Elena M. Rodríguez

Aloe vera as a functional ingredient in foods.

The main scientific discoveries on Aloe vera published mainly in the last three decades are presented in this work. After describing Aloe from a botanical point of view, the papers related with the chemical composition of different parts of the leaf of Aloe, particularly those in which the gel is described and are presented in a synthetic manner. The chemical analyses reveal that Aloe gel contains mannose polymers with some glucose and other sugars, among which the most important is Acemannan. Besides these, other components such as glycoproteins, enzymes, amino acids, vitamins, and minerals are described. Different factors also affecting the chemical composition of the gel, such as species and variety, climatic and soil conditions, cultivation methods, processing and preservation, are enumerated and discussed. On the other hand, the main therapeutic applications have been revised and the possible damaging effects of Aloe are also commented upon. A special emphasis is placed on the biologically active compounds or groups of compounds responsible for the therapeutic applications and which are their action mechanisms. The paper concludes that more research is needed to confirm the therapeutic and beneficial effects and to definitively clarify the myth surrounding Aloe vera. A general view on the problem of the commercialization and establishment of the quality and safety of Aloe products in the food industry has been offered here. The main points and European regulations that need to be considered regarding the quality control of prepared Aloe products are presented in this paper.The main scientific discoveries on Aloe vera published mainly in the last three decades are presented in this work. After describing Aloe from a botanical point of view, the papers related with the chemical composition of different parts of the leaf of Aloe, particularly those in which the gel is described and are presented in a synthetic manner. The chemical analyses reveal that Aloe gel contains mannose polymers with some glucose and other sugars, among which the most important is Acemannan. Besides these, other components such as glycoproteins, enzymes, amino acids, vitamins, and minerals are described. Different factors also affecting the chemical composition of the gel, such as species and variety, climatic and soil conditions, cultivation methods, processing and preservation, are enumerated and discussed. On the other hand, the main therapeutic applications have been revised and the possible damaging effects of Aloe are also commented upon. A special emphasis is placed on the biologically active compounds or groups of compounds responsible for the therapeutic applications and which are their action mechanisms. The paper concludes that more research is needed to confirm the therapeutic and beneficial effects and to definitively clarify the myth surrounding Aloe vera. A general view on the problem of the commercialization and establishment of the quality and safety of Aloe products in the food industry has been offered here. The main points and European regulations that need to be considered regarding the quality control of prepared Aloe products are presented in this paper.

Mineral concentrations in cultivars of potatoes

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.

Serum copper and zinc concentrations in a representative sample of the Canarian population

Serum copper (Cu) and zinc (Zn) concentrations of 395 individuals (187 males + 208 females) living in Canary Islands were determined by flame atomic absorption spectrometry. The mean copper and zinc concentrations were 1.10 ± 0.25 mg/L and 1.16 ± 0.52 mg/L respectively. Our data were similar to other data published in other Spanish regions. Individuals from Lanzarote presented a mean Cu and Zn concentrations higher (p 0.05) among the different age intervals. No clear trends in the serum Cu and Zn concentrations were observed when drinking and smoking habits were considered. The increase of physical exercise reduced (p < 0.05) the serum Cu concentrations.

Analysis of organic acid content in cultivars of tomato harvested in Tenerife

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.

Serum selenium concentration in a representative sample of the Canarian population

The concentration of serum selenium in 395 individuals (187 males + 218 females) living in the Canary Islands, Spain was determined by hydride generation atomic absorption spectrometry. The mean selenium concentration was 74.7 +/- 25.2 microg/l ranging between 7.86 and 182.3 microg/l. Twenty-two adults (7.2% of the total) had serum selenium concentrations under 45 microg/l. It is widely accepted that below this selenium serum concentration (45 microg/l) there is an increased risk of cardiovascular disease and cancer. Our results fall within data recently published in other Spanish and European regions and are much lower than data observed in USA or seleniferous regions. The estimated Se intakes of our population were lower than the Recommended Dietary Allowances for American people. Individuals from Lanzarote had a mean Se concentration significantly higher than individuals from the other islands. This could be attributed to differences in Se content of soil and/or differences in dietary habits of the populations. Serum selenium concentration did not vary with the sex of the subjects. Individuals younger than 14 years old had a serum selenium concentration significantly lower than the rest of the individuals. No relationship with socio-economic status, educational level, smoking habits, physical exercise or beer consumption was found. However, individuals who consume wine more than three times a week showed higher selenium concentrations than individuals with lower consumption. Also, individuals with consumption above seven units of spirit drinks a week had the highest mean selenium concentration.

Influence of the cultivar on the organic acid and sugar composition of potatoes

BACKGROUND Citric, malic, tartaric, oxalic, ascorbic, aconitic and fumaric acids, and sucrose, fructose and glucose, were determined in ten potato cultivars (Azucena negra, Bonita, Bonita negra, Borralla, Colorada de baga, Mora, Negra, Palmera lagarteada, Peluca blanca and Terrenta) from the Canary Islands in order to differentiate them. The influence of the production zone was also considered. RESULTS Citric acid and sucrose were the most abundant organic acid and sugar, respectively. There were significant differences in all the analysed sugars and organic acids between the potato cultivars, except for oxalic and malic acids. Differences associated with the production zone were found in the contents of organic acids for some cultivars. Linear discriminant analysis is a useful tool to differentiate the potato samples according to the cultivar and the zone of production. CONCLUSIONS Seven organic acids (citric, oxalic, malic, tartaric, aconitic, fumaric, and ascorbic acids) were identified and quantified in potatoes. The main sugars (sucrose, glucose and fructose) were also determined. The genetic information of the cultivars determines marked differences in sugars and organic acid contents among the analysed potato cultivars. The soil and climatic conditions affect the organic acid and sugar contents of some potato cultivars.

Organic Acid Contents in Onion Cultivars (Allium cepa L.)

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.

Serum manganese concentrations in a representative sample of the Canarian population

Serum manganese (Mn) concentrations of 368 individuals 6–75 yr of age (179 males and 189 females) living in the Canary Islands were determined by graphite furnace atomic absorption spectrometry. The mean manganese concentration was 1.06 ± 0.62 µg/L, ranging between 0.19 and 3.33 µg/L. Most of the analyzed samples (63.3% of the samples) fall within the reference interval (0.54–1.76 µg/L) for apparently healthy people. Individuals from Fuerteventura presented with mean Mn concentrations significantly higher than individuals from the rest of the islands. This could be attributed to differences in the Mn content of soil and/or differences in dietary habits of the population. Serum Mn concentration did not vary with gender, and individuals younger than 18 yr old had the highest mean Mn concentration, compared to the rest of the age groups considered. No relation to socioeconomic status, educational level, and tobacco or alcohol consumption was found. However, the serum Mn concentration tended to decrease when increasing the consumption of wine or beer. Sportsmen presented significantly higher serum Mn concentrations than the rest.

Physicochemical characterization of cactus pads from Opuntia dillenii and Opuntia ficus indica.

Physicochemical characteristics (weight, length, width, thickness, moisture, Brix degree, total fiber, protein, ash, pH, acidity, ascorbic acid, total phenolic compounds, P, Na, K, Ca, Mg, Fe, Cu, Zn, Mn and Cr) were determined in cactus pads from Opuntia dillenii and Opuntia ficus indica. The physicochemical characteristics of both species were clearly different. There were important differences between the orange and green fruit pulp of O. ficus indica; the cactus pads of O. dillenii could be differentiated according to the region (North and South). Consumption of cactus pads contributes to the intake of dietary fiber, total phenolic compounds, K, Mg, Mn and Cr. Applying factor and/or discriminant analysis, the cactus pad samples were clearly differentiated according to the species, the fruit pulp color and production region.

Comparison of the mineral and trace element concentrations between 'gazpacho' and the vegetables used in its elaboration.

Contents of moisture, ash and minerals and trace elements (sodium, potassium, calcium, magnesium, iron, copper, zinc and manganese) were determined in vegetable samples—garlic, tomato, white onion, cucumber, pepper—in ‘gazpacho’, which was elaborated using these vegetables. The mean sodium concentration in ‘gazpacho’ was much higher than those mean values observed in the fresh vegetables. The mean values of the minerals studied in the ‘gazpacho’, except sodium and calcium, tend to be lower than the mean values in the vegetables used. Garlic presented significantly higher mean contents of the trace elements than the rest of the vegetables and the ‘gazpacho’. Many highly significant correlations between all the minerals analyzed, except calcium, were observed. Factor analysis makes it possible to differentiate the samples of garlic, onion, and ‘gazpacho’ from one another, and from the rest of the vegetables considered.Contents of moisture, ash and minerals and trace elements (sodium, potassium, calcium, magnesium, iron, copper, zinc and manganese) were determined in vegetable samples—garlic, tomato, white onion, cucumber, pepper—in ‘gazpacho’, which was elaborated using these vegetables. The mean sodium concentration in ‘gazpacho’ was much higher than those mean values observed in the fresh vegetables. The mean values of the minerals studied in the ‘gazpacho’, except sodium and calcium, tend to be lower than the mean values in the vegetables used. Garlic presented significantly higher mean contents of the trace elements than the rest of the vegetables and the ‘gazpacho’. Many highly significant correlations between all the minerals analyzed, except calcium, were observed. Factor analysis makes it possible to differentiate the samples of garlic, onion, and ‘gazpacho’ from one another, and from the rest of the vegetables considered.