The Role of Bacteria in the Health Potential of Yogurt

Fig. 1. Yogurt as often seen and consumed. Courtesy of http://beezwaxpromo.com

Introduction

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The Biochemistry Behind Yogurt

Fig. 2. Overview of biochemical processes in yogurt production. Courtesy of The Food and Agriculture Organization of the United Nations.

Fig. 3. Lactose catabolism into glucose and galactose. Courtesy of Thomas M. Terry at the University of Hamburg.

Fig. 4. Glycolysis and homolactic fermentation. Courtesy of Dr. Todar's Online Textbook of Bacteriology.

Introduce the topic of your paper. What microorganisms are of interest? Habitat? Applications for medicine and/or environment?

Yogurt Production

Fig. 5. Scanning electron micrograph of Lactobacillus bulgaricus. Courtesy of The Microscopy Facility at Utah State University.

Fig. 6. Scanning electron micrograph of Streptococcus thermophilus. Courtesy of Dennis Kunkel Microscopy, Inc.

Benefits of Yogurt

Include some current research, with at least one figure showing data.

Fig. 7. Bacterial enzyme activities (µmol/min per gram of protein) in fecal samples obtained from non-yogurt consumers (Group N) and yogurt consumers (Group Y). Only β-galactosidase activity levels were significantly different. Figure courtesy of Alvaro et al., 2007.

Probiotics

Fig. 8. Beneficial effects and therapeutic applications of probiotics as proposed by Fuller (1989). Courtesy of Lourens-Hatting and Viljoen (2001).

Include some current research, with at least one figure showing data.

Fig. 9. Scanning electron micrograph of Lactobacillus casei. Courtesy of The Microscopy Facility at Utah State University.

Fig. 10. Gram stain of Lactobacillus acidophilus. Courtesy of Dr. Todar's Online Textbook of Bacteriology.

Fig. 11. Scanning electron micrograph of Bifidobacterium. Courtesy of Dr. Sandy Smith, Dept. of Food Science, University of Guelph, Canada.

Fig. 12. The effect of probiotics on suppressing Helicobacter pylori density and infection. (A) Number of H. pylori colonies depending on the concentration and type of probiotic bacteria present on the plate. La5 refers to Lactobacillus acidophilus and Bb12 refers to Bifidobacterium lactis. (B) Characteristics of biopsy sites before and after yogurt treatment containing La5 and Bb12. H. pylori density was graded from 0 to 5, while activity of gastritis and gastric inflammation were graded on a scale of 0 to 4. Each value is a sum of 2 biopsies. Courtesy of Wang et al., 2004.

Fig. 13. The amount of ACE-inhibitory activity as depicted by the bars and IC50, the sample concentration in mg/mL of probiotic cultures in soy yogurt needed to inhibit ACE activity by 50%, as depicted by the lines. Fermentation was halted at pH 4.50 and the samples were stored at 4°C for 28 days. Courtesy of Donkor et al., 2005.

Improving Yogurt

Current Problems

Include some current research, with at least one figure showing data.

Fig. 14. Hydrolytic breakdown of lactoferricin, as indicated by the % peptide remaining, at pH 7.0 by various strains of L. bulgaricus and S. thermophilus. Courtesy of Paul and Somkuti, 2010.

Fig. 15. Hydrolytic breakdown of a hypotensive peptide by various strains of L. bulgaricus and S. thermophilus at different pH values. Courtesy of Paul and Somkuti, 2009.

Improving functionality of Yogurt

Fig. 16. The stimulating effect of various prebiotics on probiotic growth and function. Courtesy of Ranadheera, Baines, & Adams, 2009.

Towards a "Superior" Yogurt

Fig. 17. The difference in change in % acidity over time between two levels of dissolved oxygen. The culture contained both L. bulgaricus and S. thermophilus. (A) Experiment carried out at 43°C. The circle represents the reduced oxygen fermentation treatment and the square represents the control with normal levels of dissolved oxygen. (B) Experiment carried out at a lower temperature of 37°C. The circle represents the reduced oxygen fermentation treatment and the triangle represents the control with normal levels of dissolved oxygen. Courtesy of Horiuchi et al., 2009.

Fig. 18. Evaluation of the taste and sensation of yogurt produced under varying conditions. A represents low-temperature (37°C) reduced dissolved oxygen fermentation and B represents the control fermentation at 43°C. Each characteristic was evaluated on a scale of 1 to 5 by 200 yogurt consumers. Courtesy of Horiuchi et al., 2009.

Fig. 19. Difference in firmness and appearance between the control yogurt produced at 37°C and the yogurt produced by low temperature (37°C) reduced dissolved oxygen fermentation. Courtesy of Horiuchi et al., 2009.

Conclusion

Overall text length at least 3,000 words, with at least 3 figures.

References

[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.

Adolfsson, O., S. N. Meydani, & R. M. Russell. 2004. Yogurt and gut function. Am J Clin Nutr. 80:245–256.

Akalin, A. S., G. Unal., & M. C. Dalay. 2009. Influence of Spirulina platensis biomass on microbiological viability in traditional and probiotic yogurts during refrigerated storage. Ital. J. Food Sci. 21: 356-364.

Akalin, A. S., S. Gonc, G. Unal, & S. Fenderya. 2007. Effects of frutooligosaccharide and whey protein concentrate on the viability of starter culture in reduced-fat probiotic yogurt during storage. Journal of Food Science. 72: M222-M227.

Alvaro, E., C. Andrieux, V. Rochet, L. Rigottier-Gois, P. Lepercq, M. Sutren, P. Galan, Y. Duval, C. Juste, & J. Dore. British Journal of Nutrition. 97: 126–133.

Cornell University Milk Quality Improvement Program. “Yogurt Production.” 29Dec.2006. <http:// www.milkfacts.info/>

Farnworth, E. R., I. Mainville, M.-P. Desjardins, N. Gardner, I. Fliss, & C. Champagne. 2007. Growth of probiotic bacteria and bifidobacteria in a soy yogurt formulation. Journal of Food Microbiology. 116: 174-181.

Gaetke, L.. M., C. J. McClain, C. J. Toleman, and M. A. Stuart. 2010. Yogurt protects against growth retardation in weanling rats fed diets high in phytic acid. Journal of Nutritional Biochemistry. 21: 147-152.

Guarner, F., G. Perdigon, G. Corthier, S. Salminen, B. Koletzkos, & L. Morelli. 2005. Should yoghurt cultures be considered probiotic? Brit. J. or Nutr. 93: 783-786.

Guzel-Seydim, Z. B., E. Sezgin, and A. C. Seydim. 2005. Influences of exopolysaccharide producing cultures on the quality of plain set type yogurt. Food Control. 16: 205-209.

Horiuchi, H., N. Inoue, E. Liu, M. Fukui, Y. Sasaki, and T. Sasaki. 2009. A method or manufacturing superior set yogurt under reduced oxygen conditions. Journal of Dairy Science. 92: 4112-4121.

Kitawaki, R., Y. Nishimura, N. Takagi, M. Iwasaki, K. Tsuzuki, and M. Fukuda. 2009. Effects of Lactobacillus fermented soymilk and soy yogurt on hepatic lipid accumulation in rats fed a cholesterol-free diet. Biosci. Biotchnol. Biochem. 73: 1484-1488.

Paul, M. and G. A. Somkuti. 2009. Degradation of milk-based bioactive peptides by yogurt fermentation bacteria. Lett Appl Microbiol. 49:345–350

Paul, M. and G. A. Somkuti. 2010. Hydrolytic breakdown of lactoferricin by lactic acid bacteria. J Ind Microbiol Biotechnol. 37:173–178.

Ramchandran, L. & N. P. Shah. 2008. Effect of Versagel® on the growth and metabolic activities of selected lactic acid bacteria. Journal of Food Science. 73: M21-M26.

Roberfroid, M. B. 2000. Prebiotics and probiotics: are they functional foods? Am J Clin Nutr. 71:1682S–7S.

Schrezenmeir, J. & M. Vrese. 2001. Probiotics, prebiotics, and synbiotics—approaching a definition. Am J Clin Nutr. 73:361S–4S.

Seo, M. H.,S. Y. Lee , Y. H. Chang, & H. S. Kwak. 2009. Physicochemical, microbial, and sensory properties of yogurt supplemented with nanopowdered chitosan during storage. J. Dairy Sci. 92: 5907-5916.

Shah, N. P. 2000. Probiotic bacteria: Selective enumeration and survival in dairy foods. J. Dairy Sci. 83:894-907.

Slonczewski, J.L. and J.W. Foster. Microbiology: An Evolving Science. New York. W.W. Norton & Company, Inc., 2009. Pp. 595.

Vasiljevic, T., T. Kealy, & V. K. Mishra. 2007. Effects of β-glucan addition to a probiotic containing yogurt. J. Food Sci. 72: C405-411.

Wang, K.-Y., S.-N. Li, C.-S. Liu, D.-S. Perng, Y.-C. Su, D.-C. Wu, C.-M. Jan, C.-H Lai, T.-N. Wang, & W.-M.

Wang. 2004. Effects of ingesting Lactobacillus- and Bifidobacterium-containing yogurt in subjects with colonized Helicobacter pylori. Am J Clin Nutr. 80: 737-741.

Wollowski, I. S.-T. Ji, A. T. Bakalinsky, C. Neudecker, & B. L. Pool-Zobel. 1999. Bacteria used for the production of yogurt inactivate carcinogens and prevent DNA damage in the colon of rats. J. Nutr. 129: 77–82.

Edited by student of Joan Slonczewski for BIOL 238 Microbiology, 2010, Kenyon College.