Assessment Of Nunu Produced Using Pure Starter Culture

Project and Seminar Material for Microbiology

Assessment Of Nunu Produced Using Pure Starter Culture


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.


Table of Content

Chapter One

1.0 Introduction

  • 1.1 Aim of the Study
  • 1.2 Objectives of the Study
  • 1.3 Significance of the Study
  • 1.4 Scope and Limitation

Chapter Two

2.0 Literature Review

  • 2.1 Lactobacillales
  • 2.2 Characteristics of Lab
  • 2.3 Metabolism of Lab
  • 2.4 Scientific Review of Lab
  • 2.5 Lactic Acid Fermentation
  • 2.6 Application of Lactic Acid Bacteria in Health and Disease
  • 2.7 Industrial Uses of Lab
  • 2.8 Lab as a Probiotic

Chapter Three

3.0 Material and Methods

  • 3.1 Sample Collection
  • 3.2 Sterilization and Disinfection of Material
  • 3.3 Media Used
  • 3.3.1 Preparation of Media
  • 3.4 Nunu Preparation
  • 3.5 Microbiological Analysis
  • 3.5.1 Isolation of Bacteria Strain
  • 3.6 Morphological and Biochemical Test
  • 3.6.1 Gram Staining
  • 3.6.2 Catalase Test
  • 3.6.3 Mortility Test
  • 3.6.4 Glucose Fermentation Test
  • 3.6.5 Physico-Chemical Analysis
  • 3.6.6 Sensory Evaluation
  • 3.6.7 Determination of Shelf-Life
  • 3.7 Identification of Lab

Chapter Four

4.0 Result and Analysis

  • 4.1 Isolation And Identification of Lab
  • 4.2 Physio-Chemical Analysis of Nunu

Chapter Five

5.0 Discussion, Conclusion and Recommendation

  • 5.1 Introduction
  • 5.2 Conclusion
  • 5.3 Recommendation
  • References


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

  1. To inoculate pure starter culture into freshly prepared ‘Nunu’.
  2. To isolate and enumerate Lactic Acid Bacteria present in the produced ‘Nunu’.
  3. To isolate, characterize and enumerate other microorganisms present in the produced ‘Nunu’.
  4. 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.

Chapter Five

5.0 Discussion, Conclusion and Recommendation

5.1 Introduction

Many traditional fermented milk products were made in Asia, Africa, the middle East and Northern and Eastern Europe (Savadogoet al.,2004). Studies on the microbiological characteristics of several fermented milk products have been carried out in countries such as Indonesia (Yodoamijoyoet al., 1983; Hosonoet al., 1989); Zimbabwe ( Mutukumira,1995;Gadaga et al.,1999); South Africa (Keller and Jordan,1990; Beukeset al.,2001); Morocco (Hamama,1992); Tanzania( Isonoet al.,1994); Burkinafaso (Savadogoet al.,2004); Sudan (Abdelgadinet al.,1998 and 1994); Nigeria (Eka and Ohaba, 1977, Atanda and Ikenebom,1989) and Ethopia (O’Connor et al.,1993: O’Mahony,1988).

The nature of fermented products depends on the local indigenous microflora which in turn reflects the climatic conditions of the area (Savadogoet al.,2004). Thus traditional fermented milk in regions with a cold climate contained Mesophilic bacteria such as Lactococcus and LeuconostocSpp. While Thermophilic bacteria, which include mostly Lactobacillus and Streptococcus prevailed in regions with a hot, subtropical or tropical climate (Thomas, 1985; Tamine and Robinson, 1988; Kurmann, 1984).

This fermented milk product, nunu, are consumed as food and the market value and storage life are improved over that of raw milk 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 product (Tannock, 2004).

LAB starter culture for the production of nunuwas isolated from purchased nunu samples which confers desirable flavor characteristics in certain products (Marshall,1987).

Generally, result shown that the pH of all the nono samples decreased as the milk fermented. This agreed with the work of Oyewole (1990). Who stated that the acidity of fermenting milk is normally only noticeable when the pH falls to about 5.5. This showed that the LAB inoculated into the pasteurized milk were able to carry out acid fermentation which resulted in the production of lactic acid. AchiAkobor (2000) and Nout (1991) also reported the decrease in pH during fermentation process of traditional fermented food products.

Fenwema (1985) also established in his earlier report that pasteurization and fermentation with starter culture improve the flavor and taste of milk products.

5.2 Conclusion

Various LAB do exist in the nunu sample that was collected from the Fulani local producers in the permanent site, University of Abuja, Abuja. The result obtained showed four(4) isolates of Lactic Acid Bacteria which can be grouped into four(4) genera of Lactobacillus, Leuconostoc, Lactococcus and Pediococcus.

The bacteria colonies of LAB counted from the petri dishes concurring with the work of Giraffa (1998).

Lactic Acid Bacteria contributes to the enormous demands on fermented food and has been proven to be used as starter culture in the improvement of nutritional properties, better flavor or aroma, upgrading of substances to higher value products and improved health aspect. Milk fermented with mixed starter culture of LAB had the highest quality and acceptability as was evident in this project work (Fenwema,1985). The result also showed that the pH dropped from 6.29- 5.58 and this is because LAB inoculated into the pasteurized milk were able to carry out acid fermentation which resulted in the production of lactic acid. Also nunu produced with starter culture possess antimicrobial properties and when stored at refrigerated temperature not only improved the flavor but also extended its shelf-life.

5.3 Recommendation

  1. Lactic acid bacteria contribute to enormous nutritional and health benefits. Extensive work should be performed to discover its secrets and importance in the production of nunu.
  2. The research fund and expertise should be extended and harnessed to achieve this purpose.
  3. The micro-organisms isolated from nunu should be characterized using modern molecular methods and the technological properties of the dominant types determined to facilitate selection and development of starter cultures from them for the production of nunu, this way the fermentation process will be controlled thereby increasing the quality of the product.
  4. LAB fermented foods in the diet should be encouraged.
  5. A standard processing method that will ensure nunu of the highest microbial and nutritional quality should be developed and the technology be transferred to the local producers.
  6. To avoid self-contamination of product, critical hazard points should be guided jealously during production coupled with maintenance of environmental and personal hygiene.
  7. Education of producers on good manufacturing practices including basic hygienic principles will equally be crucial in achieving a quality standard product.

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