Reduction of cyanide levels during anaerobic digestion of cassava

During the methanogenic fermentation of cassava peel in a plug flow digester, cyanide bound as linamarin in cassava was released as HCN in the fermentation liquor, and then eliminated by the activity of free enzymes and by non-enzymatic reactions. The raw cassava peel contained (1) the enzyme permitting the hydrolysis of linamarin and the liberation of HCN (linamarase), and (2) a cyanide detoxification enzyme (β-cyanoalanine synthase). Cyanide removal was sufficiently fast to maintain a cyanide concentration in the fermentation liquor which was non-inhibitory for the methanogenic microflora.     

Determination of total nitrogen and cyanide nitrogen in cassava

Heating of intact cassava leaves causes liberation of hydrogen cyanide. This phenomenon appears to be caused by β-glucosidase-catalysed decomposition of the cyanogenic glycosides linamarin and lotaustralin. Because of these losses, many previously determined values for total nitrogen in cassava (and other cyanogenic plants) are probably in error as plant materials used for Kjeldahl determinations are often dried at 70–90°C. Liberation of cyanide from intact cassava leaves by heating at 80°C is more complete than liberation by the homogenisation methods commonly used. Homogenisation of cassava leaf tissues with liquid nitrogen or dry ice gives somewhat lower values, and these materials are often not readily available in areas where cassava is studied. The basis of a relatively simple procedure for the isolation of hydrogen cyanide from cassava leaves is suggested.     

Detoxification of cassava during gari preparation

Gari, a fermented cassava product, is widely consumed in many West African countries. The present study was undertaken to investigate the detoxification of cassava during the preparation of gari. The most important processing stages, with regard to elimination of cyanide, were the initial grating of the cassava and the final roasting of the product. The breakdown of linamarin was dependent primarily on the presence of endogenous linamarase and the lactic acid bacteria present during the fermentation were not directly involved in its hydrolysis.     

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.     

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.     

Antioxidant potential of extracts from peels and stems of yellow-fleshed and white cassava varieties

This study focused on the exploration of the potentials of extracting antioxidants from peels and stems of yellow-fleshed and white cassava varieties. The effect of particle size (0.2 and 0.5 mm) and variety on the phenolic content and antioxidant activity was assessed. The peels of the yellow-fleshed cassava variety with a particle size of 0.2 mm showed the highest phenolic content with 681.5 GAE mg 100 g⁻¹ and antioxidant activity of 19% and 425 μM TE g⁻¹ dry matter using DPPH and FRAP assays respectively. The stems of the white cassava with a particle size of 0.2 mm exhibited high phenolic content (442.4 GAE mg 100 g⁻¹) and antioxidant activity of 12.8% and 234 μM TE g⁻¹, better than the stem of the yellow-fleshed cassava. These results indicate that phenolic and antioxidant extractions were influenced by variety, the plant parts and particle size for the antioxidant assays.     

Applicability of DATEM for Chinese steamed bread made from flours of different gluten qualities

BACKGROUD: The diacetyl tartaric acid ester of monoglycerides (DATEM) is an anionic oil‐in‐water emulsifier. The effects of DATEM on bread vary with the type of flour. However, there is insufficient information concerning the effects of DATEM on the qualities of Chinese steamed bread (CSB) even though it is also sold as a CSB improver. RESULTS: The effects of DATEM on CSB varied with flours. The overall qualities of CSB made from either weak or strong wheat flours were improved by the use of the additive, but the effects for medium strong flours were slight and uncertain. The effects of DATEM on individual parameters, such as specific volume, skin and inner structure, were similar to those on overall quality. The addition of DATEM increased the gluten strength and the dough stability of weak flour, whereas it weakened gluten strength and strengthened dough stability of strong flour. The addition of DATEM weakened the gluten strength and gave variable effects on dough stabilities for two medium strong flours. CONCLUSION: The effects of DATEM on CSB quality varied with flour type, by affecting flour characteristics, such as gluten strength, dough stability and lipid content. Copyright © 2008 Society of Chemical Industry     

Heat damage of water biscuits from einkorn,durum and bread wheat flours

To limit heat damage and improve the nutritional properties of bakery products, furosine, glucosylisomaltol, hydroxymethylfurfural, furfural, sugars, α-amylase, β-amylase and colour were assessed during the production of water biscuits from three einkorn, three bread and one durum wheat flours. Heat damage indices, colour and a_w development during baking (from 25 to 75 min duration) of water biscuits from one bread wheat were also studied.     

Carotenoids evolution during pasta,bread and water biscuit preparation from wheat flours

The loss of carotenoids content during food processing was investigated during the production of bread, water biscuits and pasta from refined flours of einkorn, bread and, for pasta only, durum wheat semolina.     

Reduction of cyanide content of cassava flour in Mozambique by the wetting method

Fifty cassava flour samples from Mogincual District of Nampula Province in Mozambique were found to contain, on average, 43 mg HCN equivalents/kg flour (ppm), of total cyanide, which is typical for a year of average rainfall. Five gram samples of the 30 flour samples of highest cyanide content were mixed with water and left for 5 h at 30 °C and it was found that the mean% retention of cyanide was 16.7%. Using 500 g instead of 5 g samples caused an increase in the % retention due to accumulation of the very weak acid, HCN, in the damp flour mass, which also decreased its pH and somewhat reduced the rate of breakdown of linamarin catalysed by linamarase. This problem was overcome by spreading out the damp flour in an approximately 0.5 cm thick layer on a tray, which allowed the release of HCN.     

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.     

豫西南小麦品种馒头制作适宜性研究

馒头是我国居民的传统主食之一。随着馒头机械化生产和市场化销售比例增加,馒头产业得到较快发展。在工业化馒头制作条件下,小麦品种特性及其面粉的馒头制作适宜性,尤其是面粉质量的稳定性,显著影响馒头的产品质量、消费体验及工业化生产的经济效益。选用豫西南地区生产上种植面积大、代表性较强的小麦品种为原料,分析其小麦粉品种的理化特性,研究馒头制作的适宜性及其小麦粉品种质量和馒头特性之间的关系。结果表明,豫西南小麦粉湿面筋含量较高,但面筋指数还有待改进;优质小麦占比有待提高;小麦粉色泽红绿值（a*值）、黄蓝值（b*值）、面筋指数、粉质参数的面团软化度、拉伸参数的拉伸面积及吹泡参数的面团延展性,是评价馒头粉质量的重要参考指标。小麦品种郑麦119、平麦998、陕道198、郑麦1342、郑麦1860比较适合制作馒头。     

Quality of bread made from ozonated wheat (Triticum aestivum L.) flour

BACKGROUND: Ozone gas could be used as a fumigant during grain and flour storage. Experiments were conducted to determine the effects of exposure to ozone and the effects of blending ozone‐treated flour with control flour on flour functionality and bread‐making quality. RESULTS: Ozone treatment oxidized lipids, increased brightness and reduced the yellow hue of flour, and increased peak viscosity and setback viscosity of flour. Bread made from flour treated with ozone at 1500 mg kg^?1 for 4.5 min and bread made from flour blended with 100 g kg^?1 ozonated flour had good crust color and a whiter crumb and had more crumb cells, which resulted in a greater specific volume of the bread when compared with control flour. Flour functionality declined as ozone exposure increased beyond 9 min and as the concentration of ozonated flour increased beyond 200 g kg^?1. CONCLUSION: Bread made from flour exposed to ozone for 4.5 min or flour that contained 100 g kg^?1 fully ozonated flour had greater specific loaf volume and whiter crumb compared to bread made with control flour. Exposure of flour to ozone for longer times (9–45 min) and higher blends (200–1000 g kg^?1) deteriorated quality of bread. Copyright © 2011 Society of Chemical Industry