Effect of mixing concentration and roasting time on total phenolic content of tangerine coffee .... The following main experiments focus on developing new products and protecting essenti
INTRODUCTION
The project's criticality
As science and technology advance, as do living conditions and human needs, there is an increasing need to diversify products in order to attract customers while ensuring both quantity and quality Vietnam's coffee growing area is constantly expanding As a result, the output volume increases, promoting the processing, sale, and export of coffee beans In Vietnam, coffee has grown into a full-fledged industry chain According to International Coffee Organization (ICO) research, people who drink coffee on a daily basis can reduce their risk of diabetes by 50% At the same time, it can reduce stress, improve health, and eliminate fatigue by containing active ingredients that aid in the burning of fat deep within the body
According to Satari and Karimi (2008), citrus peels can pose economic and environmental concerns due to fermentation and microorganism spoilage processes On the other hand, it is a valuable by-product of the citrus industry that can be used in food Tangerine peel phytochemicals (phenolics and flavonoids) demonstrate a wide range of biological actions that are garnering the attention of scientists as potentially beneficial to humans As a result, it might be employed as a source of useful compounds and preservatives in the development of newer food products that are safe and have health- promoting properties (Singh et al., 2020)
Arabica is preferred over Robusta because of its distinct aroma and slightly sour flavor As a result, the goal of our research will be to add flavor and taste to Robusta by incorporating tangerine peel When tangerine peel is added, the coffee product will have a tangerine peel aroma as well as a slight sour taste
For the aforementioned reasons, the project’s name is proposed "Study on the production of coffee with the supplement of tangerine ( Citrus reticulata L var.) peel." to contribute to the diversity of coffee products on the market and use the tangerine peels to resolve its waste.
Aim of the study
Investigation of the factors influencing the production of tangerine peel coffee in order to diversify the market's products.
Research content
- Innovation of a process for producing tangerine peel coffee
- Comparison and choice the best production process and specifications
OVERVIEW
Coffee
Coffee is a popular beverage all around the world There are various species of coffee plants in the Rubiaceae family, including: Coffea canephora (Robusta coffee), Coffea liberica, Coffea arabica (Arabica coffee), Coffea stenophylla and Coffea excelsa.(Park,
2015) Coffee has many varieties, but not all coffees produce high yields Coffea arabica and Coffea canephora are the two most important commercial coffee species Arabica coffee accounts for approximately 64% of total world coffee production, whereas Robusta coffee is 36% (Soares et al., 2015) Coffee is used in many areas of the food industry, but the most common use of coffee is for the production of roasting coffee and instant coffee When consumers consume coffee products, they are mainly interested in their sensory quality and medicinal value The nutritional value is of little concern
Almost, arabica and robusta are the two coffee species of the most importance in agronomical and produced in over the world Other varieties of coffee make up a little portion Both species are chemically unique, with varying amounts of minerals, volatile compounds, chlorogenic acids, and caffeine.(Soares et al., 2015) Arabica coffee is commonly used to produce roasted coffee and is regarded more for its taste qualities Robusta coffee is frequently used to produce instant coffee or is mixed with Arabica coffee to produce roasted coffee
• Arabica: According to the International Coffee Organization, Arabica farmers account for more than 60% of global coffee production This was the sort of bean that launched the Ethiopian coffee tale, and it still grows best at higher elevations It was the first coffee bean species to be used in the manufacturing of coffee from roasted coffee beans In the wild, the Arabica plant can grow to a height of 9 to 12 meters, but when produced commercially, it can reach a height of 5 meters Each fruit typically contains two arabica beans, which are harvested after they reach a deep red hue Each 2.5 – 3 kg of seeds yields 1 kilogram of bean and the bean is gray-green, green, light green, and so on The caffeine content of the bean varies depending on the processing procedure and ranges between 1 - 3% Arabica is often preferred over Robusta due to its distinct aroma and slightly sour flavor
• Robusta: Arabica coffee is the most popular, closely followed by Robusta coffee It provides for almost 40% of global coffee production Although Vietnam is the largest exporter of Robusta coffee, it is typically grown in two countries: Africa and Indonesia Robusta coffee is a popular ingredient in espresso and instant coffee The Robusta plant can grow up to 10 meters tall in the wild, but when grown for commercial purposes, it is
3 cut to roughly 5 meters in height to make harvesting considerably easier Each 3 kg of coffee berry yields 1 kilogram of green bean and the bean is gray-green, silver-green, pale yellow, and have a slightly rounded oval shape The caffeine content of the bean varies depending on the processing procedure and ranges between 1.5 - 3% (Đ.V.Phương, 2011) Currently, Robusta in Vietnam only exports raw coffee, so diversifying Vietnamese coffee products is necessary to bring higher added value
2.1.1.2 Structure and chemical composition a) Structure
The pericarp and the seed are the two main parts of the coffee berry
- The pericarp is the fruit's external three layers, which are the mesocarp (mucilage), exocarp (skin), endocarp (parchment)
+ The exocarp, also known as the peel, skin, or epicarp, is the outermost layer of the coffee fruit It might be red, dark red, or yellow depending on the variety
+ The flesh of the coffee berry is the mesocarp, commonly known as mucilage While the term "pulp" can refer to simply the mesocarp at times, it usually refers to a mixture of the exocarp and a piece of the mesocarp that is removed during the pulping process
+ The endocarp, also known as parchment, is the pericarp's innermost layer and the hull that covers the coffee bean It is mostly made up of cellulose It is composed of three to seven layers of sclerenchyma cells
- The coffee seed or bean is made up of three parts: a silver skin, an endosperm and an embryo
+ The silver skin, also known as the perisperm or spermoderm, is the seed's outermost covering It is thin, and varies in color depending on the strains
+ The endosperm consists of only one tissue, which is also the primary storage site of the seed and the fact that the oil content and cell density of cells on the outside and inside of the endosperm differ
Figure 2.1 Coffee Fruit & Seed Anatomy (Adapted from www.drsscientificart.com) b) Chemical composition
In green coffee beans there are many different chemical components The chemical composition of green coffee is determined by the species and variety in question, as well as, other factors to a lesser extent, include cultivation methods, maturity level, and storage conditions.(Clarke, 2012) This is a summary table 2.1 generated in 1975 by Clifford or Vitzthum based on available data to offer reasonable information It has been modified since then, although not significantly
Table 2.1 A summary of compositional data (%db) for Arabica coffee beans and
Content Arabica coffee Robusta coffee
In addition to the components listed above, green coffee contains organic acid, nicotinic acid, pectin, lignin, and others
2.1.2 Sensory and physicochemical criteria of coffee a) Requirements for coffee beans
Green coffee beans are generally used in medicinal and dietary preparations, while roasted coffee beans are mainly used in beverage preparations (Uman et al.,
2016) However, numerous factors contribute to the fragrance, taste, and overall quality of the coffee (Angeloni et al., 2019) Quality is critical in the current coffee industry to satisfy the demands of the coffee consumer market (Barbin et al., 2014) The following factors are commonly used to assess the quality of green coffee:
+ Moisture content is typically less than 13% (w/w)
+ Particle size: determined using an ISO standard set of sieve sizes
+ Density, mass and number of defects on coffee beans
+ The sensory qualities of coffee beans, as well as a variety of other criteria
Currently, green coffee production firms in Vietnam rely on the TCVN 4193: 2014 standard to assess quality This set of standards contains nearly the same content as the standards of International Coffee Organization (ICO) b) Requirements for sensory of ground coffee
Sensory requirements for ground coffee are shown in Table 2.2 according to TCVN 5251:2015
Table 2.2 Requirements for sensory of ground coffee (TCVN 5251:2015)
Color The product's typical brown color
Smell The product's distinctive aroma, no strange smell
Taste The specific characteristics of product
Status Powder, smooth, and free of lumps
Brewed coffee There is a specific color of the product
6 c) Requirements for physicochemical of ground coffee
Physicochemical requirements for ground coffee are shown in Table 2.3 according to TCVN 5251:2015
Table 2.3 Physicochemical requirements for ground coffee (TCVN 5251:2015)
Fineness expressed as a percentage of mass:
– Pass through a sieve with at least 0.56 mm holes
– The sieve's smallest hole size is 0.25 mm, so the particles are retained
15 Moisture expressed as a percentage of mass, but no more than 5,0 Caffeine content expressed as a percentage of mass, but no less than 1,0
Water-soluble matter expressed as a percentage of dry matter, but no less than 25
Ash content insoluble in hydrochloric acid (HCl) expressed as a percentage of mass, but no more than 0,2
2.1.3 Coffee roasting production process (L.V.V.Mẫn et al.,2011)
Coffee beans, also known as green coffee, are used as raw materials in the production of roasted and ground coffee The dry method and the wet method are the two main methods for preliminary processing However, preliminary processing by the wet method will help the coffee product to be of higher quality than the dry method The graphic below depicts a typical coffee roasting operation's process flow
Figure 2.2 Typical coffee roasting operation
Raw material: To ensure the consistency of the coffee during the roasting process, coffee beans whose size and density are not assured must be removed The moisture content of the raw material is less than 13% a) Cleaning: Cleaning is the most important step that farmers must follow in order to produce high-quality coffee Before proceeding to the next step, any impurities such as dirt, leaves, or stones must be removed To remove small particles clinging to the surface of the coffee bean and to separate the coffee beans from undesired elements based on density difference, the coffee must go through a cleaning step b) Roasting: This is the most essential and crucial stage in determining the quality of the final coffee since it modifies the physicochemical qualities of the coffee beans, making the subsequent grinding process simpler This procedure begins at a temperature of 120 °C and ends between 180 and 200 °C A variety of actions occur in accordance with the
Tangerine peel
Citrus plants, such as oranges, tangerines, lemons, and grapefruits, produce fruits that are high in nutrients Because the peels of these fruits can produce a high concentration of phenolics, they have been used in a variety of food products Normally, they are unconcerned about the garbage that is discharged into the environment, but due to the vast number of by-products emitted, they have been explored as a significant supply of nutrients at a very low cost Tangerine peel is extensively used in traditional medicine, thus adding it to culinary products not only adds nutrients but also helps to avoid specific diseases As a result, several evaluations have been written to explain the potential use of tangerine peels, rather than simply dismissing them as an environmental waste (Rafiq et al., 2016)
2.2.2 Chemical composition of tangerine peel
Table 2.5 Chemical composition of tangerine peel essential oil
Fresh tangerine peel contains about 3.8% essential oil The essential oil of tangerine peel contains approximately 17 components (Table 2.5), where the main components were limonene (28.11%), xanthotoxin (18.40%), n-Methyl-D3-Aziridine (9.07%), cytidine (8.34%), Propanoic Acid, 2-Methyl-,Methyle (4.99%) and 1,4-diethynylcyclobutene (4.73%)
There are a variety of chemical compounds found in the oils of citrus fruits such as oranges, lemons, and tangerines, including limonene, xanthotoxin, cytidine, and others Limonene has the highest percentage of chemical composition in tangerine peel The chemical formula for D – Limonene (RI = 1,487, ρ = 840 kg/m3) (Li and Lu, 2016) is 1 - methyl - 4 - (1 - methylethenyl) cyclohexane (Ren et al., 2020) Limonene and its derivatives have potential applications in a wide range of areas, including food, medicines, cosmetics, and so on They are most typically found in nature and provide numerous health benefits, including antioxidants, stress reduction, illness prevention, and so on According to certain research, limonene can also help prevent cancer Because limonene has a pleasant aroma, it is classified as safe as a flavoring agent by the Generally Recognized As Safe (GRAS)
In addition to limonene, xanthotoxin is a furanocoumarin chemical present in citrus fruit peels Xanthotoxin, also known as 8-metoxypsoralen, possesses anti-inflammatory, epidermal proliferative disorder, and psoriasis therapy properties similar to limonene Furthermore, xanthotoxin has bone healing in ovariectomized rats when tested on mice It has since been recognized as an anti – osteoporotic drug for menopausal women (Lee et al., 2017)
MATERIALS AND METHOD
Materials
The experiment used the coffee beans belonging to the variety of Coffea robusta Coffee beans originated from Dak Nong province which located in 9 th village, Quang Tin commune, Dak R'lap district, Dak Nong province
Tangerine peels (Citrus reticulata L var.) are purchased on the Thu Duc whosale market Then peeling off and storing in the frige at 5 o C
3.1.3.1 Chemicals for determined the Total Phenolic Content
3.1.3.2 Chemicals for determined the scavenging activity (DPPH)
3.1.3.3 Chemicals for determined the acidity
Chemicals are purchased at Hoa Nam Chemical Store, Add: 239/4 Ly Thuong Kiet street, Ward 11, District 5, Ho Chi Minh city
3.1.3.4 Tangerine coffee methanolic extract for determined the Total Phenolic Content and Scavenging Activity (DPPH)
Methanol solvents were applied for bioactive compounds extraction to determine and compare antioxidant activity of the tested citrus peel samples (Abd El-ghfar et al.,
2016) Weight 2g of tangerines samples and extract with and 80 ml of methanol (70%) at
70 o C then shaked by Votex machine Extracts were centrifuged (3500 rpm for 15 min at room temperature) Then the extracts were filtered using filter paper Whatman No.4 according to (Jo et al., 2003) Replicate the extraction until the extract became colorless For this experiment, each sample is repliceated 3 times
Some of the equipment and tools used during the research include:
Centrifuge ROTANTA 460 Hettich Zentrifugen, Germany
Vortex ZX3 test tube shaker, Germany
UV Spectrophotometer – Vis Halo Vis 20 Dynamica, UK
Laboratory glassware: test tube, erlen (250 mL, 500 mL, 1000 )
mL), pipette (1 mL, 5 mL, 10 mL),
3.2.1 Process proposal of tangerine coffee
Figure 3.2 Process of tangerine coffee product
Green bean coffee: Robusta green beans are bought at Dak Nong province which are sorted base on the size and color, all of dust and impurities are removed Then stored at dry place with ambient tempurture
Tangerine peels: after purchasing, place in fridge Tangerine much have similar in color and size Following that, remove the white part inside the tangerine peels and store in frige for used
Soaking tangerine peels with acid citric (0,5% at 40 minutes)
The antioxidant of tangerine peels which is soaked with acid citric is higher Inaddition, the acid citric increased the sour taste of the product that is the main purpose of our project (S.T.Liệm, Đ.V Út, 2013) Tangerine peels after removed white part inside then soaking with acid citric 0.5% for 40 minutes Following that, let them dried at ambient temperature for 15 minutes
Roasting coffee: Robusta coffee had strongly bitter taste so the medium roasting which roasting time should be 9 minutes at 210 o C (Dharmawan, A., Cahyo, F., & Widyotomo, S 2018) Following sorting stage, green bean coffee is roasted in the drum roaster for 9 minutes at 210 o C
Mixing and roasting tangerine peels with coffee
The coffee after roasing at approriate time then are mixed with proceed tangerine peels Following that, the mixer are continious roasted The percentage of tangerine peels and 2nd roasting are demonstrated by the table 3.1:
Table 3.1 Investigation of the concentration and roasting time of tangerine peels
Factor A: % mass of tangerine peel which is accounted by 100g of each sample at 5 concentrations: A1 (2%), A2 (4%), A3 (6%), A4 (8%), A5(10%)
Factor B: Roasting time of tangerine peel with coffee at 5 period times: B1 (1 minute),
Figure 3.3 Experimental layout diagram with B 1 (1 minute), B 2 (2 minutes), B 3 (3 minutes), B 4 (4 minutes), B 5 (5 minutes)
Cooling: After roasting, quickly cool tangerine coffee to reduce the bitter taste Then prepared for the grinding stage
Grinding: The size for pouring coffee product is 50x with PSD (particle size distribution) around 50%
Packaging: According to the drinking method, tangerine coffee is pack with zipple paper pack (12cm x 22cm) Each pack contained around 300g of coffee and used paper fillter for used
Moisture, ash, protein, fat, cafein were evaluated with approiated standard AOAC methods (AOAC 2005)
3.3.2 Determination of Total Phenolic content
Mechanism: Total phenolic contents of sample were determined by method which was discribed by Folin–Ciocalteu assay (Singleton and Rossi 1965)
The Folin-Ciocalteu method is described as the reaction forms a blue chromophore constituted by a phosphotungsticphosphomolybdenum complex (Schofield, P.; Mbugua
2001) where the maximum absorption of the chromophores depends on the alkaline solution and the concentration of phenolic compounds (Schofield, P.; Mbugua 2001) Procedure: 100 ul of tangerine coffee methanolic extracts were added into 10 ml of methanol 70 o Then, pipetted 0.1 ml of these solutions and mixed with 2.5 ml of 1:10 diluted Folin–Ciocalteau reagent, and 2.0 ml of 7.5% sodium carbonate (Na2CO3) After incubation at ambient temperture for 2 hours in dark place The absorbance of the reaction mixtures was measured at 765 nm by using a spectrophotometer The standard curve used Gallic acid at increasing content TPC of coffee extracts were expressed in milligram gallic acid equivalents (mg GAE/g extract)
The Total Phenolic content (mg GAE/100g) determined by the following fomula:
𝑚 where: a is the slope coefficient of the gallic acid standard curve of sample dF: The dilute of sample m: Sample solid mass (2g)
V: Volume sample (2ml) m: Mass of solid sample (g)
DPPH scavenging activity of tangerine coffee extracts was determined according to the method described by (Yi, Z et al 2008) The antioxidant activities defined as using 1,1- diphenyl-2-picryl-hydrazyl (DPPH) which is described by (Thaipong et al., 2006)
Procedure: Stock solution (DPPH 0.61mM): Weight exactly 0.24 mg DPPH (solid stage) and disolve into 100ml methanol 70 o into untransparent glass bottle
Prepare DPPH solution 0.2 mM by dilute 16.4 mL DPPH 0.61 mM solution into 33.6mL methanol 70 o Two types of samples were prepared by the following table 3.2:
Table 3.2 Concentration of sample for determination the total phenolic content
Sample solution was mixed with methanolic solution of DPPH (0.2 mM) Then stay the mixture in darkness for 30 min at ambient temperature The absorbance of the sample was measured at 515 nm with spectrophotometer DPPH scavenging capacity of the samples was measured by the change of the ABS and was determined by using the following formula:
Ac is the absorbance's at 515 nm of the control
As is the absorbance's at 515 nm of the sample
According to the experimental procedure described in Association of 198 the Official Analytical Chemists (AOAC, 1995) 2 g of sample were poured into 80 ml of an 70% v/v methanol solution then votexed and centrifuged (3.1.5) Thereafter, solution was filtered and diluted 20 fold Finally, 5 ml of the extract was titrated with NaOH 0.1M with Phenolphtalein 1% as indicator The experiment was replicate 3 times
Purpose: Evaluated the sensory quality of each sample based on the level scale in 3 factor (color, taste, smell) On the other hand, the processed coffee are not significantly different on the TPC and DPPH so the sensory testing is applied for sensory evaluation
Procedure: To evaluate coffee sensory, a scale for the product's criteria is bluit accorrding to: food product - sensory analysis - scoring method according to Viet Nam National Standard: TCVN 3215 - 79 (table 3.3) According to TCVN 3215 - 79, a 20-point system is used based on a unified scale with 6 levels (from 0 to 5) and the highest score of
5 for each indicator Applied to test all sensory criteria or each individual criterion (state, color, smell, taste ) of each type of product and goods
Table 3.3 Sensory evaluation scale according to TCVN 3215 – 79
1 5 The product has specific and obvious properties for the criterion under consideration, the product is free of defects
2 4 The product is free from defects and small defects, or both, but reduces the sensory value of the product
3 3 The product has defects which is reduced the sensory value of the product but the product is still up to the standard
4 2 Product has a defect that renders the product less than the standard quality but still marketable
5 1 The product has serious defects and it is does not meet the main use of the product, but the product is not totally damaged, after being recycled, it can still be used
6 0 Products with fully defects and cannot be used anymore
Based on the above description, in order to evaluate the sensory quality of the tangerine coffee product obtained from the experimental samples, conduct sensory evaluation for each product sample, then take the average results The scale is built for the criteria of tangerine coffee products as follows:
Table 3.4 Sensory evaluation of tangerine coffee products according to scoring method TCVN 3215-79