Food Research International 27 (1994) 567-569 RESEARCH NOTE The influence of a baker’s yeast pre-inoculum on bread-dough leavening J. F. R. Lues,‘*, B. C. Viljuenb & E. J. Smit” “ Departments of Environmental and Paramedical Sciences, Faculty of Applied Sciences, Technikon OFS, Private Bag X20539, Bloemfontein 9300, South Africa ‘Department of Food Science. Faculty of Agriculture, University of the Orange Free State. PO Box 339. Bloemfontein 9300, South Africa In order to investigate the influence of a pre-inoculum on the fermentation per- formance of compressed baker’s yeast used for bread-dough leavening, pre-in- ocula were made by adding compressed baker’s yeast to a premix-sugar broth and cultivating it for 30, 60, 90 and 120 min. The pre-inocula were added sepa- rately to the dough and the gas production measured with the aid of a fer- mento-manometer. The pre-inoculum cultivated for 120 min presented the highest increase (43.6%) in maximum gas produced (P,,,) after 90 min of dough fermentation. The possibility of reducing lag time during dough fermen- tation, by using a cost-effective pre-inoculum, was assessed and results showed a significant (P 20.05) increase in gas production which could be highly benefi- cial to the bread industry. Keywords: Pre-inoculum, baker’s yeast, bread INTRODUCTION The number of yeasts cells originally added and their physiological state are important factors gov- erning the composition and performance of baker’s yeast in bread-dough (Seiler, 1975). At- tempting to optimise dough leavening, various au- thors proposed mixing compressed yeast with water to form a pre-inoculum, before adding the yeast to the dough. Recently however, this method has fallen into disfavour, as it is time con- suming and unnecessary, and adding compressed yeast directly to dough has no detrimental effect on fermentation (Daniel, 1972; Brown, 1975; Sul- tan, 1982; Trivedi & Jacobson, 1986). It is commonly accepted that the pre-proofing stage of the Choreleywood bread-baking process allows adequate spreading and ‘revival’ of yeasts *To whom correspondence should be addressed. Food Research International 0963-9969/94/$07.00 0 1994 Canadian Institute of Food Science and Technology (Matz, 1960; Clayton, 1973). However, during the production of compressed yeast, the yeast cells are harvested in the late stationary phase to ensure optimum cell density and activity (Sanderson, 1985). This practice, as well as the lowering of metabolic rates within the yeast cells during pro- longed low-temperature storage, is responsible for an unproductive lag phase at the beginning of dough-processing, when compressed yeast blocks are directly crumbled into the dough (Fance, 1966; Pyler, 1973; Sanderson, 1985). In this study we attempted to reduce the lag phase which exists during dough developing, by improving the inoculum with the aid of pre-inoc- ula consisting of pre-mix and sugar. MATERIALS AND METHODS Inoculum level Three replicates of pre-inocula were prepared by