Mechanisms controlling wheat starch gelatinization and pasting behaviour in presence of sugars and sugar replacers : Role of hydrogen bonding and plasticizer molar volume

The effect of sugars and sugar replacers (i.e. plasticizers) on the gelatinization and pasting behaviour of wheat starch was studied. The intrinsic properties of the plasticizers, i.e. the molar volume density of effective hydroxyl groups NOH,s/vs, and the volumetric density of hydrogen bonds in the sugar solutions treated as a single solvent, i.e. Φw,eff, were proposed as factors controlling swelling (i.e. pasting) and gelatinization behaviour. Different classes of plasticizers were used including sugars, polyols, amino acids, soluble fibres such as oligofructoses, and mixtures thereof. The onset, peak and end temperature of starch gelatinization obtained by differential scanning calorimetry could be well described by Φw,eff for all solutions, following predictions from an adapted Flory-Huggins model for polymer melting. The multiple transitions involved in starch gelatinization could be well related to different ranges of Φw,eff following a side chain liquid crystalline model for starch. Deviations from the model predictions were observed mainly for Tonset in conditions of intermediate and excess solvent with high sugar concentrations (50% w/w). In such conditions phase separation likely occurs, increasing the effective starch concentration and consequently gelatinization temperatures. Pasting behaviour related to swelling, i.e. peak viscosity, was found to be a sigmoidal Fermi function of NOH,s/vs of the plasticizers. Plasticizers with high NOH,s/vs enhanced swelling compared to water while those with low NOH,s/vs had an inhibition effect. Overall, a comprehensive mechanism of starch plasticization, swelling and melting is proposed. Swelling associated with solvent ingress and helix-helix dissociation is affected by kinetic factors related to size and viscosity of the plasticizers (both described by NOH,s/vs) and by thermodynamic factors related to sugar partitioning and H-bonding ability (both related to Φw,eff). Melting of crystalline domains associated to helix-coil transition is controlled by thermodynamics, based on solvent H-bonding ability Φw,eff

Amino acids, polyols and soluble fibres as sugar replacers in bakery applications : Egg white proteins denaturation controlled by hydrogen bond density of solutions

In this paper we demonstrate that the denaturation behavior, i.e. Tden, of egg white proteins in sugar and sugar replacer solutions is explained by the volumetric density of hydrogen bonds in the solutions, i.e. nOH,eff. The validity of the presented approach is demonstrated using 18 solutions comprising single compounds as well as 7 ternary/quaternary mixtures. Different classes of plasticizers are used at various concentrations and at various ratio with proteins. Sweet amino acids such as L-proline and glycine are included as novel alternatives to polyols. The experimental data are modelled with the Flory-Huggins (FH) theory for biopolymer melting. For such purpose, solutions are treated as a single solvent, which is described by the effective volume fraction of the solvent Φw,eff (⁓nOH,eff). Overall, the FH model can well describe the denaturation behavior of egg white proteins in sugar and sugar replacer solutions up to 30% concentration. Deviations from the model become particularly evident at high sugar concentrations (i.e. 50%), which relate to conditions of phase separation in a protein-rich and sugar-rich domain. In such conditions, Φw,eff does not reflect the composition of the solvent around the proteins. An elevation in Tden is observed due to a reduction in hydrogen bond density in the protein-rich domain. The results indicate that phase separation is driven by both the concentration and the molar volume density of effective hydroxyl groups NOH,s/vs of the plasticizers or plasticizer mixtures. Finally, the proposed approach can predict key phase-transitions which result in protein network formation in pound cake baking

Water release kinetics from soy protein gels and meat analogues as studied with confined compression

In this paper, we report on the use of confined compression to study the water release properties from food gels and model meat analogues. Confined compression is a novel method in food science that provides information on the dynamics of water release under mechanical load. Confined compression measurements are compared with numerical simulations based on Flory-Rehner theory. Simulation results for soy protein gels are in reasonable agreement with experiments, while they underestimate the water release from model meat analogues. Time-domain nuclear magnetic resonance (TD-NMR) revealed the presence of internal water-filled cavities in the meat analogues. These cavities could provide a path of low resistance for the water to travel through. However, they are not captured by our current model, which explains the higher fluxes observed experimentally. Our results indicate a relation between the water release properties of meat analogues and pore structure. Control of the pore structure might, therefore, provide new opportunities to improve meat analogue juiciness

Enhancing the water holding capacity of model meat analogues through marinade composition

Meat analogues can offer consumers a more sustainable alternative to meat. A successful meat analogue is characterized by a meat-like texture and high juiciness. Juiciness is related to the water holding capacity (WHC). To gain an understanding of how to control the WHC via external conditions, we investigate the effect of ionic strength and pH on water uptake. Model meat analogues were prepared in a Shear Cell and swollen in baths of known pH and ionic strength. The effect of bath composition on water uptake was determined experimentally, and simulated using Flory–Rehner theory. Experiments and simulations were in qualitative agreement. The results show that water uptake increases with an increasing difference between bath pH and the protein's iso-electric point (pI). At low ionic strengths, the internal pH is near the pI, resulting in reduced swelling. At high ionic strengths, the charge imbalance between gel and bath is limited, also resulting in reduced swelling. At intermediate ionic strengths, swelling increases with decreasing bath ionic strength. Cross-link density negatively relates to WHC and can be controlled via the addition of cross-linking and reducing agents. This work shows that by carefully choosing marinade pH and ionic strength, the WHC of meat analogues can be controlled. These advancements can help improve the sensory characteristics and yield of meat analogues and could enable the production of reduced-salt products.</p

The importance of swelling for in vitro gastric digestion of whey protein gels

In this paper we report the importance of swelling on gastric digestion of protein gels, which is rarely recognized in literature. Whey protein gels with NaCl concentrations 0–0.1 M were used as model foods. The Young's modulus, swelling ratio, acid uptake and digestion rate of the gels were measured. Pepsin transport was observed by confocal laser scanning microscopy using green fluorescent protein (GFP). With the increase of NaCl in gels, Young's modulus increased, swelling was reduced and digestion was slower, with a reduction of acid transport and less GFP present both at surface and in the gels. This shows that swelling affects digestion rate by enhancing acid diffusion, but also by modulating the partitioning of pepsin at the food-gastric fluid interface and thereby the total amount of pepsin in the food particle. This perspective on swelling will provide new insight for designing food with specific digestion rate for targeted dietary demands.</p

Shear-induced self-diffusion and microstructure in non-Brownian suspensions at non-zero Reynolds numbers

This paper addresses shear-induced self-diffusion in a monodisperse suspension of non-Brownian particles in Couette flow by two-dimensional computer simulations following the lattice-Boltzmann method. This method is suited for the study of (many-particle) particulate suspensions and can not only be applied for Stokes flow, but also for flow with finite Reynolds number. At relatively low shear particle Reynolds numbers (up to 0.023), shear-induced diffusivity exhibited a linear dependence on the shear rate, as expected from theoretical considerations. Simulations at shear particle Reynolds numbers between 0.023 and 0.35, however, revealed that in this regime, shear-induced diffusivity did not show this linear dependence anymore. Instead, the diffusivity was found to increase more than linearly with the shear rate, an effect that was most pronounced at lower area fractions of 0.10 and 0.25. In the same shear regime, major changes were found in the flow trajectories of two interacting particles in shear flow (longer and closer approach) and in the viscosity of the suspension (shear thickening). Moreover, the suspended particles exhibited particle clustering. The increase of shear-induced diffusivity is shown to be directly correlated with this particle clustering. As for shear-induced diffusivity, the effect of increasing shear rates on particle clustering was the most intensive at low area fractions of 0.10 and 0.25, where the radius of the clusters increased from about 4 to about 7 particle radii with an increase of the shear Reynolds number from 0.023 to 0.35. The importance of particle clustering to shear-induced diffusion might also indicate the importance of other factors that can induce particle clustering, such as, for example, colloidal instability

More efficient mushroom canning through pinch and exergy analysis

Conventional production of canned mushrooms involves multiple processing steps as vacuum hydration, blanching, sterilization, etc. that are intensive in energy and water usage. We analyzed the current mushroom processing technique plus three alternative scenarios via pinch and exergy analysis. The product yield, utility use, exergy loss, and water use are used as sustainability indicators. Whilst re-arrangement of the production process could maximally save up to 28% of the heat input and up to 25% of the water usage, the most important improvement is obtained by re-using blanch water, which improves the overall yield of the preservation and canning process by 9%, also saving water and exergy use in the production