ABSTRACT
Nunu is Nigerian locally fermented
milk product commonly prepared by Hausa/Fulani cattle rearers. It’s
mostly available in the Northern part of Nigeria. It’s production and
consumption derives food security and economic benefits to the rural
people in the region. However, the process characteristics results in
products which are not appealing to many people. Lactic acid bacteria
are mostly associated with the production of fermented milk products.
They play key role in producing desirable flavour, aroma and good
physical appearance in fermented milk products. Isolation and
identification of LAB from nunu of spontaneous fermentation was carried
out and labeled LAB 1-LAB 4. An assessement of the organoleptic
property, pH, shelf-life and overall acceptability was determined. After
24 hours of fermentation, a general decrease in pH was observed. The pH
ranged between 5.58 - 6.29. Nunu samples fermented with mixed starter
culture, LAB 1+2, had the best sensory evaluation described as ;
fermented, sour, characteristic of the nunu, pleasant, soft, smooth,
semi- solid, viscous and with the highest overall acceptability of 7 on
the hedonic scale. While nunu fermented with Lab3 and Lab 2+3 had a
sensory evaluation of being umami, milk, rough, not pleasant aroma and
gritty with an overall acceptability of 2 on the hedonic scale. The
nunu sample produced stored in refrigerator had a shelf-life of 6 days
while the sample stored at room temperature (28±2oC ) had a shelf-life of 3 days.
CHAPTER ONE
1.0 INTRODUCTION
Nunu is a spontaneously
fermented milk (yoghurt-like) product in Nigeria and other parts of West
Africa including Ghana and Burkina Faso. Unlike other African fermented
milk products where milk of goats, sheep, and camels is used, Nunu is solely prepared from cow milk. The traditional processing of Nunu involves
collecting fresh cow milk into containers and then allowing it to
ferment for a day or two days at ambient temperature. Nunu is yoghurt-like in taste (a sharp acid taste) and it can be taken alone or with Fura (Owusu-Kwarteng et al., 2012; Akabanda et al., 2013). Like many other spontaneously fermented foods in Africa, the production of Nunu is
largely home-based and the fermentation is spontaneous. Thus, starter
cultures are not available, but old stocks of previous ferments and
fermentation containers are used to initiate fermentation in new
batches. The dependence on such undefined and diverse microbial
consortium during Nunu fermentation may result in product of variable quality and stability.
Currently, there is no information on the use of starter cultures for Nunu fermentation.
However, few investigations have been carried out on the microbiology
of Ghanaian traditionally fermented milk products (Obodai and Dodd,2006;
Akabanda et al., 2010). The predominant microorganisms
isolated from this traditionally fermented milk should be developed into
starter cultures that could be used to produce fermented milk products
of consistent quality and consumer acceptability. Thus, it should be
possible to improve the quality and consumer acceptability of Nunu through controlled fermentation using starter culture.
The culture should, however, be
well-defined. Such starter cultures must be developed with a clear
understanding of the ecology of the microbial species associated with
the desirable traditional fermentation process, and their contributions
to the products safety and quality are determined. The first stage in
designing such starter culture(s) is to characterize and identify the
technologically important microorganisms associated with the traditional
fermentation of the product and then to test the use of the identified
organisms in fermentation trials.
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 their application as starter cultures in Nunu production.
1.1 AIM OF THE STUDY
The present study was undertaken with the aim to investigate and assess microorganism present in ‘Nunu’ produced using pure starter culture.
1.2 OBJECTIVES OF THE STUDY
- To inoculate pure starter culture into freshly prepared ‘Nunu’.
- To isolate and enumerate Lactic Acid Bacteria present in the produced ‘Nunu’.
- To isolate, characterize and enumerate other microorganisms present in the produced ‘Nunu’.
- To make useful recommendations based on my findings.
1.3 SIGNIFICANCE OF THE STUDY
The significance of the research is to
assess Lactic acid Bacteria and other microorganisms in ‘Nunu’ (fresh
fermented cow milk) produced using pure starter culture based on
phenotypic characteristics (morphology and physiology).
More especially this study would serve
as a guideline for further research and investigation of the role of
fermented foods as physiological agents and at this point, hopefully
expose the particular peptides and amino acids responsible for
particular physiological roles.
1.4 SCOPE AND LIMITATION
The research work would assess, identify
and enumerate LABs to their generic level as identification to specie
level is strenuous and elaborate.