The major factors responsible for extending the shelf life of fruits and vegetables include: careful harvesting so as not to injure the product, harvesting at optimal horticultural maturity for intended use, and good sanitation When these are practiced, the implementation of optimum storage conditions through modified atmospheres can be quite effective at maximizing the shelf life and quality of the product.

A modified atmosphere can be defined as one that is created by altering the normal composition of air (78% nitrogen, 21% oxygen, 0.03% carbon dioxide and traces of noble gases) to provide an optimum atmosphere for increasing the storage length and quality of food/produce . This can be achieved by using controlled atmosphere storage (CAS) and/or active or passive modified atmosphere packaging (MAP). Under controlled atmospheric conditions, the atmosphere is modified from that of the ambient atmosphere, and these conditions are maintained throughout storage. Examples of this type of storage and the commercial systems available are MAP uses the same principles as CAS; however, it is used on smaller quantities of produce and the atmosphere is only initially modified. Active modification occurs by the displacement of gases in the package, which are then replaced by a desired mixture of gases, while passive modification occurs when the product is packaged using a selected film type, and a desired atmosphere develops naturally as a consequence of the products' respiration and the diffusion of gases through the film . The numerous film types used in MAP and some commercially available MAP systems are listed in Table .

Oxygen, CO2 , and N2 , are most often used in MAP/CAS (Parry 1993; Phillips 1996). Other gases such as nitrous and nitric oxides, sulphur dioxide, ethylene, chlorine (Phillips 1996), as well as ozone and propylene oxide (Parry 1993) have been suggested and investigated experimentally. However, due to safety, regulatory and cost considerations, they have not been applied commercially. These gases are combined in three ways for use in modified atmospheres: inert blanketing using Nitrogen Gas , semi-reactive blanketing using CO2 / N2 or O2 /CO2 /N2 or fully reactive blanketing using CO2 or CO2 /O2 (Parry 1993; Moleyar and Narasimham 1994).

Normally, the concentration of O2 in a pack is kept very low (1-5%) by use of Nitrogen Gas Generators to reduce the respiration rate of fruits and vegetables (Lee and others 1995). Reducing the rate of respiration by limiting O2 prolongs the shelf life of fruits and vegetables by delaying the oxidative breakdown of the complex substrates which make up the product. Also, O2 concentrations below 8% reduce the production of ethylene, a key component of the ripening and maturation process. However, at extremely low O2 levels (that is, <1%), anaerobic respiration can occur, resulting in tissue destruction and the production of substances that contribute to off-flavors and off-odors (Lee and others 1995; Zagory 1995), as well as the potential for growth of food borne pathogens such as Clostridium botulinum (Austin and others 1998). Therefore, the recommended percentage of O2 in a modified atmosphere for fruits and vegetables for both safety and quality falls between 1 and 5% (Table VI-4). However, it is recognized that the oxygen level will realistically reach levels below 1% in MAP produce. It is generally believed that with the use of permeable films, spoilage will occur before toxin production is an issue; MAP of produce, however, should always incorporate packaging materials that will not lead to an anoxic package environment when the product is stored at the intended temperature. This recommendation should be qualified, however, by saying that all films are permeable to oxygen to some degree; the difference pertains to the rate of gas transfer through the film, with some films allowing greater transfer rates than others. Moreover, the elimination or significant inhibition of spoilage organisms should not be practiced, as their interaction with pathogens may play an integral role in product safety. A number of packers of fresh prepared green vegetables in the United Kingdom have been experimenting with O2 mixtures between 70 and 100% (Day 1996). The treatment, referred to as "oxygen shock" or "gas shock," has been found to be very effective in inhibiting enzymatic discoloration, preventing anaerobic fermentation reactions, and inhibiting aerobic and anaerobic microbial growth. High levels of O2 can inhibit the growth of both anaerobic and aerobic microorganisms since the optimal O2 level for growth (21% for aerobes, 0-2% for anaerobes) is surpassed. However, there have also been reports of high O2 (that is, 80-90%) stimulating the growth of foodborne pathogens such as Escherichia coli and Listeria monocytogenes (Amanatidou and others 1999). Recent studies by Kader and Ben-Yehoshua (2000) and Wszelaki and Mitcham (2000) examining the use of superatmospheric O 2 levels to control microorganisms on produce, have found that only O 2 atmospheres close to 100 kPa or lower pressures (40 kPa O 2 ) in combination with CO 2 (15 kPa), are truly effective. These requirements may be difficult to achieve in industry since working with such high O 2 levels can be hazardous due to flammability issues. As with most MAP gases, superatmospheric O2 has varied effects depending on the commodity, and further research is required in this area to elucidate the utility of this technique in the fresh-cut produce industry. A high O2 MAP group has been formed in the United Kingdom and includes a number of industry groups, notably Marks and Spencer plc, one of the first retail chains to distribute MAP foods. More recently, the "high O2 MAP club" has provided a base for the new "Novel Gases MAP Club" in the United Kingdom, a group that will investigate the use of novel high O2 , argon and nitrous oxide MAP for extending shelf life and quality of fresh-cut produce. Their main focus is research into the commercial application of this process.

A process for generating a nitrogen-based gas, comprising the steps of: (i) combining a secondary reducing gas including at least one reducing gas with a primary nitrogen gas including 0.5-5% by volume of oxygen, the combining of the secondary gas being performed according to an uncontrolled all-or-nothing method; (ii) reacting the primary gas and the secondary gas in a catalytic deoxygenation reactor so as to obtain a nitrogen-based reaction gas which includes water vapor; and (iii) removing at least a part of the water vapor present in the nitrogen-based reaction gas by cooling the reaction gas under pressure to induce formation of a liquid phase and then extracting the liquid phase from the reaction gas under pressure to obtain a purified reaction gas

Many industrial lasers need nitrogen as an assist gas to help in the processing of materials. The laser cutting process uses a laser beam to melt or chemically alter the material being cut. The assist gases are used at the point where the laser interacts with the material and is used to remove the molten material and/or to chemically react with the material to produce additional thermal energy.

Depending on the process and material being cut, it is important that the assist gas is at the appropriate quality, not only to keep lasers operating reliably, but also to ensure the highest process productivity. For instance, stainless steel cutting requires some of the highest purity nitrogen - levels above 99.9%....

Tank Blanketing, or padding, refers to applying a cover of Inert gas over the surface of a stores commodity; usually a liquid. Its purpose is either to protect or contain the stored product or prevent it from harming personnel, equipment, or the environment. In most cases the blanketing gas is Nitrogen, although other gases may be used.

Blanketing with Nitrogen Gas may prevent liquid from vaporizing into the atmosphere. It can maintain the atmosphere above a flammable or combustible liquid to reduce ignition potential. It can make up the volume caused by cooling of the tank contents, preventing vacuum and the ingress of atmospheric air.

Blanketing Nitrogen Gas can simply prevent oxidation or contamination of the product by reducing its exposure to atmospheric air. It can also reduce the moisture content. Gas Nitrogen is supplied in a very pure and dry state.

The list of products blanketed is extensive ---- everything from adhesives, catalyst, chemicals, fats and oils, foods, fuels, inks, pharmaceuticals, photographic chemicals, soaps, and water.

Tank blanketing, or padding, is the process and practice of covering the surface of a stored commodity, usually a liquid, with an Inert gas usually Nitrogen Which Can be produced Onsite thru a Nitrogen Gas Generator ,. If that commodity is volatile or toxic, tank blanketing can prevent it from harming workers, equipment, and the environment. When the commodity is a food or other substance, tank blanketing protects it from oxidation or contamination through exposure to air or moisture. In most cases, tank blanketing gas is pure, dry nitrogen.

Extrusion is defined as the process of shaping material, such as aluminum, by forcing it to flow through a shaped opening in a die. Extruded material emerges as an elongated piece with the same profile as the die opening.

The most important factor to remember in the extrusion process is temperature. Temperature is most critical because it gives aluminum desired characteristics such as hardness and finish.

The steps in the extrusion process are as follows:

The list of products blanketed is extensive ---- everything from adhesives, catalyst, chemicals, fats and oils, foods, fuels, inks, pharmaceuticals, photographic chemicals, soaps, and water.

1. Billets must be heated to approximately 800-925 ° F.
2. After a billet reaches the desired temperature, it is transferred to the loader where a thin film of smut or lubricant is added to the billet and to the ram. The smut acts as a parting agent (lubricant) which keeps the two parts from sticking together.
3. The billet is transferred to the cradle.
4. The ram applies pressure to the dummy block which, in turn, pushes the billet until it is inside the container.
5. Under pressure the billet is crushed against the die, becoming shorter and wider until it has full contact with the container walls. While the aluminum is pushed through the die, liquid nitrogen flows around some sections of the die to cool it. This increases the life of the die and creates an inert atmosphere which keeps oxides from forming on the shape being extruded. In some cases nitrogen gas is used in place of liquid nitrogen. Nitrogen gas does not cool the die but does create an inert atmosphere.
6. As a result of the pressure added to the billet, the soft but solid metal begins to squeeze through the die opening.
7. As an extrusion exits the press, the temperature is taken with a True Temperature Technology (3T) instrument mounted on the press platen. The 3T records exit temperature of the aluminum extrusion. The main purpose of knowing the temperature is to maintain maximum press speeds. The target exit temperature for an extrusion is dependent upon the alloy. For example, the target exit temperature for the alloys 6063, 6463, 6063A, and 6101 is 930° F (minimum). The target exit temperature for the alloys 6005A, and 6061 is 950° F (minimum).
8. Extrusions are pushed out of the die to the leadout table and the puller, which guides metal down the run-out table during extrusion. While being pulled, the extrusion is cooled by a series of fans along the entire length of the run-out and cooling table. (Note: Alloy 6061 is water quenched as well as air quenched.)
9. Not all of the billet can be used. The remainder (butt) contains oxides from the billet skin. The butt is sheared off and discarded while another billet is loaded and welded to a previously loaded billet and the extrusion process continues.
10. When the extrusion reaches a desired length, the extrusion is cut with a profile saw or a shear.
11. Metal is transferred (via belt or walking beams systems) from the run-out table to the cooling table.
12. After the aluminum has cooled and moved along the cooling table, it is then moved to the stretcher. Stretching straightens the extrusions and performs 'work hardening' (molecular re-alignment which gives aluminum increased hardness and improved strength).
13. The next step is sawing. After extrusions have been stretched they are transferred to a saw table and cut to specific lengths. The cutting tolerance on saws is 1/8 inch or greater, depending on saw length.

After the parts have been cut, they are loaded on a transportation device and moved into age ovens. Heat-treating or artificial aging hardens the metal by speeding the aging process in a controlled temperature environment for a set amount of time.

Nitrogen inflation ensures that your tyres get 99.9 per cent of refined nitrogen. Tyres with that amount of nitrogen roll more freely, because this gas is lighter than compressed air. Tyre wears more slowly when it is fed on nitrogen. Nitrogen increases tyre life by 10 to 15 per cent. Air has more moisture and it oxidises from inside eating into the rim. Nitrogen is trouble-free on that front." Although the free movement of the tyres make for fuel efficiency, we refrains from telling how much, for want of a thorough study on the subject. The nitrogen tyre inflation also thrives on the fill-it-shut-it concept and is marketed as a godsend for lazy bones — "The nitrogen will stay inside the tyres for well over three months, which means you don't worry that often about the air pressure. Thanks to thinner tubes, nitrogen might slip out of two-wheeler tyres faster."

There appears to be increasing numbers of people promoting Nitrogen as a tyre inflation media in preference to normal air.

The claimed advantages are:

• The molecules of Nitrogen are allegedly larger than oxygen thus providing a more stable inflation pressure.
• Nitrogen is more stable under temperature fluctuations hence maintaining a more consistent inflation pressure.
• Nitrogen has a lower moisture content and hence has less corrosive effect on the tyre and wheel.

Promoters use the more stable and consistent inflation pressure argument as providing better tyre mileage, better fuel consumption and better tyre casing durability.

he size of a Nitrogen molecule is very comparable with that of oxygen and as air is made up of about 80% nitrogen the effect on slow leakage will be very small.

The temperature fluctuation in tyres in everyday use is small and pressure increases or decreases have never presented a problem, providing the tyre is correctly inflated in the first instance.

Given that tyres have been designed around normal air inflation for approaching a century and Nitrogen even longer, then if there was any significant advantage, Nitrogen would be the common inflation media, which it is not.

With regard to the "less moisture" argument, tyre 'inner liners' have developed to a sophisticated level and are designed to take account of moisture in normal air. Therefore providing the tyre is not damaged air remains a safe practical inflation media. If however the tyre does become damaged and the steel reinforcement becomes exposed there is a risk of corrosion taking place. Nitrogen would have a marginal positive effect under these circumstances. However, given that nearly all damage to a tyre that could cause exposure of the steel wire, comes from external sources it is most likely that the atmosphere and not the inflation media would cause any corrosion of the steel.

There are positive arguments for the use of Nitrogen in specialist areas such as Formula 1 racing and applications where tyre temperatures are high (Aircraft) or where the risk of explosion is high (hazardous materials). In these circumstances Nitrogen offers advantages of better stability during rapid temperature changes.

In conclusion Nitrogen may offer some small advantages over air, but in everyday usage of tyres the effect would be extremely difficult to measure and any benefit marginal. Users would have the added complication, of having to return to their specialist tyre dealer to have tyre pressures adjusted, as the use of airlines at local garages would nullify any advantage that is offered by nitrogen.

System Residues hide leaks. Sludge and residues coat the interior of system components and temporarily seal corrosion pits, fissures, seams, seals, o'rings, and other small leak points. Some of those residues include refrigeration oils, acids, desiccant, pulverized metal, Teflon piston ring material, brazing fluxes, dye particles, etc.

Overcoming Residue Surface Tension: Leaks are harder to find because leak testing is performed with the system turned off. Lost are the benefits of an operating system: a) constant washing of interior surfaces of components; b) higher operating pressures that encourage leaks. With a system at rest, the undisturbed residues mentioned above are able to coat the insides of the evaporator, condenser, compressor, and other components. When Residue Surface Tension is greater than the interior pressures' ability to displace it, there is no leak occurrence, thus no leak detection.

Residue Displacement: If surface tension is the culprit, then how do we overcome it? Answer: By adding 4-ounces of chlorine-based refrigerant R-22 to the system. R-22 disturbs the surface tension. We follow that by pressurizing the system with 175-200 psi of nitrogen. Both are cheap.

At the higher system pressure, the R-22 overcomes the residue surface tension and forces the leak path to reopen. Now, enough R-22 gas is available so that leaks are detected easily. The R-22 is the residue-displacing agent.

R-22 summary. R-22: (a) creates a leak path because of its oil solubility and residue displacement potential; (b) is more readily detectible by electronic leak detectors than HFCs; (c) is non visual-dependent, unlike dyes, thus can be used effectively to locate leaks in enclosed areas; (d) will not cross-contaminate nor cause any harmful consequences to CFC, HFC, nor blend refrigerant systems (i.e., after leak testing an HFC (R-134a) system using R-22, there is typically zero percent cross-contamination if evacuated afterwards).

Nitrogen summary. Nitrogen Gas has the following qualities: (a) inert gas , very dry and non-flammable; (b) does not go into solution with refrigeration oil to create non condensable pressure problems (i.e., after leak testing an HFC (R-134a) system using R-22 and nitrogen, there is typically zero percent non condensables (nitrogen or air), if evacuated afterwards).

Diluted Liquid Soap. Speed is important to technicians when performing a leak test. Large and medium size leaks can be quickly located in exposed areas such as under hood components by applying diluted liquid dishwashing soap directly to suspected leak points.

Multiple Leaks. If a large leak is discovered repair it and perform a follow-up leak test. Leak tests should be performed following each repair until all leak points are found and fixed.

Pinpoint versus Area Testing Pinpoint Accuracy. Technicians need to know exactly where leaks exist. Consequently, leak testing needs to be pinpoint accurate, regardless whether by visual or non-visual means. With dyes, the detection is strictly visual and general area, not pinpoint. Dyes do not provide the rapid and finite definition of the Combination Method [non-visual: electronic leak detector detecting the nitrogen-pressured R-22, and, visual: diluted soap solution bubbling].

Electronic Leak Detectors. Heated diode leak detectors are currently the best non-visual, dependent leak detection instrument for sensing a gaseous leak. They have the necessary characteristics of sensitivity, repeatability and recoverability (after a leak), which are so important.

Releasing Test Mix. The EPA approved the releasing of the “test mix” (R-22 & nitrogen) with the stipulation that: “All existing refrigerant within the system be recovered properly, and a 102mm (about 4”) mercury vacuum drawn on the system.”

By their definition, the R22-nitrogen test mix used for leak testing is not considered a refrigerant and therefore may be released to atmosphere. Their rationale is that one tiny loss which results in the discovery and repair of a leak reduces the greater loss over the life of a system. It's better than multiple recharges of refrigerant and multiple losses to atmosphere.

Note: We've learned that the R22- Nitrogen Gas test mix should be released outside the building via copper (or other) tubing to prevent fouling the air inside the shop. This prevents false alarms by the leak detector. Also, always maintain a well-ventilated work area.

Bulk shipped coffee, tea, nuts or dried fruit are often contaminated with a variety of live insects or other organisms which hatch and grow during long periods of storage or sea transport. These pests present not only a hygiene risk but also an economic one. To date, such pests have been treated using poisonous chemicals such as Methyl Bromide or Phostoxin which can have the disadvantage of contaminating the food. The consequences of using these chemicals include loss or change of flavor, changes to colour, even so far as causing the consignment to be destroyed because of contamination.

New Technologies against Pests A new method to combat these insect pests, which does not involve the use of poisons and is safe for humans, has been discovered. Based on the fact that "no organism can survive without Oxygen" all products requiring treatment are packed inside an Oxygen proof skin (called an Inliner) before shipping. Nitrogen Gas is flushed into the Inliner, displacing Oxygen until its concentration is reduced to <0.1%. This level is maintained for up to 100 hours, killing not only the adult pests, but also any larvae and unhatched eggs. As the Inliner is sealed, the "fumigation" process can then take place in transit, saving time and reducing handling costs.