Vanillin: Physiochemical Properties, Production and Uses

Vanillin: Physiochemical Properties, Production and Uses Vanillin (4-hydroxy-3-methoxybenzaldehyde) is an important flavoring agent mostly used in beverages, pharmaceutical industries, food products, etc. Naturally present as a vanillin glucoside in vanilla pods and used as an intermediate in the synthesis of some drugs. Vanillin possesses antimicrobial and antioxidant properties. In the past, production of vanillin is very expensive and a very long process. Vanillin was obtained from the oxidation of lignin, or from ferulic acid pathway or some other pathways. The chemical production of vanillin from various methods had been described. The method used in this research is High selectivity in the oxidation of Mandelic acid derivatives and in O-Methylation of Protocatechualdehyde. The starting material used here was catechol and nowadays this method is used for the industrial production of vanillin. The method used was tiresome but produces vanillin in good yield. The analysis of obtained vanillin was done by using Thin Layer Chromatography and Infrared Spectroscopy. Infrared spectrum of obtained product and reference spectrum of vanillin were compared. The similarity of melting points of the obtained product and vanillin from literatures shows that the product obtained can be confirmed as vanillin. Introduction Vanillin (4-hydroxy-3-methoxybanzaldehyde) is a main part of natural vanilla. It is a major flavouring agent used widely in the food and dairy products, beverages and pharmaceutical industries etc. It is an organic aromatic compound which contains three functional groups (aldehyde, phenol and ether). Vanillin is obtained from the beans or pods of Vanilla plant (Vanilla planifolia). Its origin is from the subtropical forests of Mexico and Central America. Mayan and Aztec civilizations are the first who discover the properties of vanilla. It was first extracted by Nicholas Theodore Gobley in 1858.1 Vanilla Planifolia Vanilla pods Vanilla beans In freshly harvested vanilla pods vanillin is binds with the ÃŽ ²-D-glycoside. Today vanillin is used in the preparation of many pharmaceutical preparations like Papaverine, Levodopa, Levomethyldopa and antimicrobial agent Trimethoprim and also for the production of herbicides and antifoaming agents. Vanillin also has properties like antioxidants and anti-tumor. Due to its aromatic properties it is widely used in the air fresheners, perfumes, incense and candle.1 Vanillin is extracted from the vanilla beans but due to its low natural production and high demand it is prepared by various synthetic methods like chemical synthesis, enzymatic synthesis etc.1 Physiochemical properties of Vanillin: Vanillin is a white crystalline powder which has a melting point about 820C. The purity is generally above 99.0% w/w on dried basis. Vanillin has a characteristic pleasant smell and taste for which it is widely used in the world. The boiling point of vanillin is about 1540C and its sublimation temperature is reported to be 700C. Vanillin starts to decompose at 1600C. Vanillin has a vapour pressure of 0.0022 hPa at 250C and 0.0017 hPa at 650C and saturated air has a concentration of 0.00029 % at 250C, corresponding to 18.0 mg/m3. The vapour density of vanillin is found to be 5.3 at 250C. Its apparent specific gravity is 0.6 kg/dm3. Specific gravity of vanillin is reported to be 1056 kg/m3 at 200C. Vanillin is soluble in water and its solubility increases with increasing temperature. Its solubility in water at 25Â °C was reported to be 10g/L. Vanillin was reported to be readily soluble in alcohol (ethanol). Also vanillin shows slight solubility in ethyl acetone, methanol, and diethyl ether. The Octanol/ Water partition coefficient was found to be 1.21 which indicates that vanillin is unlikely to bio accumulate. The pH of vanillin in water is 4.3. The phenol group of vanillin has a pKa value of 7.38. With increasing pH the molecule will lose a proton, become negatively charged and more soluble in water. Vanillin dissolves in dilute solution of alkali hydroxides.16 Production of vanillin: The production of vanillin is a very long and expensive process which involves large number of steps as well. The pollination of flowers has to be done manually as there is lack of natural pollinators. The flowers have to be pollinated within 24 hours to bear fruits. The vanilla beans require 10- 12 months to mature from the time of pollination. The matured vanilla beans are yellowish green, and are bitter in taste. The matured beans lack the characteristic vanilla flavour which only develops upon curing, which involves three steps. 1) Killing, the green beans are treated with variety of methods such as scalded with hot water, exposed to sun, wilted in the oven, scarred, treated with ethylene gas, or frozen to disrupt tissue integrity. The second method is the cheapest but most labour- intensive. In this step tissues completely lose their integrity, but still contains high amount of moisture which has to be removed by the sweating process. This step runs for 7-10 days, during moisture content of the beans reduced to 60- 70 %. After losing the moisture the beans turn dark brown in colour and start to develop their characteristic vanilla flavour. To reduce microbial spoilage and to concentrate the flavour, the moisture content were further reduced to 25- 30 %. After this step, the beans are stored in closed containers to reach their highest flavour content and then their conditioning is done either by hot water treatment or by sun drying.5 2) Process of curing and drying together requires 4-5 months. The cured beans pods may be covered with tiny crystals of vanillin. This coating is known as givre, which sometimes used as criterion for quality assessment.6 3) During the fermentation process, vanillin is released from its non-volatile glucoside by the action of vanilla ÃŽ ±-glucosidase on vanillin glucoside.3 Vanillin alone is not present in the extract of V. Plantifolia, some related phenylpropanoid (C3-C6) compounds [mainly p-hydroxybenzaldehyde(8.6%), vanillic acid (4.3%), p-hydroxybenzyl methyl ether (0.9%) ] are also present which gives the unique flavour to natural vanilla.7,8,9 However, vanillin has also been found to be present in traces amount in plants like tobacco, fruits and fruit products like orange, grapefruit, and tangerine. In mango, vanillin is present both as free vanillin and vanillyl glucoside. It is also reported to be present in elderberry juice, blueberries, orange juice, strawberries, passion fruit juice, leeches, and wines. It has also been found in diverse food products such as popcorn, extruded oat flour, apple cider brandy, commercial liquid smoke flavourings, mushrooms and chocolate.3, 10 Vanillin is added in the concentrations ranging from 1 to 26 milimolar in the food products which depend upon the nature of the product. Vanillin has a low flavor threshold value of 20Â µg/L in water at 20 Â °C.11Although more than 12000 tonnes of vanillin are produced each year only 1% of it comes from the natural sources and the rest are synthesized by chemical synthesis.12 Moreover, the high demand for vanillin and the fact that the vanillin derived from plants is relatively expensive ($1200- 1400 per kilo compared to synthetically produced which is