An Assessment of Nunu Milk Produced Using Pure Starter Culture

ABSTRACT

Nunu is a Nigerian locally fermented milk product commonly prepared by Hausa/Fulani cattle rearers. It’s mostly available in the Northern part of Nigeria. Its production and consumption derive food security and economic benefits to the rural people in the region. However, the process characteristics result in products which are not appealing to many people. Lactic acid bacteria are mostly associated with the production of fermented milk products. They play a 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 were carried out and labelled LAB 1-LAB 4. An assessment 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 a 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 and stored in the 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 the 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 an undefined and diverse microbial consortium during Nunu fermentation may result in products 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 a 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 safety and quality of the product 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 microorganisms present in ‘Nunu’ produced using a 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.

References

1. Yuqing Wu, Ao Li, Lin Cheng, Qianxi Chen, Jiyang Li, Yanqing Xu, Dongxue Huo. (2022) Deep Shotgun metagenomic and 16S rRNA analysis revealed the microbial diversity of lactic acid bacteria in traditional fermented foods of eastern Hainan, China. Food & Function 13:24 pages 12938-12952.

2. Aonan Xia, Yang Jiang, Baokun Li, Tong Wang, Jianxin Zhao, Xiaoming Liu, Wei Chen. (2022) Indigenous Chinese fermented dairy products: Microbial diversity, flavour, and health benefits. International Dairy Journal 135, pages 105479.

3. Sonam Lama, Jyoti Prakash Tamang. (2022) Isolation of Yeasts from Some Homemade Fermented Cow-Milk Products of Sikkim and Their Probiotic Characteristics. Fermentation 8:12 pages 664.

4. Yemisi D. Obafemi, Solomon U. Oranusi, Kolawole O. Ajanaku, Paul A. Akinduti, John Leech, Paul D. Cotter. (2022) African fermented foods: overview, emerging benefits, and novel approaches to microbiome profiling. npj Science of Food 6:1.

5. Cortney Leone, Harshavardhan Thippareddi, Cheikh Ndiaye, Ibrahima Niang, Younoussa Diallo, Manpreet Singh. (2022) Safety and Quality of Milk and Milk Products in Senegal—A Review. Foods 11:21, pages 3479.

6. Adeoye John Kayode, Anthony Ifeanyi Okoh, Massimiliano Galdiero. (2022) Assessment of multidrug-resistant Listeria monocytogenes in milk and milk product and One Health perspective. PLOS ONE 17:7, pages e0270993.