Viable counts of L. rhamnosus GR-1 were observed after incorporation of the strains in low-fat yoghurt after refrigeration for 28 days, according to results published in the journal Innovative Food Science and Emerging Technologies.
The study is said to be the first to report data on the growth and survival of the two strains in yogurt.
“This study shows that yogurt has the potential to deliver probiotic bacteria to consumers, with L. rhamnosus GR-1 providing excellent shelf life,” wrote lead author Sharareh Hekmat from the University of Western Ontario.
Professor Gregor Reid, lead researcher of the study, told NutraIngredients.com that this is not at the production level, but that there is an opportunity for commercialisation.
Further benefits of the GR1 strain was in its anti-allergy effects which will be published soon. Prof Reid said he would expect companies to be interested in the anti-allergy potential of the strain.
Dairy foods, including fermented milks and yoghurts, are among the best accepted food carriers for probiotic cultures. However, Hekmat and co-workers point out probiotics products should contain at least one million colony forming units per 100 grams if the product is to transfer the probiotic effects to the host.
“Therefore, an important aspect in the manufacture of probiotic products is to ensure that bacterial survival retains its effective dosage at the end of shelf life,” they said.
Study details
The Western Ontario researchers prepared four yoghurt formulations with both probiotic strains and the classic yoghurt starter cultures of Lactobacillus delbreukii sub-species bulgaricus and Streptococcus thermophilus. The first contained milk (1 per cent fat) with a yeast extract, the second contained inulin (0.4 per cent), the third contained the yeast and inulin, and the final one contained no additives.
They report that, in all formulations, L. rhamnosus GR-1 had significantly better survival than L. reuteri RC-14.
“It appears that L. reuteri RC-14 is sensitive to the acidic condition of yogurt, or its viability is adversely affected for other reasons,” wrote the researchers.
“This poor ability of L. reuteri RC-14 to persist in yogurt is not restricted to this species, as other potential probiotic bacteria have also shown an inability to survive well due to intrinsic properties of yogurt, such as pH, and presence of oxygen in the product as well as permeation through the packaging.”
Prof Reid said that, based on the results of this study, L. reuteri RC-14 was dropped from the yoghurt formulation, and GR1 is only used now.
Indeed, he added that L. rhamnosus GR1-containing yoghurt is already in a yoghurt in Tanzania and is part of the University of Western Ontario’s community response to the HIV/AIDS crisis in Africa.
Source: Innovative Food Science and Emerging TechnologiesPublished online ahead of print, doi:10.1016/j.ifset.2008.10.007"Growth and survival of Lactobacillus reuteri RC-14 and Lactobacillus rhamnosus GR-1 in yogurt for use as a functional food"Authors: S. Hekmat, H. Soltani, G. Reid