Tag Archives: Temperature

Chemicals imparting different tastes to whiskies

All the wines and spirits contain alcohol in different proportions. Alcohols are organic compounds with an hydroxyl (OH) group. There are thousands of compounds in this category. But the alcohol which wines and distillates of fermented matter obtained from the carbohydrates is Ethanol or ethyl alcohol with chemical formula written as C2H5-O-H. Compare it to formula of water H-O-H. If you replace one hydrogen atom in water with ethyl (C2H5) group, you get ethyl alcohol. Introduction of non polar ethyl group, reduces the polarity of the alcohol in comparison to water. This causes the alcohol to be the best solvent for many less polar organic compounds. In fact alcohol is used as a solvent in organic work.

So if the wine, whisky, rum, vodka etc were only ethyl alcohol, they would all taste the same. So where does the different taste come from? The answer lies in the variety of grain used for fermentation, the wood used for drying the fermented grain and the wooden barrels made of wood from selective trees, duration of ageing in these barrels as well as the temperature and humidity.

Whiskey is produced using barley. The grain is soaked in water to release the sugars. And yeast is applied to ferment the sugars and breakdown it into lower sugars and finally to ethyl alcohol. The spirit is then distilled to concentrate the alcohol. The distillates are then kept for years in the oak barrels for ageing before bottling.

During firing to dry the soaked mass, the aroma of wood fuel enters into the ground mass. Then thousands of organic compounds are leaches by alcohol from wood during ageing process. All these contribute a unique aroma and taste to whiskies.

Organic compounds belonging to classes namely ketones, esters, phenolic categories are mainly responsible for the distinct taste. Some of these are given below:

Whiskey lactones : These are cis and trans 3-methyl-4-Octanolide. These are ketones and are imported from Oak wood. Trans isomer imparts woody, coconut flavor while cis isomer imparts strong spicy coconut aroma.

Aldehydes: Syringaldehyde and vanillin. Syringaldehyde lends a spicy Woody aroma while vanillin gives vanilla tone. Furfural almonds like grainy flavor and hexanal offers grassy notes.

Esters: Ethyl hexanoate gives sweet apple flavor. Isoamyl acetate gives banana like flavor. Since many esters impart cloudiness to whiskey they are removed chill filtering.

Phenolic compounds: Guaiacol and eugenol impart smoky flavor and bitter taste. Cresols enter the grains when they are peat fired imparting medicinal smell.

Many other compounds like Beta  demascenone and phenethyl alcohol give floral notes. Diacetyl adds a buttery taste. Many sulphur compounds also contrite the flavor.

For more graphical description see the illustration

Ice hides memories of past climate!!!!

Almost all the elements in the universe are composed of atoms siblings though are chemically equivalent but have slightly different weight. Atom is composed of equal number of electrons and protons to make it electrically neutral and stable. There are also neutrons which are electrically neutral but have weight almost equal to the proton. Protons and neutrons reside in the centre of atom and called jointly nucleus. This is due to the different numbers of neutrons in these atoms. More the neutrons more shall be the weight of the isotope.
Oxygen has two prominent isotopes. The lighter one contains 8 neutrons and the heavier one contains 10 neutrons this is exactly 2 neutron heavier. The ratio of the heavier atoms to the lighter ones is 1:500 or 0.2%. The number and ratio of the oxygen isotopes is constant if water was present at one place only. But the distribution changes due to physical and biological processes. These two phenomena fractionated the distribution. The oxygen atoms are labeled 18O and 16O.
Since heavier oxygen has lower tendency to evaporate than the lighter and higher tendency to precipitate, the distribution changes continuously with the movement and phase changes of the water.
Originally in the sea water there was a given ratio. Now suppose sun heats the sea and evaporation takes place initiating the water cycle. But notice, the ratio of heavier atoms to lighter atoms will change both is the sea water left behind as well as the vapours. Sea water will become richer in heavier isotope and vapours poorer. Now these vapours rise and starts migrating towards the poles. Temperature gradually begins to fall triggering the precipitation but again further fractionation will take place. In the beginning, some of the heavier atoms will precipitate thus further depleting the pole ward moving water vapours in heavier atoms. So when the snow will start falling, it will be containing the least numbers of heavier atoms.
The snow will settle down. Future years will bring more snow, thus snowflakes shall begin to compact at the lower layers. Snowflakes contain roughly 80% air. After compaction, the air will be expelled and firn will form having only about 20% air. Ultimately lowest layers shall become ice containing only 2% air or less. Layer upon layer will build.
The snow precipitated in the relatively warmer climates shall have more heavier oxygen than the snow precipitated in cooler climates. This phenomena is used to measure the temperature at which a particular layer was deposited. This provides a tool for temperature records in the history of the earth.
For this purpose, scientists take out the continuous cylindrical cores of the ice and measure the abundance of heavier oxygen atoms relative to the lighter ones using ratio recording mass spectrometer and plot this against depth. From the calibration curves with temperature, scientists are able to measure the temperature records.
Knowing the past climatic history of the earth can help in understanding the ice ages epochs, chemical and biological reactions and thus the abundance or otherwise of minerals like petroleum.
Thus the ice deposited over millions of years preserves the memories of the climate in the past. They have been able to recreate the 4 million years record of temperatures.

My trysts with Fog

English: Fog in Wayanad

In my younger days at Chandigarh in North India, we experienced Foggy days and nights during winter season. Firstly, it begins to lurk over the fields which are irrigated and water is not dried. Along with the smoke which rises from the burning hearths in the huts of villages, it stays suspended low over the fields and homes.

Afterwards, when temperature drops further it begins to engulf whole region rising from the water bodies like ponds and rivers. With breeze breaking, it floats here and there. Visibility begins to reduce and the people walking a certain distance suddenly seem to emerge as wraiths and then suddenly disappearing.

For several years I have lived in Mumbai away from my home town. There temperatures never drop and weather is moderate and this fog phenomena is is rarely seen. Instead during the months of January sometimes smog surrounds all the region due to high pollution and chemical industries.

Now I have returned to North, to Dehradun. It is a valley and never a strong breeze blows. But temperatures drop very low, even then days are very sunny and bright. My first encounter with the dreaded fog which holds North India to ransom took place while traveling in the car in the very early morning from Dehradun to Chandigarh.

Fog is very treacherous. Dehradun weather was very clear but as soon as we reached a place called Selaqui about 20 kilometers towards west, nothing was visible. Whatever vehicles were there on the road, were trotting with emergency lights blinking. We followed a truck which became our guide but it also halted somewhere. Our Polo car announced by a alarm bell that the temperature has dropped below 4C.

We proceeded slowly. Keeping tabs on the white divider strips of the road. When we were nearing Nahan, suddenly the fog vanished and sun came out. It seemed that our eye sights have been restored suddenly.

We crossed the hills comfortably. But as soon as we entered the plains near Kala Amb again the it was all fog. There were burst of water jets from the trees when they shook due to passing of high vehicles. We heaved a sigh of relief after reaching our destination.