The amino acid composition and physicochemical and functional properties of hemp (Cannabis sativa L.) protein isolate (HPI) were evaluated and compared with those of soy protein isolate (SPI). Edestin, a kind of hexameric legumin, was the major protein component. HPI had similar or higher levels of essential amino acids (except lysine), in comparison to those amino acids of SPI. The essential amino acids in HPI (except lysine and sulfur-containing amino acids) are sufficient for the FAO/WHO suggested requirements for 2-5 year old children. The protein solubility (PS) of HPI was lower than that of SPI at pH less than 8.0 but similar at above pH 8.0. HPI contained much higher free sulfhydryl (SH) content than SPI. Differential scanning calorimetry analysis showed that HPI had only one endothermic peak with denaturation temperature (T(d)) of about 95.0 degrees C, attributed to the edestin component. The T(d) of the endotherm was nearly unaffected by 20-40 mM sodium dodecyl sulfate but significantly decreased by 20 mM dithiothreitol (P < 0.05). The emulsifying activity index, emulsion stability index, and water-holding capacity of HPI were much lower than those of SPI, and the fat adsorption capacity was similar. The data suggest that HPI can be used as a valuable source of nutrition for infants and children but has poor functional properties when compared with SPI. The poor functional properties of HPI have been largely attributed to the formation of covalent disulfide bonds between individual proteins and subsequent aggregation at neutral or acidic pH, due to its high free sulfhydryl content from sulfur-containing amino acids.

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Some physicochemical properties and structural characteristics of microbial transglutaminase (MTGase)-induced biopolymers of sodium caseinate (SC) were investigated. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis and size-exclusion-high-performance liquid chromatography analyses showed that all components of SC were easily polymerized or transformed by MTGase to form high-molecular weight biopolymers, and the susceptibility order of individual components was κ -Casein (C) > α -C > β -C. The emulsifying properties of biopolymers depended on the incubation time with MTGase. The emulsifying activity index of biopolymers persistently increased with the MTGase (0-12 h) incubation time. The emulsion stability also increased with the incubation time ( < 4 h), then declined a little with longer incubation (4-12 h). The differential scanning calorimetry analysis showed that the thermal properties of the biopolymers obtained after a 12-h incubation were different from that of native SC or biopolymers obtained after a shorter incubation time ( < 4 h), suggesting that the former has higher thermal stability. In addition, the ultraviolet (UV) spectra showed that the UV absorbance (at 275 nm) of MTGase-induced biopolymers of SC decreased with an increasing incubation time with MTGase, and the maximal emission wavelength ( λ max ) slightly shifted to the "blue side." The fluorescence spectra showed that the λ max was related with incubation time with MTGase, slightly Blackwell Science, LtdOxford, UKJFBCJournal of Food Biochemistry0145-8884Copyright 403 shifting to the "blue side" after 4 h with no further changes; its relative fluorescence intensity also increased. These results suggest a relationship between the functionalities and structural characteristics of the MTGaseinduced biopolymers of SC.

The application of food-grade delivery systems for the encapsulation, protection and controlled release of bioactive food ingredients have recently gained increasing interest in the research fields of functional foods and pharmaceutics. Plant proteins (mainly soy proteins, zein and wheat gliadins), which are widely available and environmentally economic compared to animal derived proteins, can be made into various delivery platforms, such as micro- and nanoparticles, fibers, films and hydrogels. In this paper, we review the recent progress in the preparation of food-grade delivery systems based on plant proteins for bioactive ingredients, and highlight some of the challenges and directions that will be the focus of future research. The preparation and application of bifunctional particles, which were able to deliver the bioactives to oil/water interface and stabilize the interface, are also described, providing a novel perspective for the design of plant protein-based delivery system.