Modeling inactivation of Listeria monocytogenes, Shigella sonnei, Byssochlamys fulva and Saccharomyces cerevisiae and ascorbic acid and β-carotene degradation kinetics in tangerine juice by pulsed-thermosonication

Thermodynamics, kinetics, and computational fluid dynamics modeling of Escherichia coli and Salmonella Typhi inactivation during the thermosonication process of celery juice

In this study, thermosonication (37 KHz, 300 W; 50, 60, and 70 °C) of celery juice was performed to inactivate Escherichia coli and Salmonella Typhi in 6 min. The inactivation of pathogens and the process were modeled using mathematical, thermodynamic, and computational fluid dynamics models. The findings indicated that the distribution of power dissipation density was not uniform across the entire domain, including the beaker area, with a maximum value of 27.8 × 103 W/m3. At lower temperatures, E. coli showed a 9.4 % higher resistance to sonication, while at higher temperatures, S. Typhi had a 5.4 % higher durability than E. coli. Increasing the temperature decreased the maximum inactivation rate of both S. Typhi and E. coli by 15.5 % and 20.5 % respectively, while increasing the thermal level by 20 °C reduced the log time to achieve the maximum inactivation rate by 20.3 % and 34.9 % for S. Typhi and E. coli respectively, highlighting the stronger effect of sonication at higher temperatures. According to the results, the positive magnitudes of ΔG were observed in both E. coli and S. Typhi, indicating a similar range of variations. Additionally, the magnitude of ΔG increased by approximately 5.2 to 5.5 % for both microorganisms which suggested the inactivation process was not spontaneous.

Lactic acid fermentation of guava juice: Evaluation of nutritional and bioactive properties, enzyme (α-amylase, α-glucosidase, and angiotensin-converting enzyme) inhibition abilities, and anti-inflammatory activities

In the present research, the impact of fermentation with two strains of Lactiplantibacillus plantarum subsp. plantarum (PTCC 1896 and PTCC 1745) on physicochemical properties, antioxidant bioactive compounds, and some health-promoting features of guava juice was investigated. Results showed a significant (p < .05) decrease in pH, total soluble solids, glucose and fructose residues, vitamin C, and total carotenoids after 32 h of fermentation. Total phenolic content, free radical scavenging abilities, and ferrous reducing power were markedly enhanced during the fermentation process. Moreover, fermented juice represented good enzyme inhibition abilities (α-amylase and α-glucosidase) and anti-inflammatory activities. The initial amount of angiotensin-converting enzyme inhibitory activity (26.5%) increased to 72.1% and 66.4% in L. plantarum subsp. plantarum 1896 and L. plantarum subsp. plantarum 1745 treatments, respectively. These findings reveal that guava juice fermentation with the studied Lactobacillus strains can be a promising strategy to augment the functional properties of the fruit-based beverage.

Ultrasound-Assisted Lactic Acid Fermentation of Bakraei (Citrus reticulata cv. Bakraei) Juice: Physicochemical and Bioactive Properties

In this study, ultrasonication (US) (50 W, 30 kHz, 1–6 min) was used to increase the efficiency of Limosilactobacillus reuteri PTCC 1655 fermentation process (37 °C; 30 h) of Bakraei juice. Total sugars, pH, Brix, organic acids, vitamin C, polyphenols, antioxidant activity, α-amylase inhibition and anti-inflammatory properties were measured during the fermentation period. The results showed that by increasing the ultrasound time up to 5 min, pH, vitamin C, citric acid, and polyphenolic compounds decreased, while lactic acid, antioxidant capacity, α-amylase inhibition and anti-inflammatory properties were increased. When the ultrasound time was increased up to 6 min, compared to the non-ultrasound-treated sample, the efficiency of the fermentation process decreased and promoted a decrease in the microbial population, lactic acid levels, antioxidant activity, α-amylase inhibition, and anti-inflammatory properties of the juices. The initial anti-inflammatory activity (11.3%) of juice reached values of 33.4% and 19.5%, after US treatments of 5 and 6 min, respectively, compared to the non-sonicated juice (21.7%), after 30 h of fermentation. As a result, the use of ultrasound in the controlled fermentation process can increase the efficiency of fermentation process.

Combined Effect of Ultrasound and Microwave Power in Tangerine Juice Processing: Bioactive Compounds, Amino Acids, Minerals, and Pathogens

The inhibition of Escherichia coli ATCC 25922 (E. coli), Staphylococcus aureus ATCC6538 (S. aureus), Salmonella Enteritidis ATCC 13076 (S. Enteritidis), and Listeria monocytogenes DSM12464 (L. monocytogenes) is one of the main aims of the food industry. This study was the first in which the use of ultrasound and microwave power were applied to optimize the values of the bioactive components, amino acids, and mineral compositions of tangerine juice and to inhibit Escherichia coli, Staphylococcus aureus, Salmonella Enteritidis, and Listeria monocytogenes. The response surface methodology (RSM) was used to describe the inactivation kinetics, and the effects of ultrasound treatment time (X1: 12–20 min), ultrasound amplitude (X2:60–100%), microwave treatment time (X3: 30–40 s), and microwave power (X4:200–700 W). The optimum parameters applied to a 5-log reduction in E. coli were determined as ultrasound (12 min, 60%) and microwave (34 s, 700 W). The optimum condition ultrasound–microwave treatment was highly effective in tangerine juice, achieving up to 5.27, 5.12, and 7.19 log reductions for S. aureus, S. Enteritidis, and L. monocytogenes, respectively. Ultrasound–microwave treatment increased the total phenolic compounds and total amino acids. While Cu, K, Mg, and Na contents were increased, Fe and Ca contents were lower in the UM-TJ (ultrasound–microwave-treated tangerine juice) sample. In this case, significant differences were detected in the color values of ultrasound–microwave-treated tangerine juice (UM-TJ) (p < 0.05). The results of this study showed that ultrasound–microwave treatment is a potential alternative processing and preservation technique for tangerine juice, resulting in no significant quality depreciation.

Inactivation kinetics of pathogenic bacteria in persimmon using the combination of thermosonication and formic acid

Four models (Baranyi, modified Gompertz, log-logistic and Weibull models) were applied to examine the performance of thermosonication (TS) and formic acid (FA), individually and in combination, at three temperatures (40, 50, and 60°C) for the inactivation of pathogens inoculated on persimmon. Results indicated that all nonlinear kinetic models provided a good fit to data; however, the Baranyi showed the best performance in fitting data. The combined treatment of FA and TS had a higher negative impact on the microbial population compared to each treatment alone. The highest lethal impact was observed at 60 °C and in TS-3%FA treatment, which reduced the initial population of Escherichia coli, Salmonella enterica subsp. enterica, and Listeria monocytogenes (8.1 log CFU/mL) to 2.2, 1.6, and 1.3 log CFU/mL, respectively. Hence, the obtained models can be used to predict the inactivation of pathogens in a food model subjected to the combined treatment of thermosonication and FA.

Ultrasound assisted modulation of yeast growth and inactivation kinetics

The yeast Saccharomyces cerevisiae is well known for its application in the food industry for the purpose of developing fermented food. The ultrasound (US) technology offer a wide range of applications for the food industry, including the enhancement of fermentation rates and inactivation of microbial cells. However, a better understanding and standardization of this technology is still required to ensure the scaling-up process. This study investigated the effect of the US technology on the growth of S. cerevisiae using frequencies of 20, 25, 45 and 130 kHz, treatment periods from 2 to 30 min. Furthermore, yeast kinetics subjected to US treatments were evaluated using modelling tools and scanning electron microscopy (SEM) analysis to explore the impact of sonication on yeast cells. Yeast growth was monitored after different US treatments plotting optical density (OD) at 660 nm for 24 h at 30 ⁰C. Growth curves were fitted using models of modified Gompertz and Scale-Free which showed good parameters of the fit. In particular, US frequencies of 45 and 130 kHz did not have a disruptive effect in lag phase and growth rate of the yeast populations, unlike the frequency of 20 kHz. Moreover, inactivation curves of yeast cells obtained after exposure to 20 and 25 kHz also observed the best fit using the Weibull model. US frequency of 20 kHz achieved significant reductions of 1.3 log cfu/mL in yeast concentration and also induced important cell damage on the external structures of S. cerevisiae. In conclusion, the present study demonstrated the significant effect of applying different US frequencies on the yeast growth for potential application in the food industry.

Sonication treatment of pomegranate juice containing Saccharomyces cerevisiae and Byssochlamys fulva: Thermodynamic and predictive modeling after treatment and during shelf life

The effect of ultrasound treatment (100 W, 30 kHz; 50 and 100% amplitudes) on inactivation of Saccharomyces cerevisiae and Byssochlamys fulva in pomegranate juice and shelf life of the juice during storage at different temperatures (5, 15 and 30 °C) for 30 days was modeled using predictive and thermodynamics models. The Baranyi and square root type models were implemented to determine the growth rate of microorganisms. It was predicted that the minimum growth temperature (T_min) of B. fulva increased by increasing sonication amplitude, however, the T_min of S. cerevisiae was not function of sonication amplitude. The predicted shelf life was shown to be in good agreement with the measured sensorial shelf life. Increasing the temperature from 5 to 35 °C, reduced the shelf life from 17.5 to 3.5 days for B. fulva and from 15 to 5 days for S. cerevisiae. Moreover, for B. fulva, the activation energy (E_a) decreased from 43.4 to 27.5 kJ/mol by increasing the amplitude, while no significant change was observed for S. cerevisiae. Besides, thermodynamics properties of the shelf life such as enthalpy (ΔH++), entropy (ΔS++) and Gibbs free energy (ΔG++)  were proven to be suitable measures to determine the microbial spoilage reaction.