"The use of riboflavin-producing strains in the production of dairy products such as fermented milk, yoghurt, and cheese is feasible and economically attractive because it would decrease the costs involved during conventional vitamin fortification and satisfy consumer demands for healthier foods," explained lead author Jean Guy LeBlanc in the journal Nutrition (Vol. 22, pp. 645-651).
Riboflavin, also known as vitamin B2, is found in a range of foods like dairy, fish, and various vegetables. Deficiency in the vitamin is common in many parts of the world, not simply confined to the developing countries, but also reported in the elderly and young adults in some industrialized nations.
The research is a collaboration between the National Council of Scientific and Technical Investigations and the National University of Tucuman in Argentina, and NIZO Food Research and Campina Innovation in The Netherlands.
The researchers fed rats a riboflavin-deficient diet for 21 days and then fed the animals the same diet supplement with one of three yoghurts for 28 days.
Three different batches of yoghurt were produced: a conventional yoghurt (control); a yoghurt with Propionibacterium freudenreichii NIZO B374 (wild bacterial strain with low riboflavin production); and a yoghurt with P. freudenreichii NIZO B2336 (a mutant strain of B374 with increased riboflavin production).
At the end of the experiment the authors found that the riboflavin content of the yoghurt was almost doubled using the B2336 strain, compared to the B374.
Riboflavin status, measured in terms of the erythrocyte glutathione reductase activation coefficient (EGRAC), was found to be improved in the B2336 yoghurt compared to those eating the B374 yoghurt and the normal (control) yoghurt.
Physiological signs of riboflavin deficiency in the animals, such as stunted growth, were also improved in the B2336 yoghurt group. The growth rate of the control yoghurt group was 1.71 grams per day. The B2336 yoghurt group had reported growth rates of 3.28 grams per day. This was still less however than rats with no riboflavin depletion (5.34 grams per day).
"These results clearly show that the use of P. freudenreichii B2336 as an adjunct culture in yoghurt fermentation increased the riboflavin content, with similar bioavailability as the commercially available vitamin, thereby improving the nutritional value of yoghurt and eliminating the costly need to fortify this fermented milk product with vitamin B2," said the researchers.
According to the scientific article, the bacterial riboflavin-enriched dairy products were prototypes. No-one from either NIZO Food Research or Campina was available to comment if the products are being developed for commercialisation.
The authors point out that such spontaneously riboflavin overproducing strains are not classified as genetically engineered organisms and, according to European Council Directive 90/220/EEC, can be used industrially for human consumption.
"Propionibacterium freudenreichii B2336 could be used for the production of yoghurt or fermented milk to increase levels of riboflavin, thus increasing their commercial and nutritional value," concluded the researchers.
The work was funded through the EU-funded NutraCells project that has also seen spontaneously folate-producing bacteria and their use in dairy products.