大麦粉替代不同比例玉米对奶牛生产性能的影响

选取泌乳天数、体重、产奶量相近的荷斯坦高产泌乳牛340头,随机分为试验组和对照组两组,每组170头。试验时间共28d,对照组全期饲喂全混合配方日粮(TMR),试验组分四阶段进行,每阶段7d,分别饲喂以10%、20%、30%、40%粉碎大麦粉替代玉米的TMR。结果发现:随着大麦粉替代玉米比例的增加,试验组采食量呈现下降趋势,其中30%、40%替代期采食量极显著低于对照组(P<0.01);与对照组相比,大麦粉替代不同比例玉米对奶牛产奶量影响不一致,20%、30%替代期产奶量增加0.4、0.3kg/d,10%、40%替代期分别下降0.6、0.7kg/d,但差异均不显著(P>0.05);试验组10%、40%替代期乳脂率极显著高于对照组(P<0.01),而20%、30%替代期乳脂率与对照组差异不显著(P>0.05);试验组10%替代期乳蛋白率极显著高于对照组(P<0.01),而30%、40%替代期显著低于对照组(P<0.05),20%替代期乳蛋白率较对照组下降0.012个百分点,但差异不显著(P>0.05)。综上所述,饲粮中用大麦粉替代20%比例的玉米饲喂奶牛,在不影响采食量、乳脂率、乳蛋白率情况下可提升产奶量并降低饲养成本,从而提高经济效益,为最佳替代比例。     

全麦粉和小麦粉中烷基间苯二酚同系物组成的对比分析

【目的】 建立全麦粉标记物烷基间苯二酚（ARs）的高效液相检测方法,对全麦粉和小麦粉中ARs同系物组成进行分析,实现全麦粉真伪品质评价。【方法】 探究高效液相条件,建立ARs同系物5-十七烷基间苯二酚（C17:0）、5-十九烷基间苯二酚（C19:0）、5-二十一烷基间苯二酚（C21:0）、5-二十三烷基间苯二酚（C23:0）和5-二十五烷基间苯二酚（C25:0）的高效液相检测方法,并进行方法学评价。以国内外全麦粉、小麦粉及小麦麸皮等共47份样品为研究对象,测定ARs同系物的含量,分析其ARs同系物组成,并进行热图分析和主成分分析。【结果】 选用ZORBAX SB-C18（150 mm×4.6 mm,5 μm,Agilent）色谱柱,流动相选用0.1%甲酸水溶液和0.1%甲酸甲醇溶液进行梯度洗脱,在紫外检测波长280 nm、柱温35℃、流速0.5 mL·min^-1、进样量20 μL条件下,可在35 min内有效分离5种ARs同系物,各个同系物的色谱峰峰形对称,分离度好。经方法学评价,该方法具有良好的精密度和灵敏度,标准曲线线性相关系数均大于0.999,检出限为0.06—0.19 μg·mL ^-1,回收率为81.16%—112.92%,精密度标准偏差为0.02%—4.02%,可作为ARs同系物的测定方法。通过热图聚类分析可知不同检测样品中ARs同系物组成及总量存在显著差异（P<0.05）。麦粉样品ARs同系物组成中C21:0最多,占33%—61%;C19:0次之,占12%—44%;C17:0、C23:0和C25:0的含量占比较小。美国、加拿大全麦粉的ARs同系物组成丰富度和含量相近,国外全麦粉中ARs同系物组成含量高于国内全麦粉。国内全麦粉中的ARs同系物组成比小麦粉中的ARs同系物组成丰富度高,但个别小麦粉除外。小麦麸皮F₁中ARs同系物组成和总含量显著高于全麦粉和小麦粉,其ARs总含量高达1 795.78 μg·g^-1,与其他样品相比差异显著（P<0.05）。经主成分分析得出,麦粉样品间的主要差异指标为ARs同系物组成含量,作为第1主成分,其累积贡献率为98.40%。小麦麸皮与其他麦粉样品的相对分散最远,中国小麦粉的分散度最大。美国全麦粉和加拿大全麦粉几乎重叠,而中国全麦粉和部分小麦粉与美国、加拿大全麦粉部分交叉。【结论】 本研究建立的液相方法能够有效、快速的对全麦粉中ARs同系物进行定量,适用于麦类全谷物产品中ARs同系物含量的测定。同时,通过全麦粉和小麦粉中ARs同系物组成对比分析可知,全麦粉中的ARs同系物组成丰富度优于小麦粉中的ARs同系物组成丰富度。     

木薯不同品种朱砂叶螨抗性与其叶片内含物的关系

为揭示木薯抗朱砂叶螨机理,以2个木薯品种‘新选048’和‘桂热4号’为材料,在朱砂叶螨发生危害时期,观察不同木薯品种受害程度并对其抗螨性进行鉴定,测定叶片单宁、可溶性糖、可溶性蛋白、游离脯氨酸及叶绿素的含量,分析各生理指标与朱砂叶螨危害程度的关系。结果表明,‘新选048’对朱砂叶螨的抗性优于‘桂热4号’。不同木薯品种,叶片单宁、可溶性糖、可溶性蛋白、游离脯氨酸及叶绿素含量不同;‘新选048’叶片单宁及叶绿素含量均高于‘桂热4号’,而可溶性蛋白、可溶性糖、游离脯氨酸含量则反之;螨害指数与单宁含量、叶绿素含量呈极显著负相关,与可溶性蛋白、可溶性糖、游离脯氨酸含量呈极显著正相关。木薯抗螨性与叶片中的可溶性糖、可溶性蛋白、游离脯氨酸、单宁、叶绿素含量密切相关,这些指标可作为木薯对朱砂叶螨抗性评价的主要指标。     

Screening of diverse cassava genotypes based on nitrogen uptake efficiency and yield

As one of the top three tuber crops of the world, cassava is a staple food and feed crop for tropical and subtropical regions. Because of its high drought resistance and tolerance to nutrient deficiency, cassava is usually cultivated on hilly areas that are nutrient-poor. Nitrogen(N) is one of the significant factors affecting cassava yield. A double factorial(N level×genotypes) split-plot field experiment was conducted to analyze differences in yield and N accumulation of 25 cassava genotypes under low-N conditions to screen for cassava genotypes with high-N efficiency. The two-year field experiment showed that cassava yield and N accumulation are determined by specific genotypes, soil N levels, and year. Among these factors, soil N levels are the main factors that are responsible for differences in cassava yield. When yield and relative N accumulation under low-N conditions were used as screening markers, we identified an efficient and responsive genotype(SC10), and two inefficient and non-responsive genotypes(SC205 and GR5). The efficient and responsive genotype and the inefficient and non-responsive genotype can be used as study materials to further reveal the mechanisms for high-N efficiency in cassava.     

Effect of aging at different temperatures on LAOS properties and secondary protein structure of hard wheat flour dough

The effects of aging from t = 0–108 h at two different temperatures (4 and 25 °C) on the non-linear viscoelastic rheological properties and secondary protein structure of hard wheat flour dough (HWD) were investigated using large amplitude oscillatory shear tests (LAOS) coupled with Fourier transform infrared spectroscopy (FTIR) and SDS-PAGE. Storage (G') and loss (G'') moduli rapidly decreased during aging at 25 °C. Subjecting HWD to progressively longer aging times at 25 °C caused dramatic changes in the non-linear viscoelastic properties demonstrated by strain softening (negative values of e₃/e₁) and shear thinning (negative values of v₃/v₁) behavior. Elastic Lissajous curves of the unaged control dough showed clockwise turn and wider elliptical trajectories as dough aging proceeds especially at higher temperatures. Other non-linear LAOS parameters (G'_M-G''_L, η'_M-η'_L, S and T) supported that aging process at higher temperature caused a progressive change in dough structure from strain stiffening to strain softening behavior while dough samples aged at 4 °C showed fairly close behavior with the control dough sample. FTIR spectra indicated that the relative content of β-sheet and β-turn structures decreased while the content of α-helix structure increased for all dough samples as a result of dough aging. SDS-PAGE results supported the breakdown of high molecular weight (HMW) and low molecular weight (LMW) glutenin subfractions. Aging at the higher temperature of 25 °C decreased the HMW/LMW ratio from 0.77 to 0.59, while the ratio was 0.73 for the dough aged at 4 °C which is fairly close to the control sample. Our results show that the degradation rate of gluten/starch network was triggered by aging at higher temperature, longer aging time, and natural fermentation which resulted in increasing acidity and increase in endogenous proteolytic and amylolytic activity, and also increasing gluten solubility and break down of intermolecular disulfide bonds at acid pH.     

Extensional rheological properties in mixed and fermented/rested dough and relationships with steamed bread quality

In this study, sixteen wheat varieties for cultivation in China were examined for the flour characteristics using the farinograph, extensograph and rheofermentometer, uniaxial extensional rheology employing the extensograph and the Kieffer extensibility rig and biaxial extension by uniaxial compression of mixed dough with and without yeast, rested and fermented dough, and steamed bread quality including specific volume and texture properties. Three statistical analysis methods including Pearson correlation, principle component and stepwise multiple regression analysis were carried out to correlate dough properties with steamed bread quality. Biaxial extension viscosity was positively correlated with texture properties (hardness and chewiness) of steamed bread (r = 0.521–0.685, p < 0.05). Based on the correlation coefficients and the model (r² = 0.852, p = 0.003) obtained using stepwise multiple regression analysis, the best predictors for specific volume of steamed bread were the maximum resistance to extension of rested dough (r = 0.664, p < 0.01) and total work for breakage of fermented dough (r = 0.662, p < 0.01). Principal component analysis of rheological properties of fermented dough and flour characteristics provided more useful information for discriminating wheat flour quality and help breeders to select most convenient wheat flour for the steamed bread making.     

Consumers’ acceptance of optimized gluten-free sorghum-based cakes and their drivers of liking and disliking

Sensory analysis is indispensable in order to promote the project of developing sorghum-based products and, therefore, work on sensory profiles of these products and consumer acceptance is needed to help them succeed. Thus, this study investigated the acceptance of 5 optimized gluten-free sorghum-based and a Reference (with gluten) cakes (prepared from cake premixes), considering their drivers of liking and disliking and their purchase intention. Chocolate and orange flavored gluten-free cakes were prepared based on the numerical optimizations of the formulations (technological, nutritional, functional, technological and nutritional, and technological and functional optimizations). Three sensory evaluation techniques were applied to cakes: acceptance testing, purchase intention and Check-all-that-apply. There was an improvement in the sensory properties of the gluten-free samples in which the nutritional or functional characteristics were optimized together with the technological characteristics, resulting in higher acceptances. It was confirmed that sensory studies are indispensable to confront the challenge of developing sorghum-based foods with sensory characteristics desired by consumers. Therefore, it is concluded that it was possible to offer a gluten-free cake premix that presents good sensory quality, having the potential to be offered as a novelty by the food industry, given that most consumers stated that they did not know sorghum.     

Solvent retention capacity and swelling index of glutenin in hard red wheat flour as possible indicators of rheological and baking quality characteristics

To overcome the cost and expense of milling and baking hundreds of samples in wheat breeding programs, cereal chemists have developed various rapid predictive tests for end-use quality assessment. In this study, five small-scale rapid tests, including Solvent Retention Capacity (SRC) and Swelling Index of Glutenin (SIG), were compared for viability and accuracy to determine end-use quality using small quantities of flour. The tests were applied on commercial hard red spring and hard red winter wheat cultivars from two of the three main production regions in South Africa. Rheological and bread-baking characteristics were related to results of the rapid tests. Highly significant cultivar differences were seen for all rheological and baking-related characteristics, and SRC and SIG parameters, with a strong genotype effect. The environment effect was also highly significant across regions, especially for flour protein content (FPC), which affected the rheological and baking-related characteristics differently across the regions. Correlations among SRC, SIG, rheological, and baking quality-related parameters were highly significant, but inconsistent for the two production regions. Only lactic acid SRC and SIG correlated consistently with the rheological and baking quality-related characteristics in both production regions.     

The effects of sodium reduction on the mechanical properties of doughs made from flours with a range of strengths using a mixograph

To devise strategies for meeting Health Canada's target for reduced-sodium bread production, relationships between dough formula (i.e., red spring wheat flour, salt (NaCl) and water content) and dough mechanical properties were examined. Mixograph energy to peak (ETP), peak height (PKH), and peak bandwidth (PBW) were used to define changes in the properties of doughs induced by sodium reduction. ETP measurements indicated that dough strength characteristics were less responsive to sodium reduction as water content was increased. ETP was a good indicator of the cultivar-dependent response of doughs to sodium reduction, with doughs made from stronger flours being more sensitive to sodium reduction. According to ETP results, sodium reduction led to a decrease in flour strength discrimination. Sodium reduction at NaCl contents below ~1.5% led to more obvious changes in dough mixing characteristics (indicated by the ratio of PBW to PKH). Mixograph analyses of dough tolerance to sodium reduction will guide wheat breeding programs to select cultivars suitable for reduced sodium breadmaking.     

Comparison of different rice flour- and wheat flour-based butter cookies for acrylamide formation

Acrylamide (AcA) contents of different rice flour- and wheat flour-based butter cookies baked at 130 °C for 20, 55, or 90 min were investigated. AcA contents of different flour-based cookies increased with baking time. Color parameters in terms of CIE L*, b*, C*, and ΔE values showed significant opposite correlation to the AcA formation in each of the raw flour cookie. The cookies based on white rice flour had the lowest AcA contents ranging from not detectable (ND) to 204 μg/kg, followed by cookies based on brown rice flour (ND to 450 μg/kg), white wheat flour (155 μg/kg to 661 μg/kg), and whole wheat flour (306 μg/kg to 982 μg/kg). Considerably lower AcA levels were found in the rice flour-based cookies than in the wheat flour-based cookies, as well as in the milled flour-based cookies than in the whole-grain cookies. Although the flour source was considered to play a primary role in determining the AcA content, AcA content was apparently not dependent on the quantities of reducing sugars and free asparagine in the starting raw flour and cookies during baking. In summary, given its reducing potential for AcA formation, rice flour could be used in the production of cookies safe from heat-induced contaminants.