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Proximate composition (moisture, protein, starch, amylose, total dietary fibre, Brix degree, fat, ash, ascorbic acid, phenolic compounds, acidity and pH), minerals (Na, K, Ca, Mg) and trace elements (Fe, Cu, Mn, Zn) were determined in 30 cultivars of sweet potato from the Canary Islands (Spain). There were significant differences between the sweet potato cultivars for all the parameters studied; in addition, both the island of production and the cultivation cycle showed a noteworthy influence on the mineral and trace element composition of the tubers. It is worth mentioning that the consumption of sweet potatoes contributes relatively high intake levels of vitamin C, phenolic compounds and mineral and trace elements (K, Mg, Ca, Mn, Fe and Cu). Application of multidimensional scaling (MDS) correctly classified the sweet potato cultivars according to the island of production and maturation cycle.

A hundred and thirty-six single-cultivar red wines of different vintages were collected from several wineries in the Canary Islands in order to study the magnitude of the copigmentation phenomenon and the antioxidant activity. The contribution of free anthocyanins, copigmented anthocyanins and polymeric pigments to the colour of wine, as well as the total phenols, the antioxidant activity (2,2-diphenyl-1-picrylhydrazyl, DPPH method) and the chromatic characteristics of the wines were determined. The influence of ageing time and the climatic conditions on these parameters was also studied. The wines made with Merlot, Ruby Cabernet and Syrah cultivars showed the highest parameters of colour, and the largest contribution to the copigmented anthocyanins was from the Ruby Cabernet, Listan negro and Syrah cultivars. The copigmented anthocyanins and the free anthocyanins decrease with the age of the wine, and the antioxidant activity of the samples appears to be related to the total phenol content. An influence of the climatic conditions on colour parameters has been found. The correlation study between parameters suggests that the parameters b* and L* could be used as suitable indicators of evolution or oxidation stage of red wines.

Tomatoes have been described as a functional food because of their particular composition of different bioactive compounds. In this study, the proximate composition, minerals and trace elements, and antioxidant compounds were determined in two tomato cultivars (Mariana and Dunkan) that were grown in Gran Canaria (Spain) either conventionally or hydroponically. Although compositional data of this type require being subjected to the specific statistical techniques of compositional analysis, this approach has not usually been considered in this context. In the present case, a compositional Mann–Whitney U test of the data showed significant differences for each factor (cultivar and cultivation system) in several of the compositional variables studied. For the differences between cultivars, these parameters were the protein, Mg, lycopene, ascorbic acid, citric acid, and fumaric acid contents. For the differences between cultivation systems, they were mainly those of the mineral and trace elements group. Although one-year data are insufficient to make clear relationship among compounds because more repetitions in several localities and years are necessary, the compositional HJ-biplot (in which the links provide estimates of the linear relationship among variables) results agreed with other scientific results about linear relationship among some compounds analyzed.

Moisture, starch, amylose, fibre, proteins, ascorbic acid, total phenol compounds, acidity, pH, ash and mineral and trace elements were determined in 10 potato cultivars from Canary Islands experimentally cultivated. Six of the cultivars were also cultivated in two locations, to ascertain the impact of different soil types on the parameters measured. There were differences between cultivars in both, physicochemical parameters and mineral and trace elements analysed. There were significant differences in the mean values obtained for all the parameters considered, except for ascorbic acid, between both locations. Application of linear discriminant analysis allowed to classify the potato samples according to the cultivar, and according to growing location.

Summary Organic acids, pH and total acidity were determined in the grains of nineteen wheat cultivars. Six organic acids, such as glutamic, oxalic, malic, tartaric, shikimic and fumaric acids, were separated and identified in all wheat samples applying HPLC coupled to diode array detector. Glutamic acid was the major organic acid followed by tartaric and malic acids. A low oxalic acid/calcium ratio was observed in the wheat samples analysed. The wheat samples belonging to Triticum turgidum had a higher (P

Phosphorous, Na, K, Ca, Mg, Fe, Cu, Zn, Mn and Se were determined in eighteen wheat landraces from Canary Islands and a commercial cultivar. The mean values obtained were: P (2370 ± 333 mg/kg); Na (102 ± 52 mg/kg); K (4363 ± 386 mg/kg); Ca (351 ± 62 mg/kg); Mg (1163 ± 155 mg/kg); Fe (40.0 ± 5.5 mg/kg); Cu (2.68 ± 0.93 mg/kg); Zn (32.1 ± 2.9 mg/kg); Mn (22.1 ± 3.5 mg/kg); Se (67.7 ± 40.4 μg/kg). There were differences ( P Triticum aestivum species had higher mean P, Mg, Fe, Cu, Zn and Mn concentrations, and a lower mean Se concentration, than Triticum turgidum species. The environment and agronomic practices could affect the genetic information of the seeds determining changes in the mineral and trace element composition. The wheat represents an excellent source of Mn (over 100% of recommended dietary intake, RDI), as well as P, Mg, Fe, Cu, Zn and Se (20–50% of RDI). Many correlations were found between the parameters analyzed emphasizing the Cu–Mg ( r = 0.691) and Cu–Mn ( r = 0.619) correlations. Linear discriminant analysis allowed a good differentiation of the wheat samples according to the cultivar (89.7% of wheat samples classified correctly).

Eight cultivars of different colored onions (white, golden, and red) were evaluated for fresh bulbs cultivated and grown under the same environmental and agronomical conditions. Cluster analysis and principal component analysis, based on different flavonoids, total phenols, and pungency, data showed that the onions were not clustered according to variety (genetic similarity degree), whereas the color was the variable with the highest influence, ranging between 50 and 70%. Artificial neural networks were applied to study the possibility of discriminating among onion varieties. Characterization of the onion according to variety and procedence of the seeds was around 95-100%. Samples belonging to the Carrizal Alto procedence had an incorrect classification for 25% of the data.

The following organic acids (glutamic, oxalic, pyruvic, malic, tartaric, citric, and fumaric), pungency, Brix degree, acidity, and pH were determined in onion cultivars (Texas, Guayonje, San Juan de la Rambla, Carrizal Alto, Carrizal Bajo, and Masca) harvested in the same agroclimatic conditions. Glutamic acid was the most abundant organic acid (325 +/- 133 mg/100 g) followed by citric acid (48.5 +/- 24.1 mg/100 g) and malic acid (43.6 +/- 10.4 mg/100 g). There were significant differences between the onion cultivars in the mean concentrations of all of the analyzed parameters. The San Juan de la Rambla and Masca cultivars presented, in general, higher concentrations of the organic acids than the other cultivars. Significant differences in most of the analyzed parameters were observed between the two seed origins for the Masca and San Juan de la Rambla cultivars. The onion samples tended to be classified according to the cultivar and, in the case of San Juan de la Rambla cultivar, according to the precedence of the seeds after applying discriminant analysis.

Chestnuts like other foodstuffs may be characterized by their chemical composition. The chemical composition of ascorbic acid, total acidity, pH, starch, refraction index (°Brix), moisture, ashes, insoluble fibre, soluble fibre, total dietary fibre, total proteins, cations (Na, K, Ca, Fe, Cu, Zn, Mn, Mg) and phosphorous was determined in 19 local chestnut varieties from three areas of production in the island of Tenerife. Significant differences were found between the mean values of moisture, starch, total phenols contents, total soluble and non-soluble fibre, Ca, Cu, K, Mg and Zn, obtained according to the area of production. Distribution patterns of the samples were established for correlating the chemical composition of the chestnuts and varieties, using different chemometrics tools such as cluster analysis, principal component analysis, factor analysis and linear discriminant analysis (LDA). Initially, cluster analysis made it possible to establish a primary relationship between the variables. When applying stepwise LDA the chestnut samples were well classified within their area of production. Also, when the stepwise LDA was used on the chestnut samples from area of production 2, 100% of the chestnut samples were also correctly classified within their variety.

BACKGROUND: P, Na, K, Ca, Mg, Fe, Cu, Zn, Mn and Se were determined in five traditional onion cultivars (Allium cepa L.) from Tenerife (Guayonje, San Juan de la Rambla, Carrizal Alto, Carrizal Bajo and Masca) and a commercial cultivar (Texas Early Grano 502) grown under the same agronomic, soil and climatic conditions in order to find out differences between these cultivars. RESULTS: Carrizal Alto presented the highest K content and lowest P, Na, Fe, Zn, Mn and Se. Texas cultivar had the highest P, Mg and Se contents, and the lowest contents of Ca, Cu and Mn. There were clear differences in the mineral and trace elements contents between the two seed origins of San Juan de la Rambla cultivar. Many correlations were found between the parameters analyzed, emphasizing the FeZn and CaMn correlations. CONCLUSION: There were differences in the mineral and trace element composition between the onion cultivars. The environment and agronomic practices could affect the genetic information of the seeds, determining changes in the mineral and trace element composition. Linear discriminant analysis is a useful tool for differentiating onion samples according to cultivar and seed origin. Copyright © 2008 Society of Chemical Industry

The determination of organic acids in tomato samples was optimized using the HPLC method with on-line photodiode array detection, previous to extraction with 80% ethanol at room temperature and clean-up in Accell Plus QMA cartridge. The organic acids (oxalic, pyruvic, malic, citric, fumaric and ascorbic), Brix degree, acidity and pH were determined in five tomato cultivars (Dorothy, Boludo, Dominique, Thomas and Dunkan) harvested in Tenerife. There are several significant differences among cultivars in the concentration of many acids. The cultivation method, sampling period and the region of production were also considered. Citric, malic and oxalic acids were the major organic acids in all the cultivars. Some significant differences in the studied parameters were observed between the cultivars. The cultivation method and sampling period influenced in a variable way the studied parameters, depending on the tomato cultivar. The production region influenced the ascorbic acid concentration of the tomatoes. Applying stepwise discriminant analysis, it was found that the sampling period is more important in the differentiation of the tomato samples than the cultivar, cultivation method and production region.

Concentrations of Na, K, Rb, Ca, Mg, Fe, Cu, Zn and Mn were determined in eight cultivars of potatoes harvested in Tenerife. The traditional cultivars presented higher K, Fe, Cu and Zn concentrations and lower ratio Na/K than recently imported cultivars. The cultivar Cara showed the highest and lowest mean concentration for Na and K, respectively. The highest mean concentrations of Fe, Cu and Zn were found in the cultivars Azucena, Palmera and Peluca, and the lowest concentrations in Cara. The trace elements significantly correlated with all the metals. The behaviour of Na was opposite to the rest of the metals, showing negative correlations. Applying factor analysis, the first three factors explaining 70.4% of the total variance were extracted. The first factor is related to Zn, the second factor is associated with Mn and K, and the third factor is negatively related to Na. Factor analysis and cluster analysis tend to separate the potato samples according to location and irrigation procedure. Traditional and recently imported potatoes were well separated when the factor analysis was applied on the samples of Solanum tuberosum.

Determination of free gallic acid and catechin (cianidanol) in banana samples was optimized using a high-performance liquid chromatographic (HPLC) method with on-line photodiode array detection. This method was applied for cultivars of bananas (Gran Enana and Pequena Enana) harvested in Tenerife (Canary Islands) and for bananas (Gran Enana) from Ecuador. The contents of catechin and gallic acid in bananas from Ecuador were higher (P

The evolution of moisture, starch, amylose, ash, fructose, sucrose, glucose and ascorbic acid was studied in five cultivars of Tenerife potatoes in order to evaluate their variation during storage at 12 °C and 90% humidity. Differences in behaviour were detected among cultivars in relation to the period of storage under these conditions. The Negra cultivar presented the worst behaviour in storage, while the Bonita and Colorada cultivars presented the best. The moisture remained constant for the first 6 weeks; afterwards; a significant decrease was observed. A progressive decrease of starch (dry basis) over the time of storage was detected, while an increase of reducing sugars occurred. The amylose/amylopectin ratio increased during the first 6 weeks of storage. The concentration of vitamin C decreased markedly during the storage, and, after the 20th week, the content had decreased by more than 50%.

The contents of moisture, protein, ash, ascorbic acid, glucose, fructose, total sugars, and total and insoluble fiber were determined in cultivars of bananas (Gran Enana and Pequeña Enana) harvested in Tenerife and in bananas (Gran Enana) from Ecuador. The chemical compositions in the bananas from Tenerife and from Ecuador were clearly different. The cultivar did not influence the chemical composition, except for insoluble fiber content. Variations of the chemical composition were observed in the bananas from Tenerife according to cultivation method (greenhouse and outdoors), farming style (conventional and organic), and region of production (north and south). A highly significant (r = 0.995) correlation between glucose and fructose was observed. Correlations of ash and protein contents tend to separate the banana samples according to origin. A higher content of protein, ash, and ascorbic acid was observed as the length of the banana decreased. Applying factor analysis, the bananas from Ecuador were well separated from the bananas produced in Tenerife. An almost total differentiation (91.7%) between bananas from Tenerife and bananas from Ecuador was obtained by selecting protein, ash, and ascorbic acid content and applying stepwise discriminant analysis. By selecting the bananas Pequeña Enana and using discriminant analysis, a clear separation of the samples according to the region of production and farming style was observed.

Determination of free phenolic compounds in potato samples was optimized using a high-performance liquid chromatographic (HPLC) method with on-line diode array detection. This method was applied to samples of four cultivars of potatoes harvested in Tenerife (Canary Islands). The free phenolic compounds found in the potato samples were (+)-catechin, chlorogenic acid, caffeic acid, p-coumaric acid, and ferulic acid. Potato samples belonging to Colorada cultivar, ssp. andigena, had mean concentrations of total phenolic compounds and chlorogenic acid higher than those found for Kerr's Pink and Cara cultivars, ssp. tuberosum, and for Negra cultivar, S. x chaucha. In contrast, p-coumaric acid was not detected in any potato samples of the Colorada cultivar. Traditional potatoes presented a higher mean concentration of ferulic acid than recently imported potatoes. A significant and negative correlation was established between (+)-catechin and p-coumaric acid. A considerable contribution to the daily intake of flavonoids was observed with the actual consumption of potatoes.