Heat-induced gelation of porcine blood plasma proteins as affected by pH.

Porcine plasma is a by-product of the meat industry that can be used as a food ingredient. It is a protein mixture, hence its composition can be modified to meet specific functionality requirements. In the present paper, the gelation properties of plasma and its two major fractions (serum and albumin) have been studied at pH 4.5, 6.0 and 7.5. Polyacrylamide gel electrophoresis (SDS-PAGE) revealed that albumin was the constituent that remained soluble to a larger extent during heat-treatments, and that acidic coagulation occurred at pH 4.5, making weak interactions the predominating ones between protein aggregates. Differential scanning calorimetry (DSC) and rheological tests showed that both the thermal stability and the gelation point of protein solutions were lower as pH decreased. The textural properties and water-holding capacities of plasma and albumin gels were more pH-dependent than serum. Albumin gels were the weakest and those of plasma at pH 7.5, the strongest. It has been determined that interactions between protein fractions play a key role in the gelling properties due to synergistic effects. This knowledge should be useful in the engineering of a plasma derivative product designed for specific food requirements, by reformulating its natural composition and enhanced by controlling pH.

Delivery of Functionality in Complex Food Systems: Physically inspired approaches from nanoscale to microscale, Paris 14 to 17 July, 2015.

The 6th international symposium in the series "Delivery of Functionality in Complex Food Systems: Physically inspired approaches from nanoscale to microscal" was held in the heart of Paris from 14 to 17 July, 2015. It brought together PhD students, academic food researchers and industrials from diversified food sectors. The scientific sessions of this meeting were constructed around important topics dealing with 1) Engineering of tailored-made structures in bio-based systems; 2) Complexity and emergent phenomena in the integrative food science; 3) Investigation of nano and microstructures in the bulk and at interfaces; 4) Modeling approaches from bio-molecules and matrix structures to functionality; 5) Tuning binding & release of bioactive compounds by matrix modulation, and finally; 6) Tuning the delivery of functionality to the body. These topics were selected to cover different scientific fields and to show the contribution of food physical structures to development of health- and plaisure-supporting food functions. The oral communications were all introduced by key note speakers and they were all illustrated by outstanding high quality short communications. One of the most original features of this symposium was the increasing number of presentations using multiscale and modeling approaches illustrating the concept of complexity and emergent phenomena integrative food science. These highlighted the importance of studies on interactions between structure properties of engineered delivery systems and human body (sensory properties, digestion, release, bioavailability and bioaccessibility).

Effect of fat nature and aroma compound hydrophobicity on flavor release from complex food emulsions.

Complex food emulsions containing either hydrogenated palm kernel oil (vegetable fat) or anhydrous milk fat (animal fat) were flavored by using different aroma compounds. The fats differed by their fatty acid and triacylglycerol compositions and by their melting behavior, while the aroma compounds (ethyl butanoate, ethyl hexanoate, methyl hexanoate, mesifurane, linalool, diacetyl, cis-3-hexen-1-ol, and gamma-octalactone) differed by their hydrophobicity. Application of differential scanning calorimetry to fat samples in bulk and emulsified forms indicated differences in the ratio of solid-to-liquid between temperatures ranging from 10 to 35 degrees C. Solid-phase microextraction coupled with GC-MS analysis indicated that flavor release from food emulsions containing animal or vegetable fat differed depending on both the fat nature and flavor compound hydrophobicity. The release of diacetyl was higher for emulsions containing animal fat, whereas the release of esters was higher for emulsions containing vegetable fat. The release of cis-3-hexenol, linalool, gamma-octalactone, and mesifurane (2,5-dimethyl-4-methoxy-(2H)-furan-3-one) was very similar for the two fatty systems. The above results were discussed not only in terms of aroma compound hydrophobicity, but also in terms of structural properties of the emulsions as affected by the lipid source.

Effect of processing on physicochemical characteristics and bioefficacy of ß-lactoglobulin-epigallocatechin-3-gallate complexes.

Varying amounts of epigallocatechin-3-gallate (EGCG) were encapsulated in ß-lactoglobulin (ß-Lg) nanoparticles, either native or processed, denoted as heated or desolvated protein. The stability, physical properties, and bioactivity of the ß-Lg-EGCG complexes were tested. Native ß-Lg-EGCG complexes showed comparable stability and binding efficacy (EGCG/ß-Lg molar ratio of 1:1) to heated ß-Lg nanoparticles (1% and 5% protein w/w). The sizes of heated and desolvated ß-Lg nanoparticles were comparable, but the latter showed the highest binding affinity for EGCG. The presence of EGCG complexed with ß-Lg did not affect the interfacial tension of the protein when tested at the soy oil-water interface but caused a decrease in dilational elasticity. All ß-Lg complexes (native, heated, or desolvated) showed a decrease in cellular proliferation similar to that of free ECGC. In summary, protein-EGCG complexes did not alter the bioefficacy of EGCG and contributed to increased stability with storage, demonstrating the potential benefits of nanoencapsulation.

Food protein aggregates as vitamin-matrix carriers: impact of processing conditions.

We studied the ability of protein aggregates for loading and protection of α-tocopherol, a model of heat- and light-sensitive bioactive compounds. Aqueous dispersions of whey proteins (4.5 wt.%, pH 6.7) in the absence and presence of α-tocopherol (4 wt.%) were prepared using an ultradisperser (10,000 rpm for 10 min and 65 °C), and then submitted to further high-pressure homogenisation (HPH) at 300 or 1200 bar for 12 cycles. Relative to free-vitamin dispersions, increasing HPH conditions in the presence of vitamin led to higher protein denaturation, more tryptophan quenching and wavelength blue-shift (by 10nm), in parallel with increased zeta potential values (by -10 mV), particle sizes (by 50%), and newly formed protein dimers, trimers and high molecular weight aggregates. As a result, the degree of vitamin degradation under increasing HPH and long-term storage was shown to decrease from 66% (ultradisper) to 50%, or to 30% (subject to further treatments at 300 or 1200 bar, respectively).

Lipid nanoparticles as vitamin matrix carriers in liquid food systems: On the role of high-pressure homogenisation, droplet size and adsorbed materials.

Twelve oil-in-water nano-emulsions were prepared using a melt high-pressure homogenisation process (HPH) at 300, 800 or 1200 bar. The resulting emulsions containing 20 wt% palm oil in the absence or presence of α-tocopherol were stabilised by whey proteins alone or in mixture with lecithin. Lipid nanoparticles in these emulsions were characterized for their particle size, surface charge and protein surface concentration (PSC) in relation to their stability against aggregation and coalescence, and to their ability for encapsulation and protection of α-tocopherol against chemical degradation. Increasing HPH values were accompanied by the formation of lipid nanoparticles with decreasing size and PSC, but increasing long-term stability against aggregation and coalescence in parallel with an increase in α-tocopherol degradation (up to 15 wt% for 1200 bar). Presence of α-tocopherol, led to increasing (or decreasing) PSC values with increasing (or decreasing) HPH values for lipid nanoparticles stabilised by proteins alone (or in mixture with lecithins). In addition to these structural properties, the ability for α-tocopherol long-term stability of nanoparticles in emulsions was shown to differ more depending on their adsorbed materials (protein alone, or in mixture with lecithin) than on their particle size values. After 2 months storage, α-tocopherol in emulsions prepared at 300, 800 or 1200 bar was protected against chemical degradation at 79, 77, 67 wt%, respectively, when whey proteins were used alone, instead of 66, 63, 48 wt% when proteins were used in mixture with lecithins. These results indicated the dominant role of adsorbed proteins on the protection of vitamin models by nanoemulsions. They are of a great technological importance for production of lipid nanoparticles presenting a high volume-to-diameter ratio values and consequently high exchange surfaces between the matrix carrier and water and oxygen environmental factors.