Effect of High Hydrostatic Pressure and Pulsed Electric Fields Processes on Microbial Safety and Quality of Black/Red Raspberry Juice

Abstract

Black and red raspberries are fruits with a high phenolic and vitamin C content but are highly susceptible to deterioration. The effect of high hydrostatic pressure (HHP 400–600 MPa/CUT-10 min) and pulsed electric fields (PEF, frequency 100–500 Hz, pulse number 100, electric field strength from 11.3 to 23.3 kV/cm, and specific energy from 19.7 to 168.4 kJ/L) processes on black/red raspberry juice was studied. The effect on the inactivation of microorganisms and pectin methylesterase (PME) activity, physicochemical parameters (pH, acidity, total soluble solids (°Brix), and water activity (aw)), vitamin C and phenolic compounds content were also determined. Results reveal that all HHP-treatments produced the highest (p < 0.05) log-reduction of molds (log 1.85 to 3.72), and yeast (log 3.19), in comparison with PEF-treatments. Increments in pH, acidity, and TSS values attributed to compounds’ decompartmentalization were found. PME activity was partially inactivated by HHP-treatment at 600 MPa/10 min (22% of inactivation) and PEF-treatment at 200 Hz/168.4 kJ/L (19% of inactivation). Increment in vitamin C and TPC was also observed. The highest increment in TPC (79% of increment) and vitamin C (77% of increment) was observed with PEF at 200 Hz/168.4 kJ/L. The putative effect of HHP and PEF on microbial safety, enzyme inactivation, and phytochemical retention is also discussed in detail. In conclusion, HHP and PEF improve phytochemical compounds’ content, microbial safety, and quality of black/red raspberry juice.

Effect of the High Hydrostatic Pressure Process on the Microbial and Physicochemical Quality of Shalgam

“…In the study of Chang et al with grape juice, a 1.1 log cfu/mL reduction was detected in a 300 MPa 3 min application, and the total inactivation level was reached when the applied pressure was raised to 600 MPa (>2.0 log). In another previous study, when pressure levels of 400 MPa and above were applied to raspberry juice for 2, 5, and 10 min, total inactivation was obtained with a 3.19 log cfu/mL reduction . According to a study on shalgam, the number of total yeast and molds was seen to linearly increase with rising temperature, regardless of the application pressure .…”

“…In another previous study, when pressure levels of 400 MPa and above were applied to raspberry juice for 2, 5, and 10 min, total inactivation was obtained with a 3.19 log cfu/mL reduction. 36 According to a study on shalgam, the number of total yeast and molds was seen to linearly increase with rising temperature, regardless of the application pressure. 24 An increase in the number of total yeast and molds was found as the application time was extended from 3 to 9 min; however, beyond that range, from 9 to 15 min, the number of Y&M is anticipated to decrease with an increase in application time.…”

The Effects of Jet-Milling and Pulsed Electric Fields on the Preservation of Spinach Juice Lutein Contents during Storage

“…Furthermore, PEF treatment on raspberry juice decreases the mold and yeast activities depending on the frequency. Also, PEF could more effectively inactivate the yeast than the mold [ 46 ]. However, it is difficult to inactivate microbial structures with a complex matrix because proteins, fats, and other compounds diminish the lethal effect of PEF; thus, the effects of PEF could be changed by the complexity of the beverage.…”

Processing and preservation of apple juice by pulsed electric fields combined with cinnamon essential oils: Exploring the effect of synergism

“…Longer treatment times as a result of multiplying the pulse frequency, pulse width, number of chambers, and the residence time of the sample in each treatment chamber is effective and practical way to increase PEF efficacy without increasing the applied energy, and thus, product temperature (Mosqueda‐Melgar et al, 2007; Toepfl et al, 2014). Combination of PEF with thermal treatment (Li et al, 2021; Luo et al, 2019; Timmermans et al, 2019), antimicrobial agents (Andaluz‐Mejía et al, 2022; Fernández‐Molina et al, 2001), and with other nonthermal technologies (Buitimea‐Cantúa et al, 2022; Zhang et al, 2020) to increase level of microbial inactivation, and thus PEF efficacy is another approach.…”