Table of Contents
Food packaging is a product that we come into contact with every day. Have you ever wondered what food would look like without packaging? So do you know what packaging method to use is the standard food grade?
The nature of food
Food is derived from animal or vegetable sources. Its organic nature makes it an unstable commodity in its natural form. Left on their own, foodstuffs can deteriorate rapidly , sometimes becoming unfit for human consumption within hours. Food spoilage can occur by three means.
“Internal biological deterioration” describes biological functions that continue even though the food has been harvested. Fruits continue to ripen and vegetables continue to respire. Fresh meat exhibits many of the processes associated with living tissue.
“External biological deterioration” refers to the action of microorganisms. What is food to us is also food to a host of other organisms. Molds, bacteria and yeasts are present inmost foods. Often they are harmless or even beneficial. In other instances, they can be deadly.
“Abiotic deterioration” describes those changes that are chemical or physical in nature and that are not dependent on a biological agent. For example, atmospheric oxygen will chemically react with (oxidize) many substances.
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Microorganisms
A large part of food preservation depends on the control of microorganisms. Molds or fungi are multicellular and unicellular plantlike organisms.
Neither is capable of producing chlorophyll or carbohydrates. Instead, they depend on outside sources for nutrients. Molds form filamentous branching growths called mycelia and reproduce by spores. Yeasts are similar organisms that reproduce by budding.
The propagation and spread of molds and yeasts is typically slower than for bacteria because of the reproduction method.
Typical of any living entity, each microorganism type has a preferred environment in which to exist and propagate and other environments under which it will not.
By manipulating the four principal environmental factors that regulate microorganism growth-temperature, moisture, acidity ( pH), and nutrient source-microorganisms can be controlled or eliminated.
Food packaging methods
Barrier packaging
We have noted that the movement of gases into or out of a package can lead to undesirable changes in the food product. An important factor in the preservation of products that contain gaseous or volatile components or that are susceptible to change through the action of such components is the ability to control the movement of these gases and volatiles.
Stopping the movement of a gas requires barrier packaging. This packaging construction either retains desirable gases and volatiles inside the package or prevents undesirable gases and volatiles from entering the package.
Often, barrier packaging must address both capabilities. Of the materials a packager can choose, only glass and metal provide absolute barriers to all gases and volatiles.
Thermal Processing
Heat can destroy microorganisms. In many instances, it is not necessary to kill all microorganisms. Pasteurization, a mild heat treatment of 60℃ to 70℃ (140℉ to 150℉), kill most, but not all, microorganisms present.
“Hot filling” refers to product filling at elevated temperatures up to 100℃ (212℉). Hot filling is used to maintain sterility in products such as jams, syrups and juices.
Ultra-high temperature (UHT) processing of milk and fruit juices uses temperatures in the range of 135℃ to 150℃ (275℉ to 302℉), but for a few seconds or less.
The high temperature is enough to kill most pathogens. UHT is the basis of most flexible aseptic drink packaging.
The term “aseptic” as applied to packaging refers to any system wherein the product and container are sterilized separately and then combined and sealed under aseptic conditions.
Water reduction
Drying is an old and well-established method of preserving food. The essential feature of drying is that moisture content is reduced below that required for the support of microorganisms.
An added advantage is reduced bulk and reduction of other chemical activity. Available moisture can be reduced by simple heat drying or, less obviously, by the addition of salt or sugar.
Equilibrium relative humidity(E.R H) is the atmospheric humidity condition under which a food will neither gain nor lose moisture to the air. This value is often expressed as Aw, the water activity. A food with an Aw of 0.5 is at an equilibrium relative humidity of 50%.
Chemical preservatives
Various natural and synthetic chemicals and antioxidants are used to help extend the keeping quality of foods. The use of most of them is strictly controlled by law, although what is allowed varies from country to country.
Antioxidants and oxygen absorbers can reduce oxidation. Some oxygen absorbers have been used indirectly, contained in separate pouches within the sealed package.
The absorber, usually, a fine iron powder, scavenges any available oxygen still in the package. Package material may also incorporate antioxidants.
Modified atmosphere packaging
Modified atmosphere packaging (MAP) recognizes that many food degradation processes have a relationship with the surrounding atmosphere. One mode of degradation is removed if a product prone to oxidation is packaged in an atmosphere free of oxygen.
MAP involves the introduction of a gas mixture other than air into a package, which mixture is then left to equilibrate or change according to the nature of the system.
A related process, controlled atmosphere packaging (CAP) , is used in storage and warehousing where the atmosphere can be monitored and adjusted.
Vacuum packaging is one type of MAP. It has the effect of eliminating some or all oxygen that might contribute to degradation.
However, the method is not universally useful, since products such as fruits and vegetables have respiratory functions that must be continued. Another difficulty is that red meat will turn brown or purple without oxygen.
Pressures created by the external atmosphere surrounding a vacuum-packaged product can physically crush delicate products or squeeze water out of moist products. Other types of MAP solve these problems.
Ambient air is about 20% oxygen and 80% nitrogen, with a trace of carbon dioxide. Altering these proportions alters product response. This forms the basis of MAP shelf life extension.
Irradiation
Irradiation has been used to increase the keeping quality of various foods. Radiation is energy categorized by wavelength and includes radio waves, microwaves, infrared radiation, visible light, ultraviolet light and X rays.
Short-wavelength radiations have enough energy to cause energy to ionization of molecules, mainly water. Ionization can disrupt complex molecules and leads to the death of living organisms.
Enzymes, vitamins and other similar complex molecules can also be destroyed. Excessive exposure will produce enough chemical changes that the taste of food or the chemistry of an enclosing container will be altered.
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