Moisture stress during growth affects the breadmaking and gelatinisation properties of cassava (Manihot esculenta Crantz) flour

Breadmaking quality (judged by the regularity of the crumb) of cassava (in cassava flour/defatted soy flour/glyceryl monostearate recipes (80/20/3, w/w), Cereal Chem 68 323–327 1991) is related to crop age and the season of planting and harvesting. When taking the data sets of the dry season (J Sci Food Agric 66, 193–202 1994) and rainy season (ibid 68 167–174 1995) together, the following additional interpretation results: breadmaking quality of cassava is positively related to flour from roots with unrestricted growth, and therefore influenced by rainfall distribution, time of planting and harvesting. Variability in baking performance of cassava flour samples is related to the length and severity of the dry season, the growth behaviour of the genotype and the crop age. The highest flour breadmaking quality is obtained after 6 months of unrestricted growth of cassava irrespective of the planting season. © 1998 SCI.     

Influence of different mulch materials on soil temperature,soil water content and yield of three cassava cultivars

In a study with three cassava (Manihot esculenta Crantz) cultivars (Local, TMS4(2)1425 and TMS30572) grown under straw, black polythene and white polythene mulches the fresh tuber yield and yield components were greater than for those grown on bare (control) plots, although the magnitude of increase was cultivar dependent. The order of response was white polythene > straw > black polythene > bare (control). The yield differences were caused by the effects of the mulches on the temperature and water content of the soil surface. Maximum daily soil temperature was lowest on the straw plots (32·5°C), about equal on the bare and white polythene treatments (38·6°C vs 39·8°C) and highest on the black polythene plots (45·0°C). In 1986 the soil moisture reserve was depleted by 84%, 46%, 29% and 24% on the bare, straw, black polythene and white polythene plots within a 60-day period following the last rain, suggesting that it was soil temperature rather than soil moisture which accounted for the large yield differences under black and white polythene.     

Cyanogenesis in somatic embryos and plantlets of cassava (Manihot esculenta Crantz)

A protocol was established for high frequency cyclic somatic embryogenesis and plant regeneration for the cassava variety PRC 60a. Linamarin content and linamarase activity were determined in various tissues of secondary somatic embryos and regenerated plants. Neither linamarin nor linamarase activity were detected in embryogenic callus and somatic embryos. The stems and leaves of regenerated plants, however, contained variable amounts of linamarin and linamarase activity whereas, in the root tissues, only linamarin was detected. This study suggests that the pathway for linamarin biosynthesis may be absent or not switched on in the embryogenic callus and somatic embryos. This system would be useful for investigating cyanogenesis in cassava. © 1999 Society of Chemical Industry     

Impact of genotype,crop age and planting season on the breadmaking and gelatinisation properties of cassava (Manihot esculenta Crantz) Flour

The breadmaking potential of cassava flour (in cassava flour/defatted soya flour/glyceryl monostearate recipes (80/20/3, w/w/w)) is not merely dependent on the age of the crop at harvest, but also on the season of planting and time of harvesting. Effects of cassava genotype are less important for determining bread quality. In flours obtained from crops harvested at different times after planting, differences in gelatinisation onset temperatures measured by Brabender visco-amylography and by differential scanning calorimetry accounted for the observed differences in breadmaking potential of cassava flour of single genotypes and planting seasons to some extent. Cassava starch produced breads with a drier crumb, with a finer structure and with a more bulged crust than cassava flour. Differentiations in baking performance between starch samples, although smaller, still existed. This showed that the breadmaking potential of cassava flour samples is determined both by the starch and by the non-starch fractions. Differentiation of cassava samples in the breadmaking process did not occur at the mixing or fermentation stage of the batter but during baking.     

不同耕作措施对延边烟田水分、烤烟生长及烟叶产量品质的影响

以吉林延边主栽烤烟品种吉烟9号为试验材料,采用田间小区试验,研究了不同耕作措施对烟田水分、烤烟生长及烟叶产量品质的影响。结果表明:(1)移栽20 d后,垄下深松处理(T1和T2)烟田各土层水分含量均高于常规起垄(CK),移栽40 d和60 d后,50 cm以上各土层含水量均是垄下深松结合揭膜后中耕培土处理(T2)>对照>垄下深松;(2)垄下深松处理(T1)旺长期烟叶氮素和磷素含量高于对照,垄下深松结合揭膜后中耕培土处理(T2)团棵期与旺长期烟叶氮素和磷素含量高于对照,且烟叶钾素含量均随着生育时期的推进呈下降趋势;(3)T1和T2可不同程度促进烤烟生长,增大叶面积,增产增质,其中垄下深松结合揭膜后中耕培土处理烤烟经济性状各项指标和致香物质总量最高,化学成分较为协调,产量和产值分别较对照提高310 kg/hm2和5997.9元/hm2。     

Production and characterization of oxidized cassava starch (Manihot esculenta Crantz) biodegradable films

Plastic is one of the most common pollutants in the environment. Therefore, the number of studies on the use of biodegradable packaging is increasing. Starch is the primary material used in the production of biodegradable plastics due to its natural abundance and high biodegradability. Yet, the strong hydrophilic character of starch presents a challenge. Therefore, the modification of its structure through oxidation may yield interesting results as the viscosity reduction. The objectives of this work were to obtain cassava (Manihot esculenta Crantz) starch oxidized with 0.8 and 2.0% active chlorine, to develop biodegradable films and characterize their mechanical properties, solubility in water, permeability to water vapor, degree of swelling, and sorption isotherms. Biodegradable films were produced with starch concentrations of 2, 3, 4, and 5% w/w and 25% glycerol (g/100 g starch) added as a plasticizer. Images of the films were obtained with an atomic force microscope and allow to observe a smooth surface and the absence of starch granules in the film produced with oxidized starches. The tensile strength of the biodegradable film produced with oxidized starch (0.8% active chlorine) was 80 MPa. The value of permeability to water vapor was 1.613 × 10⁻⁹ kg/day/m/Pa, and the average solubility was 41%. The sorption isotherms showed that biodegradable films made with oxidized starches cannot be used in environments with relative humidity below 35% or above 90%.     

The effects of time to first shoot removal on leaf vegetable quality in cassava (Manihot esculenta Crantz)

A field trial was established on a sandy soil at IITA. Ibadan. Nigeria to investigate the effects of time to first shoot removal on cyanide content and chemical composition of leaves of two cassava clones: TMS 91934 and TMS 30572. Four different times to first shoot removal were imposed on each clone: 8. 14, 20 and 52 weeks after planting (WAP). Shoot removal was repeated at 8-week intervals until harvesting at 52 WAP. Shoot removal (SR) involved removing the shoot tips just below the most fully expanded leaf. Early shoot removal during the crop growth period (SR at 8 weeks and SR at 14 weeks 14) produced significantly (P < 0.01) more fresh shoot yield than late shoot removal (SR20 and SR52 weeks). Concentrations of crude protein, iron, phosphorus and zinc were higher in the early harvested leaves but declined in concentration with increasing age of the crop (430–280 g kg^?1, 680–85 mg kg^?1, 88–42 g kg^?1, 128–30 mg kg^?1, respectively). Leaf HCN concentration was about three times that in tuberous roots (137 mg kg^?1 fresh weight compared with 43 mg kg^?1 fresh weight). The variation in leaf HCN concentration was not significant for all the treatments over the period.     

Studies on the synthesis and properties of hydroxypropyl derivatives of cassava (Manihot esculenta Crantz) starch

Cassava starch was subjected to hydroxypropylation in three different media, which included water, water in the presence of a phase transfer catalyst, and 2‐propanol, all at 30 ± 2 °C for 24 h. Propylene oxide was used in four different concentrations (50, 100, 150 and 200 g kg^?1 of starch dry weight). The products were characterized by determining their molar substitution (MS), structural and functional properties. The analyses were done in triplicate and the data were analyzed using the statistical package 8.01. The MS of the products ranged from 0.26 to 1.41. The MS of the hydroxypropyl derivatives were found to be higher when the reaction was carried out in the aqueous medium in the presence of tetrabutylammonium bromide, a phase transfer catalyst, when compared to the reaction in 2‐propanol, which was found to be not very effective at 30 ± 2 °C. The etherification altered the granular properties of starch, as could be seen from scanning electron micrographs. Hydroxypropylation resulted in starch pastes which were stable and with higher swelling volume, solubility, light transmittance and water binding capacity as compared to native starch. The hydroxypropyl starches showed significantly lower pasting temperatures and setback viscosities. The enzyme digestibility of the derivatives was seen to decrease with increase in MS and there was a significant reduction in the syneresis of the starch pastes of hydroxypropyl derivatives. Texture profile analysis showed that hydroxypropylated starch gels exhibited higher hardness, springiness (elasticity) and gumminess and lower cohesiveness than the native starch. Copyright © 2007 Society of Chemical Industry     

关中地区土壤含水率对丝织品老化的影响

为了探究关中地区土壤含水率对丝织品老化影响的规律,采用墓葬土和井水包埋市售桑蚕丝,利用色差仪、显微分析系统、红外光谱仪和万能材料试验机测试了样品老化前后颜色、微观形态、分子结构和抗拉强度的改变,以评价丝织品在包埋环境中的老化状况。结果表明：在20%含水率环境中,丝织品老化最明显;在10%含水率(干燥缺氧)环境中丝织品老化程度最小。在包埋过程中,有粉红色小双孢菌（Microbisporarosea）生成,其分泌物影响丝织品外观。因此,土壤含水率对丝织品老化的影响非常明显。该研究为古代丝织品老化机理和保护研究奠定了基础,对考古现场丝织品的出土保护具有重要意义。     

Studies on the properties of citrate derivatives of cassava (Manihot esculenta Crantz) starch synthesized by microwave technique

Cassava starch citrates with degree of substitution (DS) ranging from 0.005 to 0.063 were synthesized by the microwave‐assisted reaction of cassava starch with citric acid. A response surface small composite design was used to study the effect of different reaction conditions, viz. time, temperature and reagent concentration. All these variables significantly affected the substitution level in the modified starches. The DS increased with increase in the time of reaction and temperature. However, reagent concentration had a negative effect on the DS. The modified starches showed higher viscosity with lower breakdown, lower setback and higher final viscosities in comparison to native starch. Differential scanning calorimetry showed that the modified starches exhibited a decrease in gelatinization temperatures, T_o, T_p, T_e, in comparison to native starch. However, the heat of gelatinization was not significantly affected. The citrate derivatives exhibited reduced swelling volume and enhanced water binding capacities. They were found to be less susceptible to enzyme hydrolysis than native starch. Copyright © 2007 Society of Chemical Industry     

Impact of genotype and crop age on the breadmaking and physico-chemical properties of flour produced from cassava (Manihot esculenta crantz) planted in the dry season

The breadmaking potential of cassava flour (in cassava flour/defatted soya flour/glyceryl monostearate recipes (80:20:3, w/w)) prepared from 10 IITA cassava genotypes harvested at the International Institute of Tropical Agriculture (IITA) at 6, 9, 12, 15 and 18 months after planting, was investigated. Bread quality in general was much more dependent on the age of the cassava at harvest time than on the effects of genotype. Thus, the quality of the bread (judged by the regularity of the crumb) produced from flour from crops harvested 12 months after planting was the best in general, with that from flour resulting from 9-month plants superior to that resulting from 6-month plants. Harvesting at 15 or 18 months led to a reduction in bread quality although the effects varied for different genotypes. Brabender peak viscosity varied widely within each set of flour samples harvested at any particular harvest time, but also with the harvest time itself. By differential scanning calorimetry (DSC) (moisture: dry matter ratio 2-1 w/w), the 6-month samples were characterised by two endothermic transition peaks, one at ca 72°C and one at ca 78°C. With increasing age at harvest time (up to 15 months), the 72°C peak became relatively more important, resulting in a ‘disappearance’ of the 78°C peak in the thermogram. The 18-month samples again showed a 78°C gelatinisation peak or at least a shoulder thereof. The peak multiplicity of the 6-month samples also occurred in DSC experiments with moisture: dry matter ratio of 6-0 (w/w), showing that such samples have a unique gelatinisation pattern. Differences in the analytical values (α-amylase activity, and starch, fibre and protein content) could not explain the differences in bread-making potential.     

Effects of cultivar and growth season on the gelatinisation properties of cassava (manihot esculenta) starch

Starch was extracted from the roots of four different cassava cultivars (Munihot esculenta Crantz) grown in Colombia and harvested on four different occasions with a view to determining whether there was any relationship between the physicochemical properties of the starch and the texture of the cooked roots. The organoleptic quality of the cooked roots was evaluated by a trained taste panel and found to vary in terms of both their glassy texture and their hardness. Studies of the gelatinisation behaviour of the starches by DSC and amylography (with a Brabender amylograph), of the pasting properties by viscography and of the viscoelastic characteristics by a Bohlin rheometer demonstrated some differences between the physicochemical properties of the starches but insufficient to account for the pronounced textual differences.     

Maize (Zea mays) response to nitrogen fertiliser on an ultisol in southern nigeria under two tillage and mulch treatments

The response of maize to four rates of nitrogen (N) fertiliser (0, 60, 120 and 240 kg N ha^?1) on an ultisol in south-eastern Nigeria was evaluated under two tillage and two mulch treatments. Differences in plant height, leaf area index and grain yield between the conventionally tilled and zero-tillage treatments were not significant at P < 0.05, but the mulched plots out-yielded the unmulched plots by 23–46% during the drier seasons. On each tillage-mulch combination, grain yield response to nitrogen was of a quadratic polynomial form, indicating that maximum yields occurred at 123, 139, 130 and 142 kg N ha^?1 on the tilled-mulched, tilled-unmulched, untilled-mulched and untilled-unmulched plots, respectively. Nitrogen use efficiency (grain yield per kg N applied) decreased in the order tilled-mulched (32.6) > untilled-mulched (30.9) > untilled-unmulched (27.8) > tilled-unmulched (22.4) where the figures in parentheses represent nitrogen use efficiency (kg kg^?1). For each tillage treatment maximum soil temperature was higher and moisture retained at 2 and 10 days after saturation lower on the unmulched than mulched plots. Percentage moisture loss between these days was 45.5, 83.3, 25.0 and 55.6 respectively, on the tilled-mulched, tilled-unmulched, untilled-mulched and untilled-unmulched plots. The untilled-mulched plots had the highest contents of residual organic carbon and total N.     

Effect of processing on the retention of carotenoids in yellow‐fleshed cassava (Manihot esculenta Crantz) roots

The retention of carotenoids was studied in roots from yellow‐fleshed, high carotene cassava clones in four different processing methods. The results indicated that the extent of retention varied with the method of processing. The highest retention was observed in oven drying (total carotenoids 54.70–84.01% and β‐carotene 63.90–94.53%) followed by boiling (total carotenoids 47.87–83.79% and β‐carotene 51.31–81.04%) and frying (total carotenoids 48.76–79.77% and β‐carotene 44.11–83.87%). The lowest retention of total carotenoids (32.86–56.40%) and β‐carotene (21.47–56.68%) was recorded in the sun drying method. The variation in the total carotenoids and β‐carotene content depends on variety, processing method and initial carotene content of the fresh root.     

Effects of milk composition, stir-out time, and pressing duration on curd moisture and yield

A study was undertaken to investigate the effects of milk composition (i.e., protein level and protein:fat ratio), stir-out time, and pressing duration on curd moisture and yield. Milks of varying protein levels and protein:fat ratios were renneted under normal commercial conditions in a pilot-scale cheese vat. During the syneresis phase of cheese making, curd was removed at differing times, and curd moisture and yield were monitored over a 22-h pressing period. Curd moisture after pressing decreased with longer stir-out time and pressing duration, and an interactive effect was observed of stir-out time and pressing duration on curd moisture and yield. Milk total solids were shown to affect curd moisture after pressing, which has implications for milk standardization; that is, it indicates a need to standardize on a milk solids basis as well as on a protein:fat basis. In this study, a decreased protein:fat ratio was associated with increased total solids in milk and resulted in decreased curd moisture and increased curd yield after pressing. The variation in total solids of the milk explains the apparent contradiction between decreased curd moisture and increased curd yield. This study points to a role for process analytic technology in minimizing variation in cheese characteristics through better control of cheesemilk composition, in-vat process monitoring (coagulation and syneresis), and post-vat moisture reduction (curd pressing). Increased control of curd composition at draining would facilitate increased control of the final cheese grade and quality.     

Soybean Flour/Oil and Wheat Bran Effects on Characteristics of Cassava (Manihot esculenta Crantz) Flour Extrudate

Adding soybean flour, soybean oil and wheat bran to cassava flour increased the percentage of crude protein/fat and crude fiber respectively in the blends. Crude protein or extrudate correlated negatively (P<0.01) with expansion, water solubility or total reducing sugars and positively (P<0.01) with bulk density, and water absorption. Crude fiber of extrudate correlated negatively (P<0.01) with expansion, bulk density and total reducing sugars. At 4% soybean oil addition, extrudate expansion and WSI were highest, while bulk density and WAI were lowest. Extrudates became more yellow in color on addition of soybean flour.     

滴灌条件下不同灌水量对无核白鸡心葡萄果实的生长发育及品质的影响

为了研究在滴灌条件下不同土壤水分下限对无核白鸡心葡萄果实品质的影响,以3组土壤水分下限为处理,大水漫灌为对照,在生育期对无核白鸡心葡萄果实纵横径、采前果穗的生长发育情况及果实糖度进行测定.总结出节水灌溉可以提高葡萄果实的整齐度,且果实糖度比对照增加约3个百分点,明显提高了果实的品质.     

挤压温度对高水分植物蛋白肉流变学和结构特性的影响

研究了不同挤压温度对植物性肉制品流变性能和结构变化的影响,并测定了流变性能、扫描电镜、粒度和二级结构的变化.结果 表明:植物蛋白肉流变学特性受挤压温度的影响,动态流变结果中样品的G '均高于G",所有样品表现出黏弹性固体的性质.扫描电镜(SEM)观察到挤压前后样品的微观形貌发生了显著的改变,挤压破坏了蛋白质微粒的完整性...