The incorporation of sourdough in sugar-reduced biscuits: a promising strategy to improve techno-functional and sensory properties

The demand for sugar-reduced, low-sugar, or even sugar-free food products is increasing. Sweet bakery products are the second main source of added sugar after sugary drinks. The reduction of sugar causes a loss of product quality, since sugar contributes to structure and flavour. The most common sugar replacers on the market are polyols, which act as sweet bulking agents. However, alternatives, which can be considered as 'clean-label' are in high demand. Sourdough technology was applied using the bi-functional lactic acid bacteria strain Leuconostoc citreum TR116. This strain is able to produce mannitol, which contributes to sweetness, and/or exopolysaccharides to compensate structure loss in sugar-reduced products. Besides the full-sugar biscuit (C1), biscuits reduced in sugar by 75% by wheat starch (C2) or by commercially available mannitol (C3) were considered as controls. Wheat starch as a sugar replacer created a lower biscuit firmness (- 10.7 N), while mannitol increased the hardness significantly (+ 12.9 N). Both sugar replacers caused less biscuit spreading and a poorer sensory profiles. The addition of sourdough (5% or 10%) in a sugar-reduced biscuit by wheat starch (C2) improved the viscoelastic properties, dough stickiness and dough hardness, as well as biscuit firmness. Furthermore, it contributed to colour (lowered the Delta E value) and increased sweetness and flavour intensity (+ 140%; + 139%). The predicted GI of C2-biscuits (73.5) were lower than C3-biscuits (80.8). Sourdough did not influence the release of reducing sugars during digestion. In conclusion, 10% sourdough incorporation represents a useful tool to overcome quality loss caused by the reduction of sugar by improving texture, taste and flavour.