蛀食害虫对小麦淀粉酶及过氧化物酶活性的影响

探讨玉米象(Sitophilus zeamais)、米象(Sitophilus oryzae)和谷蠹(Rhyzopertha dominica)三种蛀食性害虫不同感染程度对小麦淀粉酶及过氧化物酶活性的影响及变化规律,为小麦科学储藏量化指标提供依据。选用河南产储藏2年的商用小麦,按不同虫种分组,设定不同的虫口密度和感染时间,检测小麦样品降落数值和过氧化物酶(POD)活性,并与虫口密度和感染时间作相关性分析。结果表明,随着虫口密度增加和感染时间延长,样品的降落数值呈波动上升趋势,POD活性呈下降趋势;三种害虫侵害后的样品降落数值与感染时间均存在极显著正相关,POD活性与感染时间均存在极显著负相关,降落数值与POD之间呈极显著负相关,而二者与虫口密度的相关性均不显著。     

蛀食性害虫生长繁殖对小麦馒头品质及质构特性的影响

为研究不同密度的3种重要蛀食性害虫侵害不同时间后,小麦馒头评分值及质构特性的变化,选用豫保1号种子小麦为实验材料,设定3种害虫感染密度(5、10、15头/kg),每30d取样进行检测。结果表明,感染60d时,米象、玉米象和谷蠹侵害的小麦样品馒头的综合评分均低于80分,感染120d后,馒头的综合品质逐渐降低,评分值下降到30～40分。随着害虫感染时间的延长,馒头的硬度和咀嚼性均呈现上升趋势,黏聚性和弹性呈现下降趋势;感染时间与品尝评分值和各质构指标均呈极显著相关,虫口密度对各指标的影响小于感染时间的影响。     

蛀蚀害虫侵害后小麦粗淀粉含量及其糊化特性变化

为探讨蛀食性害虫玉米象、米象侵害后小麦粗淀粉含量和全麦粉糊化特性的变化,选用河南产储藏3年的商品小麦为材料,按不同虫种分组,设定不同的虫口密度和侵害时间,检测害虫感染后小麦粗淀粉含量和全麦粉的糊化特性。结果表明:玉米象和米象不同程度感染后小麦粗淀粉含量总体呈下降趋势;无论是同一虫口密度随着蛀蚀时间的延长,还是同一蛀蚀时间下随虫口密度增加,其感染后的全麦粉峰值黏度、最低黏度、最终黏度、衰减值和回生值均呈下降趋势;糊化温度呈上升趋势,峰值时间基本无变化;粗淀粉含量与峰值黏度、最低黏度、最终黏度、衰减值和回生值均存在极显著正相关,与糊化温度呈极显著负相关,与峰值时间无相关性。     

蛀食性害虫侵害小麦后损伤分型指标研究

为探讨玉米象、米象和谷蠹3种主要蛀食性害虫侵害后对小麦蛀蚀损伤部位及一个生长发育周期内蛀蚀程度的影响,分别将8头、16头、32头和64头蛀食性害虫放入100 g小麦中,并定期对小麦虫蚀部位及数量进行观察、统计.结果表明:虫蚀粒随虫口密度增加而增多,虫口密度不同对产卵量产生一定影响,致使增大比例不同.饥饿处理后的米象先集中进食后产卵,而玉米象、谷蠹产卵与进食同时进行,致使前期蛀蚀部位的比例因虫种不同而变化;后期子代的大量蛀蚀致使蛀蚀胚乳部位数量显著升高,胚和胚乳两部位同时蛀蚀籽粒随时间延长而升高.64头蛀蚀30 d时,不同蛀蚀程度占总的虫蚀粒的百分比不同,但呈正态分布趋势.一个生长发育周期内,米象、玉米象蛀蚀程度在30％～40％比例最高,谷蠹蛀蚀程度在20％～30％比例最高.因此可根据蛀蚀程度对损伤粒初步划分为轻度蛀蚀(0～10％)、中度蛀蚀(10％～50％)和重度蛀蚀(50％～100％)3个阶段.     

米象和谷蠹感染小麦后面筋吸水量变化研究

在25~28℃的条件下,研究了不同密度的米象和谷蠹感染小麦不同时间后面筋吸水量的变化情况。实验结果为:低密度(4头/kg和6头/kg)的谷蠹和米象感染小麦时,小麦宜存和轻度不宜存的临界时间在第12周,高密度(10头/kg)的谷蠹和米象感染小麦时宜存和轻度不宜存的临界时间分别在第10周和第8周。无虫小麦储存时品质发生轻微劣变,但试验期间小麦品质始终在宜存范围内。染虫小麦面筋吸水量随储藏时间延长和害虫密度增加而降低,同密度的米象对小麦的危害比谷蠹更严重。     

入仓期玉米象感染不同时期小麦重量损失的研究

研究了粮食入仓过程中小麦感染玉米象造成的小麦重量损失.主要研究结果为:7月份入仓的小麦,小麦中的玉米象的虫口密度在2头/kg以上,小麦的水分在12%以上,在20 d后小麦重量将发生明显的变化.玉米象(米象)的虫口密度在1头/Kg以内,或小麦的水分在11%以内,小麦的重量损失发生明显变化推迟至一个月.8月份入仓的小麦,小麦中的玉米象的虫口密度在2头/kg以上,重量损失发生在15d内.9月初入仓的小麦,小麦中的玉米象虫口密度在2头/kg以上,小麦发生明显重量损失提前至10d.研究表明不同的玉米象虫口密度、小麦水分和不同的害虫感染时间可造成不同的粮食重量损失.因此,在发生明显的重量损失之前必须做出相应的防治措施.     

蛀食害虫侵害小麦后不同蛀蚀程度损伤粒储藏品质变化

探讨玉米象、米象和谷蠹3种重要的蛀食性储粮害虫蛀蚀小麦后不同蛀蚀程度的损伤粒的品质变化规律,指导科学评价小麦受害虫侵害后其储藏品质的优劣,为小麦科学储藏量化指标提供依据。选用河南产储藏3 a的商用小麦为材料,按不同虫种分组,检测不同蛀蚀程度损伤粒的小麦的品质指标中的水分、粗蛋白、SDS沉降值、湿面筋含量、干面筋含量、面筋吸水率和面筋指数。结果表明：随着损伤粒蛀蚀程度的增强,水分呈动态上升趋势;粗蛋白含量呈线性下降趋势;干湿面筋和面筋吸水率之间存在显著正相关性,都呈下降趋势;面筋指数由于害虫侵害筋力变差数值减少;而降落数值由于大量麸皮和害虫分泌的酸性物质的作用导致数值增加。     

谷蠹蛀食对玉米中淀粉及油脂品质的影响

探讨谷蠹不同虫口密度和为害时间对玉米加工品质的影响,为谷蠹蛀食玉米的有效利用和谷蠹的科学防控提供参考。以河南玉米为试材,以谷蠹为试虫,设置不同虫口密度进行为害,测定不同为害期玉米粗淀粉含量、破损淀粉含量、淀粉颗粒形貌、淀粉糊化特性、粗脂肪含量、脂肪酸值、过氧化值、品尝评分值等品质指标。结果表明：随着虫口密度和为害时间的增加,玉米品质指标变化幅度增加;谷蠹为害65 d时,各处理组玉米中粗淀粉减少幅度和破碎淀粉增加幅度都不超过8%,而在为害25 d时脂肪酸值和过氧化值上升幅度都已超过10%。初始虫口密度为15、25头/kg和5头/kg的玉米中淀粉的糊化特性分别在谷蠹为害25 d和45 d时出现明显变化,尤其是衰减值下降超过10%。另外,谷蠹为害会造成玉米淀粉颗粒形态改变,制成窝头颜色加深,表面粗糙,品尝评分值降低。因此,在玉米储藏过程中,应密切监测谷蠹虫口密度,并适时安排出库,合理进行加工,以降低损失。     

谷蠹侵害后糙米加工品质及食味品质关联性研究

为了研究糙米被谷蠹侵害后对其品质的影响,测定了不同虫口密度和不同侵害时间内糙米加工品质和米饭品尝评分的变化.结果表明:随着虫口密度的增加和侵害时间的延长,糙米的加工品质和米饭品尝评分均发生不同程度的下降;加工品质和米饭品尝评分呈显著正相关,通过测定糙米加工品质的变化可以很好地预测米饭品尝评分的变化.     

主要储粮昆虫在模拟条件下的种群动态研究

本试验利用铁皮仓桶模拟粮堆实际情况,分别对小麦中的玉米象、谷蠹、杂拟谷盗的单一种群以及混合种群的种群动态、种间竞争进行了研究,并建立了相应的模拟模型。结果表明,粮堆表层的种群密度大大高于其它层次。种群在低密度时,上升缓慢。整个变化过程呈“S”形上升。玉米象的种群上升最快,其次为谷蠹、杂拟谷盗。在温度较高时,谷蠧的竞争超过了玉米象,杂拟谷盗的竞争能力最弱,玉米象、谷蠹的取食加快了杂拟谷盗的种群发展。     

小麦内源蛋白水解酶对面团流变学特性的影响

通过小麦内源蛋白水解酶对小麦粉面团流变特性影响的研究,结果表明小麦蛋白水解酶对面团流变强度上有显著的弱化作用,但对不同品种小麦粉的作用程度差异较大。在用乳酸调成的ＰＨ４环境下,小麦蛋白水解酶对面团的软化作用非常迅速。小麦内源蛋白水解酶易热失活,抑胃肽、ＮａＣｌ均能通过抑制小麦蛋白水解酶活力,有效抑制面团的软化作用。     

不同品种紫薯粉面团品质特性

以纯小麦粉面团为对照,通过测定9种紫薯粉面团的粉质、糊化、流变学、水分分布状态特性,探讨9种紫薯粉对小麦粉混合面团品质特性的影响。结果表明:与纯小麦粉面团相比,不同品种紫薯粉面团的吸水率、稳定时间、弱化度、公差指数、糊化温度均有所增加;而面团带宽、峰值黏度、谷值黏度、最终黏度、衰减值、回生值均有所降低;储能模量、耗能模量和深层结合水基本呈现增加趋势,损耗角正切基本呈现下降趋势。紫薯粉的添加使得面团稳定性、保水性增加。不同紫薯粉平均粒径存在极显著性差异（P<0.01）,将紫薯粉平均粒径与其面团的粉质及糊化特性进行相关性分析和聚类分析,发现紫薯粉平均粒径与吸水率呈极显著正相关（P<0.01）,与稳定时间呈极显著负相关（P<0.01）;将紫薯粉面团分为三类,第I类包括鄂紫薯12号等7种紫薯粉面团;第Ⅱ类、第Ⅲ类分别为徐紫薯8号、绵紫薯9号。本研究为小麦粉面团专用紫薯粉品种的生产提供了理论依据。     

Rheological and Microstructural Study of Wheat Doughs Partially Replaced with Mesquite Flour (<Emphasis Type="Italic">Prosopis alba</Emphasis>) and Added with Transglutaminase

The incorporation of different flours into wheat bread may pursue different objectives, such as increasing the nutritional quality of the products or the recovery of flour with little use in the industry. The “mesquite flour” (MF) is rich in sugar, fiber, and protein and is an interesting additive to wheat flour in baking. In this study, we used crude and thermally processed bread dough formulations of wheat flour (WF), replacing 15, 25, and 35% with mesquite flour. Furthermore, each formulation was tested for two levels (0.01 and 0.1%) of the enzyme transglutaminase (TG). Dough rheology was studied by small amplitude oscillatory compression tests, and the microstructure was analyzed by laser confocal microscopy using fluorescein isothiocyanate and rhodamine B as fluorophores. It was concluded that the incorporation of mesquite into the dough resulted in changes in the structure, as evidenced by the increase in tan δ, microscopic observations (loss of the filamentary and cross-linked gluten structure), and by the increase in the gelatinization temperature. The addition of TG led to dissimilar effects on doughs, depending on the formulation (wheat/mesquite content), but most encouraging results indicate the recovery of the structure, evidenced by a reduction in tan δ and the generation of a more filamentary structure in the dough with a higher content of mesquite flour. However, the effect of TG addition on “processed dough” was attenuated and the viscoelastic matrix of gluten did not recover.     

谷朊粉对高含量荞麦面团的影响及其作用机理

本文全面研究了不同添加量谷朊粉(5%、10%和15%)对高含量(50%小麦粉替代率)荞麦面团流变学特性及馒头品质的影响,并以添加10%谷朊粉的混合面团和参照组(纯小麦粉)面团为基础,通过扫描电镜,红外光谱及分析面团中的化学作用力等分析手段,进一步探讨了谷朊粉对改善混合面团流变学性质及馒头品质方面的作用机理。结果表明,添加10%的谷朊粉能够增加荞麦-小麦混合面团中二硫键的含量,改变面团中的化学作用力(离子键、氢键含量和疏水作用力),进而改变面团中面筋蛋白的构象,改善面团的微观结构,从而改善混合粉的糊化特性及面团的粉质和拉伸特性,提高馒头的比容和弹性,改善馒头芯的孔隙结构,但仍达不到参照组馒头的品质,表明添加高含量荞麦全粉不仅仅是稀释面筋蛋白。     

淀粉酶、谷氨酰胺转氨酶及黄原胶对燕麦-小麦混合粉面团流变特性的影响

本文测定了20％燕麦-小麦混合粉面团的粉质、色泽、质构以及流变特性,并与纯小麦面团进行比较,研究添加一定总酶活(3 U/g)的淀粉酶、谷氨酰胺转氨酶、淀粉酶(1.5 U/g)及谷氨酰胺转氨酶(1.5 U/g)、两种酶(各1.5 U/g)以及黄原胶(0.3 g/100 g)对燕麦-小麦混合粉面团流变特性的影响.结果表明,...     

蒸汽润麦对小麦粉微生物指标和理化特性的影响

为缩短小麦的润麦时间,控制小麦粉中的微生物数量,研究了蒸汽润麦处理对小麦粉的降菌作用及对其理化特性的影响。研究表明:蒸汽润麦后,小麦籽粒的温度显著上升(P0.05),出粉率先下降后上升,小麦粉中的微生物数量显著降低(P0.05),且随着处理时间的延长,杀菌效果越明显。当蒸汽处理时间为320 s时,小麦粉中的微生物数量显著减少(P0.05),其中菌落总数减少了1.74 lgCFU/g、霉菌和酵母总数减少了1.99 lgCFU/g、耐热芽孢总数减小了1.01 lgCFU/g。蒸汽润麦处理后,小麦粉的酶活显著降低(P0.05),破损淀粉含量、吸水率和淀粉黏度均呈现先增大后减小的趋势;面团流变学特性的分析结果表明,蒸汽润麦能显著延长(P0.05)面团形成时间和稳定时间,增加面团强度;同时,蒸汽处理还促进了小麦粉中蛋白质的交联聚合。该研究表明蒸汽润麦在降低小麦粉中微生物数量的同时还能在一定程度上改善小麦粉的理化特性。     

Cooperation of phosphatidylcholine with endogenous lipids of wheat flour for an increase in dough volume

Phosphatidylcholine (PC) increases the gas-retaining ability of dough, the dough volume on fermentation and the loaf volume of bread. The cooperation of wheat flour endogenous lipids with PC was examined. More than 90% of the total wheat flour lipids were extracted with chloroform, the extracted lipids comprising glycolipids (33 wt%), non-polar lipids (56 wt%), and phospholipids (11 wt%). The increase in the specific volume of dough with delipidated wheat flour by the addition of PC was smaller than the increase in the specific volume of dough with native wheat flour. The addition of the extracted lipids to delipidated wheat flour restored the increase in dough volume by the addition of PC. The glycolipid fraction of the extracted lipids was most effective for enhancing the action of PC. The results suggest that interaction of PC with wheat flour glycolipids may synergistically increase foam stability to enhance the gas-retaining stability of dough.     

Effects of cultivar and soil fertility on grain protein yield,grain protein content,flour yield and breadmaking quality of wheat

Grain protein content affects the flour yield and breadmaking characteristics of wheat (Triticum aestivum L). In this study, grain protein yield, grain protein content, flour yield and loaf volume were quantified for four wheat cultivars (Inia, Carina, Kariega and SST 86) grown under six different soil fertility regimes in a long-term fertilisation and irrigation experiment at the University of Pretoria. The experimental design was a randomised complete block replicated four times, with fertility as the main plots and cultivars as the subplot treatments. Grain protein yield, flour yield, loaf volume and mixograph dough peak mixing time varied among cultivars and soil fertility situations. Grain protein content differed among cultivars, but mixograph water absorption and dough characteristics did not differ. The highest grain protein yield was 873 kg ha⁻¹ for Carina and the lowest 527 kg ha⁻¹ for SST 86. Grain protein content averaged 131 g kg⁻¹ for Carina and 122 g kg⁻¹ for Kariega. Breadmaking performance showed that in a well-balanced soil fertility situation, Kariega produced 1025 cm³ of loaf volume while Inia averaged 950 cm³. Grain protein yield increased with increasing soil fertility, but grain protein content, flour yield, loaf volume, water absorption and mixograph peak mixing time varied with soil fertility. The interaction between cultivar and soil fertility was significant for grain protein yield, grain protein content, flour yield, loaf volume and water absorption but not dough peak mixing time. The results indicate cultivar differences in breadmaking quality characteristics and that soil fertility status affects grain protein yield, grain protein content, flour yield, loaf volume potential and water absorption but not mixograph peak mixing time and dough characteristics. © 1999 Society of Chemical Industry     

Quality parameters of wheat grain and flour as influenced by treatments with natural zeolite and diatomaceous earth formulations,grain infestation status and endosperm vitreousness

This study investigated the changes in quality parameters of wheat (mealy and vitreous) non-infested and infested with Sitophilus oryzae (L.) caused by treatments with inert dusts: natural zeolite, two diatomaceous earths from Serbia, and a commercial product enhanced DE Protect-It^®.Inert dust treatments, regardless of infestation status, significantly reduced wheat test weight. This was more marked in mealy (8.3%) rather than in vitreous wheat grain (2.7%). Content of silicon dioxide (SiO₂) in flour from infested lots was significantly higher than in non-infested ones. Treatments with all formulations of inert dusts significantly affected flour water absorption in the non-infested wheat lots. Non-infested high vitreous wheat treated with Protect-It^® showed the highest moisture absorption (61.9 g.100 g⁻¹) in comparison with the control (59.7 g.100 g⁻¹). Significant improvement in dough rheology was observed in the infested soft and hard wheat, particularly through rise of dough energy. Small-deformation tests implied certain dough weakening effects of inert dusts in vitreous wheat but this was not observed in standard large-deformation rheological tests.Application of inert dusts shows an ability to improve some aspects of the technological quality of wheat.     

Influence of water and barley β-glucan addition on wheat dough viscoelasticity

The effects of the addition of two barley β-glucan isolates (0.2–1.0% of wheat flour), differing in molecular weight, and water (53–63% in a poor breadmaking wheat flour, cv. Dion, and 58–68% in a good breadmaking wheat flour, cv. Yekora) on the viscoelastic properties of wheat flour doughs were investigated. A response surface model (CCF) was used to evaluate the effects observed on the dynamic and creep-recovery parameters of the dough. The evaluation was done separately for each combination of β-glucan isolate (BG1 of ～10⁵ Da and BG2 of ～2 × 10⁵ Da) and flour type. Besides the contents of β-glucan and water, the molecular size of the polysaccharide and the flour quality were important determinants of the dough’s viscoelastic behavior. Compared to BG1, the higher molecular weight β-glucan (BG2) brought about major changes on all the rheological responses of the fortified doughs. The addition of appropriate levels of β-glucans and water in the poor breadmaking cultivar (Dion) doughs could yield similar viscoelastic responses to those observed by a non-fortified good breadmaking quality flour dough (Yekora).