Abstract
Coli ATCC 25922 inactivation was studied to determine the effect of high-pressure carbon dioxide (HPCD) process on pumpkin puree. Experiments were performed using a batch HPCD system at three conditions of pressure (7.5 MPa, 17.5 MPa and 27.5 MPa) at 32 °C. Afterwards, at the best experimental condition (27.5 MPa – 275 bar), a kinetic was performed to assess inactivation of microorganisms over time (from 1 to 8 h). The physicochemical characteristics (pH, total soluble solids – TSS, titratable acidity – TA, total carotenoids, total reducing sugars – TRS, moisture and optical microscopy) of the pumpkin puree were also evaluated. HPCD with acidification increases bacterial efficacy of treatments, as well as significant changes in physicochemical parameters. HPCD treatment reduced the microbial load moderately in all experiments, by a maximum of approximately 3.17 log cycles in 8 h of process at 27.5 MPa (275 bar). Optical microscopy showed no difference in cell wall, just in starch which was expected by cooking.
Highlights
Pumpkin puree is a raw material with pH in the range of risk for pathogenic microorganisms (> 4.5) (Satiro et al, 2020), as well as availability of nutrients, soluble carbohydrates, contrast with the practical prospects of pumpkin puree, for example, requiring additional care (Jay, 2005)
The pumpkin puree sterilized (S puree and sterilized puree (S puree) + high pressure carbon dioxide (HPCD)) has lower pH value comparing with non-sterilized samples (In natura, purees before (Puree) and HPCD puree), and showed no significant difference between them, similar behaviour to the unsterile pumpkin puree (Puree and HPCD puree)
Garcia-Gonzalez et al (2009) argue that the main factor determining bacterial susceptibility to HPCD treatment might be related to the acid resistance of the microorganisms, because a key factor in the inactivation mechanism seems to be the concentration of CO2 in the water-phase of the food
Summary
Pumpkin puree is a raw material with pH in the range of risk for pathogenic microorganisms (> 4.5) (Satiro et al, 2020), as well as availability of nutrients, soluble carbohydrates, contrast with the practical prospects of pumpkin puree, for example, requiring additional care (Jay, 2005). Non-thermal processing techniques, such as high pressure carbon dioxide (HPCD) with supercritical CO2 may be applied to control spoilage or pathogenic bacteria with minor loss of nutrients content. Spilimbergo et al (2003) reported that the biocidal effects of HPCD on pathogens bacteria in foods are due to: explosion of wall cell as a function of the internal pressure; modification of cell membrane and extraction of lipids from the cell wall; inactivation of enzymes essential for microbial metabolism; extraction of intracellular compounds According to Garcia-Gonzalez et al (2007), which gathered several works of literature to better understand the microbial inactivation mechanism by treatment with HPCD, some hypotheses have been listed: solubilisation of the pressurized CO2 in the external liquid phase; changes in cell membrane; decrease in extracellular pH; inactivation of key enzymes or inhibition in cellular metabolism as a function of decreasing of pH; inhibitory effect of CO2 and in metabolism; disorder of electrolytes intracellular balance; removing vital components of cell and cell membrane. Spilimbergo et al (2003) reported that the biocidal effects of HPCD on pathogens bacteria in foods are due to: explosion of wall cell as a function of the internal pressure; modification of cell membrane and extraction of lipids from the cell wall; inactivation of enzymes essential for microbial metabolism; extraction of intracellular compounds
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