The degree of protein aggregation in whey protein isolate-based dispersions modifies their surface and rheological properties

Este trabajo apunta a estudiar el efecto del grado de agregación de proteínas en las propiedades de superficie y reológicas de dispersiones de ASP con diferente concentración de proteína (80, 100 y 120 g/kg), pH (5,5 ó 6,5) o contenido de NaCl (1 ó 2 g/kg). Las dispersiones fueron tratadas térmicamente a 70, 75 y 80°C por diferentes tiempos. Mediante la mezcla de dispersiones de proteína agregada y nativa, se obtuvieron dispersiones con grados de agregación diferente. La tensión superficial de las dispersiones se determinó fue determinada por el método de la gota colgante, mientras que las propiedades reológicas se obtuvieron desde ensayos de curva de flujo. Se encontró un efecto menor del grado de agregación sobre la difusión, lo cual indica que las proteínas nativas dominaron la disminución de la tensión superficial. La reología de las dispersiones con adición de NaCl cambió desde un comportamiento Newtoniano a uno pseudoplástico para grados de agregación sobre el 20%; mientras que todas las dispersiones a pH 5,5 ó 6,5 presentaron un comportamiento pseudoplástico.This work aims to study the effect of degree of protein aggregation on the surface and rheological properties of whey protein isolate dispersions with different concentrations (80, 100 and 120 g/kg), pHs (5.5 or 6.5) or NaCl contents (1 or 2 g/kg). Dispersions were thermally treated at 70, 75 and 80°C for different times. By mixing aggregated with native protein dispersions, different degrees of aggregation (0%, 20%, 40%, 60% and 80%) were obtained. Surface tension of the dispersions was determined by the pendant drop method, whilst their rheological properties were obtained from flow curve tests. A slight effect of the degree of aggregation over diffusion was found, which indicates that native proteins dominated the decrease in surface tension. The rheological behavior of dispersions with NaCl addition changed from Newtonian to shear thinning for aggregation degrees above 20%, whilst all dispersions at pH 5.5 and 6.5 presented a shear thinning behavior

Impact of the Simulated Gastric Digestion Methodology on the In Vitro Intestinal Proteolysis and Lipolysis of Emulsion Gels

The aim of this work was to study the impact of the methodology of in vitro gastric digestion (i.e., in terms of motility exerted and presence of gastric emptying) and gel structure on the degree of intestinal proteolysis and lipolysis of emulsion gels stabilized by whey protein isolate. Emulsions were prepared at pH 4.0 and 7.0 using two homogenization pressures (500 and 1000 bar) and then the emulsions were gelled by heat treatment. These gels were characterized in terms of texture analysis, and then were subjected to one of the following gastric digestion methods: in vitro mechanical gastric system (IMGS) or in vitro gastric digestion in a stirred beaker (SBg). After gastric digestion, the samples were subjected to in vitro intestinal digestion in a stirred beaker (SBi). Hardness, cohesiveness, and chewiness were significantly higher in gels at pH 7.0. The degree of proteolysis was higher in samples digested by IMGS–SBi (7–21%) than SBg–SBi (3–5%), regardless of the gel’s pH. For SBg–SBi, the degree of proteolysis was not affected by pH, but when operating the IMGS, higher hydrolysis values were obtained for gels at pH 7.0 (15–21%) than pH 4.0 (7–13%). Additionally, the percentage of free fatty acids (%FFA) released was reduced by 47.9% in samples digested in the IMGS–SBi. For the methodology SBg–SBi, the %FFA was not affected by the pH, but in the IMGS, higher values were obtained for gels at pH 4.0 (28–30%) than pH 7.0 (15–19%). Our findings demonstrate the importance of choosing representative methods to simulate food digestion in the human gastrointestinal tract and their subsequent impact on nutrient bioaccessibility

Effect of Gelling Agent Type on the Physical Properties of Nanoemulsion-Based Gels

Senior populations may experience nutritional deficiencies due to physiological changes that occur during aging, such as swallowing disorders, where easy-to-swallow foods are required to increase comfort during food consumption. In this context, the design of nanoemulsion-based gels (NBGs) can be an alternative for satisfying the textural requirements of seniors. This article aimed to develop NBGs with different gelling agents, evaluating their physical properties. NBGs were prepared with a base nanoemulsion (d = 188 nm) and carrageenan (CA) or agar (AG) at two concentrations (0.5–1.5% w/w). The color, rheology, texture, water-holding capacity (WHC) and FT-IR spectra were determined. The results showed that the CA-based gels were more yellow than the AG ones, with the highest hydrocolloid concentration. All gels showed a non-Newtonian flow behavior, where the gels’ consistency and shear-thinning behavior increased with the hydrocolloid concentration. Furthermore, elastic behavior predominated over viscous behavior in all the gels, being more pronounced in those with AG. Similarly, all the gels presented low values of textural parameters, indicating an adequate texture for seniors. The FT-IR spectra revealed non-covalent interactions between nanoemulsions and hydrocolloids, independent of their type and concentration. Finally, the CA-based gels presented a higher WHC than the AG ones. Therefore, NBG physical properties can be modulated according to gelling agent type in order to design foods adapted for seniors

Comparative Study of Physicochemical Properties of Nanoemulsions Fabricated with Natural and Synthetic Surfactants

This work aims to evaluate the effect of two natural (whey protein isolate, WPI, and soy lecithin) and a synthetic (Tween 20) emulsifier on physicochemical properties and physical stability of food grade nanoemulsions. Emulsions stabilized by these three surfactants and different sunflower oil contents (30% and 50% w/w), as the dispersed phase, were fabricated at two levels of homogenization pressure (500 and 1000 bar). Nanoemulsions were characterized for droplet size distribution, Zeta-potential, rheological properties, and physical stability. Dynamic light scattering showed that droplet size distributions and D50 values were strongly affected by the surfactant used and the oil content. WPI gave similar droplet diameters to Tween 20 and soy lecithin gave the larger diameters. The rheology of emulsions presented a Newtonian behavior, except for WPI-stabilized emulsions at 50% of oil, presenting a shear-thinning behavior. The physical stability of the emulsions depended on the surfactant used, with increasing order of stability as follows: soy lecithin < Tween 20 < WPI. From our results, we conclude that WPI is an effective natural replacement of synthetic surfactant (Tween 20) for the fabrication of food-grade nanoemulsions

Plant-Based Oil-in-Water Food Emulsions: Exploring the Influence of Different Formulations on Their Physicochemical Properties

The global focus on incorporating natural ingredients into the diet for health improvement encompasses ω-3 polyunsaturated fatty acids (PUFAs) derived from plant sources, such as flaxseed oil. ω-3 PUFAs are susceptible to oxidation, but oil-in-water (O/W) emulsions can serve to protect PUFAs from this phenomenon. This study aimed to create O/W emulsions using flaxseed oil and either soy lecithin or Quillaja saponins, thickened with modified starch, while assessing their physical properties (oil droplet size, ζ-potential, and rheology) and physical stability. Emulsions with different oil concentrations (25% and 30% w/w) and oil-to-surfactant ratio (5:1 and 10:1) were fabricated using high-pressure homogenization (800 bar, five cycles). Moreover, emulsions were thickened with modified starch and their rheological properties were measured. The physical stability of all emulsions was assessed over a 7-day storage period using the TSI (Turbiscan Stability Index). Saponin-stabilized emulsions exhibited smaller droplet diameters (0.11–0.19 µm) compared to lecithin (0.40–1.30 µm), and an increase in surfactant concentration led to a reduction in droplet diameter. Both surfactants generated droplets with a high negative charge (−63 to −72 mV), but lecithin-stabilized emulsions showed greater negative charge, resulting in more intense electrostatic repulsion. Saponin-stabilized emulsions showed higher apparent viscosity (3.9–11.6 mPa·s) when compared to lecithin-stabilized ones (1.19–4.36 mPa·s). The addition of starch significantly increased the apparent viscosity of saponin-stabilized emulsions, rising from 11.6 mPa s to 2117 mPa s. Emulsions stabilized by saponin exhibited higher stability than those stabilized by lecithin. This study confirms that plant-based ingredients, particularly saponins and lecithin, effectively produce stable O/W emulsions with flaxseed oil, offering opportunities for creating natural ingredient-based food emulsions

Simulation of Human Small Intestinal Digestion of Starch Using an In Vitro System Based on a Dialysis Membrane Process

This work deepens our understanding of starch digestion and the consequent absorption of hydrolytic products generated in the human small intestine. Gelatinized starch dispersions were digested with -amylase in an in vitro intestinal digestion system (i-IDS) based on a dialysis membrane process. This study innovates with respect to the existing literature, because it considers the impact of simultaneous digestion and absorption processes occurring during the intestinal digestion of starchy foods and adopts phenomenological models that deal in a more realistic manner with the behavior found in the small intestine. Operating the i-IDS at di erent flow/dialysate flow ratios resulted in distinct generation and transfer curves of reducing sugars mass. This indicates that the operating conditions a ected the mass transfer by di usion and convection. However, the transfer process was also a ected by membrane fouling, a dynamic phenomenon that occurred in the i-IDS. The experimental results were extrapolated to the human small intestine, where the times reached to transfer the hydrolytic products ranged between 30 and 64 min, according to the flow ratio used. We consider that the i-IDS is a versatile system that can be used for assessing and/or comparing digestion and absorption behaviors of di erent starch-based food matrices as found in the human small intestine, but the formation and interpretation of membrane fouling requires further studies for a better understanding at physiological level. In addition, further studies with the i-IDS are required if food matrices based on fat, proteins or more complex carbohydrates are of interest for testing. Moreover, a next improvement step of the i-IDS must include the simulation of some physiological events (e.g., electrolytes addition, enzyme activities, bile, dilution and pH) occurring in the human small intestine, in order to improve the comparison with in vivo data.National Commission for Scientific and Technological Research (CONICYT Chile) through FONDECYT project 11140543, FONDECYT project 1191858, and project fund CONICYT-PIA Project AFB180004

Structural and Physicochemical Characterization of Extracted Proteins Fractions from Chickpea (<i>Cicer arietinum</i> L.) as a Potential Food Ingredient to Replace Ovalbumin in Foams and Emulsions

Chickpeas are the third most abundant legume crop worldwide, having a high protein content (14.9–24.6%) with interesting technological properties, thus representing a sustainable alternative to animal proteins. In this study, the surface and structural properties of total (TE) and sequential (ALB, GLO, and GLU) protein fractions isolated from defatted chickpea flour were evaluated and compared with an animal protein, ovalbumin (OVO). Differences in their physicochemical properties were evidenced when comparing TE with ALB, GLO, and GLU fractions. In addition, using a simple and low-cost extraction method it was obtained a high protein yield (82 ± 4%) with a significant content of essential and hydrophobic amino acids. Chickpea proteins presented improved interfacial and surface behavior compared to OVO, where GLO showed the most significant effects, correlated with its secondary structure and associated with its flexibility and higher surface hydrophobicity. Therefore, chickpea proteins have improved surface properties compared to OVO, evidencing their potential use as foam and/or emulsion stabilizers in food formulations for the replacement of animal proteins

Time-Dependent Rheological Behavior of Starch-Based Thickeners and Herb Infusion Dispersions for Dysphagia Management

© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim The causes of dysphagia include neurological conditions and cancer. Swallowing impairment of liquids represents a risk of aspiration, pneumonia, dehydration, and nutritional deficiencies. Commercial thickeners often based on modified cornstarch address this issue. The herb Matico (Buddleja globosa Hope) is used as a wound-healing adjuvant treatment for oral mucositis caused by cancer therapies. This study analyzes the flow behavior of Matico infusion with two thickeners, Thick & Easy TM , and Enterex® Food Thickener at three concentrations. A rheological assessment is performed (20 ± 1 °C subsequent intervals: 1–100 s −1 , constant shear step at 100 s −1 , and 100–1 s −1 , each one with a 120 s span) at five time points (0–60 min). Rheological behavior is adjusted to the Herschel–Bulkley model. Significant differences (p &lt; 0.05) are obtained for yield stress (σ 0 ), consistency coefficient (K), and flow behavior index (n) between time-