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Cui F.,Jiangsu University | Cui F.,Jiangxi Provincial Engineering and Technology Center for Food Additives Bio production | Li X.,Jiangsu University | Zhou Y.,China Agricultural University | And 5 more authors.
Chinese Journal of Environmental Engineering | Year: 2013

The present paper focused on the effect of NaOH pretreatment on anaerobic digestion (AD) of corn stover. NaOH solution with the concentrations of 1.0%, 2.5%, 5.0%, 7.5%(M/V) was used for pretreating corn stover with 24-soaked or no-soaked status, and the biogas production effeciency was determined during the AD process. The obtained data showed that lignin of corn stover was degraded up to 38.54% by 5.0% NaOH pretreatment for 24 h. The total gas yield was 226.75 L/kg VS, which was 38.54% higher than the group without NaOH pretreatment. All the results indicated that the pretreatment of corn stover by 5.0% NaOH for 24 h was preferred for further study due to its significant improvement of biogas prodution and efficiency of anaerobic digestion.

Zhao Q.,Nanchang University | Selomulya C.,Monash University | Xiong H.,Nanchang University | Chen X.D.,Monash University | And 7 more authors.
Journal of Cereal Science | Year: 2012

Rice proteins, as a cheap plant protein source from the by-products of rice dreg processing, could potentially replace commonly used proteins such as soy and whey proteins in selected food products. In this study, the functional properties, surface hydrophobicity (H 0), sulfhydryl and disulfide bond contents, thermal properties, as well as secondary structures of native rice endosperm protein (REP) and processed rice dreg protein (RDP) extracted from long-grain indica rice, were compared. RDP was found to have a higher solubility associated with its relatively higher emulsifying and foaming properties than REP, as well as its water/oil holding capacity, although it was a denatured protein. The emulsifying properties were dependent on the solubility and H 0, while solubility was also related to the disulfide bond contents. Distinct differences in H 0, thermal properties, and disulfide bond contents between REP and RDP could be due to the conformational changes, as the industrial processing steps in the production of rice syrups caused an increase in β-turns at the expense of β-sheets and random coils of REP, leading to the unfolding of β-sheets into higher-ordered supramolecular structures for RDP, which could be responsible for its better functional properties. © 2012 Elsevier Ltd.

Zhao Q.,Nanchang University | Xiong H.,Nanchang University | Selomulya C.,Monash University | Chen X.D.,Monash University | And 5 more authors.
Food Chemistry | Year: 2012

The effects of various proteases on the formation and characteristics of rice dreg protein hydrolysates (RDPHs) were investigated. Enzymatic hydrolysis of often under-utilised rice dreg protein (RDP) with different enzymes studied here was found to significantly improve protein content and solubility. RDPHs prepared by alkaline protease showed better protein recovery, producing higher protein content with much smaller peptides, while hydrolysates generated by Protamex showed the highest antioxidant activities with more than 80% solubility over a wide pH range. The results indicated that the type of protease greatly influenced the molecular weight and amino acid residue composition of RDPH. The enzyme type also determined the functional properties and antioxidant activity of the recovered proteins. It was found that an optimum allocation of alkaline protease in addition to the Neutrase enzyme could be an appropriate strategy to produce RDPH with desirable functionalities, antioxidant properties, and low salt content. © 2012 Elsevier Ltd. All rights reserved.

Zhao Q.,Nanchang University | Selomulya C.,Monash University | Wang S.,Nanchang University | Xiong H.,Nanchang University | And 7 more authors.
Food Research International | Year: 2012

Rice dreg protein hydrolysates (RDPH) can potentially be used as natural antioxidants for a variety of emulsion-type food systems. They contained 89.9% protein, 934.2. mg/g total amino acids with 517.7. mg/g total hydrophilic amino acids, and 78% peptides smaller than 5. kDa. Here, the physical and oxidative stabilities of corn oil-in-water emulsions (10. wt.% lipid) containing RDPH (0-20. mg/mL) and stabilized by Tween-20 were investigated as a function of RDPH concentration and pH. The results showed that emulsions with RDPH and Tween-20 emulsions did not experience coalescence (when RDPH concentration < 20. mg/mL), and were more stable than emulsions prepared by either emulsifier alone (RDPH or Tween-20). RDPH and Tween-20 could not prevent coalescence, because when RDPH = 20. mg/mL, competitive adsorption existed at the interface between high concentrations RDPH and Tween-20. The negatively charged emulsion stabilized with 5. mg/mL RDPH and Tween-20 was found to be more stable at pH 5. RDPH was able to inhibit lipid oxidation, reducing the formation of lipid hydroperoxides and TBARS with increasing RDPH concentrations. Similarly the increase in pH also reduced oxidation, possibly by scavenging free radicals and chelating pro-oxidant metals. The antioxidant properties of RDPH at the interface of emulsion droplets would render them suitable as natural antioxidants in some food products. © 2012 Elsevier Ltd.

Zhao Q.,Nanchang University | Xiong H.,Nanchang University | Selomulya C.,Monash University | Chen X.D.,Monash University | And 5 more authors.
Food and Bioprocess Technology | Year: 2013

This work was done to investigate the effects of different drying methods in the preparation of rice protein isolates (RPIs), as the understanding could provide useful information regarding applications of plant proteins in the food industry. RPI from rice dreg protein, a cheap by-product from the production of rice syrups, was extracted using an alkali solution along with isoelectric precipitation, and subsequently dried by freeze drying (FD-RPI) or spray drying (SD-RPI). The differences in biochemical, physical, and structural characteristics were observed for the dried proteins. SD-RPI had higher protein solubility and emulsifying activity at the pH values between 5 and 11, with higher foaming capacities (127.08 ± 2.25 % compared to 118.83 ± 2.71 %) than FD-RPI. However, FD-RPI had larger mean diameter (2,114.2 ± 79.6 nm compared to 490.4 ± 44.8 nm of SD-RPI), higher water/oil holding capacity (p < 0.05), and thermal stability. In addition, FD-RPI contained more β-turn structures (43.04 % compared to 25.81 %), and less β-sheet and random coils than SD-RPI, indicating that the more compact and ordered conformations of FD-RPI might be related to their physicochemical and functional properties. The choice of drying method could significantly influence physicochemical and conformational properties of RPIs, consequently determining their specific functional properties. The understanding of drying effects on their properties could assist in selecting the appropriate drying method to optimize the utilization of RPIs in the food industry. © 2012 Springer Science+Business Media, LLC.

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