In order to identify wild fruits possessing high nutraceutical potential, the antioxidant activities of 56 wild fruits from South China were systematically evaluated. The fat-soluble components were extracted with tetrahydrofuran, and the water-soluble ones were extracted with a 50:3.7:46.3 (v/v) methanol-acetic acid-water mixture. The antioxidant capacities of the extracts were evaluated using the ferric reducing antioxidant power (FRAP) and Trolox equivalent antioxidant capacity (TEAC) assays, and their total phenolic contents were measured by the Folin–Ciocalteu method. Most of these wild fruits were analyzed for the first time for their antioxidant activities. Generally, these fruits had high antioxidant capacities and total phenolic contents. A significant correlation between the FRAP value and the TEAC value suggested that antioxidant components in these wild fruits were capable of reducing oxidants and scavenging free radicals. A high correlation between antioxidant capacity and total phenolic content indicated that phenolic compounds could be the main contributors to the measured antioxidant activity. The results showed that fruits of Eucalyptus robusta, Eurya nitida, Melastoma sanguineum, Melaleuca leucadendron, Lagerstroemia indica, Caryota mitis, Lagerstroemia speciosa and Gordonia axillaris possessed the highest antioxidant capacities and total phenolic contents among those tested, and could be potential rich sources of natural antioxidants and functional foods. The results obtained are very helpful for the full utilization of these wild fruits.

Soy protein isolate (SPI) and wheat gluten (WG) are widely used in commercial food applications in Asia for their nutritional value and functional properties. However, individually each exhibits poor gelation. In this study, we examined the microbial transglutaminase (MTGase)-induced gelation properties of SPI and WG mixtures with high intensity ultrasonic pretreatment. Ultrasonic treatment reduced the particle size of SPI/WG molecules, which led to improvements in surface hydrophobicity (Ho) and free sulfhydryl (SH) group content. However, MTGase crosslinking facilitated the formation of disulfide bonds, markedly decreasing the content of free SH groups. Ultrasonic treatment improved the gel strength, water holding capacity, and storage modulus and resulted in denser and more homogeneous networks of MTGase-induced SPI/WG gels. In addition, ultrasonic treatment changed the secondary structure of the gel samples as determined by Fourier transform infrared spectroscopic analysis, with a reduction in α-helices and β-turns and an increase in β-sheets and random coils. Thus, ultrasound is useful in facilitating the gelation properties of MTGase-induced SPI/WG gels and might expand their utilization in the food protein gelation industry.

In this study, the preparation and structural properties of spiral dextrin (SD)/vitamin E and SD/soy isoflavone inclusion complexes were studied. SD was obtained from debranched normal maize starch using isoamylases. After fractionation using a novel method of gradient ethanol precipitation, SD was separated into different fractions, among which SD-40 was found to be the optimal host molecule to prepare SD inclusion complexes with vitamin E or soy isoflavone. X-ray diffraction (XRD) and C cross-polarization magic angle spinning nuclear magnetic resonance (NMR) suggested that the crystalline structures of SD-40/vitamin E and SD-40/soy isoflavone were V6II and V6III types, respectively. Small-angle X-ray scattering revealed that the SD-40/vitamin E inclusion complex formed a tighter and more compact crystallite than the SD-40/soy isoflavone inclusion complex. Furthermore, the connection structures of inclusion complexes were investigated by two-dimensional nuclear Overhauser effect spectroscopy NMR, indicating that part of vitamin E with an alkyl chain was encapsulated in the helix cavity of SD-40, whereas the aromatic ring B of the soy isoflavone molecule was complexed by the helix cavity and screw of SD.

The effect of microwave pretreatment is useful in advancing gelation characters of MTGase-induced SPI/WG gels and provides the possibility for expanding the application of food protein. © 2015 Society of Chemical Industry.

The natural quinoa protein isolate (QPI) was largely reflected in the nanoparticle form at pH 7.0 (∼401 nm), and the ultrasound at 20 min progressively improved the contact angle (wettability) and surface hydrophobicity of the nanoparticles. Ultrasound process also modified the type of intraparticle interaction, and the internal forces of sonicated particles were largely maintained by both disulfide bonds and hydrophobic interaction forces. In emulsion system, the ultrasound progressively increased the emulsification efficiency of the QPI nanoparticles, particularly at high protein concentration ( c > 1%, w/ v) and higher emulsion stability against coalescence. As compared with the natural QPI-stabilized emulsions, the 20 min sonicated emulsions exhibited higher packing and adsorption at the protein interface. The microstructure of emulsions that occurs is bridging flocculation of droplets at low c (≤1%, w/ v), while the amount of protein particles could be high enough to cover the droplet surface at high c ( >1%, w/ v) with hexagonal array model arrangement. Thus these results illustrated that both natural and sonicated QPI nanoparticles could be performed as effective food-grade stabilizer for Pickering emulsion; however, the sonicated QPI nanoparticles exhibited much better emulsifying and interfacial properties.

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