新型高硅奥氏体耐热不锈钢TD305B的高温抗氧化性

采用增重法研究了高硅奥氏体耐热不锈钢TD305B(/%:0.05C、3.30Si、0.80Mn、19.50Cr、13.30Ni、0.05N)和传统耐热不锈钢SUS310S(/%:0.05C、0.60Si、0.80Mn、24.60Cr、19.10Ni、0.05N)在500～1 000℃空气中氧化性能,通过扫描电镜及能谱分析(EDS)对试样表面氧化膜的形貌进行了分析。结果发现,在700～1 000℃新型高硅耐热不锈钢TD305B较传统耐热不锈钢SUS310S抗氧化性好,主要是由于TD305B钢除了在高温时基体与氧容易形成FeO·Cr₂O₃和FeCr₂O₄、NiCr₂O₄等保护性氧化膜外,还由于含有一定量的硅,在距表面20μm处形成了一层SiO₂阻止了氧化的进一步加剧,使得TD305B钢具有良好的耐高温氧化性能。     

耐溶剂聚氨酯弹性体性能之研究

采用预聚物法合成耐溶剂聚氨酯弹性体。考察了聚酯多元醇的配比、游离ω(-NCO%)含量变化以及扩链剂并用等因素对耐溶剂聚氨酯性能的影响。结果表明,随着聚酯多元醇76A用量的增加、扩链剂TIPA用量的提高,制品的力学性能和耐溶剂性能提高,TMP(三羟甲基丙烷)能有效降低制品的硬度;预聚物中游离ω(-NCO%)的含量对制品力学性能有重要影响。     

基于数值风洞的结构气动选型与风荷载计算

数值风洞模拟相对于风洞实验具有计算周期短、实施成本低的特点,并且对结构平均风荷载的模拟具有较高的精度、计算结果比实验结果更完备。数值风洞技术的以上优点使其非常适用于建筑结构前期的气动选型与优化。本文以抚顺生命之环为例,展示了数值风洞技术在结构气动选型方面的特点,并给出了最终方案的风荷载结果。     

Structural characterizations and digestibility of debranched high-amylose maize starch complexed with lauric acid

Structural characterizations and digestibility of debranched high-amylose maize starch complexed with lauric acid (LA) were studied. The cooked starch was debranched by using pullulanase and then complexed. Light microscopy showed that the lipids complexed starches had irregularly-shaped particles with strong birefringence. Gel-permeation chromatograms revealed that amylopectin degraded to smaller molecules during increasing debranching time, and the debranch reaction was completed at 12 h. Debranching pretreatment and prolonged debranching time (from 2 h to 24 h) could improve the formation of starch lipids complex. X-ray diffraction pattern of the amylose–lipid complexes changed from V-type to a mixture of B- and V-type polymorphs and relative crystallinity increased as the debranching time increased from 0 to 24 h. In DSC thermograms, complexes from debranched starch displayed three separated endotherms: the melting of the free lauric acid, starch–lipid complexes and retrograded amylose, respectively. The melting temperature and enthalpy changes of starch–lipid complex were gradually enhanced with the increasing of debranching time. However, no significant enthalpy changes were observed from retrograded amylose during the starch–lipid complex formation. Rapidly digestible starch (RDS) content decreased and resistant starch (RS) content increased with the increasing of debranching time, while the highest slowly digestible starch (SDS) content was founded at less debranching time of 2 h. The crystalline structures with dense aggregation of helices from amylose-LA complex and retrograded amylose could be RS, while SDS mostly consisted of imperfect packing of helices between amylopectin residue and amylose or LA.     

Effect of gelatinisation on slowly digestible starch and resistant starch of heat-moisture treated and chemically modified canna starches

The effects of gelatinisation on slowly digestible (SDS) and resistant starch (RS) of native and modified canna starches were investigated. Starch slurries (10% w/w) were gelatinised at 100 °C for 5, 10, 20 and 40 min using a rapid visco analyzer (RVA). Significant change in the degree of gelatinisation (DG) values of all starch samples was observed during the initial 10 min of gelatinisation; after that the DG values increased gradually with gelatinisation time. The RS contents in all gelatinised starches decreased with increasing gelatinisation time, while the SDS values fluctuated. Chemical modification affected DG values as well as RS/SDS contents. The RS contents in 10% (w/w) acetylated, hydroxypropylated, octenyl succinylated and cross-linked canna starches gelatinised at 100 °C for 40 min were 26.6%, 32.0%, 45.3% and 19.8%, respectively, which were higher than that of the native starch (12.4%). Canna starch modified by crosslinking had the highest SDS content when gelatinised for 20-40 min. Modification of canna starch by heat-moisture treatment resulted in a lower content of RS for all treated samples. However, the Vt-HMT25 (canna starch containing moisture content of 25% during heat treatment) when gelatinised for 5-20 min contained a higher amount of SDS, compared to unmodified starch. The most effective modification method for RS and SDS formation was octenyl succinylation, where the sum of RS and SDS approached that of Novelose260.     

The effect of chemically‐modified resistant starch,RS type‐4, on body weight and blood lipid profiles of high fat diet‐induced obese mice

This study was conducted to investigate the effects of feeding chemically‐modified resistant starch type‐4 (RS4) of normal (NCS) and high‐amylose corn starch (HACS) on weight gain and plasma and liver lipid profiles of mice fed a high‐fat diet (HFD). The experimental four groups were, respectively, fed following diets: A 40% HFD with NCS, HACS, NCS‐ and HACS‐RS4. A normal diet (ND) group of mice fed the standard diet was also used as control. In order to produce RS4 by chemical modification, corn starches were treated with STMP/STPP. Total RS (TRS) and total dietary fiber (TDF) levels of chemically‐modified NCS were 26.4 and 44.0%, respectively, while TRS and TDF levels in chemically‐modified HACS were 78.1 and 78.5%, respectively. Onset gelatinization temperatures of both modified corn starches clearly shifted to higher temperatures after STMP/STPP treatment. At the end of the diet trial, the mice on the HACS diet decreased body weight gain compared to the NCS‐fed mice. Adding NCS‐ and HACS‐RS4 to the diet significantly reduced the weight gain relative to NCS and HACS groups. Both RS4 diets were effective in improving the lipid profile compared to their respective controls. They significantly reduced the level of total lipid and total cholesterol.     

Resistant starch and thermal,morphological and textural properties of heat‐moisture treated rice starches with high‐, medium‐ and low‐amylose content

This study investigated the effects of heat‐moisture treatment (HMT) on the resistant starch content and thermal, morphological, and textural properties of rice starches with high‐, medium‐ and low‐amylose content. The starches were adjusted to 15, 20 and 25% moisture levels and heated at 110°C for 1 h. The HMT increased the resistant starch content in all of the rice starches. HMT increased the onset temperature and the gelatinisation temperature range (T_finish–T_onset) and decreased the enthalpy of gelatinisation of rice starches with different amylose contents. This reduction increased with the increase in the moisture content of HMT. The morphology of rice starch granules was altered with the HMT; the granules presented more agglomerated surface. The HMT affected the textural parameters of rice starches; the high‐ and low‐amylose rice starches subjected to 15 and 20% HMT possessed higher gel hardness.     

Resistant starch type 4‐enriched diet lowered blood cholesterols and improved body composition in a double blind controlled cross‐over intervention

A metabolic health crisis is evident as cardiovascular diseases (CVD) remain the leading cause of mortality in the United States. Effects of resistant starch type 4 (RS4), a prebiotic fiber, in comprehensive management of metabolic syndrome (MetS) remain unknown. This study examined the effects of a blinded exchange of RS4‐enriched flour (30% v/v) with regular/control flour (CF) diet on multiple MetS comorbidities. In a double blind (participants–investigators), placebo‐controlled, cluster cross‐over intervention (n = 86, age≥18, 2–12 week interventions, 2‐week washout) in the United States, individuals were classified as having MetS (With‐MetS) or not (No‐MetS) following International Diabetes Federation (IDF)‐criteria. RS4 consumption compared with CF resulted in 7.2% (p = 0.002) lower mean total cholesterol, 5.5% (p = 0.04) lower non‐HDL, and a 12.8% (p < 0.001) lower HDL cholesterol in the With‐MetS group. No‐MetS individuals had a 2.6% (p = 0.02) smaller waist circumference and 1.5% (p = 0.03) lower percent body fat following RS4 intervention compared to CF. A small but significant 1% increase in fat‐free mass was observed in all participants combined (p = 0.02). No significant effect of RS4 was observed for glycemic variables and blood pressures. RS4 consumption improved dyslipidemia and body composition. Incorporation of RS4 in routine diets could offer an effective strategy for public cardio‐metabolic health promotion.     

香蕉膳食纤维的研究进展

概述香蕉膳食纤维（DF）的成分及功能，着重介绍其中的抗性淀粉，比较3种香蕉DF的含量以及贮藏过程中蕉皮DF的变化情况，简介香蕉膳食纤维的加工现状。