Impact of initial sensory quality of specialty natural coffee during storage

Abstract

The objective of this study was to chemically and sensorially evaluate dryprocessed coffees with an initial quality of 82 and 84 points on the SCA (Specialty Coffee Association) scale, packaged in impermeable and permeable materials, and stored at room temperature and in a refrigerated environment for 9 months. The sensory and chemical quality of the stored beans was evaluated at the beginning of storage, as well as after six and nine months. The results show that specialty natural coffees with a higher initial sensory score experience attenuation of sweetness, acidity, body, and aftertaste over 9 months of storage, with stability in the overall score and sensory descriptors, particularly when stored in high-barrier packaging. Chemically, the changes observed during storage differ depending on the initial sensory quality of the specialty natural coffees, with greater preservation of volatile compounds and fatty acids when high-barrier packaging is used, regardless of storage temperature. It is concluded that, in addition to packaging and storage conditions, the initial attributes of natural coffee are a determining factor for quality after 9 months of storage. Chemical changes during storage vary according to the initial sensory quality of specialty natural coffees.

Key words
refrigerated storage; high-barrier packaging; jute packaging; volatile compound profile; fatty acid profile

INTRODUCTION

Coffee is one of the most important products in Brazilian agribusiness. The complexity of coffee’s qualitative attributes begins in the field and depends on crop formation, variety selection, harvesting, and post-harvest processes, and continues through storage and transportation. The sensory notes in specialty coffee reflect the final expression of a complex chain of physical and chemical transformations linking the beans to the cup (Machado et al. 2022). However, the extent of these transformations depends on the hygiene conditions, temperature, and air composition in which the beans are stored.

The purpose of storing coffee beans is to preserve them for a specific period, ensuring the retention of their physical, chemical, biochemical, and sensory properties. Changes that occur during storage are more pronounced in specialty coffees stored in jute bags compared to losses observed in commodity coffees (Borém et al. 2013, 2019a, Ribeiro et al. 2011, Vargas et al. 2018). Additionally, dry-processed coffees are more sensitive during storage, with a more pronounced quality deterioration than wet-processed coffees (Borém et al. 2019b). Thus, research has been conducted to ensure the preservation of desirable sensory attributes throughout storage (Abreu et al. 2017, 2019, Borém et al. 2013, 2019a, b, 2021, 2023a, b, Ribeiro et al. 2011). In this context, it has been found that using plastic packaging impermeable to water vapor and gases, both during storage and export, reduces the beans’ respiratory activity, helping preserve green coffee bean quality (Borém et al. 2019b). High-barrier packaging is used for specialty coffees, as they have greater added value. This technology can slow down the deterioration of beverage quality precursors, maintaining the initial characteristics for longer (Zarebska et al. 2022, Borém et al. 2013, 2019b, Ribeiro et al. 2011).

Maintaining coffee freshness is essential to preserving flavor. During improper storage, there is a decline in chemical compounds, weakening cup quality (Zarebska et al. 2022) and, consequently, affecting specialty coffee commercialization (Borém et al. 2021). A high-temperature and high-humidity environment accelerates the beans’ metabolic process. Thus, using a refrigerated atmosphere to control physical and chemical changes is a favorable technique, regardless of the processing method (Abreu et al. 2017). Despite advances in the literature on high-barrier packaging and refrigerated storage practices, no packaging fully preserves the initial quality of the beans (Borém et al. 2013, 2019a, Ribeiro et al. 2011). Additionally, no studies in the literature report on the sensory and chemical behavior of coffees with varying initial sensory qualities during storage. Considering the above, the objective of this study was to chemically and sensorially evaluate dry-processed coffees with initial scores of 82 and 84 points on the SCA (Specialty Coffee Association) scale, packaged in impermeable and permeable materials, and stored at room temperature and in a refrigerated environment for 9 months.

MATERIALS AND METHODS

Characterization of the Experiment

The specialty coffees (Coffea arabica L.) were obtained from commercial lots provided by Syngenta - NuCoffee. These natural coffee lots were initially sampled and classified as beverages with scores of 82 and 84 points according to the Specialty Coffee Association (SCA) scale. The coffee beans were stored in two types of packaging: one permeable to moisture and gases, and a second type with a high barrier to gases, moisture, and light. The packages used had a capacity of 10 kg.

The experiment was arranged in a completely randomized design (CRD), with three replications, following a 2 x 2 x 2 factorial scheme (two coffee qualities [82 and 84 points on the SCA scale], two storage environments [ambient and refrigerated], and two types of packaging [jute and high-barrier packaging]). The effects of the treatments were observed over nine months, with samples collected at 0, 6, and 9 months.

The beans were stored at room temperature, without temperature control, and in a refrigerated environment, at the Armazém Logístico Integrado de Varginha, Minas Gerais. To control for external effects, a stacking setup was used for each sampling period (0, 6, and 9 months), with proper spacing between stacks, composed of seventy 60 kg bags of coffee forming a border, and experimental samples placed in the center of the stacks for both storage conditions. The stacks were set up inside two Cococon Lite 005 containers, one refrigerated and the other at room temperature.

Refrigeration was achieved using an artificial aerator from Coolseed, which kept the grain mass temperature between 15 and 18 °C. Daily temperature and relative humidity readings of the ambient air were recorded with thermohygrographs placed in the experimental area.

Sensory Analysis

Sensory analysis was conducted by CQI (Coffee Quality Institute) certified judges, known as Q-graders. The samples were prepared according to the SCA protocol, with a light roast for coffee beans sized 16 and above, monitoring the temperature so that roasting lasted between 8 and 12 minutes. All samples were roasted within 24 hours prior to cupping, with a minimum rest of 8 hours. Five representative cups of each sample were evaluated, with a concentration of 8.25 g of coffee in 150 mL of water, adapted from the SCA protocol. The beans were ground to achieve 70% to 75% of particles passing through a 20-mesh sieve. To standardize roasting and help judges recall sensory notes across storage periods, roasted coffee samples from the first evaluation were stored at -80 °C to minimize aroma and flavor changes. The evaluation form listed sensory characteristics for aroma, flavor, acidity, and body, applying the Check All That Apply (CATA) technique (Salvio et al. 2023). Additionally, an intensity scale from 0 to 10 was used to evaluate sweetness, acidity, body, astringency, past crop, and aftertaste attributes. Finally, Q-graders provided an overall impression score, allowing for a sensory description, intensity rating of attributes, and a score for each sample.

Volatile Compound Profile

Chromatographic analyses were conducted at the experiment’s conclusion to assess volatile compounds in the roasted beans. Samples from each storage period were roasted and stored in a deep freezer (-80 °C). The roasted beans were ground for about 1 minute in an 11A basic grinder (IKA, Brazil), using liquid nitrogen to aid grinding and prevent oxidation. After grinding, 2 g of each sample was placed in hermetic vials. Volatile compounds were extracted using a gas chromatograph (GC) with mass spectrometer (MS) detection, following Rabelo et al. (2021). The GC–MS model QP − 2010 SE (Shimadzu) was equipped with an NST-100 column (30 m × 0.25 mm × 0.25 μm) with a polyethylene glycol phase similar to a Carbowax® column. The samples were equilibrated in the equipment for 30 minutes at 70 °C. The volatile phase was injected into the GC with subsequent detection by the MS, and the injector temperature was set to 220 °C. Helium was used as the carrier gas at a flow rate of 1 mL·min−1. Oven heating was programmed as follows: maintained at 25 °C for 6 min, then increased to 70 °C at 10 °C·min−1, to 95 °C at 5 °C·min−1, to 115 °C at 10 °C·min−1, to 170 °C at 5 °C·min−1, and finally to 215 °C at 40 °C·min−1. The total chromatographic run time was 35 min. Data analysis and compound identification were performed using GCMS Solution software (version 4.4, Shimadzu Corporation, Japan) and the NIST/EPA/NIH 2014 database. Each compound was identified by comparing MS spectra with database data, with results expressed as relative percentage area, representing each identified compound’s peak area relative to the total chromatogram area.

Fatty Acid Profile

The fatty acid profile was determined by gas chromatography (GC) following Borém et al. (2023b). Fatty acids were analyzed with a Shimadzu GC2010 gas chromatograph with a flame ionization detector, using an SP-2560 column (Supelco) of 100 m × 0.25 mm. The temperature gradient was set as follows: 140 °C for 5 min, increasing at 4 °C·min−1 to 240 °C, held for 30 min; injector (1/20 split) at 240 °C; and detector at 240 °C. Helium served as the carrier gas (2 mL·min−1) with an injection volume of 2 μL. Fatty acid peaks were identified by comparing them with Supelco37 methylated fatty acid standards, with the final content expressed as a relative percentage of the total area.

Organic Acid Profile

Green coffee beans were ground in an 11A basic grinder for about 1 min, with the addition of liquid nitrogen to prevent oxidation. The determination of organic acids was performed by High-Performance Liquid Chromatography (HPLC) based on the methodology described by Borém et al. (2023b). These compounds were determined using 10 mM perchloric acid at a constant flow rate of 0.6 mL·min⁻¹ as the mobile phase, and the chromatography column used was C610H at 40 °C, monitored by UV spectrophotometry at 210 nm. Standard solutions of citric, malic, tartaric, succinic, lactic, quinic, and acetic acids were used to identify the chromatogram peaks, compare their retention times, and calculate their concentrations in the samples. The final levels of organic acids were expressed as the percentage of dry matter (% w/w).

Bioactive Compounds

The non-volatile compounds, such as caffeine, trigonelline, and chlorogenic acid, were determined by High-Performance Liquid Chromatography (HPLC) following the methodology described by Borém et al. (2023b). The bioactive compounds from samples of 0.5 g of ground green coffee (prepared in a basic 11A grinder for about 1 min, with the addition of liquid nitrogen) were extracted in 50 mL of boiling distilled water and placed in a water bath with boiling water for 3 min. The extract was filtered through common filter paper and then through a 0.45 μm membrane. The determination of these compounds was performed in a liquid chromatograph (Shimadzu) with a diode array detection system (model SPD-M10A), using a Discovery C18 chromatographic column (250 x 4.6 mm, 5 μm) and a wavelength of 272 nm. The mobile phase consisted of methanol:water: acetic acid (20:80:1) with a flow rate of 1 mL·min⁻¹. A calibration curve was prepared for identification and quantitative analysis using standards of caffeine, trigonelline, and 5-caffeolquinic acid (5-CQA).

Statistical Analysis

Sensory Analysis

The attribute intensity results and the final score were evaluated by analysis of variance (ANOVA) using SISVAR software, version 5.3 (Ferreira 2011). When significant differences were found in the F test, the Scott-Knott test was applied. To better understand the relationship of the treatments with sensory attributes, principal component analysis (PCA) was performed using Chemoface statistical software, version 1.4 (Nunes et al. 2012). The results obtained through the descriptor frequencies for the attributes of aroma, flavor, acidity, and body were analyzed using Multiple Factor Analysis (MFA); only the descriptors with a frequency higher than 20% were used (Salvio et al. 2023). The analyses were performed using R software version 4.1.0 (R Development Core Team 2021).

Chemical Analysis

Principal component analysis (PCA) was performed on the relative areas and concentrations of the chemical compounds found using CHEMOFACE 1.64 statistical software (Nunes et al. 2012).

RESULTS AND DISCUSSION

Principal component analysis (PCA) was performed to evaluate the intensity of the sensory attributes and the final sensory score of the coffees. In addition, multiple factor analysis (MFA) was performed to identify the descriptors of the sensory attributes of aroma, flavor, acidity, and body. The principal component analysis is shown in Figure 1. The vectors with the largest dimensions are final score and astringency, which had the greatest effect on the vertical distribution of the treatments, followed by the vectors of body and sweetness, which had the greatest influence on the horizontal distribution.

Figure 1
Principal Component Analysis (PCA) of sensory attribute intensities (sweetness, acidity, body, aftertaste, astringency, past crop) and final scores of coffee beans with different initial quality levels, processed by dry method and stored under varied conditions. Legend: A = ambient storage; R = refrigerated storage; 82 = initial score of 82 points on the SCA scale; 84 = initial score of 84 points on the SCA scale; HB = high-barrier packaging (impermeable); J = jute packaging (permeable); 0m = 0 months of storage; 6m = 6 months of storage; 9m = 9 months of storage.

It can also be observed that the vectors of the positive attributes - sweetness, body, acidity, and aftertaste - are opposite to the vector of the past crop in the graph, indicating that greater intensity of the past crop implies a lower intensity of sweetness, acidity, body, and aftertaste. In other words, the increase in the perception of the past crop means a decrease in the positive attributes of the coffee.

It is possible to see the formation of six distinct groups. Group I is formed by coffees with 82 points at the beginning of storage, which present high intensities of the attributes body, sweetness, and astringency. Group II is formed by coffees with a quality of 84 points at the beginning of storage and presents a high body, sweetness, and, mainly, a high aftertaste and acidity. Thus, the presence of sensory astringency in the 82-point coffee differentiated it from the quality of the 84-point coffee, which initially presented high intensities of the positive attributes of body, sweetness, aftertaste, and acidity. Group III consists of coffees stored for 6 months from the samples at room temperature in jute packaging with an initial quality of 82 and 84 points (A82J 6m and A84J 6m). In addition, there are coffees with refrigerated storage with an initial quality of 82 points and impermeable and permeable packaging (R82HB 6m and R82J 6m). This was characterized by the high intensity of the past crop. Group IV consists of coffees with an initial quality of 82 points stored for nine months in permeable packaging, regardless of the storage environment (A82J 9m and R82J 9m); this group presented high intensity of astringency and past crop. Group V is formed by coffees with an initial quality of 82 points, stored for nine months in high-barrier packaging, regardless of the storage temperature (A82HB 9m and R82HB 9m). Also included are coffees with an initial quality of 84 points, stored for nine months in ambient conditions and jute packaging (A84J 9m). This group also presented high intensity from the past crop; however, it presented a higher final score than Group III and especially Group IV.

Therefore, it can be seen that storing coffees with an initial quality of 82 points in high-barrier packaging favors the preservation of the sensory note compared to jute packaging, regardless of the conditions (temperature and relative humidity) of the storage environment. Furthermore, it can also be inferred that storing coffee with an initial quality of 84 points for 6 and 9 months in ambient conditions and jute packaging reduces the quality of the coffee, since this coffee sample resembles coffees stored in high-barrier packaging with an initial quality of 82 points.

Finally, Group VI is formed by coffee with an initial quality of 82 points stored at room temperature with impermeable packaging for six months (A82HB 6m). Coffees with an initial quality of 84 points stored in high-barrier conditions for 6 and 9 months, regardless of the storage temperature (A84HB 6m, A84HB 9m, R84HB 6m, and R84HB 9m). In addition, coffee with 84 points stored for 6 and 9 months in jute packaging in a refrigerated environment (R84J 6m, and R84J 9m). This group showed a greater relationship with the score vector than the others. Thus, for coffees with an initial quality of 84 points, the use of high-barrier packaging, or the use of permeable packaging associated with refrigeration in storage, preserves the quality of specialty natural coffees for up to nine months. It is also worth noting that coffees with an initial quality of 82 points, stored in high-barrier packaging under ambient conditions, presented better sensory characteristics after 6 and 9 months of storage. Thus, coffees with an initial score of 84 have a high relationship with the score vector and a lower relationship with the past crop vector. Coffees with an initial score of 82 have a high relationship with the past crop and astringency vectors, which is consequently evidenced by a lower relationship with the score vector. These groupings reveal that, regardless of the packaging used, this perception is intensified for coffees stored with initial scores of 82. Furthermore, they show that for a storage period of 9 months, samples with a lower initial score and jute packaging have greater astringency than those stored in high-barrier packaging, regardless of whether the environment is refrigerated or not. Packaging that is impermeable to gases, light, and water vapor preserves higher sensory scores and reduces the perception of a past crop of the coffee beverage.

The modification of the sensory profile of coffee during storage is the result of chemical and biochemical changes resulting from the metabolic activity of the bean. These can affect the flavor complexity, the intensity of the body and acidity of the beverage, and mainly, the presence of notes of paper, cardboard, straw, or “past crop” that were not there at the beginning of storage (Borém et al. 2021). All treatments in this study showed a decrease in the intensity of the positive attributes of sweetness, acidity, aftertaste, and body after storage. However, coffee samples with a higher initial score were more resistant to loss of final score without presenting astringency.

In addition to this analysis of attribute intensity, the descriptors of aroma, flavor, acidity, and body are presented below in the form of graphs obtained through multiple factor analysis (MFA). The results are presented in three graphs. The first, the group inertia graph, shows the differentiation in the description of the attributes according to the storage time (0, 6, and 9)

The location of the centroid is an indicator of the similarity or difference between the sensory descriptors. If the centroids are positioned in the same quadrant, it means that the descriptors are similar; whereas if they are in different quadrants, the descriptors are different. Furthermore, the magnitude and direction of the vectors show how the storage time affects the sensory description of each treatment. When the vectors are in opposite directions, they indicate that there is differentiation between the descriptors according to time. Likewise, the larger the dimensions of the vector, the greater the differentiation in the description or frequency of the attribute descriptor.

The third graph is the correlation circle, which indicates the main sensory descriptors for each treatment. To do this, a link is established between the location of the centroids of each treatment and the vectors corresponding to the storage times in the correspondence graph. The vectors corresponding to the aroma descriptors for each time are presented in the correlation circle. This process allows the sensory descriptors for each treatment to be obtained.

Figure 2 presents the results of the multifactorial analysis for aroma descriptors of coffee beverages from dry-processed beans with initial scores of 82 and 84 on the SCA scale, stored at room temperature (a, b, c) and in a refrigerated system (d, e, f), and in different packaging (high barrier – impermeable; and jute – permeable).

Figure 2
Multiple factor analysis of aroma descriptors in coffee beverages from beans with different initial quality levels, dry-processed and stored under ambient (a, b, c) and refrigerated (d, e, f) conditions, in different packaging types. Legend: A = ambient storage; R = refrigerated storage; 82 = initial score of 82 points on the SCA scale; 84 = initial score of 84 points on the SCA scale; HB = high-barrier packaging (impermeable); J = jute packaging (permeable); 0m = 0 months of storage; 6m = 6 months of storage; 9m = 9 months of storage. Attributes: FR = fruity; SW = sweet; CH = chocolate; NU = nuts; DE = defects.

The aroma descriptors were modified over time (Figures 2a and 2d), mainly for coffees stored at room temperature, due to the greater distances from the centroids (Figure 2a). Storage time affected the aroma descriptors in all treatments, regardless of the storage temperature, which is shown in the graphs by the opposition of the vectors in all centroids (Figures 2b and 2e). Furthermore, it is possible to perceive a greater influence of the initial quality of the coffees than of the storage packaging.

At the beginning of storage, the predominant aromas of the beverages from coffee beans with an initial score of 84 points, regardless of the packaging and storage conditions, were sweet, floral, and fruity (Figures 2c and 2f). After 6 and 9 months of storage, the description of the aroma presented modifications according to the packaging and the storage environment of the beans.

For ambient conditions (Figure 2c), the coffee that initially (0 months of storage) presented a sweet, floral, and fruity aroma, after 6 months of storage in a high barrier was described as chocolate and fruity, and after 9 months as floral and chocolate. For the coffee that initially presented a quality of 84 points stored in jute, after 6 months it exhibited a floral, sweet, and nutty aroma, and after 9 months of storage, it presented a description of fruity and sweet.

In refrigerated storage with high-barrier packaging, after 6 months of storage, the aroma was described as sweet and floral, and after 9 months as floral, fruity, and sweet. Thus, it is observed that refrigerated storage with high-barrier packaging of the beans preserved the quality of the aroma of the coffees initially stored with 84 points. However, the jute packaging presented modifications in the aroma, and after 6 and 9 months of storage, it included descriptors indicating defects.

For coffees with an initial score of 82 points, the aroma descriptors at the beginning of storage (0 months) were chocolate and nutty, regardless of the environment (Figures 2c and 2f). After 6 and 9 months of storage with high-barrier packaging and a refrigerated environment (Figure 2f), this coffee presented descriptions of sweetness, floral, and fruity. Similarly, in storage at room temperature, after 6 months in impermeable packaging, the aroma was described as floral and sweet, and after 9 months as fruity and sweet.

For coffees with an initial quality of 82 points stored in jute packaging at room temperature, after 6 months they presented a defective aroma, and after 9 months they exhibited a nutty aroma. When stored in a refrigerated environment, they were described as having a nutty aroma and a defect after 6 and 9 months of storage. It is noted that the packaging had a greater effect on the quality of the coffee beans, which initially had 82 points, than the storage environment. In this case, the high-barrier packaging provided floral, fruity, and sweet aromas to the coffee, while the jute packaging resulted in nutty and defective aromas.

Figure 3 presents the results of the multifactorial analysis for flavor descriptors of the coffee beverage from dry-processed beans with initial scores of 82 and 84 on the SCA scale, stored at room temperature (a, b, c) and in a refrigerated system (d, e, f), and in different packaging (high barrier – impermeable; and jute – permeable).

Figure 3
Multiple factor analysis of flavor descriptors in coffee beverages from beans with different initial quality levels, dry-processed and stored under ambient (a, b, c) and refrigerated (d, e, f) conditions, in different packaging types. Legend: A = ambient storage; R = refrigerated storage; 82 = initial score of 82 points on the SCA scale; 84 = initial score of 84 points on the SCA scale; HB = high-barrier packaging (impermeable); J = jute packaging (permeable); 0m = 0 months of storage; 6m = 6 months of storage; 9m = 9 months of storage. Attributes: FR = fruity; SW = sweet; CH = chocolate; NU = nuts; DE = defects.

For the flavor attribute, there is a noticeable influence of the environment on the differentiation of the stored coffees, with a greater distance between the centroids in the coffee stored in a refrigerated environment (Figures 3a and 3d). In the room temperature condition, each treatment occupies a different quadrant (Figure 3b), indicating differentiation in the flavor descriptions according to the storage conditions of the green coffee beans and the initial sensory scores. However, for refrigerated storage (Figure 3e), the centroids of the samples with an initial quality of 82 points are located in the same quadrant, indicating similarity in the flavor descriptions, regardless of the storage packaging. Furthermore, it is evident that the vectors related to storage times (0, 6, and 9 months) are distinct for all treatments, indicating the influence of the storage period on the flavor descriptors. The classes of flavor descriptors for coffee beverages are similar to those of aroma descriptors (Figures 3c and 3f).

Similarly to the aroma descriptors, the flavor descriptions of coffees with an initial score of 84 points, at the beginning of storage (0 months), were sweet, floral, and fruity. Likewise, the flavor descriptors of coffees with an initial score of 82 points were chocolate, nutty, and defective, regardless of the environment and packaging, for 0 months of storage.

In the ambient condition (Figure 3c), the coffees that initially had a quality of 82 points, regardless of the storage packaging, exhibited a flavor with a defect description after 6 and 9 months of storage. In contrast, the coffees with 84 points at the beginning of storage displayed variations in their descriptors according to the environment, packaging, and storage time.

The flavor that was initially described as sweet, floral, and fruity, after 6 months of storage in high-barrier conditions at room temperature, was noted as sweet, and after 9 months, as sweet, nutty, and chocolate. For jute packaging at room temperature, the flavor of coffee stored for 6 months was described as fruity, nutty, and chocolate; after 9 months, it was described as sweet, nutty, and chocolate.

For refrigerated conditions, coffee with an initial quality of 84 points, after 6 months of storage in high-barrier packaging, was described as nutty and fruity; and after 9 months as chocolate, fruity, sweet, and floral. For jute packaging under the same storage conditions, at 6 months, the flavor was described as chocolate and defective, while after 9 months of storage, the defective flavor prevailed. Błaszkiewicz et al. (2023), studying the effect of storage conditions on the quality parameters of green and roasted coffee, observed that coffees stored in GrainPro® packaging at a temperature of 10 °C for up to 9 months maintained good tasting scores. The coffee with an initial quality of 82 points is described as having chocolate, nutty, and defective flavors. After 6 months of storage in a refrigerated environment in jute packaging, it was described as having a chocolate flavor and defect, which, after 9 months, was characterized as a defective flavor. No flavor descriptors were noted for the samples stored for 6 and 9 months in a refrigerated environment in high-barrier packaging.

Figure 4 presents the results of the multifactorial analysis for acidity descriptors of the coffee beverage from dry-processed beans with initial scores of 82 and 84 on the SCA scale, stored at room conditions (a, b, c) and in a refrigerated system (d, e, f) in different packaging (high barrier – impermeable; and jute – permeable).

Figure 4
Multiple factor analysis of acidity descriptors in coffee beans with varying initial qualities, processed by dry method and stored under ambient (a, b, c) and refrigerated (d, e, f) conditions, in different packaging types. Legend: A = ambient storage; R = refrigerated storage; 82 = initial score of 82 points on the SCA scale; 84 = initial score of 84 points on the SCA scale; HB = high-barrier packaging (impermeable); J = jute packaging (permeable); 0m = 0 months of storage; 6m = 6 months of storage; 9m = 9 months of storage. Attributes: C = citric; M = malic.

For the acidity attribute (Figure 4), the coffees were described as having citric and malic acidity. In both storage environments, the 6-month centroid differed from the others (Figures 4a and 4d), but the differentiation was more pronounced in the environment without refrigeration (Figure 4a). For refrigerated coffees, no difference was observed between those stored in high-barrier and jute packaging, both initially scoring 84 points, as they are located in the same quadrant (Figure 4e). This suggests that coffee of higher initial quality tends to retain its acidity quality regardless of the packaging type when stored in a refrigerated environment. Studies in the literature indicate that citric acidity is a marker of sensory quality in coffee (Carmo et al. 2020, Taveira et al. 2015).

Figure 5 shows the results of the multifactorial analysis for the body descriptors of coffee beverages made from dry-processed beans with initial scores of 82 and 84 on the SCA scale, stored at room temperature (a, b, c) and under refrigeration (d, e, f) in different packaging (high barrier – impermeable; jute – permeable). The body attribute was described as creamy, oily, viscous, and watery.

Figure 5
Multiple factor analysis of body descriptors in coffee beverages from beans with varying initial qualities, processed by dry method and stored under ambient (a, b, c) and refrigerated (d, e, f) conditions, in different packaging types. Legend: A = ambient storage; R = refrigerated storage; 82 = initial score of 82 points on the SCA scale; 84 = initial score of 84 points on the SCA scale; HB = high-barrier packaging (impermeable); J = jute packaging (permeable); 0m = 0 months of storage; 6m = 6 months of storage; 9m = 9 months of storage. Attributes: CR = creamy; VI = viscous; OI = oily; WA = watery.

The description of the body attribute changed over storage time, as seen by the separation of centroids for both ambient (Figure 5a) and refrigerated conditions (Figure 5d). The treatments are displayed in distinct quadrants for both temperatures, indicating differentiation in body description based on storage conditions (Figures 5b and 5e). Similar to other attribute analyses, coffees with higher initial scores tended not to show differentiation even in different packaging types.

In all storage conditions, coffee with an initial score of 84 was described as having a creamy body at the beginning of storage, while coffee with an initial score of 82 was described as viscous, oily, and watery across all storage conditions.

The coffee with the highest initial quality (84 points) maintained a creamy body throughout storage in both packaging types in ambient conditions (Figure 5c). However, in the refrigerated condition, jute packaging altered the sensory quality after 6 and 9 months, describing a viscous body. In contrast, high-barrier packaging with refrigeration preserved the creamy body of the coffee.

The coffee with an initial quality of 82 showed significant variation in the body attribute description over storage, influenced by environment and packaging. A watery body description indicates low body, detracting from the coffee’s sensory quality. Storing coffee with an initial quality of 82 in jute packaging at ambient temperature for 9 months resulted in a watery body. When stored in jute packaging in a refrigerated environment for 9 months, the body was described as oily and watery. High-barrier packaging preserved an oily and viscous body at room temperature over 9 months, and oily only in the refrigerated environment.

Twenty-five volatile compounds were identified in roasted beans of coffees stored up to nine months, with initial scores of 82 or 84 points. These compounds belong to five classes of volatile organic compounds: furan (2-methylfuran, 2,5-dimethylfuran, furfural, furfuryl formate, 2-furamethanol acetate, 5-methyl-2-furancarboxaldehyde, 2-furamethanol), aldehyde (butanal, 2-methylbutanal, 3-methylbutanal), ketone (2,3-pentanedione, 1-(2-furanyl)-ethanone, 1-hydroxy-2-butanone), acid (acetic acid), pyrazine (pyrazine, methylpyrazine, 2,5-dimethylpyrazine, 2,6-dimethylpyrazine, ethylpyrazine), pyrrole (1-methyl-1H-pyrrole, pyrrole), pyridine, phenol (3-methylphenol), thiol (1-propanethiol), and diazole (imidazole). To illustrate the profile of volatile compounds in roasted coffee beans and to analyze sample grouping, principal component analysis was conducted, as shown in Figure 6.

Figure 6
Principal Component Analysis (PCA) of volatile compounds in coffee beans with varying initial qualities, processed by dry method and stored under different conditions. Legend: A = ambient storage; R = refrigerated storage; 82 = initial score of 82 points on the SCA scale; 84 = initial score of 84 points on the SCA scale; HB = high-barrier packaging (impermeable); J = jute packaging (permeable); 0m = 0 months of storage; 6m = 6 months of storage; 9m = 9 months of storage. Volatile compounds: 1 = 2-Methylfuran; 2 = Butanal; 3 = 2-Methylbutanal; 4 = 3-Methylbutanal; 5 = 2,5-Dimethylfuran; 6 = Imidazole; 7 = 2,3-Pentanedione; 8 = 1-Methyl-1H-pyrrole; 9 = 3-Methylphenol; 10 = Pyridine; 11 = Pyrazine; 12 = Methylpyrazine; 13 = 1-Propanethiol; 14 = 2,5-Dimethylpyrazine; 15 = 2,6-Dimethylpyrazine; 16 = Ethylpyrazine; 17 = 1-Hydroxy-2-butanone; 18 = Furfural; 19 = Acetic acid; 20 = Furfuryl formate; 21 = 1-(2-Furanyl)-ethanone; 22 = Pyrrole; 23 = 2-Furamethanol acetate; 24 = 5-Methyl-2-furancarboxaldehyde; 25 = 2-Furamethanol.

It is possible to observe a trend of separation by volatile compounds based on the initial quality of the samples. Coffees with an initial score of 82 points, regardless of storage condition or duration, are located in the negative region of the first component (PC1), associated with volatile compounds 2-methylfuran (1), butanal (2), 2-methylbutanal (3), 3-methylbutanal (4), 2,5-dimethylfuran (5), 1-methyl-1H-pyrrole (8), pyridine (10), pyrrole (22), and 2-furamethanol acetate (23). These volatile compounds have green, rancid, and fruity aromas. In contrast, coffee samples with an initial quality of 84 points are mostly in the positive region of the same component (PC1), related to volatile compounds 2,3-pentanedione (7), 3-methylphenol (9), methylpyrazine (12), 1-propanethiol (13), 2,5-dimethylpyrazine (14), 2,6-dimethylpyrazine (15), ethylpyrazine (16), 1-hydroxy-2-butanone (17), furfural (18), acetic acid (19), and 5-methyl-2-furancarboxaldehyde (24), described as having buttery, caramel, and sweet aromas. This suggests that coffee with an initial quality score of 84 has a higher aroma quality than coffee with an initial score of 82 (Rabelo et al. 2024).

The samples were differentiated into five groups: Group I consists of coffees with an initial score of 82, characterized by volatile compounds like butanal (2), 2,5-dimethylfuran (5), 1-methyl-1H-pyrrole (8), and pyridine (10). Butanal and 2,5-dimethylfuran have a chocolate aroma; 1-methyl-1H-pyrrole has a woody and herbaceous aroma (TGSC 2023), while pyridine has a potent and distinctive aroma (Rabelo et al. 2024). Group II includes samples with an initial quality of 82 points stored at room temperature for 6 months, regardless of packaging (A82HB 6m and A82J 6m), and natural coffee samples with 82 points stored in high-barrier packaging under refrigeration for up to 9 months (R82HB 6m and R82HB 9m). This group shares a volatile compound profile similar to Group I, but in lower concentrations, which is why this group is more centralized in the graph.

Group III comprises coffees with an initial quality of 82 points stored at room temperature for 9 months (A82HB 9m and A82J 9m) and in jute packaging under refrigeration for 6 months (R82J 6m). This group shows higher concentrations of 2-methylfuran, 2-methylbutanal, 3-methylbutanal, and 2,5-dimethylfuran. The compounds 2-methylfuran and 2,5-dimethylfuran have a chocolate aroma profile. The volatile compound 2-methylbutanal is associated with nutty, cereal, caramel, and fruity flavors, while 3-methylbutanal has peach and fruity aromas, as well as chocolate, nut, and cocoa flavors (TGSC 2023). This indicates that over 9 months of storage, transformations occurred in the green bean’s aroma precursors, promoting the formation of pleasant volatile compounds after roasting, regardless of the packaging type.

The coffee sample with an initial quality of 82 points stored in jute packaging under refrigeration for 9 months (R82J 9m) is separate from the others, showing higher concentrations of volatile compounds pyrazine (11), furfuryl formate (20), pyrrole (22), and 2-furamethanol acetate (23). These compounds have nutty and ethereal aromas (TGSC 2023).

For coffee with an initial quality of 82 points, refrigerated storage in high-barrier packaging helped preserve the volatile compound profile. Storage at room temperature led to modifications in the volatile compound profile over 9 months, with no differentiation between permeable and impermeable packaging. However, refrigerated storage in jute packaging caused greater modifications in the volatile compound profile than other conditions and packaging types.

Group IV includes coffees with an initial score of 84 at the beginning of storage and samples stored in high-barrier packaging at room temperature for 6 months (A84HB 6m), mainly associated with volatile compounds 3-methylphenol (9), 2,5-dimethylpyrazine (14), and 5-methyl-2-furancarboxaldehyde (24). These compounds are described as having woody, phenolic, chocolate, sweet, and caramel aromas. Group V consists of samples with 84 points stored at room temperature in impermeable packaging for 9 months (A84HB 9m), in permeable packaging for 6 and 9 months (A84J 6m and A84J 9m), and in high-barrier packaging under refrigeration for 6 and 9 months (R84HB 6m and R84HB 9m). This group is mainly associated with 2,3-pentanedione (7). According to The Good Scents Company (TGSC 2023), 2,3-pentanedione has sweet, spicy, caramel, nutty, toasted, buttery, caramel, marshmallow, and molasses aromas. Borém et al. (2021) found 2,3-pentanedione to be one of the main volatile compounds in both dry- and wet-processed coffees stored in permeable and hermetic packaging. The sample with an initial score of 84 stored in jute packaging under refrigeration (R84J 6m) showed greater variation in volatile compound profile and did not group with other treatments. At 6 months (R84J 6m), it is associated with imidazole (6), a compound formed during roasting from the degradation of sugars reacting with ammonia released by amino acids or proteins through Strecker degradation (da Costa et al. 2023). At 9 months (R84J 9m), it is mainly associated with ethylpyrazine (16) and 1-(2-furanyl)-ethanone (21), which have roasted chestnut and tobacco notes (Flament & Bessiere-Thomas 2002).

This analysis shows that coffee with a higher initial quality (84 points) is more sensitive to storage, as no storage condition preserved its volatile composition for 9 months. The ambient condition with high-barrier packaging preserved the coffee’s volatile profile for only 6 months, with other conditions showing modifications over the storage period.

Other chemical compounds are also used to assess specialty coffee quality during storage, with the lipid composition of beans being extensively studied. Six fatty acids (Figure 7) were identified in dry-processed coffee samples stored in different environments and packaging over nine months, with initial scores of 82 and 84 points. Fatty acids are classified by saturation level as saturated (e.g., palmitic C16:0, heneicosanoic C21:0), monounsaturated (e.g., myristoleic C14:1, oleic C18:1), and polyunsaturated (e.g., linoleic C18:2, linolenic C18:3).

Figure 7
Principal Component Analysis (PCA) of fatty acids in coffee with initial scores of 82 and 84, stored at room and refrigerated temperatures, processed by dry method and packaged in different materials. Legend: A = ambient storage; R = refrigerated storage; 82 = initial score of 82 points on the SCA scale; 84 = initial score of 84 points on the SCA scale; HB = high-barrier packaging (impermeable); J = jute packaging (permeable); 0m = 0 months of storage; 6m = 6 months of storage; 9m = 9 months of storage. Fatty acids: Palmitic (C16:0); Heneicosanoic (C21:0); Myristoleic (C14:1); Oleic (C18:1); Linoleic (C18:2); Linolenic (C18:3).

For fatty acids, separation mainly occurs due to storage time, resulting in five groups. Groups I and II comprise the initial samples, with Group I consisting of samples with an initial quality of 84 points and Group II of samples with an initial quality of 82 points. Higher-quality coffees exhibited a high concentration of linoleic (C18:2) and linolenic (C18:3) fatty acids, while coffees with an initial quality score of 82 showed a lower initial concentration of these polyunsaturated fatty acids.

Group III includes samples stored for 6 months, regardless of initial quality, storage temperature, or packaging. The positioning of this group shows a reduction in polyunsaturated fatty acids in the green bean samples, accompanied by an increase in the concentration of saturated palmitic fatty acid (C16:0). Notably, the coffee sample with an initial quality of 82 points stored under ambient conditions in high-barrier packaging (A82HB 6m) is centered on the graph, outside of Group III, indicating greater preservation of linoleic (C18:2) and linolenic (C18:3) fatty acids. Higher levels of unsaturated fatty acids may indicate greater stability in the chemical matrix of green coffee beans during storage (Holanda et al. 2011). Group IV consists of samples with an initial quality of 82 points stored for 9 months, regardless of storage temperature and packaging (A82HB 9m, A82J 9m, R82BH 9m, and R82J 9m), as well as samples with an initial quality of 84 points stored in permeable packaging in a refrigerated environment for 9 months (R84J 9m). This group is positioned opposite the vectors of polyunsaturated fatty acids, with high concentrations of the saturated fatty acid palmitic (C16:0) and the monounsaturated acids oleic (C18:1) and myristoleic (C14:1). In a study of the fatty acid profile of specialty coffees stored in various packaging types, Borém et al. (2019a) also observed an increase in palmitic and oleic acids, particularly in coffees stored in jute bags under ambient conditions.

Group V consists of samples with an initial quality of 84 points stored for 9 months in high-barrier packaging, under both ambient and refrigerated conditions (A84HB 9m and R84HB 9m). This group is associated with the vector of the saturated fatty acid heneicosanoic (C21:0).

These results suggest that fatty acid transformations occur throughout storage, regardless of initial quality, temperature, or storage packaging. However, for coffee with an initial quality of 82 points, high-barrier packaging under ambient conditions was effective in reducing transformations for up to 6 months. Additionally, an increase in the concentration of heneicosanoic acid was detected in coffees with an initial quality score of 84 points stored for 9 months in impermeable packaging, irrespective of storage temperature. Literature has linked this fatty acid to higher sensory scores, and it has contributed to distinguishing higher-quality coffees from those with lower sensory scores (Borém et al. 2019a).

Chemical analysis of the green coffee beans identified seven organic acids in the natural coffee samples: oxalic, citric, malic, quinic, succinic, lactic, and acetic acids. In the variance analysis of these acid concentrations, succinic and acetic acids did not show significant differences across the evaluated factors. In addition to organic acids, bioactive compounds were identified in green bean samples from natural coffees with initial scores of 82 and 84 points, stored under various conditions for up to 9 months. These compounds included trigonelline, chlorogenic acids, and caffeine, among which only trigonelline showed significant concentration differences in the variance analysis. Thus, a Principal Component Analysis (PCA) was conducted on the organic acids oxalic, citric, malic, quinic, and lactic, along with the bioactive compound trigonelline, as shown in Figure 8.

Figure 8
Principal Component Analysis (PCA) of organic acids and bioactive compounds in coffee with initial scores of 82 and 84, stored at room and refrigerated temperatures, processed by dry method and packaged in different materials. Legend: A = ambient storage; R = refrigerated storage; 82 = initial score of 82 points on the SCA scale; 84 = initial score of 84 points on the SCA scale; HB = high-barrier packaging (impermeable); J = jute packaging (permeable); 0m = 0 months of storage; 6m = 6 months of storage; 9m = 9 months of storage. Compounds: oxalic acid, citric acid, malic acid, quinic acid, lactic acid, and trigonelline.

Five groups were formed. Group I consists of samples at the beginning of storage (0 months) of natural coffees with an initial quality score of 82 points, showing high concentrations of quinic and malic organic acids, as indicated by their positioning in the PCA graph. Group II is primarily composed of coffees with an initial quality of 84 points at 0 months of storage, along with the sample of coffee with 82 points stored in a refrigerated environment with high-barrier packaging for 6 months (R82HB 6m). This group exhibits a higher concentration of lactic acid and lower concentrations of the other organic acids.

After 6 months of storage, a dispersion of coffee samples with an initial quality of 82 points is observed, reflecting the effects of storage environment and packaging on the composition of organic acids and trigonelline in natural coffee beans. However, after 9 months of storage, this differentiation is no longer apparent, with samples clustering together in Group V.

Coffees with an initial quality of 84 points, stored for 6 months, are grouped closely, forming Group III, which shows a reduction in organic acid concentrations compared to the start of storage. This reduction becomes more pronounced after 9 months of storage, forming Group IV.

Groups III, IV, and V are positioned opposite to the vectors of organic acids, indicating that acid content in fruits and seeds declines under storage conditions (Vallarino & Osorio, 2019). Group V also shows a reduction in organic acids. Although trigonelline concentrations across treatments were significantly different, the stability of this compound was maintained for up to 9 months in coffees with an initial score of 82 points, regardless of packaging type or storage temperature.

CONCLUSIONS

It is concluded that:

• In addition to packaging and storage conditions, the initial attributes of natural coffee are a key factor in determining its quality after a 9-month storage period.

• Specialty natural coffees with lower initial sensory quality show greater instability in preserving sensory attributes, and permeable packaging is not recommended for 9-month storage, regardless of storage temperature.

• Specialty natural coffees with a higher initial sensory score exhibit attenuation of sweetness, acidity, body, and aftertaste over 9 months of storage, while maintaining stability in score and sensory descriptors, especially when stored in high-barrier packaging.

• Chemical changes during storage vary with the initial sensory quality of specialty natural coffees, and preservation of volatile compounds and fatty acids is enhanced with high-barrier packaging, regardless of storage temperature.

Acknowledgements

The authors acknowledge Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG), Instituto Nacional de Ciência e Tecnologia do Café (INCT Café), Nucoffee Syngenta, Logística Integrada de Varginha (LIV), and Cool Seed. The authors declare no conflict of interest.

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Correspondence

Correspondence to: Ana Paula de Carvalho [e-mail]

Publication Dates

• Publication in this collection
  07 Apr 2025
• Date of issue
  2025

History

• Received
  13 Sept 2024
• Accepted
  17 Dec 2024