Fermentation of kivuguto, a rwandese traditional milk : selection of microbes for a starter culture

Abstract EN

A total of 390 bacterial strains were isolated from four kivuguto samples.

Isolates were screened by phenotypic methods and molecular techniques using the PCR and sequencing of 16S rDNA and/or 16S-23S rDNA intergenic transcribed spacer (ITS) region.

The rate of milk acidification and ability to grow under extreme environmental conditions were also examined for pre-selected isolates.

Fermentation assays with mixed strains were performed to identify microbial formulations that produced milk similar to kivuguto.

Such formulated milk was stored at 4°C on 24 days for shelf-life analysis to detect any organoleptic defect.

Bacteria identified in kivuguto included Lactococcus lactis (strains CWB-B1466 and CWBI-B1469) and Leuconostoc mesenteroides subsp.

mesenteroides (strains CWBI-B1467 and CWBI-B1465) and Leuconostoc pseudomesenteroides (T) (NRIC177) (strains CWBI-B1468, CWBI-B1470 and CWBI-B1471).

One Leuconostoc sp.

grew at low pH 2.5, in high sodium chloride concentration (up to 6.5%) and was resistant to heat (55°C).

Fermentation experiments showed that kivuguto coagulates in 8 hours at 30°C.

Three milk formulations produced using mixed strains gave good results.

The best-tasting and longest shelf-life (35 days) kivuguto was produced by a mixture of two Leuconostoc spp.

and Lactococcus lactis.

These strains give kivuguto its characteristic properties.