Mechanical and Microstructural Properties of “Wet” Alginate and Composite Films Containing Various Carbohydrates

Composite “wet” alginate films were manufactured from alginate–carbohydrate solutions containing 5% alginate and 0.25% pectin, carrageenan (kappa or iota), potato starch (modified or unmodified), gellan gum, or cellulose (extracted or commercial). The “wet” alginate films were used as a model to understand co‐extruded alginate sausage casings that are currently being used by several sausage manufacturers. The mechanical, optical, and microstructural properties of the calcium cross‐linked composite films were explored. In addition, the water holding capacity and textural profile analysis properties of the alginate–carbohydrate gels were studied. The results indicate that the mechanical properties of “wet” alginate films/casings can be modified by adding various carbohydrates to them. Alginate films with pectin, carrageenan, and modified potato starch had significantly (P < 0.05) greater elongation values than pure alginate films. The alginate–pectin films also had greater (P < 0.05) tensile strengths than the pure alginate films. Alginate films with extracted cellulose, commercial cellulose, and modified potato starch had lower (P < 0.05) puncture force, distance, and work values than the alginate control films. Transmission electron microscopy images showed a very uniform alginate network in the control films. Several large cellulose fibers were visible in the films with extracted cellulose, while the cellulose fibers in the films with commercial cellulose were difficult to distinguish. Despite these apparent differences in cellulose fiber length, the 2 cellulose films had similar puncture and tensile properties.     

基于高压脉冲电场技术提高玉米皮多糖提取率的研究

目的研究高压脉冲电场(high-voltage pulsed electric field,PEF)技术辅助提取玉米皮多糖。方法以玉米皮粉(纤维素含量21.25%)为原料,以多糖提取率为衡量指标,以电场强度、电场频率和液固比为3个重要因素,根据单因素及响应面试验设计构建PEF技术提高玉米皮粉酶解效果的回归模型,优化出最佳工艺参数;同时对提取的多糖进行中红外(mid-infrared spectroscopy,MIR)测定,与PEF辅助水提法比较分析提取多糖的结构差异。结果 PEF辅助水提法的最佳工艺参数为:电场强度25 k V/cm,电场频率2080 Hz,液固比42:1 mL/g,此条件下PEF辅助酶法对玉米皮多糖的提取率最高可达(15.36±0.25)%,与PEF辅助水提法相比提高了6.4%。中红外谱图结果表明,PEF辅助水提法和PEF辅助酶提法多糖在O-H振动及C=O振动上有着明显差别。结论PEF技术可以提高玉米皮多糖的提取率且PEF辅助酶提法效果更佳。     

碱处理对木棉纤维结构及性能的影响

采用质量浓度分别为4、6、8、10、12 g/L的Na OH溶液对木棉纤维进行处理,对比分析了不同质量浓度碱处理对木棉纤维的表面形态、质量损失率、力学性能、浸润性能、热性能以及化学组成等结构及性能的影响。结果表明:碱处理可去除木棉纤维表面的胶质,是纤维素的净化过程;经过适当质量浓度的碱处理,木棉纤维的断裂强力、浸润性能均有所增加,但当碱液质量浓度增加到一定范围时,木棉纤维的断裂强力、浸润性能会出现下降;碱处理对纤维素的热稳定性影响不大。     

烟梗浆亚微米醋酸纤维的制备及其性能

为探索烟梗浆二醋酸纤维素(CDA)制备的可行性及其可纺性,以醋酸为溶剂,浓硫酸为催化剂,采用低温乙酰化法制备了烟梗木浆三醋酸纤维素(CTA)和二醋酸纤维素,将二醋酸纤维素与市售二醋酸纤维素按质量比20∶80、35∶65、50∶50共混,通过静电纺丝技术进行纺丝,并对纤维的结构和性能进行表征。结果表明:反应时间为5 h,纸浆与乙酸固液比为1∶5,在活化过程中加入硫酸后,醋酸纤维素的取代度从2.68提高到2.86,达到了三醋酸纤维素的标准;在80 ℃时水解6 h后可得到取代度约为2.5的CDA;与纯纺CDA纤维得到的亚微米混纺纤维相比,烟梗浆二醋酸纤维素与市售二醋酸纤维素混纺纤维的线密度及其不匀率降低,表明了烟梗浆CDA混纺的可行性。     

中空聚酯短纤维耐碱性及其力学性能分析

为了分析中空聚酯短纤维与天然纤维纤维混纺织物进行碱精练加工的可行性,研究了氢氧化钠质量浓度、处理时间和温度对纤维中空结构与失重率的影响,并分析了失重率与力学性能之间的关系。研究结果表明,氢氧化钠处理条件控制适当,聚酯纤维的中空结构不会受到显著破坏,其耐碱性基本可以满足天然纤维素纤维碱精练加工的要求;氢氧化钠质量浓度、处理温度和时间对纤维失重率均有显著的影响,其中处理温度的影响最大;断裂强力随失重率的增大而逐渐降低,失重率超过6%时尤为显著。     

响应面优化绿豆皮不溶性膳食纤维超声辅助提取工艺

以绿豆皮为原料,采用超声波辅助碱法提取绿豆皮不溶性膳食纤维,通过单因素实验来探讨提取时间、提取温度、超声功率、碱液浓度、液料比五个因素对不溶性膳食纤维提取率的影响,并通过响应面分析来优化工艺条件。结果表明:采用碱液浓度3.0 mol/L,液料比15:1 mL/g,温度52 ℃,在350 W超声波作用下提取148 min,不溶性膳食纤维提取率最大为66.28%±0.052%,此工艺可以有效地从绿豆皮中提取不溶性膳食纤维。     

Insitu Self-Assembly of Bacterial Cellulose on Banana Fibers Extracted from Peels

ABSTRACT

In this research work, in-situ self-assembly approach was used the first time, to cultivate bacterial cellulose on the surface of fibers, extracted from banana peels. The characterization was performed using SEM, FTIR, and single fiber tensile test in order to determine the surface morphology and mechanical properties of modified fibers. As-prepared hybrid fibers exhibited comparatively better mechanical properties, which can be attributed to the self-assembly of bacterial cellulose on banana fibers’ surface. Overall, this research work suggests a novel route for fiber extraction from banana peels and to use them for the preparation of bio nano-composites with improved mechanical properties.     

Comparison of aqueous extraction efficiency and biological activities of polyphenols from pomegranate peels assisted by infrared,ultrasound, pulsed electric fields and high-voltage electrical discharges

The effects of aqueous extraction of bioactive compounds from pomegranate peels using conventional extraction (CE) and extraction assisted by infrared irradiation (IR), ultrasound (US), pulsed electric fields (PEF), and high-voltage electrical discharges (HVED) have been compared. For the extractions assisted by US, PEF and HVED, the saturation in extraction was observed approximately at the same specific energy input in the order of W ≈ 90–100 kJ/kg. HVED assisted extraction enhanced the recovery of polyphenols by ≈3 and ≈1.3 times as compared to US and PEF assisted extractions, respectively. Scanning electron microscopy (SEM) data evidenced that the highest yield of total polyphenols after the HVED treatment can reflect the presence of a strong damage of the microstructure of pomegranate skins. The obtained data on inhibition of growth of A. flavus and biosynthesis of aflatoxin B1 were explained accounting for the presence of different synergetic effects of phenolic compounds on inhibition of different bioactivities. All the studied extracts (0.2 mg/mL) demonstrated the higher inhibition efficiency for S. aureus (up to ≈80%) as compared to E. coli (up to ≈33%). PEF selectively extracted and enhanced the recovery of ellagic acid (≈740 μg/g DM), whereas HVED (≈345 μg/g DM) intensified gallic acid extraction compared to US, IR, HVED and WB.     

碱预处理对制备微晶纤维素的影响

为了加快酸水解制备微晶纤维素(Microcrystalline cellulose,MCC)时酸液的渗透效率,提高酸水解反应在纤维素纤维细胞壁内的区域反应均匀性,从而提升MCC的质量。本研究采用NaOH溶液对针叶木溶解浆进行有限润胀预处理,并通过激光粒度分析仪、X射线衍射仪(XRD)、扫描电子显微镜(SEM)、傅里叶变换红外光谱仪(FT-IR)及热重分析仪(TGA)等对MCC的各项质量指标进行检测,探究了碱预处理对酸水解制备MCC的影响。结果表明,在最佳NaOH质量分数(9%)预处理后,MCC平均粒径由52.1μm降低至41.8μm,粒径分布更加集中,MCC结晶度基本保持不变;碱预处理对纤维素纤维及MCC化学结构和热稳定性均无明显影响。     

Effect of Thermal Aging and Chemical Treatment on Tensile Properties of Coir Fiber

Effect of thermal aging and chemical treatment on the physical properties of coir fiber was investigated. Coir fibers were treated with sodium hydroxide and glutaraldehyde for 2 h. The influence of alkali and aldehyde treatment on tensile strength and elongation at break was studied in detail. Enhancement in tensile strength of coir fiber was observed up to five days of aging at 50°C and further decreased. Thermal cross linking of cellulose present in the fiber may be the reason for the increase in tensile strength and thermal degradation due to the chain scission of cellulose reduced the tensile strength. Sodium-hydroxide-treated samples showed an increase in tensile strength and reduction in elongation at break. The removal of impurities such as waxy and fatty acid residues from the coir fiber by reacting with strong base solution improved the strength of fiber. Cross linking of cellulose with glutaraldehyde in the fiber reduced the elasticity and enhances the strength of the material. Scanning electron microscopy was employed to analyze the change in surface morphology upon chemical treatment. Improvement in the tensile strength suggests that NaOH and glutaraldehyde can be effectively used to modify coir fiber with excellent physical properties.     

碱煮法提取稻秸秆纤维的工艺及性能探讨

通过L16(45)正交试验方法研究碱煮法提取稻秸秆纤维的工艺参数优化方案,确定烧碱浓度、碱液温度、反应时间、搅拌速度和固液比等因素与提取的稻秸秆纤维组成及性能的关系。结果表明:最佳的工艺组合是碱液温度90℃、反应时间120min、搅拌速度720r/min、固液比1g∶30ml、秸秆/氢氧化钠(质量比)1∶0.6;稻秸秆纤维的最佳性能是平均长度10.3mm,宽度19.3μm,成纤率25.88%,未离散率0.5%,纤维中纤维素成分质量分数为74.85%,灰分质量分数为2.21%。对最佳工艺参数下制备的稻秸秆纤维进行了微观结构和红外分析,为后期研究新型稻秸秆纤维复合材料提供参考依据。     

响应面法优化魔芋膳食纤维提取及结合有氧运动对大鼠高脂血症的影响

以魔芋粉为原料,采用超声辅助法提取魔芋中膳食纤维,并研究魔芋膳食纤维结合有氧运动对大鼠高脂血症的影响。在单因素试验基础上,采用响应面法优化魔芋膳食纤维提取工艺条件。结果表明:最佳工艺参数为碱液浓度2.1%、超声温度57℃、超声功率260 W,在此条件下,魔芋膳食纤维的平均得率为22.69%。大鼠实验结果表明:魔芋膳食纤维结合有氧运动能够使TC、TG、LDL-C水平显著降低,HDL-C水平显著提高,对高脂血症的大鼠起到良好的干预作用,并且两者结合效果要优于两者单独作用。     

提取方法对青叶苎麻叶蛋白功能特性的影响

分别采用超声波辅助碱溶液、盐溶液和水3种溶剂提取青叶苎麻叶蛋白质,并分析其浓度、氮溶解指数、起泡性、起泡稳定性、乳化性和乳化稳定性。结果表明,超声波辅助盐溶液提取的蛋白质浓度(10.73 mg/mL)和氮溶解指数(61.95%)最高,且该方法提取的蛋白质的起泡性(26.34%)及泡沫稳定性(24.49%)显著优于其他两种溶剂方法;超声波辅助水提取的蛋白质乳化性(11.17 m²/g)最佳,而超声波辅助碱溶液提取的蛋白质的乳化稳定性最佳(231.92)。     

Morphology,Structure, and Mechanical Properties of Natural Cellulose Fiber from Mendong Grass (Fimbristylis globulosa)

This study was to investigate the morphology, structure, and chemical properties of the Mendong fibers extracted from Mendong grass (Fimbristylis globulosa) in the form of raw and treated fiber by alkali-included chemical content and functional group and to evaluate the strength and properties of Mendong fibers compared with other natural fibers. These studies explore the chemical properties of the fiber including fiber composition and functional group by FTIR, mechanical properties of fiber, and the structural and morphological analysis of the fiber using SEM and XRD. The results showed that the chemical contents of Mendong fibers were 72.14% cellulose, 20.2% hemicellulose, 3.44% lignin, 4.2% extractive, and moisture of 4.2%–5.2%. Mechanical properties of the fiber were a strong character with tensile strength of 452 MPa, and modulus of 17 GPa. The structural properties of Mendong fiber such as crystallinity, crystalline index, microfibril angle, and crystalline size were 70.17% and 58.6%, 22.9°, and 14.3 nm, respectively. This fiber has competitive advantages compared with other natural fibers and can be developed further as a potential reinforcement of polymer matrix composites.     

挤压膨化辅助提取米糠可溶性膳食纤维及其特性研究

以新鲜米糠为原料,在单因素和正交试验基础上,通过分析不同挤压工艺和酶解条件对米糠中可溶性膳食纤维提取率的影响,优化挤压膨化辅助酶水解技术提取可溶性膳食纤维。同时采用扫描电子显微镜、差示扫描热量法等表征可溶性膳食纤维的结构及物化特性。试验结果表明,在挤压温度130℃、螺杆速度200 r/min、物料含水量20%,酶用量2.0%、酶解温度75℃、酶解时间90 min、p H 6.0的条件下,可溶性膳食纤维提取率为30.35%。米糠可溶性膳食纤维表面形态疏松,呈蜂窝颗粒状,内部由纤维素类物质形成支撑主体,热力学相对稳定。与未经挤压膨化处理提取的可溶性膳食纤维相比,挤压辅助提取的可溶性膳食纤维具有更高的持水力、结合水力、溶胀力、结合脂肪能力及丰富的空间网状结构,结构及物化特性均得到明显改善。     

Physicochemical and functional properties of flour and protein isolates extracted from seinat (Cucumis melo var. tibish) seeds

The physicochemical and functional properties of seinat seed flour (SSF), defatted seinat flour (DSSF), and protein isolates were studied. Protein was extracted from DSSF using an alkali solution with isoelectric precipitation and freeze drying. Freeze dried seinat seed protein isolates (FSSPI), SSF, and DSSF were evaluated for their physicochemical and functional properties. SSF contained high levels of crude fat and fiber (31.13% and 24.75%, respectively). FSSPI contained 91.83% protein versus 28.58% for SSF. The amounts of potassium, the mineral with the highest content, were 9,548.33, 6,439.03, and 1,029 mg/100 g in SSF, DSSF, and FSSPI, respectively. The functional properties were variable among samples. The protein solubility of FSSPI was significantly higher (p<0.05) than for DSSF and SSF. FSSPI has a significantly better (p<0.05) foaming capacity, water/fat absorption capacity, and bulk density than SSF and DSSF. FSSPI also showed an emulsifying capacity comparable to commercial soy protein isolates.     

何首乌藤纤维的结构及其物理性能

以PMFT藤为原料,经碱煮,以多聚磷酸钠、硅酸钠、亚硫酸钠为助剂进行脱胶,制取PMFT藤单纤维。对其长度、细度进行测量,通过显微镜、X 衍射和全反射红外分析对其结构进行表征,并对其吸放湿性能进行测试。.结果表明：所得单纤维的平均长度和直径及其变异系数分别为12.29mm,11.65μm和34.20%,21.58%;该纤维的纵向形态具有转曲、粗节等特点,横截面为不规则椭圆形,有中腔;纤维的结晶度和取向度分别为59.45%和0.88;红外光谱图为纤维素特征;密度为1.58g/cm-3;回潮率为8.22%,吸放湿性能介于棉与苎麻纤维之间。因此,该纤维可能成为一种新型纺织材料。     

碱处理对涤纶/光敏树脂复合材料力学性能的影响

针对光敏树脂经3D打印成型后试样力学性能较差问题,采用涤纶长丝增强光敏树脂的方法,使用光固化3D打印设备将涤纶长丝和光敏树脂复合成型制备涤纶增强复合材料。为获得较好的增强效果,对涤纶进行碱处理,研究了碱处理各条件下涤纶的减量率与纤维形貌和力学性能的关系,以及其对复合材料力学性能的影响。结果表明:随着减量率的增加,涤纶的形貌及力学性能改变越明显;当涤纶减量率为16.2%时,纤维表面出现连续纵向沟壑,力学强度下降6%,纤维的增强效果最好;经过改性处理的涤纶增强复合材料的拉伸强度和弯曲强度分别达到78 MPa和471 MPa,相比于未处理的纤维增强复合材料分别提升了66%和336%。     

可食性褐藻纤维素的分离纯化与结构分析

以我国主要可食性褐藻海带和裙带菜为对象,对其中的纤维素成分进行分离纯化,并分析纤维素的结构属性。海带的纤维素含量明显高于裙带菜,二者纤维素的提取率分别达原料干质量的5.59%及2.61%。通过酸水解-高效液相色谱分析及傅里叶变换红外光谱分析,提取的纤维素的纯度分别达99.86%及98.91%。海带纤维素的平均聚合度为813,高于裙带菜纤维素的315。粉末X射线衍射分析揭示了2种褐藻纤维素均具有天然高度结晶性结构,结晶度指数分别达72.06%和71.48%,与市售高等植物来源微晶纤维素的水平相当。对X射线衍射图谱的进一步解析表明:褐藻纤维素的结晶性区域以单链三斜晶系(Iα)为主,显著区别于高等植物纤维素的双链单斜晶系(Iβ)为主的结构。研究结果以期为优质膳食纤维资源的开发提供参考。     

Extraction and Characterization of Calotropis gigantea Bast Fibers as Novel Reinforcement for Composites Materials

The aim of this study is to scrutinize the use of Calotropis gigantea bast fibers as potential reinforcement in polymer composites. The bast fibers were extracted from the Calotropis gigantea plant bark and some of them were treated with alkali (5 wt.%) solution. The chemical composition, physico-chemical structural properties of the untreated and the alkali treated Calotropis bast fibers were studied. The results of chemical composition analysis indicated that alkali treatment removed most of the non-cellulose materials as confirmed by the FTIR analysis. The X-ray diffraction results exhibited that the crystallinity index of the alkali treated fibers increased in comparison with the untreated fibers, which agrees with the results obtained in the mechanical tests. The tensile strength and modulus of the alkali treated fibers were found to be higher whereas the elongation at break was lower than the untreated fibers. Thermal stability of alkali treated fibers was lower than that of the untreated fiber. Scanning electron micrographs showed roughening of the surface of the fiber due to the removal of the surface impurities and non-cellulosic components on alkali treatment.It can be concluded that alkali treatment is an effective method to improve the surface and mechanical properties of Calotropis bast fibers to be used in composite materials.