Bread making is a practice that has long been discovered and has been the subject of much progress. In more recent years, developments in bread making have been increasingly focused on the enhancement and diversification of the sensory pleasures of taste, texture, and appearance of the final product
[19]. The degradation of the dough carbohydrates (namely fructose, glucose, sucrose and maltose) present in the flour, or even wittingly added, is carried out by yeasts, resulting in the release of carbon dioxide and ethanol, produced through glycolysis and posterior pyruvate decarboxylation and reduction
[17][19][30]. Carbon dioxide is responsible for the dough leavening, while most of the ethanol evaporates during the baking process. However, the latter also plays an important role in the properties of the dough
[17]. The choice of the appropriate yeast is usually based on (i) good fermentative power which could be translated into its ability to leaven the dough; (ii) capacity to use different carbon sources; and (iii) tolerance to stressful conditions, namely, osmotic, and freezing stresses
[30][47][48].
S. cerevisiae strains have been domesticated and optimized for baking applications and are usually the manufacturer’s required yeast for the baking industry. This species efficiently uses maltose as a source of energy, as opposed to
Candida humilis and
Kazachstania exigua which, according to de Vuyst et al.
[17], are sourdough-specific maltose-negative yeasts.
S. cerevisiae is commonly implemented as a leavening agent, becoming an alternative to sourdough (extensively used for years) particularly in rapid and industrial-scale bread productions
[17]. However,
T. delbrueckii is being pointed out as an alternative to
S. cerevisiae in this industry, mainly due to its high osmotic and freeze-thawing resistance, showing improvement of the quality of the bakery products
[29][30]. Experiments conducted by Almeida and Pais
[29] demonstrated greater leavening activity in lean and frozen dough for
T. delbrueckii strains, comparing to
S. cerevisiae, as the traditional yeast was more prone to suffer from freeze damage during the storage of the doughs. Apart from this feature,
T. delbrueckii strains displayed rapid growth, a more rapid response when exposed to hyperosmotic conditions, and high biomass production accompanied with sweet properties (associated with the release of aromatic compounds). These observations were later confirmed by Hernandez-Lopez, Prieto and Randez-Gil
[49]. Due to its osmotolerant properties,
T. delbrueckii has already been used in the bakery industry in Japan, for the production of sweet breads and pastries
[50].
Co-cultures using
S. cerevisiae and
T. delbrueckii species enhanced bread quality with superior aroma and improved sensorial attributes, with 47 volatile compounds—predominately alcohols, aldehydes, and esters—being identified in the bread crumb leavened with both yeasts
[19]. Wahyono et al.
[19] highlighted some properties of the resulting mixed bread which, using a radar plot, rated within a range of 4.73–5.57 from a total of 7 points, such as acceptability, enhanced flavor, mouthfeel, and color, in comparison with
S. cerevisiae single cultures, which recorded within 4.07–5.71 range in the same radar plot.