Food Biophysics

Salvia-Trujillo, L.; McClements, D.

doi: 10.1007/s11483-015-9401-8pmid: N/A

Interest in using nanoemulsions as delivery systems for lipophilic food ingredients is growing due to their high optical clarity, good physical stability, and ability to increase bioavailability. Nanoemulsion-based delivery systems may need to be incorporated into food matrices that also contain conventional emulsions. The aim of this work was to evaluate the effect of adding nanoemulsions (d < 200 nm) to conventional emulsions (d > 200 nm) on the creaming stability and microstructure of the mixed systems. Droplet flocculation and rapid creaming was observed when the nanoemulsion concentration exceeded a particular level: the critical flocculation concentration (CFC) was 3.75 % and 0.25 % (v/v) for conventional emulsions with average droplet diameters of 350 and 250 nm, respectively. Confocal microscopy indicated that there was appreciable droplet flocculation, and the fraction of individual droplets with diameters < 100 nm decreased after 14 days storage, which was probably due to Ostwald ripening and/or coalescence. The results of the present study might have important implications for the incorporation of nanoemulsion-based delivery systems into food products containing larger fat droplets, such as dressings, sauces, or beverages.

Kaya, Murat; Baublys, Vykintas; Sargin, Idris; Šatkauskienė, Ingrida; Paulauskas, Algimantas; Akyuz, Bahar; Bulut, Esra; Tubelytė, Vaida; Baran, Talat; Seyyar, Osman; Kabalak, Mahmut; Yurtmen, Huseyin

doi: 10.1007/s11483-015-9404-5

Sahni, Ekneet; Thakur, Meena; Chaney, Michael; Sherman, Gregory; Siegel, David; Pikal, Michael

doi: 10.1007/s11483-015-9405-4pmid: N/A

The aim of this work is to examine the correlation between measured instability of model flavor compounds in glassy matrices with the calorimetric relaxation times of the matrices. Spray-dried carbohydrate matrices were chosen as the model compounds for this study. Enthalpy relaxation times were determined for spray-dried carbohydrate matrices using differential and isothermal calorimetric methods. The losses of the volatile methyl acetate, ethyl acetate and limonene, as well as formation of limonene oxidation products, were measured by gas chromatography. Storage conditions were 30 and 40 °C, with samples equilibrated with 11, 23, 33 and 43 % RH at each temperature. A comparison of the relaxation times for temperatures below Tg was made using Modulated DSC (MDSC) and a Thermal Activity Monitor (TAM). TAM yields significantly lower values for relaxation times implying that it is capturing some of the faster dynamics as well as dynamics that are activated near Tg. However, plots of relaxation times as determined by both techniques versus temperature appear to converge at Tg. An increase in the relative humidity results in moderately higher loss of volatiles (methyl acetate, ethyl acetate and limonene) and greater oxidation rates. In general, there is a good correlation between relaxation time and stability, with greater enthalpy relaxation time associated with better stability. Enthalpy relaxation time appears to be a useful predictor of stability for both loss of volatiles and oxidation of limonene.

Zielbauer, B.; Franz, J.; Viezens, B.; Vilgis, T.

doi: 10.1007/s11483-015-9410-7pmid: N/A

Selective denaturation of meat proteins - essential to reach desired textures - requires cooking temperatures corresponding to their different structure and interactions. Sous-vide cooking allows precise control over the denaturation state of meat proteins (and thus the cooking state of meat products) due to the possibility to cook at very well defined temperatures. Additionally, kinetic effects also play an important role. Differential scanning calorimetry (DSC) has been used here to follow the denaturation state of proteins in pork filet (Musculus psoas major), which had been heat treated at different time (10–2880 min) and temperature (45–74 °C) combinations. Additionally, the water loss (cooking loss) occurring during heat treatments has been determined. Four endothermic peaks have been observed in the DSC curves. Their individual time and temperature dependent enthalpies show that proteins become denatured at temperatures well below the peak temperatures if kept there for long times. This observation is underlined by statistical arguments. Cooking loss increases with time and temperature, while the main water loss occurs during the first 240 min and at temperatures above 60 °C. Due to the different kinetics found for protein denaturation and cooking loss, it is not possible to directly correlate the two quantities.

Ladjal-Ettoumi, Yakoub; Boudries, Hafid; Chibane, Mohamed; Romero, Alberto

doi: 10.1007/s11483-015-9411-6pmid: N/A

This work is focused on physicochemical and emulsifying properties of pea (PP), chickpea (CP) and lentil (LP) proteins. We evaluated the molecular weight distributions, surface net charge, free sulfhydryl group (SH) and disulfide bond (SS) contents, protein solubility and thermal stability of the protein isolates. Their emulsifying properties (droplet size distribution, flocculation, coalescence and creaming) were also determined as function of pH values. The three protein isolates exhibit similar physicochemical properties, including good solubility and high thermal stability despite a high degree of denaturation. In addition, we analysed the influence of pH on stability of oil-in-water (O/W; 10 wt%/90 wt%) emulsions stabilized by the legume protein isolates. Concerning emulsifying ability and stability, the most unfavourable results for all three protein isolates relate to their isoelectric point (pI = 4.5). A significant improvement in emulsion stability takes place as the pH value departs from the pI. Overall, this study indicates that pea, chickpea and lentil proteins have great potential as food emulsifiers.

Uluata, Sibel; Decker, Eric; McClements, D.

doi: 10.1007/s11483-015-9416-1pmid: N/A

Nanoemulsions have some important potential advantages over conventional emulsions for certain commercial applications due to their optical clarity, high physical stability, and ability to increase the bioavailability of lipophilic bioactives. In this study, the factors influencing droplet size and stability in nanoemulsions fabricated from a hydrocarbon oil and an anionic surfactant were examined. Octadecane oil-in-water nanoemulsions were produced by a high pressure homogenizer (microfluidizer) using sodium dodecyl sulfate (SDS) as a model anionic surfactant. The influence of homogenization pressure, number of passes, and surfactant concentration was examined. The droplet size decreased with increasing homogenization pressure, number of passes, and surfactant concentration. Nanoemulsions with low turbidity and small droplet diameters (≈62 nm) could be produced under optimized conditions. Interestingly, nanoemulsions containing relatively high surfactant levels were highly susceptible to creaming when they were only passed through the homogenizer a few times, which was attributed to depletion flocculation. These results show the importance of optimizing surfactant levels to produce small droplets that are also stable to creaming.

Ota, Ajda; Šentjurc, Marjeta; Bele, Marjan; Grabnar, Pegi; Ulrih, Nataša

doi: 10.1007/s11483-015-9417-0pmid: N/A

We investigated the influence of carrier systems for different commercially available water-soluble formulations for coenzyme Q10 on structural changes of model lipid membranes formed by 1,2-dipalmitoyl-sn-glycero-3-phosphocholine and by a mixture of phosphatidylcholine and sphingomyelin (2.4:1). Structural changes in the membranes were measured using fluorescence anisotropy, electron paramagnetic resonance, and differential scanning calorimetry. Two fluorophores and two spin probes were used to monitor membrane characteristics close to the water-lipid interface and in the middle of the bilayer of the model lipid membranes. Different water-soluble carrier systems were tested. These data show that different systems can facilitate penetration of CoQ10 in the lipid membranes, where an increase in the lipid order parameter was observed. In addition, water soluble CoQ10 formulations better protect lipids from oxidation in liposome solution. With the exception of the carriers in an emulsified formulation of CoQ10, those in the other samples did not have any significant effects on membrane fluidity.

Zhang, Ruojie; Zhang, Zipei; Zou, Liqiang; Xiao, Hang; Zhang, Guodong; Decker, Eric; McClements, David

doi: 10.1007/s11483-015-9418-zpmid: N/A

The influence of lipid concentration on the ability of excipient emulsions to increase carotenoid bioaccessibility from raw and cooked carrots was investigated using a simulated gastrointestinal tract (GIT). Excipient emulsions were fabricated using whey protein as a natural emulsifier and a long chain triglyceride (corn oil) as a digestible lipid. Changes in particle size, charge, and microstructure were determined as the carrot-emulsion mixtures were passed through simulated mouth, stomach, and small intestine. Carotenoid bioaccessibility increased with increasing digestible lipid concentration in the excipient emulsions (from 0 to 8 %). Carotenoid bioaccessibility was higher from boiled carrots than for raw carrots, which was attributed to disruption of plant cell structure facilitating carotenoid release. In conclusion, excipient emulsions are highly effective at increasing carotenoid bioaccessibility from carrots, which can be attributed to the ability of the small lipid droplets to rapidly solubilize the carotenoids.

Nawrocka, Agnieszka; Miś, Antoni; Szymańska-Chargot, Monika

doi: 10.1007/s11483-015-9419-ypmid: N/A

The aim of this research was to study which kind of conformational changes in gluten proteins were induced by addition of four dietary fibre (apple-cranberry, cacao, carob and oat) by using FT-Raman spectroscopy and to find relationships between conformational changes and rheological behaviour of bread dough in mixing and extensional tests. Structural studies showed that all fibres induced formation of β-like structures between two protein molecules (pseudo-β-sheets) with the band at 1616 cm−1 in the Raman spectrum. According to Principal Component Analysis, the strongest dependence was between changes in gluten structure and two extensographic parameters (resistance to extension and extensibility). Resistance to extension was positively correlated with content of α-helix and pseudo-β-sheets, while a negative correlation was observed between the parameter and content of β-sheets and β-turns. Gauche-gauche-gauche conformation of disulphide bridges and ability of tyrosine residues to hydrogen bonds creation improved mixing properties as stability of dough.

Böttcher, Sandra; Drusch, Stephan

doi: 10.1007/s11483-015-9420-5pmid: N/A

Saponins from various botanical origins highly differ in molecular structure. Little is known of the influence of structural differences between the different saponins on interfacial tension, short-term adsorption and foam properties at the air-water interface (a/w). In this study five triterpenoid saponins, with three of these being monodesmosidic and two bidesmosidic as well as one steroid saponin, were analyzed. Interfacial tension isotherms were measured using a tensiometer with a Wilhelmy plate and were fitted using the modified Frumkin model. For characterization of the short-term adsorption at the a/w-interface, two-fluid needle experiments were performed. Foaming, foam stability and foam structure were analyzed using a foaming device. A new method for semi-quantitative analysis of different foam structures was established. Additionally the impact of pH and ionic strength (addition of NaCl) on interfacial tension and foam properties were determined. The short-term adsorption of all saponins was limited by an additional barrier and was not diffusion-limited. Extracts from Quillaja saponaria Molina (QS), Gypsophila (GYP), Camellia oleifera Abel (TS) and Aesculus hippocastanum (ESC) lowered the interfacial tension to 37–42 mN/m and produced stable foams. The steroid saponin from Tribulus terrestris (TT) and the monodesmosidic saponin from Glycyrrhiza glabra (GA) had only poor interfacial and foam properties. Foams made from QS and GYP were only little affected by changes in pH and ionic strength. A reduction of the pH from 5 to 3 increased stability of foams made from GA significantly. Foams made from ESC and TS were negatively affected by increasing ionic strength.