Abstract
Brazil is a major producer of special natural foods and beverages that are commercialised and sold, locally and globally, as natural and processed products. Many are marketed as good sources of elements (minerals) and polyphenols, that play an important role in human health. At present, very few scientific studies have reported the chemical composition of these natural foods or beverages obtained in Brazil. The aim of this research was to determine the levels of elements and polyphenols in yerba mate, roasted coffee and açaí berries. The chemical composition was determined for the elemental content by inductively coupled plasma mass spectrometry and polyphenols by ultra-high performance liquid chromatography and ultraviolet–visible spectrophotometry. The elemental levels of non-commercial yerba mate leaves from the Barão de Cotegipe plantation (southern Brazil) had higher levels in the old leaves. New leaves grown on trees from an organic plantation had higher elemental levels, especially when compared with other plantations treated with NPK fertilisers. Moreover, higher elemental levels were found in plants grown in traditional organic plantations than in natural forests. The elemental levels of commercial yerba mate products from Brazil and Argentina were found to be similar. All levels were higher for commercial tea bag products than for green loose material. In Brazil, yerba mate is also sold as a roasted product (loose and tea bag) which had higher elemental levels than that for the green loose material. Infusions prepared using tea bag samples had higher elemental, polyphenol and xanthine levels than that for green loose regular infusions. Moreover, regular infusions made with green loose yerba mate had significantly higher levels of trace elements, polyphenols and xanthines in comparison with the roasted samples. All infusion methods (regular, Brazilian and bombilla) represented 0.1 to 5.0 % of the recommended daily allowance (RDA) of the trace elements measured. A regular infusion serving (1 cup of 200 mL) would provide 23.7 to 106.0 % for males and 30.3 to 135.5 % for females of the manganese RDA, depending on the type of yerba mate product. In terms of the total polyphenol intake, a regular infusion serving (200 mL) could contribute 4.0 to 14.5 % of the daily intake. The effect of roasting different coffee varieties (Obatã, Catuaí, Bourbon Amarelo and blend) collected from the Fazenda Palmares and Flor plantations (Amparo, São Paulo State) resulted in a slight increase of the elemental content of the beans during the roasting process. The total polyphenol content of coffee infusions, produced from beans collected at different times of the roasting process, showed a variation of 7.0 to 52.0 % higher levels in the dark roast (10 min) when compared to the green bean infusions (0 min). The chlorogenic acids and caffeine data showed a similar trend with an increase in the levels of the infusions prepared using the medium roast coffee. A cup of coffee (92 mL) can contribute up to 7.0 % of the estimated daily intake of polyphenols. Açaí berries obtained from the Amazon region are a major nutritional source for the local population and the processed pulp is becoming a major national and global ‘super-fruit’ product. The non-commercial purple mature pulp had a significantly higher concentration of total polyphenols and anthocyanins in comparison with the white samples (different variety). These samples were found to have high antioxidant activity due to the higher levels of total polyphenols and total anthocyanins when compared to the commercial purple and non-commercial white pulp samples. The strong antioxidant effect of açaí pulp was confirmed on mouse cells through the inhibition of producing radical oxygen species (ROS). A wound healing experiment performed using human fibroblast cells confirmed a migration effect on cells subjected to açaí pulp extracts. These results are very important, as such an experiment has never been reported, and implies that processed açaí pulp may have potential as a wound healing agent. There were no statistically significant differences in the elemental content between purple and white pulp samples. Processed açaí pulp, with less water added, had higher elemental levels (based on a fresh weight). Based on a regular consumption of purple açaí (500g), the dietary intake of total polyphenols would be more than 100% of the RDA. The consumption of açaí represents a good source of Mn (average of 1500% of the RDA), Cu (90%), Mg (30%), Ca (20%) and Zn (15%). In summary, this research provides a unique database of chemical values using analytically robust methods that can be used to evaluate the nutritional quality of Brazilian natural and commercial products and the impact of consumption on dietary intake and human health.