Abstract
With the wide application of high hydrostatic pressure (HHP) technology in the food industry, safety issues regarding food products, resulting in potential food safety hazards, have arisen. To address such problems, this study explored the synergetic bactericidal effects and mechanisms of protocatechuic acid (PCA) and HHP against Escherichia coli O157:H7. At greater than 200 MPa, PCA (1.25 mg/mL for 60 min) plus HHP treatments had significant synergetic bactericidal effects that positively correlated with pressure. After a combined treatment at 500 MPa for 5 min, an approximate 9.0 log CFU/mL colony decline occurred, whereas the individual HHP and PCA treatments caused 4.48 and 1.06 log CFU/mL colony decreases, respectively. Mechanistically, membrane integrity and morphology were damaged, and the permeability increased when E. coli O157: H7 was exposed to the synergetic stress of PCA plus HHP. Inside cells, the synergetic treatment additionally targeted the activities of enzymes such as superoxide dismutase, catalase and ATPase, which were inhibited significantly (p ≤ 0.05) when exposed to high pressure. Moreover, an analysis of circular dichroism spectra indicated that the synergetic treatment caused a change in DNA structure, which was expressed as the redshift of the characteristic absorption peak. Thus, the synergetic treatment of PCA plus HHP may be used as a decontamination method owing to the good bactericidal effects on multiple targets.
Highlights
Outbreaks caused by foodborne pathogens have received public and media attention because of their risks to consumers
The current study provides a way to offset high hydrostatic pressure (HHP)’s bactericidal effect-related deficiency, and explores protocatechuic acid (PCA)’s potential as a food additive
The minimum inhibitory concentration (MIC) of the PCA on E. coli O157:H7 was 2.5 mg/mL, which was same in Nuding et al [30]
Summary
Outbreaks caused by foodborne pathogens have received public and media attention because of their risks to consumers. Escherichia coli O157:H7 is a harmful and common foodborne pathogenic bacteria that causes life-threatening infectious diseases [1]. The Centers for Disease Control and Prevention estimate that O157:H7 results in over 265,000 medical cases annually in the USA, which have medical costs and economic consequences [2]. Escherichia coli O157:H7 adapts to environmental and processing stresses [3], which might present potential dangers to food safety. Traditional thermal treatments have decent bactericidal effects, temperature-sensitive nutrients in food, such as anthocyanins, are destroyed during these processes [4]. It is necessary to find a method that can both protect temperature-sensitive nutrients and ensure food safety
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