Use of ultrasound technology for the inactivati̇on of microorganism in chicken meat under cold conditions and its effect on quality characteristics of the product

This thesis evaluated the effectiveness of combining ultrasound technology with sodium hypochlorite in the chilling process of poultry meat to inactivate Salmonella Typhimurium and Escherichia coli microorganisms. Additionally, the impact of ultrasound technology on the physical and chemical properties of poultry meat was investigated. Pre-trial experiments were conducted to determine the optimal ultrasound processing conditions for chicken breast meat. These trials involved both continuous and pulse mode conditions with amplitudes of 40% and 80%, using 250, 300, and 400 ml of washing (cooling) water. Pulse-mode ultrasound application resulted in the deterioration of the textural structure of the chicken breast meat, leading to the selection of continuous mode ultrasound for further experiments. During pre-trials, the temperature rise of distilled water was measured using a thermometer after applying the ultrasound test parameters. Temperature-time curves were obtained and analyzed for linear correlation. A highly linear correlation (R² = 0.9394) was observed between the temperature-time parameters when ultrasound was applied continuously at 80% amplitude in 300 ml of pure water. Based on these pre-trial results, ultrasound was set at amplitudes of 40% and 80% for 0, 1, 2, 3, and 5 minutes, with a circulation temperature of 4°C, an initial washing water temperature (sodium hypochlorite) between 8 and 10°C, and a cooling tank volume of 300 ml. Temperature control was observed throughout the ultrasonic application, and the overall temperature increase of the wash (cooling) water was controlled. At the end of the 5-minute sonication time, maximum temperature values of 8.77 ± 0.37 °C and 20.57 ± 0.76 °C were measured for amplitudes of 40% and 80%, respectively. The increase in temperature is due to the collapse of cavitation bubbles occurring within the device and mechanical energy transmitted through the device. When ultrasound was applied to chicken breast meat at amplitudes of 40% and 80%, it was found that 38.14 and 96.45 W ultrasound power were required, respectively. In addition, the ultrasonic energy density was calculated at 40% and 80% amplitudes, resulting in a density requirement of 13.46 and 34.03 W/cm2, respectively. The application of ultrasound at 40% amplitude was not sufficient to achieve microbial inactivation of at least 1 log KOB/g due to insufficient power and density values. As a result, it was found that an increase in amplitude was associated with increased temperature values at different sodium hypochlorite concentrations (%0, %2, and %5 NaClO), accompanied by an increase in ultrasound power and intensity data. The study included ultrasound treatments at concentrations of 0%, 2%, and 5% sodium hypochlorite (NaClO) for amplitudes of 40% and 80% at different time periods (0, 1, 2, 3, and 5 min). The inactivation effect of this process was studied. The study not onlyexamined the applications of NaClO and ultrasonication individually but also investigated the synergistic impact of ultrasonication combined with NaClO chemicals. At 40% ultrasound amplitude with 0% NaClO, a low inactivation effect on S. Typhimurium and E. coli microorganisms was observed. After 5 minutes of application, ultrasound combined with 2% NaClO washing water reduced S. Typhimurium and E. coli counts by 0.97 and -0.06 log kob/g, respectively. Using 5% NaClO for 5 minutes, the counts decreased by 1.41 and 1.55 log kob/g, respectively. Overall, ultrasound at 40% amplitude with different NaClO concentrations and durations was insufficient to achieve a approximately 1 log kob/g microbial inactivation for both microorganisms (p > 0.05). Consequently, the research focused on an amplitude value of 80%. At 80% ultrasound amplitude, a gradual microbial reduction was observed over 2, 3, and 5 minutes with 0% NaClO washing water, but 1 log kob/g microbial inactivation was not achieved (p > 0.05). S. Typhimurium and E. coli counts were reduced by 0.17 and 0.54 log kob/g, respectively, after 5 minutes. The study concluded that ultrasound alone at 0% NaClO is insufficient for inactivating Salmonella Typhimurium and Escherichia coli. However, increasing the washing water usage time (1, 2, 3, and 5 minutes), particularly at 2% and 5% NaClO concentrations, significantly enhanced microbial inactivation (p < 0.05). For ultrasound applications with 2% NaClO, E. coli and S. Typhimurium counts decreased by 1.06 and 0.56 log after 2 minutes, and by 2.12 and 1.49 log after 5 minutes. Using 5% NaClO resulted in significant reductions of 1.21 and 1.01 log after 1 minute, and 2.29 and 1.55 log after 5 minutes for E. coli and S. Typhimurium, respectively. The combination of ultrasound and NaClO exhibited a synergistic effect on microorganism inactivation while minimal microbial inactivation with only NaClO at different concentrations and times was found. Ultrasound cavitation disrupts microbial cells, allowing more NaClO solution to enter and enhance the bactericidal effect. Poultry slaughterhouses must limit S. Typhimurium and E. coli counts in carcasses entering the chilling phase to no more than 1 log kob/g. The optimal conditions for ultrasound inactivation were identified as 80% amplitude ultrasound combined with 0% NaClO for 5 minutes, 2% NaClO for 3 minutes, and 5% NaClO for 1 minute. Under these conditions, significant microbial reductions were achieved. The inactivation values for Salmonella Typhimurium and Escherichia coli microorganisms are as follows: in the washing water containing 0% NaClO, a reduction of 0.17 and 0.54 log KOB/g in 5 minutes was achieved. However, at 2% NaClO concentration, an application for 3 minutes resulted in reductions of 1.32 and 1.26 log KOB/g, and at 5% NaClO concentration with an application for 1 minute resulted in reductions of 0.88 and 1.10 log KOB/g, respectively. S. Typhimurium was found to be more resistant against ultrasounds compared to E. coli. The study highlighted that combining ultrasound with sodium hypochlorite resulted in higher microbial reduction rates than either treatment alone. The effect of ultrasound on the physical and chemical properties of chicken breast meat was also evaluated. Changes in quality parameters after ultrasonic application were investigated through various analyses, such as color analysis, texture profile analysis (TPA), pH analysis, TBARS analysis, and water holding capacity analysis. The impactof ultrasonication on color values revealed a minimal increase in the b* value, indicating a shift towards a whitish-blue color. The chicken breast samples did not show a significant difference in the L* and a* values of the color (p > 0.05). In addition, the optimal parameters resulted in a significant difference in total color change (ΔE), with more color variation observed compared to the control chicken breast without ultrasound. The application of ultrasound under optimal parameters has been found to increase pH in the sample compared to the sample without ultrasound. Under optimal conditions, ultrasound applied to chicken breast samples slightly increased the moisture content values compared to the control (without ultrasound) sample. The application of ultrasonication did not significantly impact the textural (hardness, adhesiveness, elasticity, chewiness, and elasticity) properties of chicken breast meat compared to the control sample. When analyzing the TBARS data, there was no significant difference compared to the control chicken breast samples. In addition, when evaluating the effect of ultrasound on water holding capacity, it was found that for ultrasonic applications with optimum parameters, there is an increase in water holding capacity as the concentration increases, but this difference was not considered significant (p > 0.05). In conclusion, ultrasonic technology combined with sodium hypochlorite (NaClO) is an effective method for the inactivation of Salmonella Typhimurium and Escherichia coli bacteria species in the chilling process of poultry systems. It was also found that the application of ultrasound did not have any negative effects on the physical and chemical quality parameters of chicken breast meat, and that it had the potential for integration into poultry facilities. The application of ultrasonic technology in poultry facilities not only provides a promising solution for producers and consumers, but is also an important and effective means of contributing to food safety. In addition, this technology offers an environmentally friendly and sustainable alternative to thermal treatments. Keywords: Ultrasound Technology, Sodium Hypochlorite, Salmonella Typhimurium, Escherichia coli, Food Safety.