAPPO (36.11%) were reached at the strongest HIPEF conditions (35 kV/cm for 2,000 µs in bipolar mode). Bipolar mode pulses showed lower RALOX and RAPPO than monopolar mode. However, polarity did not show a significant effect on ∆E*. LOX was always more resistant to HIPEF treatment than PPO. The optimization process (26.35 kV/cm for 1,235 μs in bipolar mode) showed around 60% of enzyme inactivation and ∆E* = 0.69. Thermally processed broccoli juice exhibited the greatest color difference (∆E* = 7.89). HIPEF processing could be an appropriate technology to preserve the color properties and reduce the enzyme activity of broccoli juice. Practical applications Vegetable juices, in particular broccoli juice is attracting the food industry attention because it contains high amounts of nutrients; however, this fact increase their susceptibility to endogenous enzymes. HIPEF is a nonthermal technology for liquid food preservation that inactivates microorganisms and enzymes without compromising the nutritional and sensorial features of foods. Consequently, this technology could be used in the food industry as an alternative for thermal treatment to inactivate deteriorative enzymes in vegetable juices, offering to consumers a high quality product.

Matrix- and Technology-Dependent Stability and Bioaccessibility of Strawberry Anthocyanins during Storage

“…A study further compared low and high-intensity PEF treatments (12 kV/cm, 80 and 130 kJ/kg) of apple juice, leading to the partial inactivation of POD and PPO for the low PEF treatment (comparable to the observations in our results) and a higher inactivation for the high-intensity PEF treatment, suggested to be related to the thermal impact occurring due to dissipating energy as a result of Joule heating during the PEF treatment [47,49]. Another study of enzyme activity in strawberry puree reported only 3% residual PPO activity after high-intensity PEF at 35 kV/cm, a frequency of 229 Hz, a pulse width of 3.2 and 4.2 µs, treatment time of 1500 µs and bipolar pulses [50], while the minimal residual activity in broccoli juice reached 36% after highintensity PEF (35 kV/cm, 986 kJ/m³, treatment time 2000 µs, bipolar pulse), while lower Compared to other studies, a decrease in the POD and PPO activity to 70% and 55% of the initial activity, respectively, was observed in kale puree after thermal treatment at 70 • C for 2 min [44], while a thermal treatment at 72 • C for 15 s of apple juice, 90 • C for 15 min of strawberry puree and 90 • C for 60 s of broccoli juice resulted in (almost) complete inactivation of POD and PPO [13,47,48]. A study further compared low and high-intensity PEF treatments (12 kV/cm, 80 and 130 kJ/kg) of apple juice, leading to the partial inactivation of POD and PPO for the low PEF treatment (comparable to the observations in our results) and a higher inactivation for the high-intensity PEF treatment, suggested to be related to the thermal impact occurring due to dissipating energy as a result of Joule heating during the PEF treatment [47,49].…”

“…Compared to other studies, a decrease in the POD and PPO activity to 70% and 55% of the initial activity, respectively, was observed in kale puree after thermal treatment at 70 °C for 2 min [ 44 ], while a thermal treatment at 72 °C for 15 s of apple juice, 90 °C for 15 min of strawberry puree and 90 °C for 60 s of broccoli juice resulted in (almost) complete inactivation of POD and PPO [ 13 , 47 , 48 ]. A study further compared low and high-intensity PEF treatments (12 kV/cm, 80 and 130 kJ/kg) of apple juice, leading to the partial inactivation of POD and PPO for the low PEF treatment (comparable to the observations in our results) and a higher inactivation for the high-intensity PEF treatment, suggested to be related to the thermal impact occurring due to dissipating energy as a result of Joule heating during the PEF treatment [ 47 , 49 ].…”

“…A study further compared low and high-intensity PEF treatments (12 kV/cm, 80 and 130 kJ/kg) of apple juice, leading to the partial inactivation of POD and PPO for the low PEF treatment (comparable to the observations in our results) and a higher inactivation for the high-intensity PEF treatment, suggested to be related to the thermal impact occurring due to dissipating energy as a result of Joule heating during the PEF treatment [ 47 , 49 ]. Another study of enzyme activity in strawberry puree reported only 3% residual PPO activity after high-intensity PEF at 35 kV/cm, a frequency of 229 Hz, a pulse width of 3.2 and 4.2 µs, treatment time of 1500 µs and bipolar pulses [ 50 ], while the minimal residual activity in broccoli juice reached 36% after high-intensity PEF (35 kV/cm, 986 kJ/m³, treatment time 2000 µs, bipolar pulse), while lower intensities of PEF (15 kV/cm, 1932 kJ/m³, treatment time 500 µs, monopolar) even triggered the PPO activity in broccoli juice [ 48 ].…”

The synergistic effects of aloe vera gel and modified atmosphere packaging on the quality of strawberry fruit

“…Coatings can provide moisture and gas permeability barriers and thus help with microbial growth control and protection of color and texture (Bourtoom, 2008; Hosseini et al., 2017; Mousavian et al., 2021). One example of a novel edible coating for storehouse fruit is aloe vera (AV; Sánchez‐Vega et al., 2020; Serrano et al., 2006). AV possesses antifungal protection against numerous pathogenic fungi such as Botrytis cinerea (De Rodrıguez et al., 2005).…”

Effect of pulsed electric field‐assisted extraction on recovery of sulforaphane from broccoli florets

“…This effect was speculatively attributed to the increased SFN content in the extract, but this was not confirmed experimentally. Other studies report about the effect of high intensity pulsed electric fields (HIPEF), using voltage of 15 kV/cm or higher, on broccoli juice (Sánchez‐Vega, Elez‐Martínez, & Martín‐Belloso, 2015; Sánchez‐Vega, Garde‐Cerdan, Rodriguez‐Roque, Elez‐Martinez, & Martin‐Belloso, 2020; Sánchez‐Vega, Rodríguez‐Roque, Elez‐Martínez, & Martín‐Belloso, 2020). The authors used the technology for broccoli juice preservation aiming at minimizing the loss of bioactive compounds other than SFN.…”