Coffee Science_v.16, 2021

URI permanente para esta coleçãohttps://thoth.dti.ufv.br/handle/123456789/12727

Navegar

Agora exibindo 1 - 8 de 8

Classification of the maturity stage of coffee cherries using comparative feature and machine learning
(Editora UFLA, 2021) Velásquez, Sebastián; Franco, Arlet Patricia; Peña, Néstor; Bohórquez, Juan Carlos; Gutiérrez, Nelson
This work presents the use of multiple techniques (i.e., physicochemical and spectral) applied to harvested coffee cherries for the postharvest classification of the maturity stage. The moisture content (MC), total soluble solids (TSS), bulk density, fruits’ hardness, CIEL*a*b parameters and the dielectric spectroscopy methods were applied on coffee cherries at seven maturity stages. These maturity stages were assessed according to the days after flowering (DAF) and the physical appearance as traditionally performed by growers. An increase of the green-to-red ratio (i.e., a*) parameter was perceived, accompanied by a monotonic response for the hardness, TSS and bulk density with a maximum moisture content at stage 5. In the case of the dielectric spectroscopy technique, the loss parameter presented higher losses for unripe stages at the ionic conduction region. To compare the individual performance of each of the techniques, three machine learning methods were used: random forest (RF), support vector machine (SVM) and k-nearest neighbours (k-NN). The meta-parameters for these techniques were optimized for each case to achieve the best performance possible. Furthermore, as the dielectric response is of spectral nature, recursive feature selection was applied and the 500 MHz to 1.3 GHz frequency range selected for the task. The highest performance was obtained for the colorimetric (75.1%) and hardness (72.5%) responses, while the lowest was obtained for the moisture content (45.5%). The dielectric spectroscopy response presented a promising response (56.8%), that achieved a clear separation of unripe from ripe stages, except for stage 5 in which some of the samples were classified as stage 2. Most techniques studied are compatible with field conditions, and the dielectric technique shows potential to be transferred based on available software-radio defined platforms.
Cold coffee seeds storage with different water content
(Editora UFLA, 2021) Penido, Amanda Carvalho; Reis, Venícius Urbano Vilela; Rezende, Édila Maria de; Rocha, Debora Kelli; Oliveira, João Almir; Rosa, Sttela Dellyzete Veiga Franco da
Coffee seeds are classified as intermediate because they have low tolerance to desiccation and low longevity. Consequently, moisture control and storage conditions are important factors in maintaining the physiological quality of these seeds. Thus, the objective in this work was to evaluate the water content effect on coffee seed longevity. Seeds of five Coffea arabica cultivars from the 2016/2017 crop were used. Part of the harvested seeds was dried in the shade until reach 12% moisture and the other part did not go through drying process, remaining with 40% water content. The seeds were stored in a cold chamber at 10 ºC for a period of nine months, and the physiological quality was evaluated every three months by germination, root protrusion, seedlings with expanded cotyledonary leaves, seedling dry mass and enzymatic analysis of catalase enzymes and superoxide dismutase. Regardless of the cultivar, wet seeds coffee storage provides better maintenance of physiological quality for up to nine months. Seedling vigor is reduced throughout the storage period, regardless of seed water content.
Evaluation of species transfer models in the cfd simulation of fixed bed soybean drying
(Editora UFLA, 2021) Mateus, Felipe Leonardo Barcelos; Faria, Mauro Magalhães Leite; Petri Junior, Irineu
The drying is fundamental to the preservation of materials, particularly food, which is sensible to damaging related to moisture because of its hygroscopic nature. The drying increases the shelf life of these products and reduces their overall weight, which facilitates the logistics and aggregates value to the product. Computational Fluid Dynamics is a potentially facilitating tool for the analysis of drying variables, such as velocity, air temperature, and particle temperature, which have great influence on the drying rate. This work aimed at studying different numeric models for the simulation of a fixed bed drying operation, analyzing the influence of the equilibrium ratio and water diffusivity in the solid on the results. The computations were made in the software FLUENT 19.2, using the Multiphase Eulerian Granular Model with packed bed configuration and different mass transfer models: Constant, Species-Con stant, Species-Sherwood, Ranz-Marshall, and Hughmark, as well as heat transfer models: Constant Heat Transfer Coefficient, Constant Nusselt Number, Ranz-Marshall, and Hughmark. The mass transfer models with the best performance were the Ranz-Marshall and Hughmark models. A strong influence of the equilibrium ratio was observed for both models, and a moderate influence of the water diffusivity. The influence of equilibrium ratio and water diffu sivity was not observed for the other models. The heat transfer models did not present expressive difference, and the system reached thermal equilibrium quickly. The overall study of the models and the influence of different parameters was effective, and was able to document the obtained results for future optimization and further investigation of the numeric model.
Isolation and identification of a native microbial consortium for the coffee pulp degradation above 2000 masl
(Editora UFLA, 2021) Cuba, Marcela N. Arteaga; Dilas-Jiménez, Josué O.; Díaz, Norberto Villanueva; Miranda, Ofelia C. Cernaqué; Santillán, Segundo M. Tafur; García, José Enrique Olivera; Mugruza-Vassallo, Carlos A.
Pulp and mucilage constitute the most abundant by-products of the processing of coffee and inadequate handling produces high-rates of pollution. Considering that in nature there is a large variety of cellulolytic microorganisms which can intervene in the degradation of coffee pulp, the inclusion of a native microbial cellulolytic consortium was assessed. The sample for isolation consisted of coffee pulp and soil from a humid forest at more than 2,000 masl. Nutrient agar was used as a means of isolation for bacteria, and malt agar for fungi, supplemented with 50% soil extract and 1% carboxylmethylbcellulose. This achieved the isolation of 118 strains of bacteria and 114 of fungi. Cellulolytic activity was established using the filter paper test, assessing and selecting only those that presented higher glucose production, among them 12 strains of fungi and 11 strains of bacteria. To obtain the microbial consortium, randomized blends were performed for both fungi and bacteria, again assessing the production of glucose. The bacterial consortium was made up of Ochrobactrum pseudo grignonense, Paenibacillus lauruscon and Bacillus xiamenensis and the fungal consortium by Fusarium sp., Penicillum sp., Cylindrocarpon sp. The optimal treatment achieved a complete degradation of the pulp in 28 days, that would contribute to the recovery and conservation of the coffee ecosystem. The main interpretation was that a wet environment at more than 2,000 masl is still suitable for coffee composting but different bacterial and fungi consortia were found to support other recent work done with one type of consortium.
Modeling effectiveness analysis of momentum and heat transfer in a fixed bed silo-dryer through computational fluid-dynamics
(Editora UFLA, 2021) Mateus, Felipe Leonardo Barcelos; Petri Júnior, Irineu
The drying procedure is of great use in the industry, being capable of increasing the shelf life of many products, in addition to facilitate its transport and storage. The operation is essential for coffee beans to remove their excessive moisture content. The silo-drier has potential to ensure sensorial qualities through the intermittent drying, as well as with optimizations in the energy consumption. The objective of this work was to study the optimization of the numeric representation of a silo-dryer system, comparing the results of three different models available in the software FLUENT® 19.2: Eulerian Multi phase Model for Granular flow with packed bed configuration disabled, the same model but with the packed bed configuration enabled, and the porous zone single-phase modelling. The convergence efficiency of these models was also analyzed through the results of the numeric residue, and the influence of the relaxation factor in the simulation results. The behavior of solid volumetric fraction, air velocity and bed temperature were qualitatively examined with hot air at the inlet. It was found that the momentum relaxation factor influenced the results. Moderately lower factors allowed for faster convergence without significant particle behavior change. Monitoring the mass residue, the enabled packed bed modelling presented lower residuals, while the porous zone modelling presented higher residuals. The packed bed and porous zone modelling reported lower air velocities in comparison to the disabled packed bed modelling, and presented satisfactory heat transfer through the temperature profiles.
Origin of black-green defect in the artificial drying of immature coffees
(Editora UFLA, 2021) Rios, Paula de Almeida; Andrade, Ednilton Tavares de; Cardoso, Danilo Barbosa
The inequality of coffee maturation leads to a large portion of green berries in the harvest. Post-harvest management techniques seek to minimize defects during the drying process, such as black-green defects in harvested immature berries. The present study aimed to investigate the minimum occurrence of black-green defects in the drying of immature coffee berries subjected to different temperature conditions and relative humidity values. In addition to fitting mathematical models to the experimental data, the effective diffusion coefficient and the water reduction rate (WRR) were determined. Nine coffee crops (Coffea arabica L.) of the Topázio Amarelo variety were harvested manually and selectively during the green maturation stage, with an initial water content of 2.106 ± 0.05 kg.kg-1 (dry basis, d.b.). After drying, the coffee was subjected to a drying treatment in a fixed-layer dryer with combined dry bulb temperatures (Dbt) of 35, 40 and 45 °C and dew point temperatures (Dpt) of 2.6, 10.8 and 16.2 °C until a final water content of 0.124 ± 0.05 kg.kg-1 (db) was reached. After drying, black-green defects were quantified as percentages. In addition to the drying kinetics, the WRR and effective diffusivity were evaluated. The lowest percentage of black-green defects occurred at a temperature of 35 °C and a Dpt of 2.6 °C (11.00%), which is the most suitable treatment for drying natural green coffees. The highest percentage of defects occurred when a Dbt of 35 °C was combined with a Dpt of 16.2 °C (14.17%). This combination showed the lowest effective diffusion coefficient of 0.551 x 10-11 m2.s-1. The Midilli model had the best fit to the experimental data for all drying combinations. The lowest WRR was 0.063 kg.kg-1.h-1 and was observed when a Dbt of 35 °C was combined with a Dpt of 16.2 °C.
Physicochemical parameters of arabica fermented coffee in different altitudes
(Editora UFLA, 2021) Pereira, Lucas Louzada; Guarçoni, Rogério Carvalho; Moreli, Aldemar Polonini; Pinheiro, Patrícia Fontes; Pinheiro, Carlos Alexandre; Moreira, Taís Rizzo; Siqueira, Evandro de Andrade; Caten, Carla Schwengber ten
The coffee quality interacts with different processes, techniques, analyses, and concepts. This study applied six different forms of wet fermentation to coffee from different altitude ranges to understand how coffee quality interacts with the physicochemical profile and its possible relations with sensory variables. Statistical analysis was performed through combined analyses of variance of the experiments, and the means were compared by the Tukey test considering the significance level of 5%. Regression models were tested by the F-test and the parameters by the t-test, followed by Pearson correlation analysis between the sensory and physicochemical characteristics and between physicochemical variables. The results indicate a correlation between sensory and physicochemical variables for total titratable acidity and indicate that these compounds are affected by the manner of fermentation applied as well as the edaphic and climatic conditions.
Post-harvest processing of coffee: an overview
(Editora UFLA, 2021) Das, Suryatapa
Coffee is known as one of the most popular beverages around the world. Coffee belongs to the botanical family Rubiaceae and genus coffea. The two most economically important species are C. arabica (arabica coffee) and C. canephora (robusta coffee).The health benefits of coffee are due to presence of many biologically active components such as caffeine, chlorogenic acid, nicotinic acid, quinolinic acid, trigonelline, tannic acid, and pyrogolic acid. The postharvest processing of coffee cherry involves dry or wet processing, grading, sorting, marketing, blending, and roasting. A series of physical and chemical changes occur during coffee roasting that are responsible for the development of pleasant aroma and flavour of coffee.