African Journal of Biotechnology Vol. 6 (18), pp. 2122-2129, 19 September 2007   

ISSN 1684–5315 © 2007 Academic Journals        

Full Length Research Paper

Microflora distribution and species ratio of Tunisian fermented doughs for bakery industry

Sana M’hir, Mondher Mejri and Moktar Hamdi*

Laboratoire d’Écologie et de Technologie Microbienne, Institut National des Sciences. Appliquées et de Technologie (INSAT), Boulevard de la Terre, Centre Urbain Nord de Tunis, BP 676, 1080 Tunis. Tunisia.

*Corresponding author. E-mail: moktar.hamdi@insat.rnu.tn. Fax: 00 216 71 704 329.

Accepted 10 April, 2007

Thirty samples of fermented wheat dough microflora, collected from different Tunisian bakeries, were characterised. Forty per cent of the samples contained approximately 10⁶ cfu/g of mesophilic aerobic bacteria (MAB). Lactic acid bacteria (LAB) and yeasts dominated the microflora of these samples. They varied from 10⁵ to 10⁸ cfu/g. The LAB/yeasts ratio arising from microbial counts were varied between 1/1 and 200/1. More than 50% of the analysed samples were deprived of Enterococcus. The content of contaminating microflora like coliforms and mesophilic Bacillus ranged from 10² to 10⁴ cfu/g. The ratio between LAB and coliforms were estimated to about 10³/l for 26% of the analysed samples. This ratio is more important between LAB and mesophilic Bacillus. The LAB/mesophilic Bacillus ratio was about 10⁴ for 45% of the analysed samples. However, Micrococcaceae were absent in all samples. This study could be used with further information to establish the cooperative effect existing between LAB and yeasts during food fermentation and to point out an eventual antagonism effect between LAB and spoilage microflora  during bakery processing as showed for other fermented foods. The coliforms-like contaminating microflora serves as indicator on the hygienic quality of Tunisian bakery industry.

Key words: Fermented dough microflora, species ratio, lactic acid bacteria, yeasts, antagonism, bakery industry, bread quality, hygiene practices.