Showing posts with label MAP. Show all posts
Showing posts with label MAP. Show all posts

Monday, January 24, 2011

THE "FRESH" CONTROVERSY-IS IT LOGICAL?

There is an increasing tendency for people o go for "fresh", "local" "natural" or organic foods and the reason is not far to seek. It is simply the fear factor that is driving millions of consumers away from preserved or processed foods and the food industry is to blame itself for this sorry situation. Historically food technology was evolved over centuries to extend the supply chain so that adequate foods are available all year round. Use of salt or sugar which increases the osmotic pressure in food system to discourage proliferation of pathogens and many spoilage organisms continues even to day though from healthy angle they are shunned by a substantial strata of the society. While uncontrolled salt consumption is known to be linked to hyper tension and cardiovascular disease, high sugar can be responsible for dental decay, diabetes, obesity and other disorders. Organolepticaly too much sugar or salt can create quick satiety. Salt and sugar preserved food products can be farthest from the concept of fresh foods.

Sun drying or the more scientific mechanical drying of perishables which contain high levels of moisture gives products with altered textural features but it still served the purpose of extending the life of the food significantly due to low water activity in such foods after removing bulk of the water content. Besides, the reconstituted final product has drastically different eating quality, not often liked by consumers. Vast improvements in dehydration technology have contributed to better finished products and freeze drying can give a product that can be quite satisfactory though cost wise such products can be very expensive. However dehydrated foods can also never qualify to be called fresh.

One often hears about "Dairy Fresh" milk which is probably taken to mean that the milk is as fresh as the one milked directly from the cow! In reality milk travels over some distance from the point of milking, gets refrigerated, pasteurized and packed before reaching the consumer. In a country like the US raw milk is never allowed to be sold directly and therefore fresh milk in literal sense can never be seen by a US consumer while in India really fresh milk is sold directly to homes within a matter of minutes! Similarly fresh fruits and vegetables which are sold in many markets in India are considered really fresh because not much time elapses between their harvest and bringing to the market. In contrast most fresh produce sold in super markets cannot claim to be fresh because they undergo a series of "processing" involving cleaning, washing, sorting, trimming, cold storage and distribution over considerable distances.

Modern technologies like MAS and MAP in combination with cold storage can extend the life of fresh produce for weeks and months though quality-wise they will always be inferior to farm fresh counterparts. That raises the inevitable question as to what qualifies to be called "fresh"? The current understanding that any food put on sale as early as possible after harvesting is some what vague and there does not appear to be any scientific definition universally accepted. The perishable nature of foods in general calls for preservation, at least till they reach the market and ultimately the bottom line is that the eating quality and nutritive value should not be adversely affected to any significant extent.

As foods, especially the perishable ones are seasonal in nature, their year round availability and supply can be assured only if they are preserved for some time. While some foods like apple, potato, onion etc are amenable to long term storage under MAS and low temperature environment, others can still be stored under such conditions for limited periods. Frozen storage or freeze drying can be the best way of protecting a food from nutrition angle but the consumer will have to compromise on eating quality as there will be deterioration in this respect due to freezing. While under optimum frozen temperature conditions almost all foods can have storage life beyond an year, the sensory quality of products when thawed can never be the same as the fresh material before freezing.

While advances in technology and transportation extends the shelf life of food, there is a price for availability and convenience in terms of nutrition and taste. Probably obsession with the word "fresh" will have to be overcome eventually as it is impossible for the world to meet the demand for such "farm fresh" foods of every consumer in the world. While intense debate goes on regarding even the ability of man to meet the bare food needs of the ever expending population, the protagonists of fresh foods are well advised not to divert the attention of the world from the basic task of increasing food production and making them available to people with maximum nutrient content. The story of organic foods also bears a parallel to fresh foods as it is logistically impossible to raise and supply such foods to meet the needs of entire population! In spite of movements like Local Produce, Slow Foods, Urban Gardening, Roof-top farming, Organic farming etc, it is unlikely that every person on this planet can be provided with "fresh" foods as it is understood commonly.

V.H.POTTY
http://vhpotty.blogspot.com/
http://foodtechupdates.blogspot.com

Friday, May 8, 2009

CARBON DIOXIDE-A FRIENDLY 'FOE'



Carbon dioxide(CO2), one of the naturally occurring gases in the atmosphere, is blamed by the environmentalists for the dreaded global warming phenomenon being faced by the modern world. It is true that CO2 is omnipotent because all living creatures inhale oxygen and exhale CO2 every second without which life is not possible. Plants absorb CO2 during day time to fix solar energy and synthesise starch using chlorophyll pigments present in green leaves. Normally atmospheric air contains 21% Oxygen, 0.038% Carbon Dioxide and 78% Nitrogen. Major sources of CO2 emission are fossil fuels which are burned to generate energy for driving modern civilization. Kyoto Protocol on green house gases calls on all countries to reduce these emissions in order to save the world from disaster due to uncontrollable and undesirable weather changes. Viewed from this angle CO2 is indeed a villain but branding this gas as such ignores the beneficial role it plays in many spheres of life to day.

The omnipotent fire extinguisher that is a part of to day's civil infrastructure is based on the principle that CO2 is a fire retardant and the soda-acid fire extinguishers generate CO2 that can be directed at the fire. As a refrigerant, dry ice or solid CO2 has no parallel as it is a clean refrigerant leaving no residue once sublimed. The temperature of pure dry ice is minus 109.8F which can be further lowered by mixing powdered dry ice with ether or acetone to minus 220F. CO2 is one of the raw materials in the manufacture of the most popular fertilizer Urea. CO2 under pressure is also widely used as a cleansing agent in many industries.

Food industry owes a lot to CO2 for its diverse portfolio of products. Most common use, as a common man can see, is in the manufacture of aerated drinks where the fizz is provided by this gas. CO2 under pressure and at low temperatures dissolves in aqueous phase lowering the pH and providing an atmosphere that inhibits almost all living contaminants in the product. Technologies like Modified Atmosphere Packaging (MAP), Controlled Atmosphere Storage (CAS), Equilibrium Modified Atmosphere Packing (eMAP), Modified Atmosphere/Modified Humidity Packing (MA/MH) owe their strength to the presence of CO2 in the gas mixture that protects commodities under ambient as well as reduced temperature conditions. CO2 at just 80% cause hypercarbia while Nitrogen beyond 98% concentration leads to hypoxia conditions, both inimical to most living things including microorganisms. CAS was being used since 1930 for transportation of fruits over long distances while MAP became prominent in 1970 for Bacon and Fish transport. To day MAP is widely used for distributing products like red meat, sea food, minimally processed fruits and vegetables, cheese, pasta, bakery goods, poultry, cooked and cured products, ready meats and dried foods. It is estimated that 25-40% of all fresh produce harvested does not reach the consumer table due to spoilage and emergence of the above technologies helps to reduce the waste to the minimum where CO2 plays a very significant role.

While meat and fish require very low gas permeability films or high barrier packing materials as they are non-respiring in nature, fruits and vegetables, being actively respiring and transpiring, call for use of films with certain permeability characteristics to allow for diffusion of O2 and CO2 for establishing equilibrium. They need O2 for respiration and emit CO2 as a by-product. Build up of too much CO2 can adversely affect the sensory quality of the product packed and that calls for its diffusion out of the pack. Depletion of O2 is also to be avoided and there fore O2 entry into such packs at desired rate is also necessary. There are excellent packaging materials available to day thanks to the innovative efforts of the packaging industry, meeting every need of the food packers. Both gas flushing and compensated vacuum methods are deployed in packing foods under MAP system. O2 levels of 3-5%, CO2 levels of 10% and rest N2 can be effective for packing fruits and vegetables. CO2 at concentrations of 10% or less is considered most effective in killing all microbes and pests. Grains stored under CO2 can stay in good shape for more than 5 years.

CO2 is a by-product of alcohol fermentation and is available in plenty, waiting to be harnessed for use by the food industry. In baking industry CO2 is an essential tool to impart the desired texture to the baked products. Baking powder, based on sodium bicarbonate and tartaric acid or calcium hydrogen phosphate which generates CO2 on heating is an integral part of the bakery industry and millions of kitchens around the world. The loaf volume, texture and other qualities of the bread are imparted by CO2 generated by yeast under aerobic conditions. The Super Critical CO2 Fluid Extraction Technology (SCFE), the high end process developed some time back has enabled the industry to obtain concentrated and purified products from flavor bearing materials like spices, herbs and aromatic plants. The decaffeinated coffee is made to day mostly by the SCFE technology which does not affect adversely the delicate flavor constituents present in coffee, unlike the solvent extraction technology and Caffeine is obtained as a valuable by-product.

Since the world is fighting against uncontrolled build up of CO2 to protect the environment, it is certainly an adversary but considering the diverse beneficial uses it has in the day day to day lives of people, CO2 is also a friendly partner that sustains the human civilization.

V.H.POTTY
http://vhpotty.blogspot.com/