Production of Gelatin-Pullulan- Nanofibers Cellulose Film Containing Salmonella Phages and Effect Its Anti-salmonella Against Salmonella typhimurium

Abstract

Introduction The main sources of Salmonella for humans are pork, beef, chicken, eggs, fruits, vegetables, and their derivatives such as mayonnaise, and peanut butter. Different species of Salmonella can adapt, grow or survive at different environmental conditions. Salmonella enterica is a majorcause of food borne illness in humans, and Salmonella typhimurium and Salmonella enteritidis serovars are the most prevalent. One strategy is to use active packaging to reduce the microbial load or prevent the growth of microorganisms on food. Recently, antimicrobial active packaging has received much attention due to maintaining food quality, safety, and increasing shelf life. Among the antimicrobials used in the food industry, bacteriophages have a very good efficiency to control pathogenic bacteria. Pullulan has a good ability to form a film, its film has good characteristics such as transparency, odorlessness, tastelessness, solubility in water, and low permeability to oxygen and fat, However, the major obstacle is related to its price. The combination of polysaccharides with proteins has been done in order to improve the performance and reduce the costs of films. Gelatin is a suitable option to combine with pullulan in terms of good mechanical properties, reduced permeability, and its good price. Different ratios of gelatin and pullulan were studied and suitable film selected, but it needed to modify, so nanofibers cellulose was added in order to improve the mechanical properties and water resistance. Adding cellulose nano fiber can be a good and appropriate option. The aim of this research was to evaluate theantibacterial effectiveness of gelatin-pullulan- nanofibers cellulose composite film containing bacteriophage against Salmonella typhimurium at two different temperatures. Materials and MethodsGelatin and pullulan powders were weighted separately and mixed together (20gelatin-80pullulan). Nanofiber cellulose was extracted from rice bran and was used at three different levels (1%, 3%, and 5%). Commercial bacteriophage solution was added to each of the films separately and the films were prepared by molding method. Thickness, moisture content, solubility, swelling, tensile strength, and elongation of gelatin-pullulan film containing nanofibers were studied. Zone inhibitory of films containing different percentage of cellulose nanofibers on the agar media against Salmonella typhimurium (104 CFU.ml-1) was evaluated. The, antibacterial effect of selected film on the poultry meat inoculated with S. typhimurium (104 CFU.g-1) and several phages on the surface meat at 4 and 12 was also investigated. Results and Discussion The results indicated that gelatin-pullulan films containing different percentages of cellulose were showed approximately 2 mm of zone inhibitory compare to films free of phages. Also, inhibitory among films at different percentage of nanofiber cellulose did not show significant change. Antibacterial effect on poultry meat was dependent on temperature, films loaded with bacteriophages at higher temperature (12 ) was more effective compare to lower temperature (4 ). The populations of S. typhimurium were decreased 1 log and 0.7 log than control samples at 4 after 7 and 9 days respectively, while at 12 , 1 log and around 2.55 log decrease was found after 1 and 9 days, respectively. In a study, beef inoculated with salmonella was treated by SALMONELEXTM bacteriophage and resulted in 1.29 log reduction of pathogenic bacteria compared to the control sample (Yeh et al., 2017). In another study, the antibacterial effect of double-layer poly lactic acid/xanthan film at 10 °C compared to 4 °C against pathogenic bacteria of Salmonella and Listeria was determined and found that at10 °C, the number of pathogenic bacteria was decreased more than at 4 °C (Radford et al., 2017).. Kamali et al. (2022b) reported that the release of phages from the film of 30 poly lactic acid/70 whey protein to the meat surface after one hour was 63.22 % and 63.18 % at 4 °C and 10 °C, respectively, which means no significant difference, after one day at both temperatures.

Keywords

• bio-control
• composite film
• food safety
• pathogen bacteria