Foaming characteristics of oat protein and modification by partial hydrolysis

Foaming ability of oat protein isolate (OPI) was analysed at pH 4 and 7. Foaming properties were influenced by partial hydrolysis with trypsin (OPT) and alcalase (OPA). The viscoelasticity of the protein film, the interactions between the protein molecules, and the network forming within the protein film were analysed by interfacial rheology. At pH 7, foams made of OPI and OPT were found to be stable with OPI showing the fastest foaming ability. At pH 4, the foaming properties of OPI were found to be poor due to limited solubility. The specific cleavage pattern of trypsin resulted in peptides with improved foaming properties, especially at pH 4, resulting in a homogenous foam structure, a fast foaming ability, and a highly viscoelastic interfacial film. The formation of a thick steric protein layer at pH 7 and the formation of strong hydrophobic interactions at pH 4 were found to be the dominating foam stabilisation mechanisms. In conclusion, oat protein may serve as a food ingredient with targeted functional properties

Spray drying of emulsions: Influence of the emulsifier system on changes in oil droplet size during the drying step

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 d$_{90,0}$ 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

Einfluss der komplexen Wechselwirkungen von Formulierungsbestandteilen auf die Stabilität sprühgetrockneter Emulsionen

Spray dried emulsions like infant formulae or coffee creamer are commonly applied systems in the food industry. The formulation of spray dried emulsions consists of a matrix material like starch conversion products, an oil phase, and emulsifying constituents like proteins and low molecular weight emulsifiers. These emulsions are transferred into powder form via emulsification, atomization and a drying step to maintain a high stability of these products over a long storage period. The stability of spray dried emulsions is affected by processing and formulation. The formulation components guide the stability during each processing step in the liquid state before powder transformation or during the storage of powders. The former case is determined by the performance of emulsifying constituents, as the latter case is determined by all formulation components. The performance of emulsifying constituents during processing steps in the liquid state is linked to their interfacial behaviour. The physicochemical mechanisms during storage are based on phase transition behaviour of the oil phase beside other phenomena. Both cases are further influenced by the complex interplay of formulation components. This interrelation was investigated in detail. The results indicate that the performance of emulsifying constituents changes due to the complex interplay of formulation components at interface, in water and oil phase. The altered performance of emulsifying constituents affects the stability of spray dried emulsions in oil droplet size and encapsulation efficiency during processing steps in the liquid state. The physicochemical mechanisms, however, are influenced by complex interactions of low molecular weight emulsifiers and oil phase. Spray dried emulsions were destabilized by crystallized low molecular weight emulsifiers at the o/w interface, releasing encapsulated oil. Since all described effects strongly depend on the molecular structure of formulation components, a tailored variation in formulation components may increase the stability of spray dried emulsions.Sprühgetrocknete Emulsionen wie bspw. Säuglingsanfangsnahrung oder Kaffeeweißer sind häufig verwendete Systeme in der Lebensmittelindustrie. Die Formulierung der sprühgetrockneten Emulsionen besteht meist aus einem Matrixmaterial aus Stärkeabbauprodukten, einer Öl-Phase und aus emulgierenden Bestandteilen wie Proteinen und niedermolekularen Emulgatoren. Diese Emulsionen werden mittels Emulgierung, Zerstäubung und dem Trocknungsvorgang in die Pulverform überführt, um eine hohe Stabilität der Produkte über einen langen Lagerzeitraum zu ermöglichen. Die Stabilität der sprühgetrockneten Emulsionen wird durch Prozess und Formulierung beeinflusst. Die Formulierungsbestandteile lenken die Stabilität während aller Prozessschritte im flüssigen Zustand vor dem Übergang in die Pulverform oder während der Lagerung der Pulver. Der erstere Fall wird vom Verhalten der emulgierenden Bestandteile bestimmt wobei im letzteren Fall alle Formulierungsbestandteile einen Einfluss haben. Das Verhalten der emulgierenden Bestandteile steht im Zusammenhang zu ihrem Grenzflächenverhalten. Die physikochemischen Mechanismen während der Lagerung basieren neben anderen Effekten auf dem Phasenübergangsverhalten der Öl-Phase. Beide Fälle werden durch die komplexen Wechselwirkungen der Formulierungsbestandteile beeinflusst. Dieser Zusammenhang wurde im Detail untersucht. Die Ergebnisse zeigen, dass das Verhalten der emulgierenden Bestandteile durch die komplexen Wechselwirkungen der Formulierungsbestandteile an der Grenzfläche, in der wässrigen und Öl-Phase verändert wird. So beeinflusst das veränderte Verhalten der emulgierenden Bestandteile die Stabilität der sprühgetrockneten Emulsionen in Öltropfengröße und Verkapselungseffizienz während der Prozessschritte im flüssigen Zustand. Die physikochemischen Mechanismen während der Pulverlagerung werden hingegen durch komplexe Interaktionen der niedermolekularen Emulgatoren und Öl-Phase beeinflusst. So wurden sprühgetrocknete Emulsionen mit kristallisierten niedermolekularen Emulgatoren an der O/W Grenzfläche durch Freisetzung des verkapselten Öles destabilisiert. Da die beschriebenen Effekte von der molekularen Struktur der Formulierungsbestandteile abhängen, kann eine gezielte Variation der Formulierungsbestandteile zur Erhöhung der Stabilität sprühgetrockneter Emulsionen führen

Interfacial properties of β-Lactoglobulin at the oil/water interface: influence of starch conversion products with varying dextrose equivalents

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.TU Berlin, Open-Access-Mittel – 202

Potential of environmental scanning electron microscopy and SAXS to determine structural insights of plant-based emulsions with increasing dry matter content

Plant-based emulsions with increasing dry matter content show a large range of structural features from atomic to macroscopic length scales, which may be examined with scattering techniques in reciprocal space and microscopic techniques in real space. In this contribution, we focus on plan-based emulsions in terms of mesoscopic structure, and report on the impact of temperature and humidity on the structure measured via environmental scanning electron microscopy (ESEM) in real space. Small angle x-ray scattering in reciprocal space extends the knowledge on structural properties on smaller length scales at different temperature. Decreasing the humidity for the ESEM experiments revealed structural properties of different products. Temperature decrease from room temperature to 5 °C showed emerging crystalline peaks during SAXS measurements

Towards an improved understanding of spray-dried emulsions: Impact of the emulsifying constituent combination on characteristics and storage stability

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