Improving the baking aptitude of corn starch and rice flour by using high hydrostatic pressure treatments

High hydrostatic pressure (HHP) treatments are generally used to increase food shelf-life by inactivating microorganisms and enzymes without using high temperatures. This study represents an attempt to apply HHP as a non-conventional treatment to modify the technological properties of corn starch (CS) and rice flour (RF). These two raw materials, in fact, are the most common ingredients used in gluten-free (GF) bread production, largely responsible for the final product quality decay due to starch retrogradation. Each raw material was mixed with water and then treated at 600MPa for 5min at 40°C, below the gelatinization temperature of the samples at atmospheric pressure. Different pasting behaviours and solvent retention capacities of the treated (t) materials, with respect to the raw ones, were evidenced. In particular, both CSt and RFt showed a higher retention capacity in carbonate and lactic acid solvents, related to starch and protein properties, respectively. The different materials were properly combined (CS-RF; CSt-RF; CS-RFt; CSt-RFt), and each mixture was then used as the basic ingredient of a GF bread recipe. The properties of the resulting doughs were investigated both during mixing and leavening. The corresponding GF breads were evaluated for specific volume, crust and crumb color, moisture and aw. Bread crumb hardness (force at 25% of deformation) was determined, both on fresh and stored (20°C, 72h; paper bags) samples: fresh breads had similar crumb hardness (0.25-0.32N), but significant differences (p<0.05) came out after 3 days of storage: CS-RF, 3.06±0.52N; CSt-RFt, 2.37±0.52N; CSt-RF, 1.58±0.32N; CS-RFt, 1.58±0.36N. Therefore, the presence of CSt and/or RFt flours decreased the staling rate of GF breads, after 72h of storage, suggesting that the HHP treatment may be successfully used to improve GF bread shelf-life.