EFFECT OF ZINC OXIDE NANOPARTICLES ON LISTERIA MONOCYTOGENES IN READY TO EAT MEAT (Ebeed.A.Saleh1., ELsayed,E.Hafez2.,Safaa,H.Gorbal3 and Etman,M.M 4)
1 Department of Food Hygiene, Faculty of Veterinary Medicine, Damanhour University, Egypt.
2 Department of Plant Protection and Bio nuclear Diagnosis, City of Scientific Researches and Technological Applications, Alex, Egypt.
3 Damanhour Directorate of Veterinary Medicine ,General Veterinary Authority, Ministry of Agriculture, Egypt.
4 Meat inspector in Ghayathi slaughterhouse, Western Region Municipality ,
Abu-Dhabi, U.A.E .
The purpose of this study was investigation of the effect of zinc oxide nanoparticles (Zn O NPs) on Listeria monocytogenes in Ready-to-eat meat products, to introduce a new, cheap, safe and fast way of food preservation. This work was performed on 240 Random Samples of RTE meat products (Frankfurter, Salami, Basterma & Luncheon)
( 60 sample of each product ). there was a significant increase in Listeria monocytogenes CFU/g in the 1st control group of each product which was not treated by any concentration of Zn O NPs, while in the 2nd group of each product which was treated with 60 ppm of Zn O NPs, there was some inhibition of CFU/g , and in the 3rd group of each product which was treated with 90 ppm of Zn O NPs, there was a significant inhibition which is matching with the highest concentration of Zn O NPs used in this study .
Keywords : Listeria monocytogenes, zinc oxide nanoparticles, RTE meat.
Food borne diseases are a substantial public health concern worldwide. Both developed and developing world suffer from severe food borne illness consequences, but to a variable extent (King et al., 2000). the U.S Centers for disease control and Prevention (CDC) estimate food borne outbreaks cause 76 million illnesses and about 5000 deaths annually in the United States (Mead et al., 1999). Scharff (2010) provided recent estimates that the cost of food borne illness in the U.S Accounted for 152 billion Dollars each year.
Food borne infections can cause several illnesses in the general population including healthy adults. However, older adults (those who are over 60 years old) tend to have more severe complications to these infections. Also, elderly persons are more susceptible to food borne illness infections and deaths (Buzby, 2002). According to Smith (1998), older adults are more likely to experience severe illness and deaths from gastroenteritis than younger adults. Listeria monocytogenes causes listeriosis, a rare disease, but it is potentially serious (Allerberger&Wagner, 2010), the average case fatality rate of human listeriosis is from 20% to 30% (Swaminathan&Gerner-Smidt, 2007).
Listeria monocytogenes can be found everywhere in the environment, in soil, water, sewage, silage and fecal materials. Soil is commonly known as a harborage of the bacterium, particularly in silage (Bourry&Poutrel, 1996). Also, it has been reported that a wide variety of healthy animal species shed Listeria in their feces. The stressful factors that animals encounter during transportation to slaughter plants has been reported to increase the shedding of Listeria. In addition, symptomatic and a symptomatic humans do excrete the bacterium in their feces.
Among the various metal oxides studied for their antibacterial activity, zinc oxide nanoparticles have been found to be highly toxic as antibacterial. Moreover, their stability under harsh processing conditions and relatively low toxicity to human combined with the potent antimicrobial properties favors their application as antimicrobials .
According to another study by (Jin et al., 2009), ZnO quantum dots, and nanoparticles of purified powdered ZnO, were effective in reducing the cell populationof Listeria monocytogenes, Salmonella Enteritidis, and E. coli O157:H7. The antimicrobial efficacy was concentration dependent, as higher ZnO concentration resulted in a greater reduction of growth. To be specific, 3.2 mg ZnO/mL treatment caused a 5.3 log reduction of L. monocytogenes and a 6.0 log reduction of E. coli O157:H7 in growth media after 2d incubation. ZnO at 1.12 and 0.28 mg/mL concentrations were investigated against Salmonella for antibacterial effects and as a consequence, cell growth was reduced by 6.1 and 4.1 log CFU/mL, respectively. the results demonstrate the antibacterial activity of ZnO NPs over a spectrum of bacteriaThis was further supported by a study conducted by ( Jones et al.,2008), where ZnO NPs were tested for their inhibitory effect on various bacteria including Staphylocoocus aureus, Staph. epidermidis, Staph. pyogenes and Bacillus subtilis. The growth reduction was greater at higher ZnO concentrations and/or smaller particle size, suggesting that the antibacterial mechanism of ZnO nanoparticles against bacteria cells was through accumulation of ZnO NPs inside the bacterial cell membrane.
Moreover, lower concentrations were used in a study by (Liu et al., 2009) where ZnO NP suspensions were analyzed at concentrations of 3, 6, and 12 mM specifically against E. coli O157:H7. Results showed that tryptic soy agar (TSA) plates with 3 and 6 mM ZnO nanoparticles exhibited less bacterial growth over that of a control while at 12 mM, the growth of E. coli O157:H7 was completely inhibited. The researcher also suggested a mode of action of ZnO NPs, which was similar to that by Jones (2008) that ZnO NPs damaged the bacterial cell membrane and caused a lost of intracellular contents.
Materials and methods :
1. Collection of samples (ISO-17604:2003):
A total of 240 random samples of ready-to-eat meat products (Frankfurter, Salami, Basterma & Luncheon) (60 samples of each product) were collected from different supermarkets and shops In Al-Behira and Alexandria governorates. Each sample weighted 250 gm; the collected samples were transferred in an insulated ice box under complete hygienic conditions rapidly and directly as possible to the Accredited Food and Feed Safety Laboratory, Faculty of Veterinary Medicine, Damanhour University.
2. Apparatus and instruments: (ISO 7218:2007)
Microbiological laboratory equipment's according to (ISO 7218:2007).