Baking using baker's yeast immobilized in a starch-gluten-milk matrix (traditional fermented cereal food trahanas), containing viable lactic acid bacteria (LAB), and kefir (natural co-culture of yeasts and LAB) immobilized on orange peel, were investigated. The use of immobilized cells increased shelf life, delayed staling, and improved overall the quality of bread, compared with the traditional baker's yeast bread. These improvements were attributed to the reduction of pH, the lower moisture loss rates, and the presence of LAB, which are known to exhibit antimould properties. Better results were obtained using the sourdough method compared to the straight dough bread-making method. Headspace SPME GCMS analysis showed that the use of immobilized cells increased the number of bread aroma volatiles, especially esters. The best results, including shelf life and overall bread quality, were obtained in the case of baker's yeast immobilized on trahanas, although kefir immobilized on orange peel seems to be a more cost effective biocatalyst. (c) 2007 Elsevier Ltd. All rights reserved.