Consumer perception of decocted coffee leaf tea originated from different altitude

It is commonly known that plantation location influences the composition of the coffee component as well as the leaves. Therefore, it was expected that the difference location will also affect the quality of decocted one. In this current study, effect of plantation location is investigated on Arabica and Robusta coffee leaf tea. Two different coffee plantations were chosen as the region of observation (560 ASL and 1700 ASL). All the coffee leaf tea was brewed by decoction method, in which sensorially optimized by Just about Right (JAR) method. The sensory attributes of concern were included sweet, sour, bitter taste and astringent mouth-feel. Considering consumer preference on the brewed coffee leaf tea, the decoction brewing condition were set on 95°C for 5 minutes. Additionally, coffee leaf tea grown at higher altitudes exhibits significantly greater total phenolic content (TPC) and antioxidant activity (p < 0.05). Not only does this tea have higher TPC and antioxidant activity at higher altitudes, but it also shows superior consumer sensory acceptability. This may be supported by the fact that higher altitude coffee leaf tea has more diverse sensory driver components than that of lower altitude coffee leaf tea as suggested by LC-MS.


Introduction
Pruning the leaves is one of common practice for cultivating the coffee plant.The pruning process aims to increase the production and quality of the coffee beans.This is normally conducted 3 to 4 times a year.This process produces the waste that is normally used for compost or cattle feed.Meanwhile, it has been reported that coffee leaf contains antioxidants and many other bioactive compounds It has also been reported that the coffee leaf can be potentially developed as functional products [1,2].
Herbal tea is one of food product developed from coffee leaf.While mimicking Camellia sinensis tea processes for coffee leaf has been reported, to date there are limited resources to be found in the literature in terms of sensory profiling of coffee leaf tea.However, intensive preliminary studies have been conducted on the sensory profile of local coffee leaf tea in Indonesia [3][4][5].It was discovered that the sensory profile of tea from various farms is not the same, despite being made using the same methodology.It has long been understood that the tea quality is mainly considered by the leaves quality.The age of the leaves (where the leaves are harvested), the strength of the sun, and the height all impact the quality of the tea leaves.High-quality tea leaves include more phytochemicals, which are most typically seen in the first two leaves.Decrease intensity sun shadow (mountain) may cause the synthesis of phytochemicals such as catechins and L-Theanine, as well as decrease caffeine levels, which are greater in lowland with more shade [6].Therefore, in this current study, the influence of altitude on quality of the coffee leaf tea is investigated.The sensory attributes profile of tea is highly affected by the brewing technique.There are also many factors affecting the brewing effectiveness such as quality of tea leaf powder, the quality of water, the brew-container, temperature as well as duration of brewing [7][8][9].In this current study, the important sensory attributes such as sweetness, bitterness, sourness, and astringency are investigated related to the brewing temperature and duration.

Materials
The coffee leaves (Arabica and Robusta) from East Java Province were utilized in this investigation, Indonesia.The high-altitude coffee leaf were collected from Tirtoyudo-Malang Regency, East Java (1700 meters above sea level) and from Silo-Jember Regency, East Java (560 meters above sea level).The tea was prepared and processed according to protocol for fermented/oxidized coffee leaf tea as suggested [10].

Methodology
By varying the brewing temperature (89.34-100.600C)and duration (2.17-7.83minutes), the Just About Right (JAR) approach was utilized to attain the optimal sensory qualities (sweetness, bitterness, sourness, and astringency).[11].The tea produced from optimum brewing condition then further chemically analyzed and arranged by Nested Design.Data processing on JAR data for Penalty Analysis was conducted by XLSTAT 2019.1.

Coffee leaf tea brewing
All the coffee leaf tea were brewed by decoction method at combinations of brewing temperature (89.34-100.60°C)and time (2.17-7.83minutes).Once the brewing process finished, the coffee leaf tea was stored in a refrigerator (10°C) overnight before serving to the panelists.The water to coffee leaf ratio was 1:100.It has been previously reported that bitter taste and astringent sensation of tea beverage tended to decrease with cold serving [12].

Sensory evaluation by JAR technique
JAR technique was utilized for sensory assessment, which attempts to test the feasibility of specific attribute levels and is used to establish the optimal number of characteristics in a product [13].JAR method was used to obtain the optimum sensory attributes (sweetness, bitterness, sourness and astringency).This sensory evaluation involved 107 consumer respondents between 20 and 30 years old.There were 13 runs or samples per session and the panellists were invited to join 4 sessions.Panellists were served one sample at one time.Each sample (30ml) was poured into a paper cup and was presented at 10 o C.

Statistical analysis
All collected data was statistically analyzed with ANOVA and further checked with Tukey post-hoc test for 95% of significance level on Minitab-19.Meanwhile, JAR data was analysed using penalty analysis feature in XLSTAT 2019.

JAR Sensory evaluation
The highest number of JAR attributes was obtained at brewing condition of 95ºC for 5 minutes (Table 1).It also shows that high altitude coffee leaf tea has more JAR attributes than that of low altitude coffee leaf tea.High altitude arabica coffee leaf tea has 4 approved attributes, while for robusta coffee leaf tea has 3 approved attributes that have reached JAR, namely sweetness, sourness and astringent mouthfeel.On the other hand, there is only 1 approved attribute for low altitude coffee leaf tea, such as sweetness for Arabica and sourness for Robusta.Of all the coffee leaf tea samples tested, only the low altitude robusta coffee leaf tea samples were not yet JAR.The response were observed from 107 untrained panellists and tabulated from penalty analysis.Too High = 3, Just-About-Right = 2, Too Low = 1.The sign of (*) indicates the significant mean drop for non-JAR categories (important to be improved otherwise rejected).
Meanwhile, the sweet taste in tea can be caused by sugar (glucose, saccharose, and fructose) and several amino acids (L-proline and L-threonine [18,19].Glucose, saccharose, and fructose are derivatives of the sugar group while the rest are protein and amino acid groups.The cause of the sweet taste found in coffee leaf teas used was presence of amino acid compounds, aspartame acid, glucose and glucose phosphate detected by LC-MS.
Caffeine usually gives bitter hint taste in food products, especially in tea [20].Caffeine can affect tea characteristics such as taste to acidity, astringency, and bitterness [21].The compounds that cause a bitter taste in the coffee leaf tea samples used include phenol and caffeine.Both compounds were detected in the LC-MS analysis.The results of sensory optimization show that only high altitude arabica coffee leaf tea has reached JAR.
Organic acids are typically responsible for tea's sour flavor.The sour flavor is caused by carboxylic acid, boronic acid, sulfonic acid, carbamic acid, carbonic acid, citric acid, and propionic acid found in coffee leaf.Only the low altitude arabica coffee leaf were not JAR from all samples.Generally, the astringent sensation is affected by the presence of tannins, oxalic acid, gallic acid, and cathecins which interact with proteins within the saliva or proteins at particular receptors of taste, resulting in astringent alterations [22,23].Tannin compounds can cause astringent sensation in food products [17].The presence of phenol and tannin components was responsible for the astringent sensation in the coffee leaf tea samples studied.Only high altitude (arabica and robusta) coffee leaf tea has met the JAR for the astringent characteristic out of the four samples evaluated.

Characteristics of brewed coffee leaf tea
The entirity if chemical characteristics of coffee leaf teas is shown at Table 2.The total phenolic compound in coffee leaf tea originated from high altitude plantation was significantly higher than those from low altitude plantation (p-value<0.05).The difference in TPC was also observed between Arabica and Robusta only at coffee leaf tea originating from a high-altitude plantation, in which Arabica TPC was significantly higher than Robusta TPC (p-value<0.05).The TPC yield in this research (42.08-195.63 mg GAE/g) is lower compared to Taiwan coffee leaf tea (50-440 mg GAE/g approximately) and Yunnan Province in China coffee leaf tea (117.47-177.77mgGA/g) [24,25], but higher from Songkhla Thailand (13 mg GAE/g) [26].
The influence of altitude also shows a similar response on antioxidant activity (p-value<0.05).However, there was no significant difference in antioxidant activity observed between Robusta and Arabica.It was suggested that differences in antioxidant activity and free radical scavenging are contributed by the type of tea, harvesting method, harvest time, oxidation process, age and altitude [27].The antioxidant level from arabica coffee leaf tea in this research is remainly competitive with another dried mature arabica coffee leaf tea from Taiwan which had 91.04 ± 0.84% [25].
It was observed that the caffeine in coffee leaf originated from low altitude plantation is significantly higher than those from high altitude plantation (p-value<0.05).The difference in caffeine is also observed between Arabica and Robusta only at coffee leaf tea originating from a high-altitude plantation, in which Arabica caffeine is significantly higher than Robusta caffeine (p-value<0.05).The quantity of caffeine is mainly affected by leaf age and duration of growing season.However, the caffeine amount in tea is primarily impacted by the tea production system, such as carbon dioxide in free air, which may also alter the caffeine content in leaf tea [28].Compared to other coffee leaf tea from Yunnan Province in China and from Taiwan, caffeine content of Jember's Indonesia coffee leaf tea is more than twenty fold lower [24,25].
It was apperared that arabica low-altitude significantly had the highest tannin content, meanhwile robusta from high-altitude had the lowest one.There is no significant difference in Total Dissolved Solids for all samples.This might be contributed by the fact that all samples were prepared homogeneously.Similar trend was also observed for pH, as there is no significant difference between samples.The pH of the coffee leaf was recorded between 7.0 and 7.1, indicating that brewed coffee leaf tea is neutral.
It was also found that altitude may not affect the oxalate content of coffee leaf tea.However, in both altitudes, Arabica coffee leaf tea tended to have lower oxalic acid than Robusta (p-value<0.05).The coffee leaf tea featured 0.010 g/kg to 0.042 g/kg of oxalic acid in which much lower than that of oolong-Camelia sinensis tea.It was reported that the amount of dissolved oxalate extracted from oolong tea was 0.23 g / kg was [29].

Conclusion
Based on penalty analysis of JAR data, decoction brewing technique is optimum for coffee leaf tea when it runs at 95⁰C for 5 minutes.High altitude coffee leaf tea was shown to have more JAR characteristics than low altitude coffee leaf tea.High altitude coffee leaf tea has the most antioxidant activity and total phenolic content, but the one from low altitude has greater caffeine content and higher tannin content.According to the LC-MS data, high altitude coffee leaf tea contains more chemical components than that of the low one, which supports the fact that panellists preferred high altitude coffee leaf tea better.

Referencees
[1] Fibrianto K, Yuwono S S and Hasyati N 2021 Just about right analysis of coffee leaves tea bitterness and astringency by modifying brewing temperature and time.IOP Conf Ser: Earth Environ Sci 672 (012053) pp 1-5

Table 1 .
Just-About-Right tabulation of decocted coffee leaf tea at different brewing temperature and duration

Table 2 .
Effect of altitude and coffee leaf type on chemical characteristics of decocted coffee leaf tea Notes: (*) indicates a significant difference (α<0.05) between altitudes.All data were analysed in duplicate form.