**4.2.2 Ergo – Naturally fermented milk**

*Ergo* is made by natural fermentation of milk under ambient temperature, without the addition of starter cultures (Assefa *et al.*, 2008). The use of a portion of ergo from a previous batch as a starter in highland areas where ambient temperature is relatively low is reported (Kassa, 2008). This practice is technically adapted to overcome the effect of low ambient temperature, which slows down the growth of lactic acid bacteria (LAB) in the absence of starter culture thus prolongs the fermentation time. The temperature and duration of incubation varies from place to place depending on the prevailing environmental conditions. According to a previous report, five LAB genera were identified from *Ergo* that include *Lactobacillus*, *Lactococcus*, *Leuconostoc*, *Entrococcus* and *Streptococcus* (Assefa *et al.*, 2008). They also indicated the LAB species identified in *Ergo* to be *Streptococcus thermophilus*, *Strep. acidominus*, *Enterococcus faecalis* var. *liquefaciens*, *Strep. bovis*, *Strep. mitis*, *Strep. agalactiae*, *Lactococcus cremoris*, *Leuconostoc dextranicum*, *Leuc. lactis*, *Lactobacillus xylosus* and

Microbial Properties of Ethiopian Marketed Milk and Milk Products and

churned using different techniques until butter granules are formed.

**4.2.3 Kibe – Traditional butter** 

considered.

stages in the milk chain.

**4.2.4 Arera – Defatted sour milk** 

Associated Critical Points of Contamination: An Epidemiological Perspective 311

Different studies on various aspects of traditional butter-making in Ethiopia have been undertaken in different parts of the country. Traditional butter-making is based on sour milk that has been accumulated over a few days commonly in a clay pot. Once the amount of the accumulated sour milk justifies churning, the sour milk is mixed thoroughly by using a wooden stick with 3 to 5 finger-like projections at one end (*mesbekia* in amahric) then

Mean total bacterial counts ranged from 6.18 cfu/g in butter samples collected from Selale area to 7.25 cfu/g in samples from Sululta. These values are higher than the acceptable limit of 5×104 cfu/g (Mostert and Jooste, 2002). Average *Enterobacteriaceae* and coliform counts were greater than 4 cfu/g of butter sampled from all study sites both of which are higher than the acceptable value of <10 cfu/g (Mostert and Jooste, 2002). Mean yeast and mould counts observed in the current study exceeded 8 cfu/g of butter sampled from all the sites

TBC of 3.15 × 107 and the presence of high variability among samples depending on the sources were reported (Mamo, 2007). Samples collected from open markets and rural producers, for instance, had higher counts as compared to that obtained from dairy farms and urban producers. Coliform counts ranging from 1.92 to 4.5 log cfu/gm of butter are reported (Mamo, 2007; Asfaw, 2008; Yilma *et al*., 2007a). These differences could be attributed to the wide variation in hygienic handling during milking, processing, storage and transport to market. *Klebsiella pneumoniae*, *Klebsiella oxytoca*, *Enterobacter cloacae*, *Citrobacter freundii*, and *Esherichia coli* were isolated from *ergo* samples collected in the central Ethiopia (Yilma *et al.*, 2007ab), and these microbes are considered to be pathogenic and spoilage (Walstra *et al.,* 2006). On the other hand, yeast and mould counts ranging between 4.3 and 6.86 log cfu/g of butter sampled from Wollayta area are reported (Asfaw, 2008). Average yeast and mould count of 4.5 × 107 cfu/g of butter was also reported (Mamo, 2007). Higher values are observed (Yilma *et al.,* 2005) that varied depending on the type of producer where lower counts were observed for butter sampled from research centers and small-scale producers than that from large-scale producers. TBC of fresh butter sampled from rural and public butter markets in Addis Ababa ranged from 6.2 x 104 to 1.86 x 108 per gram of butter and coliforms were found in all samples that indicate poor hygienic practices (ILCA, 1992). These high deviations from the acceptable value of 10 cfu/gm (Mostert and Jooste, 2002) indicate substandard handling conditions at all

Average counts of total bacteria, *Enterobacteriaceae* and coliforms were greater than 9, 4.7 and 4.2 cfu/ml, respectively of *Arera* sampled from all study sites both of which are higher than the acceptable value of <10 cfu/gm (Mostert and Jooste, 2002). Traditionally produced *Arera* sampled from Wollayta area had total bacterial count of about 9 log cfu/ml (Nebiyu, 2008). The same author also reported coliform count of 4.86 log cfu/ml. Different species of bacteria were identified in *Arera* samples collected during both dry and wet seasons, which include: *Klebsiella pneumoniae, Klebsiella oxytoca, Enterobacter cloacae, Enterobacter sakazakii,* 

*Esherichia coli* and some species of *Salmonella* (Yilma *et al.*, 2007a).

*Lact. lactis*. The isolation of similar genera, and *Micrococci* and coliforms, which are present in low numbers was also reported (Gonfa *et al.,* 2001). An average LAB count of 7.68 log cfu/ml for *Ergo* samples collected from different producers in Addis Ababa and major cities around Addis Ababa was also reported (Yilma and Faye, 2006).

LAB are reported to have antimicrobial activities. The use of different LAB species to create a stationary phase for *Staphylococcus aureus* and a higher density of LAB in modeled starter culture could result in complete inhibition of the bacterium (Le Marc *et al,* (2009). Another report also indicated that 12 LAB isolates from *Ergo* that include *Lactobacillus plantarum*, *Lactococcus lactic* ssp *cremoris*, *Lactococcus lactic* ssp *lactic*, *Lactobacillus acidophyilus*, *Leuconostoc lactic*, *Pediococcus pentosace* and *Pediococcus* sp. have antimicrobial activities against different pathogenic microbes including *Shigella flexinery*, *Salmonella typhi*, *Escherichia coli* and *Staphylococcus aureus (*Assefa *et al*., 2008).

TBC of *Ergo* was generally high ranging from 7.71 cfu/ml in samples collected from Sheno to about 10 cfu/ml in samples from Jimma. Average *Enterobacteriaceae* and coliform counts were greater than 4 cfu/ml of *Ergo* sampled from all study sites with differences between the lowest and highest counts ranging from 0.25 to 0.37 cfu/ml.

Mean yeast and mould counts observed in the current study exceeded 8 cfu/ml of *Ergo* sampled from all the sites considered. However, a lower value (2×105 cfu/ml) was reported (Gonfa *et al.,* 2001). Yeast and mould count of up to 4.6 log cfu/ml of fermented milk sampled from Southern Ethiopia was also reported (Beyene, 1994). These values are much higher than the acceptable value (<10 cfu/gm for yoghurt) (Mostert and Jooste, 2002). The presence of different species of yeast in milk and its products may result in the spoilage of the product or conversely could contribute to the enhancement of the flavor of fermented milk, since different yeast species are able to assimilate different milk substrates (Gadaga *et al.*, 2000). Bacterial species namely *Klebsiella pneumoniae*, *Klebsiella oxytoca*, *Enterobacter cloacae*, *Citrobacter freundii* and *Enterobacter sakazakii* were isolated from *Ergo* samples collected from smallholder producers in the central Ethiopia (Yilma *et al*., 2007a). Coliform count averaging at 6.57 log cfu/ml was reported for *Ergo* samples (Yilma and Faye, 2006). Lower values were also observed in which 75% of the samples showed coliform count less than 4.4 log cfu/ml (Beyene, 1994). However, the same author also reported TBC of greater than 8.6 log cfu/ml for 3/4th of fermented milk samples collected from three villages in Southern Ethiopia and coliform counts of higher than 4.4 log cfu/ml in 15% of two fermented milk varieties.

The common traditional milk processing techniques involve smoking of processing utensils using embers of *Olea africana*. This smoking practice is reported to be beneficial to keep better quality of *Ergo* through its inhibitory effect on spoilage and pathogenic organisms. For instance, the inhibitory effect of smoking on *Listeria monocytogenes* was reported (Ashenafi, 1994). The effect of lower pH of *Ergo* in controlling the proliferation of undesirable microorganisms is more effective after 24 hours of incubation. However, at this time, the *ergo* is considered to be too sour for direct consumption since *ergo* coagulates within 24 hours and preferably consumed at this time for its good flavor (Ashenafi, 2006). Accordingly, the same author recommended that milk should be boiled beforehand and a small amount of 3-days-old *Ergo* that is normally free from pathogens but contains enough LAB should be inoculated to initiate fermentation.
