品种及地理位置对糯玉米糊化特性和食味品质影响

本研究以198个糯玉米主栽品种为材料,从适宜种植区角度测定了糯玉米淀粉糊化特征值和食味品质,并分析二者相关关系。结果表明,品种对糊化特征值的影响最大,峰值黏度、崩解值、终值黏度、回复值等糊化特征值基本呈正态分布,80%的材料峰值黏度集中在2 300~3 000 cP,超过3 000 cP 有16个品种。峰值黏度、谷值黏度、崩解值、终值黏度、回复值间为极显著正相关,与糊化时间、糊化温度呈极显著负相关。东南区的食味品质总评分最高,为86.8分,显著高于西南区、黄淮海区和东华北区,而西南区、黄淮海区、东华北区间差异不显著。峰值黏度、谷值黏度和崩解值与食味品质总分呈正相关且相关系数均在0.753以上,可用于评价糯玉米食味品质优劣。     

沙蒿籽胶对玉米混合粉流变特性和面条品质的影响

以玉米粉与小麦粉(6∶4)的混合粉为原料,研究了添加沙蒿籽胶的玉米混合粉的流变特性和面条加工品质的变化。结果表明,添加沙蒿籽胶能改善玉米混合粉的粉质,使面团具有良好的流变特性,并能显著增加面团的粘弹性,从而使面条的粘弹性增强、断条率降低、糊汤程度减小,面条口感滑润耐咀嚼。     

Impact of mild acid hydrolysis on structure and digestion properties of waxy maize starch

In this study, the molecular structure of acid-treated waxy maize starch residues was investigated, and the in vitro digestibility of the residues with 2.2 N HCl at 35 °C for different time periods, was assessed. The granular appearance of waxy maize starch was destroyed and small fractions formed aggregates. A change in chain-length distribution profiles occurred with the degradation of shortest A chains and long B chains in amylopectin. The rise in the ratio of absorbance height at 1047 cm⁻¹ to the height at 1022 cm⁻¹, the intensities of major peaks, X_c, T_p, T_c, and ΔH were observed during mild acid hydrolysis, but the X-ray diffraction patterns displayed A-type for all starches. The amount of rapidly digestible starch increased, whereas the amounts of slowly digestible and resistant starch decreased. These results demonstrate that the amorphous regions of starch granules, including the shortest A chains and long B chains, are preferentially hydrolysed and affect the slow digestion and resistance properties of waxy maize starch.     

Evaluation the quality characteristics of wheat flour and shelf-life of fresh noodles as affected by ozone treatment

In this study, the effects of ozone treatment on the microorganism mortality in wheat flour and shelf-life of fresh noodles were investigated, as well as the physicochemical properties of wheat flour and textural qualities of cooked noodles. Results showed that the total plate count (TPC) can be largely reduced in wheat flour exposed to ozone gas for 30 min and 60 min. Whiteness of flour and noodle sheet, dough stability, and peak viscosity of wheat starch were all increased by ozone treatment. Free cysteine content in wheat flour was shown to decrease significantly (P < 0.05) as the treatment time increased and remarkable protein aggregates were observed in both reduced and non-reduced SDS–PAGE patterns. In addition, ozone treated noodles were generally higher in firmness, springiness, and chewiness, while lower in adhesiveness. Microbial growth and darkening rate of fresh noodles made from ozone treated flour were delayed significantly.     

脱敏魔芋粉制备集成技术初探及其对魔芋粉理化性质的影响

为了有效脱除魔芋粉中的生物碱,从而扩大其应用范围,本研究开发出超微粉碎、酶处理、微波辅助乙醇萃取等集成技术。结果表明,魔芋粉目数在160 目时,经过以上集成技术处理,其生物碱基本脱除干净,且处理后的魔芋粉溶胀性、亮度值相对于对照组有提高,黏度稳定性几乎不变。其形成的水凝胶网络结构稳定、抗剪切变形能力强。说明此技术可以用于制备脱敏魔芋粉,且还可以改善魔芋粉的部分理化性质。     

Endosperm Structure and Physicochemical Properties of Starches from Normal,Waxy, and Super-Sweet Maize

Maize is a main botanical source used for extraction of starch in the world market. New maize cultivars with different amylose contents and special starch metabolism characteristics have been generated. Three types of maize cultivars, namely, normal maize, waxy maize (wxwx homozygous mutant), and super-sweet maize (sh2sh2 homozygous mutant), were investigated to determine differences in endosperm structures, morphologies, and physicochemical properties of starches. Maize kernels exhibited significantly different contents of total starch, soluble sugar, and amylose. Normal maize kernels contained the largest proportion of floury endosperm, followed by waxy maize and then super-sweet maize. Normal maize starch and waxy maize starch were larger in size than super-sweet maize starch. Normal maize starch and waxy maize starch were spherical and polygonal in floury and vitreous endosperms, respectively. Super-sweet maize starch was spherical both in floury and vitreous endosperms. Waxy maize starch showed the strongest birefringence patterns, the highest crystallinity and the largest proportion of ordered structure in external region of granules, and the largest proportion of double helix components, followed by normal maize starch and then super-sweet maize starch. Waxy maize starch showed the highest peak viscosity, trough viscosity, breakdown viscosity, gelatinization temperatures (i.e., gelatinization conclusion temperature, gelatinization onset temperature, gelatinization peak temperature, and gelatinization enthalpy). By contrast, super-sweet maize starch showed the lowest corresponding values for these parameters.     

Physicochemical change and protein oxidation in porcine longissimus dorsi as influenced by different freeze–thaw cycles

Effects of different freeze–thaw cycles (0, 1, 3 and 5) on physicochemical change and protein oxidation in porcine longissimus dorsi were investigated. When the number of freeze–thaw cycles increased, the thawing losses, cooking loss and b*-value increased (P < 0.05), a*-value decreased (P < 0.05). The cutting forces of pork increased after one cycle of freeze–thaw (from 28.3 N to 40.4 N) (P < 0.05), but the further increase of freeze–thaw cycles would lead to decrease of cutting force. The decreases in Ca²⁺- and K⁺-ATPase activity and sulfhydryl group (P < 0.05) content with concomitant increases in carbonyl content and thiobarbituric acid-reactive substances (TBARS) value (P < 0.05) showed that multiple freeze–thaw could cause the porcine protein and fat oxidation, especially for the pork subjected to five freeze–thaw cycles. Gel electrophoresis patterns of porcine muscle showed that multiple freeze–thaw cycles could cause cross-linking of protein in myofibril. Overall, the freeze–thaw process has a detrimental effect on the quality of pork.     

Comparison of Endosperm Starch Granule Development and Physicochemical Properties of Starches from Waxy and Non-Waxy Wheat

Starch granule development and physicochemical properties of starches in waxy wheat and non-waxy wheat were investigated in this article. Starch granules in waxy wheat endosperm showed an early developmental process. Compared with non-waxy wheat starch granules (round-shaped), waxy wheat starch granules (ellipse-shaped) were larger and contained more B-type granules. According to the granule size, starch granules were divided into two groups in waxy wheat, but were divided into three groups in non-waxy wheat. Compared with non-waxy wheat starch, waxy wheat starch had higher swelling power, gelatinization temperatures (To, Tp, Tc), and relative degree of crystallinity. They showed similar ordered structures on external regions of starch granules. Additionally, waxy wheat starch had a higher proportion of double-helical components and a lower proportion of single-helical components than non-waxy wheat starch. Based on the previous results, it was concluded: (1) waxy wheat and non-waxy wheat not only differed in starch granule development, but also in physicochemical properties of starches; (2) waxy wheat had more potential value for producing traditional products than non-waxy wheat.     

蛋白面包贮藏期间理化指标的变化

测定了20℃条件下蛋白面包和酵母面包的理化指标的变化。通过水分含量、水分活度、自由水含量、结合水含量、支链淀粉结晶度、硬度和弹性的测定,得出蛋白面包与酵母面包相比具有较好的品质,在贮藏期间抗老化效果较好,并可延长货架期。为研制新型蛋白面包提供理论参考。     

玉米全粉对方便米线原料粉浆流变特性的影响

为了考察玉米全粉的添加对方便米线原料粉凝胶及流变特性的影响,以四种大米混合为原料,通过添加21%、23%、25%、27%、29%等五种不同含量的玉米全粉,研究其混合体系的流变学特性。结果表明,玉米全粉和方便米线原料大米混合粉浆凝胶体系随着玉米全粉添加量的增大,流体的假塑性不断增强,剪切稀化的现象越明显;当其添加量大于23%时,混合粉浆凝胶的黏稠度逐渐减小,流动性增强,体系开始形成的新的网络结构逐渐趋于稳定;23%和29%添加量体系的G’明显高于其他添加量,未添加的体系G″对频率依赖性大于已添加玉米全粉的混合粉浆,而体系G’对频率的依赖性却不受添加量的影响。      

Contribution of lipid to physicochemical properties and Mantou-making quality of wheat flour

Defatted flours of wheat varieties Karl and Jagger, after removing lipids by chloroform, were used to investigate the contribution of lipid to physicochemical properties and Mantou-making quality by comparing microstructure and thermal properties. The results indicated that defatted flours tend to have more single starch granules, higher gelatinization enthalpy, more water absorption, longer pasting peak time, higher peak and hold viscosity, lower setback and breakdown than those of the control. Meanwhile, the defatted flours had improved cooking stability and better ability to withstand mechanical shear stress. The Mantou-making test showed that the volume of Mantou made from defatted flour did not change significantly. C-Cell analyses on the internal crumb grains of Mantou revealed a deterioration in crumb grain characteristics upon removal of lipids from the flours. The grain cells of Mantou became bigger with thicker cell walls upon removal of lipids.     

面包专用粉研制与开发

面团流变性试验是评价小麦粉物理品质主要方法,其中,面团稳定性和评价值是最重要指标。品质改良剂(添加剂)对面包粉具有修饰改良作用,当面包粉某些性能尚不够完善时,添加剂能有助于改善其性能从而使之成为合格产品;但面包粉性能和质量主要取决于原料小麦品种、品质及制粉工艺,因此,小麦选择及其加工方式是决定面包粉质量关键。