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The performance of 3D food printing for hydrogels largely depends on the gel spatial structure and water state. However, the mechanism of microstructure and water state that affects the 3D printing performance of hydrogels remains unclear. Our previous studies found that the hydrogel made from honey bee pupae, a rich source of high-quality protein, has good fluidity but poor structural stability, limiting its use in 3D printing. Based on it, honey bee pupa protein (HBPP) added with soybean dietary fiber (SDF) was selected as a case study in this work. The results revealed that HBPP gel had good fluidity but weak mechanical strength, which was guided by the firm immobilization of water molecules and the lack of a rigid three-dimensional network structure. However, upon adding SDF, the rigid network structure of HBPP gel was enhanced and the degree of water immobilization was reduced. HBPP-SDF gel had better structural stability than HBPP gel and lower water migration ability than SDF gel. Additionally, SDF and HBPP complemented each other, thereby improving the 3D printing performance of the gel. Based on the findings, a possible microstructure evolution mechanism of different types of gels during 3D printing was proposed. Out of all the HBPP-SDF gels evaluated, the HBPP-SDF gel with an optimum SDF concentration of 30% demonstrated the best printing performance. [Display omitted] • Addition of SDF enhanced the network structure and mechanical strength of mixed gel. • Immobilized water in network of SDF gel was easily detached under external force. • SDF filling into HBPP matrix enhanced 3D printing adaptability of individual gel. • 30% SDF level yielded best 3D print adaptability compared to other formulations. • Microstructure evolution mechanism of hydrogels during 3D printing was proposed. [ABSTRACT FROM AUTHOR]

Abstract Edible insects offer a huge potential as a new source of proteins for food and feed and as a promising functional agent. In this regard, our study aimed to evaluate the effect of pH and temperature on aggregation and gelation of honey bee brood (Apis mellifera). Aggregation of soluble proteins was dependent on temperature and pH value and the highest coagulation was reached at 85 °C at pH 5 and 7 (73.7 and 68.4%, respectively). Changes in protein surface hydrophobicity, net charge and amount of available and buried sulfhydryl groups demonstrated the contribution of either covalent or non-covalent intermolecular interactions resulted in aggregation at various pH. The least gelation concentration of raw powder from honey bee brood varied from 5 to 11% on raw powder basis at pH 7 and 3, respectively. Moreover, the effect of pH on rheological and textural properties, as well as gel microstructure from honey bee brood is discussed. Therefore, freeze dried raw powder of honey bee brood has rich nutritional value and demonstrated gelation concentration comparable to conventional protein sources that reveal its potential as an ingredient for insect-based gel product. Graphical abstract Image 1 Highlights • Coagulation of honey bee brood proteins is a pH and temperature-dependent. • Size of coagulated soluble proteins varied as a function of pH and temperature. • Heating induced changes in surface hydrophobicity, charge, SH groups of proteins. • Least gelation concentration of honey bee brood raw powder – 5% on raw basis at pH 7. • Textual properties and gel microstructure were affected by pH alteration. [ABSTRACT FROM AUTHOR]

Starch digestibility strongly depends on the food composition and microstructure formed during food processing. Identifying the interplay among food ingredients is vital to design starch-based foods with low digestibility. In this work, the effects of native and enzymatic (pepsin and pancreatin) hydrolyzed rice proteins on structural features, enzyme activity and digestibility of cooked rice starch were systematically investigated. All protein and its hydrolysates showed potent abilities in mitigating starch digestion. Native and pepsin hydrolyzed proteins increased starch retrogradation extent and thus increased ordered and aggregated structures of cooked starch. Pepsin-pancreatin hydrolyzed proteins displayed anti-retrogradation activity and decreased starch ordered structures, however, increased V-type inclusion complexes and displayed a potent mixed-type (competitive and non-competitive) inhibitory activity against α-amylase. Based on these findings, it can be concluded that native and pepsin hydrolyzed proteins decreased starch digestibility via increasing ordered structures of cooked starch, while pepsin-pancreatin hydrolyzed proteins mitigated starch digestion by the synergistic effects of V-type structures enhancement and mixed-type suppression activity against α-amylase. The data is of significant to formulate low glycemic health-promoting food products via native or proteolytic proteins complexation. [ABSTRACT FROM AUTHOR]

The 7S and 11S globulins, the main protein fractions found in legumes, may differ in functionality. This study evaluated gel formation and rheological and microstructural properties of gels formed from the 7S and 11S protein fractions of faba bean. The effect of adding sodium chloride (NaCl) was also investigated. In terms of rheological and mechanical properties, NaCl addition appeared to have an opposing effect on 7S and 11S gels. Gels formed from 7S showed increases in storage modulus and peak stress when NaCl was added, whereas gels formed from 11S showed decreases. Microstructural changes were observed only for 7S gels, for which addition of NaCl resulted in transition from a fine-stranded to a coarse-stranded gel network. The 11S gels showed a fine-stranded gel network at all NaCl concentrations investigated. Gels formed from a mixture of 7S and 11S (7S:11S ratio 3:7) showed similar rheological properties and microstructure as the 11S gels. [Display omitted] • 7S and 11S protein fractions were successfully extracted from faba bean. • NaCl had opposing effects on the rheological properties of 7S and 11S gels. • Upon addition of NaCl, microstructural changes were observed only for 7S gels. [ABSTRACT FROM AUTHOR]

Recently, the demand for protein-rich ingredients derived from non-animal sources has increased as possible alternatives to animal proteins for products, such as quinoa, lentil, and rice sources, which have great potential to generate innovative products. The objective of this work was to determine the influence of different proportions of rice and lentil in mixtures with desaponified precooked quinoa flour and hyper-protein quinoa flour under specific conditions (pH 5 and 7) on the properties of zeta potential, flow behavior, properties pasting, oscillatory tests and creep recovery. Rheological behavior of dispersions was characterized before and after a heating process. Results showed that applying temperature at 80 °C form gels with contributions in the yield stress, consistent index with the Hershel-Bulkley model. Pasting properties were affected by pH and addition of rice and lentils. The oscillation test, and the treatments presented (G' > G″), indicating an interconnected gel-like network. Results show that lentil flour incorporation and pH improve gels' rheological stability and affect the masses' microstructure. These impacts are more obvious at high concentrations, which suggest that these treatments have potential for innovations in the food industry. [Display omitted] • Rheological properties of quinoa, lentil, rice dispersions were analyzed. • Lentil and rice flour and pH affect the rheological properties of quinoa flour. • During a warm-up process, pseudoplastic behavior occurred. • Protein dispersions with high lentil flour concentrations presented stronger gels. [ABSTRACT FROM AUTHOR]

Starch and protein are major components in many foods, contributing to nutritional and textural properties. Understanding how the behaviour and interactions of these components contribute to different textures is important. In this study, mixed gel systems were created with different ratios of starch to protein (constant solid content 12%) extracted from faba bean, a promising crop for locally produced plant-based foods in cold climate regions. The mixed starch-protein gels were characterised in terms of pasting, texture and microstructure. Starch-rich mixtures showed higher water binding and water absorption than samples with higher protein content. A tendency for more efficient hydration in starch-rich samples was confirmed by NMR. Iodine affinity appeared to be lower for high-protein samples, particularly at higher temperatures. Mixtures with high starch content also showed higher viscosity during pasting, higher storage modulus throughout gelation, lower tan δ and lower frequency dependence of the final gel. Characterisation by compression tests showed stronger and more elastic gels with increasing starch content. Light microscopy revealed that starch granules were tightly packed, especially at higher starch content, with protein filling the spaces between starch granules. SEM micrographs revealed a network structure with larger pores and thicker strands in samples with higher starch content. Overall, increasing protein content reduced viscosity during pasting and caused softer gels, likely owing to different gelation and hydration properties of starch and protein. [Display omitted] • Pasting temperature increased and viscosity decreased as protein replaced starch. • Gels became softer as protein replaced starch. • Water binding and textural/rheological properties improved with starch content. • NMR revealed better hydration in starch-rich samples, affecting granule swelling. • LM and SEM revealed different microstructures in starch and protein networks. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the water distribution in maize starch (MS) and pea protein isolate (PPI) composite gels and understand how the separate contributions of MS and PPI affect the mechanical properties of composite gels with varying MS/PPI ratios. A series of MS gels with increasing PPI contents and a series of PPI gels with increasing MS contents were prepared. The water distribution was evaluated with a novel image analysis method using confocal laser scanning microscopy (CLSM). This method was used to quantify the volume fraction of each phase, from which the water distribution between the starch phase and the protein phase within the gels was estimated. Depending on the MS/PPI ratios, either a dispersed or a bicontinuous gel was formed. The estimated stiffness of each phase was used to estimate the gel stiffness using models for either dispersed or bicontinuous structures. These predictions were shown to be in good agreement with experimental data obtained from compression tests. The determination of the properties of each phase separately allowed us to determine which phase dominated the properties of the composite gel. In filled gels, the MS network dominated the gel properties, unless the stiffness of PPI fillers was remarkably higher than that of the MS network. In bicontinuous gels, the stiffness of the composite gels was determined by the network with the highest stiffness. Dispersing pea protein aggregates (PPA) with different size into MS gels resulted in minor differences in mechanical properties compared to PPI-MS gel. These results show that this new analysis method can be used to predict water distribution within gels, and how this leads to changes in the stiffness, hardness and brittleness of the gels. [Display omitted] • Water distribution can be estimated with a CLSM imaging analysis method. • Uneven water distribution was observed in all studied starch-protein gels. • Stiffness estimated based on theoretical models was in good agreement with experimental data. • In composite gels, the stiffer component dominates the gel properties. [ABSTRACT FROM AUTHOR]

Whey protein isolate – WPI/cellulose fibers were obtained combining formation of cellulose fibers with acid induced gelation of whey protein in the simultaneous process. The mechanical properties of the cellulose fibers were improved by adding whey protein. Regenerated cellulose fibrils exhibited a dense structure with voids of several micrometers pore size. The blend fibers were smoother than cellulose fibers with smaller void spaces and attached protein filaments. On the surface of the regenerated cellulose fibers, formation of hierarchical flowerlike micro/nanostructures was observed. The XRD pattern indicated that the flowerlike microstructure was composed of ammonium copper(II) sulfate hexahydrate. Regenerated cellulose alone and in the mixtures with WPI crystallized partly in the cellulose II monoclinic system. For cellulose/WPI blend reduction in –C–OH groups was observed, which was probably caused by interactions of cellulose with the protein molecules. The obtained blended cellulose/WPI fibers can have tremendous potential use in medicine, tissue engineering and as a material for active ingredients release. [ABSTRACT FROM AUTHOR]

Abstract: The microstructure of oil droplets of bi-layer emulsions was studied as a function of pH (i.e. 7, 5, and 3) using scanning electron microscopy. The bi-layer emulsions consisted of a primary emulsion: 5 wt% soybean oil (SBO) in a 1% protein (nonfat dry milk) aqueous solution. The secondary layer was ι-carrageenan, high- (HMp), low (LMp)-methoxyl pectin, or gelatin. The secondary emulsions consisted of 2.5% SBO, 0.5% protein, and 0.2% polysaccharide or protein. Gelatin secondary emulsions were stable at pH 7 with defined droplets and became unstable at pH 5 and 3. The destabilization mechanisms for these emulsions at pH 5 and 3 were different as observed with the SEM: at pH 5 there is complete aggregation of protein due to their proximity to the isoelectric point; and at pH 3 the droplets are perfectly separated, suggesting that at this pH, when the net charge is positive, the destabilization is mainly due to depletion flocculation. HMp secondary emulsions shift from being stable (individual droplets) at pH 3 to being unstable at pH 7 where an extensive webbing is observed between the droplets at this pH value. The ι-carrageenan secondary emulsions are stable at each pH and the individual droplet microstructure is minimally altered as the pH changes. LMp secondary emulsions shift from being stable at pH 7 with individual droplets observed in the SEM micrographs to being unstable at pH 3 where extensive webbing is observed in the SEM micrographs. [Copyright &y& Elsevier]

Abstract: Gelling profiles and interaction between basil seed gum (BSG) and β-lactoglobulin (BLG) were characterized using dynamic rheology and scanning electron microscopy. Sequence of experimental sweeps of time–temperature, frequency, and strain were applied for BSG, BLG and BLG–BSG mixtures in the ratio of 10:1, 5:1, 2:1 & 1:2. Rheological behavior of BLG was found to be different from that of BSG and gelling point was raised during the heating period. By increasing BSG concentration, storage and loss moduli were increased and gel point was determined at about 80 °C, which was dependent of concentration and occurred during cooling period. Upon heating–cooling period (temperature sweep) of BLG–BSG mixture from 20 °C to 90 °C and coming back to original temperature, mixed gels presented a biphasic profile: the first phase, characterized by a sharp increase in the storage modulus in which gelation of BLG happened and the second phase exhibiting an increase in the storage modulus, corresponded to the build-up of a BSG network. Strain sweep results obtained for mixed gels at the end of the temperature sweep tests supported the biphasic hypothesis. The SEM results showed that BLG has a globular structure in comparison with BSG which has fibril and globular structure and the mean diameter of its globular structure was higher than that of BLG. Increasing the ratio of BSG to BLG resulted in a finer microstructure, which could retain higher water to form gel. In addition, microstructural study showed that BLG–BSG mixed is a bicontinuous network in which BSG dispersed in BLG continuous phase. [Copyright &y& Elsevier]

Abstract: This article provides a summary of an example of how relationships between molecular scale properties and macroscopic properties are formulated, in this case with a focus on fibril microstructures and according system elasticity. Entropy plays a dominant role on all length scales. The elasticity is reviewed in terms of the micro-mechanical properties of the fibrils over a wide range of concentrations. The elasticity is concluded to be of an entropic nature. The micro-mechanical fibril property is the persistence length. For fibrils based on globular proteins the response to temperature change and flow has been reported to be either reversible or non-reversible, dependent on the age of the fibril. The reversibility is argued to be related to the fact that the fibril consists of peptides originating from hydrolysis of the globular proteins, and that the initial step of fibrillar peptide assembly is entropic of nature. The longer term irreversibility is speculated to be caused by a secondary assembly step being a collective transition into inter-beta-sheets. [Copyright &y& Elsevier]

Abstract: The microstructural and large deformation rheological properties of model food gels were studied by performing notch propagation tensile testing on the gels using a tensile stage and observing changes in the microstructure of the gels during tensile testing using confocal laser scanning microscopy (CLSM). Heat-set whey protein (WP) gels containing either added sodium caseinate (NaCN) or sunflower oil droplets emulsified with WP or NaCN as the emulsifier protein were prepared in 0 or 50mM NaCl. The WP gel structure strengthened in the presence of added NaCl and NaCN. The rheological properties of WP gels containing sunflower oil droplets emulsified with WP or NaCN were influenced by the NaCl concentration, oil concentration and extent of oil droplet aggregation in the gel or by the type of emulsifier protein used. During tensile testing, the notch length in all gels increased above a certain critical stress, leading to fracture of the gels through the notch. Also, the microstructural changes in the oil phase of emulsion filled gels subjected to tensile testing were influenced by the structural properties of the WP gel matrix and the proximity of the oil droplet to the fracture path. [ABSTRACT FROM AUTHOR]