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1.
A hard white spring wheat was milled to yield three patent flours with different starch damage levels by manipulating reduction grinding conditions, and each flour was sieved to give three different particle sizes (85–110, 110–132, 132–183 μm). Raw alkaline noodles were prepared using either 1% w/w kansui (sodium and potassium carbonates in 9:1 ratio) or 1% w/w sodium hydroxide. Noodles prepared with sodium hydroxide were significantly brighter, less red, and more yellow than those made with kansui. Differences in noodle color among flour treatments were evident but were attributable to differences in flour refinement rather to than particle size or starch damage. Noodles were rested for 1 hr after processing before cooking. Alkaline reagent was the main factor associated with cooking loss, being ≈50% greater for sodium hydroxide noodles because of higher pH compared with kansui noodles. Cooked sodium hydroxide noodles were thicker than kansui noodles, and cooked strands for both noodle types became thicker as starch damage increased and as particle size became coarser. Instrumental assessment of cooked noodle texture showed that maximum cutting stress (MCS), resistance to compression (RTC), recovery (REC), stress relaxation time (SRT), chewiness (CHE), and springiness (SPR) were influenced by the type of alkaline reagent. Flour particle size and starch damage also influenced noodle texture but the magnitude of the effects and the trends were dependent on alkaline reagent. MCS of kansui noodles was much greater than for sodium hydroxide noodles. MCS of kansui noodles increased as starch damage increased but, in contrast, MCS of sodium hydroxide noodles decreased with increasing starch damage. REC of kansui noodles increased with increasing starch damage and decreased with larger particle size, whereas for sodium hydroxide noodles REC decreased with increasing starch damage and declined dramatically with larger particle size. Kansui noodles exhibited significantly shorter SRT than sodium hydroxide noodles. SRT of kansui noodles was only moderately affected by starch damage and particle size, whereas for sodium hydroxide noodles, SRT became much shorter as flour became coarser and starch damage became higher. CHE of kansui noodles was greater than for sodium hydroxide noodles. CHE of kansui noodles increased as starch damage increased. In contrast, CHE of sodium hydroxide noodles decreased as starch damage increased and also decreased as flour became coarser. SPR of both noodle types decreased as flour became coarser and starch damage became greater. On the basis of these experiments, flour of smaller particle size is an asset to the cooking quality of sodium hydroxide noodles, but high starch damage is to be avoided. For kansui noodles, the impact of flour particle size on cooked noodle texture was less evident and low starch damage, rather than high starch damage, was an asset. 相似文献
2.
土壤磁化率-温度曲线(κ-T)可用于鉴定土壤中磁性矿物类型。以水稻土、红壤、黄壤和砖红壤为对象,采用BaringtonMS2κ-T磁化率/温度系统,测定了不同土壤类型中磁性矿物种类。结果表明:水稻土κ-T曲线在300℃出现矿物相变点,黄壤、红壤和砖红壤在350℃出现相变点;水稻土和黄壤κ-T曲线呈现出磁铁矿的居里点(580℃),表明土壤磁性载体以磁铁矿为主;红壤和砖红壤的κ-T曲线呈现赤铁矿的居里点(680℃)。将水稻土和红壤分别制成2 mm、1 mm、0.30mm和0.15 mm的颗粒大小,称取相同质量土样(1 g)研究不同颗粒大小对土壤κ-T曲线测定的影响;称取过2 mm筛土样0.5 g、1 g、1.5 g和2 g,研究不同称样量对κ-T曲线测定的影响。结果表明:不同土壤类型,颗粒大小和称样量对κ-T曲线的测定有一定影响,但不会改变土壤中磁性矿物的相变点。它们对红壤和砖红壤的κ-T曲线测定影响甚少,对水稻土和黄壤的影响较大。实验证明在颗粒大小上选择过0.30 mm筛的土样,称样量上选择大于1 g的土样可以得到较明显的κ-T曲线,不会掩盖矿物的相变点。 相似文献
3.
Aroma extracts from fresh soybeans, mung beans, kidney beans, and azuki beans were prepared using simultaneous steam distillation and solvent extraction (SDE) under mild conditions (55 degrees C and 95 mmHg). Extracts were examined for antioxidative activities in two different assays. The aroma extracts isolated from all beans inhibited the oxidation of hexanal for nearly one month at a level of 250 microL/mL. Mung bean and soybean extracts inhibited malonaldehyde (MA) formation from cod-liver oil by 86% and 88%, respectively, at the 250 microL/mL level. Azuki and kidney bean extracts inhibited MA formation from cod-liver oil by 76% and 53%, respectively, at the 250 microL/mL level. The antioxidative activities of mung bean and soybean extracts were comparable with that of the natural antioxidant, alpha-tocopherol (vitamin E). 相似文献
4.
The effect of replacing cowpea with hard-to-cook beans on the nutritional and sensory properties of akara were evaluated. Cowpea (Vigna unguiculata), traditionally used for making akara, was substituted 0%, 25%, 50%, 75%, and 100% with hard-to-cook (HTC) mottled brown beans (Phaseolus vulgaris). Cowpea (CP) soaked for 60 min HTC beans soaked for 18 h were separately decorticated, ground to a paste, and mixed in the following CP:MBB ratios: 0:100, 25:75, 50:50, 75:25, and 100:0. The paste mixtures were each whipped and fried into akara. The samples were analyzed for bulk density, nutritional composition, carbohydrate and protein digestibility, alpha-amylase inhibitor and trypsin inhibitor activity, and sensory attributes. The bulk density of paste as well as of akara increased with the increasing content of HTC bean. Akara made from composite paste had a relatively better amino acid profile. Frying beyond 5 min destroyed the alpha-amylase inhibitors as well as the trypsin inhibitor activity. No significant difference was observed in the overall acceptability of akara made from cowpea substituted up to 50% with HTC beans. Hence, this approach permits the utilization of hard-to-cook beans. 相似文献
5.
牛肉质构特性的近红外光谱无损检测 总被引：3，自引：2，他引：1
为了建立基于近红外光谱技术的牛肉质构特性快速检测方法,该试验采集了202个新鲜牛肉样品在800～2500 nm波长范围内的漫反射光谱,测定了牛肉的硬度、弹性、咀嚼性和黏附性,经小波消噪后,分别采用平滑、一阶微分、二阶微分等6种方法预处理,建立了牛肉质构特性的偏最小二乘回归模型,并用最优模型进行预测。结果表明：经小波消噪后采用二阶微分预处理方法建立的牛肉硬度、弹性、咀嚼性的检测模型效果最好,其校正集相关系数 r 均在0.9以上,校正集均方根误差（root means square error of calibration,RMSEC）分别为6.247 N、0.760 mm、14.954 mJ,预测集相关系数均在0.664以上,预测集均方根误差（root means square error of prediction,RMSEP）分别为8.887 N、0.951 mm、22.117 mJ,相对预测误差（ratio of prediction to deviation,RPD）值分别为2.43、1.88、2.32,预测精度较高,能够有效地预测牛肉的硬度、咀嚼性,可以检测精度要求不高的牛肉弹性;试验所建立的牛肉黏附性检测模型的预测性能不是很理想,虽然其校正集和预测集相关系数较高（分别为0.720、0.694）,RMSEC 和 RESEP 均较小（分别为0.302、0.243 N·mm）,但其 RPD 值小于1.5,模型预测精度较差,不可以用于预测未知样品的黏附性,此方法还需进一步研究。研究结果为牛肉质构特性的快速无损评价提供了理论依据。 相似文献
6.
We evaluated the effect and magnitude of flour particle size on sponge cake (SC) baking quality. Two different sets of wheat flours, including flours of reduced particle size obtained by regrinding and flour fractions of different particle size separated by sieving, were tested for batter properties and SC baking quality. The proportion of small particles (<55 μm) of flour was increased by 11.6–26.9% by regrinding. Despite the increased sodium carbonate solvent retention capacity, which was probably a result of the increased starch damage and particle size reduction, reground flour exhibited little change in density and viscosity of flour‐water batter and produced SC of improved volume by 0.8–15.0%. The volume of SC baked from flour fractions of small (<55 μm), intermediate (55–88 μm), and large (>88 μm) particles of soft and club wheat was in the range of 1,353–1,450, 1,040–1,195, and 955–1,130 mL, respectively. Even with comparable or higher protein content, flour fractions of intermediate particle size produced larger volume of SC than flour fractions of large particle size. The flour fractions of small particle size in soft white and club wheat exhibited lower flour‐water batter density (102.6–105.9 g/100 mL) than did those of large and intermediate particle fractions (105.2–108.2 g/100 mL). The viscosity of flour‐water batter was lowest in flour fractions of small particle size, higher in intermediate particles, and highest in large particles. Flour particle size exerted a considerable influence on batter density and viscosity and subsequently on SC volume and crumb structure. Fine particle size of flour overpowered the negative effects of elevated starch damage, water absorption, and protein content in SC baking. 相似文献
7.
Properties of modified starches from partial waxy wheats have not been examined. Protease digestion of cracked kernels of three hard winter wheats varying in amylose content led to 82–85% recovery of starch, whereas kneading of the flour-water doughs gave 75–83% recovery. All starches had a protein content of <0.3% and ash content of <0.01%. Granule size distributions showed that starch from Ike kernels contained 86% A-type granules with a peak size of ≈18μm, and Karl-92 starch contained 77% A-type granules with a peak size of ≈16μm. The A-type granules (82%) from Rio Blanco starch were intermediate in size. The amylose content of Karl-92 starch, determined by concanavalin-A precipitation of amylpectin, was 28%, which was 17% higher than that of Ike starch (23%). The amylose content of Rio Blanco starch was 26%. The lipid content of Karl-92 starch, determined as fatty acid methyl esters, also was 18% higher than that of Ike starch (601 vs. 488 mg/100 g of starch, respectively). Wheat starches were modified with hydroxypropyl (HP) groups to low (1.5–2.5%) and medium (≈4.0%) levels, and the HP starches were cross-linked with phosphoryl chloride at levels of 0.003–0.075%. Pasting curves (amylograms) showed that Ike starch substituted with a low level of HP and optimally cross-linked with 0.025% phosphoryl chloride (starch basis) had a greater paste consistency than low HP cross-linked Karl-92, and Rio Blanco starches. At 4% HP and optimum cross-linking (0.003% phosphoryl chloride), the paste consistencies of the modified starches were nearly the same. The clarity of unmodified Ike starch paste was higher than that of Karl-92 or Rio Blanco starch pastes, and the clarity of all three pastes decreased as cross-linking was increased. Unmodified Ike starch formed a stronger gel than unmodified Karl-92 and Rio Blanco starches, but gel properties largely converged as the starches were modified. 相似文献
8.
The AACC Approved Method for near-infrared reflectance (NIR) spectroscopy to produce a wheat hardness score for wheat market classification can be corrected for variation in wheat moisture content. The cause of the variation in NIR spectra resulting from variation in wheat moisture was investigated. Ten samples each of soft red winter, soft white winter, hard red winter, and hard red spring wheats were stored at 20, 40, 60, and 80 equilibrium relative humidity. Wheats were then ground on a cyclone grinder as required by the standard method. Variation in unground wheat kernel moisture content resulted in variation in NIR data. NIR log 1/reflectance values increased at all wavelengths as wheat moisture content increased. Spectral changes were related to changes in the apparent particle size of ground wheat meal as it was influenced by moisture content. Higher moisture contents produced slightly higher apparent particle size in meal, suggesting larger particles of pericarp that became more pliable at higher moisture (temper) levels. The apparent particle size of meal of high moisture wheats resulted in greater NIR radiation scattering and decreased reflectance. Meal moisture content itself had no effect on the two NIR wavelengths used to evaluate wheat hardness. 相似文献
9.
Small kernels of soft wheat are sometimes considered to be harder than larger kernels and to have inferior milling and baking characteristics. This study distinguished between kernel size and kernel shriveling. Nine cultivars were separated into large, medium, and small kernels that had no shriveling. Eleven cultivars were separated into sound, moderate, and severely shriveled kernels. Shriveling greatly decreased the amount of flour produced during milling. It adversely affected all other milling quality characteristics (ash content, endosperm separation index, and friability). Shriveled kernels produced flour that had inferior soft wheat baking qualities (smaller cookie diameter and higher alkaline water retention capacity). In contrast, test weight and milling qualities were independent of kernel size. Small, nonshriveled kernels had slightly better baking quality (larger cookie diameter) than larger nonshriveled kernels. Small kernels were softer than large kernels (measured by break flour yield, particle size index, and flour particle size). Small nonshriveled kernels did not have diminished total flour yield potential or other reduced flour milling characteristics. Those observations suggest a possibility of separating small sound kernels from small shriveled kernels to improve flour yield and the need to improve dockage testing estimation techniques to distinguish between small shriveled and small nonshriveled kernels. 相似文献
10.
Kalamaki MS Powell AL Struijs K Labavitch JM Reid DS Bennett AB 《Journal of agricultural and food chemistry》2003,51(25):7465-7471
Suppression of the expression of a ripening-related expansin gene, LeExp1, in tomato enhanced fruit firmness and overexpression of LeExp1 resulted in increased fruit softening. Because of the incompletely understood relationship between fresh fruit texture and the consistency of processed products, we examined the effects of LeExp1 overexpression on the processing characteristics of tomato fruit. As determined by Bostwick consistency and by controlled strain rheometry, juices and pastes prepared from transgenic tomatoes with suppressed LeExp1 expression had a higher viscosity than preparations from control fruits. However, the viscosity of juice and paste prepared from fruit overexpressing LeExp1 was significantly greater than products from controls or lines with reduced LeExp1. Bostwick consistency increased by 9% (juice) and 6% (paste) in lines with suppressed LeExp1 expression but increased by 27.5% (juice) and 19.5% (paste) in lines overexpressing LeExp1, relative to controls. Determined by laser diffraction, the particles in juice and paste prepared from transgenic fruits with reduced LeExp1 expression were smaller, and preparations from fruits overexpressing LeExp1 had a size distribution indicating more large particles. Analysis of cell wall polysaccharides size indicated that LeExp1 overexpression enhanced depolymerization of water soluble pectins as well as tightly bound matrix glycans. LeExp1 overexpression may allow increased cell wall hydration, resulting in expanded particle size and increased viscosity of products. Because either LeExp1 suppression or overexpression leads to improved consistency, the interactions that contribute to optimal product rheological properties are complex. 相似文献
11.
《Cereal Chemistry》2017,94(2):177-184
In this study, red beans were bioprocessed by using a novel solid‐state fermentation (SSF) with an edible and medical filamentous fungus Cordyceps militaris . The effect of SSF on the total phenolic content (TPC), antioxidant activity, and DNA damage protection of red beans was determined. Furthermore, solvents with different polarities (80% methanol, 80% ethanol, 80% acetone, and deionized water) were used to extract antioxidant compounds from the red bean samples. The results indicated that SSF significantly enhanced TPC, 2,2‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonic acid) diammonium salt radical cation scavenging activity, reducing power, and chelating ability of red beans. Furthermore, this study also demonstrated that fermented red beans exhibited greater protection against oxidative DNA damage than nonfermented red beans. Besides, the water extract of fermented red beans showed the highest TPC, antioxidant activity, and DNA damage protection among the various extracts examined. For the specific phenolics profile, HPLC analysis was performed, which showed that gallic acid, chlorogenic acid, p‐hydroxybenzoic acid, syringic acid, ferulic acid, daidzein, quercetin, and genistein of red beans were increased during SSF. There was a positive correlation among phenolic compounds, antioxidant activity, and DNA damage protection. Thus, this study demonstrated that SSF with C. militaris is an effective method for the enhancement of phenolic compounds, antioxidant activity, and DNA damage protection of red beans. 相似文献
12.
Tan SY Yeung CK Tako E Glahn RP Welch RM Lei X Miller DD 《Journal of agricultural and food chemistry》2008,56(13):5008-5014
Polyphenols in foods may chelate dietary Fe and lower its bioavailability. Concentrations of phenols are higher in red beans than in white beans. The aim of this study was to compare iron bioavailabilities from red and white beans in a piglet hemoglobin repletion model. Fe deficient cross bred piglets (Hampshire x Landrace x Yorkshire) were used. Nutritionally balanced diets (except for Fe) were formulated to contain 50% precooked, dehydrated beans (either small red or Great Northern white). At age 5 weeks, the piglets were assigned to two groups and fed diets containing either red or white beans for 4 weeks. Weight and hemoglobin (Hb) concentrations were monitored weekly. Feed intakes were measured daily. Hemoglobin repletion efficiency (HRE) was calculated as the gain in total body hemoglobin Fe (Hb-Fe) divided by Fe intake. Hb concentrations, Hb-Fe gains, and HRE were not different between the groups at any time point ( p > 0.05). HRE values in the red bean group were 50% in the first week and 30% over the entire 4 week period. In the white bean group, they were 56 and 26%, respectively. Proline-rich protein mRNA concentrations in parotid glands were higher in the red bean group compared to the white bean group. These results show that iron bioavailabilities from red and white beans are similar and suggest that pigs adapt to the inhibitory effects of polyphenols on iron absorption by increasing the secretion of protective proline-rich proteins in the saliva. 相似文献
13.
The purpose of this study was to evaluate the differences among four retail whole wheat flours with respect to particle size distribution and composition of fractions separated by sieving. Interestingly, not only were significant differences discovered among the brands for particle size distribution, but lots within two of the brands were significantly different (P < 0.05), suggesting that flour particle size produced by the same company is not always consistent. Starch damage ranged from 4.67 to 7.69%. As expected, darker colors were associated with the larger particle size fractions, and the colors lightened as particle size decreased. This observation suggested that the differences in particle size resulted from differences in the degree to which the bran fraction of the kernel was milled, an observation substantiated by the distribution of ash in each fraction, which ranged from 0.37 to 38.0% of total ash. Distribution of protein ranged from 0.19 to 61.8% of total protein. These data are relevant because differences in particle size distribution and composition affect functionality, sensory acceptability, nutritional properties, and shelf life of whole wheat flour. 相似文献
14.
15.
为了制备栀子黄脂质体,以栀子黄色素为研究对象,采用乙醇注入法制备栀子黄脂质体,以栀子黄包封率(EE)为指标,通过响应面法优化制备栀子黄脂质体的反应参数,并通过Zeta电位与平均粒径、傅里叶红外光谱(FT-IR)和透射电子显微镜(TEM)等技术对其结构与形态进行表征。采用壳聚糖对栀子黄脂质体进行表面修饰,通过分析经紫外光照射、加热和体外模拟消化等处理后脂质体中的Zeta电位、平均粒径及释放率等指标的变化,研究壳聚糖修饰栀子黄脂质体的稳定性。结果表明,最优反应条件为:搅拌温度51.5℃,卵磷脂与胆固醇质量比5.2∶1,缓冲液体积为32.4 mL,所得栀子黄脂质体EE为78.36%。根据Zeta电位与平均粒径、FT-IR及TEM分析结果可知,已成功制备未修饰栀子黄脂质体与壳聚糖修饰栀子黄脂质体,其平均粒径从203.77 nm增加至282.17 nm。紫外光照射、加热和体外模拟消化试验结果表明,壳聚糖修饰脂质体的稳定性明显高于未修饰脂质体。本研究可为水溶性类胡萝卜素脂质体的制备及应用提供一定的理论依据。 相似文献
16.
Genetic variation in the physical properties of sweet potato starch. 总被引：10，自引：0，他引：10
Sweet potato starch, prepared from 44 genotypes adapted to Philippine conditions, showed wide variation and distinctly different pasting profiles in Rapid Visco-Analyzer (RVA) analysis at 11% and 7% starch concentration. At 11% starch concentration, the pasting profiles were type A, characterized by high to moderate peak with a major breakdown and low cold paste viscosity. At 7%, the pasting profile was generally type C, characterized by the absence of a distinct peak with none to very slight breakdown and high cold paste viscosity. However, differentiation among genotypes was better achieved from RVA pasting profiles at 11% starch concentration. Peak viscosity (PV) and hot paste viscosity (HPV) at 11% starch paste concentration had significant negative correlation with amylose content. PV, HPV, and setback ratio were significantly correlated to adhesiveness of the starch gel. Sweet potato starch generally had high swelling volume but low solubilities at 92.5 degrees C. 相似文献
17.
Roller milled flours from eight genotypes of hull‐less barley (HB) with normal, waxy, zero amylose waxy (ZAW), and high amylose (HA) starch were incorporated at 20 and 40% (w/w) with a 60% extraction Canada Prairie Spring White (CPSW, cv. AC Vista) wheat flour to evaluate their suitability as a blend for yellow alkaline noodles (YAN). The barley flour supplemented noodles were prepared using conventional equipment. Noodles containing 40% HB flour required less work input than the corresponding 20% blend noodles due to a higher water absorption at the elevated level of HB flour addition, which probably caused them to soften. The addition of any HB flour at either level to the CPSW flour resulted in significantly decreased brightness (L*) and yellowness (b*), elevated redness (a*), concomitant with a significantly greater number of specks per unit area of noodle sheet compared with the control flour. The addition of 40% HB flour to YAN decreased cook time and cooking losses. Noodle firmness, as determined by maximum cutting stress (MCS), was significantly increased by the addition of 40% HB flour. Noodle chewiness, as determined by the texture profile analysis (TPA), was affected by the type of starch in the barley samples; the addition of waxy and ZAW HB flour decreased chewiness, whereas normal and HA HB flour increased chewiness of composite noodles. 相似文献
18.
为提高墨鱼汁在食品加工业中的应用价值,将高压微射流均质处理后的墨鱼汁添加到生鲜面中,分析不同处理压力(0、40、80、120、160、200 MPa)对墨鱼汁粒径变化及墨鱼汁生鲜面蒸煮、质构特性的影响。结果表明,微射流最佳处理压力为120 MPa。该条件下,墨鱼汁粒径显著减小为101.20 nm(P<0.05),墨鱼汁生鲜面条最佳蒸煮时间为315 s,蒸煮断条率和蒸煮损失率分别降低至4.44%和4.98%,膨胀率增加至183.50%,硬度、咀嚼性分别达到642.37 g、176.84 g,感官评价综合得分为94.31。扫描电镜结果显示,微射流处理后墨鱼汁生鲜面结构变得更加均匀致密,孔隙相对减小,结构得到改善。综上,微射流可较好地改善墨鱼汁生鲜面的蒸煮特性和质构特性。本研究结果为墨鱼汁食品的开发提供了一定的理论依据。 相似文献
19.
【目的】旨在明确粳型软米食味品质及其质构特征对氮肥水平的响应差异及各指标间的关系。【方法】在稻麦两熟制条件下,选用江苏省生产上具有代表性的粳型软米品种南粳9108和南粳5055为试验材料,通过设置4种施氮水平0、150、225和300 kg/hm2,分析了不同施氮水平对粳型软米的食味品质与质构特征的影响,并对各指标间的关系进行了系统分析。【结果】1)在设计范围内,随施氮量的增加,稻米完整性持续增加,但香气、光泽、味道和食味值等指标呈下降趋势,粳型软米食味指标对氮肥的敏感程度表现为口感光泽食味值味道香气完整性,说明氮肥水平对粳型软米口感和光泽的影响程度较大,而对香气和完整性的影响程度较小。2)随着施氮量的增加,硬度、粘聚型、咀嚼度和回复性呈先增加后降低趋势,最大值在N 225 kg/hm2;粘着性呈先降低后升高趋势,最低值在N 225 kg/hm2处理;弹性不受氮肥水平影响,粳型软米质构指标对氮肥的敏感程度表现为咀嚼度硬度回复性粘着性粘聚性,说明氮肥水平对粳型软米的胶粘性、咀嚼度、硬度影响较大,而对粘聚性的影响程度较小。3)南粳9108的香气、光泽、味道、口感和食味值均高于南粳5055,完整性低于南粳5055,并且其各食味指标的变异系数均高于南粳5055,说明南粳9108食味特征优于南粳5055,并且前者对氮肥的敏感性强于后者。4)南粳9108的硬度、粘着性、弹性、咀嚼度均低于南粳5055,粘聚性、胶粘性均高于南粳5055,并且各质构指标的变异系数均高于南粳5055,说明南粳9108质构特征较优并且前者对氮肥的敏感性弱于后者。5)相关分析表明,食味值与香气、光泽、味道、口感呈极显著正相关,与完整性呈极显著负相关;口感与光泽呈显著正相关,与完整性呈显著负相关;完整性与香气、光泽呈极显著负相关;光泽与香气呈极显著正相关;回复性与硬度极显著正相关,与粘聚性呈显著正相关。【结论】氮肥水平和品种对粳型软米食味品质与质构特征具有显著影响。增加施氮量将降低供试的两个品种米饭的口感、光泽、味道和香气,但增加其完整性,施氮量小于225 kg/hm2,施氮可以增加米饭的硬度、粘聚型、咀嚼度和回复性。因此,粳型软米生产中应特别重视氮肥的施用水平,以保持其优良的风味。 相似文献
20.
为了探讨粒度组成对红黏土干缩裂隙发育的影响,从而给红黏土地区的工程建设及减灾防灾提供理论依据。通过室内干燥试验,研究了粒度组成对昆明呈贡红黏土饱和泥浆样的水分蒸发、干缩裂隙的形成和演化、表面干缩裂隙结构形态的影响。结果表明:(1)蒸发曲线分为4个阶段,常速率阶段是最重要阶段;(2)常速率阶段历时随粒径减小而增长,随粒径分布范围变大而减短;(3)蒸发速率与粒径、粒径分布范围的关系不明显;(4)干缩裂隙形成与演化过程分为5个阶段,受粒度组成影响最显著的是裂隙形成阶段;(5)粒度组成影响裂隙形成阶段历时、不同等级裂隙先后衍生关系、开裂曲线的分段性、裂隙网络结构和土块分布;(6)天然粒组样的干缩裂隙产生向上卷曲现象;(7)粒径分布范围越大,分布非均匀性越强,表面裂隙率越大,而粒径的影响不明显;(8)表面裂隙的分形维数随粒径减小而减小。综上,粒径分布范围和分布非均匀性显著影响红黏土的水分蒸发过程,干缩裂隙的形成和演化,表面干缩裂隙结构形态。 相似文献