Inactivation kinetics of inoculated Escherichia coli and Listeria innocua in fresh‐cut Chinese cabbage using sweeping frequency ultrasound

Abstract

Sweeping frequency ultrasound washing is a recent technology of applying varying ultrasound frequencies in the decontamination of fresh produce. Ultrasound inactivation of Escherichia coli and Listeria innocua inoculated on fresh‐cut Chinese cabbage was investigated at sweeping frequencies of 28 ± 2 to 68 ± 2 kHz for washing time of 5–40 min. The survival ratio of E. coli and L. innocua decreased with the time of exposure to ultrasound washing and varying frequencies. E. coli were more sensitive to ultrasound washing than L. innocua, achieving >3.0 log reductions after 10 min of washing with 40 ± 2 kHz. A nonlinear Weibull model was used to describe the experimental data, and the fitness of the model was evaluated by the coefficient of determination (R2) and the root mean square error (RMSE). The model used provided a good fit with R2 ≥ .98 for both bacteria and RMSE values in the range of 0.03–0.21 and 0.02–0.32 for E. coli and L. innocua, respectively. Practical Application Ultrasound decontamination is an alternative nonthermal technology that has been applied in recent years to improve the microbial safety of fresh produce. The bacterial inactivation is predominantly attributed to cavitation, an occurrence that interrupts cellular arrangement and function. With the known significance of sanitization in the processing of vegetables, it is imperative to develop and appraise novel approaches that contribute to the microbial safety of these fresh produce. Largely, the results of our study could guide the design of new ultrasonic fresh produce wash systems in addition to current industrial practice related to frequency selection and use of ultrasound during fresh produce sanitation.

Nondestructive monitoring, kinetics and antimicrobial properties of ultrasound technology applied for surface decontamination of bacterial foodborne pathogen in pork

“…The Weibull model showed slightly improved results and is consistent with literature and has been commonly implemented in various microbial inactivation assessments of non-thermal technologies due to the simplicity and reliability [14] , [15] , [26] . In assessing the kinetic parameters of the Weibull model, when ρ < 1 shows cumulative damage caused by cavitation on the microbial cell, rendering the cells more susceptible to lethal treatment, while The higher the δ value (The first decimal bacterial colony reduction period needed), the slower the microorganism inactivation cycle [26] .…”

“…The kinetic mathematical models defining microbial pathogens inactivation used in this study are shown below. Weibull [14] and log-linear [15] models, as well as a description of the parameters, is described …”

Influence of high power ultrasound on natural microflora, pathogen and lactic acid bacteria in a raw meat emulsion

“…For example, in strawberries, Gani et al [40] achieved 2 log reductions, corresponding to 33% of native microflora with ultrasound treatments performed at 60 W and 33 kHz, for 60 min. Alenyorege, Ma & Ayim, [41] achieved reductions up to 3 log of Listeria inocua, with 40 kHz for 10 min in bath ultrasound, in cabbages. In soy sprouts, with the addition of sanitizing agents and ultrasound bath treatments for 10 min, Ngnitcho et al [42] found 4 log reductions of L. monocytogenes .…”

Effective pretreatment technologies for fresh foods aimed for use in central kitchen processing

“…10,11 Ultrasonic decontamination is suitable for a variety of fresh food materials. For example, it is noted to be effective in cleaning strawberry, 12 Chinese cabbage, 13 lettuce, 13 and carrot, 4 among other produce. In addition to being able to effectively remove impurities, microorganisms, and pesticide residues on the surface of fruit and vegetables, ultrasonic cleaning is also noted to be able to help inactivate deleterious enzymes, resulting in improved quality of the treated produce.…”

“…18,19 The efficiency of ultrasonic cleaning is related to its applied frequency, power, and time. Alenyorege et al, 13 for example, studied the effects of different frequency patterns (sweep frequency, fixed frequency, and combination of frequencies) on ultrasonic decontamination of Escherichia coli and on physicochemical quality changes of Chinese cabbage. Compared with ordinary water cleaning, ultrasonic cleaning at a fixed frequency of 40 kHz could more effectively reduce the number of E. coli by 3 log(CFU)/g, retain about 20% more phenolic compounds, and did not affect the appearance of the produce.…”