高压对玉米淀粉糊化特性的影响

本文采用ＤＳＣ法研究了玉米淀粉经４００ＭＰａ以下的高压处理后，其糊化特性的变化。处理压力越高，保压时间越长，则糊化温度降低越大。４００ＭＰａ处理３０ｍｉｎ，糊化温度降低２．３７℃，糊化焓则在３００ＭＰａ，３０ｍｉｎ的出现最低点。     

超高压处理对玉米淀粉结构及糊化特性的影响

利用光学显微、X-射线衍射、差示扫描量热、快速黏度分析技术研究了超高压处理对玉米淀粉结构及糊化性质的影响。结果显示,超高压处理能使玉米淀粉糊化,处理压力为500 MPa及600 MPa时完全糊化所需保压时间分别为15 min和5 min,但400 MPa超高压处理30 min也不会使淀粉糊化。超高压糊化过程中,淀粉颗粒结构逐渐破坏膨胀,结晶结构由A型向V型转化,RVA黏度曲线峰值黏度逐渐消失。适宜条件的超高压处理对淀粉颗粒同时具有韧化和晶体破坏作用。其中,400 MPa超高压处理5~10 min时,淀粉颗粒内部韧化作用占优,因而表现为相对结晶度、糊化温度(T_o,T_p)及糊化焓增加,而RVA曲线峰值黏度降低。     

纳米纤维素对普通玉米淀粉糊化特性和流变特性的影响

透射电子显微镜图表明,纳米纤维素为棒状,直径小于10 nm,长度在100~500 nm。快速黏度分析仪(RVA)分析表明,纳米纤维素添加量为5%~20%时,普通玉米淀粉的糊化温度无明显改变,峰值黏度、谷值黏度、末值黏度和衰减值均随着纳米纤维素添加量的增加而升高。研究结果表明:普通玉米淀粉糊具有假塑性流体的特征,属"剪切变稀"体系。纳米纤维素添加量增加,普通玉米淀粉糊的表观黏度增加,体系稠度增大,淀粉糊的流动性降低。纳米纤维素可改变普通玉米淀粉胶的三维网络结构,使得体系被破坏后的回复力减弱。     

支链淀粉含量对玉米淀粉浆料糊化和结晶性能的影响

将支链淀粉加入到玉米淀粉中组成混合纺织浆料,采用RVA和XRD研究了支链淀粉含量对淀粉浆料流变性以及结晶性能的影响。结果表明：随着支链含量的增加,淀粉浆液的峰值粘度、谷值粘度、末值粘度逐渐降低,衰减值和回生值也逐渐变小,达到峰值的时间缩短,加入支链淀粉有利于淀粉糊化和浆液稳定;同时,淀粉膜的结晶度随支链淀粉含量增加而减小,晶体尺寸呈增长趋势。     

萌发玉米淀粉的糊化特性及其对面包品质的影响

研究了萌发玉米淀粉的糊化特性及对面包品质的影响。结果表明,与原淀粉相比,萌发玉米淀粉的糊化温度有所降低,糊化时间有所缩短。5种面包样品的仪器测定和消费者实验表明,添加适量的萌发玉米淀粉能够有效提高面包质地特性和总体接受程度、口感、外观、气味等特征。     

萌发玉米淀粉的糊化特性及其对面包品质的影响

研究了萌发玉米淀粉的糊化特性及对面包品质的影响。结果表明,与原淀粉相比,萌发玉米淀粉的糊化温度有所降低,糊化时间有所缩短。5种面包样品的仪器测定和消费者实验表明,添加适量的萌发玉米淀粉能够有效提高面包质地特性和总体接受程度、口感、外观、气味等特征。      

玉米淀粉糊化质量的控制

本文阐述了糖化过程中使用玉米淀粉为辅料的糊化质量控制及常见问题的处理,以供参考。     

β-环糊精对玉米淀粉糊化特性的影响

基于β-环糊精（β-CD）对淀粉回生的抑制机理作用,利用淀粉黏度仪及红外光谱仪研究了β-CD对玉米淀粉糊化特性的影响,以期为淀粉类食品的生产提供参考。结果表明：一定量的β-CD能够显著降低淀粉的回生值和结晶度,增加冷糊黏度和冷糊稳定性;β-CD与淀粉之间未产生化学反应,主要是范德华力、氢键力和静电力的相互作用,并不涉及共价键的断裂与生成。     

老化处理对玉米中淀粉含量及其糊化与消化特性的影响

通过对玉米进行老化处理,模拟老化后的生理状态,研究其淀粉含量、淀粉酶活性、淀粉糊化特性及消化性变化规律对人工老化处理的响应,以期为玉米淀粉应用及玉米合理储藏提供理论参考.以郑单958、伟科702、浚单29为材料,采用高温高湿(42℃、100％RH)人工老化的方法,分析玉米淀粉含量、总淀粉酶活性、α-淀粉酶活性、淀粉去分...     

郑单958与先玉335玉米籽粒淀粉粒分布的比较

以郑单958及先玉335玉米为材料,利用激光衍射粒度分析仪及扫描电镜,分析玉米籽粒淀粉粒形态及分布特征。结果表明,两品种籽粒淀粉粒体积分布均为三峰曲线,峰值分布均在1.919,5.355及18.00μm;两品种籽粒淀粉粒表面积分布为三峰曲线,其峰值分别为1.322(1.097),5.355及16.40μm;郑单958、先玉335籽粒淀粉粒数目分布为双峰曲线,其峰值分别为0.627(0.688)及4.878(4.444)μm。两玉米品种>15μm所占体积最大,而<2μm淀粉粒所占体积最小; <2μm淀粉粒所占表面积及数目均最高,>15μm淀粉粒所占数目最小。郑单958及先玉335淀粉粒分布范围分别为0.375-39.78,0.375-30.07μm;淀粉粒体积及表面积均值均是先玉335>郑单958,而淀粉粒数目均值则是郑单958>先玉335。淀粉粒含量与2-15μm范围的淀粉粒体积和数目呈显著正相关,和其他淀粉粒分布特性相关性不显著。郑单958玉米籽粒淀粉粒呈圆形或椭圆形,大小不均匀,淀粉粒排布致密,脂体含量丰富;先玉335大多呈圆形,大小均匀,淀粉粒排布分布较郑单958稀疏,脂体含量少于郑单958。     

不同基因型玉米籽粒发育过程中糖代谢相关酶活性的比较

对高淀粉玉米与低淀粉玉米籽粒发育过程中蔗糖代谢和淀粉合成相关酶活性的变化动态进行了比较研究。结果表明,费玉3号籽粒支链淀粉、直链淀粉及总淀粉积累速率高于豫玉22;费玉3号籽粒支链淀粉、直链淀粉及总淀粉含量大于豫玉22;豫玉22的高峰黏度、低谷黏度、最终黏度及胶凝值均显著高于费玉3号,其崩解值和糊化温度低于费玉3号;豫玉22的可溶性糖含量高于费玉3号;费玉3号的腺苷二磷酸葡萄糖焦磷酸化酶(ADPG-PPase)活性、尿苷二磷酸葡萄糖焦磷酸化酶(UDPG-Ppase)活性、可溶性淀粉合成酶(SSS)活性、束缚态淀粉合成酶(GBSS)活性高于豫玉22。     

Physicochemical,thermal, and pasting properties of flours and starches of eight Brazilian maize landraces (Zea mays L.)

Both genetic and environmental factors create significant variation in the amount and quality of maize landrace constituents. Details on the flours and starch characteristics have not been fully investigated. The physicochemical, pasting and thermal properties of 8 promising cultivars were assessed in this study and those properties were correlated. Higher values of swelling and solubility (RJ – 13.14%; 14.39%), lipid content (MG – 5.53%), WBC (PR – 18.89%), and amylose content (PR – 27.43%) were found for those genotypes. Lower onset temperatures of gelatinization (To) were observed for RX-F1 (66.1 °C) as RX-F1 (68.7 °C) genotype showed the lower pasting temperatures. A wide range of viscosity values was found among the maize landraces (MG-F0, 343 mPa s and RJ-F1, 175 mPa s) as well as for the retrogradation (R8C-F1, 796 mPa s and RX-F1, 22 mPa s). ATR-FTIR spectroscopy revealed amylose, amylopectin, lipids, and proteins as major flours constituents and their differences were discriminated by PCA analysis.     

Interrelationship of nitrogen nutrition with maize (Zea mays) grain yield,nitrogen use efficiency and grain quality

Eight maize (Zea mays L) hybrids were grown under five N levels with or without the nitrification inhibitor, nitrapyrin (2-chloro-[6-trichloro-methyl] pyridine), to evaluate N interactions relative to yield performance, N use efficiency, grain protein concentration, and kernel texture. Results indicate that maize hybrids can be grouped into three categories based on grain yield: (1) low N-responsive types which reach their maximum yield with 134 kg ha^?1 of applied N; (2) intermediate types that respond to moderate N levels (134 to 201 kg N ha^?1); and (3) high N-responsive types that respond to higher levels of N (201 kg N ha^?1). High N-responsive types, in general, increased yield with nitrapyrin treatment at all levels of N. Crop N utilisation efficiency for high N-responsive hybrids decreased, but was static for low N-responsive hybrids as N fertiliser increased. In general, as the grain yield of a hybrid increased in response to N, the concentration of protein in the kernel increased; although grain yields and protein concentration are negatively correlated among hybrids. Increased kernel translucence, an indicator of kernel hardness induced by N fertiliser, correlated highly positive with zein proteins. Isoelectric focusing analysis showed that increases in zein were primarily due to a quantitative increase in α- and γ-zein polypeptides. This study indicates that hybrids are different in their N requirements for maximum yield. Low N conditions not only restrict grain yield but also affect kernel textural quality.     

Pasting and rheologic properties of potato starch and maize starch mixtures

This study characterized the pasting and rheologic behavior of potato/maize starch mixtures of various ratios. Pasting analysis using a Brabender Viscograph indicated that most important pasting parameters did not show a linear change that reflected the ratio of starches. A significant effect on final viscosities and setback was evident. The diameter distribution of starch granules that were heated to 70°C was determined by a laser particle size analyzer. The result suggested that the swelling of starch granules in the mixtures was reduced at the onset of gelatinization. Measurement of dynamic viscoelasticity measurement demonstrated that the mixtures showed slightly higher loss modulus than those seen for the control at small measuring frequencies. The mixture pastes with a high proportion of potato starch exhibited more pseudoplasticity and had a more significant thickening effect than either control paste. Nonadditive behavior was found by mixing potato and maize starch. This suggests that an appropriate blend of starches from diverse botanical origins may provide a simple practical avenue for manipulation.     

The effect of rice variety and starch isolation method on the pasting and rheological properties of rice starch pastes

The effect of rice variety and starch isolation method on the pasting and rheological properties of rice starches was evaluated. One waxy and three non-waxy rice varieties from California with a range of amylose contents of 1.6–26.5% and four methods of isolation were evaluated. A rotational rheometer (RR) was used to measure the pasting and rheological properties of starch dispersions (8% w/w). The RR pasting curves had similar shapes to those from a rapid visco-analyzer (RVA). The four treatments used for isolating starch were a protease, NaOH (0.1% and 0.4%), or sodium dodecyl sulfate (SDS) (1.0%). The NaOH (0.4%) and SDS treatments were found to reduce the peak pasting temperatures of the non-waxy starches as compared with the protease and NaOH (0.1%) treatments. The same trend of the treatments was found with the elastic moduli, low shear viscosities, and yield stresses of the non-waxy starch pastes measured at 65 °C, immediately after pasting. The elastic moduli of the waxy starch pastes appeared to be least affected by method of starch isolation, but the low shear viscosity and yield stress of the protease starch paste was significantly higher than the paste from the other three treatments. Overall, the method of rice starch isolation was found to affect the gelatinization and rheological characteristics of hot rice starch paste.     

Sugar and Soluble Solids Changes in Refrigerated Sweet Corn (Zea mays L)

Three sweet corn (Zea mays L) genotypes, one cultivar each, were tested for sugar and soluble solids changes at 6°C for 5 days. Genotypes and cultivars were sugary (su), ‘Silver Queen’; sugary enhanced (se), ‘Incredible’ and super sweet (sh 2), ‘How Sweet It Is.’ Fructose, glucose, sucrose, maltose, total sugars and °Brix were measured. Sucrose predominated. Generally, °Brix, fructose, glucose and sucrose decreased and maltose increased, sh 2 had lowest °Brix and highest sucrose and total sugars, and su had highest °Brix and lowest sucrose and total sugars, su consisted of 3.8% total sugars (DWB); se, 7.2% and sh 2, 10.9%. Overall correlation coefficient between °Brix and total sugars was ?0.99.     

Accumulation of phenolics,antioxidant and antiproliferative activity of sweet corn (Zea mays L.) during kernel maturation

Phenolic profiles and gene expression pattern in their synthetic pathway, total antioxidant activities and antiproliferative activities in two genotypes of sweet corn (YT16 and YT28) during kernel maturation were analysed. Results showed that increasing trends of phenolics and flavonoids in the two genotypes of kernels from 10 to 30 days after pollination (DAP). Gallic acid, chlorogenic acid, p-coumaric acid and ferulic acid were identified and quantified as the main phenolic compounds in both genotypes of kernels. High expressing levels of C4O and PAL resulted in the increasing phenolic contents. Higher expressing levels of CHS in YT28 led to higher flavonoid contents than that in YT16. The phenolic contents, antioxidant capacities and antiproliferative abilities of the two genotypes of sweet corn were competitive comparing to many fruits and vegetables. In addition, the maturation process of sweet corn could raise the kernel’s bioactive ability as well as nutritional values.