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     

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     

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.     

Initial evaluation of a field-friendly extraction procedure for the enzymatic assay of cassava cyanogens

A novel ‘field friendly’ extraction procedure has been developed for the enzymatic colorimetric determination of cyanogenic potential (CNP) in fresh cassava root parenchyma. The novel procedure does not require electrical power or vacuum, and employs inexpensive lightweight equipment, making it suitable for remote field sites. Testing of the procedure involved ten fresh roots (24–80 mg kg^?1 total CNP, as HCN, fresh basis). From the parenchyma of each root, one extract was made using the novel procedure, and a ‘control’ extract was made using a traditional laboratory‐based procedure. Total CNP assay of the extracts indicated strong (y = mx) or very strong (y = mx + c) correlation of results obtained using the two procedures, while a very strong correlation (y = mx) was obtained for free HCN. Based on this preliminary evidence, the novel procedure is satisfactory at least for total CNP assay of fresh low‐CNP cassava roots.     

Cyanogenic potential of randomly sampled fresh and processed cassava on retail sale in Singapore

A random sample of fresh cassava roots and cassava products, purchased at various retail outlets in Singapore during 2016–2017, had total cyanogenic potential (CNp–expressed as mean ± standard deviation, mg kg⁻¹ HCN, fresh weight basis) as follows: fresh roots (n = 66) from three SE Asian countries, 59.0 ± 19.2; peeled chilled root pieces from Malaysia (20 × 1-kg packs), 38.5 ± 16.5; cassava flour from Indonesia (8 × 1-kg packs), 11.7 ± 8.2; dried Indonesian chips for home frying (5 × 250 g packs), 61.6 ± 16.5; one pack (120 g) of Malaysian ready-to-eat (RTE) chips, 17.1 ± 3.2. CNp in all flour and RTE chips was below 20 mg kg⁻¹. The majority of fresh roots (59.1%) and packs of dried chips (80%), and 15% of packs of peeled chilled root parenchyma, exceeded the Codex Alimentarius limit (50 mg kg⁻¹) for ‘sweet’ (boil-and-eat) cassava.     

Cyanogenicity of cassava varieties and risk of exposure to cyanide from cassava food in Nigerian communities

BACKGROUND: High‐cyanogenic cassava varieties are cultivated in many tropical communities that are free of neurological syndromes attributed to consumption of cassava foods. This study was done in four geographical areas of Nigeria (northern, southwestern, southeastern and an area endemic for ataxic polyneuropathy) to determine if cyanogenicity of cassava is associated with geographical area, altitude or level of cyanogenic compounds in gari, a popular cassava food in West Africa. RESULTS: Mean levels of cassava cyanogens were 153, 127, 68 and 65 mg HCN equivalents (eq.) kg^?1 dry weight (DW) in the endemic, southeastern, southwestern and northern areas respectively (P < 0.0001), while mean levels of gari cyanogens were 9, 4, 7 and 13 mg HCN eq. kg^?1 DW in the respective areas (P < 0.0001). The mean altitude was 35 m in the endemic area, 55 m in the southeastern area, 220 m in the southwestern area and 273 m in the northern area (P < 0.0001). Altitude was associated with cyanogenicity of cassava in univariate and multivariate models (P < 0.0001). One hundred and twenty‐six (93%) farmers and 255 (77%) processors did not perceive cassava or its food products as toxic. CONCLUSION: The findings indicate that cyanogenicity of cassava is determined by environmental factors rather than by conscious selection of varieties by farmers. Farming high‐cyanogenic cassava is not associated with high levels of residual cyanogens in gari. Cassava is not perceived as toxic by farmers and processors. Copyright © 2008 Society of Chemical Industry     

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     

Sensory evaluation of new lines of oca (Oxalis tuberosa) grown in New Zealand

Five new and one local cultivar of oca or New Zealand yam (Oxalis tuberosa) were evaluated by a consumer-type panel for appearance, flesh colour, flavour, texture and overall acceptability of raw, steamed and baked tubers. The intensity, ‘just right’ or liking scores were analysed using the proportional odds model. Skin and flesh colour of tubers were also measured objectively using a colorimeter. For raw oca, panellists preferred bright red tubers, but size was also important. Flesh colour, bitterness and mealiness were important variables which described the overall acceptability of steamed oca, while only flesh colour and bitterness were important variables for baked oca. Cultivars which had flesh colour described as ‘bright yellow’, flavour as ‘no bitter taste’, and a ‘very slightly mealy’ texture were more preferred. Cultivars with higher yellow/blue (b¹) and chroma (c¹) values for cooked tuber skin and flesh colours were more acceptable.     

Limonoids and Flavonoids in Juices of Oroblanco and Melogold Grapefruit Hybrids

Oroblanco and Melogold are hybrids obtained from pummelo and grapefruit. Limonoids and flavonoids in both juices were analyzed. Oroblanco and Melogold juices contained low concentrations of limonoid glucosides, an average of 99 and 59 ppm, respectively. However, they contained relatively high concentrations of bitter limonoid aglycones, limonin and nomilin, at levels above the limonin bitterness threshold. For comparison, limonoid glucosides in juices of grapefruit, another pummelo hybrid, were also analyzed. Limonin glucoside was the major limonoid glucoside in all juices analyzed. Nomilin glucoside and nomilinic acid glucosides were also present. Oroblanco and Melogold juices contained bitter flavonoids normally found in grapefruit and pummelo including naringin, neohesperidin and poncerin in total amount of 440 ppm in Oroblanco juice and 495 ppm in Melogold juice. They also contained several other nonbitter flavonoids found in grapefruit.     

Recombinant yeast as a functional tool for understanding bitterness and cucurbitacin biosynthesis in watermelon (Citrullus spp.)

Cucurbitacins are a group of bitter‐tasting oxygenated tetracyclic triterpenes that are produced in the family Cucurbitaceae and other plant families. The natural roles of cucurbitacins in plants are probably related to defence against pathogens and pests. Cucurbitadienol, a triterpene synthesized from oxidosqualene, is the first committed precursor to cucurbitacins produced by a specialized oxidosqualene cyclase termed cucurbitadienol synthase. We explored cucurbitacin accumulation in watermelon in relation to bitterness. Our findings show that cucurbitacins are accumulated in bitter‐tasting watermelon, Citrullus lanatus var. citroides, as well as in their wild ancestor, C. colocynthis, but not in non‐bitter commercial cultivars of sweet watermelon (C. lanatus var. lanatus). Molecular analysis of genes expressed in the roots of several watermelon accessions led to the isolation of three sequences (CcCDS1, CcCDS2 and ClCDS1), all displaying high similarity to the pumpkin CpCPQ, encoding a protein previously shown to possess cucurbitadienol synthase activity. We utilized the Saccharomyces cerevisiae strain BY4743, heterozygous for lanosterol synthase, to probe for possible encoded cucurbitadienol synthase activity of the expressed watermelon sequences. Functional expression of the two sequences isolated from C. colocynthis (CcCDS1 and CcCDS2) in yeast revealed that only CcCDS2 possessed cucurbitadienol synthase activity, while CcCDS1 did not display cucurbitadienol synthase activity in recombinant yeast. ClCDS1 isolated from C. lanatus var. lanatus is almost identical to CcCDS1. Our results imply that CcCDS2 plays a role in imparting bitterness to watermelon. Yeast has been an excellent diagnostic tool to determine the first committed step of cucurbitacin biosynthesis in watermelon. Copyright © 2014 John Wiley & Sons, Ltd.     

The glucosinolates sinigrin and progoitrin are important determinants for taste preference and bitterness of Brussels sprouts

The glucosinolates, sinigrin and progoitrin, are related to the bitterness observed in Brussels sprouts. The role of these glucosinolates in taste preference for Brussels sprouts (Brassica oleracea var gemmifera) was studied with two different consumer taste panels and an analytical panel. Four different taste trials were conducted between 1989 and 1995 to study the role of sinigrin and progoitrin on taste preference and bitterness of sprouts. Sinigrin and progoitrin correlated negatively with taste preference of sprouts when their combined content was higher than 2·2 g kg⁻¹. Under these conditions the overall preference for different Brussels sprouts cultivars, in two different trial designs, was accounted for, respectively, 64 (Novartis Seeds BV) and 86% (TNO) by the contents of the glucosinolates sinigrin and progoitrin. In two additional trials, in which the combined content of sinigrin and progoitrin of all cultivars was below 2·2 g kg⁻¹, no relationship between taste preference and the content of both glucosinolates was observed. In the latter trials the content of sinigrin and progoitrin was found to be correlated with bitterness (r²_multiple = 0·67 and 0·93, respectively) as assessed by an analytical panel. The results of the taste trials show that both bitterness and taste preference for sprouts are correlated with the content of sinigrin and progoitrin. Taste preference for sprouts is only correlated with sinigrin and progoitrin when their combined content exceeds 2·2 g kg⁻¹, while bitterness is correlated with both glucosinolates for the whole studied content range. © 1998 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.     

Quantification of chicory root bitterness by an ELISA for 11β,13-dihydrolactucin

Chicory root (Cichorium intybus L. var. sativum) is an important foodstuff appreciated for its bitter taste, which is caused by sesquiterpene lactones. These compounds represent a quality parameter for monitoring the raw material. Using polyclonal antibodies, an enzyme-linked immunosorbent assay (ELISA) was developed to quantify the bitter compound 11β,13-dihydrolactucin in chicory root. Assay linearity ranged from 4.6 to 300 ng/ml, with intra- and inter-assay variations of 4.9% and 7.2%, respectively. An IC₅₀ of 2 ng/ml and a detection limit of 0.16 ng/ml were obtained. No or little cross-reactions with other sesquiterpene lactones occurred. Roots of three different chicory varieties were evaluated for their bitter taste and were investigated by the ELISA. Distinct concentrations of 11β,13-dihydrolactucin ranging from 485 to 1720 mg/kg dry matter were correlated with the bitterness degree (r = 0.9). The ELISA appeared sensitive, selective, accurate and may serve as screening tool in breeding of chicory roots for bitterness.     

Phenolic composition of European cranberrybush (Viburnum opulus L.) berries and astringency removal of its commercial juice

Phenolic composition of the European cranberrybush (ECB) (Viburnum opulus L.) juice was determined using high‐performance liquid chromatography. The juice contained 2037 mg kg^?1 chlorogenic acid, which was 54% of total phenolics, and several other phenolics such as (+)‐catechin, (?)‐epicatechin, cyanidin‐3‐glucoside, cyanidin‐3‐rutinoside and six different glucosides of quercetin. Because of its strong astringent taste, the juices were treated with various doses of two different types of activated carbons (Granucol Bi and Granucol Ge) in order to remove phenolic compounds. Results revealed that both types of activated carbons were equally effective on astringency removal (P < 0.01). A 20–30% reduction in total phenolics was achieved by application of 2.0–3.0 g L^?1 activated carbon which also removed unpleasant taste and odour.     

Limonoid content of sour orange varieties

BACKGROUND: Modern Citrus cultivars are thought to have arisen from three parents: the pummelo, the mandarin, and citron. Taxological and genetic data support that sweet and sour oranges share a common parentage. However, as their name suggests, the organoleptic properties of the fruit from these two families is distinctly different. Analysis of the limonoid content of sour orange varieties has been limited. RESULTS: Juice samples prepared from a selection of sour orange cultivars were evaluated for their limonoid A‐ring lactone, aglycone, and glucoside contents. Limonoate A‐ring lactone concentrations ranged from 11.1 to 44. 9 mg L^?1, whereas nomilinoate A‐ring lactone levels were found not to exceed 1.2 mg L^?1. Total limonoid aglycone and total limonoid glucoside concentrations varied from 2.4 to 18.4 mg L^?1 and from 149.0 to 612.3 mg L^?1, respectively. Limonoid glucoside profiling by liquid chromatography–mass spectrometry suggest that the sour oranges are distinctly different from sweet oranges and other citrus species. CONCLUSION: Limonoid aglycone and A‐ring contents across sweet and sour oranges are similar, whereas limonoid glucoside profiles are distinctly different. Juice prepared from Citrus maderaspatana had the highest limonoid concentrations among the samples tested and could potentially be used for the isolation of limonoid A‐ring lactones and glucosides. Published 2011 by John Wiley & Sons, Ltd.     

Modification of perceived beer bitterness intensity,character and temporal profile by hop aroma extract

The effect of hop aroma on perceived bitterness intensity, character and temporal profile of beer was investigated. A hop aroma extract was added at 3 levels (0, 245, 490 mg/L) to beers at low, medium and high bitterness. Beers were evaluated for perceived bitterness intensity, harshness, roundedness and linger by a trained panel using a rank-rating technique at each bitterness level, with and without nose clips. The use of nose clips enabled the olfactory aspect to be decoupled from taste and mouthfeel aspects of bitterness perception. Results showed significant modification of perceived bitterness in beer by hop aroma depending on the inherent level of bitterness. These modifications were mainly driven by olfaction – in an example of taste-aroma interactions, as well as certain tactile sensations elicited by the hop aroma extract in the oral cavity. At low bitterness, beers with hop aroma added were perceived as more bitter, and of ‘rounded’ bitterness character relative to those without hop aroma. When judges used nose clips, this effect was completely eliminated but the sample was perceived to have a ‘harsh’ bitterness character. Conversely, at high bitterness, even when nose clips were used, judges still perceived beers containing hop aroma to be more bitter. These increases in bitterness perception with nose clips indicates the stimulating of other receptors, e.g. trigeminal receptors by hop aroma extract, which in tandem with the high bitterness, cause perceptual interactions enhancing bitterness intensity and also affecting bitterness character. Bitterness character attributes such as ‘round’ and ‘harsh’ were found to significantly depend on bitterness and aroma levels, with the second level of aroma addition (245 mg/L) giving a ‘rounded’ bitterness in low bitterness beers but ‘harsh’ bitterness in high bitterness beers. The impact of aroma on temporal bitterness was also confirmed with time-intensity measurements, and found to be mostly significant at the highest level of hop aroma addition (490 mg/L) in low bitterness beers. These findings represent a significant step forward in terms of understanding bitterness flavour perception and the wider impact of hop compounds on sensory perception.     

Bitterness and Astringency of Sinapine and Its Components

Sinapine, choline chloride, and sinapic acid were evaluated for bitterness and astringency, at suprathreshold concentrations in water, by a trained sensory panel using magnitude estimation. Power functions (S = kCⁿ) were established for the bitterness of each of the three chemicals and the reference caffeine; none of the exponents for bitterness was significantly different from caffeine (n = 0.98) suggesting that, for any of these taste precursors, a doubling of concentration would double the bitterness perceived. Equimolar solutions of caffeine and sinapine were considered similar in intensity and significantly more bitter than choline chloride; sinapic acid was intermediate in bitterness. The sum of the bitterness values calculated from the power functions for choline chloride and sinapic acid accounted for approximately 80% of the bitterness of sinapine, at equimolar concentrations. Fifty to 94% of the bitterness perceived from tasting water slurries of rapeseed flour and protein concentrate was explained by the bitterness expected from their content of sinapine and free choline. Reliable power functions could not be established for the astringency of sinapine, choline chloride, and sinapic acid at the concentrations used. However, a clear psychophysical function was established for the astringency of the reference alum.     

The determination of bitter principles in zucchinis

A method using reverse phase thin layer and high performance liquid chromatography was developed to determine the level of the bitter principle occasionally found in zucchini (Cucurbita pepo L.). The system gave excellent separation with recovery rates of about 90% from spiked fruit. The bitter principle was confirmed by C¹³ NMR and mass spectrometry as cucurbitacin E glycoside which was present in concentrations in the order of 600mg kg^?1 in bitter fruits. Bitterness was detected by a taste panel at cucurbitacin E glycoside concentrations of 1 mg kg^?1 in aqueous solutions and 2 mg kg^?1 in zucchini pulp. The method described should assist the screening for bitterness in commercial and breeding populations of zucchini.     

Microwave–hot air drying applied to selected cassava cultivars: drying kinetics and sensory acceptance

The effects of three cassava cultivars produced in Brazil were assessed (IAC Espeto, IAC 14 and IAC Caapora) in order to obtain chips by precooking and hot air–microwave drying (70 °C, 95 W). The difference in the composition of cultivars has not influenced the drying of cassava slices. The drying kinetics presented a constant drying rate period followed by a decreasing drying rate with effective diffusion coefficient of 2.8–3.0 × 10^?10 m²s^?1. The hedonic means of all attributes ranged from ‘neither like nor dislike’ to ‘like moderately’. Therefore, the choice of the more suitable cultivar can be based on plant productivity and product yield. The IAC 14 cultivar resulted in the highest root production per plant, product mass per roots and chips yield.     

What are domestic apples worth? Hedonic responses and sensory information as drivers of willingness to pay

The effects of written information of key sensory characteristics of apple cultivars on hedonic ratings and willingness to pay (WTP) were measured in an experimental auction. Participants (n = 118, 95F, 23M, mean age 37 y.) rated, in three subsequent rounds, pleasantness and WTP based on (1) appearance only (n = 25), (2) appearance, written information and tasting (n = 44), or (3) appearance, tasting and written information (n = 49). Four domestic cultivars were described as medium sour and crispy (‘Amorosa’), sour and medium crispy (‘Konsta’), medium sweet and medium crispy (‘Lobo’) and sweet and medium crispy (‘Tobias’). The differences between the cultivars in pleasantness and WTP were minimal when the evaluation was based on appearance only. The effect of tasting after visual inspection was positive in three cultivars and negative in one (‘Konsta’). Written information after tasting did not affect pleasantness or WTP. For one cultivar (‘Tobias’), information given before tasting created expectations that were not fulfilled, thus tasting decreased hedonic ratings and WTP. Mean WTP was 2.36 euro/kg. When pleasantness increased by one point, WTP increased by 0.31–0.45 euro/kg. Regression models showed that pleasantness explained 38–55% of WTP. Respondents who reported consuming domestic apples more often than once a week had 0.52–0.74 euro/kg higher WTP than those who consumed them less frequently, suggesting that familiarity with the product increases WTP. Results indicate that both written information and tasting contribute to the ratings of pleasantness and WTP.