Biblioteca do Café
URI permanente desta comunidadehttps://thoth.dti.ufv.br/handle/123456789/1
Navegar
3 resultados
Resultados da Pesquisa
Item Arabica coffee flow properties assessed using different roasts and particle sizes during storage(Instituto de Tecnologia de Alimentos – ITAL, 2022-02-18) Oliveira, Gabriel Henrique Horta de; Corrêa, Paulo Cesar; Oliveira, Ana Paula Lelis Rodrigues de; Vargas-Elías, Guillermo Asdrúbal; Calil Júnior, CarlitoFlowability of agricultural products is an important factor to be considered at post-harvest, thus impacting directly on number of operations and the design of machinery. This study aimed to evaluate and determine the K coefficient and flow properties as a function of different levels of roasting, grain size, temperature and storage. Coffee beans were roasted at medium light and moderately dark, then ground at fine, medium and coarse sizes. An additional coffee lot was not ground. Samples were stored at 10 ºC and 30 ºC and analyzed during storage (0, 30, 60, 120 and 180 days), regarding internal and external friction coefficients, angle of internal friction, effective angle of internal friction, wall friction angle (concrete, rough steel and wood) and lateral pressure coefficient (K coefficient). Angle of internal friction varied significantly due to particle size and roast degree. Moderately dark roast with fine particle size led to higher values (about 29.5 º) of wall friction angle. The wood sample was the material with the highest values of wall friction angle, followed by the concrete and steel samples, when compared at the same storage temperature, roast degree and particle size. Whole coffee was classified as free-flowing. Fine particle size leads to cohesive flow characteristic, according to the flow function. Coffee roasted at medium light, kept whole requires storage facilities with higher pressure support, accordingly to the K coefficient values.Item Cinética do aquecimento, expansão volumétrica e perda de massa em grãos de café durante a torrefação(Universidade Federal de Viçosa, 2014-08-26) Vargas-Elías, Guillermo Asdrúbal; Corrêa, Paulo CésarObjetivou-se com este trabalho estudar a transferência de calor e massa nas etapas do processo de torrefação do café pela cinética do aquecimento, da expansão volumétrica e a perda de massa dos grãos. Para diferenciar as cinéticas do aquecimento dos grãos foram empregadas quatro temperaturas iniciais do processo (290, 310, 345 e 380°C), que diminuíram devido às condições não isotérmicas da parede, em contato com os grãos. As cinéticas foram adaptadas a um modelo físico de aquecimento dos grãos, considerando que o calor transferido aos grãos é usado tanto para o aquecimento da massa quanto para a evaporação da água na superfície dos grãos. A cinética do aquecimento dos grãos foi ajustada adequadamente a torra dos grãos de café em função da temperatura do torrador. Observou-se nos primeiros minutos de torra que a temperatura dos grãos aumentou bruscamente, após um ponto de inflexão, atingiu uma tendência linear até o final do processo. A transferência de massa foi analisada pelas mudanças físicas causadas pelos gases liberados durante o processo tanto de vapor quanto de dióxido de carbono, o que permitiu separar o processo em duas etapas; de secagem e de torrefação. Foi desenvolvido um modelo matemático baseado na lei das reações químicas para representar o efeito dos gases na expansão volumétrica dos grãos e na transformação da massa seca. A cinética da expansão aparente e a de perda de massa seca do café dependeram diretamente da temperatura do torrador, pelo que foi adequadamente representado pelo modelo de Arrhenius, onde foram determinadas as respectivas energias de ativação para cada etapa.Item Particle size and roasting on water sorption in conilon coffee during storage(Editora UFLA, 2016-04) Corrêa, Paulo Cesar; Oliveira, Gabriel Henrique Horta de; Oliveira, Ana Paula Lelis Rodrigues de; Vargas-Elías, Guillermo Asdrúbal; Baptestini, Fernanda MachadoThe aim of this work was to evaluate alterations on the water sorption of coffee due to the effect of roast, grind and storage in two temperatures (10 and 30 oC) during 180 days. Crude grain coffee (Coffea canephora) with average initial moisture content of 12.61 % (d.b.) was used. Grain was roasted at two levels: medium light (ML) and moderately dark (MD). Afterwards, grain was processed in three different particle sizes: fine (0.59 mm), medium (0.84 mm) and coarse (1.19 mm), besides the whole coffee lot. Samples prepared were then stored in two temperatures (10 and 30 oC). These were analyzed during six months, at five distinct times (0, 30, 60, 120 and 180 days) regarding moisture content and water activity. Furthermore, mathematical modeling and thermodynamic properties acquisition of the coffee moisture adsorption process were accomplished. A split plot design was used, in which plots consisted of storage period and split-plots consisted of a 2 x 4 x 2 factorial (two roasting degrees, four particle sizes and two storage temperatures), with five repetitions.It was concluded thatparticle size did not significantly affectedmoisture content of coffee, independently of roast degree; Sigma-Copace model best represented hygroscopic equilibrium for sorption of roasted coffee; with moisture content reduction, an increase of differential enthalpy and entropy of sorption and Gibbs free energy occurs.