Effects of Microwave Radiation, Organic Acid and Salt Combination on Survival of Pseudomonas Aeruginosa Inoculated In Veal Meat Stored In Refrigerator

Different species of Pseudomonas bacteria are found in abundance in environment. Although they are weak pathogens, they have great importance in food hygiene and human health because they are psychrotrophic bacteria, can grow and proliferate at refrigerated temperatures, and can produce proteolytic and lipolytic enzymes. 

In this study, the simultaneous effect of different doses of microwave radiation and different concentrations of salt and lactic acid on Pseudomonas aeruginosa inoculated onto veal meat pieces. For this purpose, 108 samples were evaluated in 9 treatments on days 0, 3, 6, 9, 12, and 15 during chilled storage in -4⁰ C. The control group was treated with distilled water. The bacterial count was done in Pseudomonas Agar medium and that showed that different concentrations of acid, salt, and microwave exposure time and their interactions had a significant effect on the mean logarithm number of bacteria during the refrigerating period. 

In this study, the interaction between microwave radiation, organic acid and salt cause to more reduction in the count of bacteria than the control group. There was a significant difference between the number of bacteria under acid and salt treatments and the control group (p<0.001)In this study, by controlling the effect of salt concentration and microwave duration, using 2.5 and 5% lactic acid led to reduce the logarithm of the bacteria during the refrigeration  period in comparison with the acid-free samples (P<0.001) and as well as, 5% acid significantly decrease the logarithm of the number of bacteria during the refrigeration  period compared to the samples treated with 2.5% acid (P <0.001). Also, by controlling the impact of the concentration if the acid and microwave duration, using 4 and 6% salt significantly decrease the logarithm of the number of bacteria during the refrigeration period compared to non-salty samples (p <0.001). Samples containing of 6% and 4% salt did not indicate a significant difference in the logarithm of the number of bacteria during the refrigeration period (p = 0.89). Also, the microwave duration of 9 s (65 °C) significantly decreases the logarithm of the bacteria compared to 7 (55 °C), 5 (45 °C) and 3 s (30 °C) (P <0.001). Also, using lactic acid (5%) and salt (6%) the microwave duration was reduced from 9 s (65 °C) to 5 s (45 °C) in order to complete elimination of bacteria. The results were analyzed by mixed repeated measure ANOVA (SPSS version 21). 

In summary, the results of this study showed that the use of organic acid, salt, and microwave irradiation on pseudomonas aeruginosa, which was inoculated into meat parts during storage in the refrigerator, reduced the bacterial count during this period. In this study, the combination of microwave radiation, organic acid and salt concentration caused a greater reduction in bacteria count compared to the control group, and there was a significant difference between the bacterial count when each these three factors were used comparing with control group.