A simple and rapid method for isolating cassava leaf linamarase suitable for cassava cyanide determination

A simple method was developed for isolating cassava leaf linamarase. It involved homogenising the leaves in a buffer containing polyvinylpolypyrrolidone, followed by ammonium sulphate precipitation, filtration and partial purification of the enzyme by hydrophobic interaction chromatography. All stages of the enzyme preparation were carried out at room temperature and it was completed within 90 min. A linamarin-indicator strip for checking the activity of the enzyme preparation was also developed. This isolation technique which has been developed into a simple kit should be suitable for laboratories in developing countries where the enzyme is needed to determine the cyanogenic potential of cassava and its products. © 1997 SCI.     

Effect of variety on the heat transfer coefficient during drying of fermented ground cassava

The effect of variety on the heat transfer coefficient of four cassava cultivars (TMS 30555, TMS 30572, NR 8082 and one Native type) was investigated. The cultivars were dried at an air temperature of 142 °C, air velocity of 1.397 m/s⁻¹ and relative humidity of 55%. The heat transfer coefficient obtained varied from 0.0622 to 0.0725 kJ kg s °C. The heat transfer coefficient varied for some cultivars, while some cultivars had close heat transfer coefficient. NR 8082 had the lowest heat transfer coefficient while TMS 30555 had the highest heat transfer coefficient. The cultivars with high heat transfer coefficient were found to have low bulk density, smaller particle diameter, high drying rate, low specific heat capacity and high carbohydrate fat and protein contents than other cultivars.     

Mechanism of cyanogen reduction in cassava roots during cooking

The cyanogen elimination profile during cooking of cassava roots was investigated and correlated with the changes in cyanogenic β-glucosidase (GLase) activity monitored at close intervals in the cook water and root. Cyanogenic β-glucosidase (GLase) activity was detected in the cook water within 5 min of starting cooking. Whilst significant decrease in the GLase activity was noticed in cook water and root within 15 and 10 min, respectively, for varieties M4 and H165, H1687 GLase activity decreased tremendously only at 20 and 15 min in the cook water and root, respectively. There was no GLase activity in cook water after the 30 min pre-boiling phase while GLase activity was present in the roots even after 60 min of cooking. The decrease in GLase activity at 15–20 min pre-boiling phase led to accumulation of cyanogens in cook water. The cyanogen fractions (glucosidic and non-glucosidic) increased significantly with cooking in the cook water in the case of varieties M4 and H165 while their levels were almost static throughout the post-boiling phase for H1687. The amount of HCN escaping through steam did not bear a direct relationship with the initial cyanogen content in cassava roots. Although free cyanogen is highly volatile, all of it does not escape through steam and a certain quantity appears to be stabilised in the cook water. ©1997 SCI     

Comparison of an alkaline picrate and a pyridine-pyrazolone method for the determination of hydrogen cyanide in cassava and in its products

A determination of hydrogen cyanide in fresh cassava tissues and in processed cassava products using an alkaline picrate procedure and a pyridine-pyrazolone method which uses Conway vessels has been made. Results obtained for the fresh cassava tissues by the two methods were similar. Statistically significant higher values for processed cassava products were obtained by the alkaline picrate method which measured both glycosidic and non-glycosidic cyanide. The suggestion is reaffirmed that hydrogen cyanide in processed cassava products may exist in two forms: glycosidic and non-glycosidic (entrapped) cyanide.     

The retail market for fresh cassava root tubers in the European Union (EU): the case of Copenhagen,Denmark — a chemical food safety issue?

BACKGROUND: A number of retail shops in Copenhagen sell fresh cassava roots. Cassava roots contain the toxic cyanogenic glucoside linamarin. A survey was made of the shop characteristics, origin of the roots, buyers, shop owner's knowledge of toxicity levels, and actual toxicity levels. RESULTS: Shops selling fresh cassava were shown mostly to be owned by persons originating in the Middle East or Afghanistan, buyers were found to predominantly be of African origin, and sellers' knowledge concerning the potential toxicity was found to be very restricted. Seventy‐six per cent of the roots purchased had a total cyanogenic potentials (CNp) above the 50 mg HCN equivalents kg^?1 dry weight (d.w.) proposed as acceptable by an EU working group. Two of 25 roots purchased had CNp higher than 340 mg HCN eq. kg^?1 d.w. CONCLUSION: The EU has previously made risk assessments concerning cassava and cyanogenic compounds. In the light of the conclusions drawn, the EU needs to make decisions about how to deal with the regulation and control of fresh cassava roots imported to the European food market. Also cassava root products and cassava leaves should be considered. Copyright © 2009 Society of Chemical Industry     

Amaranth flour,cassava starch and cassava bagasse in the production of gluten‐free pasta: technological and sensory aspects

The objective of the present research was to analyse the combined effect of pregelatinised cassava starch and bagasse (70:30) flour, cassava starch and amaranth flour on the cooking properties of pasta, verify the acceptance and buying intention of the product with the best technological characteristics, and finally compare them with commercial products made with regular and whole wheat flour. The vermicelli‐type pasta obtained in this study in the proportion of 10:60:30 (pre‐gelatinised flour:cassava starch:amaranth flour) showed the best results in the quality tests, with a cooking time of 3 min, mass increase of 101.5% and 0.6% solids loss to the cooking water, superior to the commercial pasta. Acceptance testing showed that this was a very good pasta (score of 7.2 on a 9‐point scale) and obtained 42% buying intention amongst the consumers. The elaboration of pasta containing pregelatinised cassava starch and bagasse (70:30) flour, cassava starch and amaranth flour was shown to be a feasible alternative with respect to the technological and sensory aspects, and could be consumed by those suffering from gluten intolerance.     

湿热处理对裸燕麦复配米方便米饭品质的影响

燕麦属于粗杂粮,具有极高的营养价值。为了改善目前市场上方便米饭多以粳米为原料,加之在生产工艺中造成米饭营养流失而引起的方便米饭营养不足,以裸燕麦米为原料,与粳米以适当比例配合,制作裸燕麦复配米方便米饭,确定方便米饭加工工艺最佳工艺参数。试验结果表明,将裸燕麦用沙滚碾米机进行碾磨后与粳米以适当比例复配,裸燕麦米与粳米的最佳比例为1∶2,湿热处理最佳工艺为在35℃恒温水浴锅中将米浸泡30 min,蒸煮米水比1∶1,蒸煮时间8 min,蒸煮压力0.05 MPa,此条件下裸燕麦复配米方便米饭的复水率为2.20,糊化度91.2%,感官评分27.1,综合值140.3。     

Batter rheology and bread texture of sorghum‐based gluten‐free formulations modified with native or pregelatinised cassava starch and α‐amylase

The influence of α‐amylase (0–0.3 U g^?1) on the crumb properties of gluten‐free sorghum batter and bread, respectively, was investigated. The formulations were modified using native or pregelatinised cassava starch (i.e. batter A – 17% pregelatinised starch, 83% sorghum, 100% water fwb; batter B – 17% native starch, 83% sorghum, 100% water fwb; and batter C – 30% native starch, 70% sorghum, 80% water fwb). The batters had solid viscoelastic character with the storage modulus predominant over the loss modulus. Storage moduli of batter A decreased with increasing angular frequency, whereas the moduli of batters B and C were independent from the angular frequency. Increasing enzyme concentration did not affect the loss factors of the batters. Batters’ resistance to deformation, from highest to lowest, followed the order C > A > B. Increasing enzyme concentration decreased crumb firmness, cohesiveness, springiness, resilience and chewiness but increased adhesiveness. Overall, breads containing native starch had better crumb properties (i.e. springier and less firm, chewy and adhesive) than breads containing pregelatinised starch.     

Thermo‐physical properties of composite bread dough with maize and cassava flours

Composite wheat–cassava and wheat–maize flours were produced in ratio 100:0. 60:40, 50:50, 40:60 and 0:100 respectively. Thermo‐physical properties of bread dough were determined. For wheat –cassava composite bread dough, moisture content ranged between 44.02 ± 2.04 to 51.31 ± 2.99% dry basis (db), density (1035.2 ± 20.4 to 975.6 ± 12.6 kg m^?3), specific heat capacity (2.51 ± 0.61 to 3.01 ± 0.42 kJ kg^?1 K) and thermal conductivity (0.362 ± 0.13 to 0.473 ± 0.12 W mK^?1). While wheat–maize mixture gave 44.14 ± 1.94 to 45.09 ± 1.26%(db) of moisture content, 981.4 ± 16.3–960.4 ± 22.5 kg m^?3 density, 1.77 ± 0.17–2.61 ± 0.63 kJ kg^?1 K specific heat capacity and 0.36 ± 0.07–0.39 ± 0.02 W mK^?1 thermal conductivity. Effects of substitutions was significant on moisture content and thermal conductivity of dough while non significant influence was recorded on density and specific heat capacity at P < 0.05.     

Use of infrared analysis to identify genetic resources from isolated producers in Brazil as a tool to improve cassava competitiveness in the starch market

Our objective was to verify the potential of identifying different starches in Brazilian landraces of cassava using near and medium infrared analyses. The survey was conducted on 132 landraces collected throughout the Cerrado, Pantanal and Amazon biomes, in the Brazilian state of Mato Grosso, including 10 commercial starches. The results are reflective of selection for different genetic variants in small isolated producers. Infrared analysis enables rapid identification of this material and is the first step in identifying starches with different properties. The results demonstrate the potential of MIR analyses for in situ evaluation, an additional option for identifying important varieties and value the development of efforts made by small producers, whose landraces have special and economically important properties.     

食品中氯丙醇污染及其毒性

氯丙醇类化合物,尤其是3-MPCD对酱油污染成为国际上关注食品安全热点问题之一。为了对该类物质有一全面了解,该文对食品中氯丙醇类化合物的种类、特性、来源、毒性、检测方法和预防措施及各国限量标准进行综述。     

Cyanide detoxification in cassava for food and feed uses

Cassava (Manihot esculenta Crantz) is an important tropical root crop providing energy to about 500 million people. The presence of the two cyanogenic glycosides, linamarin and lotaustralin, in cassava is a major factor limiting its use as food or feed. Traditional processing techniques practiced in cassava production are known to reduce cyanide in tubers and leaves. Drying is the most ubiquitous processing operation in many tropical countries. Sun drying eliminates more cyanide than oven drying because of the prolonged contact time between linamarase and the glucosides in sun drying. Soaking followed by boiling is better than soaking or boiling alone in removing cyanide. Traditional African food products such as gari and fufu are made by a series of operations such as grating, dewatering, fermenting, and roasting. During the various stages of gari manufacture, 80 to 95% cyanide loss occurs. The best processing method for the use of cassava leaves as human food is pounding the leaves and cooking the mash in water. Fermentation, boiling, and ensiling are efficient techniques for removing cyanide from cassava peels.     

Effects of plant population on soil structure,soil moisture depletion and on yield of cassava (Manihot esculentd) on an Ultisol in Southeast Nigeria

The effects of four cassava populations (8, 10, 13 and 20 × 10³ plants per ha^?1) on soil physical properties, moisture retention characteristics, moisture potential profiles and moisture depletion patterns were compared with uncropped plots receiving no cultivation of an Ultisol in the humid region in eastern Nigeria. The growing of cassava decreased the bulk density of 0–10 cm depth by 17% in comparison with the uncultivated soil (1.53 Mg m^?3). The bulk density of the 10–20 cm depth was higher for the cropped than the uncropped control plots. The moisture retention below a suction of pF 2.4 for 0–10 cm depth was less for the uncultivated control than for soil growing cassava. The reverse was found in moisture retention characteristics of the 20–40 cm depth especially for low suction ranges of pF below 0.8. The 0–10 cm soil layer of uncropped control dried more rapidly than the cropped soil. Below 10 cm, however, cassava depleted moisture reserves more rapidly than in uncropped control. The effect of plant population on soil moisture depletion was more conspicuous within than between rows. Significant differences in water flux and in water uptake from different horizons were observed among various population densities. The total water loss was the highest for the least plant population for the between-row zone, and for the highest population for the within-row zone. Plant population had no effect on tuber and stalk yield.     

中式油炸食品中丙烯酰胺测定及降低方法初探

研究高效液相色谱法分析测定中式油炸食品中丙烯酰胺方法。样品预处理条件:油炸样品粉碎后用0.1%甲酸水溶液(料液比1:5)进行三次重复提取,提取液经高速离心、冷冻、C_(18)固相萃取小柱纯化,最后采用高效液相色谱仪进行测定。测定色谱条件:流动相为甲醇—0.02 mol/L乙酸胺溶液(5:95,v/v)、流速为0.9 ml/min、进样量为20μl、保留时间约4.887 min,检测器为紫外检测器,波长为210 nm、柱温25℃±0.5℃;试验结果表明,丙烯酰胺色谱图峰面积与其浓度在0.5～5.0μg/mL范围内呈良好线性关系,其最低检出限为10 ng/mL,回收率为94.5%～106.5%,相对标准偏差3.2%～4.5%;该法回收率高、精密度好,重复性好。利用该法测定几类市售中式油炸食品和自制油炸食品中丙烯酰胺含量,结果表明,市售中式油炸食品丙烯酰胺检出率为100%,仅含量水平有较大差异;试验也表明,通过优化工艺技术条件和配方如调节pH值或添加抗氧化剂等可降低油炸食品中丙烯酰胺含量。     

Picrate paper kits for determination of total cyanogens in cassava roots and all forms of cyanogens in cassava products

The simple semiquantitative picrate method for the determination of total cyanogens in cassava flour has been modified by increasing the concentration of the picrate solution used to make up the picrate papers, such that a linear Beer's Law relation between absorbance and cyanogen content is obtained over the range 0–800 mg HCN equivalents kg⁻¹ cassava. The method has been adapted to determine the total cyanogen content of cassava roots and the results compared using the picrate method and the acid hydrolysis method for six different roots from five cultivars. The agreement between the results is satisfactory. The simple method for determination of total cyanogens in cassava roots in the field is available in kit form. The methodology has been modified to allow determination of the three different forms of cyanogens present in cassava flour, viz HCN/CN⁻, acetone cyanohydrin and linamarin. HCN/CN⁻ is determined by the picrate method in which cassava flour is reacted with 0.1 M sulphuric acid for 3 h at room temperature. HCN/CN⁻ plus acetone cyanohydrin is also determined by the picrate method after treating cassava flour with 4.2 M guanidine hydrochloride at pH 8 for 3 h at room temperature. A comparison has been made of the amounts of the three cyanogens present in six cassava flour samples using the semiquantitative picrate and the acid hydrolysis methods. The agreement between the two methods is satisfactory, which shows that the new methodology works well. The picrate method for determination of the three cyanogens in cassava flour is also available as a kit. © 1999 Society of Chemical Industry     

热加工食物中糠醛类化合物的剂量安全与减控研究进展

糠醛类化合物作为美拉德反应的中间过程产物之一,在各类热加工食品中广泛存在,其中羟甲基糠醛和糠醛是最常见的2种糠醛类化合物,而反应物种类、加工方式、贮藏条件、水分活度、pH等因素都会影响其产生与积累。目前围绕糠醛类化合物展开的安全性报道并不多见且并未得出一致的结论,少量报道指出了低浓度糠醛类化合物的有益作用和高浓度的不良影响。基于糠醛类化合物在食物中分布的广泛性、多样性,以及潜在的安全风险,考虑到食物中糠醛类化合物的过量暴露可能会给人体带来健康风险,因此有必要对其进行系统的安全性评价并对其含量加以减控。本文旨在归纳包括乳制品在内的各种热加工食物中糠醛类化合物的分布情况,围绕国内外糠醛类化合物的安全性研究现状、减控技术展开综述,以期为食品质量安全控制提供理论参考。