拔节期追氮对鲜食糯玉米粉糊化和热力学特性的影响

以苏玉糯1号、苏玉糯5号和渝糯7号为材料,研究了拔节期追氮量（N 0、150和300 kg/hm2）对鲜食糯玉米粉糊化和热力学特性的影响。结果表明,随着拔节期追氮量的增加,峰值黏度和崩解值下降,糊化温度升高,而谷值黏度、终值黏度和回复值呈先降后升趋势; 热力学特征参数中,回生值、终值温度、糊化范围和峰值指数受拔节期追氮量影响较小。原样品热焓值和回生后样品热焓值均表现为随着拔节期追氮量的增加呈先降后升趋势。糊化和热力学特征值对拔节期追氮量的响应不同品种间存在差异。鲜食糯玉米粉的理化特性存在显著的基因型差异,峰值黏度以苏玉糯5号最高,苏玉糯1号最低; 峰值温度苏玉糯1号和苏玉糯5号无显著差异,但均高于渝糯7号; 热焓值、回生值、糊化范围和峰值指数不同品种间相对稳定。相关分析表明,峰值黏度与原样品热焓值和峰值指数呈显著正相关; 崩解值与糊化温度及转变温度,回生值与淀粉的终值黏度和回复值呈显著负相关。在本试验条件下,拔节期追氮总体上使糯玉米食用品质降低,其中以苏玉糯5号在不追氮处理下的糊化和热力学特性较优,即峰值黏度、崩解值和热焓值较高,回生值较低。     

播期对夏播糯玉米淀粉理化特性的影响

为明确夏播糯玉米的适宜播期,以苏玉糯5号和渝糯7号为材料,分析了播期对夏播糯玉米籽粒淀粉理化特性的影响。结果表明,2014年度2个糯玉米品种的淀粉平均粒径在早播和迟播处理下均显著降低,2013年度苏玉糯5号在早播处理下较高,渝糯7号受播期影响较小。播期对糯玉米淀粉的晶体衍射类型无影响,但使尖峰强度发生了变化。淀粉碘结合力随播期推迟逐渐降低,糊化范围在早播和迟播处理下均显著降低。淀粉最大吸收波长、糊化温度、胶凝温度(起始温度、峰值温度和终值温度)受播期影响较小。淀粉膨胀势、黏度特征值、热焓值和回生值在不同播期处理下均发生了变化。相关分析结果表明,生育期较高的积温增加了支链淀粉中长链比例,使谷值黏度升高;降雨量过多易导致淀粉膨胀势下降,热焓值降低;较长的日照时数增加了支链淀粉中长链比例,使淀粉膨胀势、谷值黏度和热焓值升高。因此,在夏播糯玉米生产中,应根据气候条件和生产目标确定适宜播期,提高黏度应提早播种,降低回生应推迟播种。本研究结果为夏播糯玉米淀粉品质调优提供了理论依据。     

缓释肥施用时期对春播鲜食糯玉米产量和籽粒品质的影响

为探明缓释肥施用时期对鲜食糯玉米产量和籽粒品质的影响,本研究以苏玉糯11号为材料,在等量施肥条件下,以常规施肥方式(N15CK,基施复合肥+六叶期追施尿素)和不施肥为对照,研究缓释肥于播种期(SN15-0)、三叶期(SN15-3)和六叶期(SN15-6)一次性施用对鲜食糯玉米鲜果穗和鲜籽粒产量,籽粒淀粉和蛋白质含量、碘结合力、热力学特性和糊化特性的影响。结果表明,缓释肥处理的鲜果穗产量和鲜籽粒产量显著高于常规肥处理,且SN15-6和SN15-3的鲜果穗产量分别比SN15-0提高14.0%和7.4%,鲜籽粒产量提高14.6%和2.0%。SN15-6的籽粒中淀粉、可溶性糖和蛋白质含量均显著高于其他处理。缓释肥延后施用使淀粉粒径变小,SN15-6与N15CK的淀粉碘结合力和最大吸收波长显著高于其他处理。与不施肥相比,施肥提高了籽粒淀粉的糊化温度和胶凝温度(起始温度、峰值温度和终值温度),降低了回生热焓值和回生值。其中SN15-3的峰值黏度、谷值黏度、崩解值和终值黏度最高,而SN15-6的回复值、回生热焓值和回生值最低。综上,缓释肥适当延后施用有利于提高鲜食糯玉米产量,增加籽粒中蛋白质、淀粉、可溶性糖含量,降低淀粉平均粒径;另外,三叶期施用可显著提高籽粒糊化黏度,六叶期施用使籽粒回生值显著降低。本研究结果可为春播鲜食糯玉米绿色高产优质轻简栽培提供理论依据与技术支撑。     

鲜食糯玉米籽粒理化特性的基因型差异

以糯玉米国家区域试验14个品种为材料,研究其鲜食期籽粒理化特性的基因型差异。结果表明,鲜食糯玉米籽粒理化特性存在显著的基因型差异,淀粉和蛋白质含量变幅分别在48.7%~72.2%和7.4%~8.9%之间,但其含量高低对籽粒理化特性无显著影响。籽粒淀粉最大吸收波长变幅在531.6~559.4nm之间,但总体上变异较小,且均表现出典型的糯性特征。碘结合力和微量元素含量均存在显著的基因型差异。差示扫描量热仪(DSC)和快速黏度分析仪(RVA)研究表明,供试品种中淮科糯3号和禾盛糯1512黏度特征值较优,适合作鲜穗食用;禾盛糯1512和沈糯062回生值较低,在速冻玉米上具有独特优势。相关分析表明,碘结合力与回生值显著负相关,与回复值显著正相关。微量元素中,Cu、Fe、Ca、Na元素含量与热力学特征值和糊化特征值无显著相关性,Mn、Zn、S和P元素含量与峰值黏度和崩解值显著负相关,K与崩解值显著正相关,S与糊化温度显著正相关。     

氮肥施用量对甘薯产量和品质性状的影响

【目的】氮是影响作物产量和品质性状的重要因素,合理施氮是提高作物产量和改善品质的主要途径。研究施氮量对甘薯块根产量形成、营养品质和淀粉糊化特性的影响,对于明确江苏徐淮地区甘薯种植的适宜施氮量具有重要意义。【方法】本文选用淀粉型甘薯品种徐薯22和兼用型甘薯品种徐薯28为试验材料,设置5个施氮水平0、60、120、180、240 kg/hm2。调查了甘薯不同生育期的叶面积指数、光合势、干物质积累和产量构成要素,采用分光光度法测定了块根主要营养品质指标,利用Tech-master型RVA快速测定淀粉谱粘滞特性,分析明确施氮量对块根主要品质指标和淀粉糊化特征值的影响。【结果】施氮N 60 kg/hm2增加了各生育期甘薯的叶面积,提高了甘薯的光合势,显著增加了块根产量(徐薯28增产16.38%,徐薯22增产9.31%),过量施氮(N 240 kg/hm2)则产量降低。施氮并未显著降低块根中的淀粉和直链淀粉含量,但明显增加了可溶性糖和蔗糖含量。施氮显著提高最高粘度、最低粘度、最终粘度和消减值。相关分析显示,直链淀粉含量与最高粘度值和崩解值呈极显著或显著负相关(相关系数分别为-0.90**和-0.71*);直链淀粉含量与消减值呈显著正相关(相关系数为0.73*)。【结论】综合考虑甘薯的产量和品质,在本实验条件下甘薯较为适宜的氮肥用量约为60 kg/hm2。     

粳稻粒位间淀粉RVA谱特征与其它品质性状的关系

为了明确RVA谱特征值在评价稻米品质中的作用,本文选用不同穗型水稻为材料,按照穗部位置分为27个粒位,研究了不同粒位上淀粉RVA谱特征与其它品质性状的关系。结果表明碾米品质中的整精米率和粒长与峰值黏度、热浆黏度和崩解值3个特征值有极显著正相关关系。外观品质中的垩白率、垩白度和营养品质中的总蛋白质含量、清蛋白含量、醇溶蛋白含量、谷蛋白含量、脂肪酸含量都与峰值黏度、热浆黏度、崩解值呈极显著负相关,与消减值极显著正相关;球蛋白含量则表现相反规律。蒸煮食味品质中的食味值、直链淀粉含量和胶稠度与峰值黏度、热浆黏度、崩解值3个特征参数呈极显著正相关,与消减值呈极显著负相关,尤其是与峰值黏度和崩解值2个参数的相关系数较大。淀粉RVA谱特征值能密切反映稻米品质的好坏,穗下部二次枝梗籽粒的峰值黏度和崩解值的大小可以作为优质粳稻辅助选择的首选指标。     

垄沟集雨覆盖对旱作马铃薯块茎淀粉颗粒形态、颗粒分布及糊化特性的影响

为探讨垄沟集雨覆盖栽培对旱作马铃薯块茎形成过程中淀粉颗粒形态、颗粒分布及糊化特性的影响,以马铃薯栽培品种青薯9号为材料,设置全膜双垄(M2)和地膜垄作(M1)覆盖栽培模式,以露地平播为对照(M0),采用扫描电镜、激光粒度仪、粘度分析仪,测定马铃薯块茎形成过程中淀粉的颗粒形态、分布及糊化特性指标。结果表明,从块茎发育全程来看,全膜双垄覆盖栽培模式下马铃薯块茎淀粉颗粒的平均粒径、峰值粘度、低谷粘度及最终粘度整体较高;地膜垄作覆盖栽培模式下马铃薯块茎淀粉颗粒的离散度、崩解值、回生值整体较高;各栽培模式间马铃薯块茎淀粉颗粒形态、糊化温度无显著差异;马铃薯淀粉颗粒的平均粒径与各阶段粘度呈显著正相关,与糊化温度呈显著负相关,与崩解值、回生值无显著相关性;马铃薯淀粉颗粒的离散度与淀粉的糊化特性各指标均无显著相关性。综上,全膜双垄覆盖栽培模式所产生的淀粉品质较好。     

水稻心白突变体xb1的淀粉理化特性分析

淀粉是稻米胚乳的主要成分,解析其理化特性对改良水稻品质具有十分重要的意义。为了探究心白稻米淀粉的理化特性,本研究以经EMS诱导粳稻品种辽星1号获得的心白突变体xb1为材料,利用扫描电镜、激光粒度分析仪、RVA快速黏度分析仪、差示扫描量热仪等方法,对形态结构、淀粉颗粒结构和粒径分布、糊化特性及热力学特性等进行了分析。结果表明,与野生型相比,突变体xb1籽粒的粒宽、粒厚和千粒重均显著降低;淀粉结构和淀粉粒粒径分布均发生改变,淀粉粒粒径值大于13左右的淀粉粒数量明显低于野生型;突变体种子中蛋白质含量极显著高于野生型,总淀粉含量极显著低于野生型,而直链淀粉含量没有明显改变;在支链淀粉分支结构上,聚合度(DP)在6~9之间的短链及25~35之间的中长链比例有所增加,而DP值在10~24之间的中短链及36~50之间的长链比例有所减少;突变体xb1淀粉的糊化起始温度(To)、峰值温度(Tp)、终止温度(Tc)和糊化距离(Tr)均未发生明显改变,只有热焓值(△H)极显著提高。同时,突变体xb1的RVA谱特征值中,热浆黏度(HPV)、峰值黏度(PKV)、冷胶黏度(CPV)和消减值(SBV)极显著提高,崩解值(BDV)和回复值(CSV)极显著降低。本研究结果为探索垩白形成的生理机制以及进一步的基因克隆奠定了基础。     

挤压体系中可得然胶对小麦淀粉回生特性和冻融稳定性的影响

小麦淀粉的回生现象和较差的冻融稳定性是限制面制品加工的重要原因。为探索一种有效抑制小麦淀粉回生及改善其冻融稳定性的方法，该文研究了挤压体系中不同质量分数的可得然胶对小麦淀粉回生特性和冻融稳定性的影响，利用差示扫描量热仪、X-射线衍射和傅里叶红外光谱等技术表征了可得然胶-小麦淀粉复合物的分子结构，并结合化学试剂处理、质构仪和扫描电镜探讨了可得然胶与小麦淀粉的结合机制。结果表明：随着可得然胶浓度的增加，可得然胶-小麦淀粉复合物的回生值和析水率先降低后增加；与挤压小麦淀粉相比，添加质量分数0.6%的可得然胶能够显著提高小麦淀粉的糊化温度，并降低小麦淀粉的相对结晶度、短程有序性和碘结合力，抑制了直链淀粉的重结晶；挤压体系中可得然胶与小麦淀粉主要通过氢键和弱的静电相互作用结合，使小麦淀粉的结构更加致密，从而抑制小麦淀粉的回生并改善其冻融稳定性，该研究可为开发抗回生和低析水率的挤压小麦淀粉基食品提供参考。     

马铃薯糊化过程中介电特性和热特性的分析(简报)

该文采用介电特性测定仪(DES100)和示差扫描量热仪(DSC120)对马铃薯片(含水率80.7%,淀粉含量16.5%)介电特性和热特性进行了比较研究,以确定马铃薯淀粉糊化过程中各特征参数值之间的关系。由介电特性曲线得出:在1～100kHz频率范围内的,65～80℃温度范围内,介电常数e′随温度的升高出现跃变型变化,67℃时变化速率最大,之后逐渐下降;由热吸收曲线得出热焓值的变化与e′变化规律相同,其糊化的3个特征温度(糊化起始、峰值、结束)分别是65、67和80℃,从两曲线得到的各特征值基本一致,说明利用马铃薯的介电特性和热特性的综合分析可以更准确地掌握其糊化过程,为进一步利用和控制马铃薯的糊化作用提供参考。     

Effects of Waterlogging Around Flowering Stage on the Grain Yield and Eating Properties of Fresh Waxy Maize

The effects of waterlogging around flowering stage on the grain yield and eating quality of fresh waxy maize were studied using Suyunuo5 and Yunuo7 as materials in 2014 and 2015. Waterlogging around flowering stage decreased the fresh weight, volume, and number of grains, which led to the loss of fresh grain yield. Waterlogging before pollination reduced grain moisture content and increased grain dry weight. Waterlogging increased starch contents and decreased protein contents, especially after pollination; decreased albumin and glutenin contents; and did not affect globulin content. Zein content was decreased and increased, respectively, by waterlogging before and after pollination. The responses of starch granule size and iodine‐binding capacity to waterlogging were dependent on planting year, variety, and waterlogging stage. Pasting and gelatinization temperatures were only slightly affected by waterlogging. Waterlogging increased peak viscosity at both stages in Suyunuo5, but this parameter decreased and increased, respectively, before and after pollination in Yunuo7. Waterlogging did not affect gelatinization enthalpy but increased retrogradation enthalpy and percentage. In conclusion, waterlogging around flowering stage suppressed grain yield and shortened grain filling duration. Eating quality (viscosity and retrogradation) was also altered by waterlogging because grain proximate content and starch granule structure were changed.     

Quality Characteristics of Waxy Hexaploid Wheat (Triticum aestivum L.): Properties of Starch Gelatinization and Retrogradation

The viscoelastic properties and molecular structure of the starch isolated from waxy (amylose-free) hexaploid wheat (WHW) (Triticum aestivum L.) were examined. WHW starch generally had lower gelatinization onset temperature, peak viscosity, and setback than the starch isolated from normal hexaploid wheat (NHW). Differential scanning calorimetry (DSC) showed that WHW starch had higher transition temperatures (T_o, T_p, and T_c) and enthalpy (ΔH) than NHW starch. However, when compared on the basis of amylopectin (AP) content, ΔH of WHW starch was almost statistically identical to that of its parental varieties. Typical A-type X-ray diffraction patterns were observed for the starches of WHW and its parental varieties. Somewhat higher crystallinity was indicated for WHW starch. WHW starch was also characterized by having greater retrogradation resistance. The high-performance size-exclusion chromatography (HPSEC) of amylopectin showed that each amylopectin yielded two fractions after debranching. Although WHW amylopectin had somewhat long B chains, little difference was observed in the ratio of Fr.III/ Fr.II between WHW and its parental varieties.     

Retrogradation of Rice Flour Gel and Dough: Plasticization Effects of Some Food Additives

Certain food additives commonly used in flour products also have a plasticization effect on product shelf life regarding retrogradation. Sucrose, sorbitol, glycerol, citric acid, and acetic acid at 25, 25, 25, 0.5, and 0.5%, respectively, were added to two different starch gel systems: slurry (high‐amylose rice flour gel) and dough (waxy rice flour dough). All plasticizers increased gelatinization temperature, decreased enthalpy (ΔH), and promoted a more homogeneous system. Sucrose had the greatest effect on gelatinization increase. Rice dough was more susceptible to plasticizers, resulting in higher moisture content and a more amorphous structure. Retrogradation was highly positively correlated with amylose content, moisture retention, ratio of protons of water/starch, and previous occurrence of retrogradation. Moisture retention was increased in plasticizer‐added samples, especially waxy rice dough. Over a longer storage period, sucrose and sorbitol showed an antiplasticization effect in waxy rice flour dough, but glycerol and acid caused higher retrogradation in high‐amylose rice flour gel.     

Thermal Properties of Starch from 62 Exotic Maize (Zea mays L.) Lines Grown in Two Locations

The variability in thermal properties among 62 S₃ lines derived from a high-yielding exotic corn (Zea mays) population, Antigua 1 (PI 484990), was evaluated by differential scanning calorimetry (DSC). The S₃ lines were grown in Puerto Rico (1990–1991) and Georgia (1994). Separate single-kernel starch extractions for five kernels (five replicates) from each line grown in each location were performed, and the starch was analyzed. The DSC values reported included gelatinization onset (T_oG), range (R_G), enthalpy (ΔH_G), and peak height index (PHI) and retrogradation onset (T_oR), range (R_R), enthalpy (ΔH_R), and percent retrogradation (%R) (an indication of the stability of gelatinized starch after storing at 4°C for 7 days). Significant differences (P < 0.05) were found among the 62 lines of Antigua 1 for T_oG, R_G, and PHI and highly significant differences (P < 0.01) were found for ΔH_G. The starches from plants grown in Georgia (1994) had significantly (P < 0.05) greater T_oG, ΔH_G, and PHI but a significantly lower R_G than those from Puerto Rico (1990–1991). These data suggest that the starch from plants grown in Georgia (1994) might have a greater degree of crystallinity than that from Puerto Rico (1990–1991). None of the retrogradation values were significantly different among starches of the 62 lines of Antigua 1 and the starches from plants grown in the two locations.     

Effect of Sucrose on Glass Transition,Gelatinization, and Retrogradation of Wheat Starch

Differential scanning calorimetry (DSC) was used to study the effect of sucrose on wheat starch glass transition, gelatinization, and retrogradation. As the ratio of sucrose to starch increased from 0.25:1 to 1:1, the glass transition temperature (T_g, T_g′) and ice melting enthalpy (ΔH_ice) of wheat starch‐sucrose mixtures (with total moistures of 40–60%) were decreased to a range of −7 to −20°C and increased to a range of 29.4 to 413.4 J/g of starch, respectively, in comparison with wheat starch with no sucrose. The T_g′ of the wheat starch‐sucrose mixtures was sensitive to the amount of added sucrose, and detection was possible only under conditions of excess total moisture of >40%. The peak temperature (T_m) and enthalpy value (ΔH_G) for gelatinization of starch‐sucrose systems within the total moisture range of 40–60% were increased with increasing sucrose and were greater at lower total moisture levels. The T_g′ of the starch‐sucrose system increased during storage. In particular, the significant shift in T_g′ ranged between 15 and 18°C for a 1:1 starch‐sucrose system (total moisture 50%) after one week of storage at various temperatures (4, 32, and 40°C). At 40% total moisture, samples with sucrose stored at 4, 32, and 40°C for four weeks had higher retrogradation enthalpy (ΔH) values than a sample with no sucrose. At 50 and 60% total moisture, there were small increases in ΔH values at storage temperature of 4°C, whereas recrystallization of samples with sucrose stored at 32 and 40°C decreased. The peak temperature (T_p), peak width (δT), and enthalpy (ΔH) for the retrogradation endotherm of wheat starch‐sucrose systems (1:0.25, 1:0.5, and 1:1) at the same total moisture and storage temperature showed notable differences with the ratio of added sucrose. In addition, T_p increased at the higher storage temperature, while δT increased at the lower storage temperature. This suggests that the recrystallization of the wheat starch‐sucrose system at various storage temperatures can be interpreted in terms of δT and T_p.     

Comparative study of the retrogradation of intermediate water content waxy maize, wheat, and potato starches

The retrogradation of extruded starches from three different botanical sources was studied in concentrated conditions (34 +/- 1% water) at 25 degrees C using differential scanning calorimetry (DSC) and isothermal calorimetry, Fourier transform infrared spectroscopy (FTIR), and wide-angle X-ray scattering. Potato starch showed the highest rate of retrogradation (approximately 0.17 h(-1)) followed by waxy maize (approximately 0.12 h(-1)), while the retrogradation of wheat starch was the slowest (approximately 0.05 h(-1)). In addition to the kinetics, the extent of molecular order in the retrograded samples was studied in detail in terms of "short-range" (helical) and "long-range" (crystalline) distance scales. The amylopectin crystallinity indices were essentially the same (approximately 47-51% amylopectin basis) for the three starches. However, significant differences were found in the enthalpy of melting measured by DSC after "full" retrogradation (potato, 11.6 +/- 0.7; waxy maize, 9.0 +/- 0.5; and wheat, 6.1 +/- 0.3 J/g of amylopectin). The degree of short-range molecular order in the retrograded state determined by FTIR was waxy maize > potato > wheat. The effect of amylopectin average chain length and the polymorphism of the crystalline phase were taken into account to explain the differences in the retrogradation enthalpies.     

Structure and Functionality of Barley Starches

Amylose contents of prime starches from nonwaxy and high-amylose barley, determined by colorimetric method, were 24.6 and 48.7%, respectively, whereas waxy starch contained only a trace (0.04%) of amylose. There was little difference in isoamylase-debranched amylopectin between nonwaxy and high-amylose barley, whereas amylopectin from waxy barley had a significantly higher percentage of fraction with degree of polymerization < 15 (45%). The X-ray diffraction pattern of waxy starch differed from nonwaxy and high-amylose starches. Waxy starch had sharper peaks at 0.58, 0.51, 0.49, and 0.38 nm than nonwaxy and high-amylose starches. The d-spacing at 0.44 nm, characterizing the amylose-lipids complex, was most evident for high-amylose starch and was not observed in waxy starch. Differential scanning calorimetry (DSC) thermograms of prime starch from nonwaxy and high-amylose barley exhibited two prominent transition peaks: the first was >60°C and corresponded to starch gelatinization; the second was >100°C and corresponded to the amylose-lipid complex. Starch from waxy barley had only one endothermic gelatinization peak of amylopectin with an enthalpy value of 16.0 J/g. The retrogradation of gelatinized starch of three types of barley stored at 4°C showed that amylopectin recrystallization rates of nonwaxy and high-amylose barley were comparable when recrystallization enthalpy was calculated based on the percentage of amylopectin. No amylopectin recrystallization peak was observed in waxy barley. Storage time had a strong influence on recrystallization of amylopectin. The enthalpy value for nonwaxy barley increased from 1.93 J/g after 24 hr of storage to 3.74 J/g after 120 hr. When gel was rescanned every 24 hr, a significant decrease in enthalpy was recorded. A highly statistically significant correlation (r = 0.991) between DSC values of retrograded starch of nonwaxy barley and gel hardness was obtained. The correlation between starch enthalpy value and gel hardness of starch concentrate indicates that gel texture is due mainly to its starch structure and functionality. The relationship between the properties of starch and starch concentrate may favor the application of barley starch concentrate without the necessity of using the wet fractionation process.     

Utilization of Hydroxypropylated Waxy Rice and Corn Starches in Korean Waxy Rice Cake to Retard Retrogradation

A traditional waxy rice gel cake in Korea, Injulmi, was prepared with hydroxypropylated waxy rice and corn starches (molar substitutions 0.13 and 0.11, respectively), and the textural and retrogradation characteristics of the cake were compared with a conventional cake made of waxy rice flour. In the pasting viscogram, hydroxypropylated starches exhibited reduced pasting temperatures, but increased peak viscosities compared with the unmodified starches. Under differential scanning calorimetry, the T_g′ and ice melting enthalpy of the starch gel cakes were reduced by hydroxypropylation, which indicated that the modified starches had higher water‐holding capacity than the unmodified starches. The degree of retrogradation, as measured by the hardness of the gel cake and the melting enthalpy, was significantly reduced by hydroxypropylation and hydroxypropylated waxy rice starch was more effective in retarding the retrogradation than hydroxypropylated waxy corn starch     

Heat Stress at Different Grain Filling Stages Affects Fresh Waxy Maize Grain Yield and Quality

The effects of heat stress (mean day/night temperatures were 29/18 and 35/18°C for control and heat stress treatments, respectively) at 1–10 or 11–20 days after pollination (DAP) on grain yield and quality of two waxy maize varieties, Suyunuo5 and Yunuo7, were studied. The decrease in grain number and fresh grain yield was more severe when heat stress was introduced early. The responses of grain weight and its components to heat stress were dependent on the variety and heat stress stage. Heat stress increased the starch granule size and volume percentage of diameter larger than 17 μm in both varieties. Crystallinity, iodine binding capacity, and pasting and gelatinization temperatures were increased in both varieties under heat stress at 11–20 DAP; however, the response to early‐stage heat stress was variety dependent. Peak viscosity and retrogradation percentage were increased by heat stress at either stage. These results suggest that heat stress decreases fresh grain yield and accelerates grain filling rate; it increases starch content, starch granule size, crystallinity, and iodine binding capacity as well as decreases the protein content in Yunuo7, thus making the grain less tender and prone to retrogradation. Warm conditions should shorten the time to harvest in fresh waxy maize production.