Publicações Científicas
URI permanente desta seção${dspace.url}/handle/123456789/3352
Navegar
3 resultados
Resultados da Pesquisa
Item Physicochemical comparison of aqueous extracts from Peruvian coffee husks (Caturra, Catimor and Geisha) varieties(Universidade Federal de Lavras, 2023-12-19) Yance, Maciela Yoselyn Puñez; Peréz, Grover Chuquipiondo; Galdos, María Estela Ayala; Pariona-Velarde, DanielThe study aimed to determine and compare the physico-chemical characteristics of coffee husks aqueous extracts corresponding to three Peruvian varieties of Arabica coffee: Caturra, Catimor and Geisha. Each sample was dehydrated at 45 °C for 10 hours, ground, sieved and dissolved in 2.5% w/w water. Aqueous extracts were obtained and analyzed for pH, total solids (TS), whiteness index (WI), reducing sugars (RS), total phenols (TP) and reducing power (RP) for the antioxidant activity The influence of coffee varieties, particle sizes (0.097, 0.033, and 0.0139in) and extraction temperaturas (60 and 80 ºC) on the physicochemical characteristics of their corresponding extracts was determined by factorial analysis. Correlation between TP and RP was significant while RS and TP showed an inverse relationship. Cluster values indicate similarity between Geisha extracts at 60 and 80 °C and the corresponding Catimor extracts at 80 °C. Differences were observed between the Catimor extracts at 60 °C and Caturra at 60 and 80 °C. Based on these results, the extracts exhibit distinctive intrinsic characteristics. The Caturra extracts at 60 °C showed the highest antioxidant capacity, while the Catimor extracts at 60 °C or 80 °C exhibited the highest WI (water holding capacity) and pH values. Additionally, the Geisha extracts displayed the highest amount of RS (reducing sugars). These findings are of utmost significance for the development of novel products using Peruvian coffee husks, encompassing beverages, concentrated juices, and the enhancement of coffee quality offered in coffee shops. These developments can be guided by the physicochemical characteristics obtained in this study.Item Evaluation of aqueous coffee husks extracts as a corrosion inhibitor of 1020 carbon steel in 1 mol L-1 HCl solution(ABM, ABC, ABPol, 2019) Ramos, Samantha Alcântara Fernandes; Senna, Lilian Ferreira de; Lago, Dalva Cristina Baptista doCorrosive processes in acidic medium reduce the performance and durability of metallic materials, causing problems to several industries. Corrosion inhibitors are commonly used to decrease these effects. As these inhibitors must be ecologically friendly currently, this work evaluated the anticorrosive effect of natural extracts of coffee husks (Coffea arabica L.) in the protection of carbon steel in 1 mol L-1 HCl solution. Extractions were performed using water as the extraction solvent. The polyphenols content increased with the extraction temperature, and the extracts were produced using 100 ºC. Extract concentrations of 10, 20 and 30 % v/v were analyzed as inhibitors for carbon steel in acid medium, using weight loss and electrochemical tests, as well as scanning electron microscopy. There was an increase in the inhibition efficiency as the extract concentration increased, reaching values around 97 % using 30 %v/v of extract for the weight loss tests.Item Kinetic parameters study for the slow pyrolysis of coffee residues based on thermogravimetric analysis(Sociedade Brasileira de Química, 2020) Tibola, Fernando L.; Oliveira, Tiago J. P. de; Cerqueira, Daniel A.; Ataíde, Carlos H.; Cardoso, Cássia R.Thermal decomposition of coffee husks was investigated by thermogravimetric analyses. The proximate, ultimate and composition analyses were performed. Thermogravimetric tests were realized, the material was heated to 1173 K using five heating rates: 5, 10, 15, 20, 25 K min-1. The kinetic parameters were estimated using the methods of Kissinger-Akahira-Sunose and Friedman, the distributed activation energy model and the independent parallel reactions model. The isoconversional models of Kissinger-Akahira-Sunose and Friedman showed the dependence between determined values of activation energy and mass conversion, the activation energy values varied from 1437.39 to 199.22 kJ mol-1 for Kissinger-Akahira-Sunose and from 127.81 to 230.35 kJ mol-1 for Friedman model. The values of activation energy were determined for Miura-Maki method; varying from 137.39 to 199.22 kJ mol-1. The model of parallel and independent reactions showed the presence of six different reactions (with activation energy values varying from 42.0 to 214.2 kJ mol-1) occurring during coffee husks pyrolysis, indicating a complex reaction. Currently, works regarding the determination of kinetic parameters for coffee husks pyrolysis are not common. The present work is the first report using the model of parallel and independent reactions to estimate kinetic parameters for pyrolysis of coffee husks, a residue widely generated worldwide.