What is it:
The modified atmosphere packaging (MAP) is the packaging of foods in a different atmosphere from the natural one. It consists of gas mixtures in different proportions according to the food: primarily oxygen, nitrogen and carbon dioxide but, potentially, argon, helium and nitrous oxide, all defined by the European directive on additives.
The EEC legislation concerning the labeling of food products, has recently introduced the words “Packaged in a protective atmosphere” which must be used between the directions on the label when the product’s life has been prolonged due to gas packaging .
What is its purpose:
the main purpose of the MAP packaging is to extend the preservation of the quality of foodstuffs.
To extend the life of a food it is essential to be able to slow down those chemical and biological mechanisms that determine its decay or deterioration. However, the modified atmosphere packaging, is used also in cases where it is not possible to guarantee a significant extension of conservation because of the specific properties of the food, it may allow a better presentation. For example, a steak of meat may appear to a bright red color and therefore more appreciated; a cheese present less greasy on the surface and provide a meat slices well detached from each other, in these cases the best presentation of the food may be the sole purpose sought.
A COMPARISON BETWEEN THE CONSERVATION IN AIR AND IN SOME FOOD FOR MODIFIED ATMOSPHERE
||Shel-life in air (days)
||Shelf-life in MAP (days)
|Fresh pasta stuffed
|Preparations of red meat
|White meat fresh
|Snacks and candy
How it works
To understand the effectiveness of the modified atmosphere it is important to consider that the food always interacts with the air that surrounds it.
The food-atmosphere interactions may be of microbiological or chemical-physical. Those microbiological concern the possibility of multiplication of the microorganisms present in the product, those affecting the chemical and physical stability and functionality of important components of the food such as proteins, membranes, lipids, pigments, enzymes, etc..
ATMOSPHERE “TYPE” FOR SOME FOOD
|Fatty fish and smoked
|Coffee beans and ground coffee
Air and modified atmosphere gases
The air we breathe is normally made up of about 21% oxygen and 78% nitrogen and the remaining 1% from lower gas including carbon dioxide is present for less than 0.05%. The oxidations (appearance of tastes and / or anomalous odors), fat rancidity, the browning and other modifications of color have their main cause in the reactions of oxygen with the constituents of the food and the majority of microbes that can contaminate food (mold, bacteria, acidifying, fermenting and turbidities) they need some more (aerobic) and those not (microaerophilic), oxygen to reproduce and multiply.
The first objective of the modified atmosphere used for the packaging of food is, in fact, a few exceptions, the elimination of oxygen from contact with the food.
In this regard it is essential to know a little ‘better the effects of different gases on the constituents of the food and microorganisms.
MAIN EFFECTS OF CO2 IN CONTACT WITH FOOD
– Inhibits the respiration of plants
– Acidifies the tissue fluids
– Can denature some proteins
– Inhibits plant growth hormones
– Inhibits the hydrolysis of pectins (avoiding fluidization)
– Slows down the ripening of the plant
– Reduces cold damage of plant tissues
MAIN EFFECTS OF ‘O2 IN CONTACT WITH FOOD
– Oxygenated myoglobin (red pigment of fresh meat) improving the color
– Activates the enzymatic and chemical oxidation
– Activates the degradation of beta-carotene
– Is the substrate of respiration of plant cells and microbial
MAIN EFFECTS OF ‘N2 IN CONTACT WITH FOOD
– Inhibits some proteases (enzymes that break up proteins)
– Inhibits some lipases (enzymes that cause rancidity)
– Inhibits some decarboxylase (respiratory enzymes)
– Preserve nitrosomioglobina (pink pigment of canned meat)
2. The carbon dioxide
As is evident the carbon dioxide has the greatest number of positive effects and can, therefore, considered the true active element of the modified atmosphere. Many chemical and biochemical effects reported correspond to an effective bacteriostatic.
From numerous experimental work shows that this gas inhibits microorganisms especially Gram – while action has much reduced the growth of Gram +, which are, in large part, anaerobic or microaerophilic. This gas also has two important characteristics, its solubility in different media and its reactivity:
CO2 is largely soluble in water but also in alcohol and fats; in all cases its solubility is largely influenced by the temperature (the lower the temperature the greater the solubility), so the efficacy of a modified atmosphere packaging is always influenced by storage temperature;
many links that this gas forms with food constituents are slowly reversible, even after you unpack the ‘carbon dioxide that is released slowly from the product, continues to exert a conservative useful for some time (“residual effect”) .
Quality and freshness of food
As is known, the qualitative characteristics of the fresh products evolve more or less rapidly depending on storage conditions, resulting in alterations that make the product unsuitable for consumption.
It may be intended as a shelf-life or durability of a product under certain storage conditions, the time limit within which the progress of individual reactive events lead to subtle changes on the sensory or otherwise still acceptable in terms of safety.
Among the factors that most affect the shelf life (ie, durability), the temperature is the most important, because it is subject to the constraints dictated by the organization of the supply chain.
Chemical reactions and physical processes that can alter the quality of food
|CHEMICAL AND BIOCHEMICAL REACTIONS
||NATURE OF PHYSICAL OR CHEMICAL PROCESSES-PHYSICS
- Non-enzymatic browning
- Enzymatic browning
- Hydrolysis of lipids
- Oxidation of lipids
- Hydrolysis of proteins
- Denaturation of proteins
- Agglomeration of the protein
- Hydrolysis of polysaccharides
- Synthesis of polysaccharides
- Degradation of natural pigments
- Inactivation of vitamins
- Changes in the bioavailability of vitamins and minerals
- Crystallization of the sugars
- Starch retrogradation
- Loss of volatiles
- Adsorption / desorption of moisture
- Changes in partitioning of components
In fresh produce, fresh or semi-like the root cause of this evolution is biological microorganisms and enzymes naturally present in food or from the environment to establish a variety of degradative reactions.
As is known, factors such as temperature, humidity, the presence of oxygen or light play a fundamental role in the speed of the individual events reagents. And of course, to the progress of these events correspond to changes on the sensory, nutritional and safety.
Normally, fresh food, an increase of 10 ° C storage temperature doubles or triples the rate of degradation of the quality parameters, which means that the period of storage of the product is simultaneously reduced to half or one third.
In this case, temperature fluctuations are recorded with the progressive exhaustion of the response of the indicator and, on the extent of this, one can determine, at each instant on the cumulative conditions equivalent time-temperature. Compared to more sophisticated monitoring systems, this application has the privilege of low-cost indicator, and possibilities of its localized placement (on the packaging of a product-carrier, a member of the transport vehicle, in a particularly unfavorable position in the display exposure) by means of these devices can therefore be repeated and extended control.
The use of modified atmosphere, in any case, should not be regarded as a mean to improve the quality of a food product poor but, rather, as a technological operation of support that only in conjunction with other interventions such as refrigeration, the hygienic control , etc.. can achieve the desired effects.
What must always be emphasized is the importance of temperature control, a control that can not be neglected, but which instead purchasing atmosphere packaging, perhaps even greater importance than in the case of pasteurization: maintaining the cold chain have, on the one hand, the guarantee to avoid proliferation of dangerous germs and, secondly, the certainty of a greater solubility in the food of gases, which can thus better exert their protective effects.