Robusta and Arabica coffee beans chemical components
History of Coffee
Coffee beans are from a coffee plant that is a member of the genus Coffea, which has over 80 different species members (Choi et al, 2010). The coffee berries mostly have two seeds but very small percentage that only has one seed which are called peaberries that are obtained by three different procedures that are wet, wet or semi-dry processing. According to Duarte, Pereira and Farah, theses process produces coffee with different characteristics for instance, washed coffee are better quality with less body, higher acidity and more aroma that are then roasted, ground and brewed (Camp et al.2010).
Coffee plants are now mainly found in Asia, South America, Africa and Brazil. Brazil is being to be the largest coffee producer and exporter that are responsible for thirty percent of the green coffee beans available in markets. The economic commodity and stability in these countries coffee, eighty one percent are Coffee Arabica of the two most popular coffee beans that are accounts for seventy percent of the world’s coffee production (Dias et al.2010). As Coffee Arabica beans are considered as the higher quality and higher desired flavour than Coffee Robusta; are approximately two-three times more expensive than the Robusta beans, therefore fraudulence occur due to they are more expensive to buy and sell (Perks.2008).
The longer the coffee roasts the deeper is the colour. It is has been found that the coffee beans components also contain between seven and seventeen percent fat, in which Arabica seeds contain approximately five percent more than Robusta. The main green coffee oil is triacylglycerols with fatty acids that are very much similar to vegetable oils (Ferrari et al. 2010). It has been suggested that the content of the fatty acid in coffee beans is unchangeable before or after the roasting process. Mainly the green coffee oils are indulged in the cosmetic industry while the oils produced from roasted beans are involved in food applications.
The Arabica roasted coffee consist of cell-wall polysaccharides, proteins, sucrose, chlorogenic acids that each component plays a major role, for instance proteins and amino acids are essential components in producing the coffee aroma (Joet et al.2010).
Coffee can be identified by describing it by different ways; green coffee is, “harvested coffee bean before the roasting process” (Campo, et al.2010). Coffee bean, “coffee seed that has been roasted” and roasted coffee is, “green coffee roasted to any degree” and soluble coffee is, “roasted coffee that is dried water-soluble” (Choi et al.2010).
Components under Investigation
Coffee has many thousands of components that these compounds give more interest in studying coffee. Here we are looking at so many different components in many different coffee samples with one technique in order to quantify them with measurements. If this success then, coffee flavour and aroma main components would be identified for understanding the reason behind it not only for coffee as a food product but also it can open a door for many other food products to get approach such study. To identify the reason behind the flovaour and aroma whether the temperature affect the coffee bean by having different components that make them different from one coffee that is planted in one country to another; whether the temperature is the natural sun exposure that is hotter in certain coffees from another that produces chemicals components that make a distinguished coffee to another country.
Coffee Coffee has a very important role economically as it is the world second trade after oil and provides great employment for around twenty million people. Coffee also has a major social role due to its taste and aroma features with a stimulant effect to make consumable worldwide, (Martins and Gloria 2010). The popularity of coffee makes economic stability for the worldwide as more coffee shops are setting-up every year such as there are over 750 Costa coffee shopes in the UK (Costa Foundation, .
It was studied that green roasted coffee acidity is dependent upon the degree of roast (Marbrouk and Deatherage.1956). The acidity and sourness of coffee importantly contribute to the sensory quality. The acids present in coffee are responsible for 11% of the green beans weight and 6% of roasted coffee beans weight
Coffee species are hundreds but the two most important ones are Coffee Arabica and Canephora (Robusta) coffee, which are different in the taste, economic prises and needed growth conditions.
Arabica coffee is well known for its pleasant taste range from sweet to tangy. Arabica bean looks like blueberries and after roasting has a distinguishable taste tone. They are usually gown at high altitude between 600-200 M in subtropical climates. The tree normally takes long time to grow and gives different flavours in different parts in the world, suggesting the soil type and weather might be the cause (Choi et al 2009). Coffee Arabica crop are well known of the highest quality and its prises are very expensive and usually sold in coffee stores as high quality blend.
Robusta coffee tree grow at low altitude of 200-800M and within 2-3 years the first crop can be sold. The growth conditions are unspecific and taste ranges from neutral, bitter and oatmeal while the unroasted beans smell like raw peanut. They are also known of low cost of production comparing to Arabica. Mostly are sold in supermarkets known as the cheaper blend due to high quality Robusta coffee is very rare. Robusta coffee is more used in esperesso coffees due to it tends to increase the body and foam of the coffee. See figure 1 Robusta beans and Arabica beans (Chio et al. 2009).
Although coffee beans are different in colour, shape and size but once they have been roasted it is hard to distinguish between them which makes fraudulences and authenticity a possibility. Control parameters are needed for coffee beans roasting process to not exceed the limit as chemical properties can be altered due to roasting time and temperature. The usual effect can be obviously observed from the outer surface of the beans. Scientifically the physicochemical properties can be measured from Trigonelline, nicotinic acid, Chlorogenic acid ratios. See figure (1) Arabica and Robusta coffees roasted (Olivera and Ferreira. 1999).
The altered compounds produced during coffee roasting are believed to be responsible for coffee aroma and taste.
The three different stages of roasting process are:
Drying the coffee beans in the 1st half of the process when the volatile compunds and water are released, due to that the beans change from green to yellow colour.
2) Beans go through something called Prolysis that is characterised by physical and chemical changes. The beans turns to brown as a result of releasing volatile compounds, sugar and release of water molecules that heat caramelise it and maillard reaction cause the browning of the beans.
3) Cooling the coffee beans to prevent burning.
It has been suggested that the roasting process is responsible for the coffee aroma and flavour. However, Chlorogenic acid degradation gives rise to the bitterness taste as it results in the phenolic substance (France, Mendonca and Oliveira. 2005).
Caffeine is an alkaloid; a large class of organic compounds that is nitrogen centred structure. Caffeine is usually present in many drinks such as tea, coffee, cocoa beans. It is known as an antioxidant and natural pesticide that kills insects live in plants. It is one of the most popular psychoactive substances that have a stimulant effect in the Central nervous system. Many studies have highlighted the health risks linked to high levels of caffeine consumption and arrhythmias, hypokalemia, hyperglycaemia, vomiting and convulsions (Sout et al. 2010). Problems associated with Caffeine intake in pregnant women has also been found that it causes fetal growth problems such as; nervousness, insomnia, restlessness, gastrointestinal upset, tremors, tachycardia and psychomotor agitation. The Brazilian National Health Agency, it is suggested that the concentration of caffeine in a decaffeinated coffee must be less than 0.1% of the normal levels that is found in pure Arabica and robusta coffees (Souto et al. 2010). It has been reported by Rubayiza and Meuren (2005) that caffeine in Arabica coffee has less caffeine contents than in Robusta coffee.
In a study that was noted by Cadeias, Gallardo and Matos (2009) that there is no definite way of knowing the exact amount of caffeine in any regular cup, that they clarified the incredible difference in amounts from highest to lowest content. They have identified the difference in their study of the highest and lowest caffeine to be 17-fold.
Chlorogenic acid is an ester of caffeic acid and quinic acid. It is known as poly-phenolic group. That is present by approximately 6-12% in coffee constituents. Caffeic acid of that is one of the phenolic compounds. It is an organic compound that acts as an antioxidant, able to delay glucose release in the body after a meal and has an important role in intermediating in lignin biosynthesis. Chlorogenic Acid has a major role in coffee taste and roasted coffee colour and it has been believed that it is responsible for coffee hunger (Galilea and pena. 2007). It has a positive health contribution by preventing cardiovascular disease and type II diabetes. It has an antioxidant effect in coffee beans and it decreases the oxidation of low-density lipoproteins in humans, prevent damage to human epithelial cells by oxidation and inhibit the metabolism of glucose 6-phosphate (Stalmach et al. 2010).
Caffeic acid is a cinnamic acid that is a yellow solid organic compound that is present in wine and coffee that is a polar and hydrophilic. It forms bonds with other molecules like esters as it is very reactive (Batista et al.2010). That contains Phenolic acid and acrylic functional groups. It is found in most all plants that has a major role in Lignin biosynthesis. It has been reported that it has an antioxidant activity (Higdon.2007). It has been suggested that caffeic acid has a positive health effects of inhibiting the growth of the tumours only in the hepatocarinoma cells of the mouse but not in human’s case.
Trigonelline is formed by methyl group and Nitrogen atom. It is one of the alkaloid forms that is produced from vitamin B3 that is found in coffee seeds and many plants. It is a prevalent non protein nitrogen compound that is found in garden peas, oats, potatoes and especially Robusta coffee. It is an antioxidant compound that normally excretes in urine. It is believed that Trigonelline is responsible for coffee aroma after the roasting processes the decomposition to produce Pyridine and Nicotinic Acid (Taylor and Mottram.1996). Trigonelline and caffeic acid components have proven that they prevent the bacteria,Steptoccus mutans from occurring plaque by prevent it attach to teeth (Antonio et al. 2010). Although it has shown in animals that Trigonelline has an anti-cancer properties and able to regenerate the dendrites and axons of the axons and enhance memory (Perrone et al. 2008).
It is an organic compound Niacin, B3 and is extracted from liver that is classified as one of the essential nutrients. It is one of pyridine derivative that is a colourless compound. Usually is found in coffee depends on the roasting process that Trigonelline is demethylated produces Nicotinic Acid in different levels that is highly bioavailable that making coffee a good source of vitamin B3 (Clark and Macrae.1988). It has been suggested that quantifying Trigonelline and nicotinic acid ratio can indicate the degree of the coffee beans roasting that have endured (Perrone et al.2008) that further future studies of roasting can focus on the nicotinic acid levels as a way for investigation. It has proven to be abundant in coffee and has health benefits that it improves insulin sensitivity, decrease inflammation, lower the risk of diabetes and reduce chronic heart disease (Wu et al.2009).