EC Microbiology

Research Article Volume 19 Issue 6 - 2023

Determination of Microbial Isolates Contamination of Yoghurt from Different Factories in Dohuk City

Warveen I Abdulrhman1 and Karkaz M Thalij2*

1College of Agriculture, Dohuk University, Dohuk, Kurdistan Region, Iraq

2Department of Food Science, Tikrit University, Tikrit, Iraq

*Corresponding Author: Karkaz M Thalij, Department of Food Science, Tikrit University, Tikrit, Iraq.
Received: March 28, 2023; Published: April 10, 2023



This study was conducted to the identification of microbial species isolates that contaminated yoghurt samples and to determine the viable microbial total counts, also the coliform counts, Staphylococcus, lactic acid bacteria (LAB) and the fungi counts, in addition to the pH levels after storage the samples for 7 or 30 days in refrigerator temperature at 5ºC from eight dairy factories in Dohuk city.

The results were shows that the total viable microbial counts significantly increased (p < 0.05) and appeared between log 6.25 to 9.25 CFU/ml after the end storage period, while, the LAB significantly decreased in all yoghurt samples and became between log 4.23 to 4.60 CFU/ml, compared with the counts at initial storage at between log 8.14 to 12.20 CFU/ml. The coliform, Staphylococcus and fungal isolates were found only at the end of yoghurt samples storage periods and some of its samples were not to detected in its. The range of pH for all yoghurt samples at the end of storage periods was 3.62 to 4.05 compared with the range at the initial storage periods at 3.97 to 4.40. The microbial isolates from yoghurt samples were the Staphylococcus sp., E. coli, Klebsiella sp. and Pseudomonas luteola, Lactobacillus bulgaricus, Aspergillus sp., Penicillium sp., and the yeast in all of the samples. Also, it that appears some bacterial isolates were completely resistant to antibiotics.

Keywords: Yoghurt; Microbial Contamination; Dairy Factories; Safety; Dohuk

  1. Mozaffarian D and Wu JHY. “Flavonoids, Dairy Foods, and Cardiovascular and Metabolic Health: A Review of Emerging Biologic Pathways”. Circulation Research 122 (2018): 369-384.
  2. Giosuè A., et al. “Consumption of Dairy Foods and Cardiovascular Disease: A Systematic Review”. Nutrients 14 (2022): 831-851.
  3. Harper AR., et al. “Fermentation of plant-based dairy alternatives by lactic acid bacteria”. Microbial Biotechnology5 (2022): 1404-1421.
  4. Naibaho J., et al. “Fortification of milk-based yogurt with protein hydrolysates from brewers’ spent grain: Evaluation on microstructural properties, lactic acid bacteria profile, lactic acid forming capability and its physical behavior”. Current Research in Food Science 5 (2022): 1955-1964.
  5. El-Sayed AS., et al. “Detection of Potential Microbial Contaminants and Their Toxins in Fermented Dairy Products: a Comprehensive Review”. Food Analytical Methods 15 (2022): 1880-1898.
  6. Gao X., et al. “Yogurt Intake Reduces All-Cause and Cardiovascular Disease Mortality: A Meta-Analysis of Eight Prospective Cohort Studies”. Chinese Journal of Integrative Medicine 26 (2020): 462-468.
  7. Akinyemi MO., et al. “A review of microbes and chemical contaminants in dairy products in sub-Saharan Africa”. Comprehensive Reviews in Food Science and Food Safety2 (2021): 1188-1220.
  8. Roberts D and Greenwood M. “Practical food microbiology”. 3rd edition, Blackwell publishing Inc., 350 Malden, Massachusetts 02148-5018, USA (2003).
  9. Maza LM., et al. “Color Atlas of Medical Bacteriology, 3edition”. American Society for Microbiology, Willey (2020): 434.
  10. Willey J., et al. “Prescott's Microbiology 11th Edition”. McGraw-Hill Higher Education. USA (2020).
  11. Winn CW., et al. “Koneman's Color Atlas and Textbook of Diagnostic Microbiology”. Sixth Edition, Lippincott Williams Wilkins (2006).
  12. Watanabe A. Pictorial atlas of soil and seed fungi, morphologies of cultured fungi and key to species 2nd edition, CRC Press LLC (2002).
  13. Jorgensen JH and Turnidge JD. “Susceptibility test methods: dilution and disk diffusion methods, p: 1152-1172”. In Murray PR, Baron EJ, Jorgensen JH, Landry ML, Pfaller MA. (edition), Manual of clinical microbiology, 9th edition. ASM Press, Washington, D.C (2007).
  14. Clinical and Laboratory Standards Institute (CLSI). Performance standards for antimicrobial susceptibility Testing; Thirty informational supplement. Approved standard M100-S25. CLSI, Wayne, PA (2020).
  15. SAS Version. “Statistical Analysis System”. SAS Institute Inc., Cary, NC. 27512 - 8000, U.S.A (2001).
  16. Duncan DB. “Multiple range and F; test”. Biometric 11 (1955): 42.
  17. Rad AH., et al. “The safety perspective of probiotic and non-probiotic yoghurts: a review”. Food Quality and Safety 3 (2019): 9-14.
  18. Toghyani M., et al. “Effect of probiotic and prebiotic as antibiotic growth promoter substitutions on productive and carcass traits of broiler chicks”. International Conference on Food Engineering and Biotechnology 9 (2011): 82-86.
  19. COSQC, Central Organization for Standardization and Quality Control. ISO 22000:2018 Food safety management systems - A practical guide (2018): 1-18.
  20. Reuben RC., et al. “Isolation, characterization, and assessment of lactic acid bacteria toward their selection as poultry probiotics”. BMC Microbiology 19 (2019): 253-273.
  21. Singh P and Gandhi N. “Milk Preservatives and Adulterants: Processing, Regulatory and Safety Issue”. Food Reviews International3 (2015): 236-261.
  22. Güler-Akin MB. “The effects of different incubation temperatures on the acetaldehyde content and viable bacteria counts of bio-yoghurt made from ewe's milk”. International Journal of Dairy Technology3 (2005): 174-179.
  23. Jakubowska M and Matusevicius T. “The Effect of Storage Time and Temperature on the Quality of Natural Yoghurt”. Acta Scientiarum Polonorum Zootechnica4 (2019): 29-38.
  24. Jankowska A and Reps A. “Factors affecting the shelf-life of yoghurt during storage [Czynniki decyduj ˛ace o trwałosci ´ jogurtu podczas przechowywania]”. Mlecz 11 (2013): 2-5.
  25. Eissa EA., et al. “Physicochemical, microbiological and sensory characteristics of yoghurt produced from goat milk. Livestock Res”. Rural Development8 (2010): 23-31.
  26. Kisanthini S and Kavitha MB. “Microbial Contamination of Yoghurt-An Overview”. International Journal of Science and Research (IJSR)3 (2021): 954-957.
  27. Sarkar MM., et al. “Chemical and bacteriological quality of popular Dahi available in some selected areas of Bangladesh”. Bangladesh Journal of Animal Science1 (2012): 47-51.

Warveen I Abdulrhman and Karkaz M Thalij. “Determination of Microbial Isolates Contamination of Yoghurt from Different Factories in Dohuk City”. EC Microbiology  19.6 (2023): 08-16.