A Detail Chemistry of Coffee and Its Analysis

This review article highlights the detailed chemistry of coffee including its components; chemical constituents like carbohydrates, proteins, lipids, and caffeine; aromatic principles; oil and waxes; and minerals and acids. The high extent of caffeine can be found in the coffee plants; hence, in the second part of the study, various analytical methods are designed for the proper identification, separation, optimization, purification, and determination of caffeine present in coffee, tea, and marketed coffee. These analytical methods are appropriated for the separation and quantification of caffeine. The various analytical methods include spectroscopy methods like UV, IR, and NMR spectroscopy; chromatographic methods like paper, TLC, column, HPLC, and gas chromatography; and hyphenated techniques like LC–MS, GC–MS, and GC–MS/MS. This article compares and contrasts the amount of caffeine by various analytical methods.


Introduction
Coffee consists of ripe seeds of Coffea arabica Linn., belonging to family Rubiaceae. Coffee extracted from coffee bean is also present in crimson fruits is completely removed, and the spermoderm is removed, occasionally. The seeds of botanical genus Coffea may be raw, roasted, whole, or ground. The prepared drink through such coffee seeds is also called as coffee. Among 70 species of coffee, only three are cultivated. 75% of the world's production of coffee is provided by Coffea arabica, about 25% by Coffea canephora, and less than 1% by Coffea liberica and others. Generally, coffee is cultivated at the altitude of 1000-2000 [1]. It is indigenous to Ethiopia, Brazil, India, Vietnam, Mexico, Nepal Guatemala, Indonesia, and Sri Lanka.
The following sections will be discussed in detail after acceptance of this short proposal: • This article will deal on the types of carbohydrate, protein, lipids, and other chemical constituents in detail.
• This article will review on various analytical methods for the estimation of constituents present in coffee.
Coffee is often used as antioxidants, but more importantly coffee is a good source of chromium and magnesium that assist in controlling blood sugar by ensuring proper usage of insulin.
The main chemical ingredients in coffee beans are given below: The carbohydrate content of green and roasted coffee (Santos) was identified and measured. Green coffee contained about 6-7% of sucrose as soluble sugars and low amount of glucose. The soluble sugars of roasted coffee were sucrose, fructose, and glucose. The experiment was also carried out for the isolation of holocellulose fractions of green and roasted coffee.
The holocellulose of green coffee was hydrolyzed by a novel method consisting of anhydrous sulfuric acid and 10% potassium insoluble hydroxide, which was partially solubilized on roasting and results in the following ratio of sugars: 1 L-arabinose/2D-galactose/2D-glucose/6D-mannose. Out of these sugars, the arabinose was easily acid-hydrolyzed. Other coffee constituent analyzed and determined were caffeine, trigonelline, caffeic acid, chlorogenic acid, isochlorogenic acid, and the 10 amino acids. The free amino acids disappeared in roasting. An analytical method was developed for evaluating caffeine on chromatograms [3].
In coffee pulp, condensed tannins are the major phenolic compounds, while in the seeds, phenolic compounds exist primarily as a family of esters formed between hydroxycinnamic acids and quinic acid, collectively recognized as chlorogenic acids (CGA). Green coffee seeds contain up to 14% CGA, which are present in high concentrations and have a greater influence for determining the quality of coffee and play a vital role in the formation of the coffee flavor. The various constituents along with components of coffee are shown in Table 1.

Carbohydrates
Most of the carbohydrates present, such as cellulose and polysaccharides consisting of mannose, galactose, and arabinose, are insoluble.

Lipids
The lipid fraction appears to be very stable, and its composition is given below. Linoleic acid is the predominant fatty acid, followed by palmitic acid. Lipid composition. Triacylglycerols. Diterpene esters. Diterpenes. Triterpene esters. Triterpenes (sterols). Unidentified compounds.

Acids
The volatile acids include formic acids and acetic acids, while nonvolatile acids include lactic, tartaric, pyruvic, and citric acid. Minor constituents include higher fatty acids and malonic, succinic, glutaric, and malic acids. The degradation products of citric acid are itaconic (I), citraconic (II), and mesaconic acids (III), while fumaric and maleic acids are degraded products of malic acid: Chlorogenic acids are the mainly rich acids of coffee.

Aromatic principle
The aroma profile of coffee is composed of the following notes: sweet/caramellike, earthy, sulfurous/roasty, and smoky/phenolic.

Caffeine
The best known N compound is caffeine (1,3,7-trimethylxanthine) because of its physiological effects (stimulation of the central nervous system, increased blood circulation, and respiration). It is mildly bitter in taste. 10% of the caffeine and about 6% of the chlorogenic acid are present in a coffee drink. During roasting, the caffeine level in beans is decreased. Synthetic caffeine and caffeine obtained by the decaffeination process are used by the pharmaceutical and soft drink industries. By methylation of xanthine, synthetic caffeine is obtained which is obtained from uric acid and formamide. Medicinally, caffeine is used as a CNS stimulant, usually combined with another therapeutic agent and in analgesic preparations.
Theobromine acts as diuretic and smooth muscle relaxant, but not routinely used. Theophylline is used as smooth muscle relaxant and is frequently dispensed in sustainable formulations to lower the side effects. It is also available as aminophylline (a more soluble preparation containing theophylline with ethylenediamine) and choline theophyllinate (theophylline and choline). The alkaloids may be isolated from natural sources or obtained by total or partial synthesis [5].
The purine alkaloids include caffeine, theobromine, and theophylline as shown in Figure 1. They have a limited distribution as alkaloids, but the origins are very close with those of the purine bases like adenine and guanine, fundamental components of nucleosides, nucleotides, and the nucleic acids. Caffeine is mainly consumed in the form of beverages like tea, coffee, and cola and is most widely consumed and socially accepted natural stimulants. Theophylline is much more important as a drug compound because of its muscle relaxant properties, utilized in the relief of bronchial asthma when compared to caffeine, medicinally. The major constituent of cocoa and related chocolate products is theobromine.
Out of four nitrogen atoms, two are supplied by glutamine and a third by aspartic acid. The synthesis of the nucleotides AMP and GMP is by way of IMP and XMP, and the purine alkaloids then branch away via XMP. The loss of phosphate via methylation generates the nucleoside 7-methylxanthosine, which is then released from the sugar moiety. Furthermore, successive methylation on the nitrogen gives caffeine through theobromine, while a different methylation sequence can result in the formation of theophylline ( Table 2) [6]. AMP = adenosine-5 0 -monophosphate. GMP = guanosine-5 0 -monophosphate. IMP = inosine-5 0 -monophosphate. XMP = xanthosine-5 0 -monophosphate.