The Research Uptake Communications (RUC 2016) Campaign
The Use of Lactic Acid Bacteria Starter Culture in the Production of Nunu, a Spontaneously Fermented
Milk Product in Ghana
Background
Nunu is a spontaneously fermented milk (yoghurt-like) product which is produced solely from cow milk and consumed in Ghana and other parts of West Africa. It is mostly produced at home where old stock of previous ferments serve as starters for the fermentation of new ones. These starters when used may lead to the inconsistency in the quality and stability of the fermented milk due to the presence of varied microorganisms.
There is a need for a well-defined starter culture for the Nunu fermentation which would improve the quality, consistency and consumer acceptability of the milk. There is no information currently on the use of starter cultures for Nunu fermentation but a well-defined starter culture can be designed by characterizing, identifying and testing technologically important microorganisms with relation to the fermentation.
Objective of Study
The objective of the present study was therefore to evaluate the technological potential of lactic acid bacteria isolated from spontaneously fermented Nunu in view of application as starter cultures in Nunu production.
Findings
A total of 373 Lactic Acid Bacteria (LAB) were isolated and identified from spontaneously fermented Nunu and were assessed for their technological properties which include acidification properties, proteolytic activity, lipolytic activity and antimicrobial activities.
From the results obtained, a majority of strains showed fast rate of acidification serving as good candidates for starter cultures. This property only stops the growth of unwanted microorganisms but is also required for the aroma, texture and flavor of the milk (NUNU). The analysis of the proteolytic activity of LAB is not only related to the quality of fermentation obtained but it also accounts for the different organoleptic properties of various fermented milk products. Varying degrees of proteolytic activities were observed from the isolated strains which indicate their ability to serve as starter bacteria.
Lipolysis is employed in the dairy industry to hydrolyse milk fat by the use of microbial lipases. The lipolytic identified by the LAB indicates its potential to be used as a starter for both the hydrolysis of milk and the reduction of cholesterol levels in humans.
All the LAB strains tested produced some amount of exopolysaccahride [EPS] which is known to serve as biothickener which improves the constistency and viscosity of the milk. EPS has added advantages such as reducing cholesterol levels as well as the formation of pathogenic biofilms. These among other properties make the EPS-producing LAB essential in the production of starter cultures.
Lactic acid bacteria isolated from Ghanaian traditional fermented milk product (Nunu) have demonstrated desirable technological properties and have subsequently been successfully used as starter cultures for Nunu fermentation. Lactobacillus fermentum, L. helveticus, and L. plantarum starter cultures (whether used alone or in combination) were able to produce yoghurt with desirable consumer sensory characteristics. Therefore, further development and application of these cultures in commercial Nunu production will improve safety and consumer acceptability of the product.
Research Uptake Communicators:
Mr John Anoku
Mrs Mammie Hutchful Nortey
Authors:
Fortune Akabanda
James Owusu-Kwarteng
Kwaku Tano-Debrah
Charles Parkouda
Lene Jespersen