CHEMISTRY OF TASTE AND AROMA COMPOUNDS IN TEA AND COFFEE

KUSH VERMA (15/PFT/001)

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PRESENTED BY

Growing Conditions• A hot, moist Climate• Temperature ranging from 10 – 30 degrees centigrade• Average yearly rain fall, around 200mm• Ground level of between 200-600m above sea level

Types of Tea

• Black Tea• Green Tea• White Tea• Oolong Tea

Health & Benefits of Tea• Higher antioxidant capacity than fruits & vegetables.• Help to relax on human• Assist in natural immune• Response to infection• Reduce risk of heart diseases, cancers, cholesterol

level, higher blood pressure.• Reduce eye fatigue.

Product Life Cycle

• Now they are in Maturity Stage in their product life Cycle.

Tea Processing Cycle

Plucking

It is a process of harvesting and collecting tea leaves.

Before the tea plucking we have to maintain foliage & tipping.

There are mainly 3 types of Plucking Systems,

– Scale leaf plucking– Fish leaf plucking– Mother leaf plucking

Mechanical Plucking

Reasons Shortage of manual labors . Low efficiency in manual plucking.

High labor wages.

Additional man power equipments.

During peak flush period necessitate mechanical .

Limitation Decline in leaves Quality.

Difficulty in using high sloppy land.

Difficulty to repair .

•Mechanical Plucking System can use when there is a scarcity of pluckers during July to September.

Withering

• The primary aims of withering are, to reduce the moisture content of the leaf and to soften it.

• the tea leaves are spread out on a large tray of wire mesh, and hot air blowers are used to heat the leaf and drive the moisture out.

• Withering duration is dependent on temperature and humidity and could range from 18 to 24 hours.

• At this point, the leaf has become limp and turned into a darker shade of green.

Rolling

• It is a process where rollers are used to rupture the cell walls of the withered leaves for oxidation of the polyphenols in the presence of oxygen from air.  

• There are two methods used by manufacturers,– Orthodox– CTC

Fermentation

• It is the process of oxidation of leaves.• The mechanical aspect involves spreading out of the

leaves macerated by rolling a layer 5-8 cm thick, for 45 minutes to 3 hours, depending on the quality of the leaves.

• In here pay more attention to humidity & Temperature.

TEA

• Tea is an aromatic beverage commonly prepared by pouring hot or boiling water over cured leaves of the Camellia sinensis, an evergreen shrub native to Asia. After water, it is the most widely consumed drink in the world. There are many different types of tea; some teas, like Darjeeling and Chinese greens, have a cooling, slightly bitter, and astringent flavour, while others have vastly different profiles that include sweet, nutty, floral or grassy notes.

CHEMICAL CONSTITUENTS OF TEA

• The chemical composition of tea leaves has been thoroughly studied. The main constituents of tea leaves belong to the polyphenol group accounting for 25 to 35% on a dry weight basis (Balentine, 1997; Hara et al., 1995d). The polyphenols (Mukhtar et al., 2000) in tea mainly include the following six groups of compounds: flavonol's, hydroxyl-4-flavanols, anthocyanins, flavones, flavonol's and phenolic acids

AROMA COMPOUNDS OF TEA

• Aroma is one of the critical aspects of tea quality which can determine acceptance or rejection of a tea before it is tasted. All the data reported so far shows that more than 630 compounds have been reported responsible in tea aroma.

• Carotenoids include β-carotene, lutein, zeaxanthin, neoxanthin, xanthophyll, and lycopene, and more have been identified as precursors for many tea flavors. Many of them play key roles in deciding the quality of tea.

TASTE COMPOUNDS OF TEA• Taste of food is mainly composed of five basic sensations;

that is, sweetness, astringency, sourness, bitterness and umami).

• polyphenols was necessary for the expression of reasonable amounts of tangy astringency.

• The gallated tea flavonols are related to astringency and also to the bitterness taste; the non-gallated tea flavonols are related to bitterness, however, are not related to or only slightly related to the astringent taste of black tea infusion. Among theoflavins (TFs), theoflavin is less astringent. The contribution of TF-digallate and mono-gallate to astringency is 6.4 and 2.2 times to that of the aflavin.

COFFEE

• Coffee is a brewed drink prepared from roasted coffee beans, which are the seeds of berries from the Coffea plant.

• Coffee is slightly acidic and can have a stimulating effect on humans because of its caffeine content. Coffee is one of the most popular drinks in the world.

CHEMICAL CONSTITUENTS OF COFFEE

• The nonvolatile fraction of green coffee is composed primarily of water, carbohydrates and fiber, proteins and free amino acids, lipids, minerals, organic acids, chlorogenic acids, trigonelline, and caffeine . Of these compounds found in green coffee, chlorogenic acids, caffeine, trigonelline, soluble fiber, and diterpenes from the lipid fraction are most. likely to be bioactive, and they may also be important contributors to the beverage flavor after roasting

AROMA COMPOUNDS OF COFFEE• Coffee aroma is perceived by two different mechanisms. It can either be sensed

nasally via smelling the coffee through the nose or retronasally. Retronasal perception occurs when the coffee is either present in the mouth or has been swallowed and aromatic volatile compounds drift upward into the nasal passage.

• The number of aromatic compounds found in coffee increases every year. Today the number is well over 800, and as our analytical methods become more precise, more will be uncovered. Yet, the perception of coffee aroma is dependent upon both the concentration of the compound and its odour threshold. With that said, understanding coffee aroma is not as difficult as understanding how over 800 coffee elements interact with the olfactory epithelium. It is probable that a relatively small group of compounds that share both a high concentration and a low odor threshold make up the fragrance we know as coffee aroma. This article will discuss the recent research that has narrowed in on these aroma impact compounds.

CONTINUE….• Illy listed the following chemical processses that affect the development

of volatile compounds in coffee:1) Maillard or non-enzymatic browning reaction between nitrogen containing substances, amino acids, proteins, as well as trigonelline, serotonine, and carbohydrates, hydroxy-acids and phenols on the other.2) Strecker degradation.3) Degradation of individual amino acids, particularly, sulfur amino acids, hydroxy amino acids, and proline.4) Degradation of trigonelline.5) Degradation of sugar.6) Degradation of phenolic acids, particularly the quinic acid moiety.7) Minor lipid degradation.8) Interaction between intermediate decomposition products.

TASTE COMPOUNDS OF COFFEE• Coffees taste is perceived mostly on the tongue by the taste buds.• SWEET- The first sensation humans develop, In coffee, a number

of sugars (usually called polysaccharides or carbohydrates) exist and are perceived as sweetness. Sweetness in coffee is directly related to the ripeness of the coffee when picked.

• SOUR- We perceive acid on the tongue as the flavor sour. The term sour in coffee is related to an excess of acetic acid or tartaric acid due to an over fermentation or unripe coffee. However, our sour receptors also perceive desirable acidity characteristics of fine coffees.

• SALTY- Frequently in coffee tasting a saltiness can appear which is unrelated to mineral content. Salty flavor is a taste defect in coffee and is usually related to mineral contamination during processing, especially drying coffee on the ground.

• BITTER- A common alkaloid in coffee is caffeine. Bitterness is essential to coffee's flavor.

• SAVORY- In the early 1900s, a Japanese Scientist established the taste sensation of umami (literally: deliciousness). Glutamic acid is the most common amino acid in food protein. Savoriness in coffee has developed due to yeast activity during fermentation phase of processing.

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