Development of nanocomposite biodegradable film containing iron nanoparticles biosynthesised by Saccharomyces cerevisiae

The use of nanoparticles in biodegradable films has been shown to improve their characteristics in food packaging. The study was designed to investigate the effect of iron oxide nanoparticles (IONPs) and lysed yeast cells residue (YSR) on the properties of whey protein concentrate (WPC) films. IONPs (0, 0.5, 1.0 and 1.5 mm ) biosynthesised by Saccharomyces cerevisiae and YSR were used to prepare WPC films. The addition of IONPs and YSR increased the tensile strength (TS) of the films by approximately 2.6 MPa compared with the control films (P < 0.05). Percent elongation and water vapour permeability of the films decreased significantly (P < 0.05) by the contribution of IONPs. All the films did not inhibit the growth of tested microorganisms. The incorporation of YSR in the film also did not make a significant change in any properties of the film (P > 0.05). The results indicated the usefulness of IONPs incorporation into WPC films to enhance mechanical but not antimicrobial properties.     

Preparation and in vitro evaluation of calcium-induced soy protein isolate nanoparticles and their formation mechanism study

Soy protein isolate (SPI) nanoparticles (28–179 nm) were prepared by employing a cold gelation method with a slight modification. The obtained nanoparticles exhibited uniform size distribution and spherical shape with a unique honeycomb-like core structure. Nanoparticle characteristics including size, surface charge and hydrophobicity could be adjustable by changing calcium concentration and environmental pH. Generally, higher calcium concentration and lower pH led to formation of nanoparticles with larger size, lower surface charge and hydrophobicity. Both protein conformation and nanoparticle dissociation studies indicated that calcium likely shielded negative charges on the SPI polypeptide chains, and functioned as a salt-bridge to permit polypeptide chains to approach one another. In this process, calcium favoured the development of β-sheet structures to form SPI aggregates stabilised by hydrogen bonding. These aggregates were then associated to build SPI nano-networks through hydrophobic interactions. In vitro study indicated that the SPI nanoparticles were non-toxic and mainly located in the cytoplasm when uptaken into Caco-2 cells.     

可食性大豆分离蛋白膜制备与性质

为探索新型生物膜材料的制备,以大豆分离蛋白为基本材料,探究大豆分离蛋白(SPI)、增塑剂(甘油)、还原剂(Na_2SO_3)、乙醇等添加量和处理温度、成膜液pH、成膜介质等条件对膜的完整率、厚度、透光率、水溶率、水蒸气透过系数、透油性等性质的影响。当SPI浓度在2%~6%时,随着添加量的增加,成膜变得容易,但是膜的厚度增加、水蒸气透过系数和透油系数变大、色泽变深。甘油添加量在2%以下可以改善膜的柔韧性,同时降低膜的透气性能和透油性。添加5%的乙醇也可以降低膜的透气性和透油性。添加0.1%的Na_2SO_3可以改善膜的色泽,同时降低膜的透油性。适当提高处理温度和溶液pH可以降低膜的透气性和透油性。     

Physical properties and antimicrobial activities of a persimmon peel/red algae composite film containing grapefruit seed extract

As a by-product of dried persimmon production, persimmon peel (PP) can be utilized as an edible film base material. In this study, PP/red algae (RA) composite films were prepared, and their physical properties were determined. Among the PP composite films, the 4% PP/1% RA composite film had the best physical properties (7.31 MPa, 8.16%, and 4.99 ng m/m²s Pa for tensile strength, elongation at break, and water vapor permeability, respectively). The optical property of the PP composite film was desirable because the color of the film had an intrinsic persimmon color. In addition, the 4% PP/1% RA composite film containing 1% grapefruit seed extract was prepared as an antimicrobial film. These results suggest that this PP composite film can be applied to food packaging.     

Preparation and physicochemical characterization of trans-resveratrol nanoparticles by temperature-controlled antisolvent precipitation

In order to enhance the oral bioavailability, trans-resveratrol (t-RVT) nanoparticles were prepared by temperature-controlled antisolvent precipitation with the hydroxypropyl methylcellulose as the stabilizer. The mean particle size was reduced by decreasing the precipitation temperature, mainly due to the higher nucleation rate and slower growth rate. The freeze dried t-RVT nanoparticles were well reconstituted in aqueous solution maintaining a similar particle size and distribution in the nanosize range that is prior to freeze drying without the aid of cryoprotectants. The SEM images exhibited some aggregation of individual spherical nanosized particles. The FT-IR analysis confirmed that the molecular structure of t-RVT nanoparticles was not changed after the precipitation process. Furthermore, t-RVT nanoparticles showed significantly enhanced saturation solubility and dissolution rate by the decrease in particle size and degree of crystallinity when compared to the raw t-RVT. The combined results have demonstrated that this method can considerably enhance the bioavailability of t-RVT.     

大豆分离蛋白-水溶性大豆多糖可食性复合膜的制备与性质

以大豆分离蛋白(soy protein isolates,SPI)和水溶性大豆多糖(soluble soybean polysaccharides,SSPS)为主要原料进行了可食性复合膜的制备与性质研究。综合考虑SPI与SSPS的比例、甘油、海藻酸钠添加量及钙离子浓度等影响因素,通过单因素与正交实验对成膜配方进行研究,得到了复合膜的最佳配比,并从水溶性、水蒸气透过性、抗拉伸强度、断裂延伸率等方面对膜的性质进行了综合评价。结果显示:在SPI∶SSPS质量比为1∶7,甘油添加量2%,海藻酸钠添加量4%,Ca2+浓度为1.0mol/L的条件下,复合膜的综合性能评分最高,为67.8。     

Preparation of isoflavones enriched soy protein isolate from defatted soy hypocotyls by supercritical CO2

Soy hypocotyls, the byproduct from soy protein industry, rich in isoflavones, was attempted to develop into a value-added functional food, soy protein isolate (SPI). Soy hypocotyls were defatted by supercritical CO₂ (SC-CO₂) under the following conditions as 35 MPa, 2 h, 45 °C with a constant flow rate of CO₂ at 5 l/min, fed from the bottom of the extraction vessel. Via extraction, the oil contents were lowered from 10.5 g/100 g in original soy hypocotyls to 0.2 g/100 g in defatted soy hypocotyls (DSH) with a Protein Dispersibility Index (PDI) value of 91.2 that contained about 2.18 g/100 g of isoflavones and 63.6 g/100 g of proteins. SPI was then extracted from DSH under the optimized conditions including: the pH of water solution at 6, the ratio of DSH to water solution as 1:10 and the extraction temperature at 30 °C with the extraction time of 30 min. The freeze-dried SPI contained 92.46 g/100 g of the proteins and 640 mg/100 g of isoflavones, where the three major β-glycosides, glycitin, daidzin and genistin accounted for about 83.7% of the total isoflavones. The yields of SPI and isoflavones were about 48% and 30% in terms of their respective total contents in DSH.     

Fabrication and characterization of TiO2/whey protein isolate nanocomposite film

Composite films of whey protein isolate and TiO₂ are formed through three simultaneous processes, i.e., the self-assembly of protein–protein, TiO₂–TiO₂, and the association of protein–TiO₂. All the processes could be controlled by adjusting TiO₂ concentration in the blended system. The self-assembly of protein–protein molecules constituted the main network of the composite film. A low TiO₂ concentration (<0.25%) dispersed the TiO₂ nanoparticles in the protein matrix, reinforced the association of protein–TiO₂, reduced the ability of UVC absorption, and promoted the fluorescence and tensile strength of the composite films. In contrast, a high TiO₂ concentration (>0.25%) enhanced the self-assembly of TiO₂–TiO₂ nanoparticles, brought fluorescent quenching, and produced a decline of the tensile strength and water vapor permeability. The transmittance of the visible, UVA, and UVB lights showed a first order exponential decay relative to the TiO₂ concentration.     

酶解玉米醇溶蛋白-叶黄素纳米粒的制备、结构表征及体外抗氧化和释放特性研究

本研究采用中性蛋白酶（Neutral protease, NPT）对玉米醇溶蛋白（Zein）进行酶解改性,通过反溶剂法构建玉米醇溶蛋白酶解物（Corn protein hydrolysate,CPH）负载叶黄素（CPH-LUT）纳米体系,研究了其结构表征、体外抗氧化活性及溶解释放特性。研究结果表明,最佳酶解条件为：酶用量 2.7%,酶解时间60 min,酶解温度50℃,酶解pH 6.0,在此条件下,对叶黄素的包封率最高可达92.1 ± 1.5%：制备的CPH-LUT纳米粒的平均粒径为173.7 nm,多分散系数为0.077,Zeta电位为-18.1 mV;抗氧化和体外释放实验表明,CPH-LUT纳米粒中叶黄素的溶解性以及抗氧化活性显著提高,叶黄素在胃液和肠液中的释放皆符合一级动力学模型,且CPH对叶黄素具有一定的缓释作用。NPT酶解改性的玉米蛋白可作为叶黄素类功能成分保护和输送的有效载体。     

Antimicrobial,rheological, and physicochemical properties of sago starch films filled with nanorod-rich zinc oxide

The effects of zinc oxide nanorod incorporation on the flow properties of sago starch solution and antimicrobial, sorption isotherm, water vapor permeability, and UV transmission of sago starch films were investigated. The nanorod-rich ZnO (ZnO-N) was homogenized by sonication and incorporated into sago starch solutions at different concentrations (e.g. 1%, 2%, 3%, and 5% w/w dried starch). Introduction of low concentration ZnO-N to starch solutions significantly increased the viscosity of the solution and significantly decreased the permeability of the films to water vapor by less than one third. Solubility, moisture content, and monolayer water content of the films were decreased, whereas contact angle was increased with higher ZnO-N concentration. ZnO-N starch films had 0% UV transmittance and were able to absorb more than 80% of Near Infrared spectra. ZnO-N sago starch films exhibited excellent antimicrobial activity against Staphylococcus aureus. These properties suggest that ZnO nanorod has the potential as a filler in starch-based films for use as active packaging materials in the pharmaceutical and food industries.     

Preparation of red algae film containing grapefruit seed extract and application for the packaging of cheese and bacon

Red algae (RA) film containing grapefruit seed extract (GSE) was used as a wrapping film for cheese and bacon. RA film containing 1% GSE was prepared to inhibit the growth of pathogenic bacteria such as Escherichia coli O157:H7 and Listeria monocytogenes. Wrapping of cheese and bacon with the film decreased the populations of E. coli O157:H7 and L. monocytogenes. After 15 days of storage, wrapping of cheese with the RA film reduced the populations of E. coli O157:H7 and L. monocytogenes by 1.21 and 0.85 log CFU/g, respectively, compared to control. Bacon wrapped with the RA film also decreased the populations of E. coli O157:H7 and L. monocytogenes by 0.45 and 0.76 log CFU/g, respectively. Wrapping of bacon with the RA film decreased peroxide and thiobarbituric acid values. These results suggest that RA film containing GSE is a useful wrapping material for extending the shelf lives of cheese and bacon.     

Effects of NaCl and soy protein isolate on the physicochemical,water distribution,and mobility in frankfurters

In this study, we investigated the effect of gel and rheological properties, microstructure, and water distribution of frankfurters with various amounts of NaCl (1 and 2%) and soy protein isolate (SPI, 3 and 6%). The frankfurter cooking yield, a*value, and hardness significantly increased with the increasing NaCl and SPI content. However, the frankfurter springiness and cohesiveness were lower in the case of 6% SPI and 2% NaCl content than in the case of 3% SPI and 2% NaCl content. The thermal stability of myosin improved with the increasing NaCl and SPI, resulting in more compact and continuous structures. Meanwhile, the initial T_2b, T₂₁, and T₂₂ relaxation times were significantly shorter, and the P₂₁ and P₂₂ peak ratios increased and decreased significantly, respectively, implying the increase of the immobile water content. Overall, the SPI use allowed the production of reduced-salt frankfurter with desirable quality.     

羧甲基葡甘聚糖/大豆分离蛋白复合膜的制备及表征

以溶液共混法制备羧甲基葡甘聚糖/大豆分离蛋白复合物.正交实验确定了羧甲基葡甘聚糖与大豆分离蛋白质量比为1.5∶1、pH10、6 mL/100g干粉质量的三氯氧磷作用下,40℃水浴反应3 h,羧甲基葡甘聚糖与大豆分离蛋白有良好的相互作用,复合膜的力学性能、抗潮性能及阻气性能均有明显提高,其中拉伸强度较羧甲基葡甘聚糖提高了117.6%,吸湿增重较羧甲基葡甘聚糖下降了19.02%,透湿系数降至6.7 g/mm·h·Pa,用红外光谱、Tg测定表征了其结构.     

米曲霉种曲和碱性蛋白酶协同水解玉米-大豆蛋白复配物及其产物的抗氧化活性

以玉米蛋白和大豆蛋白为原料,按m(玉米蛋白)∶m(大豆蛋白)=7∶3复配后,研究其水解产物的抗氧化活性。首先用米曲霉(Aspergillus oryzae)种曲和碱性蛋白酶(alcalase)协同水解玉米-大豆蛋白复配物,制备玉米-大豆蛋白水解物(CSPHs);然后通过测定CSPHs的DPPH自由基清除率和金属离子(Fe~(2+))螯合能力,分析其体外抗氧化活性;再建立双氧水(H_2O_2)氧化应激模型,探讨CSPH的细胞抗氧化活性。结果表明,CSPHs在体外具有较强的抗氧化活性,并且在加入质量分数为10%的米曲霉种曲与加入质量分数0. 8%的碱性蛋白酶情况下,协同水解后的产物CSPH4具有良好的细胞抗氧化活性。此时的水解度、可溶性蛋白含量分别为46. 10%和(73. 04±1. 68) mg/mL,·DPPH清除率和亚铁离子螯合能力分别为(41. 26±0. 69)%和(50. 23±3. 15)%。CSPH4可降低H_2O_2诱导的氧化应激人结肠癌细胞(Caco-2)细胞内活性氧(reactive oxygen species,ROS)的含量。米曲霉种曲和Alcalase协同水解复配物得到的产物具有良好的抗氧化活性,具有运用到食品工业中作为抗氧化剂的潜力。