Cyanogenic potential of fresh and frozen cassava on retail sale in three Irish cities: a snapshot survey

Imported cassava roots can be found on retail sale in several Irish cities and towns. Fresh roots (n = 36 roots) and peeled frozen root pieces (n = 28 packs) were randomly purchased from five retailers in Belfast, Dublin and Limerick and assayed for cyanogenic potential (CNp). Total CNp of fresh root parenchyma varied from 37.5 to 242.9 mg kg^?1 as HCN, dry weight basis – dwb), averaging 104.4 mg kg^?1 HCN (dwb). Total CNp of frozen root parenchyma (n = 28 packs) ranged from 28.5 to 258.6 mg kg^?1 HCN (dwb), averaging 81.7 mg kg^?1 HCN (dwb). Around 78% of fresh roots, and 93% of packs of frozen parenchyma, complied with the Codex Alimentarius definition of ‘sweet’ cassava, but most (86.1% and 64.3%, respectively) exceeded European Union NETTOX recommendations for total CNp. In around one‐third of frozen parenchyma packs, nonglycosidic cyanogens accounted for 83–100% of total CNp. The toxicological implications are briefly discussed.     

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     

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     

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     

Development of extruded snacks using jatobá (Hymenaea stigonocarpaMart) flour and cassava starch blends

The use of the jatobá trees (Hymenaea stigonocarpa Mart) by the timber industry poses an ecological problem in Brazil. The objective of this research was to investigate the use of jatobá flour for the production of snacks by the thermoplastic extrusion of a composite flour consisting of jatobá and cassava starch. Chemical analysis showed that the jatobá fruit provides high-fibre flour (486 g kg⁻¹) with 66 g kg⁻¹ protein, and 398 and 88 g kg⁻¹ of insoluble and soluble fibre, respectively. Such flour is of potential use for the production of high-fibre snacks, allowing for the economical exploitation of the jatobá while preserving the tree. Composite flours with jatobá flour and cassava starch mixtures (150: 850, 300: 700, 450: 550), conditioned to moisture levels of 170, 200 and 230 g kg⁻¹ were processed in a Brabender single-screw extruder. The extrusion conditions were 150 rpm screw speed, 4 mm die diameter and 125, 150 and 175°C of barrel temperatures. The snacks produced were evaluated as to their sensory characteristics and response surface methodology was used to optimise the extrusion process. Response surface and contour diagrams revealed that all mixtures conditioned to 170 g kg⁻¹ moisture and extruded at 150°C produced snacks of acceptable quality, higher levels of jatobá flour leading to significant quality losses with respect to sensory characteristics. © 1998 Society of Chemical Industry.     

PROCESSING TECHNIQUES AND HYDROCYANIC ACID CONTENT OF CASSAVA-BASED HUMAN FOODSTUFFS IN NIGERIA

The hydrocyanic acid content of peeled cassava tubers from various localities in Eastern Nigeria (major cassava growing and consuming area) varied from 26 ± 1.6 to 38 ± 2.6 mg/100g fresh weight. There was no correlation between the cyanide contents of cassava tubers and locality. Processing the tubers with the highest cyanide content into different forms of cassava-based foodstuffs (i.e. Garri, Fufu, cassava cake and cassava chips for cassava salad) consumed in Nigeria resulted in an undetectable amount of cyanide. It is concluded that these cassava-based foodstuffs consumed in Nigeria are free from cyanide toxication, and the incidence of ataxic neuropathy associated with prolonged consumption of cassava as a result of its cyanide content should not be due to prolonged consumption of processed cassava products.     

Microbiological and physico‐chemical characteristics of fufu analogue from breadfruit (Altocarpus altilis F)

Breadfruit was processed into a novel form analogous to retted cassava or fufu. The fruits and cassava tubers were each peeled, comminuted and fermented for 5 days. The slurries obtained were dewatered, oven‐dried at 50?C and then milled to flour. Microbial and physico‐chemical analyses of the flour samples were evaluated. During fermentation, total viable count, lactic acid bacteria count and yeast/mould count of breadfruit increased from 2.9 × 10⁴ to 64 × 10⁵, 24.8 × 10⁵ to 11.9 and 6.7 × 10⁵ to 2.6 × 10⁶, respectively. Corresponding increases were recorded for cassava. The ?Brix of the steep waters increased steadily while the pH decreased over the fermentation period. Pasting characteristics of breadfruit recorded for unfermented breadfruit starch were higher than those of fermented starch (P < 0.05). Processing of breadfruit into a culturally familiar form analogous to fufu will increase the utilisation of breadfruit, especially in several food deficit countries where fermented cassava products are already accepted as staple foods.     

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     

Application of a picrate semi‐quantitative screening assay for the cyanogenic potential of cassava roots at a remote field site

The purpose of this research was to test the accuracy of the picrate screening assay (PSA) in the evaluation of the cyanogenic potential of cassava roots at a remote field site under conditions of unusual difficulty. To do this, a PSA was conducted in the field and compared to data collected previously on five of the same cassava varieties using the Cooke colorimetric enzymic assay. PSA data were collected for 10 different cassava varieties in the Tukanoan Indian village of Yapú in the Colombian Amazon region. The PSA results agree with Tukanoan classifications of cassava; that is, those classified as ‘sweet’ by the Tukanoans generally had low‐to‐moderate parenchymal cyanogenic potential (0–50 mg kg⁻¹ fwb of HCN), while those that they classify as ‘bitter’ had high parenchymal cyanogenic potential (≥100 mg kg⁻¹ fwb of HCN). The PSA results also agree with the data collected using the Cooke colorimetric enzymic assay. The data suggest that the PSA is an appropriate test of the cyanogenic potential of cassava roots in remote field sites. © 2000 Society of Chemical Industry     

Retention of carotenoids in cassava roots submitted to different processing methods

Large genetic variation in carotenoid content has been reported after screening roots from thousands of cassava genotypes. Moreover, these pigments have to withstand different processing methods before cassava is consumed. True retention of β‐carotene from cassava roots that had been boiled, oven‐dried, sun‐dried, shadow‐dried, or used for gari preparation was measured. True retention was also measured after storing for 2 or 4 weeks some of the products of these processing methods. Oven‐drying, shadow drying and boiling retained the highest levels of β‐carotene (71.9, 59.2 and 55.7%, respectively) and gari the lowest (about 34.1%). Higher retention was observed when dried roots were kept as chips rather than as flour. Storage of flour packed in plastic bags under vacuum unexpectedly resulted in higher losses than storage of flour packed in plastic bags without the application of vacuum. Losses were higher during the first 2 weeks and tended to be considerably lower during the second 2 weeks of storage. Copyright © 2006 Society of Chemical Industry     

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.     

The enrichment of Asian noodles with fiber‐rich fractions derived from roller milling of hull‐less barley

Fiber‐rich fractions (FRF) derived from roller milling of waxy (W) and high amylose (HA) starch hull‐less barley genotypes were evaluated for suitability as functional ingredients in fresh and dried white salted (WSN) and fresh yellow alkaline (YAN) noodles. FRF‐W and FRF‐HA both contained over 300 g kg⁻¹ dietary fiber, and over 200 g kg⁻¹ of β‐glucans. Replacement of 250 g kg⁻¹ Canada Prairie Spring White (cv AC Vista) wheat patent flour with the FRF posed no problems in noodle processing, although water absorption had to be substantially increased. All three noodle types enriched with the FRF were significantly darker and contained more brown specks than the wheat flour control noodles. The presence of the FRF reduced cooking time of fresh YAN and WSN by ∼50%. The addition of FRF improved cooked YAN texture, as evidenced by increased firmness and resistance to compression. FRF‐enriched fresh WSN were comparable to the wheat flour control noodles for those parameters, whereas enrichment of dry WSN by FRF imparted less firmness and less chewiness. FRF‐enriched fresh YAN and WSN offer consumer convenience due to shorter cooking time, improved nutritional quality and acceptable cooking quality. These features might make FRF‐enriched noodles sufficiently attractive to health‐conscious consumers to overcome the negative effects of color and appearance Copyright © 2005 Society of Chemical Industry     

An enzymatic assay for the total cyanide content of cassava (Manihot esculenta Crantz).

An enzymatic assay for the cyanide contents of cassava parenchymal tissue (peeled root), cassava peel or cassava leaves is described. The material is homogenised in orthophosphoric acid; filtered through glass-fibre paper and aliquots of the filtrate are neutralised and incubated with exogenous linamarase for 15 min. The cyanogenic glucosides present are hydrolysed to free cyanide which is estimated spectrophotometrically. The acid extraction solution inactivates endogenous linamarase, and assay of aliquots without enzyme treatment gives the free (non-glycosidic) cyanide contents of the extracts. The acid extracts are stable for at least 4 days at 4°C, and the steam-distillation/aspiration of earlier methods is unnecessary. The detection limit is < 0.01 mg (0.1 parts 10^?6) cyanide per 100 g fresh weight and peeled root, and 40-50 samples per day can be handled easily. Analyses of eight cultivars indicated longitudinal and radial cyanide gradients in the roots, and the problem of sampling bulky roots is discussed.     

The Effect of Root Maturity, Preprocess Holding and Flour Storage on the Quality of Cassava Biscuit

Effect of root maturity (12 and 23 months) and flour storage on physical, chemical, and sensory attributes of cassava biscuits was evaluated. Pulp and flour of 12 months were higher than the 23 months mature roots. Moisture, crude protein, crude fat, and cyanide contents of the cassava flour varied between 10.1% and 10.3%, 2.2% and 2.4%, 0.2% and 0.3%, and 12.1 and 13.4 mg HCN/100 g, respectively. Diastatic activity of the flour ranged from 115 to 243 mg maltose for fresh and roots stored for 3 days. Water-holding capacity of the roots and peak viscosity of flours decreased during storage. Sensory results showed that cassava biscuits were acceptable and compared favorably with the wheat biscuits.     

Influence of drying mode on iridoid bitter constituent levels in gentian root

Root samples of wild gentian (Gentiana lutea L) were harvested from six localities (altitude 970 m to 1350 m) from May to November 2000. Each batch of roots was split into three: fresh roots, naturally dried roots (ambient air) and artificially dried roots (40 °C). In all the samples, levels of iridoid bitter constituents and of xanthone coloured compounds were determined by HPLC. The mean total iridoid content in the fresh roots was 102.4 g kg^?1 in dry matter (DM). The mean level of the principal bitter compound gentiopicroside was particularly high at 81 g kg^?1 DM. Loganic acid, not previously reported in G lutea, was the second most abundant bitter compound at a mean level of 14.3 g kg^?1 DM. Swertiamarin was present at 5.4 g kg^?1, with another minor unidentified iridoid. Levels of iridoid compounds were strongly dependent of the drying mode. These amounts were 88.5 g kg^?1 DM in artificially dried roots and 62.5 g kg^?1 DM in naturally dried roots, mostly owing to a marked decrease in gentiopicroside. The temperature of 40 °C preserved the bitter compounds and the bitterness of fresh gentian roots. The amount of coloured xanthones was relatively low at 3.3 g kg^?1 and did not change with the drying mode. Copyright © 2004 Society of Chemical Industry     

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.     

Cyanide content in whole-root chips of ten cassava cultivars and its reduction by oven drying or sun drying on trays

The effect of sun drying on trays for 48 hr and of oven drying in an air-forced oven at 60°C for 24 hr on the cyanide content of chips of ten cassava varieties was studied. Fresh cassava chips from whole roots of these varieties showed significantly different total cyanide contents among them with values in the range of 100–900 mg/kg on a dry matter basis; most of the varieties studied exhibited cyanide contents in the range of 200–600 mg/kg. The free cyanide proportion in the fresh chips was in the range of 30–40% of their total cyanide. Sun and oven drying reduced the cyanide content in the dried chips to approximately 15–30% of the initial cyanide content of fresh chips. In addition, the free cyanide content in dried chips accounted for approximately 60–80% of their total cyanide value.     

Nicotine determination in mushrooms by LC–MS/MS with preliminary studies on the impact of drying on nicotine formation

A problem concerning significant amounts of nicotine in dried wild mushrooms (mainly Boletus edulis from China) has been reported to the European Commission. As a consequence, the European Food Safety Authority (EFSA) proposed temporary maximum residue levels (MRLs) of 0.036 mg kg^?1 for fresh wild mushrooms and 1.17 mg kg^?1 for dried wild mushrooms (2.3 mg kg^?1 for dried ceps only). The EFSA also highlighted the necessity for a monitoring and testing programme to be launched by food business operators at the start of the 2009 harvest season. In the present study, a quick and sensitive analytical method for routine analysis of nicotine in fresh and dried mushrooms was developed and validated by a single-laboratory procedure. The method, which employs an LC–MS/MS system and (±)-nicotine-d ₄ as internal standard, has a limit of quantification of 6 and 60 µg kg^?1 for fresh and dried product, respectively. Analyses of samples spiked with different levels of nicotine showed recoveries ranging from 107 to 122%, with relative standard deviations of 2.9–10.1% depending on the spiking level. The combined uncertainties, calculated at a low level for frozen (0.015 mg kg^?1) and a high level for the dried (2 mg kg^?1) matrix, were 13 and 10%, respectively. Application of the method to real samples of mushrooms purchased on the market or obtained from local producers showed nicotine levels ranging 0.01–0.04 and 0.1–4.5 mg kg^?1 in fresh/frozen and dried matrices, respectively. To establish reasons for the unexpectedly high levels of the nicotine in dried matrices, preliminary laboratory experiments involving drying mushrooms were performed under various conditions.     

Flour,starch and composite breadmaking quality of various cassava clones

Bread was made using a straight-dough baking process from a local soft wheat flour partially substituted at four levels with flour from nine different cassava (Manihot esculenta, Crantz) clones. The physicochemical properties of the blended flouts, including starch quality, were determined and related to dough rheology, bread volume and crumb characteristics. Breadmaking quality at substitution levels of 100 and 200 g kg^?1 of mixed flour was reliably predicted from the cassava flour diastatic activity only. Flours with relatively high diastatic activities, ie above ～ 145 mg of maltose, had deleterious breadmaking effects. Baking absorption effects were more critical at substitution levels of 300 and 400 g kg^?1. Cassava flour diastatic activity was highly dependent on the moisture contents of the respective tuberous roots, and affected the extent of starch gelatinisation in the breadcrumbs.     

CHARACTERIZATION OF SURFACE AUXIN RESIDUE IN GREENHOUSE TOMATOES (LYCOPERSICON ESCULENTUM)

Greenhouse tomato samples (n = 20) was analyzed before and after peel removal in order to determine surface auxin residue. Mean 4‐CPA residue levels of greenhouse tomatoes with and without peels were 0.383 ± 0.123 mg kg^?1 and 0.241 ±0.085 mg kg^?1, respectively. This difference (36 ±13%) was statistically significant. The frequency distribution curve of tomatoes with peel had a peak point at 4‐CPA reside interval of 0.4‐ < 0.5 mg kg^?1 tomato, and shifted back to 4‐CPA residue interval of 0.2‐ < 0.3 mg kg^?1 for tomatoes without peel. Percentage of samples having 4‐CPA level lower than the critical concentration of 0.5 mg kg^?1 was 80% before peel removal, but increased to 100% upon being peeled. The mean 4‐CPA residue of peels was roughly estimated to be 3.449 mg kg^?1 peel based on peeled versus nonpeeled fruit residue.