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This paper investigates the binding behavior of iso-α-acids from hops on free wort amino acids and proteins concerning the wort production process in breweries. The studies were carried out with different amino acids, bovine serum albumin and wort. To identify the nature of reaction between iso-α-acids and these substances, analyses of free amino nitrogen, HPLC and isothermal titration calorimetry were performed. According to the results, the iso-α-acids do not form covalent bonds with free amino acids of wort. However, iso-α-acids, especially isohumulone and isoadhumulone, form ionic bonds with wort proteins. A distinction must be made between proteins that are present in the hot trub, and those that are still dissolved in the hot wort. Proteins that are already coagulated and precipitated no longer react with iso-α-acids. Future experiments will investigate whether the established ionic bonds between iso-α-acids and proteins from the wort preparation process are maintained during fermentation until the finished beer or beer foam. If this is the case, which is induced by the experiments, there is a measurable loss of iso-α-acids in the hot wort, but at the same time, a gain for the later beer foam retention, as the iso-α-acids will stabilize it.

Engineered fibril solutions from whey protein beta-lactoglobulin are known for their excellent foaming capacity. These amyloid aggregates solutions (AAS) usually contain a polydisperse mixture of different protein structures. An optimized ratio of amyloid (AF, fibrils) and non-amyloid fractions (n-AF) in AAS may improve foaming, particularly by interactions at the air-water interface. Foamability, surface activity, and monolayer phase behavior at the air-water interface of isolated AF and n-AF as well as AAS with different AF/n-AF-ratios were investigated using drop tensiometry, Langmuir trough and foam analysis. N-AF exhibited faster migration, twice as fast adsorption and thus faster spreading at the air-water interface than the fibrils (AF). N-AF required less energy to assemble in a liquid-expanded phase in a monolayer, i.e., they were more compressible in the monolayer than AF. This resulted in rapid stabilization of lamellae in foam. High surface hydrophobicity of AF results in faster adsorption and formation of capillary forces between adsorbed fibrils, improving the attraction for additional fibrils. Orientation of semi-flexible and larger fibrils in AF consumes high energy. In combination with n-AF, the energy needed for orientation and assembly of fibrils is equivalent, however, the yield of AF in AAS was only 20 %, indicating the interplay of amyloid and non-amyloid proteins at the air-water interface. N-AF can be incorporated into a fibrillar film, which increase the network's density and stiffness and the interfacial film stability. Consequently, in AAS fibrils and non-amyloid material acted synergistically at the air-water interface, whereby only small amounts of amyloid aggregates are required to stabilize foams.

Encapsulation of food and feed ingredients is commonly applied to avoid the loss of functionality of bioactive food ingredients. Components that are encapsulated are usually sensitive to light, pH, oxygen or highly volatile. Also, encapsulation is also applied for ingredients that might influence taste. Many polymers from natural sources have been tested for encapsulation of foods. In the past few years, pectins have been proposed as emerging broadly applicable encapsulation materials. The reasons are that pectins are versatile and inexpensive, can be tailored to meet specific demands and provide health benefits. Emerging new insight into the chemical structure and related health benefits of pectins opens new avenues to use pectins in food and feed. To provide insight into their application potential, we review the current knowledge on the structural features of different pectins, their production and tailoring process for use in microencapsulation and gelation, and the impact of the pectin structure on health benefits and release properties in the gut, as well as processing technologies for pectin-based encapsulation systems with tailor-made functionalities. This is reviewed in view of application of pectins for microencapsulation of different sensitive food components. Although some critical factors such as tuning of controlled release of cargo in the intestine and the impact of the pectin production process on the molecular structure of pectin still need more study, current insight is that pectins provide many advantages for encapsulation of bioactive food and feed ingredients and are cost-effective.

Food researchers are currently showing a growing interest in in vitro digestibility studies due to their importance for obtaining food products with health benefits and ensuring a balanced nutrient intake. Various bioactive food compounds are sensitive to the digestion process, which results in a lower bioavailability in the gut. The main objective of structured food delivery systems is to promote the controlled release of these compounds at the desired time/place, in addition to protecting them during digestion processes. This review provides an overview of the influence of structured delivery systems on the in vitro digestive behavior. The main delivery systems are summarized, the pros and cons of different structures are outlined, and examples of several studies that optimized the use of these structured systems are provided. In addition, we have reviewed the use of plant-based systems, which have been of interest to food researchers and the food industry because of their health benefits, improved sustainability as well as being an alternative for vegetarian, vegan and consumers suffering from food allergies. In this context, the review provides new insights and comprehensive knowledge regarding the influence of plant-based structured systems on the digestibility of encapsulated compounds and proteins/polysaccharides used in the encapsulation process.

Proteins are able to stabilize dispersed food systems due to their amphiphilic nature, acting as emulsifiers. Their interfacial properties can be influenced by different methods, including the formation of protein-phenol nanocomplexes. In this study, the interfacial behavior of phenolic compounds and protein-phenol nanocomplexes was first characterized according to the oil-water partitioning behavior of phenolic acid derivatives according to their molecular structure and its impact on interfacial tension. The influence of the phenolic compounds on protein film formation and its properties by dilatational rheology was then evaluated. The most phenolic acid derivatives are predominantly present in the aqueous phase. Despite their hydrophobic benzene body, weak interfacial activity was observed depending on their chemical structure. This result supports possible protein-phenol nanocomplex formation in the aqueous phase and possible interactions at the oil-water interface. Protein-phenol nanocomplexes showed decreased interfacial adsorption properties and decreased viscoelastic interfacial behavior, depending on the expansion of the delocalized π-electrons in the phenol.

In spray dried emulsions, frequently milk proteins are used as interfacial active components and starch conversion products are added as matrix material at high concentrations. To characterize interfacial properties at the oil/water interface by commonly applied methods, low protein, and carbohydrate concentrations from 1 to 2% are usually analyzed. The impact of a higher concentration of starch conversion products was not investigated so far. Therefore, the formation and rheological properties of β-lactoglobulin (β-LG) stabilized films at the oil/water interface were investigated via short and long-time adsorption behavior using pendant drop tensiometry as well as dilatational and interfacial shear rheology. Suitability of the applied methods to the chosen samples with higher concentrations >1–2% was verified by calculation of selected key numbers like capillary number and by detailed reviewing of the results which is summarized further on as key indicators. It is hypothesized, that the increase in concentration via presence of starch conversion products will delay interfacial stabilization as a result of increased bulk viscosity with decreasing degree of degradation (dextrose equivalent) of the starch. Furthermore, this increase in concentration leads to more stable interfacial films due to thermodynamic incompatibility effects between protein and starch conversion products which results in increases of local protein concentration. Key indicators proved a general suitability of applied methods for the evaluation of the investigated samples. Moreover, results showed an increase in interfacial film stability and elastic properties alongside a decreased interfacial tension if starch conversion products were present in a high concentration.

Hops are an essential raw material for beer production in the brewery. The hop constituents give the beer its bitter taste, additional aroma, and can make it more stable. As hops are a cost-intensi...

The physical stability of protein-based emulsions depends on intra- and intermolecular interactions of the interfacial protein-film. As studied in aqueous systems before, phenolic acid derivatives (PADs) non-covalently or covalently crosslink proteins depending on pH-value and thus, may impact interfacial protein-films. Whether these interactions occur in the same manner at the interface as in water and how they vary the properties of the interfacial protein-film has not been clarified. The present study aimed to investigate the interfacial protein-film viscoelasticity and physical emulsion-stability after non-covalently (pH 6.0) and covalently (pH 9.0) crosslinking depending on PAD-structure. For this purpose, we studied an interfacial β-lactoglobulin film with dilatational rheology after crosslinking with PADs, varying in number of π-electrons and polar substituents. Then, we analyzed the physical emulsion-stability by visual evaluation and particle size distribution. The results indicate that PADs with a high number of π-electrons (rosmarinic acid and chicoric acid) weaken the protein-film due to competing of phenol-protein interactions with protein-protein interactions. This is reflected in a decrease in interfacial elasticity. PADs with an additional polar substituent (verbascoside and cynarine) seem to further weaken the protein film, since the affinity of the PADs to the interface increases, PADs preferentially adsorb and sterically hinder protein-protein interactions. In emulsions at pH 6.0 and thus low electrostatic repulsion, PADs promote bridging-flocculation. Due to higher electrostatic repulsion at pH 9.0, the PADs are sterically hindered to form bridges, even though they are polymeric. Hence, our research enables the control of protein-film viscoelasticity and emulsion-stability depending on the PAD-structure. Graphical abstract

Oil in water emulsions are commonly stabilized by emulsifying constituents like proteins and/or low molecular weight emulsifiers. The emulsifying constituents can compete or coexist at the interface. Interfacial properties thus depend on molecular structure of the emulsifying constituents and the oil phase and the resulting molecular interactions. The present study systematically analyzed the impact of fatty acid saturation of triacylglycerides and phosphatidylcholine on the interfacial properties of a β-lactoglobulin-stabilized interface. The long-term adsorption behaviour and the viscoelasticity of β-lactoglobulin-films were analyzed with or without addition of phosphatidylcholine via drop tensiometry and dilatational rheology. Results from the present study showed that increasing similarity in fatty acid saturation and thus interaction of phosphatidylcholine and oil phase increased the interfacial tension for the phosphatidylcholine alone or in combination with β-lactoglobulin. The characteristics and stability of interfacial films with β-lactoglobulin-phosphatidylcholine are further affected by interfacial adsorption during changes in interfacial area and crystallization events of low molecular weight emulsifiers. This knowledge gives guidance for improving physical stability of protein-based emulsions in foods and related areas. Graphic abstract

Complex coacervation is an encapsulation process involving two oppositely charged biopolymers. Since different compositions of gum arabic may affect its interaction with protein, we studied the complex coacervation of two types of gum arabic (GA) (Acacia senegal-GA1 and Acacia seyal-GA2) with soluble pea protein (SPP) through Zeta potential, turbidity, morphology, the secondary structure of SPP, UV/vis absorbance and thermodynamic parameters. The maximum formation of coacervates occurred at SPP:GA 3:1 (w/w) and pH 3.5-4.0 with changes in the secondary structure of SPP. GA1 combination resulted in higher binding constant, implying a stronger affinity between SPP and GA1. Entropy of 0.7 and 0.5 kJ/mol.K, and enthalpy of -151 and -95.5 kJ/mol were obtained for SPP:GA1 and SPP:GA2. The complex coacervation was spontaneous as proved by the negative values of the Gibbs free energy. GA1 resulted in stronger interactions with SPP, offering new alternatives for encapsulation of bioactive compounds.

Past investigations have shown high browning potential during the caramelization of sugar acids in comparison to reducing sugars. However, no approaches to elucidate the chemical mechanisms have been made. Therefore, this study aims to clarify the reasons for the high browning potential by measuring the mutarotation velocity and the elimination of CO2 during the heat treatment of uronic acids. Performed polarimetric experiments show that the mutarotation velocity of d-galacturonic acid exceeds that of d-galactose by a factor of nearly 4.5. However, the ring opening velocity is not the only parameter that differs between the two carbohydrate structures. Measurements of the release of CO2 of heated d-galacturonic acid at 60 °C show a steady increase, and after 48 h, 6% of degraded d-galacturonic acid has eliminated CO2. CO2 release was also found during the heating of pectin, indicating a decarboxylation reaction during thermal degradation. One of the degradation reactions postulated for the release of CO2 leads to α-ketoglutaraldehyde, which is responsible for the formation of several chromophoric substances.

The goal of this study was to investigate the influence of the emulsifier system on the changes in oil droplet size occurring during the drying step of spray drying of emulsions. Atomization and spray drying experiments were performed with emulsions stabilized with whey protein isolate (WPI) alone or in combination with low molecular weight emulsifiers (lecithin, mono- and diglycerides (MoDi), and citrem). Oil droplet coalescence was observed for the systems WPI/Citrem and WPI/MoDi, as the d90,0 increased from 0.86 ± 0.16 and 1.67 ± 0.35 µm after atomization to 1.83 ± 0.24 and 1.90 ± 0.17 µm after drying, respectively. Oil droplets stabilized with WPI or WPI/Lecithin remained stable during drying. Measurements of dilatational rheology of the interfacial film showed that phase angle values increase in the order WPI/Lecithin < WPI < WPI/Citrem = WPI/MoDi. Therefore, in the studied system oil droplet coalescence during drying increases when the elastic behavior of the interfacial film decreases.

Nutritional recommendations for the elderly, but also the general public, include incorporation of plant proteins in the diet, an increase in the intake of Ω-3 fatty acids and an increase in intake of dietary fibre. Protein structure and structuring behaviour of plant proteins differ from that of milk proteins. Therefore, the aim of the presented study was to characterise the structuring process and resulting structure of yoghurt-style gels containing 10% pea protein with and without addition of nutritionally recommended ingredients like rapeseed-oil and/or commercial oat fibre. Rheological measurements were combined with microscopy for sample characterisation. Generally, all studied formulations were able to form acid induced gels via fermentation. The acidification led to a two-phase gelation process resulting in thick gels that showed mainly weak rheological behaviour. Supplementation with oil and/or fibre resulted in an increase of the relative concentration of pea protein in the aqueous phase and led to a strong increase in the complex shear modulus |G*| as well as the maximum structuring velocity d|G*|/dt. These effects need to be considered when tailoring yoghurt-style gels with high consumer acceptance.

Dietary fibre yields an additional benefit in terms of stabilisation of food structure or nutritional value, but may alter sensory properties in fibre-enriched foods. This study aims to investigate the impact of pectin-rich orange fibre on rheological, sensory and tribological properties of yoghurt gels. More specifically, the effect of the fibre particle size (coarse and fine) and fibre concentration (0.1 and 1.0%) is evaluated. Both, coarse and fine fibre accelerate structure formation during lactic acid fermentation. At low concentration fibre-enriched yoghurts exhibit rheological properties similar to the plain yoghurt and syneresis is decreased. At high concentration coarse fibre considerably reduces gel firmness whereas fine fibre additionally stabilises the casein network as a filler. This stabilising effect might be favoured by pectin, which leaches from orange fibre during mechanical and thermal pre-treatment and subsequently supports the bridging of casein micelles due to its calcium sensitivity. Depending on the criteria for classification of gels, fibre-enriched yoghurts show either strong or weak gel properties. Fibre addition causes alterations in sensory perception. A slight decrease in overall acceptance compared to the plain yoghurt is mainly related to a more compact texture and an increased particulate mouthfeel. Tribological data reveal that increased friction is mainly related to a reduced ability of coarse fibre yoghurt to immobilise water at high strain and that the protein (casein) network dominates lubrication properties in plain yoghurt.

Aim of the present study was to investigate the impact of different demethoxylation methods and the co-occuring side effects on the molecular properties and structure formation in pectin gels. A high-methoxylated citrus pectin (HMP) was demethoxylated using either hydrochloric acid or pectin methylesterases of plant (pPME) or fungal (fPME) origin. pPME treatment causes a more block-wise distribution of free carboxyl groups, fPME or acidic treatment a random distribution. Twelve pectin samples with four different degrees of methoxylation (DM) between 62% and 41% were prepared. The gelation process was studied by oscillatory measurements. In pectin samples from pPME treatment structure formation started at higher temperature and the final gels were more elastic in comparison to pectin from the two other modifications. The impact of the block-wise distribution of the free carboxyl groups became more evident with decreasing DM. The gelling process of pectin samples with random distribution was similar independent of DM.Side effects of all demethoxylation reactions were an altered sodium ion content (high in enzymatically treated pectin, close to zero in acidic treated) and a decrease of the molecular weight with increasing degree of demethoxylation. These side effects additionally altered the gelation process and the final gel properties in different ways.

Mechanical and thermal processings may affect the composition and the techno-functional properties of dietary fibre as a part of a complex food system. The aim of this study was to investigate the impact of a mechanical and thermal treatment alone or in combination on alcohol insoluble substance (AIS), the content of galacturonic acid (GalA), the water retention capacity (WRC) and the microstructure by scanning electron microscopy (SEM). Two samples of orange fibre with different particle size (coarse and fine) were investigated in an experimental design and evaluated with regard to particle size (d50) after treatment and their impact on network formation. Our study highlights a more pronounced susceptibility of the coarse fibre towards mechanical stress compared to the fine fibre with regard to particle size reduction. High-pressure homogenization (HPH) represents the crucial step regarding AIS release and the increase of WRC for both fibres. A mechanical treatment with additional thermal treatment maximises AIS release. GalA, as a marker for pectin in AIS, was detected in various amounts depending on the intensity of the treatment. Highest values for WRC were achieved for the coarse fibre as a consequence of both, particle size reduction and the formation of a stable network on a microstructural level.

High shear rheometry was used to investigate the rheological behavior of high internal phase emulsions (HIPEs) stabilized by whey protein isolate (WPI). The physical stability of HIPEs was tested at extremely high shear rates generated by decreasing the gap height between parallel plates. Viscosity and yield stress, at narrow gaps, increased with protein concentration due to tighter packing of smaller droplets. Structural breakdown and recovery of HIPEs were affected by protein concentration and pH. The hysteresis behavior of HIPEs was either thixotropic or anti-thixotropic and was determined by protein concentration, whereas pH affected the magnitude of anti-thixotropy. At pH 3, emulsions showed greater stability against extreme shear and creaming due to higher deformability of oil droplets and increased interdroplet interaction compared to neutral pH. Challenging the physical integrity of concentrated emulsions under high shear is an effective way to characterize microstructural changes and stability of HIPEs in foods.

In spray-dried emulsions a wide range of emulsifying constituents including proteins and low molecular weight emulsifiers are used. Due to their different behaviour, combinations of different emulsifying constituents are common, whereupon their interactions may also adversely affect powder properties and stability. Therefore, the impact of whey protein isolate alone or in combination with lecithin, mono-/diglyceride and citrem as low molecular weight emulsifiers on powder characteristics and storage stability were investigated. Temperature stresses were applied to induce instability phenomena. A specific combination of protein and low molecular weight emulsifiers resulted in a reduction in oil droplet size while maintaining encapsulation efficiency. Induction of crystallisation through low temperature stress induced oil release in samples, in which templating for heterogeneous nucleation took place. High temperature stress caused Maillard reaction, protein-fat complexation and phase transition of the matrix resulting in colour changes and reduction of extractable oil.

Organic zinc sources for the treatment of zinc deficiency or as a supplement to a specific diet are increasingly needed. Zinc-enriched yeast (ZnYeast) biomass is a promising nutritional supplement for this essential micronutrient. However, these products are not yet authorized in the European Union and a clear position from the European Food Safety Authority on the use of ZnYeast as a zinc supplement is pending, demanding more data on its bioavailability.The study aimed to produce a ZnYeast based on a Saccharomyces genus (S. pastorianus Rh), characterize its zinc enrichment quota, cellular distribution of zinc, and evaluate its zinc bioavailability after human digestion by comparing it to commonly used inorganic and organic zinc supplements (ZnO, ZnSOThe zinc-enriched S. pastorianus Rh contained 5.9 ± 1.0 mg zinc/g yeast, which was predominantly localized on the cell surface according to its characterization on the microscale with scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX). Combined experiments with a human in vitro digestion model and the in vitro intestinal cell model Caco-2 showed that intestinal zinc bioavailability of digested yeast biomass was comparable to the other zinc supplements, apart from ZnO, which was somewhat less bioavailable. Moreover, zinc released from digested ZnYeast was available for biological processes within the enterocytes, leading to mRNA upregulation of metallothionein, a biomarker of intestinal zinc status, and significantly elevated the cellular labile zinc pool.Our findings demonstrated that ZnYeast represents a suitable nutritional source for organically bound zinc and highlighted optimization strategies for future production of dietary ZnYeast.

Food hydrocolloids 110, 106132 (2021). doi:10.1016/j.foodhyd.2020.106132, Published by Elsevier, Amsterdam

The mechanical stability of protein-stabilized emulsions depends on physiochemical interactions within the interfacial protein film. However, intermolecular interactions vary with the protein's conformational state and charge and may in turn affect the mechanical stability through modifications in the three-staged interfacial stabilization; migration, adsorption and film formation at the oil/water-interface. Therefore, the aim of our study was to investigate the different protein conformations within the interfacial stabilization process by applying bulk water conditions and to determine the protein film stability against mechanical stress. For this purpose, we analyzed the structure and interactions of β-lactoglobulin in water and at the oil/water-interface at pH 7, pH 7NaCl (containing 100 mM NaCl) and pH 9 with membrane-osmometry, Fourier-transform-infrared-spectroscopy, extrinsic fluorescence and ζ-potential. Moreover, we characterized the conformational state and charge in context with the molecule density and interfacial film properties via Langmuir trough analysis, interfacial shear and dilatational rheology. Distinct unfolding of monomers and dimers at pH 9 resulted in the lowest interfacial molecule density but at the same time the highest film stability due to pronounced structural flexibility. In comparison, β-lactoglobulin at pH 7 was monomeric, unfolding was less pronounced, and interfacial molecule density was higher. Electrostatic shielding of β-lactoglobulin dimers at pH 7NaCl resulted in the highest density but least stable protein film that approached low molecular weight surfactant behavior due to few and weak intermolecular interactions. Our research contributes to the control of the emulsion stability against mechanical stress by varying intermolecular interactions within the interfacial protein film.

The mechanical stability of interfacial protein films is limited through the intermolecular interaction of the adsorbed proteins. Since the intermolecular interactions vary in dependence of the protein structure, the investigation of intentionally induced structural modifications (i.e., through high hydrostatic pressure) of interfacial active proteins is required to mechanistically understand their structure-function-relationship. The aim of this study was to link the structural analysis of pressure-treated whey protein β-lactoglobulin at the oil/water-interface with the formation of the interfacial protein film and the resulting film stability against mechanical stress. For this purpose, we treated β-lactoglobulin in water at pH 7 with hydrostatic pressures of 600 MPa for 10 min at 20 °C and analyzed the protein structure in oil/water-emulsion with Fourier-transform-infrared-spectroscopy, extrinsic fluorescence, and ζ-potential. We characterized the molecular density and interfacial film properties via Langmuir trough analysis, electron-paramagnetic-resonance-spectroscopy, interfacial shear and dilatational rheology. The structural flexibility of pressure-treated β-lactoglobulin favored its unfolding and a fast interfacial protein film formation that resulted in pronounced intermolecular interactions, including van der Waals interactions, hydrophobic associations and disulfide bonds. The high interfacial molecule density combined with many and strong intermolecular interactions stabilized the pressure-treated protein film against shear deformation and small dilatational deformation. However, against high dilatational deformation, the pressure-treated β-lactoglobulin film showed a lower stability due to a slow migration towards unoccupied interfacial area. Hence, our research contributes to the control of the mechanical protein film stability, and thus the colloidal stability of emulsions in dependence of the protein structure at the oil/water-interface.

Hypothesis High hydrostatic pressure treatment causes structural changes in interfacial-active β-lactoglobulin (β-lg). We hypothesized that the pressure-induced structural changes affect the intra- and intermolecular interactions which determine the interfacial activity of β-lg. The conducted experimental and numerical investigations could contribute to the mechanistic understanding of the adsorption behavior of proteins in food-related emulsions. Experiments We treated β-lg in water at pH 7 with high hydrostatic pressures up to 600 MPa for 10 min at 20 °C. The secondary structure was characterized with Fourier-transform infrared spectroscopy (FTIR) and circular dichroism (CD), the surface hydrophobicity and charge with fluorescence-spectroscopy and ζ-potential, and the quaternary structure with membrane-osmometry, analytical ultracentrifugation (AUC) and mass spectrometry (MS). Experimental analyses were supported through molecular dynamic (MD) simulations. The adsorption behavior was investigated with pendant drop analysis. Findings MD simulation revealed a pressure-induced molten globule state of β-lg, confirmed by an unfolding of β-sheets with FTIR, a stabilization of α-helices with CD and loss in tertiary structure induced by an increase in surface hydrophobicity. Membrane-osmometry, AUC and MS indicated the formation of non-covalently linked dimers that migrated slower through the water phase, adsorbed more quickly due to hydrophobic interactions with the oil, and lowered the interfacial tension more strongly than reference β-lg.

Yoghurt style gels are a promising way to increase the consumption of plant derived proteins. However, reaching texture properties similar to those commonly known from milk yoghurts while incorporating large amounts of plant-derived proteins, is a challenge that needs to be addressed to meet consumers expectations. Therefore, this study aims to investigate the influence of pH conditions (pH 6.0 to pH 8.0) during pre-treatment on the rheological properties of fermentation induced pea protein gels with a protein content of 10%. Results showed a strong correlation between the pH value during pre-treatment and the protein solubility after pH readjustment to pH 8. Solubility was highest if pea protein was pre-treated at pH 8.0 and lowest if it was pre-treated at pH 6.0. Since only soluble aggregates are believed to participate in network formation, networks formed by pea protein pre-treated at pH 6 were coarser, than those formed by pea protein pre-treated at pH 8 owing to a lower degree of crosslinking caused by less available protein. Coarser networks and higher proportions of insoluble particles increased loss of water and lowered the storage modulus G’ as well as the ability of the networks to recover after intense shearing. In particular pre-treatment at pH values below 7.0 led to gels with storage moduli of the same magnitude as those measured in commercial milk derived yoghurts. Adjusting the pH value during pre-treatment of pea protein can therefore be considered a promising approach for the customisation of texture properties while maintaining a constantly high protein content.

Made available in DSpace on 2020-12-10T20:02:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-10-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The aim of the present study was to investigate the impact of chickpea protein (CP) alone or in the form of sequentially adsorbed chickpea protein and high methoxylated pectin (CP-HMP) on the microencapsulation of buriti oil by spray drying. CP was extracted and characterized by its molecular weight distribution, zeta potential and solubility. The adsorption of CP and CP-HMP complexes to the oil/water (O/W) interface was investigated by measurement of the interfacial tension. The interactions between the molecules at the O/W interface were analyzed by interfacial shear rheology. Emulsions containing CP or CP-HMP were prepared at pH 3.5, homogenized and spray dried at 180/70 degrees C and 210/90 degrees C (inlet/outlet) temperature. The oil droplet size distribution (ODS) of emulsions before and after spray drying, the encapsulation efficiency (EE) of microcapsules and their oxidative stability were evaluated. The interfacial tension of CP at the O/W interface was not affected by pectin addition. However, interfacial shear rheology revealed strong interactions between CP-HMP complexes, maintaining the physical integrity of emulsion oil droplets during spray drying. On the other hand, interactions in the CP film were weaker and the droplets were affected by spray drying, suffering from an increase in size. The EE of CP-HMP microcapsules was higher than for CP microcapsules, which suggests a synergistic effect. The spray drying temperature had no effect on the EE. During 6 months of storage, a slight increase of the conjugated dienes content was observed for all microcapsules. However, the type of microcapsule and the temperature of spray drying had no effect on the development of lipid oxidation. Sao Paulo State Univ, Inst Biosci Humanities & Exact Sci, Dept Food Engn & Technol, Cristovao Colombo 2265, BR-15054000 Sao Jose Do Rio Preto, Brazil Tech Univ Berlin, Inst Food Technol & Food Chem, Dept Food Technol & Food Mat Sci, Berlin, Germany Sao Paulo State Univ, Inst Biosci Humanities & Exact Sci, Dept Food Engn & Technol, Cristovao Colombo 2265, BR-15054000 Sao Jose Do Rio Preto, Brazil FAPESP: 2017/05107-9 FAPESP: 2016/06204-5 FAPESP: 2014/02910-7

In the light of changing nutritional trends and recommendations, yoghurt style gels from plant proteins are a promising way to incorporate relevant amounts of plant derived proteins into the diet. However, in order to attain a high level of consumer acceptance, a thorough understanding of rheological behaviour, involved protein fractions and relevant interactions is mandatory in order to later be able to customise properties of fermentation induced gels. Therefore, the aim of this study was to first characterise the type of dominating interactions within the gel network and the protein fractions involved followed by determination of the rheological properties of gels made from pea protein and pea protein hydrolysates. Results showed that the protein-protein interactions were mainly hydrophobic in nature and involved mostly the legumin fraction. A smaller contribution could be ascribed to electrostatic interactions between vicilin and the basic legumin-β chain, thus incorporating some vicilin into the gel. The interaction between vicilin and the basic legumin-β chain was influenced by modification of the molecular weight distribution via enzymatic hydrolysis. Especially hydrolysis with trypsin led to an enhanced involvement of vicilin in the gel structure due to the increased availability of legumin-β. The molecular weight distribution only had a minor impact on the rheological properties of the fermentation induced pea protein gels leading to the conclusion that in rheology the type of interactions is more important, than the protein fractions involved.

Sensory perception of food is very important when it comes to consumer acceptance. The sensory impression in the oral cavity plays a key role. Especially the haptic properties are dominated by friction when the food is strained between the tongue and the palate. Tribology enables friction measurements by determining the coefficient of friction as the ratio between friction force and normal force. The aim of this study was to develop a method for tribological measurement of food within a simulated tongue-palate contact using varying surface combinations (tribopairs) in a rheometer set-up. The impact of surface handling and sampling procedures on the coefficient of friction was investigated in order to establish suitable conditions for the tribological characterisation of food samples with varying composition. Tribological measurements were carried out in a rheometer equipped with a tribology module. Additionally, the characterisation of the used counter and ground surfaces was conducted by AFM and SEM analyses. The reliability and reproducibility of the developed method is highly affected by the handling of the surfaces and the sampling of the foods, passing the run-in-period and the number of compressions between ground and counter surface. A tribopair consisting of a glass sphere on PDMS pins demonstrates the best usability with respect to low standard deviation, good reproducibility and distinct differentiation of all four sections of the Stribeck curve. The content of water in food systems has a substantial influence on these parameters, which is related to varying adhesive effects of the respective tribopair.

The efficacy of cold-set binding systems on the network formation and rheological structuring mechanisms of restructured meat depends on the binding system, time and temperature of cold setting, and the presence of NaCl. Therefore, the structure formation during the binding process using transglutaminase (TG), Ca-alginate (AL) or glucono-δ-lactone (GdL) for 20 h at 4 °C with or without added NaCl was investigated. The dynamic oscillation rheology, water binding capacity, firmness and microscopic structure of the resulting meat gels were studied. The results showed that cold-set binding systems significantly affect the pH, water binding capacity and the textural properties of the resulting gels. The main process of gel setting took place within the first 1.5 h without the use of salt. Adding salt to the matrix shortened this period to 1 h. The pH of the resulting gels was only influenced by GDL, which caused a decrease from pH 5.48 to 4.90 when applied to the meat batter alone. AL gels showed a soft and semi solid-like behavior with a spreadable texture, TG provided with increased solid-like viscoelastic behavior and a coherent structure, and GdL resulted in an unstable aggregation and an incoherent structure between the meat particles. The water binding capacity was highest in AL gels (86.1%), followed by TG (72.6%). GDL had no effect on the water binding capacity (63.3%), which was strongest influenced by the addition of NaCl to the meat batter (99.9%). The later minimized most of the differences between the binding systems, demonstrating a greater impact on the matrix than the pure binding systems. Furthermore, the AL has to be added as a pre-formed gel to the meat batter to aid gel formation in the presence of NaCl.

For different reasons, there is an increasing interest in plant-based foods as well as vegetarian and vegan dairy and meat alternatives. Frequently, those foods represent dispersed systems and more specifically food emulsions with proteins as emulsifying food ingredients. Owing to a very heterogeneous composition of plant proteins and a wide range of structural varieties in the proteins, it is worth discussing if our current understanding of interfacial and emulsifying properties of proteins is sufficient to meet the challenges associated with the utilisation of plant proteins for the stabilisation of food emulsions. To this purpose, we review the current understanding of the interfacial behaviour of proteins, summarise analytical techniques for their characterisation and critically discuss the available literature on oilseed and legume proteins to identify future research needs and opportunities for customised emulsion design.

Clouds represent oil-in-water emulsions, which are used to create a turbid appearance in beverage emulsions. Aim of the present study was to investigate whether crystalline structures at the oil-water interface or a solidified dispersed phase sufficiently increase the refractive index difference between the two phases to create turbidity in a more efficient manner. Bulk materials and dispersions were characterized by differential scanning calorimetry and time-domain-NMR for crystal structure and solid fat content, respectively. Use of high melting emulsifiers (HME), 1% sodium stearoyl lactylate (SSL), 1% glyceryl stearoyl citrate (GSC), respectively 1.5% phospholipid (PL) did not result in an increase in turbidity. Data indicate that the emulsifiers did not crystallize at the interface. However, modification of the dispersed phase with high melting lipids (HML) was successful. Using fats with increasing melting point, it was shown that turbidity increased with increasing degree of crystallinity. Compared to a liquid medium chain triglyceride (MCT) turbidity increased significantly from 290 NTU (ratio) using hydrogenated palm fat (HPF, 400 NTU (ratio)) or tristearin (SSS, 440 NTU (ratio)) instead. In order to induce that effect, a critical degree of crystallinity of more than 36% needed to be achieved.

The interfacial properties of dairy proteins are of great interest to the food industry. Food manufacturing involves various environmental conditions and multiple processes that significantly alter the structure and colloidal stability of food materials. The effects of concentration, pH, heat treatment, addition of salts etc., have considerable influence on the surface activity of proteins and the mechanical properties of the interfacial protein films. Studies to date have established some understanding of the links between environmental and processing related parameters and their impacts on interfacial behavior. Improvement in knowledge may allow better design of interfacial protein structures for different food applications. This review examines the effects of environmental and processing conditions on the interfacial properties of dairy proteins with emphasis on interfacial tension dynamics, dilatational and surface shear rheological properties. The most commonly used surface analytical techniques along with relevant methods are also addressed.

In order to critically discuss the potential of Pickering-type emulsions in food applications this review provides the theoretical background of the stabilizing mechanisms, the resulting requirements for particles to stabilize these systems and the limitations resulting from these fundamental considerations. Food grade particle systems investigated in the past are presented. It becomes obvious that with a proper choice of a particle type, oil-in-water as well as water-in-oil emulsions can be achieved. For highly viscous products, products with a high internal phase volume and foams Pickering particles offer alternatives to commonly used surfactants. Pickering emulsions might be able to offer new approaches for fat reduction as well as encapsulation and sustained release of active ingredients. Nevertheless, a major part of successful systems have been achieved with silica or modified silica particles, which is not in line with the consumer demand for clean label, natural systems or not even food grade. However, the intriguing possibilities motivate and justify future research on the identification of new suitable ingredients, improvement of existing formulations and identification of new fields of application.