Starch constitutes the major macronutrient constituent in numerous deep-fried foods. In this study, the impact of starch physicochemical properties during deep-frying on the corresponding microstructural deformations were investigated for wheat starch (WS) and potato starch (PS) hydrated to 40 and 50 % moisture content (MC) using complementary techniques assessing (micro)structure in-situ (time-resolved X-ray microcomputed tomography and variable-temperature time domain proton nuclear magnetic resonance) and ex-situ (differential scanning calorimetry, swelling properties and scanning electron microscopy). Within 5 s of deep-frying, WS and PS swelling increased and most starch gelatinized, resulting in fully amorphous starch chains exhibiting high molecular mobility. Structure expansion during deep-frying (5-30 s), triggered by rapid steam generation in preexisting air pores, was supported by starch chains in a rubbery state. Notably, PS exhibited greater swelling, more extensive disruption of granule morphology, and formed larger pores in the microstructure compared to WS. With longer deep-frying times, WS and PS granular integrity was progressively lost. Expansion of steamfilled pores, and thus global structure, ceased when starch in the outer regions of the structure lost sufficient water and transitioned to a glassy state. Oil absorption during deep-frying strongly depended on the starting porosity of formulations. PS and WS at 40 % MC were highly porous before deep-frying and displayed considerable oil absorption immediately upon their submersion in oil when vapor pressures were still low. However, PS and WS at 50 % MC did not exhibit porous microstructures before deep-frying and showed no oil absorption during the process (60 s).

The combination of heat and enzymatic treatment on ovalbumin (OVA) has been shown to lead to a mixture of amyloid-like fibrils (ALFs) and peptides. Due to their gelling behavior, these mixtures are able to stabilize oil-inwater (O/W) emulsions. As peptides present alongside the OVA ALFs can impact interfacial behavior, it is necessary to remove them. Here, the ability to separate peptides from OVA ALFs by ultracentrifugation and dialysis was investigated. Size exclusion-high performance liquid chromatography results showed that dialysis produced pure OVA ALFs, while ultracentrifugation resulted in both a fibril- and a peptide-enriched fraction. Drop shape tensiometry confirmed that dialysis removed peptides, as a delayed decrease in interfacial tension indicated slower adsorption kinetics of larger structures. This was further supported by an increase in dilatational elasticity compared to samples containing peptides. Emulsions [10.0 % (O/W)] with only fibrils (obtained by dialysis) contained oil droplets that were noticeably larger than those in emulsions containing peptides. However, these emulsions exhibited high creaming and coalescence stability. In contrast, emulsions with peptideenriched OVA dispersions contained smaller oil droplets but were prone to coalescence due to the lack of a thick viscoelastic layer or a highly viscous continuous phase. The obtained results suggest that peptides, when present, preferentially adsorb at the interface, favoring small emulsion droplets, while the long OVA ALFs form a gel-like network in the continuous phase. This distinct interfacial behavior of peptides and ALFs, in the presence or absence of each other, may be useful when considering their use in food products.

The impact of soy protein concentrate (SPC) preparation method on its physicochemical properties and structure formation during processing with high moisture extrusion remains largely unexplored. In this study, SPCs were prepared by washing steps using acidic solutions at pH 4.5 or 5.5 (pH4.5- or pH5.5-SPCs), or using 50 % or 70 % aqueous ethanol solutions (E50- or E70-SPCs). The SPC protein dispersibilities, water-holding capacities, and rheological properties were analyzed at extrusion-relevant dry matter-to-waterlevels and related to structure and texture of extrudates made from these SPCs. pH4.5-SPC had the highest water-holding capacity, and E70-SPC the lowest. Rheological experiments showed higher complex viscosity of pH-SPCs heated to 140 degrees C and cooled to 60 degrees C compared to E-SPCs. Extrusion trials were conducted with a Thermo Fisher Process 11 extruder. pH-SPC extrudates exhibited anisotropic fibrous macrostructure and V-shaped protein-rich lamellae, whereas E70-SPC extrudates lacked distinct fibrous structure. X-ray tomography revealed thicker protein-rich lamellae in E70-SPC extrudates, indicating less pronounced syneresis during extrusion, which likely relates to its softer texture than the other extrudates. Correlation analysis suggested that rheological properties determined at extrusion-like temperatures can be indicative of extrudate texture. In conclusion, the used protein preparation protocol significantly impacted the physicochemical and rheological properties of SPCs, which then affected the structure and texture of extrudates made from these SPCs.

While wheat is a good source of iron (Fe) and zinc (Zn), their bioaccessibility is limited due to chelation with phytic acid. Sprouting wheat at 26 °C reduced the phytate content by 25-40 % and increased bioaccessibility (determined with an in vitro digestion assay) 1.5-2.7 times (Fe) and 1.6-2.3 times (Zn), depending on the sprouting time (48-120 h). Subsequent application of in vitro digests to Caco-2 cells showed that sprouting for 120 h at 26 °C did not enhance wheat Fe bioavailability, while it increased Zn bioavailability 1.6-fold. When the in vitro digests were exposed to diffusive gradients in thin film (DGT) with Chelex resin, which binds free mineral ions, sprouting was found to have caused release of non-labile Fe complexes and some labile Zn complexes. The latter resulted in higher levels of bioavailable forms of Zn in wheat.

Induction of amyloid-like morphology in food proteins offers high potential to induce new techno-functional properties in food products (e.g. use as emulsifier, thickener or gelling agent in e.g. bakery and confectionery products). However, the health impact of amyloid-like fibril (ALF) consumption remains widely understudied and merits additional research. The aim of this study was to (partially) elucidate the general health impact of food-borne ALF consumption, using egg white ovalbumin as a case study. Based on in vitro cell culture models it was demonstrated that ovalbumin ALFs (i) do not induce direct cytotoxic effects on intestinal (Caco-2, IPEC-J2) and neuronal (SH-SY5Y) cell lines, but (ii) are able to induce a Toll-like-receptor-mediated innate immune response, similar to endogenous amyloids, in activated THP-1 cells. Furthermore, the consecutive in vitro digestion and absorption (enterocyte and M-cell) experiments demonstrated that ovalbumin ALFs (i) do not completely lose their ALF morphology upon in vitro gastrointestinal digestion, and that (ii) the ALF core sequences, located at the center of the ALF structure, are transported across Caco-2 based cell models, suggesting aggregate transport. In vivo, intestinal translocation of ingested ALFs would imply potential cross-seeding of endogenous, disease-related precursor proteins. The ability of ovalbumin ALFs to induce aggregation of a disease-related precursor protein, αSyn, was evaluated in a precursor overexpressing cell model. Here, it was illustrated that only homologous (αSyn) - but not heterologous (ovalbumin) - seeding resulted in intracellular aggregation bodies of (phosphorylated) αSyn. The lack of cross-seeding supports the assumption that ovalbumin ALF consumption is not a risk factor for the development of α-synucleinopathies like Parkinson's disease.

The integration of emerging technologies and innovative functionalization techniques presents a promising strategy to address contemporary challenges involving dietary shifts, environmental and ethical issues associated with traditional protein consumption. Amyloid fibrils (AFs) are on the spotlight since they can deliver innovative techno-functional properties in food systems. Conventional proteins such egg white proteins (EWP) have demonstrated to form AFs under food processing conditions. Vegetable proteins, such as pea protein (PP) are pointed as a potential alternative for EWP but have limited techno-functionality. In this sense, ohmic heating (OH) was used for the first time as an assisting technology in protein fibrillation of EWP and PP. OH treatment of EWP dispersions induced the formation of AFs with distinct aggregation patterns and shorter length (ca. 65 nm) than the ones obtained by conventional heating (ca. 134 nm). Regarding PP fibrillation, the results point towards to a structural rearrangement of the existing fibrils, particularly when OH is applied. These findings open a perspective for using OH for tailoring food protein fibril formation and innovative food protein applications. Ultimately, this work underlines that, as any other functionalization strategy, plant protein fibrillation is more challenging than animal protein fibrillation. Industrial relevance: Research on food protein AFs formation has increased because of its potential to deliver specific techno-functionality (e.g., viscosity, gelling, emulsifying and foaming properties) in food systems. Recent reports show that animal and plant protein can fibrillate under food processing relevant conditions. In line with this, the use of emerging processing technologies such as OH to induce fibril formation is of high interest because of its ability to modulate protein structures. We here demonstrated that OH can be used under food processing relevant conditions for tailoring food protein fibril formation which can lead to novel food protein applications.

Soy protein concentrates (SPCs) are common food ingredients. They typically contain 65% (w/w) protein and similar to 30% (w/w) carbohydrate. SPCs can be obtained with various protein precipitation conditions. A systematic study of the impact of these different protein precipitation protocols on the SPC protein composition and physical properties is still lacking. Here, SPCs were prepared via three different protocols, that is, isoelectric (pH 3.5-5.5), aqueous ethanol (50%-70% [v/v]), and Ca2+ ion (5-50 mM) based precipitations, and analyzed for (protein) composition, protein thermal properties, dispersibility, and water-holding capacity. SPCs precipitated at pH 5.5 or by adding 15 mM Ca2+ ions had a lower 7S/11S globulin ratio (similar to 0.40) than that (similar to 0.50) of all other SPC samples. Protein in SPCs obtained by isoelectric precipitation denatured at a significantly higher temperature than those in ethanol- or Ca2+-precipitated SPCs. Precipitation with 50%-60% (v/v) ethanol resulted in pronounced denaturation of 2S albumin and 7S globulin fractions in SPCs. Additionally, increasing the precipitation pH from 3.5 to 5.5 and increasing the Ca2+ ion concentration from 15 to 50 mM caused a strong decrease of both the dispersibility of the protein in SPC and its water-holding capacity at pH 7.0. In conclusion, this study demonstrates that the SPC production process can be directed to obtain ingredients with versatile protein physicochemical properties toward potential food applications.Practical ApplicationThis study demonstrates that applying different protein precipitation protocols allows obtaining SPCs that vary widely in (protein) composition and physical properties (such as protein dispersibility and water-holding capacity). These varying traits can greatly influence the suitability of SPCs as functional ingredients for specific applications, such as the production of food foams, emulsions, gels, and plant-based meat alternatives. The generated knowledge may allow targeted production of SPCs for specific applications.

Oil acts as a high-temperature heating medium while also contributing to the organoleptic properties in energy dense deep-fried foods. The amount of oil absorbed is associated with the rapid structural deformation of food during deep-frying, creating pathways for oil to enter the internal microstructure. Here, we describe a 4D imaging system (three spatial dimensions and time) that uses fast synchrotron radiation tomography for in-situ visualization of the highly dynamic deep-frying and post-frying cooling processes. We use dynamic imaging and 3D quantification to show that the continuously evolving connectivity of the heterogeneous porous microstructure in a wheat flour-based dough is altered by the deformations induced during and after deep-frying. The resulting pore network integrity, more than porosity, significantly impacts the rate of oil uptake and its distribution. The findings also suggest that a two-stage deep-frying operation at different temperatures can help reduce oil content while achieving a desired crust.

The aim of this work was to investigate wheat gluten protein network structure throughout the deep-frying process and evaluate its contribution to frying-induced micro- and macrostructure development. Gluten polymerization, gluten-water interactions, and molecular mobility were assessed as a function of the deep-frying time (0 - 180 s) for gluten-water model systems of differing hydration levels (40 - 60 % moisture content). Results showed that gluten protein extractability decreased considerably upon deep frying (5 s) mainly due to glutenin polymerization by disulfide covalent cross-linking. Stronger gliadin and glutenin protein-protein interactions were attributed to the formation of covalent linkages and evaporation of water interacting with protein chains. Longer deep-frying (> 60 s) resulted in progressively lower protein extractabilities, mainly due to the loss in gliadin protein extractability, which was associated with gliadin co-polymerization with glutenin by thiol-disulfide exchange reactions. The mobility of gluten polymers was substantially reduced during deep-frying (based on the lower T2 relaxation time of the proton fraction representing the non-exchanging protons of gluten) and gluten proteins gradually transitioned from the rubbery to the glassy state (based on the increased area of said protons). The sample volume during deep-frying was strongly correlated to the reduced protein extractability (r = -0.792, p < 0.001) and T2 relaxation time of non-exchanging protons of gluten proteins (r = -0.866, p < 0.001) thus demonstrating that the extent of gluten structural expansion as a result of deep-frying is dictated both by the polymerization of proteins and the reduction in their molecular mobility.

The texture of potato mash significantly influences consumer satisfaction. We here investigated the impact of blanching and different methods thereof on the texture and extractable extracellular fractions (EEFs) of potato mash when extracted with water or with dimethyl sulfoxide (DMSO) to seek determining factors of potato mash texture. Mashes prepared from potatoes blanched in 2.04 mM CaCl2 (CaB-M) exhibited hardness (24.9 N) and stickiness (1.0 N & sdot;s) readings intermediate to those from potatoes that were not blanched (NB-M, 19.2 N and 1.2 N & sdot;s), or blanched in deionized water (WaB-M, 30.5 N and 0.6 N & sdot;s), which aligned with their levels of intact cells. Starch was the main constituent (57.2 % - 64.4 %, w/w) in all EEFs and more starch was present in (1) NB-M and (2) the DMSO extracts. The chain length distributions of DMSO-extracted extracellular starch (DEES) revealed that the amylopectin content increased in the order WaB-M (46.3 %), CaB-M (55.1 %), and NB-M (76.6 %), which was attributed to more intracellular amylopectin being released to the extracellular phase of mashes. The relative contents of shorter chain amylose (degree of polymerization 110-1000) and the DEES yield were significantly correlated to the hardness while the yield of DEEFs was positively correlated with the stickiness.

An I-optimal response surface experimental design revealed impacts of dough moisture content (DMC, 14-22%) and level of wheat flour substitution (10-50%) by wheat gluten and one of six different native starches [wheat, (waxy) maize, rice, potato, pea] on sugar-snap cookie starch thermal properties, in vitro starch digestion, dough and cookie hardness and spread ratio. Increasing DMCs from 14 to 22% increased the cookie starch digestion rate constants of each starch source used. A linear increase of the constant by 25-30% across the 14 to 22% DMC range for all starches was predicted and validated. That cookie spread and hardness were related to the water retention capacity of the native starches used suggested that they underwent limited changes during baking. For each starch examined, formulations were optimized to lower in vitro starch digestion rate and extent, and cookie hardness, while maximizing dough spread ratio.

Cakes are produced in different ways, with pound, cream and sponge cake being examples. While cream and pound cake are made from emulsion-type batters, sponge cake stems from a foam-type batter rich in gas bubbles. For these different cake systems, the influence of mixing atmospheres, containing different levels of nitrogen (N2) and carbon dioxide (CO2), on batter and cake properties were investigated. Regular pound cake is not positively influenced by enriching the mixing atmosphere with CO2. However, using 50% N2 -50% CO2 mixing atmosphere elevates the quality of reduced sucrose pound cakes to be similar to that of regular pound cake. Using CO2 in the mixing atmosphere of cream cake batter increases cake quality, with 50% of CO2 in the mixing atmosphere providing optimal leavening during baking. CO2 has a negative effect on sponge cake hardness and specific volume. The cohesiveness, springiness and resilience stayed similar or increased in all cake types when increasing the concentration of CO2 in the mixing atmosphere.

Maize zein based nanoparticles (ZNPs) can have applications as food dispersion stabilizers. It has not been documented to what extent the used zein isolation method and conditions thereof impact the structure and functionality of nanoparticles (NPs) based thereupon. Here, zein extracted from maize flour on lab scale (LS-zein) was compared with a commercial zein powder (CS-zein). On a dry matter basis, CS-zein contained 96.5% protein, while LS-zein contained 74.5% protein, 12.7% lipid, 2.9% ash, and a residual fraction, likely starch remnants. SE-HPLC analysis showed that 27.8% of CS-zein protein occurred in an aggregated and insoluble form, while LS-zein mainly contained mono-/dimeric proteins but also approximately 30% hydrophilic peptides. These differences resulted in notably different behavior in the functionality of ZNPs based on CS- and LS-zein (CS-ZNPs and LS-ZNPs, respectively) produced via liquid antisolvent precipitation. CS-ZNPs had poor foaming properties regardless of the pH, in line with their low interfacial dilatational moduli (12.9-15.0 mN/m). The foaming properties of LS-ZNPs were notably better. The high LS-ZNP foam stability (FS) at pH 8.0 and 10.0 was attributed to electrostatic repulsive effects between interfaces of adjacent air bubbles due to the adsorption of peptides and to synergistic protein-lipid interaction effects at the air-water interface. The LS-ZNP FS at pH 4.0 was low despite a high interfacial dilatational modulus (52.6 mN/m). It is hypothesized that intact LS-ZNPs in the liquid thin films between gas bubbles negatively affect FS by a bridging de-wetting effect. Overall, it can be concluded that the (partial) co-isolation of lipids with zein may positively influence foaming properties of NPs based thereupon, while extensive zein purification as applied in industrial zein isolation leads to (partial) zein aggregation and overall low foaming capacity of the obtained CS-ZNPs.

Hen egg white protein (EWP) is an ingredient in many food products. EWP containing amyloid-like fibrils (ALFs) can be prepared under food processing relevant conditions and have specific techno-functional properties which advantageously can be exploited in specific food products. Here, we investigated whether combinations of heating and NaCl addition or trypsin treatment improve EWP fibrillation and gel properties. Heating (75 degrees C, 150 min) control 0.2% EWP solutions resulted in limited fibrillation unless they also contained 150 mM NaCl, in which case increased levels of curly ALFs were observed. When similarly heated control EWP solutions were submitted to trypsin treatment (37 degrees C, 24 h, 150 rpm), both straight and curly ALFs were formed. Gels [5.0%- 6.0% (w/v) EWP] prepared by heating (75 degrees C, 150 min) of 150 mM NaCl containing dispersions or by similar heating without NaCl addition but with trypsin treatment contained ALFs of similar morphology but shorter than those in control EWP solutions. Increased levels of curly or of both straight and curly ALFs in NaCl containing gels or gels prepared with trypsin treatment, respectively, resulted in higher EWP gel stiffness than when the EWP gels were prepared in water. While the presence of straight ALFs in trypsin-derived EWP gels resulted in fast gel breakdown, the presence of both curly and straight ALFs reduced the amount of EWP needed for gel for-mation. The level and morphology of EWP ALFs can thus be modulated by specific food relevant processing and the resultant ALFs have specific gelling properties.

Starch is the main source of dietary energy for humans. In order to understand the mechanisms governing native starch in vitro digestion, digestion data for six starches [wheat, maize, (waxy) maize, rice, potato and pea] of different botanical sources were fitted with the most common first-order kinetic models, i.e. the single, sequential, parallel and combined models. Parallel and combined models provided the most accurate fits and showed that all starches studied except potato starch followed a biphasic in vitro digestion pattern. The biological relevance of the kinetic parameters was explored by determining changes in crystallinity and molecular structure of the undigested starch residues during in vitro digestion. While the crystallinity of the undigested potato starch residues did not change substantially, a respectively small and large decrease in their amylose content and chain length during in vitro digestion was observed, indicating that amylose was digested slightly preferentially over amylopectin in native starch. However, the molecular structure of the starch residues changed too slowly and/or only to an insufficient extent to relate it to the kinetic parameters of the digested fractions predicted by the models. Such parameters thus need to be interpreted with caution, as their biological relevance still needs to be proven.

Cakes are chemically-leavened sugar-rich bakery products. Depending on the cake type, air is incorporated differently during mixing. Sponge cake batter is a gas bubble rich foam, while cream cake batter is an emulsion containing less gas cells. Given the consumer interest in reduced sucrose food systems, we here examined the potential of using altered mixing atmospheres [pure nitrogen (N2) 2 ) or carbon dioxide (CO2)] 2 )] to improve reduced sucrose cake quality. The use of poorly soluble N2 2 resulted in voluminous, stable batter. This was especially the case for foam-type sponge cake batters. During baking of sponge and cream cake batters, leavening was similar for batters prepared either under air or N2, 2 , resulting in similar cake qualities. Use of the highly soluble CO2 2 as mixing atmosphere negatively affected batter density, but positively leavening during baking due to temperature induced release of previously solubilized CO2. 2 . In foam-type sponge cake making, the significant negative effect of CO2 2 on batter density was not overruled by the positive effect of CO2 2 release during leavening/baking. In contrast, the CO2 2 mixing atmosphere during batter-type cream cake making had only a limited negative effect on batter density while greatly affecting leavening, and resulting in high-quality, voluminous (reduced sucrose) cakes.

The (joint) contribution of soy proteins and dietary fibers (DFs) in determining the structure and texture of high moisture extrudates remains largely unclear. Blends of soy protein isolate (SPI) and a soy DF-enriched fraction (SDF) were prepared in different ratios, and their bulk rheology and water mobility distribution when hydrated to 60% moisture were related to the structure, texture, and protein extractability of high moisture extrudates prepared at the same moisture level. Increasing the DF proportion in hydrated SPI-SDF blends resulted in higher storage and loss moduli in linear region. In the non-linear region, however, higher DF levels resulted in more viscous behavior. The mobility of weakly interacting water protons decreased in samples with more DF. High moisture extrudates made from SPI had a layered microstructure consisting of V-shaped lamellae. Extrudates prepared from a blend containing 25% DF had more fibrous appearance with thin, branched protein-rich lamellae. Extrudates containing 52% DF exhibited a macrostructure without the presence of distinct layers or fibers and lacked a continuous protein network in their microstructure. The contribution of disulfide bonds to sustaining the protein network increased in extrudates containing more DF. Extrudates containing more DFs had lower cutting strengths and anisotropic indices. Strong negative correlations were found between the phase angle (obtained at 95 °C) in the non-linear region of the hydrated blends (indicating the relative importance of the viscous response) and the cutting strength of the extrudates in both longitudinal (R = -0.759) and perpendicular (R = -0.883) directions to the flow. In conclusion, the ratio of soy protein to DF had a significant impact on the characteristics of high moisture extrudates, which were associated with alterations in rheological properties, water mobility distribution and protein extractability.

The particle size of milled soft wheat used in cookie making affects the in vitro digestion of the cell wall encapsulated starch material.

Background and ObjectivesIn the accompanying paper (Part 1), it was reported that forced convection roasting of wheat before milling can be directed to tailor the viscosifying properties of flour. The objective of the present work was to examine the effect of prior wheat roasting on flour proteins.FindingsEffective control of wheat roasting conditions proved to be essential to avoid the irreversible loss of flour functionality as deduced from the flour ethanol and lactic acid solvent retention capacity and mixography data. Response surface models predicted roasting at 108 degrees C and 80 Hz (135 s) to maintain protein integrity. The microstructure of flour and isolated starch as well as X-ray diffraction patterns revealed starch to be relatively unaffected by this heat treatment.ConclusionsFlour produced from roasted wheat can still be used for products that require the formation of a gluten network.Significance and NoveltyProtein is more sensitive to roasting conditions than starch.

Background and ObjectivesDry thermal treatment of wheat modifies the properties of wheat and of flour prepared from it. The objective of this study was to investigate the effect of wheat roasting on microstructural properties of wheat grains using confocal laser scanning, X-ray diffraction (XRD), and scanning electron microscopy (SEM) techniques. The impact of roasting on the damaged starch contents, the solvent retention capacity profiles, and the pasting properties of the resulting flour prepared from roasted wheat were also studied.FindingsResponse surface models predicted wheat roasting at 115 degrees C and 65 Hz (165 s) to enhance flour viscosifying properties. Roasting before milling resulted in grain puffing, slight damage to the starch granule surface, and destruction of the protein matrix, as observed using SEM. XRD analysis revealed that amylose-lipid complexation had occurred. As a result of roasting, the peak, hot paste, and final viscosities of flour from roasted wheat were significantly (p <= .05) higher than those of flour produced from control wheat.ConclusionsRoasting induces structural changes in wheat. Flour produced from roasted wheat can be used to produce gel structures with increased viscosities.Significance and NoveltyDry thermal treatment improves the viscosifying properties of flour milled from roasted wheat.