Polysaccharides of nutritional interest in jicama (Pachyrhizus erosus) during root development.

Jicama root applications have focused on their nutraceutical properties without clearly specifying which compounds are related to this effect. Thus, the aim of the present study was to identify the changes in polysaccharides of nutraceutical interest in two commercial jicama roots (YS - Yellow Seed; PS - Purple Seed) during four stages of maturation, focusing on starch, fructooligosaccharides, and pectin (via galacturonic acid), and on their glycemic index, with the goal of determining, if possible, the best cost-effectiveness between jicama growing stages and nutraceutical effect. Both materials (YS, PS) presented similar growth rates (0.069 and 0.072 cm/day) and final sizes (12.7 ± 1.25, 12.3 ± 1.63 cm). Changes in size were accompanied by changes in protein, fiber, ashes, lipids, and carbohydrates, after 106 or 127 days of growing. It was also found that fructose content was higher than glucose during the maturing stages, possibly because of the hydrolysis of fructooligosaccharides or sucrose for starch production. Concerning inulin, its levels decreased (<6.0%), after the first days (YS: 13.4% ± 0.7%; PS: 8.4% ± 0.2%, 106 days); however, during development, the presence of other fructooligosaccharides was observed (nystose-YS 106 days 15.8% ± 0.9% and PS-106 days 18.5% ± 0.1%), while galacturonic acid and native starch levels increased, which must be related to the jicama's low glycemic index found (<25%), and their nutraceutical properties. This work proves the presence of inulin in jicama roots by analytical methods, its dependence on root development and classifies jicama as a low glycemic index food, supporting its nutraceutical character.

Ammonia-Oligotrophic and Diazotrophic Heavy Metal-Resistant Serratia liquefaciens Strains from Pioneer Plants and Mine Tailings.

Mine tailings are man-made environments characterized by low levels of organic carbon and assimilable nitrogen, as well as moderate concentrations of heavy metals. For the introduction of nitrogen into these environments, a key role is played by ammonia-oligotrophic/diazotrophic heavy metal-resistant guilds. In mine tailings from Zacatecas, Mexico, Serratia liquefaciens was the dominant heterotrophic culturable species isolated in N-free media from bulk mine tailings as well as the rhizosphere, roots, and aerial parts of pioneer plants. S. liquefaciens strains proved to be a meta-population with high intraspecific genetic diversity and a potential to respond to these extreme conditions. The phenotypic and genotypic features of these strains reveal the potential adaptation of S. liquefaciens to oligotrophic and nitrogen-limited mine tailings with high concentrations of heavy metals. These features include ammonia-oligotrophic growth, nitrogen fixation, siderophore and indoleacetic acid production, phosphate solubilization, biofilm formation, moderate tolerance to heavy metals under conditions of diverse nitrogen availability, and the presence of zntA, amtB, and nifH genes. The acetylene reduction assay suggests low nitrogen-fixing activity. The nifH gene was harbored in a plasmid of ∼60 kb and probably was acquired by a horizontal gene transfer event from Klebsiella variicola.

Evaluation of extracts from potato and tomato wastes as natural antioxidant additives

The industrialization of potato and tomato produces large amount of wastes. Previous studies have demonstrated that these by-products are rich in antioxidant compounds. In this study, the composition and antioxidant efficacy of extracts from potato and tomato by-products were determined in order to evaluate their potential as food additives. Potato and tomato wastes showed to be good sources of fiber, protein and antioxidants. The antioxidant activity and total phenolic, carotenoid and lycopene contents were determined in methanol, ethanol and acetone extracts of the residues. Methanol was the best solvent for the extraction of phenolics while acetone was the best in the extraction of carotenoids in both residues. The greatest antioxidant activity (14.10 µmol Trolox/g) resulted when potato peels were extracted with ethanol. The oxidative stability of canola oil containing either ethanol extracts of potato and tomato wastes (200 and 400 mg/kg) or the synthetic antioxidant BHT (200 mg/kg), compared to oil without antioxidants, was evaluated by measuring their peroxide values, conjugated dienes and p-anisidine value after 72 and 144 h storage at 65 °C. The order of antioxidant efficacy was as follows: potato peels > BHT > tomato residues. The results showed that ethanol extracts of potato and tomato waste could be used as natural antioxidant additives in the protection of vegetable oils(AU)

La industrialización de la papa y el jitomate genera grandes cantidades de desechos. Estudios previos han demostrado que estos subproductos son ricos en compuestos antioxidantes. En este trabajo se determinaron la composición y la eficacia antioxidante de subproductos de papa y jitomate con el fin de evaluar su potencial como aditivos alimentarios. Los desechos de papa y jitomate demostraron ser buenas fuentes de fibra, proteína y antioxidantes. Se determinó la actividad antioxidante y el contenido de compuestos fenólicos, carotenoides y licopeno en extractos metanólicos, etanólicos y acetónicos de los residuos. El mejor disolvente para la extracción de compuestos fenólicos fue el metanol mientras que la acetona fue el mejor disolvente para extraer los carotenoides. La mayor actividad antioxidante (14.10 µmol Trolox/g) se obtuvo cuando las cáscaras de papa se extrajeron con etanol. La estabilidad oxidativa de aceite de canola adicionado con los extractos etanólicos de desechos de papa o jitomate (200 y 400 mg/kg) o con el antioxidante sintético BHT (200 mg/kg), comparándolos con aceite sin antioxidantes, se evaluó mediante la medición de su índice de peróxidos, dienos conjugados e índice de anisidina, después de almacenarlo a 65°C durante 72 y 144 h. El orden de eficacia antioxidante fue como sigue: cáscara de papa > BHT > residuos de jitomate. Los resultados demostraron que los extractos etanólicos de los desperdicios de papa y jitomate podrían ser usados como aditivos antioxidantes naturales en la protección de aceites vegetales(AU)