Nuclear Triad

Reference- India moves closer towards Nuclear Triad

A nuclear triad refers to a nuclear arsenal which consists of three components, traditionally strategic bombers (Fired from Air), intercontinental ballistic missiles (ICBMs)(Fired from Land), and submarine-launched ballistic missiles (SLBMs)(Underwater). The purpose of having a three-branched nuclear capability is to significantly reduce the possibility that an enemy could destroy all of a nation's nuclear forces in a first-strike attack; this, in turn, ensures a credible threat of a second strike, and thus increases a nation's nuclear deterrence

Cellular base stations

A macrocell is a cell in a mobile phone network that provides radio coverage served by a high power cellular base station (tower). High power implies higher amount of radiations are emitted. Generally, macrocells provide coverage larger than microcell. The antennas for macrocells are mounted on ground-based masts, rooftops and other existing structures, at a height that provides a clear view over the surrounding buildings and terrain. Macrocell base stations have power outputs of typically tens of watts.

A microcell is a cell in a mobile phone network served by a low power cellular base station (tower), covering a limited area such as a mall, a hotel, or a transportation hub. A microcell is usually larger than a picocell, though the distinction is not always clear. A microcell uses power control to limit the radius of its coverage area.
Typically the range of a microcell is less than two kilometers wide, a picocell is 200 meters or less, and a femtocell is on the order of 10 meters.

In August 2012, the Union government has told Parliament that the exposure limit of radio frequency fields (base station emissions) will be brought down to one-tenth of the existing level from September 1. Microcells, Picocells and Femtocells are viewed as an alternative to current use Macrocells

http://www.thehindu.com/news/national/article3828735.ece

ISRO gets ready for historic 100th mission - Indian Express

ISRO gets ready for historic 100th mission - Indian Express

Sounding rockets

• A sounding rocket, sometimes called a research rocket, is an instrument-carrying rocket designed to take measurements and perform scientific experiments during its sub-orbital flight.
• Sounding rockets are advantageous for some research due to their low cost and their ability to conduct research in areas inaccessible to either balloons or satellites.
• They are also used for measurements in the upper atmosphere and microgravity research
• Thumba Equatorial Launching Centre of ISRO near Thiruvanantpuram uses Sounding rockets for research. Thumba is located near Earths magnetic equator.
  
• Rockets launched from this site are helpful to probe phenomena associated with the magnetic Equator – such as the electrojet, a stream of electric current flowing in a narrow band of three degrees on either side of the magnetic Equator at a height of 100 kms.
• The sounding rockets were used by ISRO to develop and test several sub-systems for advanced rockets and evaluate more powerful propellants.

Cable digitalisation

Computers use digital signals to send and receive data. Although digital signals can only be in the state 1 (on) and 0 (off), complicated combinations of these two values are used to send/receive data. Think of this example: 
Using only binary (values 1 and 0), we can create a string of values that is interpreted by a computer to be something more meaningful. For instance, the value 11000110 00110101 10010011 00101101 is interpreted to equal 198.53.147.45 in decimal format. In conclusion, the strength of using a digital system over analog is clear. Digital signals are easier to transmit and offer less room for errors to occur. This leads to accurate data transmission that in turn leads to faster transmission rates and better productivity

Today, nearly all electronic devices we use are digital. The main reason for the change from analog to digital is because digital signals are easier to transmit and are also more reliable

In analog technology, a wave is recorded or used in its original form. So, for example, in an analog tape recorder, a signal is taken straight from themicrophone and laid onto tape. The wave from the microphone is an analog wave, and therefore the wave on the tape is analog as well. That wave on the tape can be read, amplified and sent to a speaker to produce the sound.

In digital technology, the analog wave is sampled at some interval, and then turned into numbers that are stored in the digital device. On a CD, the sampling rate is 44,000 samples per second. So on a CD, there are 44,000 numbers stored per second of music. To hear the music, the numbers are turned into avoltage wave that approximates the original wave.

The two big advantages of digital technology are:

·         The recording does not degrade over time. As long as the numbers can be read, you will always get exactly the same wave.

Analog technology comprises of natural signals like human speech. With digital technology this human speech can be saved and stored in a computer. Thus digital technology opens up the horizon for endless possible uses.

A set-top box (STB) or set-top unit (STU) is aninformation appliance device that generally contains atuner and connects to a television set and an external source of signal, turning the signal into content which is then displayed on the television screen or other displaydevice. Set-top boxes are used in cable television andsatellite television systems, to transform the signal from the cable or satellite to a form that can be used by the television set or other receiver. It also enhances the quality of signal from cable or satellite.

The Cable TV Networks (Regulation) Act will be amended

 The digital technology will offer improved quality of transmission and greater choice of content, albeit at a higher cost to consumers.

"This will benefit the entire broadcasting industry, both economically, and from the point of view of content," 

The broadcasting industry has been suffering from poor bandwidth of analogue cable, which will be resolved with digitisation, he said, adding this will also plug leakages in the revenue system by solving the problem of under declaration of subscribers in the analogue cable system

Touchscreen

There are three basic systems that are used to recognize a person's touch:

• Resistive
• Capacitive
• Surface acoustic wave

The resistive system consists of a normal glass panel that is covered with a conductive and a resistive metallic layer. These two layers are held apart by spacers, and a scratch-resistant layer is placed on top of the whole setup. An electrical current runs through the two layers while the monitor is operational. When a user touches the screen, the two layers make contact in that exact spot. The change in the electrical field is noted and the coordinates of the point of contact are calculated by the computer. Once the coordinates are known, a special driver translates the touch into something that the operating system can understand, much as a computer moouse driver translates a mouse's movements into a click or a drag.

In the capacitive system, a layer that stores electrical charge is placed on the glass panel of the monitor. When a user touches the monitor with his or her finger, some of the charge is transferred to the user, so the charge on the capacitive layer decreases. This decrease is measured in circuits located at each corner of the monitor. The computer calculates, from the relative differences in charge at each corner, exactly where the touch event took place and then relays that information to the touch-screen driver software. One advantage that the capacitive system has over the resistive system is that it transmits almost 90 percent of the light from the monitor, whereas the resistive system only transmits about 75 percent. This gives the capacitive system a much clearer picture than the resistive system.

On the monitor of a surface acoustic wave system, two transducers (one receiving and one sending) are placed along the x and y axes of the monitor's glass plate. Also placed on the glass are reflectors -- they reflect an electrical signal sent from one transducer to the other. The receiving transducer is able to tell if the wave has been disturbed by a touch event at any instant, and can locate it accordingly. The wave setup has no metallic layers on the screen, allowing for 100-percent light throughput and perfect image clarity. This makes the surface acoustic wave system best for displaying detailed graphics (both other systems have significant degradation in clarity).

A resistive system registers a touch as long as the two layers make contact, which means that it doesn't matter if you touch it with your finger or a rubber ball. A capacitive system, on the other hand, must have a conductive input, usually your finger, in order to register a touch. The surface acoustic wave system works much like the resistive system, allowing a touch with almost any object -- except hard and small objects like a pen tip.

3G vs 4G

3G is currently the world’s best connection method when it comes to mobile phones, and especially mobile Internet. 3G stands for 3rd generation as its is just that in terms of the evolutionary path of the mobile phone industry. 4G means 4th generation. This is a set of standard that is being developed as a future successor of 3G in the very near future.

The biggest difference between the two is in the existence of compliant technologies. There are a bunch of technologies that fall under 3G, including WCDMA, EV-DO, and HSPA among others. Although a lot of mobile phone companies are quick to dub their technologies as 4G, such as LTE, WiMax, and UMB, none of these are actually compliant to the specifications set forth by the 4G standard. These technologies are often referred to as Pre-4G or 3.9G.

4G speeds are meant to exceed that of 3G. Current 3G speeds are topped out at 14Mbps downlink and 5.8Mbps uplink. To be able to qualify as a 4G technology, speeds of up to 100Mbps must be reached for a moving user and 1Gbps for a stationary user. So far, these speeds are only reachable with wired LANs.

Another key change in 4G is the abandonment of circuit switching. 3G technologies use a hybrid of circuit switching and packet switching. Circuit switching is a very old technology that has been used in telephone systems for a very long time. The downside to this technology is that it ties up the resource for as long as the connection is kept up. Packet switching is a technology that is very prevalent in computer networks but has since appeared in mobile phones as well. With packet switching, resources are only used when there is information to be sent across. The efficiency of packet switching allows the mobile phone company to squeeze more conversations into the same bandwidth. 4G technologies would no longer utilize circuit switching even for voice calls and video calls. All information that is passed around would be packet switched to enhance efficiency.

E- Ticket v/s I-Ticket

When ordering tickets online in India, you can opt between getting an E-Ticket or an I-Ticket. The main difference between an E-Ticket and an I-Ticket is how you get the ticket. With an E-Ticket, you receive an electronic form that you print and carry with you while with an I-Ticket, the actual ticket is produced and then sent to you via a courier.

The most direct consequence for this is the difference between the booking date and actual travel date. With an I-Ticket, you need to book at least two days before the actual date of travel to give time for the tickets to be mailed to you. Since you just print the E-Ticket, there is no associated delays. You can even book on the day of travel and just bring the printout with you.

But to ensure that the person bringing the E-Ticket is the one that booked it, you need to bring the identification papers you supplied when booking. This is used to confirm your identity. With an I-Ticket, you need not present identification papers as the tickets would serve that purpose.

You also need to consider that an I-Ticket is more expensive due to the cost of delivering the ticket to your location. The only additional cost of an E-Ticket is the cost of printing it which so small to be considered significant. In general, given the same destinations, an E-Ticket would usually cost less than an I-Ticket.

Lastly, you need to consider the situation where you might need to cancel the ticket for whatever reason. With an E-Ticket, cancellation is very easy and takes effect instantly. Not so with an I-Ticket, especially when the tickets have been sent. The process is a bit more difficult and time consuming not to mention the fact that you would get less of your money back

Television Display Types (In Short) from Reuters

http://blog.thomsonreuters.com/wp-content/uploads/2012/04/TV-Types.jpg

Hydrualic fracturing from Reuters

http://blog.thomsonreuters.com/wp-content/uploads/2012/05/Fracking.jpg

God's particle

From Reuters- http://blog.thomsonreuters.com/wp-content/uploads/2011/12/higgs-boson.jpg

Also read for more details- http://www.indianexpress.com/news/god-exists/970403/

"Space Tornado" or solar tornadoes

Huge 'solar tornadoes' 1000 miles wide captured heating sun's atmosphere to millions of degrees centigrade - and find could power 'clean' reactors on Earth

A space tornado can actually result from solar windstorms that produce funnel-shaped clouds of charged particles. The solar wind blows at 600,000 to 2,000,000 miles per hour.


solar tornadoes carry the energy from the energy reservoir below the Sun's surface, called the convection zone, to the outer atmosphere in the form of magnetic waves.


One of the major problems in modern astrophysics is why the atmosphere of a star, like our own Sun, is considerably hotter than its surface?


It is understood that the energy originates from below the Sun's surface, but how this massive amount of energy travels up to the solar atmosphere surrounding it is a mystery. It is believed that we have found evidence in the form of rotating magnetic structures -- solar tornadoes -- that channel the necessary energy in the form of magnetic waves to heat the magnetized solar plasma. It is hoped that the process could be replicated here on Earth one day to energize plasma in tokamak that are believed to be a future device to produce completely clean energy.


Scientists viewed the solar tornadoes in the outer atmosphere of the Sun, stretching thousands of miles from the giant star's surface by using both satellite and ground-based telescopes. They then created 3D-layered sequence of images of the tornadoes and simulated their evolution with state-of-the-art numerical codes using the magnetic imprints detected by their high-resolution, cutting-edge telescopes.

Above, Telescope images form a tower showing how 'solar tornadoes' work

 A simulated image of solar tornado

Solar Flares from Reuters

New light shed on explosive solar activity

New light shed on explosive solar activity

Big data

In information technology, big data is a loosely-defined term used to describe data sets so large and complex that they become awkward to work with using on-hand database management tools. 
"Big data" is a term applied to data sets whose size is beyond the ability of commonly used software tools to capture, manage, and process the data within a tolerable elapsed time.
Examples include web logs, RFID, sensor networks, social networks, social data (due to the social data revolution), Internet text and documents, Internet search indexing, call detail records, astronomy, atmospheric science, genomics, biogeochemical, biological, and other complex and often interdisciplinary scientific research, military surveillance, medical records, photography archives, video archives, and large-scale e-commerce.

LCD, LED and Plasma Display- comparison

LCD Display Technology

Most basically LCDs produce the image you see by blocking or emitting the light from a backlight using liquid crystals sandwiched in between two glass plates.

An LCD display is made up of a thin layer of liquid crystals arranged in a matrix (or grid) of a million or more pixels (picture elements), This layer is sandwiched between the two glass plates, which are covered in a matrix of electrodes and transistors (electronic switches), each coated with a polarising filter. The two polarising layers only allow light vibrating in one direction to pass through them, one allows horizontally vibrating light through and the other passes vertically vibrating light.

The light source in an LCD is its backlight so this unpolarized light becomes vertically polarized as it passes through the first polarizing filter at the back of the display. The other polarizing layer on the front sheet of glass is horizontally polarized, so ordinarily the now vertically polarized light coming from backlight can't pass through it. The role of the liquid crystal layer in the middle of the display is to rotate the vertically polarized light travelling through it by ninety degrees so it can pass through the front, horizontally polarized filter. By varying the voltage applied to the liquid crystal sub-pixels the amount they twist the light changes, allowing more light of each colour though as a greater voltage is applied.

Each pixel is made up of three sub-pixels aligned to a colour filter for each of the primary colours; red, green and blue. Individual pixel colours are produced by the combination of the primary colours produced by each sub pixel, with the pixel's overall brightness is produced by the sub-pixels relative intensities. Many thousands of these pixel units operating together in the display combine to produce the image you see.

What is LED TV?

The first thing to know about LED (Light Emitting Diode) TVs is that they are simply LCD TVs with a different kind of backlighting. The screen remains the same but LEDs are used for backlighting in place of Cold Cathode Fluorescent Lamps (CCFL) that are found in most LCD TVs.

The LEDs can come in two forms, Dynamic RGB LEDs which are positioned behind the panel, or white Edge-LEDs positioned around the rim of the screen which use a special diffusion panel to spread the light evenly behind the screen.

RGB Dynamic LED TV

This method of backlighting allows dimming to occur locally creating specific areas of darkness on the screen. This means you see truer blacks and much higher dynamic contrast ratios.

(Image courtesy of Sony)

Edge-LED TV

This method of backlighting allows for LED TVs to become extremely thin. The light is diffused across the screen by a special panel which produces a superb uniform colour range across the screen.

(Image courtesy of Sony)

Currently LEDs are not small enough to be used for individual pixels in domestic televisions, and so the use of true LED TVs is restricted to much larger screens in places such as sport stadia or above 40' sizes. There are some great benefits to choosing an LED TV over a standard LCD TV.

• Improved brightness and contrast levels, with deeper blacks.

• The use of Edge-LED lighting allows the TV to be thinner than standard LCD TVs.

• LED TVs can consume up to 40% less power than a LCD TV of similar size.

• They can offer a wider colour gamut, especially when RGB-LED backlighting is used.

LED TVs are also more environmentally friendly due to there being no mercury used during manufacture. Further longevity of LED TV's is claimed to be better.

Future of LED TV

The future of LED TV is expected to focus on the use of "Quantum Dots" as light emitting diodes to create QD-LED displays and QD-WLED (White LED) displays, which operate in a similar fashion to OLED displays in that light is supplied on demand. Quantum dots are valued for displays, because they emit light in very specific gaussian distributions. This can result in a display that more accurately renders the colors than the human eye can perceive. Quantum dots also require very little power since they are not color filtered. Research is still ongoing for this technology, and it is not expected to be put into use on commerical TVs until at least 2012.

How plasma displays work (little technical, difficult to simplify)

A panel typically has millions of tiny cells in compartmentalized space between two panels of glass. These compartments, or "bulbs" or "cells", hold a mixture of noble gases and a minuscule amount of mercury. Just as in the fluorescent lamps over an office desk, when the mercury is vaporized and a voltage is applied across the cell, the gas in the cells form a plasma. With flow of electricity (electrons), some of the electrons strike mercury particles as the electrons move through the plasma, momentarily increasing the energy level of the molecule until the excess energy is shed. Mercury sheds the energy as ultraviolet (UV) photons. The UV photons then strike phosphor that is painted on the inside of the cell. When the UV photon strikes a phosphor molecule, it momentarily raises the energy level of an outer orbit electron in the phosphor molecule, moving the electron from a stable to an unstable state; the electron then sheds the excess energy as a photon at a lower energy level than UV light; the lower energy photons are mostly in the infrared range but about 40% are in the visible light range. Thus the input energy is shed as mostly heat (infrared) but also as visible light. Depending on the phosphors used, different colors of visible light can be achieved. Each pixel in a plasma display is made up of three cells comprising the primary colors of visible light. Varying the voltage of the signals to the cells thus allows different perceived colors.

Plasma Technology	LCD Technology	LED Technology
Strengths • Great black levels • Produce exceptional color (up to 16.77 million) • Good for dark rooms • Cheapest of 3 TV types • Great for 3D	Strengths • Great in bright rooms • High native resolution • More energy efficient than Plasma	Strengths • Produce blacks similar to Plasma • Amazingly thin • Energy efficient • Good for 3D
Weaknesses • Lower brightness than LCD/LED • Glass screens reflect light • Not slim or light as LCD/LED	Weaknesses • Do not produce true black • Narrower viewing angle than Plasma • Handles fast motion less efficient than Plasma • More expensive than Plasma	Weaknesses • Models with glass screens reflect light • Narrower viewing angle than Plasma • Not ideal for videogames • Most expensive TV technology

LEDs Magazine - Benefits and drawbacks of LEDs

LEDs Magazine - Benefits and drawbacks of LEDs

OLED: Components, Working, Advantages and Disadvantages

OLED Components (components and working is little technical, so can be neglected)

Like an LED, an OLED is a solid-state semiconductor device that is 100 to 500 nanometers thick or about 200 times smaller than a human hair. OLEDs can have either two layers or three layers of organic material; in the latter design, the third layer helps transport electrons from the cathode to the emissive layer. In this article, we'll be focusing on the two-layer design.

An OLED consists of the following parts:

Substrate (clear plastic, glass, foil) - The substrate supports the OLED.

Anode (transparent) - The anode removes electrons (adds electron "holes") when a current flows through the device.

Organic layers - These layers are made of organic molecules or polymers.

Conducting layer - This layer is made of organic plastic molecules that transport "holes" from the anode. One conducting polymer used in OLEDs is polyaniline.

Emissive layer - This layer is made of organic plastic molecules (different ones from the conducting layer) that transport electrons from the cathode; this is where light is made. One polymer used in the emissive layer is polyfluorene.

Cathode (may or may not be transparent depending on the type of OLED) - The cathode injects electrons when a current flows through the device.

How do OLEDs Emit Light?

OLEDs emit light in a similar manner to LEDs, through a process called electrophosphorescence.

The process is as follows:

1. The battery or power supply of the device containing the OLED applies a voltage across the OLED.
2. An electrical current flows from the cathode to the anode through the organic layers (an electrical current is a flow of electrons). The cathode gives electrons to the emissive layer of organic molecules. The anode removes electrons from the conductive layer of organic molecules. (This is the equivalent to giving electron holes to the conductive layer.)
3. At the boundary between the emissive and the conductive layers, electrons find electron holes. When an electron finds an electron hole, the electron fills the hole (it falls into an energy level of the atom that's missing an electron). When this happens, the electron gives up energy in the form of a photon of light.
4. The OLED emits light.
5. The color of the light depends on the type of organic molecule in the emissive layer. Manufacturers place several types of organic films on the same OLED to make color displays.
6. The intensity or brightness of the light depends on the amount of electrical current applied: the more current, the brighter the light.

OLEDs offer many advantages over both LCDs and LEDs:

·        OLED substrates can be plastic rather than the glass used for LEDs and LCDs.

·        OLEDs are brighter than LEDs. Because the organic layers of an OLED are much thinner than the corresponding inorganic crystal layers of an LED, the conductive and emissive layers of an OLED can be multi-layered.

·         Also, LEDs and LCDs require glass for support, and glass absorbs some light. OLEDs do not require glass.

·        OLEDs do not require backlighting like LCDs. LCDs work by selectively blocking areas of the backlight to make the images that you see, while OLEDs generate light themselves.

·        Because OLEDs do not require backlighting, they consume much less power than LCDs (most of the LCD power goes to the backlighting).

·        OLEDs are easier to produce and can be made to larger sizes. Because OLEDs are essentially plastics, they can be made into large, thin sheets. It is much more difficult to grow and lay down so many liquid crystals.

·        OLEDs have large fields of view, about 170 degrees. Because LCDs work by blocking light, they have an inherent viewing obstacle from certain angles. OLEDs produce their own light, so they have a much wider viewing range.

Problems with OLED 

·        Lifetime - While red and green OLED films have longer lifetimes (46,000 to 230,000 hours), blue organics currently have much shorter lifetimes (up to around 14,000 hours[source: OLED-Info.com]).

·        Manufacturing - Manufacturing processes are expensive right now.

·        Water - Water can easily damage OLEDs.

Comparing LCD and Traditional CRT monitors

Characteristics	LCD Displays	CRT Monitors
Physical size	Thin, compact and lightweight. Takes up less space.	Bulky, heavier and takes up more space.
Brightness	LCDs are backlit and have different levels of brightness and capable of producing very bright images and shows extremely uniform brightness. Very suitable for environments that are brightly lit.	Fairly bright, but not as bright as LCDs. Brightness is not a necessary concern with CRTs. Not appropriate for brightly lit conditions.
Power Consumption and Heat	Energy efficient. Consume less electricity than a CRT and produce little heat.	Use more power and produce more heat than a LCD.
Radiation Emission	Emit considerably lesser radiation.	Emit harmful radiation.
Display Size	Advance LCD technology make colour LCD monitors comparable in screen size to CRT monitors	Wide ranges of screen sizes.
Colours	Capable of displaying hundreds or thousands of colours, but newer ones are capable of unlimited colours.	Capable of displaying unlimited colours.
Resolution	Works best at its own native resolution. The native resolution is generally the highest resolution that the LCD can display. Changing to other resolutions require adjusting procedures which can cause considerable deterioration of the image.	Capable of displaying multiple video resolutions, each with the same good quality. Highest pixel resolution was available for operation.
Viewing Angle	Restricted viewing angles. Needed to be viewed in front to have a better view. Not much of an issue for newer LCDs.	Viewable from almost every angle.
Price	More expensive but saves more electricity.	Less expensive but more electricity consuming.

Food preservation

The basic idea behind all forms of food preservation is either:

• ·         To slow down the activity of disease-causing bacteria
• ·         To kill the bacteria altogether

I­n certain cases, a preservation technique may also destroy enzymes naturally found in a food that cause it to spoil or discolor quickly. An enzyme is a special protein that acts as a catalyst for a chemical reaction, and enzymes are fairly fragile. By increasing the temperature of food to about 150 degrees Fahrenheit (66 degrees Celsius), enzymes are destroyed. A food that is sterile contains no bacteria. Unless sterilized and sealed, all food contains bacteria. 

Different techniques used for preservation.

Refrigeration and Freezing

 In the case of refrigeration, the idea is to slow bacterial action to a crawl so that it takes food much longer  to spoil. In the case of freezing, the idea is to stop bacterial action altogether. Frozen bacteria are completely inactive.

Refrigeration and freezing are used on almost all foods: meats, fruits, vegetables, beverages, etc. In general, refrigeration has no effect on a food's taste or texture. Freezing has no effect on the taste or texture of most meats, has minimal effects on vegetables, but often completely changes fruits (which become mushy). Refrigeration's minimal effects account for its wide popularity.

Canning Food

 In canning, you boil the food in the can to kill all the bacteria and seal the can (either before or while the food is boiling) to prevent any new bacteria from getting in. We generally think of "cans" as being metal, but any sealable container can serve as a can. One problem with canning, and the reason why refrigeration or freezing is preferred to canning, is that the act of boiling food in the can generally changes its taste and texture (as well as its nutritional content).

Dehydrating Food 

Water content in the food is removed. Since most bacteria die or become completely inactive when dried, dried foods kept in air-tight containers can last quite a long time. e.g.

·         Powdered milk

·         Dried fruits and vegetables

·         Powdered soups and sauces

·         Pasta

·         Instant rice

Normally, drying completely alters the taste and texture of the food.

Freeze-Drying

Freeze-drying is a special form of drying that removes all moisture and tends to have less of an effect on a food's taste than normal dehydration does.

In freeze-drying, food is frozen and placed in a strong vacuum. The water in the food then sublimates -- that is, it turns straight from ice into vapor. Freeze-drying is most commonly used to make instant coffee, but also works extremely well on fruits such as apples.

Salting and Pickling

Salting, especially of meat, is an ancient preservation technique. The salt draws out moisture and creates an environment inhospitable to bacteria. If salted in cold weather (so that the meat does not spoil while the salt has time to take effect), salted meat can last for years.

Pickling was widely used to preserve meats, fruits and vegetables in the past, but today is used almost exclusively to produce "pickles,". Pickling uses the preservative qualities of salt (see above) combined with the preservative qualities of acid, such as acetic acid (vinegar). Acid environments inhibit bacteria.

Pasteurizing, Fermenting, Carbonating

Pasteurizing

It involves heating the food to a high enough temperature to kill certain (but not all) bacteria and to disable certain enzymes, and in return you are minimizing the effects on taste as much as you can. Commonly pasteurized foods include milk, ice cream, fruit juices.

Fermenting

Fermentation uses bacteria like yeast to produce alcohol. Alcohol is a good preservative because it kills bacteria. When you ferment grape juice you create wine, which will last quite a long time (decades if necessary) without refrigeration.

Carbonating

Carbonated water is water in which carbon dioxide gas has been dissolved under pressure. By eliminating oxygen, carbonated water inhibits bacterial growth. Carbonated beverages (soft drinks) therefore contain a natural preservative.

Chemical Food Preservation

There are three classes of chemical preservatives commonly used in foods:

·         Benzoates (such as sodium benzoate)

·         Nitrites (such as sodium nitrite)

·         Sulphites (such as sulphur dioxide)

Another common preservative is sorbic acid. All of these chemicals either inhibit the activity of bacteria or kill the bacteria.

Food Irradiation

Nuclear radiation is able to kill bacteria without significantly changing the food containing the bacteria. So if you seal food in plastic and then radiate it, the food will become sterile and can be stored on a shelf without refrigeration. Unlike canning, however, you do not significantly change the taste or texture of the food when you irradiate it.