Investigation the effect of using ZnO and Ag Nanoparticles and Nisin on the Microbial Contamination of yogurt

Abstract

The purpose of the study was to assess how the microbiological load of yogurt kept for 20 days at 5 ± 2 °C was affected by silver AgNPs and zinc ZnNPs nanoparticles placed onto edible gelatin shells at concentrations of 20 and 30%, either by themselves or in conjunction with nisin at a concentration of 50%. The result of this study indicated that the total bacterial counts at the beginning of storage ranged between 12.00 and 16.33 Log/g for all treatments, compared to the treatments for control T1 and T2, which were 24.66 and 22.66 Log/g respectively. With continued storage and up to a storage period of 20 days, treatment T11 was the best in terms of total number, which recorded 15.33 Log\g compared to the increase achieved by the control treatments T1 and T2, which reached 34.33 and 26.00 Log\g, respectively. The results also showed that no growth of yeasts and molds was observed on the first day of storage for all treatments. With continued storage until the 20th day, the best treatment was     T11, in which no growth was observed at the end of the storage period. It was followed by treatment T7, which recorded 0.33 Log\g. compared to the control treatments T1 and T2 , which recorded 3.33 and 2.00 Log\g. respectively. As for the lipolytic bacteria, they also had no growth at First day. On the 10th day of storage, treatment T7 was the best and had the lowest growth in this type of bacteria, reaching 0. 33 Log\g. At the end of the storage period, at the 20th day, treatment T11 was the lowest in terms of lipolytic bacteria, reaching 1.66 Log\g compared to T1 and T2, the control treatments, which recorded 12.33 and 9.33 Log\g. The rest of the treatments ranged between these values. We also note from the results that Proteolytic bacteria had no growth at First day, but at time 10 days, treatments T7 and T11 were the best due to the continued absence of any growth of proteolytic bacteria, while the control treatments T1 and T2 recorded values ​​of 2.00 and 1.66 Log\g. At the end of the storage period at time 20 days, we also note that treatment T11 is the best, as it recorded a value of 1.00 Log\g. compared to the control treatments T1 and T2, whose values ​​were 4.66 and 2.66 Log\g. respectively, while the values ​​of the rest of the treatments ranged between those values