Impact of acidification and protein fortification on thermal properties of rice, potato and tapioca starches and rheological behaviour of their gels

Abstract

The impact of acidification and non-gluten protein fortification (egg-albumin and soy-protein isolate) on thermal transitions of rice, potato and tapioca starches as well as the viscoelastic properties of their gels prepared at two casting temperatures, 90ºC and 120ºC, was investigated. The thermal and rheological behaviour of starches depended on their botanical origin and were significantly influenced by the presence and type of protein added as well as by the pH of the aqueous dispersion. Acidification to pH 4.5 increased the gelatinization temperature of rice starch in the presence of albumin or soy proteins, while reduced it in the case of tapioca starch, regardless of the presence of proteins. Acidification of rice starch dispersions decreased significantly the apparent gelatinization enthalpy; this effect was even greater in the presence of proteins. The addition of proteins brought about a structuring effect on tapioca gels leading to higher viscoelastic moduli and lower tan δ values. In general, acidification led to weaker gel structures, with more pronounced effect for potato starch, most likely related to its higher phosphate content (charge screening). Much weaker gels were obtained at 120ºC compared to those processed at lower temperatures; however, protein incorporation reinforced gel structure, an effect that was not observed in gels formed at 90º, as also revealed by microstructure analysis using confocal scanning laser microscopy. In conclusion, protein addition and pH adjustments of aqueous starch dispersions can provide an effective means to modulate the functional and textural properties of gel-like starch-based gluten-free formulations.

Textural, Pasting, and Rheological Behavior of Starch‐Pectin‐Sucrose Gels: Relation with Sensory Perception

“…Tan δ relates to the viscous and the elastic behavior (tan δ G″/G′) and provides information on the balance of the viscoelastic modulus of a material . The tan δ range of 0.115–0.173, indicating a weak viscoelastic gel character and a stable structure . This is in accordance with results reported by Galkowska et al, who obtained gels with sucrose, pectin, and starch with weak viscoelastic character, and Cruz using starch suspensions.…”

“…The gels were placed in the measuring system and the upper plate was placed in position (1 mm gap). The sample excess was removed and rested for 10 min to allow for sample relaxation . The oscillatory assays were carried out: (1) strain sweep (0.01–100%, 1 Hz, 25 °C), in order to determine LVR; (2) frequency sweeps into LVR (strain: 0.2%), frequency range 0.1–10.0 Hz and 25 °C; and (3) temperature ramp from 25 to 80 °C, heating rate 5 °C min −1 , 1 Hz, strain: 0.2%.…”

Microwave radiation and protein addition modulate hydration, pasting and gel rheological characteristics of rice and potato starches

“…The homogenous distribution of radiation on the sample is of crucial importance. So, the container was stirred constantly to ensure a uniform energy and temperature distribution during treatment as described in Villanueva et al (2018b). MW radiation frequency was 2450 MHz and the power, 900W.…”

“…This indicated that starch sample structures had different resistances to stress-induced rupture. According to Villanueva et al (2018b), potato gels preserved their structure beyond rice starch gels, meaning that potato gels had good mechanical resistance and hardness. Adding proteins to rice starch gels reduced their resistance to breakage and led to values of τmax 36% and 49% lower than those of protein-free gels for CA and SPI, respectively.…”

“…The addition of protein is a viable alternative to improve the nutritional properties of these products. Proteins are also known to modify structure and texture in foods (Villanueva et al, 2018b). Soy proteins isolate (SPI) and calcium caseinate (CA) have been investigated in GF applications because of their effect on nutrition and structure of products (Krupa-Kozak et al, 2011;Ronda et al, 2014).…”