ASSESSMENT OF NUNU PRODUCED USING PURE STARTER CULTURE. A RESEARCH PROJECT MATERIAL ON BIOCHEMISTRY
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.
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.