Bitter taste in cassava roots correlates with cyanogenic glucoside levels

Cassava roots contain cyanogenic glucosides. Malawian farmers classify cultivars into two groups based on the perceived danger of eating raw roots that they associate with bitterness. In the vernacular, cultivars that produce roots with bitter taste are called vyakubaba (bitter), whereas those yielding non‐bitter roots are called vyakuzizra (cool). In the scientific literature they are distinguished as ‘bitter’ or ‘sweet’. Roots from ‘bitter’ cultivars are processed prior to consumption. We studied the ability of farmers to predict the cyanogenic glucoside levels of 492 roots from the 10 most commonly grown cultivars. Twenty‐eight farmers predicted the taste of each of the cultivars that they grew, and scored bitterness on a five‐point scale by tasting the root tip. Thereafter cyanogenic glucosides were determined on half of the root, while a taste panel scored the taste of the other half. The mean cyanogenic glucoside level in 132 roots from ‘cool’ cultivars was 29 mg HCN eq kg^?1 fresh weight (CI 25–33, range 1–123) and in 360 roots from ‘bitter’ cultivars was 153 mg HCN eq kg^?1 fresh weight (CI 143–163, range 22–661). Farmers' distinction of ‘cool’ and ‘bitter’ cultivars predicts glucoside levels. The tasting of the tip of the root improved the farmers' prediction of toxicity. Scoring of bitterness by a trained taste panel showed a stronger correlation with glucoside levels (r² = 0.67). This suggests that cyanogenic glucosides confer the bitter taste, notwithstanding the probability of additional modifying intrinsic factors. Copyright © 2004 Society of Chemical Industry     

内蒙古不同种源山杏杏仁中苦杏仁苷含量差异分析

采用高效液相色谱法(HPLC),对内蒙古7个种源山杏杏仁中苦杏仁苷的含量进行差异性分析。结果表明:不同种源山杏杏仁中苦杏仁苷的含量存在显著差异(p<0.05);7个种源苦杏仁苷平均含量为5.43%,平均含量范围为4.34%~6.25%;平均变异系数为0.07,扎鲁特旗种源的变异系数较其它种源大;苦杏仁苷含量与经纬度呈极显著负相关,相关系数分别为0.806、0.722,与海拔呈极显著正相关(0.896);聚类分析将7个种源划分为2类。该研究结果为内蒙古地区山杏的深加工以及利用提供理论依据。      

Occurrence of sapogenins in leaves and seeds of quinoa (Chenopodium quinoa Willd)

Seeds of the Andean seed crop quinoa usually contain saponins in the seed coat. Saponins give a bitter taste sensation and are a serious antinutritional factor. Therefore selection of sweet genotypes with a very low saponin content in the seeds is a main breeding goal. However, selection for sweet genotypes is retarded by cross‐pollination. Early identification of sweet and bitter quinoa genotypes before anthesis would speed up breeding considerably. The ability to distinguish sweet and bitter genotypes was investigated in a glasshouse and in a field experiment. In the glasshouse experiment the content of sapogenins was determined in leaves of sweet and bitter quinoa genotypes at successive stages of plant development and finally in the seeds. Detectable amounts of sapogenins were found earliest 82 days after sowing in leaves of both sweet and bitter quinoa genotypes. The total sapogenin content in leaves of sweet and bitter genotypes increased during plant development but remained lower than the content found in the seeds. The sapogenin content in seeds of sweet genotypes varied from 0.2 to 0.4 g kg⁻¹ dry matter and in seeds of bitter genotypes from 4.7 to 11.3 g kg⁻¹ dry matter. The difference in sapogenin content between leaves and seeds was much higher in bitter genotypes than in sweet genotypes. Hederagenin was the major sapogenin found in leaves, and oleanolic acid in seeds. In the field experiment it was found that the content of sapogenins in the leaves of F2 plants of crosses between both quinoa types did not differ between sweet and bitter genotypes. The obtained results demonstrated that sweet genotypes could not be selected before anthesis on the basis of the sapogenin content in the leaves. © 2000 Society of Chemical Industry     

响应面试验优化苦杏仁粕中苦杏仁苷提取工艺及其高效离心分配色谱纯化

为实现苦杏仁资源的高效利用,以带皮生杏仁为原料,首先研究热烫去皮对苦杏仁苷含量的影响,然后采用响应面试验优化了超声辅助提取压榨脱脂苦杏仁粕中苦杏仁苷的工艺条件,应用高效离心分配色谱分离制备高纯度苦杏仁苷。结果表明：按料液比1∶5（g/mL）加入沸水,煮沸10 min,能够较好地达到灭酶保苷的目的,苦杏仁苷含量为（4.72±0.14）%;压榨脱脂苦杏仁粕中苦杏仁苷最佳提取工艺条件为73%乙醇溶液、液料比8∶1、超声温度70 ℃、提取时间20 min、提取2 次,苦杏仁苷的提取率达8.03%;高效离心分配色谱纯化苦杏仁苷的最佳条件为以正丁醇-乙酸乙酯-甲醇-水（2.5∶0.625∶0.5∶4,V/V）为溶剂体系,上相为固定相,下相为流动相,转速900 r/min,流速2.0 mL/min,分离纯化得纯度为96.14%的苦杏仁苷。     

Composition of Atriplex hortensis, Sweet and Bitter Chenopodium quinoa Seeds

Composition and amino acid profiles of seeds from garden orach (A triplex hortensis) and sweet quinoa (Chenopodium quinoa Willd. ‘Surumi’) were compared with bitter quinoa (Chenopodium quinoa Willd.). Protein content was 14.8 and 15.7% for sweet and bitter quinoa, respectively. Garden orach seeds had a protein content of 25.7%, similar to that found in legumes. Fat and ash contents were similar for all three samples (5.3 to 6.2% fat; 2.6 to 3.2% ash). Amino acid profiles showed a balanced content of essential amino acids for all three samples when compared with reference patterns from the World Health Organization. Garden orach and quinoa seed proteins contained higher lysine contents compared with cereals.     

Physicochemical and descriptive sensory characterization of Spanish pomegranates: aptitudes for processing and fresh consumption

Pomegranate fruit and its products are being widely promoted to consumers as healthy alternatives for their daily diet. The aim was to study the main sensory differences among twenty pomegranate cultivars, determining which cultivars have particular flavour or texture notes that could make them more appropriate for fresh consumption or processing. Four clusters grouped all samples, two of them included sour cultivars and two of them included sweet and sweet‐sour cultivars. Cluster 1 (sour) was characterized by having floral, apple, and grape flavour notes and also producing a tongue numbing sensation. Cluster 2 (sour), which included the Wonderful cultivar, had samples with wine‐like attributes. Clusters 3 and 4 (sweet and sour‐sweet) were characterized by having overall sweet, pear and grape notes for cluster 3, and beet, fruity‐dark, fermented, musty and woody flavour for cluster 4.     

Effects of Seasonal Variation on Sensory Properties and Total Phenolic Content of 5 Lettuce Cultivars

ABSTRACT: Butterhead, crisphead, green leaf, red leaf, and romaine types of lettuce (Lactuca sativa L.) are all commonly available in U.S. markets. Sensory properties of lettuce may vary in response to environmental factors that often fluctuate widely throughout the growing season. Bitterness is generally thought to increase in lettuce grown at higher temperatures and may be related to phenolic content. This study evaluated sensory properties and total phenolic content of 5 lettuce cultivars harvested early, midway, and late in the growing season and investigated possible correlations with environmental temperature and light intensity indexes. Thirty panelists rated bitterness, appearance, flavor, texture, and overall acceptability of “Crisp and Green” (green leaf), “Crispino” (crisphead), “Green Forest” (romaine), “Lochness” (butterhead), and “Vulcan” (red leaf) lettuce. There was considerable variation in sensory ratings among the 5 cultivars (P < 0.005) but few differences within cultivars across the growing season. The crisphead cultivar, Crispino, received higher scores (P < 0.01) for flavor, texture, and overall acceptability and was rated less bitter (P < 0.05) than other cultivars. Total phenolic content varied significantly (P < 0.001) among cultivars with the red leaf cultivar, Vulcan, exhibiting the highest levels. There was no correlation between bitterness and total phenolic content or environmental factors. Differences among lettuce cultivars appear to have a larger impact on sensory and phenolic profiles than environmental variation during the growing season.     

Effects of phenolics in sorghum grain on its bitterness,astringency and other sensory properties

Despite the fact that condensed tannins are potentially important antioxidants, there is a general belief that tannins in sorghum confer objectionable sensory attributes. The objective of this study was to determine differences in the sensory attributes of sorghums containing different levels of total phenolic compounds. A trained sensory panel described and quantified the sensory attributes of different sorghums (condensed‐tannin containing and tannin‐free). All the sorghum cultivars were perceived as bitter and astringent. Bran infusions of tannin sorghums were perceived as darker, clearer, more bitter and more astringent than those of the tannin‐free sorghums, while those of tannin‐free sorghums were perceived as sweeter and cloudy. Sorghum whole‐grain rice from the tannin sorghums which had relatively soft endosperm texture (PAN 3860 and Ex Nola 97 GH) was perceived as dark, hard, chewy, bitter and astringent, while that from tannin‐free sorghums having relatively hard endosperm texture (Segaolane and Phofu) was perceived as soft, sweet and had a maize‐flavour. Surprisingly, the bitterness and astringency, as well as other sensory attributes of NS 5511 (tannin sorghum), were perceived as similar to PAN 8564 (tannin‐free sorghum) even though NS 5511 had more than twice the total phenol content of PAN 8564. This suggests not all condensed‐tannin containing sorghums have objectionable sensory attributes. Copyright © 2007 Society of Chemical Industry     

Original article: In vitro starch digestion and potassium release in sweet potato from Papua New Guinea†

Twenty samples of sweet potato from Papua New Guinea, made up of cultivars 3‐mun, Carot kaukau, Wahgi besta, Nillgai, Baiyer kaukau, and 1‐mun from three provinces, three farmers, and three locations, were subjected to an in vitro starch digestion procedure. Digestion of starch was studied by glucometry, while potassium release was monitored using electrochemistry. The potassium content of the nondigested samples ranged from 4 to 17 mg g^?1 dry solids, while the starch content was from 47 to 80 g per 100 g dry solids and independent of G × E effects. In vitro starch digestibility (2–75 g digested starch per 100 g dry starch) significantly (P < 0.05) varied with time in a nonlinear manner with biphasic digestograms. Potassium release was independent of time in in vitro gastric and pancreatic regions, but more potassium was released during pancreatic than gastric digestion. Results suggest differences in resistant starch and bioavailability of (micro)nutrients that could influence utilisation of sweet potato.     

Total lipid content and fatty acid composition of oilseed from lesser known sweet pomegranate clones

The oil content and fatty acid composition of the oilseed of seven lesser known Spanish sweet pomegranate (Punica granatum L) clones were determined by gas chromatography. The seeds contained oil in the range of about 63–122 g kg⁻¹ dry matter, a notably lower content than that of some oriental pomegranate cultivars. Levels of lipid content probably could be considered insufficient for economic industrial exploitation compared with those of conventional oilseeds. The predominant fatty acid was the polyunsaturate (n − 3) linolenic acid (43.4–88.2%), followed by the diunsaturate linoleic (5.3–16.5%), the monounsaturate oleic (3.7–20.3%) and palmitoleic (traces to 2.9%) acids. To a lesser extent the saturates palmitic (2.6–14.9%) and stearic (1.2–9.0%) acids were also found in all clones. Lauric and arachidic acids were rarely detected. We have not confirmed the presence of behenic (C22:0) and lignoceric (C24:0) acids previously reported in edible and non‐edible pomegranate cultivars. Intervarietal differences in fatty acid composition were shown and they could be useful to establish chemotaxonomic differences. In contrast with previous reports on sweet pomegranate cultivars, a very low (0.04–0.35) saturated/unsaturated fatty acid ratio was found. © 2000 Society of Chemical Industry     

Phenolic compounds in virgin olive oils: influence of the degree of olive ripeness on organoleptic characteristics and shelf-life

 An experimental investigation was performed on virgin olive oils from Coratina and Ogliarola salentina cultivars extracted from green, partially blackened and totally blackened olives in order to evaluate changes in the organoleptic properties and in the shelf-life of the oil. The aim of the investigation was to identify the optimal stage of olive maturation for each cultivar to produce higher quality oils. Routine analyses in accordance with EC regulation no. 2568/91, the determination of phenols by HPLC and induction times were carried out. On the whole, the simple phenolic compounds increased as darker olives were used whereas the hydrolysable phenolic compounds decreased. In both the cultivars, total phenols and induction times were significantly higher in the oils obtained from green olives than in oils from totally blackened olives. Hence, it seems advisable to delay olive harvesting for cultivars usually yielding bitter to pungent oils (e.g. Coratina), but to anticipate harvesting for olives producing sweet tasting oils (e.g. O. Salentina). This would produce less bitter Coratina oils, with organoleptic features which may better fulfil consumers' expectations, and O. Salentina oils more resistant to oxidation. Received: 5 June 2000     

Inhibitory effect of bitter principle of palmyrah (Borassus flabellifer L) fruit pulp on the growth of mice: evidence using bitter and non‐bitter fruit pulp

Different cultivars of palmyrah produce mature fruits of differently flavoured palmyrah fruit pulp (PFP). A natural ‘sweet’ (non‐bitter) variety exists. Bitter and naturally non‐bitter palmyrah fruit pulps showed little difference in total sugars (471 and 543 g kg⁻¹ respectively), estimated by the Nelson method after invertase action, and had total crude flabelliferin contents of 1480 and 1650 mg kg⁻¹ respectively. The flabelliferin profiles on silica gel G60 TLC plates developed using butanol; ethanol; NH₃ (7:2:5) differed. Bitter fruit pulp (from Jaffna) contained the bitter flabelliferin F‐II as the major component (about 900 mg per kg), while the non‐bitter fruit pulp (from Ampara) did not contain F‐II but contained the anti‐microbial flabelliferin, F_B. Incorporation of non‐bitter PFP at the 100 g kg⁻¹ level into WHO standard mice‐breeding feed resulted in significantly increased (p = 0.00008) weight gain by ICR mice compared with bitter PFP incorporation at the same level in the feed. Weight gain was also significantly higher (p = 0.021) than in the control (WHO standard mice‐breeding feed). The study supports the conclusion that the bitter principle, F‐II is responsible for reduced weight gain in mice. © 2000 Society of Chemical Industry     

Effects of processing of grated cassava roots by the 'screw press' and by traditional fermentation methods on the cyanide content of gari

The extent of the loss of hydrocyanic acid (HCN) from grated cassava roots, selected from both the sweet and bitter varieties, was compared in the roasted grit (gari) derived from their fresh pulp which had been dewatered and fermented by two different processes; the quick (1-day) 'screw press' method (QSP) and the slow (3-day) traditional one (STD), respectively. The relative amounts of HCN which had disappeared after 1 day, in the case of QSP, and 3 days, in respect of STD, were comparable (92–100%) for either free (non-glycosidic) or bound (glycosidic) cyanide content of the two cultivars, indicating that the former method was more efficient than the latter in the detoxification of the grated pulp. The QSP method appeared to retain some of the bound cyanide while with the STD method, virtually no bound cyanide was detectable. About 83–91% of the total HCN content of the grated roots was present as free cyanide. It would seem that varietal differences in HCN contents of cassava may not be a critical factor in the preferential selection of the roots for 'garification'.     

Taste properties of cocoa drinks with an added bitter/sweet sugar: intensity/time effects

Cocoa drinks treated with either sucrose or the bitter/sweet sugar, methyl α-D-mannopyranoside were evaluated for their intensity/time response determined by taste panellists using a moving chart recorder. Both additives caused an increase in persistence as well as intensity of response, sucrose for sweetness and methyl α-D-mannopyranoside for bitterness.
Tasting of the sucrose-treated drinks, after presaturating panellists' tongues with quinine sulphate solutions, caused no significant differences in perceived sweetness. However, presaturating panellists' tongues with sucrose solution did cause significant differences in bitterness perception of the drinks containing methyl α-D-mannopyranoside.
These results accord with a previous observation of the taste response to methyl α-D-mannopyranoside in pure water and suggest that the bitter/sweet molecule may exert its effect by simultaneously spanning both basic taste receptors.