GLUTEN-FREE BREAD: OPTIMIZATION OF FORMULATION AND PROCESS CONDITIONS

The aim of this PhD research project was to identify the formulations and to define the process conditions that most influence the quality and the shelf-life of gluten-free (GF) bread. Raw materials that are commonly used in GF bread production were first characterized, in particular as regards the rheological properties of different starchy gels during a short term ageing. Waxy rice flour (WRF) and rice bran (RB), at 25% and 50% substitution level, came out to be very effective in reducing gel stiffness and storage modulus (G’) of the mixtures containing corn starch (CS) or rice flour (RF). The effects of High Hydrostatic Pressure treatments on CS, RF and WRF were also investigated. A partial gelatinization of RF treated at 400MPa and 600MPa was evidenced by the viscoamylographic test and the formation of a more compact structure and a higher water retention capacity were registered for CS treated at 600MPa. The effect of Psyllium (Psy) and sugar beet (SB) fibers on dough and bread properties was also evaluated. The presence of 2.5% Psy generally determined an increase of dough height and CO2 production during leavening. Psy fiber also showed an anti-staling effect, higher than SB fiber. Taking into account all these results, a GF sourdough (SD) containing selected bacteria and yeasts (Lactobacillus sanfranciscensis and Candida humilis) was developed; then it was constantly refreshed and monitored in terms of number and type of microorganisms, capability to produce/retain CO2 and pH variations. When a stable microbial association was achieved, as well as constant SD properties, some breadmaking trials were performed. GF SD combined with compressed yeast resulted an excellent opportunity to improve GF bread quality and shelf-life.