Thermoplastic starch modified during melt processing with organic acids: The effect of molar mass on thermal and mechanical properties

Thermoplastic starch (TPS) was modified with ascorbic acid and citric acid by melt processing of native starch with glycerol as plasticizer in an intensive batch mixer at 160 °C. It was found that the molar mass decreases with acid content and processing time causing the reduction in melting temperature (T_m). As observed by the results of X-ray diffraction and DSC measurements, crystallinity was not changed by the reaction with organic acids. T_m depression with falling molar mass was interpreted on the basis of the effect of concentration of end-chain units, which act as diluents. FTIR did not show any appreciable change in starch chemical compositions, leading to the conclusion that the main changes observed were produced by the variation in molar mass of the material. We demonstrated that it is possible to decrease melt viscosity without the need for more plasticizer thus avoiding side-effects such as an increase in water affinity or relevant changes in the dynamic mechanical properties.     

荔枝果实干制加工的热烫和无硫护色工艺

荔枝是我国南方一种重要的热带、亚热带水果,具有较高的营养价值和商业潜力.然而,在高温高湿季节,采后荔枝果实极易发生腐烂变质、果皮褐变、病原菌侵染等品质劣变现象.因此,荔枝果实除鲜食外,常被加工成不同的商业产品,特别是荔枝果干.干制荔枝由于干制加工时间较长,易发生果皮褐变,导致其外观色泽、产品质量和风味丧失,最终限制荔枝...     

Effect of the Temperature on the Spray Drying of Roselle Extracts (<Emphasis Type="Italic">Hibiscus sabdariffa</Emphasis> L.)

The effect of the drying temperature on the volatile components and sensory acceptance of the Roselle (Hibiscus sabdariffa) extract in powder was investigated. The Roselle extraction was carried out by maceration with 7 L of 30% ethanol (v/v), 560 g of fresh Roselle calyces for 168 h. The Roselle extracts were spray dried at different temperatures 150, 160, 170, 180, 190, 200 and 210 °C, giving different outlet values about yield and final moisture. The volatile compounds in Roselle extract and dried samples were performed using needles of solid phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS HP-5890). Twenty volatile compounds were identified in the extracts among them terpenoids, esters, hydrocarbons and aldehydes. Fourteen volatile compounds were identified in the powder sample, but only ten were present in the Roselle extract. This indicates that some compounds were lost and some others were generated due to a degradation process. An acceptability sensory analysis showed that the best powder sample was the Roselle extract dehydrated using temperature between 190 °C and 200 °C (p < 0.05). There was not statistically significant difference in the pH of Roselle extracts ranging from 3.4 to 3.9. It was concluded that the spray drying temperature of the Roselle extracts has an effect on the volatile compounds losses.     

Dyeing of cotton and silk yarn with the extracted dye from the fruit hulls of mangosteen,<Emphasis Type="Italic">Garcinia mangostana</Emphasis> linn

The extracted dye from the dried fruit hulls of mangosteen was used as a natural dye for the dyeing of cotton and silk yarn. The optimal conditions for dye extraction were to extract the dried fruit hulls of mangosteen at 80°C for 1 hour with a 15 % w/v citric acid solution in a 1:4 ratio of mangosteen powder to solvent. Cotton dyeing with the extracted dye from the dried fruit hulls of mangosteen was carried out at 60°C for 60 minutes with a material to liquor ratio of 1:25. The effect on dyeing of mordant type with different mordanting methods was studied. The results showed that the dyeing of cotton using the post-mordanting method with ferrous sulfate and calcium hydroxide not only provided better depth of shade but also provided better wash fastness and light fastness than with other mordants (alum; zinc tetrafluoroborate) or without a mordant. Good fastness properties were also obtained using a post-mordanted silk with calcium hydroxide.     

Effects of plasticizer on the mechanical properties of kenaf/starch bio-composites

Research and development of biodegradable bio-composite can replacement the synthetic polymer materials, which is used for automobile interior materials, finishing materials of air conditioner and refrigerator. To develop both components as biodegradable bio-composite, this research used natural polymer starch as matrix and kenaf fiber as a filler. Various plasticizer(polyvinyl alcohol, polyethylene glycol, glycerol) were added and examined the mechanical properties of the kenaf/starch bio-composites according to these plasticizer. The kenaf bast which cultivated in Korea was retted with 2 % NaOH solution. The plasticizer weighting 10 % of that of matrix was added. kenaf/starch composites were molded with hot press for 30 minutes at 130 °C and 3,500 PSI molding condition. The mechanical properties such as tensile strength, elongation, and young modulus of the kenaf/starch composites were measured. Also, we measured the SEM cross-section images in order to investigate interfacial adhesion properties of fractured surfaces. The order of strength size of composites were G (12.42 MPa) > PVA (9.72 MPa) > PEG (4.73 MPa) samples respectively. The tensile strength of PEG sample is lower than the control sample (5.40 MPa).     

槟榔汁喷雾干燥工艺研究

研究槟榔汁喷雾干燥工艺条件。在单因素试验基础上，选取进风口温度、进料量、空气流量3个因素的3个水平进行正交试验，得到槟榔汁喷雾干燥工艺的优化组合条件为进风口温度190℃、进料量25 mL/min、空气流量为700 L/h。在此条件下所得产品的总生物碱含量、水分含量、出粉率分别为0.459%、5.17%和88.6%。     

Potato tuber sugars, starch and organic acids in relation to ozone exposure

Summary Data from two Swedish and one Finnish open-top chamber experiments were combined to investigate effects of ozone exposure on potato (Solanum tuberosum L.) tuber content of starch, sucrose, fructose, glucose, malic, citric and ascorbic acids. The glucose, fructose and malic acid concentrations showed strong negative correlations with ozone exposure, while citric acid, consistently increased with ozone exposure. No ozone effects could be demonstrated on starch, sucrose or ascorbic acid concentrations. It is discussed to what extent the changes found in potato tuber composition can be explained in terms of ozone effects on tuber maturity. Ozone exposure was expressed as the accumulated exposure over a cut-off concentration of 40 nmol mol⁻¹ (AOT40) and as the accumulated uptake of ozone over an ozone uptake rate threshold of 7 nmol m⁻² s⁻¹ (CUO 7). The difference in ability of the exposure indices to explain observed effects was small.     

Properties of dry film lubricants prepared by spray application of aqueous starch–oil composites

Aqueous dispersions of starch–soybean oil (SBO) and starch–jojoba oil (JO) composites, prepared by excess steam jet cooking, form effective dry film lubricants when applied as thick coatings to metal surfaces by a doctor blade. This application method necessitates long drying times, is wasteful, requires the addition of sucrose to promote composite adhesion to the metal surface, and restricts the substrate geometry to planar surfaces. These issues represent important barriers to the commercialization of this aqueous biobased dry film lubricant technology. We now report an air-assisted spray method that uses readily available spray equipment to apply aqueous starch–oil composite dispersions as thin coatings (0.15–2.0 mg/cm²) to metal surfaces quickly and efficiently. Aqueous dispersions of waxy maize starch–oil composites containing either SBO, JO or hexadecane (HD), having 0.020–31.7 wt% oil relative to starch, were applied by air-assisted spraying and could be dried to the touch in approximately 30 s. Additionally, sucrose was found unnecessary for adhesion of the sprayed coatings. Tribological ball-on-flat testing of metal specimens spray coated with starch–SBO, –JO, and –HD composites showed the thin films of starch–SBO and –JO performed better at reducing the coefficient of friction (COF) than the starch–hexadecane composites. A low COF ranging between 0.027 and 0.044 was obtained for the starch–SBO and –JO composites containing 4–5 wt% oil relative to starch. Above 4–5 wt% oil loadings, no further COF reductions were realized. Further results revealed that micrometer-sized oil droplets embedded within the dried starch matrix of the composite film are delivered “on demand”. It appears that when pressure is applied to the dry film lubricant, the starch matrix ruptures and releases the entrained oil to the friction surface.     

外源有机酸对铝毒胁迫下大豆根系形态的影响

通过添加三种不同浓度的有机酸(柠檬酸、草酸和苹果酸) ,测定铝毒胁迫下大豆的根系活力及主要根系 性状,研究了三种外源有机酸对大豆铝毒害的缓解效应。实验结果显示,三种有机酸在适当低浓度条件下,对大豆 铝毒害都有一定的缓解效果,其中以柠檬酸的缓解效果最好,草酸和苹果酸的缓解效果相当;但当有机酸浓度较高 时,反而会使大豆根系活力降低,根伸长受到抑制;有机酸对浙春2号的缓解作用强于浙春3号, 15d处理的缓解效 果优于30d。     

Film preparation by melt- or compression-process using poly(vinyl chloride) powder swollen with dimethylformamide

A melt-process was used to prepare high molecular weight Poly(vinyl chloride) (PVC) films without the use of a conventional plasticizer and heat stabilizer. Rigid PVC powder was swollen with dimethylformamide containing 4∼10 vol% water to reduce its melting temperature. The swollen powder was pressed at a relatively low temperature of 75∼125 °C to form a film shape, and then washed and dried. The visible light transmittance, X-ray diffraction, density and the tensile properties of the resulting films were examined to estimate the success or failure of film formation. The films could be produced by not only the melt-process but also a compression-process using the rigid, highly swollen PVC powder. The resulting films had no voids, which are generally observed in PVC products formed by a solution process. The minimum temperature for these processes decreased with decreasing water content in the mixture: The minimum temperatures according to the water content in the mixture to produce faultless films through the melt-process were 4 %–105 °C, 6 %–115 °C, 8 and 10 %–125 °C, while those through the compression process were 4 %–95 °C, 6 and 8 %–105 °C, 10 %–115 °C.     

Spray Drying of Chitosan Acid Salts: Process Development,Scaling Up and Physicochemical Material Characterization

We investigated a spray drying process for preparing water-soluble salts of high molecular weight chitosan (CH) intended for pharmaceutical excipient applications. CH was derived from chitin of marine lobster origin (Panulirus argus). The effects of organic acid (acetic or lactic acid) and the ratio (difference) of inlet/outlet air temperature (140/90 °C or 160/100 °C) on spray drying were studied. The yield of spray-dried CH salt powders ranged from 50% to 99% in laboratory and industrial-scale processes. The spray-dried dry powder of CH salts consisted of spherical agglomerated particles with an average diameter of 36.2 ± 7.0 µm (CH acetate) and 108.6 ± 11.5 µm (CH lactate). After dispersing the spray-dried CH salt powder samples in purified water, the mean particle sizes obtained for the CH acetate salts were 31.4 nm (batch A001), 33.0 nm (A002) and 44.2 nm (A003), and for the CH lactate salts 100.8 nm (batch L001), 103.2 nm (L002) and 121.8 nm (L003). The optimum process conditions for spray drying were found: an inlet air temperature of 160 ± 5 °C, an outlet temperature of 100 ± 5 °C and an atomizer disk rotational speed of 18,200 min⁻¹. The X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC) results confirmed the amorphous state of the CH salts. The ¹H nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR) spectra of CH acetate and lactate salts verified that the spray drying process does not affect the polymer backbone. In conclusion, both laboratory and industrial-scale spray drying methods for preparing water-soluble acid salts of CH are reproducible, and the physicochemical properties of the corresponding CH acid salts are uniform.     

淮山中多酚氧化酶特性及无硫护色脱水工艺

酶促褐变是导致淮山脱水加工过程中色泽变化的主要原因。通过研究淮山中多酚氧化酶的最适pH 值、最适温度等主要特性,设计选取适当的非硫成分NaC1、VC、柠檬酸进行护色,通过正交实验得到一种安全有效的无硫复合护色液,即含质量分数0.7%NaC1、0.3%Vc、0.6%柠檬酸的水溶液。在脱水加工过程中,用该护色液对淮山片浸泡护色4h后,在65℃下干燥4.5h,得到与传统硫熏漂白同样好色泽的终产品。     

New strategies in the preparation of exfoliated thermoplastic starch-montmorillonite nanocomposites

A simple method based on the combination of the intercalation from solution and melt-processing preparation methods was used to prepare highly exfoliated and compatible thermoplastic starch (TPS) and montmorillonite clay (MMT) nanocomposites. The effects of the MMT content on the thermal, structural, and mechanical properties of the nanocomposites were investigated. XRD diffraction was used to investigate the MMT exfoliation/intercalation degrees in the TPS matrix. Data from thermogravimetric analysis and differential scanning calorimetry revealed that the addition of MMT increased the thermal stabilities of TPS nanocomposites. Young's modulus and tensile strength increased from 8.0 to 23.8 MPa and 1.5 to 2.8 MPa with an increasing MMT content from 0 to 5 wt% without diminishing their flexibility. The improvement in such properties can be attributed to the good dispersion/exfoliation of MMT in the TPS matrix. Combining both methods, it was possible to obtain homogenous and transparent nanocomposites with excellent thermal and mechanical properties for application as packaging materials.     

Influence of citric acid and water on thermoplastic wheat flour/poly(lactic acid) blends. I: Thermal, mechanical and morphological properties

Wheat flour was plasticized with glycerol and compounded with poly(lactic acid) in a one-step twin-screw extrusion process in the presence of citric acid with or without extra water. The influence of these additives on process parameters and thermal, mechanical and morphological properties of injected samples from the prepared blends, was then studied.Citric acid acted as a compatibilizer by promoting depolymerization of both starch and PLA. For an extrusion without extra water, the amount of citric acid (2 parts for 75 parts of flour, 25 parts of PLA and 15 parts of glycerol) has to be limited to avoid mechanical properties degradation. Water, added during the extrusion, improved the whole process, minimizing PLA depolymerization, favoring starch plasticization by citric acid and thus improving phases repartition.     

Durable press finish of cotton fabric using malic acid as a crosslinker

It has been considered that malic acid,α-hydroxy succinic acid, could not form crosslinks in the cellulosic materials unless activated by other polycarboxylic acids such as butanetetracarboxylic acid or citric acid because there are only two carboxylic acids per molecule available for the formation of one anhydride intermediate. However we found that the dicarboxylic malic acid with sodium hypophosphite catalyst without the addition of other crosslinkers was able to improve wrinkle resistance of cotton up to 294° (dry WRA) and 285° (wet WRA), which is a measure of crosslinking level in cotton.¹H FT-NMR, FT-IR and GPC analysis indicated the in-situ formation of an trimericα, β-malic acid with a composition of 1:3 through the esterification between hydroxyl group and one of carboxylic groups in malic acid during curing. The crosslinking of cotton was attributed to the trimericα, β-malic acid, a tetracarboxylic acid, which can form two anhydride rings during curing. The influence of crosslinking conditions such as concentrations of malic acid and catalyst, pH of the formulation bath, and curing temperature were investigated in terms of imparted wrinkle resistance and whiteness. The addition of reactive polyurethane resin in the formulation slightly increased the mechanical strength retention of crosslinked fabric coupled with additional increase in wrinkle resistance.     

Fabrication and characterization of oat flour processed by different methods

The properties of oat flour can be manipulated by processing to suit various consumption and product development needs. In this work, three different processes typically used on oat flour, namely the extrusion, drum drying and enzyme-treatment spray drying process were evaluated with respect to how each process changes the quality of the oat flour. Results showed that the extrusion process produced oat flour with the best flow ability while the enzyme-treated spray drying process led to the lowest flowability. The color of enzyme-treated spray-drying oat flour was the brightest while the oat flours turned darker after extrusion and drum drying. In addition, drum dried oat flour had the highest capability to hold water. In terms of particle size distribution, the extruded and drum dried oat flour showed smaller particle size and the particle had less complete and irregular surfaces. On the other hand, the enzyme-treated spray-drying samples showed the best particle uniformity and sphericity. The viscosity of all the treated oat flour decreased with increasing shear rate, indicating the shear thinning behavior, and a weak gel-like behavior with very high viscosity was obtained via drum drying. The results reported here can be useful and provide a baseline to fully understand how the oat flour properties changes with different processing methods to offer a wider opportunity in using oat flour for food product fortification and design.     

低分子量有机酸对大豆根系形态和磷素吸收积累的影响

采用砂培试验研究了几种低分子量有机酸(柠檬酸、草酸、苹果酸和三种酸的混合)对根系形态和磷素吸收积累的影响.结果表明:不同有机酸处理均显著降低了大豆根系生物量和根冠比,同时使根长、根表面积和根体积均显著降低,而且随着有机酸浓度的增加抑制作用加强,几种有机酸混合后,抑制作用也相对增强,表明不同有机酸处理均抑制了大豆根系的生长,同时使大豆根系的竞争能力降低.几种有机酸处理均降低了大豆对磷素的吸收积累,从而降低了大豆对磷素的吸收效率,但磷利用效率增加.     

Effect of silk protein fibers on properties of thermoplastic rice starch

Biodegradable polymer was prepared as thermoplastic starch (TPS). Due to poor mechanical properties and high water absorption of TPS, thermoplastic rice starch (TPRS) was modified by reinforcing with natural silk protein fibers, as an alternative choice of fiber reinforcement. Different contents and lengths of silk fibers were varied and used as the reinforcement. Internal mixer and compression molding machine were used to mix and shaped the TPRS/silk composites. It was found that stress at maximum load and Young??s modulus of the TPRS/silk composites significantly increased with the incorporation of silk fibers. Water absorption of the TPRS/silk composites was also dropped by the addition of silk fibers. Moreover, thermal degradation temperatures of the TPRS/silk composites shifted to higher temperatures by the inclusion of the silk fibers. Functional group analysis and X-ray diffraction patterns were analyzed by FI-IR and XRD techniques, respectively. Furthermore, color measurement, morphology and biodegradation by soil burial test were carried out for different TPRS/silk composites.     

Changes in malic and citric acid contents during growth and storage ofSolanum tuberosum L.

Changes in malic and citric acid contents of apical and basal portions of tubers were followed during growth and development and in storage. Malic acid content was highest in the early harvested potatoes and decreased as the growing season progressed until a minimum level was reached approximately the first to the middle of September, and then started to increase again as temperatures got cooler in the fall. Malic acid content closely paralleled sucrose content during growth and development. The period at which low malic acid content was observed coincided with optimum time of harvest. Citric acid content did not show a definite pattern of behavior with increase in maturity. Low temperature storage resulted in decreased pH and an increase in malic and citric acid contents of tubers. Both acid contents were higher in the apical portion, although the pH was lower in the basal portion. No significant correlation was found between pH and content of either acid.     

不同黄皮品种果实品质和糖酸组分分析

采用常规的品质分析方法和高效液相色谱技术,对9个黄皮品种进行了果实品质和糖酸组分分析.结果表明,黄皮果实的可溶性糖主要由果糖、葡萄糖和蔗糖组成.其中果糖含量最高,葡萄糖次之,蔗糖最低.根据单糖与双糖的比例,黄皮属于单糖积累型.黄皮果实中有机酸主要由苹果酸和柠檬酸组成,可明显区分为苹果酸型和柠檬酸型两类.黄皮果实的糖酸比主要取决于有机酸的含量.综合来看,甜叶黄皮和大果甜鸡心的果实品质最好.