熔喷非织造用聚(3-羟基丁酸-co-3-羟基戊酸共聚酯)/聚乳酸双组分生物降解材料的可纺性能

采用熔融共混法制备了质量比为100/0、75/25、50/50、25/75、0/100的熔喷非织造用PHBV/PLA共混材料,分别采用热重分析法（TG）、熔融指数法（MFI）、热台偏光镜法（POM）和毛细管流变法对共混材料的可纺性能进行了研究,并对其初生纤维的纺丝性能给予了初步评价。研究表明：PHBV的热稳定性差、加工窗口窄且熔体流动性差,PHBV/PLA共混材料的热稳定性和熔体流动性明显改善;PHBV结晶速率快, PLA对PHBV的结晶具有稀释作用;PHBV/PLA共混物为典型的切力变稀型流体,PHBV对温度和剪切速率变化敏感度高,PHBV/PLA共混材料的表观粘度随着PLA含量的提高而有所增大,但均小于纯PLA;PHBV纤维发粘现象严重,纺丝困难,随着共混材料中PLA含量的提高,纺丝性能提高,初生纤维表面变得光滑。     

Compatibilisation of starch/poly(butylene adipate co‐terephthalate) blends in blown films

Reactive extrusion was utilised for starch/poly(butylene adipate co‐terephthalate) (PBAT) blown film production, using maleic anhydride (MA) and citric acid (CA), alone or combined, as compatibilisers. These compounds (2% w/w) were added to the starch/PBAT (55:45) mixture after dispersion on glycerol. More rigid films, with greater tensile strength (9.82 ± 0.45 MPa), were produced when 2.0% CA was used. The opposite, little homogeneity and poor tensile strength (0.77 ± 0.12 MPa) and elongation (2.67 ± 0.67%) were found in films produced using 2.0% MA. Barrier properties to water vapour were improved by compatibilisers. FTIR analysis showed that CA and MA were able to promote esterification/transesterification reactions. Blends containing CA also showed better phase compatibilisation in the scanning electron microscopic images. It was found that in mixtures containing MA, the process and the concentration of this reagent need to be adapted to produce films with improved properties.     

季铵醚阳离子化改性对CMS浆料性能的影响

通过改变3-氯-2羟丙基三甲铵对淀粉的投料比,制备了一系列具有不同取代度的季铵型羧甲基淀粉,并以性能对比实验研究了这种变性淀粉的阳离子化变性程度对浆液黏度、黏附性及浆膜性能的影响。为了减少PVA的用量,研究了这种变性淀粉与PVA共混物对涤/棉纤维的黏附性能。结果表明:随着阳离子取代度的增加,季铵醚改性CMS的黏度明显提高;季铵型变性能够进一步改善羧甲基淀粉对涤/棉纤维的黏附性能,且随着阳离子取代度的增加,对涤/棉纤维的黏附性能增大。     

Effects of Compositional and Granular Properties on the Pasting Viscosity of Rice Starch Blends

The changes in swelling power and pasting properties of suspensions of starch blends were studied in dependence on starch composition and at various isothermal temperatures (T_iso). Samples were prepared by mixing rice starches from Kaoshiung Sen 7 (KSS7, a high‐amylose‐content variety) and Taichung waxy 70 (TCW70, a waxy variety). Generally, mixing these starches at a comparable ratio caused significant decrements in overall swelling power, onset temperature of gelatinization or viscosity rise, and final viscosity of hot pastes after 30 min of isothermal stirring. Notable increases in the peak and conclusion temperatures of gelatinization and in the peak viscosity of the pastes were also observed. Generally, all viscosity parameters of the blends showed two linear dependencies on the starch composition, the graphs intersecting at a critical starch composition depending on the parameters concerned. The onset temperature of viscosity increase was related to the volume fraction of swollen granules when they were just closely packed in suspension. The volume fraction of KSS granules was smaller than that of TCW70. In addition, the rate of viscosity increase and the peak viscosity of the starch suspensions could be well described in terms of the swelling power (Q) when Q ≤ ∼27, and depending on the T_iso examined. From the photomicrographs of starch suspensions, the extensive shear‐induced disintegration of TCW70 granules in the co‐existence of rigid KSS7 granules was evident and in turn responsible for the reduced final viscosities of the hot pastes obtained from starch blends.     

Influence of water on potato starch–lipid interactions. An electron spin resonance (ESR) probe study

Electron spin resonance (ESR) was used in order to study the mechanism of interaction of potato starch with lipids in systems with different water contents (40, 50 and 60% w/w) during heating and cooling. Different spin probes were used, on the one hand spin‐labelled stearic acids (5‐DSA and 16‐DSA), which limited lipids, and on the other hand the water‐soluble probe 4‐hydroxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl (Tempol), which was sensitive to changes in the dynamic properties of the water phase associated with the temperature‐induced starch structural transformations. Whatever the water content in the hydration range considered, Tempol was observed to be relatively mobile in the presence of potato starch, whereas a strong absorption of spin‐labelled stearic acids on potato starch granules took place at room temperature for all investigated starch–water systems. Spin‐labelled stearic acids were expected to stick on the starch granules. The mobility of the spin‐labelled stearic acid was less upon cooling than upon heating as a result of starch gelation. The mobility of spin probes decreased with increasing starch concentration. Introduction of a doxyl fragment at position 16 of the hydrocarbon chain leads to a lower degree of immobilisation of the spin probe as compared with 5‐DSA. This result suggests that there is a stronger interaction of polar sites of stearic acid with starch granules. © 2000 Society of Chemical Industry     

Physicochemical Properties of Casein‐Starch Interaction Obtained by Extrusion Process

Extruded samples of starch‐casein blends were processed by using a single‐screw extruder. The independent variables in the process were temperature (126–194°C), moisture content (18–29%) and starch‐casein blend (5–95%). These independent variables affected significantly the physicochemical and textural properties of the biopolymers. The highest values for expansion (EXP) and water absorption index (WAI) were found when a higher starch proportion was present in the blends, at 126°C barrel temperature and moisture content higher than 25%. By increasing the barrel temperature, from 126°C to 194°C, the water solubility index (WSI) and color parameter were increased. Initial viscosity (IV) and viscosity at 90°C (V90) were mainly affected by the barrel temperature at 194°C. However, the viscosity at 50°C (V50) was affected neither by the different extrusion variables nor by the biopolymer proportion in the blends. Compression force (CF) was strongly dependent on moisture content and casein proportion in the blend. The higher CF values were found at starch concentrations around 50% and 25% moisture content, for higher or lower values than these the obtained extruded products were softer and consequently had lower CF values.     

The influence of α-amylase-hydrolysed barley starch fractions on the viscosity of low and high purity barley β-glucan concentrates

Gelatinized barley starch was hydrolysed using porcine pancreatic α-amylase for various time intervals and the hydrolysate fractionated according to molecular weight distribution (low, medium and high) by gel permeation chromatography. The effects of hydrolysed starch fractions (2.5%, w/w) on the solution viscosity of low- (∼50%, w/w) and high- (∼88%, w/w) purity barley β-glucan (0.75%, w/w,) at different temperatures (20 and 37 °C) were determined and compared to that of a control. The results indicated that none of the hydrolysed starch fractions significantly influenced the solution viscosity of high purity β-glucan. However, addition of the medium molecular weight fraction to low purity β-glucan significantly increased its viscosity when determined at low shear rates (1.29–12.9 s⁻¹). Marginal changes in viscosity were observed at shear rates exceeding 12.9 s⁻¹. This study suggested that a non-β-glucan component in the low purity β-glucan concentrate probably influences the solution viscosity of “β-glucan–hydrolysed starch” blends.     

Chemical and Functional Properties of Phaseolus lunatus and Manihot esculenta Starch Blends

Chemical and functional characteristics were determined for Phaseolus lunatus (P) and Manihot esculenta (M) starches, and blends of these two starches (25P/75M, 50P/50M, 75P/25M (%, w/w)). Starch purity varied from 95 to 98%. The lowest amylose content was in M. esculenta (17.3%) and the highest in P. lunatus (32.4%) with the blends having intermediate values. Total dietary fiber content in M. esculenta was 1.7%, and 1.2% in P. lunatus; of the blends the 25P/75M had the highest percentage (2.3%). Initial gelatinization temperature was higher for P. lunatus (67.9°C) than for M. esculenta (57.6°C), with the blends having intermediate values. P. lunatus starch had the highest retrogradation value (8.3 mL/50 g starch) of all the starches, while M. esculenta and the 25P/75M blend had no retrogradation at all. The P. lunatus paste had the highest viscosity (125.5 mPa s) compared to the other pastes, which were statistically similar (P>0.05). Gel clarity was lower in P. lunatus (23.84%T) than in M. esculenta (51.76%T), with intermediate values in the blends. The 25P/75M blend was selected as having the best combination of characteristics, since it showed not retrogradation, had high viscosity (102 mPa s), and was stable in the heating‐cooling cycle. This makes it a starch with suitable functional properties for use in a variety of foods. These results suggest that blending native starches from different vegetable sources improves their properties.     

生物可降解聚（3-羟基丁酸-co-3-羟基戊酸共聚酯）/聚乳酸共混物的相容性和结晶性

针对聚（3-羟基丁酸-co-3-羟基戊酸共聚酯）（PHBV）热稳定性差、易分解的问题,通过与聚乳酸（PLA）采用熔融共混的方法制备了不同混合比例的的PHBV/PLA共混物,借助差示扫描量热仪、热重分析仪、动态热机械分析仪和X射线衍射仪研究了PHBV/PLA共混物的相容性、热学性能和结晶性等,并用热台偏光显微镜观察了PHBV/PLA共混物的动态热结晶过程。结果表明：PHBV/PLA共混物呈现分离的熔融温度和玻璃化转变温度,X射线衍射曲线上没有出现新的衍射峰,说明PHBV和PLA的相容性较差;PLA的加入提高了PHBV的热稳定性能,拓宽了PHBV的熔融加工窗口;随着共混物中PLA比例的增加,共混物的结晶相由“海-岛”相逐渐变成两聚合物分别连续成相。     

Thermostable Water Dispersions of Myofibrillar Proteins from Atlantic Mackerel (Scomber scombrus)

A process for preparation of a thermostable, low viscosity water dispersion of myofibrillar proteins from Atlantic mackerel (Scomber scombrus) was developed. The comminuted meat was washed sequentially with cold water, a bicarbonate solution, and cold water. It was then homogenized in ice-cold water. Apparent viscosity of the dispersion depended on protein concentration and temperature. Lowering pH to 3.7 by acetic acid reduced viscosity of the dispersion which remained unchanged irrespective of temperature. The proteins did not precipitate upon heating to 100° followed by centrifugation at 5000 xg for 15 min, even in the presence of 50 mM NaCl solution. However, increasing pH of the acidified solution resulted in precipitation of proteins. Acetic acid also prevented separation of water upon centrifugation of heated dispersion.     

THERMAL CHARACTERISTICS OF POLYLACTIC ACID/WHEAT GLUTEN BLENDS

The interaction between polylactic acid (PLA) and wheat gluten (gluten) has been studied using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction and phase contrast microscope. The primary DSC thermogram of gluten showed one glass transition (Tg) at 63C. Neat (pure) PLA also showed a Tg around the same temperature range followed by crystallization (Cry) and a melting (Mel) transition. Different PLA : gluten blends (20:80, 50:50, 80:20) showed a Tg followed by PLA Cry and immediate Mel transitions. However, subsequent heating‐cooling cycling of the blend demonstrated a decrease in PLA Cry and Mel transitions and the appearance of a second Tg. The presence of gluten reduced the number of cycles needed to change PLA Cry structure to mostly amorphous. The low PLA Cry indicates an interaction between the two polymers. The TGA data showed slower PLA degradation compared with gluten, where 10% was degraded at 316C while 10% of the gluten degraded at 254C. Solid‐state FTIR showed that amide I and II peaks significantly decreased signifying gluten‐heat degradation. A strong peak, corresponding to ester formation between gluten and hydrolyzed gluten molecules, appeared at 1750/cm. The esterification increased in the presence of PLA. The phase contrast microscope demonstrated that the melting of PLA starts at 150C, which means that the continuous phase between 150 and 250C was the melted PLA. At 220C, gluten formed a thin layer; and at about 245C, it aggregated.     

压力对聚对苯二甲酸乙二醇酯-聚酰胺6共聚物/聚酰胺6共混物流变性能的影响

为研究高压条件下聚合物的流变性能,以熔融共混挤出的方法制备聚对苯二甲酸乙二醇酯-聚酰胺6嵌段共聚物(PET-PA6)与聚酰胺6(PA6)共混物,利用安装在反向压力腔末端的旋塞控制毛细管出口压力,研究该共混物在出口压力为5~50 MPa条件下,剪切速率和温度对PET-PA6/PA6共混物流变行为的影响。结果表明:PET-PA6/PA6共混物的剪切黏度随压力的变化规律符合Barus方程;在恒定剪切速率下,随着毛细管内平均压力的增加,剪切黏度逐渐增大;当剪切速率从108 s^-1增加到1 080 s^-1时,压力系数减小19.24%,当温度从265 ℃增加到 290 ℃ 时,压力系数减小32.33%,共混物熔体剪切黏度对压力的依赖性随剪切速率和温度的增加逐渐减小。     

Effect of Organic Nitrogen Sources on Raw Starch‐Digesting Glucoamylase Production of Rhizopus sp. MKU 40

In a liquid cultivation of Rhizopus sp. MKU 40, supplementation of the medium with 1.5% (w/v) organic nitrogen sources (neopeptone, casein from milk, and meat extract) had a slightly positive effect on glucoamylase (GA) (EC 3.2.1.3) activity compared with the medium lacking organic nitrogen sources. The addition of organic nitrogen sources induced production of protease. Supplementation of the medium with 1.5% (w/v) organic nitrogen sources resulted in an acid and neutral protease activity of 11 — 25 U/mL and 12 — 20 U/mL, respectively. The co‐existence of GA‐I [a highly raw starch‐digesting glucoamylase (RSDG)] and protease in the same medium leads to the production of Ga‐II (an extremely weak RSDG) from GA‐I. As a result the RSDG activity in the medium decreases. Raw starch adsorption rates of a medium without organic nitrogen sources were 100%, because the medium contained only GA‐I. In contrast, the media supplemented with organic nitrogen sources had low starch adsorption rates because the media contained both GA‐I and GA‐II. The results presented in this paper indicate that supplementation of the culture medium of Rhizopus strains with organic nitrogen sources negatively affects GA‐I production.     

Studies on interactions of corn starch with casein and casein hydrolysates

Incorporation of non-starchy substances into starch pastes modify their viscosity and rheological profile. Protein hydrolysates blended with starch have been used in the formulation of hypoallergenic weaning and specialised adult nutritional formulas. In the present work, an attempt has been made to study the interaction of corn starch (5% w/v) with casein and its hydrolysates with respect to changes in the paste viscosity and the gelatinization temperature when heated in a Brabender amylogram. The pastes resulting on heating blends of starch and the casein/casein hydrolysates were also studied for their rheological profile on a Haake viscometer to confirm the effect under varying shear rates.     

Steady and Dynamic Shear Rheology of Rice Starch‐Galactomannan Mixtures

Rheological properties of rice starch‐galactomannan mixtures (5%, w/w) at different concentrations (0, 0.2, 0.4, 0.6 and 0.8%, w/w) of guar gum and locust bean gum (LBG) were investigated in steady and dynamic shear. Rice starch‐galactomannan mixtures showed high shear‐thinning flow behaviors with high Casson yield stress. Consistency index (K), apparent viscosity (η_a,100) and yield stress (σ_oc) increased with the increase in gum concentration. Over the temperature range of 20–65°C, the effect of temperature on apparent viscosity (η_a,100) was described by the Arrhenius equation. The activation energy values (E_a = 4.82–9.48 kJ/mol) of rice starch‐galactomannan mixtures (0.2–0.8% gum concentration) were much lower than that (E_a = 12.8 kJ/mol) of rice starch dispersion with no added gum. E_a values of rice starch‐LBG mixtures were lower in comparison to rice starch‐guar gum mixtures. Storage (G′) and loss (G′′) moduli of rice starch‐galactomannan mixtures increased with the increase in frequency (ω), while complex viscosity (η*) decreased. The magnitudes of G′ and G′′ increased with the increase in gum concentration. Dynamic rheological data of ln (G′, G′′) versus ln frequency (ω) of rice starch‐galactomannan mixtures have positive slopes with G′ greater than G′′ over most of the frequency range, indicating that their dynamic rheological behavior seems to be a weak gel‐like behavior.     

Granule Integrity and Starch Solubility During Slow,Extended Pasting of Maize Starch — the Second Viscosity Peak

Maize starch granule integrity and starch solubilisation at specific intervals during a relatively long pasting profile—which is known to exhibit biphasic peak viscosity character—was studied by microscopy and high‐performance size‐exclusion chromatography, respectively. Maize starch granules, although swelling and leaching components, remained mainly intact until the second viscosity peak when they lost integrity and formed a relatively homogenous paste. The second viscosity peak coincided with a decrease in starch content in solution and amylose going out of solution was mainly responsible for this decrease. It is suggested that the loss of granule integrity during the second viscosity peak increases the potential for amylose to form complexes with lipids at this stage. It is further suggested that the second viscosity peak is due to the formation and breakdown of superstructures of amylose‐lipid complexes.     

Some Properties of Amaranthus paniculatas (Rajgeera) Starch Pastes

The lysine rich high protein seeds of A. paniculatas (Rajgeera) are reported to contain 50–60% of waxy starch, concentrated in the endosperm. However its food related properties are comparatively unknown. In the present work, paste viscosity, paste clarity, freeze-thaw stability and effect of shear on the viscosity of A. paniculatas starch paste have been studied and compared to corn starch. Also included are the stability of Rajgeera starch paste under pressure cooking (30 min, 15 lb pressure) and acidic conditions (pH 6.98—1.76). Rajgeera starch was found to have a higher paste viscosity, lower paste clarity and high freeze-thaw stability than corn starch. Both Rajgeera and corn starch underwent thinning on being subjected to mechanical shear. Rajgeera starch withstood pressure cooking conditions admirably, but was found to be sensitive to acidic conditions.     

Steady and Dynamic Shear Rheology of Fucoidan‐Buckwheat Starch Mixtures

Rheological properties of fucoidan (F) and buckwheat starch (B) mixtures (3% or 6%) at different blending ratios of fucoidans (0, 0.1, 0.2, 0.5 and 1.0%) were investigated in steady and dynamic shear. Steady shear viscosity measurement revealed that aqueous pastes of the BF blends (3%, w/v) had a pseudoplastic and shear‐thinning behavior with flow behavior index (n) values of 0.61–0.68. The substitution of starch with fucoidan polymers significantly lowered the apparent viscosities compared with the pure starch paste and, when mixed with less than 0.5% of fucoidan, the viscosities of the pastes were even lower than those of the starch pastes at the corresponding starch concentrations. According to dynamic viscoelastic measurement performed at 6% total carbohydrate concentration, buckwheat starch mixtures behaved like weak gels and the BF blends containing less than 0.5% fucoidan had considerably lower storage (G') and loss (G') moduli than the starch paste at the corresponding starch concentrations. However, the magnitude of G' increased with fucoidan concentrations over 0.5%, suggesting that a concentration of fucoidans > 0.5% might enhance the formations of three‐dimensional networks and crosslinking of the starch samples, probably because of the mutual exclusion between starch and fucoidan polymers through the phase separation process. This study indicates that it is possible to obtain the BF blends having various rheological properties by changing the concentration of fucoidan polymers.     

Influence of prior acid treatment on physicochemical and structural properties of acetylated sorghum starch

Influence of prior acid treatment on acetylation of starch isolated from an Indian sorghum cultivar was investigated. The starch was acid thinned (AT) using 0.1, 0.5, and 1 M HCl for 1.5 h and then acetylated (Ac) with acetic anhydride (8% w/w). The acid thinning and subsequent acetylation appeared to reduce the percentage acetylation as indicated by degree of substitution. Ac‐AT starches exhibited significantly different physicochemical, thermal, pasting, and gel textural properties from those of AT and Ac starches. Starches after dual modification showed higher solubility, lower AM content, gelatinization temperatures, retrogradation, peak viscosity, and gel hardness than native starch. Enthalpy and range of gelatinization were observed to be higher in dual modified starches than native starch. However, no significant changes in granule morphology or crystalline pattern of Ac‐AT starches were observed compared with native starch.     

Resistant Starch Derived from Extruded Corn Starch and Guar Gum as Affected by Acid and Surfactants: Structural Characterization

Corn starches with and without guar gum [10% (w/w)] and 2% (w/w) of diacetyl tartaric acid ester of monoglyceride, sodium stearoyl‐2‐lactylate or citric acid, respectively, were extrusion‐cooked in a twin‐screw extruder at 18% moisture, 150 °C and 180 rpm screw speed. The content of resistant starch was determined by sequential enzymatic digestion. The formation of resistant starch in extruded corn starch was strongly affected by the addition of gum and the different food additives. X‐ray diffraction of the extruded starches gave a V diffraction pattern indicating the effect of extrusion cooking and amylose‐lipid complexes. Enzymatic digestion did not affect the V‐structure, which could apparently be attributed to extrusion cooking. Similarly, differential scanning calorimetric thermograms indicated that all isolated resistant starches exhibited endothermic transitions between 71—178 °C signifying a complex formation between amylose and the emulsifiers and possibly the melting of amylose crystallites in the resistant starch. Purification of the isolated resistant starches by size exclusion‐high performance liquid chromatography showed a dependence of molecular weight on the added additives. Results of differential scanning calorimetry and X‐ray diffraction suggest that amylose‐lipid complexes could also be involved in the formation of resistant starch in extruded cornstarch.