Encapsulation of lycopene in Pickering emulsion stabilized by complexes of whey protein isolate fibrils and sodium alginate: Physicochemical property, structural characterization and in vitro digestion property.

In present study, whey protein isolate fibrils and sodium alginate complexes (WPIFs-SA) were prepared and further used to stabilize Pickering emulsions for lycopene delivery. The optimal interaction between WPIFs and SA occurred at pH 3.0, with a mass ratio of 2:1. Increasing the oil fractions and the content of WPIFs-SA complexes significantly improved Pickering emulsions' stability, concurrently reducing droplet size and increasing viscoelasticity. Meanwhile, it facilitated the formation of a thicker protective layer and a compact network structure around the oil droplets, offering better protection for lycopene against thermal and photo degradation. In vitro digestion studies revealed that as the oil fractions and complex contents increased, the lipolysis degree decreased. The engineered WPIFs-SA Pickering emulsion could be used as an innovative delivery system for the protection and delivery of lycopene.

Fabrication of dry S/O/W microcapsule and its probiotic protection against different stresses.

BACKGROUND: Encapsulation is commonly used to protect probiotics against harsh stresses. Thus, the fabrication of microcapsules with special structure is critical. In this work, microcapsules with the structure of S/O/W (solid-in-oil-in-water) emulsion were prepared for probiotics, with butterfat containing probiotics as the inner core and with whey protein isolate fibrils (WPIF) and antioxidants (epigallocatechin gallate, EGCG; glutathione, GSH) as the outer shell. RESULTS: Based on the high viscosity and good emulsifying ability of WPIF, dry well-dispersed microcapsules were successfully prepared via the stabilization of the butterfat emulsion during freeze-drying with 30-50 g L-1 WPIF. WPIF, WPIF + EGCG, and WPIF + GSH microcapsules with 50 g L-1 WPIF protected probiotics very well against different stresses and exhibited similar inactivation results, indicating that EGCG and GSH exerted neither harm or protection on probiotics. This significantly reduced the harmful effects of antioxidants on probiotics. Almost all the probiotics survived after pasteurization, which was critical for the use of probiotics in other foods. The inactivation values of probiotics in microcapsules were around 1 log in simulated gastric juice (SGJ), about 0.5 log in simulated intestinal juice (SIJ), and around 1 log after 40 days of ambient storage. CONCLUSION: Dry S/O/W microcapsule, with butterfat containing probiotics as the inner core and WPIF as the outer shell, significantly increased the resistance of probiotics to harsh environments. This work proposed a preparation method of dry S/O/W microcapsule with core/shell structure, which could be used in the encapsulation of probiotics and other bioactive ingredients.

Validation of Layer-By-Layer Coating as a Procedure to Enhance Lactobacillus plantarum Survival during In Vitro Digestion, Storage, and Fermentation.

Probiotics are sensitive to phenolic antibacterial components and the extremely acidic environment of blueberry juices. Layer-by-layer (LbL) coating using whey protein isolate fibrils (WPIFs) and sodium alginate (ALG), carboxymethyl cellulose (CMC), or xanthan gum (XG) was developed to improve the survival rate of Lactobacillus plantarum 90 (LP90) in simulated digestion, storage, and fermented blueberry juices. The LbL-coated LP90 remained at 6.65 log CFU/mL after 48 h of fermentation. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) indicated that dense and rough wall networks were formed on the surface of LP90, maintaining the integrity of LP90 cells after the coating. Stability evaluation showed that the LbL-coated LP90 had a much higher survival rate in the processes of simulated gastrointestinal digestion and storage. The formation mechanism of the LbL coating process was further explored, which indicated that electrostatic interactions and hydrogen bonding were involved. The LbL coating approach has great potential to protect and deliver probiotics in food systems.

Co-delivery of curcumin and epigallocatechin gallate in W/O/W emulsions stabilized by protein fibril-cellulose complexes.

Hydrophobic curcumin and hydrophilic epigallocatechin gallate (EGCG) are reported to exhibit a variety of biological activities and may exhibit synergistic effects when used in combination. A co-encapsulation system was developed to improve their applicability and bioavailability. This delivery system consisted of a water-in-oil-in-water (W1/O/W2) double emulsion stabilized by whey protein isolate fibrils (WPIFs) and cellulose nanocrystals (CNCs). Double emulsions were fabricated using a two-step emulsification method using either WPIF-CNC complexes or WPIF alone. The physicochemical stability, encapsulation performance, and digestive properties of the delivery systems were then investigated. The double emulsions stabilized by the WPIF-CNC complexes were more resistant to heat and salt stress, exhibited greater encapsulation stability, and had a higher bioaccessibility for curcumin (67.8%) and EGCG (68.9%) than those stabilized by WPIFs. This research shows that the stability and bioaccessibility of curcumin and EGCG can be enhanced by co-encapsulating them in emulsion-based delivery systems using nanostructured protein-polysaccharide complexes.

Enhancing emulsion stability and performance using dual-fibrous complexes: Whey protein fibrils and cellulose nanocrystals.

Edible proteins can self-assemble into fibrils, which can improve their performance as emulsifiers. However, they are limited in some food applications. We prepared whey protein isolate fibril-cellulose nanocrystal complexes (WPIF-CNC) by electrostatic complexation. The stabilities of emulsions prepared using either WPIF or WPIF-CNC were compared to evaluate the effect of complexation on emulsion formation and properties. Moreover, the potential of the emulsions to act as delivery systems for curcumin was investigated. WPIF and CNC were found to complex by hydrogen bonding, hydrophobic, and electrostatic interactions. The complexes formed were good Pickering stabilizers in oil-in-water emulsions. Emulsions formulated using the complexes were more resistant to creaming than those stabilized by WPIF. The complexes were able to form self-supporting gelled emulsions at 70 % oil concentration, which protected curcumin from photo- and thermal-degradation. Consequently, dual-fibrous complexes may have application in the food industry as novel emulsifiers for the creation of nutraceutical delivery systems.

Hydrogels assembled from hybrid of whey protein amyloid fibrils and gliadin nanoparticles for curcumin loading: Microstructure, tunable viscoelasticity, and stability.

Food grade hydrogel has become an ideal delivery system for bioactive substances and attracted wide attention. Hybrids of whey protein isolate amyloid fibrils (WPF) and gliadin nanoparticles (GNP) were able to assemble into WPF-GNP hydrogel at a low protein concentration of 2 wt%, among which WPF and GNP were fabricated from the hydrolysis of whey protein isolate under 85°C water bath (pH 2.0) and antisolvent precipitation, respectively. Atomic force microscope (AFM) images indicated that the ordered nanofibrillar network of WPF was formed at pH 2.0 with a thickness of about 10 nm. Cryo-SEM suggested that WPF-GNP hydrogel could arrest GNP within the fibrous reticular structure of the partially deformed WPF, while the hybrids of native whey protein isolate (WPI) and GNP (WPI-GNP hybrids) only led to protein aggregates. WPF-GNP hydrogel formed at pH 4.0 (85°C, 3 h, WPF:GNP = 4:1) possessed the largest elastic modulus (G' = 419 Pa), which far exceeded the elastic modulus of the WPI-GNP hybrids (G' = 16.3 Pa). The presence of NaCl could enhance the strength of WPF-GNP hydrogel and the largest value was achieved at 100 mM NaCl (∼105 mPa) in the range of 0∼500 mM due to electrostatic screening. Moreover, WPF-GNP hydrogel showed a high encapsulation efficiency for curcumin, 89.76, 89.26, 89.02, 85.87, and 79.24% for pH 2.0, 3.0, 4.0, 5.0, and 6.0, respectively, which suggested that the formed hydrogel possess good potential as a delivery system. WPF-GNP hydrogel also exhibited a good protection effect on the photodegradation stability of the loaded curcumin with the retention of up to 75.18% after hydrogel was exposed to ultraviolet radiation for 7 days. These results suggested that the viscoelasticity of WPF-GNP hydrogel was tunable via pH-, ion-, or composition-adjustment and the hydrogel showed excellent protection on the thermal and photodegradation stability of curcumin.

Effects of protein fibrillation and antioxidants on probiotic survival during ambient storage.

Drying of probiotic cultures is the main form of stabilization but dry probiotics face oxidative stress. The addition of antioxidants has been employed for protection of probiotics against oxidative stress, but results on the addition of antioxidants remain inconclusive. In this work, matrices of whey protein isolate fibrils (WPIF) with epigallocatechin gallate (EGCG) or glutathione (GSH) were used. Probiotic viability during ambient storage decreased in the order of WPIF > WPIF + EGCG > WPIF + GSH > WPI > WPI + EGCG > WPI + GSH. The improved protection of WPIF might be explained by its better cell encapsulation and the high antioxidant activity of WPIF. Both antioxidants accelerated the death of probiotic, which might be related with the antimicrobial activity or the cytotoxicity of the reaction products. This study proposed an excellent wall material of amyloid fibrils for probiotic protection during ambient storage, and questioned the "common sense" that antioxidants protect probiotics from oxidative stress.