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The main objective of this work is to study the effect of polyphenols, from the brown seaweed Ascophyllum nodosum, on the structure and digestion behaviour of gels at two corn starch concentrations (1.95 and 5.00% w/w) as well as the structure, color and texture features of crumbs from gluten-free breads. Adsorption isotherms of polyphenols on native and gelled starches were carried out and modelled by means of Langmuir and Henry models, respectively. The formation and characteristics of tested gels were rheologically monitored by means of heating ramp, time sweep at high temperature, cooling ramp and frequency sweep at 25 °C. Elastic modulus values decreased with the presence of polyphenols. Additionally, the polyphenols significantly decreased the digestion rate, measured by both chemical and rheological procedures, and the final concentration of digested starch. Finally, the presence of polyphenols in breads increased the hardness and chewiness values and decreased the cohesiveness and resilience values as well as the crumb hardening during storage.

The aim of this work was to formulate a gluten-free focaccia flat bread based on rice and corn flour fortified with dry-fractionated pea protein concentrate (55 g/100 g protein content). A simplex-centroid mixture design with ten formulations helped to study how the flour ratios influenced the physical and sensory properties of dough and breads. The special cubic model significantly described all the responses determined in the dough and flour mixes, and most of those determined in the focaccia. The pea protein concentrate influenced the pasting properties of the flour mixes resulting in a decrease of viscosity. The midpoint of the experimental domain (focaccia containing 5 g/100 g of pea protein concentrate and 20 g/100 g of rice flour and corn flour each) was optimal, being not affected by the discolorations typical of pea (a* = 11.97, b* = 31.86, corresponding to an orange hue), having crumb hardness and chewiness of 9.11 N and 4.83 N, respectively, and moderate legume odor and flavor (5.6 and 5.3 c.u. in a 0–9 scale, respectively). The selected formulation could be labelled as “source of protein” (energy value provided by proteins >12%), “source of fiber” (fiber >3 g/100 g), and “low-fat” (fat <3 g/100 g).

Hydrocolloids are extensively used for food processing because their techno functional properties (emulsifier, stabilizer, and structural agent). But there is increasing interest in their role connected with nutritional improvements, particularly related to starch hydrolysis rates, which might involve the viscosity resulting from starch-hydrocolloid interaction. The objective of this research was to investigate the impact of gels viscosity on the enzymatic hydrolysis of a range of starch gels made with different starches and hydrocolloids. Heterogeneous systems (starch-hydrocolloid) were prepared with several starches (corn, wheat, rice, potato, cassava, pea) and hydrocolloids (locust bean gum, guar gum, xanthan gum, hydroxypropylmethylcellulose K4M, psyllium) at different concentrations (0%–0.5% - 2.5%). The starch-hydrocolloid pasting behavior and their susceptibility to amylase hydrolysis was recorded with the Rapid Viscoanalyzer following a rapid method (Santamaria, Montes, Garzon, Moreira, & Rosell, 2022a). The viscosity decay due to alpha-amylase activity was modeled to obtain starch gels hydrolysis rate (k). A negative correlation was found among kinetic constant (k) and viscosity at 37 °C (r = −0.55), setback (r = −0.50), and area under the pasting curve (r = −0.42). For instance, xanthan gum and psyllium addition showed strong negative correlation between kinetic constant and viscosity at 37 °C (r = −0.75) and setback (r = −0.79), respectively, particularly when blended with potato starch. These correlations indicate that pasting properties of the starch-hydrocolloid systems might be predictors of the enzymatic digestion rate of the gels, allowing the design of foods with controlled postprandial glucose response.

Corn starch gels (1:4 w:w) were made with the addition (up to 2% w/w starch basis) of sodium alginates of different average molecular sizes and nature. Rheology of the starchy gels were characterized to evaluate their viscoelasticity. Gels were subjected to in vitro digestion to estimate the effect of alginates addition on glycemic response. Tested alginates significantly decreased the value of the elastic modulus of gels. The coordination number obtained from complex modulus indicated that in general, less compact structures were obtained in the presence of alginates. These results were confirmed by scanning electron micrographs, where significant differences in the structure of alginate-corn starch gels were observed, but molecular size of alginates was not critical. Hydrolysis rate decreased with the presence of alginates in corn starch gels by interactions of alginates with leached amylose. At high alginate content, slower hydrolysis rates were determined when the most hygroscopic alginates were added.