Influence of Arabinan Fine Structure, Galacturonan Backbone Length, and Degree of Esterification on the Emulsifying Properties of Acid-Extracted Sugar Beet Pectins.

Sugar beet pectins (SBPs) are known for their emulsifying properties, but it is yet unknown which structural elements are most important for functionality. Recent results indicated that the arabinose content has a decisive influence, but the approach applied did not allow causality to be established. In this study, a mostly intact SBP was selectively modified and the obtained pectins were analyzed for their molecular structure and their emulsifying properties. De-esterification only resulted in a moderate increase in droplet size. The length of the pectin backbone only influenced the emulsifying properties when the homogalacturonan backbone was cleaved to a higher extent. By using different arabinan-modifying enzymes, it was demonstrated that both higher portions and chain lengths of arabinans positively influence the emulsifying properties of SBPs. Therefore, we were able to refine the structure-function relationships for acid-extracted SBPs, which can be used to optimize extraction conditions.

Effect of Conformation of Sugar Beet Pectin on the Interfacial and Emulsifying Properties.

The influence of the conformation of sugar beet pectin (SBP) on the interfacial and emulsifying properties was investigated. The colloidal properties of SBP, such as zeta potential and hydrodynamic diameter, were characterized at different pH levels. Furthermore, pendant drop tensiometry and quartz crystal microgravimetry were used to study adsorption behavior (adsorbed mass and adsorption rate) and stabilizing mechanism (layer thickness and interfacial tension). A more compact conformation resulted in a faster reduction of interfacial tension, higher adsorbed mass, and a thicker adsorption layer. In addition, emulsions were prepared at varying conditions (pH 3-5) and formulations (1-30 wt% MCT oil, 0.1-2 wt% SBP), and their droplet size distributions were measured. The smallest oil droplets could be stabilized at pH 3. However, significantly more pectin was required at pH 3 compared to pH 4 or 5 to sufficiently stabilize the oil droplets. Both phenomena were attributed to the more compact conformation of SBP at pH < pKa: On the one hand, pectins adsorbed faster and in greater quantity, forming a thicker interfacial layer. On the other hand, they covered less interfacial area per SBP molecule. Therefore, the SBP concentration must be chosen appropriately depending on the conformation.

Extrusion Processing of Rapeseed Press Cake-Starch Blends: Effect of Starch Type and Treatment Temperature on Protein, Fiber and Starch Solubility.

For the valorization of oilseed press cakes into food products, extrusion can be used. A common way of applying the protein- and fiber-rich press cakes in directly expanded products is the combination thereof with starch, since starch gives a favourable texture, which correlates directly to expansion. To control product properties like expansion of protein and fiber-rich extruded products, the underlying physicochemical changes of proteins, fibers and starch due to thermomechanical input need to be comprehensively described. In this study, rapeseed press cake (RPC) was extruded and treated under defined thermomechanical conditions in a closed-cavity rheometer, pure and in combination with four starches. The impact of starch type (potato PS, waxy potato WPS, maize MS, high-amylose maize HAMS) and temperature (20/25, 80, 100, 120, 140 °C) on protein solubility, starch gelatinization (Dgel), starch hydrolysis (SH) and fiber solubility of the blends was evaluated. The extrusion process conditions were significantly affected by the starch type. In the extruded blends, the starch type had a significant impact on the protein solubility which decreased with increasing barrel temperature. Increasing barrel temperatures significantly increased the amount of soluble fiber fractions in the blends. At defined thermomechanical conditions, the starch type showed no significant impact on the protein solubility of the blends. Therefore, the observed effects of starch type on the protein solubility of extruded blends could be attributed to the indistinct process conditions due to differences in the rheological properties of the starches rather than to molecular interactions of the starches with the rapeseed proteins in the blends.

Impact of Rapeseed Press Cake on the Rheological Properties and Expansion Dynamics of Extruded Maize Starch.

Rapeseed press cake (RPC), an oil pressing side product rich in protein and fiber, can be combined with starch and valorized into directly expanded products using extrusion technology. The mechanism of starch expansion has been studied in detail, but the impact of RPC on expansion behavior is poorly understood. However, it can be linked to rheological and physicochemical properties and is a key product quality parameter. Blends with different amounts of RPC (0, 10, 40 g/100 g) were extruded at different barrel temperatures (100, 120, 140 °C) and moisture contents (24 or 29 g/100 g). The initial, intermediate and final sectional, longitudinal and volumetric expansion indices (SEI, LEI, VEI) were monitored directly, 10 s and 24 h after die exit to measure extrudate growth and shrinkage. The viscous and elastic properties of the extruded blends were investigated in a closed cavity rheometer. Starch and blends with 10 g/100 g RPC achieved a high initial SEI followed by significant short-term shrinkage. Blends containing 40 g/100 g RPC did not show any initial expansion. With increasing RPC content, the intermediate SEI decreased, but all samples reached a similar final SEI due to time-dependent swelling of the RPC blends. With increasing RPC content, the elasticity of the starch-based extruded samples significantly increased. Our study shows that comprehensive control and understanding of expansion mechanisms can be achieved only by investigating all stages of extrudate growth and shrinkage. We also found that the closed cavity rheometer is a powerful tool to correlate the rheological properties and expansion mechanisms of biopolymers.

Linking Expansion Behaviour of Extruded Potato Starch/Rapeseed Press Cake Blends to Rheological and Technofunctional Properties.

In order to valorise food by-products into healthy and sustainable products, extrusion technology can be used. Thereby, a high expansion rate is often a targeted product property. Rapeseed press cake (RPC) is a protein- and fibre-rich side product of oil pressing. Although there is detailed knowledge about the expansion mechanism of starch, only a few studies describe the influence of press cake addition on the expansion and the physical quality of the extruded products. This study assessed the effect of RPC inclusion on the physical and technofunctional properties of starch-containing directly expanded products. The effect of starch type (native and waxy), RPC level (10, 40, 70 g/100 g), extrusion moisture content (24, 29 g/100 g) and barrel temperature (20-140 °C) on expansion, hardness, water absorption, and solubility of the extrudates and extruder response was evaluated. At temperatures above 120 °C, 70 g/100 g of RPC increased the sectional and volumetric expansion of extrudates, irrespective of starch type. Since expansion correlates with the rheological properties of the melt, RPC and RPC/starch blends were investigated pre- and postextrusion in a closed cavity rheometer at extrusion-like conditions. It was shown that with increasing RPC level the complex viscosity |ƞ*| of extruded starch/RPC blends increased, which could be linked to expansion behaviour.

Properties of ß-Lactoglobulin Aggregates and Gels as Affected by Ternary Emulsifier Mixtures of Tween 20, Lecithin, and Sucrose Palmitate.

The influence of sucrose palmitate, Tween 20, and lecithin on the properties of heat-induced aggregates and cold-set gels of ß-lactoglobulin was studied based on an experimental mixture design with a fixed total emulsifier concentration. Emulsifiers were added to the protein solution before heating. Aggregate size and absolute values of ζ potential increased with the addition of emulsifiers, among which lecithin had the most pronounced effect. The water retention of the aggregates correlated positively with the aggregate size. Gels had reduced fracture stress and strains with increasing sucrose palmitate and decreasing Tween 20 contents. The fracture properties correlated with the ζ potentials of the aggregates, and larger aggregates led to gels with higher water-holding capacities. The emulsifiers hence influenced the gel properties indirectly via the aggregate properties. The impact of emulsifiers on food structures should therefore be considered when a food product is designed.

Collagen peptide-loaded W1/O single emulsions and W1/O/W2 double emulsions: influence of collagen peptide and salt concentration, dispersed phase fraction and type of hydrophilic emulsifier on droplet stability and encapsulation efficiency.

Bioactive peptides hold great promise as functional ingredients, but they are susceptible to hydrolysis (e.g., protease degradation) during digestion and under different physiological conditions in the human body. Thus, bioactive peptides must be encapsulated first to preserve their innate characteristics and to ensure delivery to an absorption site at the small intestine without biodegradation. The objective of this study was to formulate stable single emulsions of water in oil (W1/O) and double emulsions of water in oil in water (W1/O/W2) containing collagen peptide as core material. In this study, the influence of the following parameters was investigated: collagen peptide concentration (0-20%), salt (0% or 1% NaCl), hydrophilic emulsifiers for the outer water phase (Tween 80, lecithin, chitosan, pectin), and the use of different inner/outer water fractions (20-50% inner water, 50-80% outer water) on the droplet stability of the W1/O and W1/O/W2 emulsions during storage. In particular, the influence of the osmolytes was investigated to evaluate the change in osmotic balance and destabilization of the W1/O/W2 emulsion system as the encapsulated peptide was also osmotically active. Tween 80-stabilized W1/O/W2 emulsions showed the best droplet stability without phase separation (d90,3 = 36.6 µm) and the highest collagen peptide retention (encapsulation efficiency > 90%). During prolonged storage, collagen peptides were released from the W1/O/W2 emulsion system without significant droplet size changes, possibly due to diffusion of the collagen peptide from the inner to the outer water phase. Therefore, our findings can be utilized for preparing stable functional foods or cosmetic products from W1/O/W2 emulsions containing bioactive ingredients.