The text of this blog article was originally written by Amy Tsang, a 3rd-year food technology student of mine at RMIT University in 2009. I have provided some slight updates/changes/revisions. While probiotics now exist (for example, Bacillus coagulans) that are able to withstand pasteurisation and high pressure processing, there’s no doubt of the ongoing importance of the issue of viability of probiotics, given adequate amounts of the organisms reaching the appropriate place in the gastrointestinal tract is a requisite for their success, and the multitude of factors that can negatively impact probiotic survival during manufacture, in food and during gastrointestinal passage, as noted in the image above.
Probiotics continue to attracted much interest from consumers; who are concerned with their personal diet and lifestyle. These consumers expect that the functional foods they consume will exert clear health benefits for their digestive system; especially in Europe where gut health is a key component for the benefits provided by functional foods (Mattila-Sandholm et. al, 2002). Future research into probiotics may also help to alleviate many health issues such as allergies or even particular types of cancers. Currently there are many studies focused on probiotic survival through the gastrointestinal environment.
Misconceptions about probiotics need to be defended when placed under scrutiny (Gorbach, 2002). To counter misconceptions of probiotics, detailed research and human/clinical studies need to be conducted by scientists to prove to consumers that probiotics have health promoting properties. In addition, consumer education is also important; if probiotics were to become a part of the daily diet; appropriate scientific facts and information should be made readily available for consumers. Without consumer confidence, the probiotic industry would not prosper.
There are several major issues that need to be addressed before developing new probiotic products or re-formulating products for consumption. The viability and stability of probiotics and maintaining an acceptable number of viable cells above food standard requirements throughout the whole shelf life of the product and ensuring specific probiotic strains are chosen that can withstand the gastrointestinal stresses present in that environment; these have all been major challenges for the food industry (Mattila-Sandholm et. al, 2002). These requirements highlight the need for innovative solutions such as new technological advancements; however maintenance of low production costs will also be high on the agenda as the solutions need to be financially viable for food manufacturers and consumers alike.
Yoghurt, a popular dairy product with probiotic health benefits, has established the foundations for further research into other potential probiotic functional foods such as; probiotic drinks, non dairy beverages; vegetable and fruit juices, desserts for vegetarians, baby foods, and cereal based products (Mattila-Sandholm et. al, 2002; Heenan, 2004 et. al; Prado et. al, 2008; Lee & Salminen, 1995).
Various ideas towards the method of benefit offered by probiotics have been hypothesised. Although these significant methods have not been completely established, the possibilities include; rivalry for nutrients, secretion of microbial substances, blocking of adhesion sites, decrease in virulence, blocking of toxin receptor sites, immune stimulation and suppression of toxin production (Fooks et. al, 1999). The competition for nutrients is quite a significant factor for any bacteria thriving in the gastrointestinal tract. Various bacterial species are quite specific in their nutritional requirements and so one particular population may deplete nutrients at the expense of another species (Fooks et. al, 1999); thus if probiotics were used in this circumstance it would be highly beneficial to the gut flora, where health promoting bacteria may predominate. In general terms, probiotic foods and supplements are expected to restore the balance in the gut; given there are sufficient numbers, which is generally 106 cfu/g (Elahi et.al, 2008; Lee & Salminen, 1996).
Probiotic effectiveness can be further enhanced with the inclusion of probiotics for a symbiotic effect. According to (Fooks et. al, 1999) this combination of one probiotic with another probiotic can enhance the survival of probiotic bacteria overall.
To further highlight the importance of probiotic bacterial survival, there are also other issues to consider. Although probiotic bacteria in food products may be able to survive the initial fermentation, production process; the storage and the gastrointestinal tract are also of great concern, probiotic bacteria may be susceptible to extreme and harsh environments. As discussed by (Lacroix & Yildirim, 2007) the storage conditions can have an impact on probiotic bacteria such as oxygen stress, competition with other organisms, variability in temperature and moisture content, given that the probiotic bacteria do survive during storage they are then exposed to the gastrointestinal tract.
Furthermore, the gastrointestinal tract will have extreme acidic conditions present in the stomach and enzyme activity will be present, thus the composition of the environment may not favour the probiotic bacteria and presence of bile salts in the small intestine may inhibit the growth of the probiotic bacteria ingested (Lacroix & Yildirim, 2007). These are typical stresses which probiotic bacteria may be subjected to, therefore probiotic bacteria chosen for products should be those that can adapt to extreme conditions and changing environments (Lacroix & Yildirim, 2007). Therefore due to such conditions, it is not always likely that sufficient numbers of probiotic bacteria will reach the appropriate gut location to exert their beneficial health effects. A research project was conducted by (Gibson & Brostoff, 2005 – apologies, citation details cannot be found!) to test commercially available supplements that contained strains of probiotic bacteria and their survival in the gastrointestinal environment. Their results demonstrated that Lactobacillus spp. were resistant to the gastric environment, however they were sensitive to the upper intestinal content, on the contrary Bifidobacterium spp. displayed sensitivity to the stomach environment but were able to survive well in the upper intestine. This study highlighted the significance of different probiotic species and their diverse capacity to survive within the intestinal environment.
References
Elahi, S., Farnell, P., Thurlow, K. J., Scotti, C., Varnam, A. H., 2008, ‘Referee analysis of probiotic food supplements’. Food Control, vol 19, pp. 925-929.
Fooks, L. J., Fuller, R., Gibson, G. R., 1999, ‘Prebiotics, probiotics and human gut microbiology’. International Dairy Journal, vol 9, pp. 53-61.
Gorbach, S. L., 2002, ‘Probiotics in the Third Millennium,’ Digest Liver DIS, vol. 34.
Heenan., C. N., Adams, M. C., Hosken, R.W., Fleet, G.H., 2004, ‘Survival and sensory acceptability of probiotic microorganisms in a nonfermented frozen vegetarian dessert,’ Lebensm.-Wiss. U.- Technol, vol. 37,pp. 461-466.
Lee, Y. L., & Salminen, S. 1996, ‘The coming of age of probiotics.’ Trends in Food science and Technology,’ vol 6, pp. 241-245.
Lacroix, C., & Yildirim, S., 2007, ‘Fermentation technologies for the production of probiotics with high variability and functionality,’ Current Opinion in Biotechnology, vol 18, pp.176-183.
Mattila-Sandholm, T., Myllärinen. P., Cittenden, R., Mogensen, G., Fonden, R., Saarela, M., 2002, ‘Technological challenges for future probiotic foods,’ International Dairy Journal, vol. 12, pp. 173-182.
Prado, F.C., Parada, J. L., Pandey, A., Soccol, C. R., 2008, ‘Trends in non-dairy probiotic beverages,’ Food Research International, vol. 41, pp. 111-123.
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