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Development of functional starter cultures with added values and health benefits for production of the sour milk product 'nono', a traditional Nigerian fermented milk product
Project
Project code: MRI-MBT-08-KA-921-1040 Nono
Contract period: 01.07.2016
- 30.06.2019
Purpose of research: Experimental development
Keywords: fermentation, Nono, product development, Nigeria
The research project aims to scientifically characterize and develop the controlled production of a Nigerian fermented sour milk product called “nono”. The critical step in the development of a controlled processing of nono, is the selection and application of starter cultures. In order to select suitable starters, the biodiversity of lactic acid bacteria involved in typical nono fermentations needs to be characterized and predominant bacteria involved in the fermentation will be investigated for their functional properties relating to their suitability for the fermentation of the product, and to their ability to provide added health benefits, such as production of bioactive peptides in milk as a result of proteolytic activity. Altogether, the project thus aims to obtain a microbiologically safe product of high sensory quality which has an acceptable shelf life and which offers additional health benefits in the form of bioactive peptides by using appropriate starter cultures.
The microbial populations of the Nigerian nono-type products called sallah and kindirimo were characterized. It was found that overall a lactic acid fermentation takes place in the production of these products and that the end products contain 15-20 g/L lactic acid and have a typical pH of 3.5-4.0. These products contain approx. 10^7 to 10^8 bacteria per ml end product. These bacteria appeared to be mostly lactic acid bacteria consisting predominantly of lactobacilli, while streptococci also occurred at a minor proportion. The amounts of streptococci also appeared to decline from 48 h samples to 72 h samples to levels of ca. 10^3 to 10^5 bacteria per ml. The microbial diversity of the fermented products were investigated by metagenomics and it was found that lactic acid bacteria were the predominant bacteria isolated. However, there were differences in the lactic acid bacterial populations between products, as some products contained predominantly lactobacilli and streptococci, while other contained predominantly lactobacilli and lactococci. Gram negative enterobacteria such as Shigella and Escherichia species were also detected. Although it is doubtful that these were actively multiplying in a product with an end pH of under 4.0, the results show that these products are contaminated with pathogenic bacteria. These results clearly show that in order to obtain a product of consistently high quality and safety, starter cultures should be developed. This would ensure that the microbial composition of the products are more stable and consistently similar and that gram-negative pathogens cannot grow. In order to develop potential starter cultures the predominant microorganisms associated with the fermentation needed to be identified. For this reason ca. 150 isolates were genetically fingerprinted and grouped according to their fingerprints. The 16S rRNA gene of representative isolates from each of the groups was sequenced in order to identify the bacteria. Using this approach it could be determined that Lactobacillus fermentum strains, followed by Lactobacillus delbrueckii subsp. bulgaricus and Lactobacillus helveticus strains and homofermentative cocci (to be identified) are the predominant lactic acid bacteria associated with a nono-type fermentation. So far, the complete genomes of three of these representative species (L. fermentum, L. helveticus and L. delbrueckii subsp. bulgaricus) were sequenced in order to determine their potential technological characteristics from the genomic data. Future research will look at the use of combinations of these cultures in the production of laboratory scale nono.
Section overview
Subjects
- Food Processing
- Food microbiology
Framework programme
Funding programme
Excutive institution
MRI - Department of Microbiology and Biotechnology (MRI-MBT)
