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KIMIKA Volume 29, Number 2, pp. 30-35 (2018)
© 2018 Kapisanang Kimika ng Pilipinas
© 2018 Kapisanang Kimika ng Pilipinas（菲律宾卡皮萨南基米卡） All rights reserved. Printed in the Philippines.
保留所有权利。在菲律宾印刷。 ISSN 0115-2130 (Print); 2508-0911 (Online)
ISSN 0115-2130（印刷版）;2508-0911 （在线的） https://doi.org/10.26534/kimika.v29i2.30-35 Effect of Pressure on the Particle Size Distribution of Espresso Coffee Erick Christofer I. Gonzales 1 , Karl Gabriel M. Lloren 1 , Jihan S. Al-shdifat 2 , Lica B. Valdez 3 , Krizzia Rae Gines, Emmanuel V. Garcia 1* 1 Chemistry Department, De La Salle University, Taft Avenue Manila 1004 2 Brownstone Asia-Tech Inc., Mandaluyong City 1552 3 Barista Cofee Academy o f Asia, San Juan City 1503 ABSTRACT Studies regarding particle size distribution, particularly in espressos are surprisingly few. Particle size distribution (PSD) is a plot that displays the average diameter versus percentage volume of the particles present in a sample. With increased awareness amongst cofee drinkers, a study aiming to report the efects of di ferent pressure on particle size distribution o f espresso from four di ferent cofee blends was conducted. Te method involved pulling of espresso shots at 7, 9, and 11 bar (or atm) from di ferent cofee blends labeled as MA, CO, AL, and MO. Laser difraction analysis showed diferent particle size groupings for each set of extraction pressure. Fine particles are within 1.20 to 28.70 µm. Te most abundant particle size is centered at 185.4 µm. Te particle size distribution of co fee blends composed o f 100% Arabica co fee (AL and MO) but sourced from di ferent locations, showed four similar modes or size ranges centered at 3.523, 13.005, 28.70, and 185.4 µm regardless of the extraction pressure or the co fee source. On the other hand, the cofee blends composed o f di ferent ratios o f Arabica and Robusta (MA and CO) showed di ferent modes depending on the pressure. Tis indicates the potential of PSD for characterizing the purity of a cofee blend. Te particle size distribution can also give insights as to the sensory attributes o f the espresso cofee. Keywords: particle size distribution; laser difraction; arabica-robusta blend; espresso; pressure INTRODUCTION Cofee has been among the most traded commodities around the world. Its consumption has been increasing throughout the years with consumers shifting their focus on to favor quality and distinctive sensory attributes (Sunarhanum et al. 铝。, 2014). Since favor is still the most important
, 2014).因为恩惠仍然是最重要的 consumer parameter, cofee drinkers nowadays
消费者参数，当今的咖啡饮用者 increasingly prefer specialty co
越来越喜欢专业公司fee over non-specialty 非专业费用 ones. Specialty cofee is de
的。特色咖啡是 defned by its quality
质量上乘from 从 farm to cup, which has been carefully handled
从农场到杯子，经过精心处理 during harvesting, processing, drying, shipping, and
在收获、加工、干燥、运输和 beverage preparation (SCAA, 2009). Te favor it
饮料制备（SCAA，2009）。Te favor it imparts is found to be unique depending on species,
根据物种的不同，发现赋予是独一无二的， place of origin, climate, agricultural practices, and
原产地、气候、农业实践和 extraction method. (Sunarharum, 2014).
提取方法。（Sunarharum，2014 年）。 Many extractions or brewing methods are available
有许多提取或酿造方法可供选择 in preparing a cup of co
在准备一杯一氧化碳时fee. One o 费。一 of which is with
f 与 the use of an espresso machine. According to
使用浓缩咖啡机。根据 Mestdagh 梅斯特达et al. 等。, (2017), an espresso is a beverage
， （2017）， 浓缩咖啡是一种饮料 that can be prepared from roast and ground co
可以从烤肉和磨碎的一氧化碳中制备fee 费 by means of hot water pressure applied for a short
通过热水施加短时间的压力 period of time, to a compact roast and ground
一段时间后，将烤得紧实，然后磨碎 cofee cake by a percolation machine to obtain a
咖啡蛋糕通过渗滤机获得 *Author to whom correspondence should be addressed; email: emmanuel.garcia@dlsu.edu.ph
*应收信的作者;电子邮件： emmanuel.garcia@dlsu.edu.ph
© 2018 Kapisanang Kimika ng Pilipinas（菲律宾卡皮萨南基米卡） All rights reserved. Printed in the Philippines.
保留所有权利。在菲律宾印刷。 ISSN 0115-2130 (Print); 2508-0911 (Online)
ISSN 0115-2130（印刷版）;2508-0911 （在线的） https://doi.org/10.26534/kimika.v29i2.30-35 Effect of Pressure on the Particle Size Distribution of Espresso Coffee Erick Christofer I. Gonzales 1 , Karl Gabriel M. Lloren 1 , Jihan S. Al-shdifat 2 , Lica B. Valdez 3 , Krizzia Rae Gines, Emmanuel V. Garcia 1* 1 Chemistry Department, De La Salle University, Taft Avenue Manila 1004 2 Brownstone Asia-Tech Inc., Mandaluyong City 1552 3 Barista Cofee Academy o f Asia, San Juan City 1503 ABSTRACT Studies regarding particle size distribution, particularly in espressos are surprisingly few. Particle size distribution (PSD) is a plot that displays the average diameter versus percentage volume of the particles present in a sample. With increased awareness amongst cofee drinkers, a study aiming to report the efects of di ferent pressure on particle size distribution o f espresso from four di ferent cofee blends was conducted. Te method involved pulling of espresso shots at 7, 9, and 11 bar (or atm) from di ferent cofee blends labeled as MA, CO, AL, and MO. Laser difraction analysis showed diferent particle size groupings for each set of extraction pressure. Fine particles are within 1.20 to 28.70 µm. Te most abundant particle size is centered at 185.4 µm. Te particle size distribution of co fee blends composed o f 100% Arabica co fee (AL and MO) but sourced from di ferent locations, showed four similar modes or size ranges centered at 3.523, 13.005, 28.70, and 185.4 µm regardless of the extraction pressure or the co fee source. On the other hand, the cofee blends composed o f di ferent ratios o f Arabica and Robusta (MA and CO) showed di ferent modes depending on the pressure. Tis indicates the potential of PSD for characterizing the purity of a cofee blend. Te particle size distribution can also give insights as to the sensory attributes o f the espresso cofee. Keywords: particle size distribution; laser difraction; arabica-robusta blend; espresso; pressure INTRODUCTION Cofee has been among the most traded commodities around the world. Its consumption has been increasing throughout the years with consumers shifting their focus on to favor quality and distinctive sensory attributes (Sunarhanum et al. 铝。, 2014). Since favor is still the most important
, 2014).因为恩惠仍然是最重要的 consumer parameter, cofee drinkers nowadays
消费者参数，当今的咖啡饮用者 increasingly prefer specialty co
越来越喜欢专业公司fee over non-specialty 非专业费用 ones. Specialty cofee is de
的。特色咖啡是 defned by its quality
质量上乘from 从 farm to cup, which has been carefully handled
从农场到杯子，经过精心处理 during harvesting, processing, drying, shipping, and
在收获、加工、干燥、运输和 beverage preparation (SCAA, 2009). Te favor it
饮料制备（SCAA，2009）。Te favor it imparts is found to be unique depending on species,
根据物种的不同，发现赋予是独一无二的， place of origin, climate, agricultural practices, and
原产地、气候、农业实践和 extraction method. (Sunarharum, 2014).
提取方法。（Sunarharum，2014 年）。 Many extractions or brewing methods are available
有许多提取或酿造方法可供选择 in preparing a cup of co
在准备一杯一氧化碳时fee. One o 费。一 of which is with
f 与 the use of an espresso machine. According to
使用浓缩咖啡机。根据 Mestdagh 梅斯特达et al. 等。, (2017), an espresso is a beverage
， （2017）， 浓缩咖啡是一种饮料 that can be prepared from roast and ground co
可以从烤肉和磨碎的一氧化碳中制备fee 费 by means of hot water pressure applied for a short
通过热水施加短时间的压力 period of time, to a compact roast and ground
一段时间后，将烤得紧实，然后磨碎 cofee cake by a percolation machine to obtain a
咖啡蛋糕通过渗滤机获得 *Author to whom correspondence should be addressed; email: emmanuel.garcia@dlsu.edu.ph
*应收信的作者;电子邮件： emmanuel.garcia@dlsu.edu.ph
Volume 29, Number 2, July 2018 •
第 29 卷第 2 期， 2018 年 7 月 •KIMIKA 喜米卡 Efect o f Pressure on the Particle Size Distribution of Espresso Co
f 对浓缩咖啡颗粒分布的压力fee 费31 small concentrated foamy cup. Te key parameters
小浓缩泡沫杯。关键参数 identifed 已识别for this preparation method are, water to
对于这种制备方法，水以 cofee ratio, particle size, compaction, pressure, and
配fee ratio、粒径、压实度、压力和 brewing time. Among these, the extraction pressure
冲泡时间。其中，提取压力 has the main infuence on the acquired favor
对获得的青睐有主要影响 profle o 教授f an espresso because it is also a dependent
f 浓缩咖啡，因为它也是一个依赖 variable with respect to the permeability of co
与一氧化碳的磁导率有关的变化fee 费 beds (Corrochano, 2015). A research conducted by
床（Corrochano，2015）。一项研究 Andueza 安杜埃萨et al. 等。, (2002) concentrated on the efect
， （2002） 集中于 efect of water pressure in the physicochemical, sensory
水压在理化、感觉 characteristics, and essential odorants of Arabica
阿拉比卡咖啡的特性和必需气味 espresso. However scientifc studies are still lacking
浓咖啡。然而，仍然缺乏科学研究 to substantiate seeming impact of such key variables
证实这些关键变量的看似影响 on cup quality. 关于杯子质量。 Te grinding process of roasted co
焙烧的研磨工艺fee beans are related
费用豆是相关的 to a particular brewing method in that an average
对于特定的酿造方法，平均 grind size is deemed appropriate for each method. In
研磨尺寸被认为适合每种方法。在 the preparation of espresso, a certain amount of
浓缩咖啡的制备，一定量fne FNE的 particles (< 100 µm) are needed for pressure build-
压力建立需要颗粒 （< 100 μm） up. Tese directly afect both permeability and
向上。Tese 直接影响渗透率和fow 福 of water (i.e. low permeability of co
（即一氧化碳的低渗透性fee bed results 收费床结果 to higher extraction pressures, low total fow rate, and longer extraction times, thus leading to over- extraction and change in taste). For this reason, studies were done regarding the ground cofee beans, relating its particle size distribution on favor release (Malvern, 2012), along with investigating the efects o f various brewing techniques and particle size of ground co fee on sensory pro fling (Fibrianto et al. , 2018). We surmised that pressure during cofee processing can in fuence the bean fracturing dynamics, and therefore the fnal size distribution. However, a cursory survey of the literature reveals very limited reports focusing on the particle size distribution in espressos, hence this study. In line with the rising demand for high-quality co fee alongside increased consumer awareness amongst cofee drinkers (Per fect Daily Grind, 2017), the aim of this work is to investigate the e fects o f various pressures: 7, 9, and 11 bar (or atm) in the particle size distribution of espresso obtained from four diferent cofee blends by means o f laser di fraction analysis. METHODOLOGY Materials and Reagents. Te grinding of co fee beans were carried out using a Rancilio Kyro 65 OD. Te holder of the ground co fee was a ridged VST Inc. precision flter basket (58 mm in diameter, 20-22g nominal capacity, and 30 mm height). Extraction process using an espresso machine, commonly termed as pulling, was done using the Milano Italy Bezzera Arcadia Display. Plastic containers for biological samples were used to contain the espresso samples. To prevent further dissolution of co fee particles, the sample containers were placed in an ice-flled chiller during the brie f transport to the laboratory. Te samples were then analyzed using the Beckmann Coulter LS 13 320 Laser Difraction Particle Size Analyzer equipped with Universal Liquid Module using a 1.5mL liquid dropper. Distilled water was used for the rinsing and suspension of sample in the liquid module of the instrument. Collection of Samples. Two cofee species are used in this study: Cofea canephora (Robusta) and Cofea arabica (Arabica). Four commercial variants of the co fee beans having diferent compositions and origins were used for the preparation the espresso shots. Cofee blend MA is 60% Arabica and 40% Robusta in medium-dark roast. Cofee blend CO is 20% Arabica and 80% Robusta in medium dark roast. Cofee blend-AL is 100% Arabica from Ethiopia, and Co fee blend MO is also 100% Arabica but sourced from di ferent regions in Central America. Both AL and MO blends were roasted at a light level. Twenty (20) grams of co fee grounds were collected per extraction. Te ground cofee samples were then compacted in a porta flter – a component o f the espresso machine that holds the ground cofee prior to and during the brewing process, and using an accessory used for compression called a tamper. Afterwards, espresso shots were pulled at various pressures of 7, 9, and 11 bar (or atm). Extraction temperature was fxed at 95±1ºC and weight of cofee grounds were set at 35 g per shot. Samples were immediately transferred to plastic containers and refrigerated. All extracted samples were prepared by a seasoned barista at the Barista and Cofee of Asia Association (BCAA). Particle Size Distribution Analysis. Vigorous swirling of the sample was done prior to the particle size analysis, to ensure homogeneity in aqueous solution. Samples were placed in the sample holder with a use of a dropper. Te following parameters were set on the LS 13 320 Laser Difraction Particle Size Analyzer: auto-rinsing for 15 seconds, de- bubbling for 142 seconds, measuring ofset for 60 seconds, aligning for 30 seconds, and measuring background for 60 seconds. Modes or peaks are the particle sizes that pinpoint a large abundance in a sample. Calibration of the Instrument. Glass beads with a known particle sizes and distribution were analyzed before and after the series of analyses. Te data was then compared with the accepted value prescribed by the instrument. Te standard procedure in calibrating the instrument was used in running the samples so as to avoid any diferences in the results basing from the parameters set.
第 29 卷第 2 期， 2018 年 7 月 •KIMIKA 喜米卡 Efect o f Pressure on the Particle Size Distribution of Espresso Co
f 对浓缩咖啡颗粒分布的压力fee 费31 small concentrated foamy cup. Te key parameters
小浓缩泡沫杯。关键参数 identifed 已识别for this preparation method are, water to
对于这种制备方法，水以 cofee ratio, particle size, compaction, pressure, and
配fee ratio、粒径、压实度、压力和 brewing time. Among these, the extraction pressure
冲泡时间。其中，提取压力 has the main infuence on the acquired favor
对获得的青睐有主要影响 profle o 教授f an espresso because it is also a dependent
f 浓缩咖啡，因为它也是一个依赖 variable with respect to the permeability of co
与一氧化碳的磁导率有关的变化fee 费 beds (Corrochano, 2015). A research conducted by
床（Corrochano，2015）。一项研究 Andueza 安杜埃萨et al. 等。, (2002) concentrated on the efect
， （2002） 集中于 efect of water pressure in the physicochemical, sensory
水压在理化、感觉 characteristics, and essential odorants of Arabica
阿拉比卡咖啡的特性和必需气味 espresso. However scientifc studies are still lacking
浓咖啡。然而，仍然缺乏科学研究 to substantiate seeming impact of such key variables
证实这些关键变量的看似影响 on cup quality. 关于杯子质量。 Te grinding process of roasted co
焙烧的研磨工艺fee beans are related
费用豆是相关的 to a particular brewing method in that an average
对于特定的酿造方法，平均 grind size is deemed appropriate for each method. In
研磨尺寸被认为适合每种方法。在 the preparation of espresso, a certain amount of
浓缩咖啡的制备，一定量fne FNE的 particles (< 100 µm) are needed for pressure build-
压力建立需要颗粒 （< 100 μm） up. Tese directly afect both permeability and
向上。Tese 直接影响渗透率和fow 福 of water (i.e. low permeability of co
（即一氧化碳的低渗透性fee bed results 收费床结果 to higher extraction pressures, low total fow rate, and longer extraction times, thus leading to over- extraction and change in taste). For this reason, studies were done regarding the ground cofee beans, relating its particle size distribution on favor release (Malvern, 2012), along with investigating the efects o f various brewing techniques and particle size of ground co fee on sensory pro fling (Fibrianto et al. , 2018). We surmised that pressure during cofee processing can in fuence the bean fracturing dynamics, and therefore the fnal size distribution. However, a cursory survey of the literature reveals very limited reports focusing on the particle size distribution in espressos, hence this study. In line with the rising demand for high-quality co fee alongside increased consumer awareness amongst cofee drinkers (Per fect Daily Grind, 2017), the aim of this work is to investigate the e fects o f various pressures: 7, 9, and 11 bar (or atm) in the particle size distribution of espresso obtained from four diferent cofee blends by means o f laser di fraction analysis. METHODOLOGY Materials and Reagents. Te grinding of co fee beans were carried out using a Rancilio Kyro 65 OD. Te holder of the ground co fee was a ridged VST Inc. precision flter basket (58 mm in diameter, 20-22g nominal capacity, and 30 mm height). Extraction process using an espresso machine, commonly termed as pulling, was done using the Milano Italy Bezzera Arcadia Display. Plastic containers for biological samples were used to contain the espresso samples. To prevent further dissolution of co fee particles, the sample containers were placed in an ice-flled chiller during the brie f transport to the laboratory. Te samples were then analyzed using the Beckmann Coulter LS 13 320 Laser Difraction Particle Size Analyzer equipped with Universal Liquid Module using a 1.5mL liquid dropper. Distilled water was used for the rinsing and suspension of sample in the liquid module of the instrument. Collection of Samples. Two cofee species are used in this study: Cofea canephora (Robusta) and Cofea arabica (Arabica). Four commercial variants of the co fee beans having diferent compositions and origins were used for the preparation the espresso shots. Cofee blend MA is 60% Arabica and 40% Robusta in medium-dark roast. Cofee blend CO is 20% Arabica and 80% Robusta in medium dark roast. Cofee blend-AL is 100% Arabica from Ethiopia, and Co fee blend MO is also 100% Arabica but sourced from di ferent regions in Central America. Both AL and MO blends were roasted at a light level. Twenty (20) grams of co fee grounds were collected per extraction. Te ground cofee samples were then compacted in a porta flter – a component o f the espresso machine that holds the ground cofee prior to and during the brewing process, and using an accessory used for compression called a tamper. Afterwards, espresso shots were pulled at various pressures of 7, 9, and 11 bar (or atm). Extraction temperature was fxed at 95±1ºC and weight of cofee grounds were set at 35 g per shot. Samples were immediately transferred to plastic containers and refrigerated. All extracted samples were prepared by a seasoned barista at the Barista and Cofee of Asia Association (BCAA). Particle Size Distribution Analysis. Vigorous swirling of the sample was done prior to the particle size analysis, to ensure homogeneity in aqueous solution. Samples were placed in the sample holder with a use of a dropper. Te following parameters were set on the LS 13 320 Laser Difraction Particle Size Analyzer: auto-rinsing for 15 seconds, de- bubbling for 142 seconds, measuring ofset for 60 seconds, aligning for 30 seconds, and measuring background for 60 seconds. Modes or peaks are the particle sizes that pinpoint a large abundance in a sample. Calibration of the Instrument. Glass beads with a known particle sizes and distribution were analyzed before and after the series of analyses. Te data was then compared with the accepted value prescribed by the instrument. Te standard procedure in calibrating the instrument was used in running the samples so as to avoid any diferences in the results basing from the parameters set.