Inactivation of Listeria innocua and Escherichia coli in carrot juice by combining high pressure processing, nisin, and mild thermal treatments

The effect of high‐pressure processing or thermosonication in combination with nisin on microbial inactivation and quality of green juice

“…However, Pokhrel et al (2019) observed a decrease in pH and TSS of carrot juice after treated with the combination of high pressure,…”

“…This technology is effective on reducing microbial load; however, high pressure level with extended holding time is required to inactivate pressure‐resistant pathogens and spores (Bello, Martínez, Ceberio, Rodrigo, & López, 2014), which may adversely alter the product quality (Gudbjornsdottir, Jonsson, Hafsteinsson, & Heinz, 2010) and increase the cost of processing as well (Bermúdez‐Aguirre & Barbosa‐Cánovas, 2011). Combining moderately high pressure with nisin, which is a bacteriocin produced by a strain of Lactococcus lactis , resulted in an additional decrease of gram‐positive and gram‐negative bacteria (Lee & Kaletunç, 2010; Pokhrel et al, 2019; Ponce, Pla, Sendra, Guamis, & Mor‐Mur, 1998), because pressure level above 300 MPa can affect the secondary structure of proteins and peptides and consequently increase the antimicrobial activity of nisin (Yang & Powers, 2016). According to the Pokhrel et al (2019), HPP at 500 MPa for 2 min at 20°C with 50 mg/L of nisin increased log reduction of Escherichia coli and Listeria innocua in carrot juice from 5 to 8 CFU/ml and 4 to 7 CFU/ml, respectively, when compared to high‐pressure treatment alone and there was no significant change in the quality of the product.…”

“…Combining moderately high pressure with nisin, which is a bacteriocin produced by a strain of Lactococcus lactis , resulted in an additional decrease of gram‐positive and gram‐negative bacteria (Lee & Kaletunç, 2010; Pokhrel et al, 2019; Ponce, Pla, Sendra, Guamis, & Mor‐Mur, 1998), because pressure level above 300 MPa can affect the secondary structure of proteins and peptides and consequently increase the antimicrobial activity of nisin (Yang & Powers, 2016). According to the Pokhrel et al (2019), HPP at 500 MPa for 2 min at 20°C with 50 mg/L of nisin increased log reduction of Escherichia coli and Listeria innocua in carrot juice from 5 to 8 CFU/ml and 4 to 7 CFU/ml, respectively, when compared to high‐pressure treatment alone and there was no significant change in the quality of the product.…”

“…In addition, pH, viscosity, acoustic energy density, and treatment time are also other important factors of TS treatment that influence the lethality of bacteria (Guerrero, López‐Malo, & Alzamora, 2001). More than 5 log reduction of E. coli was attained in fresh carrot juice when treated with TS (22 mm probe, 24 kHz, 120 µm) for 2 min at 58°C and did not adversely affect the quality (Pokhrel et al, 2019). Similar results were obtained in the inactivation of S. cerevisiae in pineapple, grape, and cranberry juices (Bermúdez‐Aguirre & Barbosa‐Cánovas, 2012) and E. coli in strawberry juice (Yildiz, Pokhrel, Unluturk, & Barbosa‐Cánovas, 2019) under continuous TS treatments.…”

Augmenting the Pressure-Based Pasteurization of Listeria monocytogenes by Synergism with Nisin and Mild Heat

“…Previous studies have also indicated that pressure at an intensity level of 400 MPa lasting for up to 10 min in the presence of 1000 IU/mL nisin could also be efficacious for the treatment of sessile cells of the pathogen when tested against L. monocytogenes biofilm [39]. Nisin was also similarly efficacious against Listeria innocua at 35 and 50 • C and pressure intensity of 200-500 MPa [40]. In addition to antilisterial activities, this naturally occurring antimicrobial has been tested for enhancing the pressure-based pasteurization of bacterial spores [41], Escherichia coli and Staphylococcus aureus [42], Salmonella enterica serovar Typhimurium and Bacillus subtilis [43], and pathogenic Cronobacter spp.…”