Drying of Fruits and Vegetables: Retention of Nutritional/Functional Quality

In the past, research and development in drying has focused on the process and technology and food drying was performed mainly to extended the shelf life without much importance on retaining quality attributes. Recently, however, efforts have been made to develop high-quality dried foods. This is achieved by utilizing novel drying technologies, by improving and optimizing existing drying methods, and by maximizing quality attributes such as structure, color, flavor, nutrition, etc. In an effort to highlight quality aspect of dried foods and biomaterials, a special issue of Drying Technology [2005, 23(4)] was published. The objective of this article is to present an overview of quality attributes normally considered in the drying of food and biomaterials and highlight the recent advances in drying methods for the retention of nutritional and functional properties of fruits and vegetables.     

Drying of Fruits and Vegetables: Retention of Nutritional/Functional Quality

In the past, research and development in drying has focused on the process and technology and food drying was performed mainly to extended the shelf life without much importance on retaining quality attributes. Recently, however, efforts have been made to develop high-quality dried foods. This is achieved by utilizing novel drying technologies, by improving and optimizing existing drying methods, and by maximizing quality attributes such as structure, color, flavor, nutrition, etc. In an effort to highlight quality aspect of dried foods and biomaterials, a special issue of Drying Technology [2005, 23(4)] was published. The objective of this article is to present an overview of quality attributes normally considered in the drying of food and biomaterials and highlight the recent advances in drying methods for the retention of nutritional and functional properties of fruits and vegetables.     

三维编织复合材料的细观结构与力学性能

归纳、梳理了三维编织复合材料细观结构表征方面较有代表性的单胞模型,分析、比较各结构模型的优缺点,从理论分析与试验测试两方面总结三维编织复合材料刚度和强度性能的研究成果与进展,探讨了细观结构表征与力学性能预报中存在的主要问题,并展望今后的研究重点与发展方向。     

木粉增强木质素／环氧树脂复合材料的制备与力学性能

将玉米秸秆酶解木质素和双酚A环氧树脂共混,利用低相对分子质量聚酰胺作为同化剂,采用热压工艺制备了一种木粉增强的交联型木质素,环氧树脂复合材料,研究了热压温度、热压压力以及木粉的加入对复合材料力学性能的影响。研究结果表明,随着热压温度和热压压力的增加,木粉增强木质素,环氧树脂复合材料的弯曲强度和冲击强度均先升高而后降低,在120℃热压温度、8MPa热压压力下复合材料的力学性能达到最佳。随着木粉含量的增加,复合材料的弯曲强度和冲击强度均升高;木粉的粒径也对复合材料的力学性能有较大影响;综合考虑复合材料的力学性能,优选加入40—80目的木粉,木粉的含量为20％。     

Preparation and Properties of Biodegradable Polymer Film Based on Polyvinyl Alcohol and Tropical Fruit Waste Flour

In this study, two different types of tropical fruit waste flour, rambutan waste flour (RWF) and banana waste flour (BWF), were blended with polyvinyl alcohol (PVOH) by solution casting method. The structure of the blend film was characterised by Fourier Transform Infrared Spectroscopy. The tensile strength and elongation at break of tropical fruit waste flour-filled polyvinyl alcohol were lower, but the tensile modulus was higher, than that of PVOH film. At a similar blend ratio, the tensile properties of the PVOH/RWF film were higher than the PVOH/BWF film, but the PVOH/BWF film showed higher water uptake than PVOH/RWF film.     

Antioxidative and Functional Properties of Pumpkin Oil Cake Globulin Hydrolysates

Cucurbitin extracted from pumpkin (Cucurbita pepo) oil cake was enzymatically hydrolysed with three different enzymes viz. alcalase, flavourzyme and pepsin. Antioxidative and functional properties of cucurbitin hydrolysates with different degrees of hydrolysis (DH) were investigated. The antioxidant activity of the hydrolysates was strongly dependent on the enzyme used. The hydrolysates obtained by alcalase and pepsin showed antioxidative potential whereas flavourzyme hydrolysates did not demonstrate these activities. Reducing power and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) scavenging activity of cucurbitin hydrolysate were positively related to DH. The highest antioxidant activity was found in the hydrolysate obtained by alcalase at DH 25.6 % [reducing power of 0.25 ± 0.01 A700 nm and ABTS scavenging activity of 3.34 ± 0.02 mmol/L Trolox equivalent antioxidant coefficients (TEAC)]. Hydrolysis by all enzymes increased the protein solubility within the studied pH range. The best emulsion activity and stability index (EAI = 143.28 ± 3.05 m²/g and ESI = 87.5 ± 1.96 min) have hydrolysates produced by flavourzyme (DH 9.2 %) whereas alcalase produced hydrolysates with the best foaming capacity (FC = 242 ± 3.21). The results demonstrate that hydrolysates produced in the present study have good functional properties as well as antioxidant activity indicating their possible use in different food systems.     

Curing Characteristics and Mechanical Properties of Oil Palm Wood Flour Reinforced Epoxidized Natural Rubber Composites

Abstract

The paper reports on the curing characteristics and mechanical properties of oil palm wood flour (OPWF) reinforced epoxidized natural rubber (ENR) composites. Three sizes of OPWF at different filler loadings were compounded with a two roll mill. The cure (t ₉₀) and scorch times of all filler size decrease with increasing OPWF loading. Increasing OPWF loading in ENR compound resulted in reduction of tensile strength and elongation at break but increased tensile modulus, tear strength and hardness. The composites filled with smaller OPWF size showed higher tensile strength, tensile modulus and tear strength. Scanning electron microscope (SEM) micrographs showed that at lower filler loading the fracture of composites occurred mainly due to the breakage of fibre with minimum pull-out of fibres from the matrix. However as the filler loading is increased, the fibre pull-out became very prominent due to the lack of adhesion between fibre and rubber matrix.     

还原氧化石墨烯增强水泥基复合材料微观结构及力学性能

采用水热还原法制备了不同还原程度的还原氧化石墨烯(RGO),并将其添加到水泥浆体中,制得石墨烯增强水泥基复合材料。采用傅里叶变换红外光谱(FT-IR)、力学性能测试仪、扫描电子显微镜(SEM)对氧化石墨烯(GO)还原程度及水泥基复合材料的力学性能和微观结构进行测试。结果表明,在120℃水热条件下,控制不同还原时间可以得到不同还原程度的RGO;随着GO还原程度的提高,复合材料力学强度不断增加;RGO可使水泥更加密实,降低了水泥浆体的孔隙率,对水泥基复合材料起到增强增韧的作用。     

Polypeptide Profile,Amino Acid Composition and Some Functional Properties of Calabash Nutmeg (<Emphasis Type="Italic">Monodora myristica</Emphasis>) Flour and Protein Products

The aim of this work was to compare the physicochemical and functional properties of calabash nutmeg (Monodora myristica) seed protein flour with those of protein-enriched products (albumin, globulin, and protein isolate). Defatted M. myristica seed flour (MMF) was used to prepare various protein products. A NaCl extract of MMF was dialyzed against water to obtain the soluble albumin fraction (MMA) and a precipitated globulin fraction (MMG). MMF was also extracted with NaOH, the extract adjusted to pH 4.0 and the precipitated proteins collected as the isolate (MMI). Non-reducing gel electrophoresis showed that the MMF, MMG and MMI had similar composition that was dominated by 55 and 110 kDa polypeptides while MMA consisted mainly of smaller (<35 kDa) polypeptides. However, under reducing conditions, the 110 kDa polypeptide was not observed. Amino acid composition revealed an Arg/Lys ratio that increased in the extracts (1.92, 2.28 and 2.11 for MMA, MMG and MMI, respectively) relative to that in MMF (1.85). MMA had 67.5–86.5% protein solubility in the pH 4.0–6.0 range while those of MMF, MMG, and MMI were 37.7–63.8, 2.7–69.4 and 3.8–55.1%, respectively. MMA, MMG and MMI were found to be better emulsifiers based on their smaller oil droplet sizes (8–14 μm) compared with the 14–33 μm for MMF emulsion. Maximum foaming capacity was highest for MMI (205%) when compared with MMA or MMG (150%) and MMF (89%). We conclude that protein enrichment led to significantly enhanced emulsion and foam-forming properties but high solubility may have contributed to reduced emulsion stability.     

二次烧结温度对牙科氧化锆陶瓷组织和力学性能的影响

研究二次烧结温度对氧化锆牙科陶瓷微观组织和力学性能的影响。方法：氧化锆亚微米粉经过干压、冷等静压成型后在1050ºC预烧结,然后将预烧结牙科氧化锆瓷块在1300ºC-1600ºC进行二次烧结。对不同二次烧结温度下材料的线收缩率、烧结密度、物相、三点抗弯强度进行测量分析,并通过扫描电镜观察试样的断面形貌。结果：结果表明随着二次烧结温度提高,氧化锆的密度、弯曲强度呈上升趋势。在1350ºC时体积密度达到6.10g/cm³,1500ºC时的机械性能最优,三点弯曲强度为852MPa,主晶相为四方相。结论：亚微米氧化锆粉体烧结活性高,力学性能优良,能够满足口腔全瓷修复材料的要求。     

HDPE/木粉复合材料性能的研究

本文以高密度聚乙烯(HDPE)和木粉为原料,通过同向旋转双螺杆挤出机,制备HDPE/木粉复合材料。研究了木粉含量和螺杆结构对HDPE/木粉复合材料流变-形态-性能的影响。结果表明:木粉含量的增加增大了复合材料的储能模量和复数黏度,降低了冲击强度,而厚度大和错列角大的捏合块元件的加入有助于降低复合材料的储能模量和复数黏度,增加冲击强度。     

Microstructure,dielectric, piezoelectric,and ferroelectric properties of fine-grained 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 ceramics

For preparing fine-grained 0.94Na_0.5Bi_0.5TiO₃-0.06BaTiO₃ lead-free ferroelectric ceramics, the precursor powders were synthesized via sol-gel method and calcined at various temperatures. The precursor powders calcined at 520 °C, 550 °C, and 600 °C exhibit mean grain sizes of 30 ± 4 nm, 54 ± 3 nm, and 78 ± 5 nm, respectively. By optimizing the synthesis parameters, the fine-grained ceramics with high relative densities (>97%) and mean grain size around 100 nm were prepared. The ferroelectric, dielectric, and piezoelectric behavior were investigated. The ceramics prepared using the different precursor powders show different piezoelectric, ferroelectric, and dielectric behavior. The ceramic calcined at 550 °C and sintered at 900 °C exhibits the breakdown strength higher than 85 kV/cm, which exhibits the maximum polarization of 38.4 ± 0.3 μC/cm², remanent polarization of 20.6 ± 0.4 μC/cm².     

Melt Rheological Behavior and Thermal Properties of Low-Density Polyethylene/Palm Kernel Shell Composites: Effect of Polyethylene Acrylic Acid

The melt flow behavior and thermal properties of low-density polyethylene (LDPE)/palm kernel shell (PKS) composites were studied. Polyethylene acrylic acid (PEAA) was used as a compatibilizer in the composites. The results showed that the increasing of PKS loading had decreased MFI values of LDPE/PKS composites. The presence of PEAA increased the MFI values of the LDPE/PKS composites. The apparent viscosity of the composites was found to exhibit a linear relationship with the reciprocal of the temperature. Thermal properties showed that higher filler loading tended to reduce the onset temperature as the PKS possessed lower degradation temperature compared to the LDPE. The presence of the PKS in the LDPE polymeric matrix improved the thermal stability of the composites. The addition of PEAA into the composites provided better interfacial bonding between the LDPE matrix and PKS filler, while higher onset temperature and lower total weight loss were observed of LDPE/PKS composites. The activation energy of the LDPE/PKS composites was increased with increasing filler loading. At similar filler loading, the presence of PEAA increased the activation energy of the LDPE/PKS composites.     

Effects of Tween 20 and Transglutaminase Modifications on the Functional Properties of Peanut Proteins

The effects of Tween 20 on the emulsification and gelation properties of peanut protein isolates (PPI) were investigated. The functional properties of different peanut protein products, including PPI, Tween 20-assisted aqueous extraction peanut proteins (TPP), and their transglutaminase-modified products (TG-TPP), were then compared. The results indicate that the addition of Tween 20 to the PPI resulted in higher emulsifying activity index (EAI) and emulsion stability index (ESI) values than PPI without Tween 20; however, the emulsions produced by the PPI–Tween 20 mixtures were easier to destabilize during storage. As the amount of Tween 20 was increased, both the surface hydrophobicity and gel strength of the PPI–Tween mixtures significantly decreased. TPP (containing approximately 11% Tween 20) exhibited significantly different functional properties from PPI. Compared with PPI, TPP had higher EAI and ESI values but a weaker heat-induced gelation ability. The protein solubility of TPP was markedly higher than that of PPI. Modification of TPP with transglutaminase (TGase) significantly enhanced their gelation and oil-binding properties but reduced the protein solubility and ESI value. The remarkable improvement in the gelation ability of TG-TPP was mainly attributed to the formation of high-molecular-weight protein aggregates and their conformational changes.     

Effects of Durian Seed Flour on Processing Torque,Tensile, Thermal and Biodegradation Properties of Polypropylene and High Density Polyethylene Composites

Composites containing various percentage of durian seed flour (DSF) in the polypropylene (PP) and high density polyethylene (HDPE) have been compounded using an internal mixer. The processing torque, tensile, thermal and biodegradation properties have been determined. The incorporation of DSF increases stabilization torque and had adversely affected the mechanical properties by reducing the tensile strength and elongation at break, while the elastic modulus is increased, as starch content increases. At similar filler content, DSF filled PP showed higher tensile strength and elastic modulus, while lower in elongation at break than DSF-filled HDPE. The scanning electron microscopy (SEM) of tensile fracture specimens revealed good adhesion and dispersion of the DSF granules in the polymer matrix. However, the SEM results showed agglomeration of the DSF at higher filler content in the polymer and hence revealed poor wetting between DSF granules and polymer. The TGA results showed that both of the composites systems with higher filler content have higher initial degradation temperatures, T₀, degradation temperatures, T_deg and total weight loss. A simple biodegradability test conducted on each composite system shows that composites are subjected to biodegradation, judging by the significant increase in carbonyl and hydroxyl index of the composites after the test.     

Microstructure,mechanical and tribological properties of TaCN composite films by reactive magnetron sputtering

In this paper, a series of TaCN composite films with different carbon content were deposited by the magnetron sputtering system and the microstructure, mechanical and tribological properties were investigated. The results showed that the deposited TaCN films exhibited a three-phase of face-centered cubic (fcc) Ta(C,N), hexagonal closed-packed (hcp) Ta(C,N) and amorphous CNx. With the increase of carbon content, the hardness of the TaCN films first increased and then decreased, after reaching a maximum of 33.1 GPa; the adhesion strength increased gradually; the coefficient of friction decreased monotonically and the wear property initially improved and then weakened at room temperature. The coefficient of friction of the TaCN film at 28.21 at.% carbon decreased first, then increased and then decreased again and its high-temperature wear rate first decreased slightly and then increased, as the temperature increased from room temperature (RT) to 600 °C. The TaCN film at 28.21 at.% carbon exhibited excellent an elevated-temperature tribological properties.     

Microstructure evolution,mechanical and tribological properties of Ti3(Al,Sn)C2/Al2O3 composites

In this paper, in situ formed Ti₃(Al,Sn)C₂/Al₂O₃ composites were fabricated by sintering the mixture of Ti₃AlC₂ and SnO₂. The Al atoms could diffuse out of the Ti₃AlC₂ layered structure to react with SnO₂, resulting in the formation of Ti₃(Al,Sn)C₂ solid solution and Al₂O₃. When the SnO₂ content was 20?wt.%, the sintered Ti₃(Al,Sn)C₂/Al₂O₃ composite exhibited the best overall mechanical properties, because of the optimized cooperative strengthening effect of solution strengthening and Al₂O₃ enhancement. When the SnO₂ content increased up to 30?wt.%, the flexural strength and fracture toughness of Ti₃(Al,Sn)C₂/Al₂O₃ composite dramatically decreased on account of the large accumulation of generated Al₂O₃. Moreover, according to the SiC ball-on-flat wear tests, it was found that the wear resistance of Ti₃(Al,Sn)C₂/Al₂O₃ composites was significantly improved as the SnO₂ content increased.     

Composition Profiles and Functional Properties of Dietary Fiber Powder from Lime Residues: Effects of Pretreatment and Drying Methods

Lime residues after juice extraction have proven to be a potential raw material for producing dietary fiber (DF) powder due to their good functional properties. Compositions and antioxidant activity of DF powder from lime residues as affected by selected pretreatment (hot-water blanching and ethanolic soaking) and drying methods, viz. hot air drying, vacuum drying, and low-pressure superheated steam drying (LPSSD) at 60–80°C, were investigated. Fresh lime residues contained significant amounts of vitamin C, phenolic compounds, and flavonoids. Hesperidin was a major flavonoid and only one polymethoxyflavone (i.e., tangeretin) was detected in small amounts. A decrease in the amount of interested bioactive compounds and their antioxidant activity was noted at almost all steps of processing. Higher retention of bioactive compounds was noted when the residues were subject either to vacuum drying or LPSSD; the total antioxidant activities were 61–62% and 81–82% when being assessed by the β-carotene bleaching and DPPH assays, respectively. Vacuum drying at 80°C was the most suitable condition for preparing DF powder from lime residues due to its short required drying time and its ability to retain bioactive compounds. The in vitro analyses imply that DF powder prepared by vacuum drying at 80°C has the potential to reduce blood glucose and cholesterol levels by exhibiting high glucose retardation index (GRI) and bile acid retardation index (BRI).     

Microstructure,mechanical behavior and oxidation resistance of disorderly assembled ZrB2-based short fibrous monolithic ceramics

Axially aligned fibrous monolithic ceramics present non-catastrophic fracture behavior via crack deflection and delamination along cell boundaries. However, severe in-plane anisotropy and time-consuming preparation procedures prevent their extensive promotion. The introduction of high content of weak phase components with poor oxidation resistance in weak interface destroys the excellent oxidation resistance of ceramic matrix. In this work, ZrB₂-based short fibrous monolithic (SFM) ceramics with in-plane isotropic mechanical properties and excellent oxidation resistance were easily prepared by hot pressing randomly assembled short ceramic fibers. The microstructure and mechanical behavior of ZrB₂-based SFM ceramics densified at various temperatures were systematically investigated. The mechanical properties of ZrB₂-based SFM ceramics slightly improved with the increase of sintering temperature. ZrB₂-based SFM ceramics exhibited excellent oxidation resistance and remained intact without macroscopic cracks after ablation for 615 s in oxyacetylene flame with maximum temperatures exceeding 2150 °C. The oxidation behavior was analyzed in detail.