Abstract
In the present study, we have evaluated the microbiological quality of walnut kernels and pasteurized apple juice concentrate and the application of PCR for quality control of these important horticultural products. PCR assays for the detection of Bacillus cereus, Salmonella, Escherichia coli and E. coli O157:H7 were standardized using minimum time for each step of the reaction. The protocols were effective for their detection in these products after pre-enrichment for 6–12 h. 2, 68 and 30% of the samples of walnut kernels were respectively found satisfactory, acceptable and unsatisfactory on the basis of their viable count. Only 15% of the samples of pasteurized apple juice concentrate were found to possess the desired viable count of less than 100 c.f.u./ml. The predominant contaminants of walnut kernels were found to be the species of Bacillus, Klebsiella, Enterobacter and Staphylococcus. Samples of apple juice concentrate were predominantly found contaminated with species of Bacillus, Staphylococcus and Micrococcus. However, B. cereus, Salmonella and E. coli were also isolated from some of the samples of walnut kernels. Bacillus cereus was also obtained from some of the samples of pasteurized apple juice concentrate in high numbers. Among the moulds Penicillium, Aspergillus, Cladosporium, Rhizopus and Mucor were isolated from these products.
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References
American Public Health Association. 1992 In Compendium of Methods for the Microbiological Examination of Foods, 3rd edn. eds. Vanderzant, C. & Splittstoesser, D.F. Washington, DC: APHA technical committee on microbiological methods for foods. ISBN 0-87553173-3.
Bergey's Manual of Systematic Bacteriology 1994 Krieg, N.R. (ed.) vol. 1, pp. 465-469. Baltimore, MD USA: Williams and Wilkins, ISBN 0-683-04108-8(v.1).
Betley, M.J., Miller, V.L. & Mekalanos, J.J. 1986 Genetics of Bacterial Enterotoxins. Annual Review of Microbiology 40, 577–605.
Border, P.M., Howard, J.J., Plastow, G.S. & Siggens, K.W. 1990 Detection of Listeria species and Listeria monocytogenes using polymerase chain reaction. Letters in Applied Microbiology 11, 158–162.
Cappuccino, J.G. & Sherman, N. 1996 Microbiology, a Laboratory Manual, 4th edn. Redwood City, California: The Benjamin/Cummings Publishing Company, ISBN 0-80530573-4.
Fang, T.J., Chen, C.Y. & Kuo, W.Y. 1999 Microbiological quality and incidence of S. aureus and B. cereus in vegetarian food products. Food Microbiology 16, 385–391.
HCAC (House of Commons Agriculture Committee). 1997 Minutes of Evidence Dec. 2, 1997. London: Public health laboratory service. Stationary Office, pp. 82–83.
Healthy Nut Initiative. Jan. 1998 Nuts and Aflatoxins: data, facts, background. The Executive Committee of The Healthy Nut Initiative, eds. Dankert, H., Berndt, R., Calcagni, G., Goldman, C., Payne, W., Soetaert, D. & Rafii, A. International Tree Nut council. Hamburg.
ICMSF. 1996 Bacillus cereus in Microorganisms in Foods 5. Characteristics of Microbial Pathogens, eds. Roberts, T.A., Baird-Parker, A.C. & Tompkin, R.B. London: Blackie Academic & Professional, ISBN 0412 47350 X, pp. 20–35.
Lampel, A.K., Orlandi, P.A. & Kornegay, L. 2000 Improved template preparation for PCR-based assays for detection of foodborne bacterial pathogens. Applied and Environmental Microbiology 66, 4539–4542.
Peng, H., Ford, V., Frampton, E.W., Restaino, L., Shelef L.A. & Spitz, H. 2001 Isolation and enumeration of Bacillus cereus from foods on a novel chromogenic plating medium. Food Microbiology 18, 231–238.
PHLS Advisory Committee for Food and Dairy products. 2000 Guidelines for the microbiological quality of some ready to eat foods sampled at the point of sale. Community Disease and Public Health 3, 163–167.
Pitcher, D.G., Saunders, N.A. & Omen, R.J. 1989 Rapid extraction of bacterial genomic DNA with guanidium thiocynate. Letters in Applied Microbiology 8, 151–156.
Roberts, D., Hooper, W. & Greenwood, M. eds. 1995 Practical Food Microbiology. London: Public Health Laboratory Service, ISBN 0901144363.
Saiki, R.K., Gelfand, D.H., Stoffel, S., Scharf, S.J., Higuchi, R., Horn, G.T., Mullis, K.B. & Erlich, H.A. 1988 Primer directed enzymatic amplification of DNA with a thermostable DNA polymerase. Science 239, 487–491.
Schmieg, D.M. & Sofos, J.N. 1997 Detection of Shigella by PCR following filtration and minimal enrichment. Science Forum Poster (Abstract No. A28).
Thomas, E.J.G., King, R.K., Burehak, J. & Gannon, V.P.J. 1991 Sensitive and specific detection of L. monocytogenes in milk and ground beef with the polymease chain reaction. Applied and Environmental Microbiology 57, 2576–2580.
USFDA/CFSAN 1999 Foodborne disease outbreak articles and databases of interest. Bad Bug book 1-3 (http://www.cfsan.fda. gov/~mow/app5.html.)
Westbrook, G.L., O'Hara, C.M., Roman, S.B. & Michael, J. 2000 Incidence and identification of Klebsiella planticola in clinical isolates with emphasis on newborns. Journal of Clinical Microbiology 38, 1495–1497.
Whelen, A.C. & Persing, D.H. 1996 The role of nucleic acid amplification and detection in the clinical microbiology laboratory. Annual Review of Microbiology 50, 349–373.
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Riyaz-Ul-Hassan, S., Verma, V., Malik, A. et al. Microbiological quality of walnut kernels and apple juice concentrate. World Journal of Microbiology and Biotechnology 19, 845–850 (2003). https://doi.org/10.1023/A:1026052112401
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DOI: https://doi.org/10.1023/A:1026052112401