Despite decades of research on marine algae, there are still significant gaps in basic knowledge about chemical composition of these organisms, especially in tropical environments. In this study, the amino acid compos...Despite decades of research on marine algae, there are still significant gaps in basic knowledge about chemical composition of these organisms, especially in tropical environments. In this study, the amino acid composition and contents of total nitrogen, phosphorus, lipid, carbohydrate and protein were determined in Asparagopsis taxiformis, Centroceras clavulatum, Chaetomorpha aerea, Sargassum filipendula and Spyridia hypnoides. The seaweeds showed low lipid contents (lower than 5.5% d.w. in all species) and were rich in carbohydrates (more than 16% d.w. in all seaweeds). The percentage of nitrogen, phosphorus and protein varied widely among species, which red algae showed the highest con-centrations. The amino acid composition was similar among the seaweeds, which glutamic acid, aspartic acid and leu-cine as the most abundant. All species are poor in histidine. An average of 24.2% of the total nitrogen is non-proteinaceous. From data of total amino acid and total nitrogen, specific nitrogen-to-protein conversion factors were calculated for each species. The nitrogen-to-protein conversion factors calculated ranged from 4.51 to 5.21, with an overall average of 4.86. These findings show that the traditional conversion factor of 6.25 should be avoided for seaweeds, since it overestimates the actual protein content.展开更多
Coffee is currently the second largest commodity on the world market today,and there is great concern about the quality of the beans exported from producer countries to Europe and USA.Practices such as using blends of...Coffee is currently the second largest commodity on the world market today,and there is great concern about the quality of the beans exported from producer countries to Europe and USA.Practices such as using blends of different species and adding low-cost raw materials,such as chicory,corn,and soybean,impair the sensory and functional characteristics of the drink made from roasted and ground coffee beans.There is a need to adopt more efficient analytical methods than the microscopy technique currently used.The first chromatographic method used to determine fraud was reported in 1958.This method used paper chromatography to differentiate between coffee and chicory based on the free reducing sugars.As of the 1980s,different methods involving high-performance liquid chromatography and gas chromatography were developed in order to demonstrate geographic authenticity,distinction between species,occurrence of adulteration,and the presence of defective beans by determining the monosaccharides,oligosaccharides,tocopherols,fatty acids,volatiles,diterpenes,sterols,and phenolic substances,among others.As far as the authors know,there are no papers published in the literature that have compiled such an extensive set of information about these chromatographic methods as here.Over the last 2 years,there has been a trend to develop analytical methods for ultra-performance liquid chromatography coupled with tandem mass spectrometry to confirm fraud in coffee,due to high sensitivity and selectivity.展开更多
基金Authors are indebted to Brazil’s National Council for Scientific and Technological Development(CNPq)and Research Support Foundation of Rio de Janeiro State(FAPERJ)for the financial support of this studyGDS thanks Coordination of Improvement of Higher Education Personnel(CAPES)for her scholarshipAuthors thank Dr.Renato Crespo Pereira(UFF)for the use of labora-tory facilities and to Dr.Joel C.De-Paula(UNIRIO)for confirming the identification of the seaweeds.
文摘Despite decades of research on marine algae, there are still significant gaps in basic knowledge about chemical composition of these organisms, especially in tropical environments. In this study, the amino acid composition and contents of total nitrogen, phosphorus, lipid, carbohydrate and protein were determined in Asparagopsis taxiformis, Centroceras clavulatum, Chaetomorpha aerea, Sargassum filipendula and Spyridia hypnoides. The seaweeds showed low lipid contents (lower than 5.5% d.w. in all species) and were rich in carbohydrates (more than 16% d.w. in all seaweeds). The percentage of nitrogen, phosphorus and protein varied widely among species, which red algae showed the highest con-centrations. The amino acid composition was similar among the seaweeds, which glutamic acid, aspartic acid and leu-cine as the most abundant. All species are poor in histidine. An average of 24.2% of the total nitrogen is non-proteinaceous. From data of total amino acid and total nitrogen, specific nitrogen-to-protein conversion factors were calculated for each species. The nitrogen-to-protein conversion factors calculated ranged from 4.51 to 5.21, with an overall average of 4.86. These findings show that the traditional conversion factor of 6.25 should be avoided for seaweeds, since it overestimates the actual protein content.
基金Universidade Federal Rural do Rio de Janeiro(UFRRJ),Empresa Brasileira de Pesquisa Agropecuária(Embrapa)and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior(CAPES)for their financial support(1020010/00542).
文摘Coffee is currently the second largest commodity on the world market today,and there is great concern about the quality of the beans exported from producer countries to Europe and USA.Practices such as using blends of different species and adding low-cost raw materials,such as chicory,corn,and soybean,impair the sensory and functional characteristics of the drink made from roasted and ground coffee beans.There is a need to adopt more efficient analytical methods than the microscopy technique currently used.The first chromatographic method used to determine fraud was reported in 1958.This method used paper chromatography to differentiate between coffee and chicory based on the free reducing sugars.As of the 1980s,different methods involving high-performance liquid chromatography and gas chromatography were developed in order to demonstrate geographic authenticity,distinction between species,occurrence of adulteration,and the presence of defective beans by determining the monosaccharides,oligosaccharides,tocopherols,fatty acids,volatiles,diterpenes,sterols,and phenolic substances,among others.As far as the authors know,there are no papers published in the literature that have compiled such an extensive set of information about these chromatographic methods as here.Over the last 2 years,there has been a trend to develop analytical methods for ultra-performance liquid chromatography coupled with tandem mass spectrometry to confirm fraud in coffee,due to high sensitivity and selectivity.
