Release Model of Water-soluble Chitosan Nanoparticles for Protein Delivery

[Objective] The experiment aimed to explore release rule of water-soluble chitosan (WSC) in vitro. [Method]The bovine serum albumin(BSA) was taken as a model protein drug and some existing release models such as Kinetics model, Gompertz model, Weibull model, Higuchi model and Logistic model were used to fit the BSA release profile from WSC carriers. [Result] Except Higuchi model and Logistic model, other models could fit BSA release profile better. [Conclusion] Gompertz two-order kinetics model could fit the release of WSC nano-particles better and model parameters had practical physical meaning.

Palatability of Water-Soluble Extracts of Protein Sources and Replacement of Fishmeal by a Selected Mixture of Protein Sources for Juvenile Turbot(Scophthalmus maximus)

Poor palatability is a limiting factor for replacing fishmeal with other protein sources in aquaculture. The water-soluble molecules with low molecular weights are the major determinants of the palatability of diets. The present study was conducted to investigate the palatability of water-soluble extracts from single protein source(single extract pellets) and the mixture of these extracts with different proportions(blended extract pellets) in juvenile turbot(Scophthalmus maximus). Then according to the palatability of blended extract pellets, an optimal mixture proportion was selected, and a new protein source made from raw protein materials with the selected proportion was formulated to replace fishmeal. Summarily, the palatability of single extract pellets for turbot was descendent from fishmeal to pet-food grade poultry by-product meal, wheat gluten meal, soybean meal, peanut meal, meat and bone meal, and corn gluten meal. Subsequently, according to the palatability of single extract pellets, 52 kinds of blended extract pellets were designed to test their palatability. The results showed that the pellets presented remarkably different palatability, and the optimal one was diet 52(wheat gluten meal: pet-food grade poultry by-product meal: meat and bone meal: corn gluten meal = 1:6:1:2). The highest ingestion ratio(the number of pellets ingested/the number of pellets fed) was 0.73 ± 0.03, which was observed in Diet 52. Then five isonitrogenous(52% crude protein) and isocaloric(20 k J g^(-1) gross energy) diets were formulated by replacing 0(control), 35%, 50%, 65% and 80% of fishmeal with No.52 blending proportion. After a 10-weeks feeding trial, a consistent feed intake was found among all replacement treatments. Replacement level of fishmeal up to 35% did not significantly influence final body weight, specific growth rate, feed efficiency ratio, and protein efficiency ratio of turbot. Therefore, the water-soluble extracts of protein sources play an important role in improving the palatability of non-fishmeal protein sources in aquafeed.

Favorable and unfavorable amino acid residues in water-soluble and transmembrane proteins

We analyzed the amino acid residues present in the water-soluble and transmembrane proteins of 6 thermophilic and 6 mesophilic species of the domains Archaea and Eubacteria, and characterized them as favorable or unfavorable. The characterization was performed by comparing the observed number of each amino acid residue to the expected number calculated from the percentage of nucleotides present in each gene. Amino acids that were more or less abundant than expected were considered as favorable or unfavorable, respectively. Comparisons of amino acid compositions indicated that the water-soluble proteins were rich in charged residues such as Glu, Asp, Lys, and His, whereas hydrophobic residues such as Trp, Phe, and Leu were abundant in transmembrane proteins. Interestingly, our results found that although the Trp residue was abundant in transmembrane proteins, it was not defined as favorable by our calculations, indicating that increased numbers of a particular amino acid does not necessary indicate it is a favorable residue. Amino acids with high G + C content such as Ala, Gly, and Pro were frequently observed as favorable in species with low G + C content. Comparatively, amino acids with low G + C content such as Phe, Tyr, Lys, Ile, and Met were frequently observed as favorable in species with high G + C content. These are the examples to increase the supply of amino acids than expected. Amino acids with neutral G + C content, i.e., Glu and Asp were favorable in water-soluble proteins from all species analyzed, and Cys was unfavorable both in water-soluble and transmembrane proteins. These results indicate that amino acid compositions are essentially determined by the nucleotide sequence of the genes, and the amino acid content is altered by a deviation from expectation.

Heat Induced Gels from Coconut Press Cake Proteins

Freeze-dried coconut press cake powder (CPP), 43% w/w protein, was used to investigate the heat-induced gelation by heating in rheometer to 75℃ in a wide range of pH values, from 4 to 9. Low strain oscillatory method applied the measure visco-elastic propertieson 15% w/w CPP. The gel strength was also assessed by a texture analyzer. SDS-PAGE electrophoresis was conducted to identify the proteins evolved in the gel network structure and the gel micro-structure was also evaluated. At low pH, the CPP proteins formed soft (elastic modulus <100 Pa) particulate gels prone to syneresis, with aggregate size of the order of 4.2 micrometers. In the alkaline region, homogenous gels were induced by heating. Gel strength started to increase dramatically from 64℃ to 67℃, for pH 9 and pH 8 respectively, reaching the maximum gel elastic modulus over 1000 Pa at pH 9. The SDS-PAGE showed that the polypeptide sub-unities at 24, 32 - 34 and 53 kDa were the most prominent in gelation.

Coconut Press Cake Alkaline Extract—Protein Solubility and Emulsification Properties

The solubility and the emulsification properties of a crude freeze dried alkaline protein extract (APE), 30% protein, obtained from coconut milk press cake by one step extraction at pH 11, were characterized at pH 2 to 11, and the cream and subnatant fractions of the emulsion studied by SDS-PAGE electrophoresis. The protein solubility followed U profile, showing a minimum at pH 3 to 4, close to but not identical to reported iso-electric points of 4 - 5 for many coconut protein fractions. The extract showed good capacity to form oil-in-water emulsion outside the low solubility pH range. The bands that appeared to play a role in the emulsification were found at 32 and 42 kDa in SDS-PAGE electrophoresis, but the most predominant absorbed band was at 23 kDa.

海南岛几种栽培类型椰子肉脂肪和蛋白质含量分析

为进一步了解我国主要椰子种植区海南岛本地生长的椰子肉主要营养成分情况,对海南岛不同地区几种不同栽培类型的椰子肉脂肪和蛋白质含量进行了差异性分析,比较不同类型的椰子肉脂肪含量。结果显示,香水椰子肉脂肪含量最低,且与红高、海高、赤椰、绿矮、马哇杂交种存在显著性差异;红矮类型椰子肉蛋白质含量最高,且与黄矮、绿高、香水椰子类型存在显著性差异。产于文昌的椰子肉脂肪含量最高,且与东方、万宁的存在显著性差异;产于海口的椰子肉蛋白含量最高,且与产于琼海、儋州、屯昌、文昌的存在显著性差异。海南岛椰子肉的脂肪和蛋白质含量不仅存在栽培类型间的差异,也受种植地理区域的影响。因此,对椰子肉组分及含量变化情况开展研究很有必要。

响应面法优化维生素C碳点辅助提取椰蛋白工艺

以废弃椰粕为原料,维生素C碳点为辅助提取剂,水溶性椰蛋白提取率为主要考察指标,通过响应面法优化维生素C碳点辅助提取椰蛋白工艺.结果表明,维生素C碳点辅助提取椰蛋白最优工艺参数为:提取液pH值为11.9,5 mg/mL维生素C碳点用量为30.0μL,超声时间29.7 min,液料比为24.2 mL/g,在此优化条件下水溶性椰蛋白提取率为3.78%.研究结果为废弃椰粕再利用提供参考.

维生素C碳点对椰蛋白提取率及其功能特性的影响研究

以废弃椰粕为原料,首次将维生素C碳点应用于碱溶酸沉法提取水溶性椰蛋白。考察了提取剂pH值、维生素C碳点用量、超声时间、液料比对水溶性椰蛋白提取率的影响;同时考察了维生素C碳点对椰蛋白的功能特性(蛋白质溶解度(protein solubility,PS)、乳化活性指数(emulsion activity index,EAI)、乳化稳定性指数(emulsion stability index,ESI)、起泡能力(foaming ability,FC)、起泡稳定性(foaming stability,FS))的影响。结果表明,椰粕中水溶性椰蛋白的最佳提取工艺为提取液pH为11、5 mg/mL维生素C碳点用量25μL、超声时间为30 min、液料比(mL:g)为20:1,在优化的条件下椰粕中水溶性椰蛋白提取率为3.55%,是不加维生素C碳点的椰蛋白提取率1.67倍;维生素C碳点提高了椰蛋白的PS、EAI、FC,降低了椰蛋白的ESI、FS。

酶法提取椰子蛋白质及其对亚基的影响

研究酶制剂的种类、用量、提取温度、pH、料液比等因素对椰子蛋白质提取率的影响,通过正交试验研究最佳的提取条件。得到的椰子蛋白质进行SDS-PAGE分析,研究酶法提取对椰子蛋白质亚基组成的影响。结果表明,添加质量分数0.3%的风味蛋白酶的提取效果最好,各因素对提取率影响的次序为:料液比>pH>温度>提取时间,其中,料液比和pH对提取率的影响达到了显著水平;最佳工艺参数为:酶质量分数0.3%、50℃、pH8.5、料液比1∶15和时间2h,在此条件下,椰子蛋白质的提取率为78.28%。SDS-PAGE分析表明,风味蛋白酶对椰子蛋白的酶解作用十分显著,与缓冲溶液提取的椰子蛋白质相比,酶法提取的椰子蛋白质中小分子质量亚基含量很高。

椰肉中醇溶蛋白抗氧化活性

从脂质过氧化的抑制作用、对DPPH自由基(DPPH·)的清除作用、羟基自由基(·OH)的清除作用、Fe2+的络合能力等几个方面研究椰子醇溶蛋白的抗氧化活性,并以BHT、没食子酸,VE做为对照。结果表明,椰子醇溶蛋白对Fe2+具有很强的络合能力,对DPPH·有较强的清除能力,同时具有一定的清除·OH能力和还原能力,但其抑制脂质体过氧化作用的能力较弱。这表明椰子醇溶蛋白有较好的抗氧化活性,但其溶解性限制了其在脂溶性食品中的应用。

椰子果肉中蛋白质亚基的组成与含量分析

采用非变性聚丙稀酰胺凝胶电泳(Native-PAGE)和十二烷基硫酸钠-聚丙稀酰胺凝胶电泳(SDS-PAGE)分离分析椰子果肉中蛋白质主要亚基的组成、分子量和含量。结果表明,用pH7.8的磷酸盐缓冲溶液提取,椰子果肉中蛋白质在浓缩胶浓度为7.5%、分离胶浓度为11.5%的SDS-PAGE凝胶系统中可以得到很好的分离。在海南本地高种椰子的椰子果肉蛋白中含有11条亚基,分子量范围为13.6～64.5 kDa,主要是中、小分子量亚基。非变性凝胶电泳分析表明,高种椰子蛋白中含有5个不同分子量、不同电荷的组分。

pH、离子强度等因素对椰子分离蛋白溶解性和乳化性的影响

分析椰子分离蛋白(CPI)溶解性、乳化性、乳化稳定性及pH、离子强度和温度对这些功能特性的影响。结果表明,与大豆分离蛋白和棉籽分离蛋白相比,椰子分离蛋白具有较好的溶解性、乳化性、吸油性和吸水性;而pH、离子强度和温度等因素对椰子分离蛋白的溶解性、乳化性和乳化稳定性有显著影响。在等电点附近,椰子分离蛋白表现出最低的溶解性与乳化性;低离子强度可提高椰子分离蛋白的溶解性和乳化性,而高离子强度降低了其溶解性和乳化性;CPI在60℃时有较好的溶解性和乳化性。

国内外椰子蛋白质研究新进展

椰子蛋白质是一种资源丰富,营养价值高,保健功能好的植物蛋白质资源,但目前国内对它的研究报道极少。文章重点介绍了国内外关于椰子蛋白质的氨基酸组成、分类、制备、功能特性和保健功能的研究进展以及椰子蛋白在食品工业中的应用情况,以期对椰子蛋白质进一步的开发利用提供帮助。

椰子蛋白质研究进展

椰子蛋白质是一种资源丰富,营养价值高,保健功能好的植物蛋白质资源,但目前国内对它的研究报道极少。重点介绍了国内外关于椰子蛋白质的制备、组成、分类、功能特性的研究进展及椰子蛋白在食品工业中的应用情况,以期对椰子蛋白质进一步的开发利用提供帮助。

椰肉蛋白酶解及其产物的抗氧化活性研究

将新鲜椰肉粉碎脱脂,利用碱溶酸沉法制备椰肉蛋白。用Alcalase碱性蛋白酶、Neutrase中性蛋白酶、菠萝蛋白酶、Papain木瓜蛋白酶酶解椰肉蛋白,以DPPH自由基清除能力和水解度为指标对酶解过程进行分析,筛选出最适合制备抗氧化酶解物的酶为Alcalase碱性蛋白酶。然后采用单因素及多指标正交实验设计优化Alcalase碱性蛋白酶酶解条件,其中酶解温度和底物浓度对DPPH自由基清除率影响最大。优化后的制备参数为:酶解温度50℃,pH值10.5,加酶量14000 U/g,酶解时间7 h,底物浓度2%,该条件下水解液中蛋白含量为15.8 mg/mL,水解度和DPPH.清除率分别为29.16%和89.07%,椰肉蛋白酶解物显示出较强的抗氧化活性,接近同一浓度下谷胱甘肽的抗氧能力,比同浓度Vc的DPPH自由基清除率高3.33倍。

椰子果肉蛋白亚基的组成及品种间的差异分析

采用非变性聚丙烯酰胺凝胶电泳(Native-PAGE)和十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)方法对香水椰子、红矮、黄矮、海南本地高种、马哇、文椰78F1 6个椰子品种的果肉蛋白主要亚基的组成、分子量、含量、分类和命名等进行研究。结果表明,在椰子果肉蛋白中含有11～18条亚基,分子量范围为12~115 kDa,主要是中、小分子量亚基。其中,主要亚基有CSα、CSβ、CSA1、CSA2、CSB1、CSB2、CSδ和CSΔ。CSA1、CSA2为酸性亚基,CSB1和CSB2为碱性亚基;CSα的含量最高,其次,CSδ和CSΔ的含量也较高。方差分析表明,除CSB1外,其余7种亚基的含量在不同品种之间呈极显著性差异。Native-PAGE分析表明,在自然条件下,椰子果肉蛋白质是由5个分子大小不一、带有不同电荷的组分构成的。不同品种椰子果肉蛋白亚基组成的差别可能是不同品种椰子间口感和风味不同的原因之一。

不同SDS-PAGE分离胶浓度下椰子贮藏蛋白亚基的分离效果

采用SDS-PAGE浓缩胶浓度为7.5%,分离胶浓度分别为9%、10%、11%、11.5%、12%、13%、14%、15%、16%的凝胶系统,探讨不同分离胶浓度条件下椰子贮藏蛋白亚基的分离效果。结果表明,分离胶浓度对亚基电泳分辨率的影响非常明显。分离胶浓度为11%～12%时,蛋白质亚基的分辨效果很好;当分离胶浓度为11.5%时,椰子贮藏蛋白亚基的分离效果最好,可以得到9条清晰的亚基条带。

椰子分离蛋白起泡性、黏度及其影响因素的研究

分析了椰子分离蛋白(CPI)起泡性、泡沫稳定性、黏度及pH、离子强度、温度和蛋白质浓度对这些功能特性的影响。结果表明,椰子分离蛋白的起泡性和黏度与大豆分离蛋白(SPI)相近;而pH、离子强度、温度等因素对椰子分离蛋白的起泡性和黏度有显著的影响。在等电点(pH4.5)附近,CPI的起泡性和黏度最小,但却表现出最高的泡沫稳定性(91.25%);低离子强度可以提高椰子分离蛋白的起泡性,但高离子强度使CPI的起泡性、泡沫稳定性和黏度都变小;在70℃时CPI的黏度最大;蛋白质浓度变大时,CPI的黏度也显著增大。

脱脂椰子种皮的蛋白质功能性质研究

提取了脱脂椰子种皮中的蛋白质,对其功能性质,如溶解性、持水力、乳化性以及蛋白消化率等进行测定。结果表明,提取所得的脱脂椰子种皮蛋白质持水力(1.50 g/g)以及蛋白消化率(25.63%)均较低;pH对脱脂椰子种皮蛋白质的溶解性、起泡性及乳化性的影响较大,在pH4.0时,脱脂椰子种皮蛋白质的溶解性和乳化性最低;而不同浓度的蛋白质起泡性均在pH4.0时最高。

椰子分离蛋白质提取工艺的研究

利用磷酸盐缓冲溶液从椰子肉中提取椰子分离蛋白质,采用单因素实验和正交实验研究最佳工艺条件。结果表明,各因素对提取率的影响次序为:料液比>温度>提取时间>pH,其中,料液比对提取率的影响达到了显著水平;最佳工艺参数为:35℃、pH9.5、料液比1∶20、时间120min,在此条件下,椰子分离蛋白质的提取率为76.60%。