A survey of total hydrocyanic acid content in ready-to-eat cassava-based chips obtained in the Australian market in 2008

Cassava (Manihot esculenta Crantz) is a widely consumed food in the tropics that naturally contains cyanogenic glycosides (cyanogens, mainly composed of linamarin, acetone cyanohydrin, and hydrocyanic acid). If cassava is not adequately processed to reduce the level of cyanogens prior to consumption, these compounds can lead to the formation of hydrocyanic acid in the gut. Exposure to hydrocyanic acid can cause symptoms ranging from vomiting and abdominal pain to coma and death. In 2008, a survey of ready-to-eat (RTE) cassava-based snack foods was undertaken to determine levels of cyanogens measured as total hydrocyanic acid. This survey was undertaken in response to the New South Wales Food Authority being alerted to the detection of elevated levels of cyanogens in an RTE cassava-based snack food. This survey took 374 samples of RTE cassava chips available in the Australian marketplace. Significant variation in the levels of total hydrocyanic acid were observed in the 317 samples testing positive for cyanogens, with levels ranging from 13 to 165 mg of HCN equivalents per kg (mean value, 64.2 mg of HCN eq/kg for positive samples). The results from this survey serve as a timely warning for manufacturers of RTE cassava chips and other cassava-based snack foods to ensure there is tight control over the levels of cyanogens in the cassava ingredient. Evidence from this survey contributed to an amendment to the Australia New Zealand Food Standards Code, which now prescribes a maximum level for hydrocyanic acid in RTE cassava chips of 10 mg of HCN eq/kg, which aligns with the Codex Alimentarius Commission international standard for edible cassava flour.     

Industrial Demand for Cassava Starch in India

Cassava (Manihot esculenta crantz) is a staple food crop cultivated in several developing countries. Cassava is consumed either directly as cooked tubers or as the products prepared from cassava. Cassava in India is used mainly in the human consumption, industrial and animal feed sectors. In India nearly 60% of cassava is used industrially in the production of sago, starch and dry chips. The presented study has clearly indicated that the future of cassava in India lies in its diversified uses in the industrial sector. The projected demand is predominantly in the adhesive sector, especially in the corrugation gums and paper conversion industry, and in the paper industry. The projected demand‐supply gap in the industrial sector is expected to be 1.5×10⁶ t of cassava tubers requiring another 750 000 ha to be brought under cassava cultivation. New and potential areas in the non‐traditional cassava‐growing states are to be considered for area expansion.     

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.     

Chronic poisoning by hydrogen cyanide in cassava and its prevention in Africa and Latin America

Africa produces more than 30 million tons of cassava on about 5 million hectares (6 tons per hectare). Approximately 80% of the root production and 70% of the harvested area are from Western Africa. Recent reports suggest that the ingestion of poorly processed cassava roots is associated with the incidence of an ataxic neuropathy (konzo) in African countries. When cassava-based diets are not supplemented with good sources of protein and iodine, goiter and rickets are also prevalent. In certain countries of Africa where the rate of ataxic neuropathy is high, the incidence of thyroid disorders is also high. Persons consuming poorly processed cassava in large quantities are susceptible to neuropathologies caused by cyanide. Cyanide detoxification in the body is impaired by protein deficiency. When properly processed, the root of cassava is safe and cheap as a major dietary energy source for humans and domestic animals; however, a cassava-based diet will lack sufficient protein and will be particularly deficient for the growth and development of children unless it is supplemented by protein from animal, including fish, or legume sources. Cassava leaves, if they are appropriately cooked, can be a useful source of some nutrients.     

Hydrocyanic acid levels in fermented cassava

The extent of loss of hydrocyanic acid during the fermentation of cassava tubers selected from both sweet and bitter varieties in the traditional method (whole unpeeled tubers) compared with the fermentation of peeled tubers and crushed pulps with or without the addition of water. Although the traditional fermentation is terminated after 3–4 days, in this study the fermentation was allowed to proceed for 8 days. Loss of cyanide from the whole tubers was 8047% after 8 days and was only 51–53% after 4 days. Loss of cyanide from the whole sweet tuber was not significant after 5 days. The loss of cyanide from the peeled tubers was comparable to the whole tubers after 8 days of fermentation. However, there was a marked decrease in free cyanide in the 1st day of fermentation of the peeled tubers compared to whole tubers. The loss in cyanide in the crushed pulp, which occurred primarily in the 1st day, appears to be due to the action of endogenous linamarase rather than hydrolysis by fermentation. When water is added to the crushed pulp the reduction in cyanide was 83–91% with marked decrease in bound cyanide in the 1st day of fermentation. It seems that autohydrolysis is enhanced by addition of water to the crushed pulp.     

Effect of processing methods on quality and acceptability of fufu from low cyanide cassava

The effects of steeping whole and grated tubers and of periodic change of water during steeping on the quality and acceptability of fufu from low-cyanide cassava were evaluated. Steeping increased the acidity and reduced the pH and cyanide content of cassava. Grating the tuber before steeping improved aroma, and periodical change of water during steeping improved taste, colour and texture of fufu over that produced by the traditional method. Fufu from low-cyanide cassava had an acceptability similar to that of fufu from high-cyanide cassava. However, oven drying of the flour significantly reduced acceptability of fufu.     

Cassava (Manihot esculenta Crantz) and Yam (Dioscorea spp.) Crops and Their Derived Foodstuffs: Safety,Security and Nutritional Value

Cassava (Manihot esculenta Crantz) and yam (Dioscorea spp.) are tropical crops consumed by ca. 2 billion people and represent the main source of carbohydrate and energy for the approximately 700 million people living in the tropical and sub-tropical areas. They are a guarantee of food security for developing countries. The production of these crops and the transformation into food-derived commodities is increasing, it represents a profitable business and farmers generate substantial income from their market. However, there are some important concerns related to the food safety and food security. The high post-harvest losses, mainly for yam, the contamination by endogenous toxic compounds, mainly for cassava, and the contamination by external agents (such as micotoxins, pesticides, and heavy metal) represent a depletion of economic value and income. The loss in the raw crops or the impossibility to market the derived foodstuffs, due to incompliance with food regulations, can seriously limit all yam tubers and the cassava roots processors, from farmers to household, from small-medium to large enterprises. One of the greatest challenges to overcome those concerns is the transformation of traditional or indigenous processing methods into modern industrial operations, from the crop storage to the adequate package of each derived foodstuff.     

Chemical assay of cyanide levels of short-time-fermented cassava products in the Abraka area of Delta State,Nigeria

Five cassava products, commonly consumed in and around the Abraka area of Delta State, Nigeria were analysed for their cyanide levels. This study, to determine safe levels of cyanide, became necessary as the fermentation time in the processing of these products has been observed to be drastically shortened to as low as 6 h for quick economic returns. In all the products, the cyanide levels were reduced from 30.0–58.0 mg HCN equivalent kg⁻¹ of product. These levels fall below the reported 30.0 mg HCN equivalent kg⁻¹ safe (fresh weight) of raw cassava to 5.4–24.0 mg HCN equivalent kg⁻¹ level for cassava products. Nevertheless, some of the products containing up to 20.0–26.5 g HCN equivalent kg⁻¹ of products are dangerous to health as these levels are higher than the 20.0 mg HCN equivalent kg⁻¹ safe level recommended by the Standard Organization of Nigeria. The current practice of short-time fermentation should therefore be discouraged.     

Effects of cassava processing methods on antinutritional components and health status of children

This study was conducted to evaluate cassava processing methods in Nigeria, its antinutritional components and the possible impact on the health status of children. The traditional method of cassava processing involved peeling of cassava tubers with a knife, manual grating, dewatering with logs of wood and/or stones, sieving with a cane‐woven sieve and frying in a local metal fryer on a wood fire. In contrast, the modern method involved the use of knives for peeling, a mechanical grater, a hydraulic press for dewatering, iron sieves for sieving and an improved metal fryer for frying on a coal fire. The products of both methods included gari (accounting for 70% of Nigeria's total cassava consumption) and lafun. The intake of gari and other foods in 129 3–5‐year‐old children in Benin City, Nigeria was also assessed based on a food frequency questionnaire. The children were classified into normal and protein‐deficient groups using lower/middle/upper‐arm circumference and clinical features of malnutrition. Based on the number of households in villages around Benin City who were involved in cassava processing, 90% used the traditional processing method compared with 10% using the modern method, although the latter controlled the commercial production and sale of gari. There were significantly (P < 0.05) higher intakes of protein and energy in normal compared with protein‐deficient children, but the latter group obtained higher percentages of protein and energy from gari. In addition, the correlation between the amount of gari consumed and clinical scores of malnutrition was low (R² < 0.2). This may be due to the children consuming gari from both methods and also from different sources. The average gari intake for these children was 320 g day^?1 and HCN levels may be as high as 10.24 mg day^?1. Some children who are exposed to these levels with poor nutritional status and lack of access to food varieties may develop sublethal effects in the short term. The higher protein intake by the normal children may also reduce the toxicity of HCN. We conclude that methods of processing cassava have profound effects on HCN retention and chemical composition of cassava products. In addition, the modern processing method is more efficient than the traditional method, with significantly reduced processing losses, labour input and levels of HCN. The HCN content in combination with the quantity and quality of protein in the diet has significant impact on the health status of children. Therefore, in susceptible children with poor nutritional status who consume inadequately processed cassava products with limited food choice, these may predispose them to the effects of HCN and thiocyanate. © 2002 Society of Chemical Industry     

Analysis of various Nigerian foodstuffs for crude protein and mineral contents by neutron activation

Various Nigerian foodstuffs were analysed for crude protein and some important nutrient minerals, Ca, Fe, K and P, using the neutron activation technique. The protein content of the staple foods, cassava and its products, cocoyam, yam, rice and plantains, varies from about 1% to 12·8%, while the grains, maize, guinea corn and millet, as well as African breadfruit seeds and some popular vegetables, have a relatively high protein content. Corrections for the relevant reaction interferences in nitrogen determination were carried out. The precision of the sample analyses varied in the range ± 2·1 to ± 6·3%.     

Moisture-pressure combination treatments for cyanide reduction in grated cassava

Several cyanide-associated health disorders have been linked with frequent consumption of mildly toxic cassava (Manihot esculenta crantz) products in individuals on a low-protein diet. Production of bread from cassava often involves application of prolonged physical pressure (pressing) to the freshly grated root for several hours. This study aimed to determine effects of pressure and wetting on grated cassava. Six treatments were applied: confining pressure for 12 h, wetting for 4 h at 25 °C, 2 h at 25 °C, 2 h at 40 °C, and 2 h at 50 °C, or each of the above followed by pressure for 12 h. Treatments released cyanide from samples in the order: 2-h wet at 50 °C + pressing >4-h wet at 25 °C + pressing = 2-h wet at 40 °C + pressing >2-h wet at 25 °C + pressing = 4-h wet at 25 °C >12-h pressing. Wetting for 2 h at 50 °C followed by pressure for 12 h reduced cyanide levels by at least 20% more than that of any other treatment. The combination of moisture and pressure enhanced the contact time between linamarin and linamarase to increase the release of hydrogen cyanide.     

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.     

Processing factors affecting the level of residual cyanohydrins in gari

Intake of cyanogens in gari, a food processed from cassava roots, is implicated in the causation of tropical ataxic neuropathy (TAN). This neurological syndrome is endemic in some communities in south‐western Nigeria. Studies have shown that methods of processing cassava roots determine the quantity of cyanogens in gari. This study was conducted to investigate the effects of the method of dewatering and the duration of fermentation on cyanogens in gari. Cassava roots (400 kg) were peeled, washed, grated and divided into 14 woven polyethylene sacks. The mash in seven of the sacks was dewatered continuously during fermentation, while the mash in the remaining seven sacks was fermented without dewatering, but dewatered at the end of fermentation. Cassava mash from each treatment was roasted into gari at 24 h intervals up to 168 h. Mean cyanohydrin content in gari roasted from cassava mash dewatered continuously during fermentation was 10.8 mg HCN eq kg^?1 dw (CI 9.7–11.9), while mean cyanohydrin content in gari roasted from cassava mash dewatered after fermentation was 6.3 mg HCN eq kg^?1 dw (CI 5.3–7.4). Mean linamarin content was 4.0 mg HCN eq kg^?1 dw (CI 3.1–4.9) and mean HCN content was 1.6 mg kg^?1 dw (CI 1.3–1.9) in gari roasted from cassava mash dewatered continuously, while mean linamarin content was 3.2 mg HCN eq kg^?1 dw (CI 2.3–4.0) and mean HCN content was 1.2 mg kg^?1 dw (CI 0.9–1.5) in gari roasted from cassava mash dewatered after fermentation. The method of dewatering cassava mash and the duration of fermentation were significantly associated with the level of cyanohydrin in gari (p < 0.001). This study shows that dewatering of cassava mash continuously during fermentation contributes to the dietary cyanide load in TAN‐affected communities. © 2002 Society of Chemical Industry     

Deep‐fat frying of cassava: influence of raw material properties on chip quality

Thirteen cultivars of cassava (Manihot esculenta Crantz) were used to obtain chips by deep frying slices of fresh cassava flesh in palm oil. The cultivars were representative of three different levels of four major characteristics (water, cyanide, starch and amylose content) in parenchyma. The effects of raw material composition and crop age (10 and 12 months) on mass transfer (dehydration and oil uptake), texture and colour were assessed for 1.5 mm thick chips with a final water content of 0.04 kg kg⁻¹ wet basis, corresponding to a water activity of about 0.3. Frying time varied from 70 to 90 s and oil bath temperature from 140 to 160 °C. All cultivars gave a high frying yield (>0.5 kg chips kg⁻¹ fresh cassava) and a chip fat content of between 0.23 and 0.37 kg kg⁻¹ wet basis, with the highest frying yields and lowest fat contents being obtained from roots with the lowest water content and cyanide content. The intensity of darkening reactions increased in accordance with the level of reducing sugars, while the rigidity modulus of the chips was negatively correlated with the fibre content. The other characteristics (starch, amylose and total sugar content) were either not or poorly correlated with any of the chip quality parameters studied. Cyanoglucosides were only partially eliminated during frying (over 40% retention), so cultivars with a high cyanide content gave bitter chips. For a similar composition, drying rates and cooking rates were much lower when crop age increased. This could be attributed to a structural effect characterising crop age. © 2000 Society of Chemical Industry     

Bitterness of cassava: Identification of a new apiosyl glucoside and other compounds that affect its bitter taste

Compounds extracted by methanol from cassava parenchyma and cortex have been separated on a preparative HPLC column and identified by ¹H and ¹³C NMR spectroscopy. A new compound isopropyl-β-D -apiofuranosyl-(1 → 6)-β-D -glucopyranoside (IAG, structure I ) has been found as well as small amounts of phenylalanine and tryptophan. The composition of another HPLC fraction has not been elucidated. The amounts of the identified compounds and of linamarin, lotaustralin, citrate, malate and the various sugars present in cassava have been determined by HPLC methods. The threshold levels of bitterness of aqueous solutions of linamarin, lotaustralin and IAG, have been determined and together with published data on L -phenylalanine and L -tryptophan have allowed our evaluation of their contributions to the bitterness of cassava. Linamarin is the sole contributor in the parenchyma but (with two cultivars out of six studied) IAG contributes more to the bitterness of the cortex than does linamarin. The perception of bitterness of linamarin solutions is confounded in the presence of neutral citrate and malate which have a sour taste. These modify the taste of cassava tubers. There are many compounds that contribute to the taste of cassava tubers, hence it is not surprising that the bitterness of cassava is not always correlated positively with the cyanide potential.     

Cassava foliage: Chemical composition,cyanide content and effect of drying on cyanide elimination

The chemical composition and cyanide concentration in the foliage of four cassava cultivars (M Col 113, M Col 22, M Col 1684, CM 342–170) were evaluated at four plant ages (6, 8, 10 and 12 months). The effect on cyanide elimination of sun-drying on a concrete floor and of oven-drying at 60°C was also studied, including some observations on the tannin content of dried foliage. The proximal composition, calcium and phosphorus contents, as well as the amino acid composition of dried cassava foliage compared favourably to that of sun-cured lucerne meal. In most cases, foliage from 6-to 12-month-old plants contained 25 to 30% dry matter, and as dried foliage had 13 to 20% crude protein and 16 to 20% crude fibre. Crude protein and crude fibre were the two chemical constituents which varied the most with plant age. The average gross energy of dried cassava foliage was 4.12 kcal kg^?1 with a range of 3.90 to 4.35 kcal kg^?1. Sun-drying eliminated more cyanide than oven-drying (82 to 94% vs 68 to 76%, respectively) and in addition, most of the cyanide in sun-dried foliage was free cyanide (62 to 77%) whereas only 24 to 36% was found as such in oven-dried foliage. Sun-dried foliage samples had consistently lower tannin content than the corresponding oven-dried samples.     

The effects of variety,drying procedure,fineness of grinding and dietary inclusion level on the bioavailability of Cassava (Manihot esculenta crantz) starch

The bioavailability of raw cassava starch from dried, whole roots, as affected by a number of variables, both inherent and processing-induced, was determined in a series of feeding trials using the rat as a test animal. Apparent starch digestibility was in excess of 99% and was unaffected by cassava variety, cyanide content, drying process, fineness of grinding, dietary inclusion level (up to 50% of the diet) and age of the animal. A high level of residual cyanide (406.6 mg kg^?1 dried cassava chips) reduced feed intake and weight gain. Since the floor-drying procedure, whilst effectively reducing the cyanide to an acceptable level, was without effect on the digestibility of cassava starch, it is recommended that this process be adopted for drying high cyanide cultivars of cassava destined for the animal feed market. This will allow cassava to be incorporated in the diet at a higher inclusion level with no undesirable effects on animal performance.     

Composition of some tropical tuberous foods

Four tropical root tubers were evaluated for their chemical compositions and amino acid patterns. These were winged bean (Psophocarpus tetragonolobus (L.)DC., yam, sweet potato and cassava (Manihot utillisima, Pohl.). Winged bean tubers had protein contents ten times higher than those of cassava and sweet potato and five times higher than yam and contained a high level of carbohydrates. The minerals analysed were about the same in concentration but winged bean tubers had about three times more iron than other root tubers.Although cassava roots have the highest content of S-containing amino acids, winged bean roots have the highest values for lysine, tyrosine, tryptophan and threonine. The total content of essential amino acids is much greater in winged bean tubers than in the other tuberous roots.     

The effect of storage on the oxalate content of New Zealand grown oca

Four lines of oca, No. 38 and 41, Inca Gold and Market were grown in four replicated plots and the soluble oxalate content was determined on the freshly harvested tubers and tubers that had been stored for 6 weeks at 16.4 ± 0.5 °C. The mean dry matter content of freshly harvested tubers was 14.3 ± 0.5 g 100 g^?1 fresh weight (FW), and after storage was 14.6 ± 0.5 g 100 g^?1 FW. The mean soluble oxalate content of freshly harvested tubers was 162.1 ± 8.8 mg 100 g^?1 FW, and, after 6 weeks storage, 173.5 ± 0.9 mg 100 g^?1 FW. The different cultivars behaved differently during storage, the soluble oxalate content of Inca Gold tubers fell 7.2% while the soluble oxalate content of the other three cultivars increased (mean 13%).     

Pre-treatment effect on the nutritional and functional properties of selected cassava-based composite flours

The low protein and lack of gluten in cassava (Manihot esculenta Crantz) are disadvantageous for its use for product development and is overcome through the use of composite flours incorporating cereal and/or legume flours. The functionality and nutritional attributes of cassava flour were altered in the present study by pre-treatment with termamyl and green gram amylase, pre-gelatinization and subsequent blending with cereals, legumes, bran sources etc. Malting of cassava flour with termamyl followed by pre-gelatinization reduced the starch and increased the sugar content of the mixes. Pre-gelatinization had little effect on the crude protein of the mixes; nevertheless, the fat content was higher by 0.15–1.0 units. Energy content was around 1176 and 1217 KJ/100 g for the rice bran added mixes from malted cassava, which slightly increased in the respective pre-gelatinized cassava mixes. The peak viscosity of termamyl treated cassava-based flour mixes was much lower than the respective gram amylase based mixes, indicating that the latter had much less amylolytic activity than termamyl and pre-gelatinization further reduced the viscosity. The very low viscosity for the enzyme treated cassava-based mixes was due to the inability for retrogradation of the hydrolyzed starch. Significant improvement in in vitro starch digestibility (IVSD) (enhancement by 5.0–16.0 units in termamyl treatment vs 5.0–9.0 units in gram amylase treatment) was observed for the pre-gelatinized mixes. Lowest IVSD (25–29 units) was for the two bran based mixes, suggesting its use in the nutrition therapy for controlling obesity linked diseases.

Industrial relevance

With the development in human society, the incidence of chronic diseases like diabetes, cancer, cardiovascular problems and conditions like obesity contributing to several diseases is on the increase. This has led to an increasing awareness and research efforts on the development of functional foods, pharmafoods etc, which have wide potential application in medical nutrition therapy. The present work aims at improving the nutritional and functional attributes of cassava through fortification with cereal and/ or legume flours, bran sources etc. and through pre- treatment with enzymes to improve the functionality and reduce the energy content. The study led to the development of cassava based composite flours with low starch digestibility, high protein content and low energy content which could be effectively utilized for developing designer foods for obese and diabetic people. Enhanced digestibility of pre- gelatinized malted flours from cassava finds potential application for the development of foods for geriatric and convalescent people.