Maricely Guevara-Sánchez

Karen Elizabet Guevara-Sánchez

Neiser Quispe-Cubas

Miguel Angel Valles-Coral

Jorge Raul Navarro-Cabrera

Lloy Pinedo

Rev. Fac. Agron. (LUZ). 2022, 39(3): e223936

ISSN 2477-9407

DOI: https://doi.org/10.47280/RevFacAgron(LUZ).v39.n3.02

Food Technology

Associate editor: Dra. Gretty R. Ettiene Rojas

University of Zulia, Faculty of Agronomy

Bolivarian Republic of Venezuela

Keywords:

Cupping

Electromechanical

Heating

Organoleptic

SCAA

Drying effect by infrared radiation on sensory quality in special coffees (Coffea arabica) cup

Efecto del secado por radiación infrarroja sobre la calidad sensorial en taza para cafés (Coffea

arabica) especiales

Efeito da secagem por radiação infravermelha na qualidade sensorial em xícara para cafés (Coffea

arabica) especiais

Asociación de productores Selva Nor Oriental-Aproselvanor,

Moyobamba, Perú.

Programa Nacional de Desarrollo Tecnológico e Innovación

– ProInnóvate, Perú.

Universidad Nacional de San Martín, Tarapoto, Perú.

Received: 02-05-2022

Accepted: 10-06-2022

Published:

30-06-2022

Abstract

The drying process of coffee (Coffea arabica) is important to achieve

quality organoleptic characteristics. The objective of the study was to

evaluate the effect of drying by means of an electromechanical system

based on infrared on sensory quality in special coffees cup. For this,

an electromechanical system was designed using infrared emitters that

combines electromagnetic radiation with conventional convective heating.

75 coffee samples were collected at three (3) height levels. The samples

underwent the traditional drying process and the electromechanical system,

to later be evaluated by professional tasters under the SCAA (Specialty

Coffee Association of America) scale. The samples dried with infrared

at 12% humidity presented a cupping value of 82.93 for cup coffee with

a smaller data dispersion than the traditional system that obtained 81.34,

in addition the t-test of non-equivalent samples indicates that its value is

signicantly better (p<0.05). We concluded that the electromechanical

system with infrared drying increased the sensory quality of coffee compared

to traditional drying.

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2-7 |

Resumen

El proceso de secado del café (Coffea arabica), es importante para

lograr características organolépticas de calidad. El objetivo del estudio

fue evaluar el efecto del secado mediante un sistema electromecánico

basado en infrarrojos sobre la calidad sensorial en taza para cafés

especiales. Para ello se diseñó un sistema electromecánico utilizando

emisores de infrarrojos que combina radiación electromagnética con

calentamiento convencional convectivo. Se recolectaron 75 muestras

de café en tres (3) niveles de altura. Las muestras se sometieron al

proceso de secado tradicional y al sistema electromecánico, para

luego ser evaluadas por catadores profesionales bajo la escala SCAA

(Specialty Coffee Association of América). Las muestras secadas con

infrarrojo al 12 % de humedad presentaron un valor de catación de

82,93 para café en taza con una dispersión de datos menor que el

sistema tradicional que obtuvo 81,34, además la prueba t de muestras

no equivalentes indica que su valor es signicativamente mejor

(p<0,05). Se concluye que el sistema electromecánico con secado

infrarrojo aumentó la calidad sensorial del café con respecto al secado

tradicional.

Palabras clave: Calentamiento, catación, electromecánico,

organoléptica, SCAA.

Resumo

O processo de secagem do café (Coffea arabica) é importante

para alcançar características organolépticas de qualidade. O objetivo

do estudo foi avaliar o efeito da secagem por meio de um sistema

eletromecânico baseado em infravermelho na qualidade sensorial

da xícara para cafés especiais. Para isso, foi projetado um sistema

eletromecânico utilizando emissores infravermelhos que combina

radiação eletromagnética com aquecimento convectivo convencional.

Foram coletadas 75 amostras de café em três (3) níveis de altura. As

amostras passaram pelo processo de secagem tradicional e pelo sistema

eletromecânico, para posteriormente serem avaliadas por provadores

prossionais sob a escala SCAA (Specialty Coffee Association of

America). As amostras secas com infravermelho a 12% de umidade

apresentaram um valor de degustação de 82,93 para xícara de café

com dispersão de dados menor que o sistema tradicional que obteve

81,34, além disso o teste t de amostras não equivalentes indica que

seu valor é signicativamente melhor (p<0,05). Conclui-se que o

sistema eletromecânico com secagem por infravermelho aumentou a

qualidade sensorial do café em relação à secagem tradicional.

Palavras-chave: Aquecimento, degustação, eletromecânico,

organoléptico, SCAA.

Introduction

Worldwide, Peru is a benchmark in specialty coffees, producer

and exporter of organic coffee, with up to 25 % of the United States

market. In fact, its cultivation has become an important axis of the

economic and social engine (Guevara-Sánchez et al., 2019).

According to Pérez-Escalante et al. (2021); Joy Cave. (2020) and

Marquez Romero et al. (2016), coffee it is the livelihood of the highest

percentage of agricultural producing families in the departments

of Junín, San Martín and Amazonas, allowing them a decent living

standard thanks to they receive the payment of a sustainable price

for their cultivation. Coupled with the effect of farmer empowerment

strategies based on fair trade certication (Sirdey and Lallau, 2020).

On the other hand, according to the International Coffee

Organization (2021) after Brazil and Colombia, Peru is the third

largest producer in Latin America with 2.32 % of world production;

however, 85 % of coffee growers are small farmers with 1 to 5 ha of

crops. In this regard, Díaz Vargas and Willems (2017), point out that

small coffee growers have plots without technical or technological

management and only 20 % are associated, affecting the productivity

and homogeneity of the cup quality of specialty coffees. At the same

time, the weak and scattered institutions of the sector mean that

organic coffee is sold as conventional.

It should be noted that Aproselvanor (Asociación de Productores

Selva Nororiental), has 478 associated producers, of which more than

90 % apply the traditional drying method based on sunlight (Devan

et al., 2020; Vijayavenkataraman et al., 2012), which does not

guarantee the physical conditions for the preservation of the optimal

organoleptic characteristics and quality of the coffee bean (Tesfa et

al., 2021), only reaching physical averages of 60 % and 81 points

on the scale (Specialty Coffee Association, 2021). The consequences

are seen in the decrease in production, due to the characteristics of

the grain drying processes, due to loss due to rotting and mold due to

poorly controlled humidity.

Aproselvanor exports coffee containers with organic certication

and fair-trade seal; however, its capacity is limited by the need to

ensure a homogeneous moisture content that ranges between 10 and

12 %, thus avoiding microbiological deterioration, physical damage

and loss of coffee quality that is almost impossible to guarantee with

the traditional method.

A stage of the drying process that needs to be controlled is that

of grain lling, which is affected by the average temperature of the

environment, a parameter that affects the acidity and fruity character

of the drink (Bote and Jan, 2021).

The traditional drying system used by coffee farmers,

documented by Devan et al. (2020) and Vijayavenkataraman et

al. (2012), accompanied by hydrometeorological conditions with

signicant rainfall in the province, prevent standardizing the results

of the process, causing losses due to uncontrolled fermentations when

exposed to humidity and inadequate drying that changes the physical

and sensory quality of the product due to the production of volatile

compounds associated with the undesirable aroma of the grain (Leobet

et al., 2019), having to be classied as conventional coffees with a

low price in the market. According to Zartha Sossa et al. (2021) the

damage in the nutritional and organoleptic characteristics to which

the products are subjected are quite high.

For Aproselvanor, controlling the moisture present in the grains

is a great challenge, how it is stored, the environmental humidity, the

variety of the grain and the size of the particles, determine the humidity

during the drying process, thus guaranteeing the increase in grain shelf

life by reducing moisture and inactivating microorganisms (Meenu et

al., 2017). For this, different drying methods were identied, some

based on heating, infrared and intermittent microwaves (Castellanos

et al., 2018; Kaveh et al., 2021), but the lack of facilities, techniques

and technology for post-harvest activities affects in the quality of the

coffee in the cup obtained (Lao et al., 2019).

Regarding infrared (IR) emitters, there are basically two types

used in the industry, electric IR and gas IR (Pan and Atungulu, 2010).

Electric IRs emit any wavelength from short to long wavelength,

gas IRs emit medium or long wavelength offering advantages (Su

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Guevara-Sánchez et al. Rev. Fac. Agron. (LUZ). 2022, 39(3): e2239363-7 |

et al., 2015). The device combines electromagnetic radiation with

conventional convective heating (Aghbashlo, 2015), considered more

efcient than both techniques separately (Zhang et al., 2019), with

high efciency and potential energy savings (Lao et al., 2019).

The objective of this study was to evaluate the effect of drying by

means of an electromechanical system based on infrared on sensory

quality in the cup for special coffees, for which infrared radiation

was used, which directly heats the product, with little heat loss in the

surrounding air, leading to high energy efciency and reduced drying

time due to high heating rates. In addition, with the convection heated

drying air, the evaporated water is removed in the form of saturated

air, achieving efcient drying.

In this sense, an electromechanical drying system based on far

infrared technology was designed and built, which according to

Chunshan et al. (2016), is a method to save energy and obtain effective

drying, to control the process indicators that include temperature and

relative humidity of the drying environment, time used, resulting

humidity, allowing the standardization and homogenization of the

process.

Materials and methods

Construction of electromechanical drying system with far

infrared (FIR) technology

The prototype was designed, acquiring structural materials,

equipment, accessories with far infrared technology for its assembly,

motors, movement transmission elements and heat transfer elements

such as infrared panels.

Sample Collection

The collection of the coffee bean was carried out in 30 plots of

the provinces of Moyobamba and Rioja, which are at an altitude of

between 850 and 1,600 m.a.s.l. These were grouped and classied

by low zone, middle zone and high zone. Thirty samples of 300 g of

clean green coffee (without defects) dried in the traditional way were

collected: 10 with an average of 12.96 % humidity from the lower

area; 10 with an average of 13.13 % humidity in the middle area and

10 with 14.83 % humidity in the high area. Also included were 45

samples of 300 g of clean green coffee (without defects) dried with

the electromechanical system based on far infrared (IR) technology

with 12 % humidity: 15 samples from the lower area, 15 from the

middle area and 15 from the high area.

The collected samples received in bags with hermetic closures

were subjected to organoleptic analysis (fragrance, avor, residual

taste, acidity, body, uniformity, balance, clean cup, sweetness and

taster score), through tasting sessions, in which forms endorsed by

the SCAA (Specialty Coffee Association of America) were applied,

in order to assess the organoleptic characteristics with scores ranging

between 6 and 10 per attribute (being 6 - 6.75 good, 7 - 7.75 very

good, 8 - 8.75 excellent and 9 - 9.75 extraordinary), resulting in the

average sensory quality classication based on the total score of the

sum of the qualied attributes (less than 80 below specialty quality;

80 - 84.99 very good; 85 - 89.99 excellent; 90 - 100 extraordinary).

The tastings were carried out on homogeneous samples of coffee,

with the same levels of roasting, quantity and conditions.

Coffee cupping procedure

The samples were dried, stacked, without defects, exportable gold

coffee variety were roasted from 8 to 12 minutes, from 63 to 58 on the

Agtron roasting scale in grain and ground, from 8 to 24 hours prior to

cupping. They were stored in a cool, dry and dark place for nine (9)

hours of rest. Subsequently, 10 g of coffee were ground at 70 - 75 %,

15 minutes before infusion with 200 mL of water. The “dry” tasting

was carried out to determine fragrance, smelling and assessing in the

le.

“In a cup”, water at 93 °C was added homogeneously. For

the analysis, the nose is brought closer to the cup and with a deep

inhalation the aromas are transmitted and identied, forming foam or

crust, the taster smells the aroma that he values. After three (3) to ve

(5) minutes of rest, with three gentle movements with a spoon, the

crust was broken, which developed the aromas for evaluation.

For the taste, acidity and body test, the crust was removed and only

coffee with liquid was left at 71 °C. The parameters were determined

by absorbing the coffee with the testing spoon covering the mouth,

tongue and upper palate and spitting out the drink.

The nal analysis was uniformity, sweetness and clean cup.

It was obtained by testing each cup, no more than ve per sample.

The process was based, in the same way, on the absorption and

determination by the sense of taste.

The peculiarities were scored and noted. Tastings with

characteristics that were not favorable to the quality of the product

throughout the process were punished and valued as defects, lowering

the nal evaluation.

Results and discussion

Construction of the electromechanical drying system with far

infrared technology

System design

For the design, AutoCAD was used for the 2D structural

plans, and Autodesk Inventor Professional for the modeling of 3D

views, resulting in the designs shown in gures 1 and 2, in which,

geometrically, a cylindrical shape positioned horizontally whose

rotation it is achieved thanks to a system of driving force multiplied

by gear and pinion transmission.

Rotating cylindrical drying chamber

The cylinder was perforated 1.2 m x 2.4 m, for the coffee beans,

this perforated surface served to transfer far infrared rays and

facilitate vapor evacuation. Technically, the rate of heat transfer is

in equilibrium with the latent heat consumed by evaporation. During

this condition, most of the water evaporates including moisture on

the surface of the product; the rate of heat transfer is greater than

the latent heat consumed by evaporation and the temperature of the

product increases, in this sense, the rate of drying decreases and

is controlled by the rate of diffusion of water on the surface of the

product (Adonis and Khan, 2004).

Preheated air blower or fan and heater unit

They are responsible for heating and injecting the heated air ow

into the rotary dryer, which is distributed by the interior air diffuser

that is attached to the rotary cylinder chamber. The heating system

delivers heat from two infrared burners whose fuel used It was

liqueed petroleum gas (LPG) and coffee husks.

The emitters are distributed on both sides of the drying chamber,

internally and externally, a panel holder and a displacement mechanism

have been conditioned for their handling. They are responsible for the

emission of far infrared waves from the center of the prototype to the

receptors that are the wet coffee beans subjected to drying. In Figure

2 it appears unfolded thanks to the mounting system attached to it.

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4-7 |

Figure 3. Time and temperature used for infrared drying.

Harvest height, cupping and moisture percentage

The results obtained from the cupping according to the Specialty

Coffee Association (2021),

the harvest height and the percentage

of humidity of the samples obtained by the traditional method are

presented in table 1. Thus, on average the samples from the lower

area presented 80.15 in tasting, 814 m.a.s.l. and 12.96 %; in the

middle area, 81.22 in tasting, 1271 m.a.s.l. and 13.13 %; in the

upper area 82.65 in tasting; 1460 m.a.s.l. and 14.83 %, respectively.

The result of the cupping according to the Specialty Coffee

Association (2021), harvest height and moisture percentage

obtained by the infrared-based electromechanical system is shown

in table 2. On average, the samples from the lower area presented

82.05 in cupping, 818.3 m.a.s.l. and 12.96% humidity; in the middle

area they reached 83.05 in tasting and 1,270 m.a.s.l.; in the high

area 83.70 and 1 460 m.a.s.l., respectively. Due to the infrared-

based electromechanical drying system, the samples reached a

relative humidity of 12%.

Analysis of the results of coffee cupping

Based on the data obtained in the organoleptic evaluation forms of

the coffee beans, a comparative descriptive statistical analysis

was carried out (table 3) of the two types of drying.

The descriptive results obtained show better values in the

organoleptic characteristics evaluated for the case of the IR system,

which were like those reported by Guevara-Sánchez et al. (2019),

in which the flavor, fragrance, acidity and body attributes of the

coffee tasted by specialists, made with mechanical drying, obtained

higher values compared to the traditional method, favoring the cup

score with up to 2 % more than performance. Likewise, in the

study carried out by Lao et al. (2019), in which they used the

IR-based electromechanical system, achieved the objective of

producing high-quality food efficiently.

Subsequently, different inferential statistical tests were

carried out (table 4) that allowed the analysis of the results and

gave greater support to the process.

The mean with the traditional method was 81.34, with standard

deviation and mean standard error higher than the mean of 82.93

for the electromechanical system. This indicates that the cupping

value with the electromechanical system is higher and the data is

less dispersed. To validate this statement, the data normality

test was carried out (table 5).

Assembly and installation of the drying prototype and its

components

The joint assembly was carried out for function tests and

calibration, provision of adequate electricity supply to its drives

and emitters of far infrared waves. Knowing the elements that are

part of the electrical circuit, the control system required to carry out

the start-up and start-up of the actuator that is part of the prototype

was designed.

Figure 1. 2D design of the far infrared rotary dryer.

Figure 2. 3D design of the far infrared rotary dryer.

Sensor mounting

For humidity measurement, a microwave sensor was used

whose operating characteristics have been carefully evaluated and

selected. For the temperature measurement of the heated air ow, a

J-type temperature sensor was used. For the loading and unloading

positioning of the equipment, inductive sensors were used.

Drying time

Figure 3 presents the values of the drying speed and temperature

inside the cylindrical chamber used in the IR system, the results of

the middle zone (1271 m.a.s.l.) were used as a reference.

It is observed in gure 3, that the drying time with IR was

approximately 12 hours, reducing the humidity of the coffee bean

from 34.62 to 13.13 %, during the drying process the temperature

of the cylindrical chamber worked in the range from 35.20 to 87.20

°C, likewise, the physical temperature of the coffee beans ranged

between 23.96 °C minimum and 44.62 °C maximum. It should be

considered as the altitude of the collected grain samples increases,

that the incident radiation decreases, so the heat transfer is less,

which affects the increase in the drying time of the coffee beans

(Guevara-Sánchez et al., 2019). Therefore, the statement applies, in

this case, if the height is less, the time used for the drying process

will be less.

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Table 1. Tasting value, harvest height and moisture percentage obtained by the traditional method.

Low area Middle area High area

Sample SCAA Height

Humidity

Sample SCAA Height

Humidity

Sample SCAA Height

Humidity

A-01 80.25 850 12.0 A-11 81.75 1200 13.0 A-21 82.50 1400 14.0

A-02 79.75 900 12.5 A-12 81.50 1250 13.0 A-22 82.50 1430 15.3

A-03 82.00 920 13.5 A-13 81.50 1100 13.8 A-23 82.00 1500 16.0

A-04 81.50 880 14.0 A-14 80.50 1300 14.0 A-24 82.50 1550 13.0

A-05 80.78 780 12.0 A-15 81.25 1350 13.0 A-25 82.75 1600 12.0

A-06 81.00 700 12.0 A-16 81.75 1400 12.5 A-26 83.25 1300 17.0

A-07 80.00 720 12.5 A-17 80.25 1380 12.0 A-27 82.75 1460 13.5

A-08 72.00 800 13.6 A-18 81.75 1250 13.0 A-28 82.25 1600 17.5

A-09 82.25 790 14.0 A-19 80.50 1200 14.0 A-29 82.50 1360 12.0

A-10 82.00 800 13.5 A-20 81.50 1280 13.0 A-30 83.50 1400 18.0

Mean 80.15 814 12.96 Mean 81.22 1271 13.13 Mean 82.65 1460 14.83

Table 2. Tasting value, harvest height and humidity percentage obtained by the infrared-based electromechanical system.

Low area Middle area High area

Sample Taste Height Sample Taste Height Sample Taste Height

SEC-001 82.50 890 SEC-016 82.75 1183 SEC-031 83.00 1443

SEC-002 82.25 890 SEC017 83.50 1183 SEC032 83.50 1443

SEC-003 81.50 890 SEC-018 83.25 1183 SEC-033 83.25 1443

SEC-004 82.00 890 SEC-019 82.50 1183 SEC-034 84.00 1443

SEC-005 82.25 890 SEC-020 83.00 1183 SEC-035 82.50 1443

SEC-006 82.50 787 SEC-021 83.75 1350 SEC-036 83.50 1483

SEC-007 82.50 787 SEC-022 83.25 1350 SEC-037 84.00 1483

SEC-008 82.00 787 SEC-023 82.50 1350 SEC-038 84.20 1483

SEC-009 82.25 787 SEC-024 82.75 1350 SEC-039 83.00 1483

SEC-010 81.00 787 SEC-025 83.25 1350 SEC-040 84.00 1483

SEC-011 82.00 778 SEC-026 83.50 1278 SEC-041 83.75 1455

SEC-012 82.50 778 SEC-027 82.50 1278 SEC-042 84.00 1455

SEC-013 81.75 778 SEC-028 82.50 1278 SEC-043 84.25 1455

SEC-014 81.50 778 SEC-029 83.50 1278 SEC-044 84.50 1455

SEC-015 82.25 778 SEC-030 83.25 1278 SEC-045 84.00 1455

Mean 82.05 818.3 Mean 83.05 1270 Mean 83.70 1460

Note: The humidity percentage obtained with the electromechanical system was 12 %.

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Table 3. Effect of the type of drying on the SCAA value.

Traditional drying Drying with IR technology

Analysis Low Middle High Low Middle High

Fragrance 7.25 7.50 7.50 7.50 7.75 7.75

Taste 7.25 7.50 7.50 7.50 7.75 7.75

Residual taste 7.00 7.00 7.50 7.50 7.50 7.50

Acidity 7.25 7.25 7.50 7.50 7.50 7.75

Body 7.00 7.25 7.50 7.50 7.50 7.75

Uniformity 10.00 10.00 10.00 10.00 10.00 10.00

Balance 7.25 7.50 7.50 7.50 7.50 7.75

clean cup 10.00 10.00 10.00 10.00 10.00 10.00

Sweetness 10.00 10.00 10.00 10.00 10.00 10.00

Taster score 7.00 7.25 7.50 7.25 7.50 7.50

Total score 80.00 81.25 8.5 82.00 83.00 83.75

Table 4. Main statistics of the tasting process by type of drying.

Item drying N Mean Standard deviation Mean standard error

Taste

Traditional 30 81.34 2.01 0.37

Electromechanical

system

45 82.93 0.83 0.12

Table 5. Normality tests.

Item Drying type

Kolmogorov-Smirnova >30 Shapiro-Wilk <= 30

Statistical DF Sig. Statistical DF Sig.

Tasting

Electromecha-

nical

0.14 45 0.02 0.97 45 0.34

Traditional 0.20 30 0.00 0.64 30 0.00

a. Lilliefors signicance correction

The results of the cupping in both treatments presented a normal distribution (tables 4 and 5). The t-test for independent samples was applied

(table 6).

Table 6. Independent samples test.

Levene test for

equality

of variances

t test for equality of means

F Sig. T DF Sig. (bilateral) Mean difference

Standard error

difference

95% CI of the difference

Lower Higher

Tasting

Equal

variances

2.99 0.09 4.74 73 0.00 1.59 0.34 0.92 2.26

Non-equal

variances

4.11 35.70 0.00 1.59 0.39 0.80 2.37

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In tables 4 and 6, it is observed that the cupping value of samples

dried with the IR system was different from the traditional system

(P<0.05), so it is inferred that with the electromechanical prototype a

greater effectiveness in sensory quality of coffee was obtained. Similar

results were reported in different studies, in which the highest cupping

values were obtained through articial drying, using drying tunnels

based on heated air (Tesfa et al., 2021), by far infrared convection

(Chunshan et al., 2016; Lao et al., 2019), and by mechanical drying

(Guevara-Sánchez et al., 2019).

Conclusions

The built electromechanical drying system works safely. The

function tests, temperature and heat transfer tests of the heating unit, as

well as the correct displacement of the external emitters in its bearing

structure were successful. Humidity, temperature and positioning

sensors have been installed by specialists in instrumentation,

connectivity and programming.

The results indicate that the infrared-based electromechanical

system increased the sensory quality of the coffee compared to

traditional drying, since the sensory quality of the beans at the

evaluated altitudes was higher. Likewise, the values of the applied

tasting and statistical tests showed that the sensory quality obtained

is due to the type of drying used that preserves the attributes of the

coffee. Determining that electromechanical drying is an efcient and

effective alternative for the drying processing of coffee beans for the

agricultural sector, which seeks to ensure the appropriate organoleptic

characteristics for the commercialization of specialty coffees.

Acnowledgements

To the Programa Nacional de Desarrollo Tecnológico e Innovación

- ProInnóvate for the nancing of the project "Incremento de la

calidad en taza para cafés especiales con la aplicación y validación de

un sistema electro-mecánico de secado, con tecnología de infrarrojos

lejanos (IR) en Aproselvanor, Provincia Moyobamba - Región San

Martín", Contract No. 293-INNOVATEPERU-PIEC1-2019.

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