HYGIENIC STATUS AND PREVELANCE OF HEAVY METALS AND PESTICIDE RESIDUES IN FROZEN MEAT, CHICKEN AND THEIR PRODUCTS IN LUXOR CITY

Dept. of Food Hygiene,

Animal Health Research Institute, Dokki.

Hygienic status and prevelance of heavy metals and pesticide residues

in frozen meat, chicken and their products in Luxor City

(With 7 Tables)

By

M.M. Hassouba; M.F. Hashim

and Omaima M.E.L. Maghraby

(Received at 12/5/2007)

الحالة الصحية ومدى تواجد بقايا المعادن الثقيلة والمبيدات الحشرية

فى اللحوم المجمدة والفراخ المجمدة ومنتجاتها فى مدينة الاقصر

مصطفى محمد حسوبة ، محمد فاروق هاشم ، أميمة محمد الطاهر مغربى

تم تجميع عدد خمسة وسبعون عينة لحوم مجمدة ولحم مفروم بقرى مجمد وفراخ مجمدة  (25 عينة من کل نوع) من أسواق مدينة الاقصر خضعت للفحوص الکيميائية والبکتيريولوجية وکان ترکيز الاس الهيدروجينى ونسبة القواعد النيتروجينية الکلية المتصاعدة فى الحدود المسموح بها. وکان متوسط قيم المعادن الثقيلة (الکادميوم والرصاص والزئبق) 005, ، 012, ، 003, ، 022, ، 004, ، 035, ، 009, ، 006, ، 085, ميکروجرام / جرام على التوالى وهى فى الحدود المسموح بها، وکان متوسط ترکيز      دى دى تى ، ألدرين +داى ألدرين وليندان 2.1، 4. ، 1.3 ميکروجرام/کيلو جرام فى اللحوم البقرية و 3, ، 1.2 ، 1.6 ميکروجرام /کيلو جرام فى اللحم المفروم البقرى وغير ملحوظة فى الفراخ وکان متوسط العد البکتيرى الکلى للميکروبات الهوائية والميکروبات المعوية والميکروبات القولونية (العد الاحتمالى) فى اللحوم البقرية المجمدة ، واللحم المفروم البقرى ، الفراخ 2.8 × ⁶10 ، 1.6 × ⁶10 ، 2 × ⁶10 ; 2.1 × ⁴10 ، 2.7 × ⁴10 ،  2 × ⁴10 ; 1.5 × ³10 ، 3.1 × ³10 ، 1.2 × ³10 خلية بکتيرية/ جرام من العينة على التوالى. وکانت جميع العينات خالية من ميکروب السالمونيلا. وکان تواجد الميکروب المکور العنقودى الذهبى والايشيريشيا کولاى المرضية فى عينات اللحوم البقرية المجمدة ، اللحم المفروم البقرى والدواجن المجمدة 8 ، 21.3 ، 6.7 ، 4 ، 8 ، 4% على التوالى.

Summary

Seventy five frozen beef, minced beef and chicken samples (25each) were collected from markets located in Luxor City, and subjected to chemical and bacteriological examinations. The PH and TVB-N were within the permissible limits.The examined samples had a normal values of Cd, Pb and Hg (the mean values were 0.005, 0.012, 0.003; 0.022, 0.004, 0.035 and 0.009, 0.006, 0.085 µg / g respectively). The mean concentration of DDT, Aldrin+dieldrin and Lindane were 2.1, 0.4 and 1.3µg / kg in beef and 3.0, 1.2 and 1.6µg / kg in minced beef and were undetected in chicken. The mean values of Aerobic plate, Enterobacteriaceae and Total coliform (MPN) counts of  frozen beef, minced beef and chicken were 2.8x106, 1.6x106, 2x106; 2.1x104, 2.7x104, 2x104; 1.5x103, 3.1x103 and 1.2x103 CFU/g respectively. All the samples were free from salmonella. The incidence of staph. aureus and Enteropathogenic E.coli in frozen beef, minced beef and chicken samples were 8 , 21.3 , 6.7 ; 4 , 8 and 4% respectively.

Key words: Heavy metals, pesticide residues, frozen meat, chicken,

 meat products

Introduction

Traditional physical meat inspection in markets is based on visual inspection, which does not identify pathogenic microorganisms such as Salmonella, Enteropathogenic E.coli, or Staph.aureus (Edwards, et al. (1997). To improve the control of such pathogens via improvement in process hygiene must apply the  hazard analysis critical control point (HACCP) system which has been promoted and implicated in the European Union (EU), (Anonymous, 1999). This analysis allowed the identification in the process flow of the sensitive areas that might contribute to a hazard. During processing of meat may become contaminated with both spoilage and pathogenic microorganisms from fecal and stomach contents. Additional sources of microbial contamination are the processing tool, equipments, structural components of the facility, human contact and carcass to carcass contact (Institute of food technologists, 2002).

The toxic elements cadmium, lead and mercury are widely distributed in environment and generally regarded as accidental pollutants although they are frequently found in minute amounts in food (Lucis et al., 1972, Underwood, 1977). Cadmium is used extensively in the mining and electroplating industries and found in fertilizers and fungicides. All its chemical form are toxic (Fleischer et al., 1974). It inhibits sulphydryl enzyme systems necessary for cellular metabolism (Gunn and Gould, 1957).

Lead is used in many industrial processes, lead paint, lead gasoline. It is a common material for spraying fruit trees. Absorbed lead accumulates in tissue of animal. Lead inhibits the activity of enzymes dependent upon the presence of free sulphydryl groups for their activity and this inhibition is clearly demonstrated in disturbance which occur in the biosynthesis of heme (Klauder and petering, 1975, Willoughby et al., 1976).

Mercury was used as fungicides, mercurial fungicides used for seed dressing. Toxic compounds of mercury accumulate in animal tissues, the alkylmercuries are slowly metabolized and more evenly distributed in the body tissues (Underwood, 1977). Mercury caused redness of lips, throat and tongue, loss of teeth, swelling and redness of the skin with pink-red finger tips. it affects the nervous system causing irritability (Mert, 1987). Contamination of food of animal origin by organochlorine and organophosphorus compounds and their metabolites has been reported in various countries (Neumann, 1988 and Goldman   et al., 1990).The main side effect of environmental pollution by pesticides in food contamination leading to injury of non-target organisms concerns the health of the workers and consumers. The wide spread usage of pesticides in Egypt led to many problems and constituted hazard in animals. In recent years, pesticides in food arises as an important problem of serious public health hazards which may lead to acute or chronic hepatic toxicity for human being.

The trend in this study is to evaluate the hygienic status and detection of heavy metals and pesticide residues in frozen (beef, minced beef and chicken) in Luxor City markets.

MaterialS and methods

A - Sampling

Seventy five frozen beef, frozen minced beef and frozen chicken samples (25 each) were collected from markets located in Luxor City. The samples were transferred to the laboratory in an ice box without undue delay to be examined.

B- Chemical examination:

a-      Determination of pH value  according to ISO (1974)

b-     Determination of Total Volatile Basic Nitrogen (TVB-N) according to FAO (1992).

c-      Heavy metals analysis: Digestion of samples was according to Perez (1999),Determination of cadmium (Cd), lead (Pb) and mercury (Hg) were conducted by using atomic absorption spectrophotometer “AAS” (Perkin Elmer, 2380, USA) which was adjusted at 228.8, 217 and 253.7 nm for Cd, Pb and Hg respectively.

d-     Determination of Organochlorine (OC) and organophosphrous (OP) pesticides were conducted by using HPLC apparatus (ISCO model 2350) HPLC and 205 UV/vis detectors with Hypersil HPLC column 250 x 4.6 mmBDs 18 OC 5M.

Samples were extracted and the pesticides residues were determined according to A.O.A.C. (1980) and Pesticide Analytical Manual (PAM) (1994).  

C- Bacteriological counts:

The samples were subjected to bacteriological examination through determination of:

a-      Aerobic plate count by spreading technique according to European Union Communities Commission (2001).

b-     Enterobacteriaceae count according to European Union Communities Commission (2001).

c-Enumeration of coliform bacteria by Most Probable number (MPN) according to FAO (1992).

D- Detection of some food-borne pathogens:

a-      Isolation and identification of Staphylococcus aureus according to Bennett and Lancette (2001).

b-     Isolation and identification of Salmonellae according to Health Protection Agency (HPA) (2003 a).

c-      Isolation and identification of Enteropathogenic Escherichia coli according to Health Protection Agency (HPA) (2003 b).

Serological identification was done by using diagnostic sera,         (Biotec, 1999).

Results

Table 1:  Mean values of the pH and TVB-N of the examined samples           (n = 25 each)

Table 2: Concentration of heavy metals in the examined samples          (µg /g). (n=25 each)

Table 3: Chlorinated pesticide residues in the examined samples in (ppb)

               *   Not  detected.

Table 4: Organophosphorus pesticide residues in the examined samples (ppb)

                * Not detected

Table 5: Mean values of bacterial counts of the examined samples           (n = 25 each)

Table 6: Incidence of food-borne pathogens in the examined samples              (n = 25 each)

Table 7: Serotyping of Enteropathogenic E.coli isolated from the examined samples       

Discussion

Table (1) showed that the mean values of the pH and TVB-N (mg/100g) of the examined frozen beef, frozen minced beef and frozen chicken were 5.9 , 13 ; 6.1 , 16 and 5.8 , 20  respectively. The obtained data are within the permissible limits according to The Egyptian Standards (1991, 2005) {pH is 5.6 -6.2 and TVB-N is 20 mg/100g}.

Data presented in Table (2) showed that the examined samples had a normal values of Cd, Pb and Hg when compared by FAO/WHO (1972) dietary intake limits (Cd 20 – 100 µg / day, Pb 100µg / day and Hg 0.03 mg / day). Egyptian Organization for Standardization and Quality control E.O.S.Q.C (2360/1993) mentioned that the maximum provisional weekly intake from cadmium by human as 0.0067 – 0.0083 mg/kg of body weight and 2mg/kg of sample weight, and from lead by human as 0.05 mg / kg body weight.

Cadmium (Cd) concentration in beef, minced beef and chicken in  Table (2) ranged from 0.0 to 0.04, 0.0 to 0.35 and 0.0 to 0.02 µg / g with mean values of 0.005, 0.012 and 0.003 µg /g respectively. These results agreed with those reported by Folandyezand Lorenc-Biala (1991) and Salisbury et al. (1991) and lower than that reported by Kienholz et al. (1974), Doyle and Pfander (1975), Wright et al. (1976) and Daoud et al. (1998).

Lead (Pb) concentration ranged from 0.006 to 0.45, 0.001 to 0.007 and 0.2 to 0.05µg / g with means 0.022, 0.004 and 0.035 µg / g in beef, minced beef and chicken samples respectively. These results agreed with the results which reported by Spaulding (1975), Wright      et al. (1976) and Salisbury et al. (1991) and lower than Amodio-Coccheri and Fiore (1987), Folandyez and Lorenc-Biala (1991) and Schiilz-Schroeder (1991).

Shroeder and Hipton (1968) have reported the significant difference in the levels with age as Pb concentration increased with age in many tissue under USA environmental conditions as cited by Underwood (1977).

Mercury (Hg) conc. in beef, minced beef and chicken as recorded in Table (2) ranged from 0.005 to 0.099, 0.005 to 0.008 and 0.08 to     0.1 µg / g with mean values of 0.009, 0.006 and 0.085 respectively. The recorded results of Hg agreed with those reported by Sell et al. (1975), Spaulding (1975) and National Bureau of Standards (1976).

Cd, Pb and Hg concentrations in the examined samples were within the permissible limits.

In Table (3) the existence of the Organochlorine pestisides with varying concentrations, reflects the intake of pesticides by the animals and may be attributed to way of nutrition (graze in different pastures) and continuously exposure to the spraying with insecticides to control external parasites. The persistence of DDT in the environment means that much of the material used for control of insect borne diseases and elimination of agricultural pests still contaminates soil, water and air (Ralls and Cortes, 1972) though their wide spread use in this country was restricted in 1974. Food and Feeds still contain detectable levels of these contaminants. Results recorded in Table (3) show that the concentration of DDT, Aldrin, Dieldrin and Lindane in beef ranged from 0.7 to 3.5, 0.02 to 1.0 and 0.65 to 2.5 mg /kg respectively, while in minced beef were 0.9 to 4.5, 0.8 to 2.0 and 1.1 to 2.5 with mean values of 2.1, 0.4 and 1.3 mg / kg in beef and 3.0, 1.2 and 1.6mg / kg in minced beef. DDT, Aldrin, Dieldrine and Lindane were undetected in chicken, the concentration of DDT in samples analyzed were much lower than the maximum limits established by the World Health Organization (1989) (5ppm in meat) DDT is still ubiquitous in the environment due to its past wide use and its chemical and physical characteristics. DDT persists for more than 10 years in the soil and accumulates in the organisms through the food chain. After absorption, a part of the DDT is metabolized, the products in mammals being DDE, DDA and DDT (Bartik and Piskac, 1980). Low levels of DDT and its metabolites will be present in the environment for a long time (Ert and Sullivan, 1992). The concentration of Lindane was low in beef than minced beef while their mean values were higher than the maximum limits established by the (WHO, 1989) which is 1.1 ppm. The data agrees with that recorded by Zasadowski     et al. (1991). The mean concentration of Aldrin, Dieldrine in the examined samples was higher than the maximum limits established by (WHO, 1989) which is 1.01 ppm. Similar results were nearly obtained by El-Shafei (1988) and Folandyez and Kannan (1992).

Table (4) shows the concentration of Malathion and Dimethoat which ranged from 1.0 to 2.5, 0.02 to 1.0 µg / kg in beef, respectively, while in minced beef ranged from 1.5 to 2.8 and 0.26 to 1.2 µg / kg, respectively, with mean values of 1.4 and 0.35 µg / kg in beef while mean of malation and dimethoate in minced beef was 1.7 and 0.7 µg / kg respectively, this result lower than Frank et al. (1990). Consequently, organochlorin and organophosphrous pesticide residues in food of animal origin are substantially high in developing countries than in areas of intensive urban due to application of pest control programs with care under official supervision.

The results presented in Table (5) showed that the mean values of aerobic plate, enterobacteriaceae and coliform (MPN) counts of frozen beef, frozen minced beef and frozen chicken were2.8x106, 1.6x106, 2x106 ; 2.1x104, 2.7x104, 2x104 ; 1.5x103, 3.1x103 and 1.2x103 CFU/g respectively. Bosilevac et al. (2004) reported that the mean values of aerobic plate and enterobacteriaceae counts in beef were 9.5x105 and 6.1x104 respectively. Arther et al. (2004) reported that the mean values of aerobic plate and enterobacteriaceae counts in beef were 2.9x103 and 250 respectively. Gill et al. (2005) reported that the aerobic plate and coliform counts of chicken were 103 and 20 respectively. Pepperell, (2005) reported that the aerobic plate count of cattle was 0.8x104. Paulsen et al. (2006) reported aerobic plate count of beef minced meat ranged from 0.2x102 to 0.5x 107 CFU/g.

Table (6) showed that the incidence of staph. aureus, salmonella and Enteropathogenic E.coli of the examined frozen beef, frozen minced beef and frozen chicken samples were 8 , 21.3 , 6.7 ; 0, 0, 0, ;  4 , 8 and 4% respectively. Ploatjies et al. (2004) identified staph.aureus in 50% of the beef carcasses. The high levels of staph.aureus growth indicate poor hygiene of the meat handlers during the processing stage as well as lack of sterilization of utensils and working surfaces. Staph.aureus produce enterotoxins which lead to food poisoning. Yasmine et al. (2005) isolated 4 salmonella strains out of 120 beef samples at a percentage of 3.3%. Busani et al. (2005) isolated 49 salmonella strains out of 5037 beef samples at a percentage of 1%. Phillips et al. (2001) recovered 10.3% Enteropathogenic E.coli out of 1275 beef samples. Table(7) showed that the isolated Enteropathogenic E.coli serotypes were two strains each of O55, O128, O111, O114, O119 and O142. George (2004) reported that Enteropathogenic E.coli serotypes O55 and O111 were imbilicated as a causative agents for nursery school outbreaks in London and Aberdeen in the 1940,s. He also added that O111, O119, O128 and O142 serotypes were isolated from infected infants in North America and Europe during the 1950,s and up to the early 1970,s in the United Kingdom. These outbreaks had a high attack rate and characterized by high mortality rate, which could exceed 50% of the babies less than 6 months of age, especially those that were bottle-fed.

In conclusion, frozen beef, minced beef and chicken samples showed high bacterial loads beside a relatively high rate of the pathogens, this is due to miss-handling and processing as well as the negligence of hygienic aspects at the production level. There fore, one can safely recommend the following, aiming to have meat with good quality: good hygiene of the meat handlers during the processing stage as well as good of sterilization of utensils and working surface. Thermo-stable of refrigerators and deep freezer is important for retarding the growth of both pathogenic and spoilage bacteria. Each food item must be kept separate. The laboratories performing the analysis must be accredited according to the ISO standard. Food handlers need to be educated on the importance of proper, safe hygienic working practices.

References

Amodio-Cocchieri, R. and Fiore, P. (1987): Lead and Cadmium concentrations in live stock breed in Campaina, Italy. Bull. Environ. Contam. Toxicol., 39(3): 460 – 464. 

Anonymous (1999): The evaluation of microbiological criteria for food products of an animal origin for human consumption. Opinion of scientific Committee on Veterinary Measures Relating to Public Health. European Commission, Brussels.

AOAC (1980): Official Methods of the Association official analytical chemists, Washington D.C. chapter 29 (pesticides) Bed.

Arther, T.; Bosilevae, J. and Nou, X. (2004): Escherichia coli O157 prevalence and enumeration of aerobic bacteria, enterobacteriaceae and E. coli O157 at various steps in commercial beef processing plants. J. of Food Prot. 67(4)     658 – 665.

Bartik, M. and Piskac, A. (1980): Veterinary toxicology, 137. Elseveier scientific publishing company Amsterdam-Oxford-Newyork.

Bennett, R.W. and Lancette, G.A. (2001): Staphylococcus aureus, Chapter 12, rev. Jan. 2001. In FDA Bacteriological Analytical Manual 8^th ed., Rev. A. AOAC International, Gaithersburg. M.D.

Biotec (1999): Bacterial typing anti-sera. Biotec. Laboratories Ltd. Ipswich. Suffolk U.K.

Bosilevac, J.; Arther, T. and Wheeler, T. (2004): Prevalence of Escherichia coli O157:H7 and levels of aerobic bacteria and enterobacteriaceae are reduced when hides are washed and treated with cetylpyridinium chloride at a commercial beef processing

Busani, L.; Cigliano, A. and Taioli, E. (2005): Prevalence of salmonella enterica and listeria monocytogenes contamination in food of animal origin in Italy. J. Food Prot. 68 (8) 1729 – 1733.

Daoud, J.R.; Adel, A.K. and Abou-Bakr, R.M. (1998): Determination of lead, cadmium and copper residues in muscles, liver and kidneys of slaughtered cattle and sheep in El-Sharkia Governorate. Vet. Med. J., Giza Vol. 46, No. 4. App. 339–348.

Doyle, J.J. and Pfander, W.H. (1975): Interactions of Cadmium with Copper, Iron, Zinc and Manganese in ovine tissues. J. Nutr. 105: 59.

Edwards, D.S.; Johston, A.M. and Mead, G.C. (1997): Meat inspection in the UK: an overview of present practices and future trends. Vet. J. 154:135 – 147.

Egyptian Organization for standardization and Quality Control (E.O.S.Q.C.) (1993): Maximum residue limits for heavy metals in food. Ministry of Industry. No.2360/1993, pp.5 Cairo. Egypt.

Egyptian Standards (1991): Frozen meats. Number 1522. Egyptian Organization for Standardization and Quality Control.

Egyptian Standards (2005): Frozen poultry and rabbits. Number 1090.  Egyptian Organization for Standardization and Quality Control.

El-Shafei, M.E. (1988): Monitoring of pesticide residues in Egyptian livestock in middle Egypt .Ph.D of thesis Meat Hygiene Fac. Vet. Med. Cairo University.

Ert, M.V. and Sullivan, J.B. (1992): Organochlorine pesticides in Hazardous materials Toxicology clinical principle of Environmental health. Sullivan and Krieger, Chapter 1020; 1027: Williams & Wilkins.

European Union Communities Commission (2001): Commission decision of 8 June 2001 laying down rules for the regular checks on the general hygiene carried out by the operators in establishments according to directive 64/433/EEC on health conditions for the production and marketing of fresh meat. Document 2001/471/EEC. Off. J. Eur Communities 21-6- 2001. L165: 48 – 53.

FAO (1992): Manual of Food Quality Control. Part 4. Food and Agriculture Organization of United Nation, Rome.

FAO/WHO, (1972): Evaluation of Mercury, Lead, Cadmium and the Food additives amaranth, diethylpyrocarbonate, and actyl gallate, WHO Food Additives series No. 4, pp. 11–56, World Health Organization, Geneva.

Fleischer, M.; Sarofim, A.F.; Fassett, D.W.; Hammond, P.; Shacklette, H.T.; Nisbet, J.C. and Epstein, S. (1974): Environmental impact of Cadmium. A Review by the panel on hazardous trace substances. In R. Goyer and H Falk, Ed. Environ. Health Perspect. Exp. Issue No. 7 P. 253. Health, Education and Welfare. Nat. inst. Environ. Health Sci.

Folandyez, J. and Kannan, K. (1992): Organochlorine pesticide and polychlorinated biphenul residues in slaughtered and game animal fats from northern part of Poland Zeitschrift Fuerleben smitleunter suchnug and Forschung. 195: 17.

Folandyez, J. and Lorenc-Biala, H. (1991): Metal in muscle tissue, liver and kidney of slaughtered animal from the Northern region of Poland . Bromatol. Chem. Toskyol, 22:19.

Frank, R.; Braun, H.; Stonefield, K.J. and Luyken, H. (1990): Organochlorine and organophosphrous residues in the fat of domestic farm animal species. Ontario-Canada 1096 – 1988 Food additives and contaminates, 7; 629.

George, C. (2004): The incidence, growth and survival of diarrhoeagenic Escherichia coli in South Africa meat products. Submitted in fulfillment of the requirements for the degree of master O/Science (Food Microbiology). In the Department of Microbial, Biochemical and Food Biotechnology. Faculty of Natural and Agricultural Science. University of the Free State. South Africa.

Gill, C.O.; Badoni, M.; Moza, L.F.; Barbut, S. and Griffiths, M.W. (2005): Microbiological Sampling of poultry carcass portions by excision, rinsing, or swabbing. J. Food Prot. 68(12)       2718 – 2720.

Goldman, L.R.; Smith, D.F.; Neutra, R.R.; Sounders, L. and Kiger, K.W. (1990): Pesticide food poisoning from contaminated water meloni . In California, 11985, Arch. Environ. Health 45, 229.

Gunn, S.A. and Gould (1957): Selective accumulation of Cd 115 by cortex of rat kidney. Proc. Soc. Exp. Biol. Med. 96:820.

Health Protection Agency (2003a): Standard methods for food products. Detection of salmonella spp. Standard method F13.Available at Http: www.hpa. org. UK/srm/div-esl-su/sops-docs/fsops/F/3i/. 3. pdf. Accessed 26 January 2004.

Health Protection Agency (2003b): Standard methods for food products. Direct enumeration of Escherichia coli Standard method F20. Available at Http: www.hpa. org. UK/srm/div-esl-su/sops-docs/fsops/F/20i/.3. pdf. Accessed 26 January 2004.

Institute of Food Technologist (2002): Expert report on emerging microbiological food safety issues, implications for control in the 21^st century.

ISO (1974): International Standard 2917 – 1974. meat and meat products: Measurement of PH (reference method). International Standard Organization.

Kienholz, E.W.; Chappell, W.R.; Megen, R.R. and Rudolph, H. (1974): Effects of dietary supplements of copper sulfate and molybdate upon liver and kidney concentrations of ten minerals in young chickens. Trace subs. In Environ. Health 8: 373. 

Klauder, D.S. and Petering H.G. (1975): Protective value of dietary Copper and Iron against some toxic effects of lead in rats. Environ. Health prespect. 12: 77. 

Lucis, O.J.; Lucis, R. and Shaikh, Z. (1972): Cadmium and zinc in pregnancy and lactation. Arch. Envir. Health. 25: 14.

Mert, W. (1987): Trace element in Human and Animal Nutrition. 5^th Edn. Vols. I and II. London: Academic press.

National Bureau of Standards, Washington D.C. (1976). 

Neumann, G.B. (1988): The occurrence and variation of organochlorine pesticide residues detected in Australian livestock at slaughter. Acta, Veternaria Scandinavca 84: 299. 

Paulsen, P. ; Schopf, E. and Smulders, F. (2006): Enumeration of total aerobic bacteria and Escherichia coli in minced meat and on carcass surface samples with an automated Most Probable-Number method compared with colony count protocols. J. Food Prot. 69(10) 2500 – 2503.

Pepperell, R.; Carol, A.R.; Silvia, N.S. and et al., (2005): Experimental  comparison of excision and swabbing microbiological sampling methods for carcasses. J. Food Prot. 68(10)          2163 – 2168.

Perez, D. (1999): Mercury levels in Mole Carbs Hipia cubensis, Emerita brasiliensis, E.portoricensis, and lepidopa richmondi (crustacean; Decapoda Hippidae) from a sandy beach at venzuela . Bull. Environ. Contam. Toxicol. 63: 320 – 326.

Pesticide Analysis Manual (PAM): Vol.1; 3^rd edition, (1994): US. Deponent of Health and human services. Food and Drug Administration.

Phillips, D.; Summer, J. and Alexander, F. (2001): Microbiological Quality of Austerian beef. J.Food Prot. 64(5) 692 – 696. plant. J. of Food Prot. 67(4) 646 – 650.

Ploatjies, Z.; Lues, J. and Buys, E. (2004): Staphylococcal growth in fresh vacuum-packed red meat at various storage conditions. 8^th World Congress on Environmental Health. Durban, South Africa.

Ralls, J.W. and Cortes, A. (1972): Survey of food ingredient DDT reactions under thermal processing conditions. J.Food Sci.    37: 760.

Salisbury, C.D.C.; Chan, W. and Saschenbrecker, P.W. (1991): Multi element concentrations in liver and kidney tissues from five species of Canadian slaughtered animals. J. Assoc. Off. Anal. Chem. 74: 587 – 591.

Schiilz-Schroeder, G. (1991): Lead and Cadmium in samples of muscle, liver and kidney from lambs and sheep. Fleisch Wirtschaft, 71(12): 1435 – 1438.

Sell, J.L.; Dietz, F.O. and Buschellan, M.L. (1975): Concentration of mercury in animal products and soils of North Dakota. In Archives Environmental Contamination and Toxicology. Vol. 3, p. 278. Springer-verlag, New York.

Shroeder, H.A. and Hipton, J.H. (1968): Arch. Environm. Health,       17, 965.

Spaulding, J.E. (1975): Unpublished data. USDA-APHIS, Washington, DC.

Underwood, E.J. (1977): Trace elements in human and animal nutrition 4^th Ed. Academic Press, New York .   

WHO (1989): Pesticide residues in food, FAO Plant protection paper 157 – 159.

Willoughby, R.A.; Thawley, D.G. and Brown, G. (1976): Interactions of Lead with other trace substances and dietary factors. Arch. Indust. Hyg. Toxic.(Yugoslavia) 26: 29.

Wright, F.C.R.; Younger, L.; Riner, G.C.; McPeth, C.A. and Haugler, M. (1976): Residue of Lead and associated clinical observations in cattle given daily oral subtoxic doses of a wet Lead based paint. Bull. Envir. Contam. And Toxicol. 16: 156.

Yasmine, G.; China, B. and Korsak, N. (2005): Belgian surveillance plans to assess changes in salmonella prevalence in meat at different production stages. J. Food Prot. 68(11) 2269 – 2277.

Zasadowski, A.; Amarowiez, R.; Barsri, D. and Terlecka, A. (1991): Residues of polychlorinated pesticides in fat, liver and brain of cattle and pigs from the region of Varnia and Mazuria (1981, 1888). Bromatol. CHEM. Toksykol. 24 (3 – 4): 317.