Abstract
A total of 150 samples of raw milk and two types of refrigerated processed dairy desserts dishes (cooked rice with milk and Mehalabia dishes) (50 for each) were collected from dairy shops and local restaurants in Assuit City, Egypt. ISO7932 method was used for enumeration of B. cereus, afterwards a PCR was performed to confirm the presence of cereulide toxin (ces) gene. In addition, the effect of different concentrations of chitosan and chitosan nanoparticles (CNPs) (0.05, 1%) on B. cereus was studied in pasteurized milk.The shelf life was evaluated by clot on boiling test and Ph value. Their pathological effect was detected by orally administration to experimental rats to investigate their adverse effect on rats liver and intestine using histopathological examination. The most prominent potent bactericidal effect was observed inCNPs 1%, B. cereus count reached to undetectable level at 5th day of refrigerated storage. The pasteurized milk inoculated with B. cereus, chitosan and CNPs showed some pathological lesions in rats treated with B. cereus,while the chitosan 0.5% had antibacterial activities without cytotoxic effect on rat tissues, alternatively to CNPs 1%, which exist edematous tips of intestinal villi and mild kupffer cells activation in liver.Therefore, our results contribute data that are primary to indicate the risk of food poisoning due to B. cereus and trials to control that in food by careful using of nanotechnology. However, the additional researches are needed to safe using of this technology even on natural nano-materials as it at nano-size gain new qualities.
Highlights
B. cereus is a spore forming opportunistic environmental wide spread pathogen, cause food-borne outbreaks in human (Yu et al, 2019). Zhao et al (2020) had isolated B. cereus from different dairy products, and considered it as a potential risk pathogen need to contribute an effective prevention and control program
Another purpose was to investigate the potential of applying chitosan and its nanoparticles as a natural food preservative to control the growth of B. cereus in pasteurized milk during storage
Our present study was focused on the application of chitosan and chitosan nanoparticles (CNPs) in pasteurized milk contaminated with B. cereus as an example of spoilage and pathogenic microorganism
Summary
B. cereus is a spore forming opportunistic environmental wide spread pathogen, cause food-borne outbreaks in human (Yu et al, 2019). Zhao et al (2020) had isolated B. cereus from different dairy products, and considered it as a potential risk pathogen need to contribute an effective prevention and control program. Because chitosan has many advantages properties and mostly safe, so it used in nanotechnology as chitosan nanoparticles (CNPs) depend on ionic gelation method, which describes the crosslinking reaction of chitosan with sodium tripolyphosphate (TPP) (Nguyen et al, 2017; Sreekumar et al, 2018) the objective of our study was to detect the incidence and count of B. cereus in raw milk and two dairy desserts detect the cerulide producing toxin (ces gene) in isolates by using PCR Another purpose was to investigate the potential of applying chitosan and its nanoparticles as a natural food preservative to control the growth of B. cereus in pasteurized milk during storage. To provide a histopathological evaluation for the antimicrobial activity of chitosan and CNPs in different concentrations against B. cereus on intestine and liver of experimental rats
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