User:Mariakhalil16/sandbox

Modified atmosphere
Modified atmosphere is the practice of modifying the composition of the internal atmosphere of a package (commonly food and drugs) in order to extend their shelf life. The need for this technology for food arises from the short shelf life of food products such as meat, fish, poultry, and dairy in the presence of oxygen. In food, oxygen is readily available for lipid oxidation reactions. Oxygen also helps maintain high respiration rates of fresh produce, which contribute to shortened shelf life. From a microbiological aspect, oxygen encourages the growth of aerobic spoilage microorganisms. Therefore, the reduction of oxygen and its replacement with other gases can reduce or delay oxidation reactions and microbiological spoilage. Oxygen scavengers may also be used to reduce browning due to lipid oxidation by halting the auto-oxidative chemical process.

The modification process generally lowers the amount of oxygen (O2) in the headspace of the package. Oxygen can be replaced with nitrogen (N2), a comparatively inert gas, or carbon dioxide (CO2).

A stable atmosphere of gases inside the packaging can be achieved using active techniques, such as gas flushing and compensated vacuum, or passively by designing “breathable” films.

History
The first recorded beneficial effects of using modified atmosphere date back to 1821. Jacques Etienne Berard, a professor at the School of Pharmacy in Montpellier, France, reported delayed ripening of fruit and increased shelf life in low oxygen storage conditions. Controlled Atmosphere Storage (CAS) was used from the 1930's when ships transporting fresh apples and pears had high levels of CO2 in their holding rooms in order to increase the shelf life of the product. In the 1970's, MA packages reached stores when bacon and fish were sold in retail packs in Mexico. Since then, development has been continuous and interest in MAP has grown due to consumer demand.

Theory
Atmosphere within the package can be modified passively or actively. In passive MAP, the high concentration of CO2 and low O2 levels in the package is achieved over time as a result of respiration of the product and gas transmission rates of the packaging film. This method is commonly used for fresh respiring fruits and vegetables. Reducing O2 and increasing CO2 slows down respiration rate, conserves stored energy, and therefore extended shelf life. On the other hand, active MA involves the use of active systems such as O2 and CO2 scavengers or emitters, moisture absorbers, ethylene scavengers, ethanol emitters and gas flushing in the packaging film or container to modify the atmosphere within the package.

The mixture of gases selected for a MAP package depends on the type of product, the packaging materials and the storage temperature. The atmosphere in an MA package consists mainly of adjusted amounts of N2, O2, and CO2. Reduction of O2 promotes delay in deteriorative reactions in foods such as lipid oxidation, browning reactions and growth of spoilage organisms. Low O2 levels of 3-5% is used to slow down respiration rate in fruits and vegetables. In the case of red meat, however, high levels of O2 (∼80%) are used to reduce oxidation of myoglobin and maintain an attractive bright red color of the meat. Meat color enhancement is not required to pork, poultry and cooked meats, therefore, a higher concentration of CO2 is used to extend the shelf life. Levels higher than 10% of CO2 are phytotoxic for fruit and vegetables, so CO2 is maintained below this level. N2 is mostly used as a filler gas to prevent pack collapse. In addition, it is also used to prevent oxidative rancidity in packaged products such as snack foods by displacing atmospheric air, especially oxygen, therefore extending shelf life. The use of noble gases such as Helium (He), Argon (Ar) and Xenon (Xe) to replace N2 as the balancing gas in MAP can also be used to preserve and extend the shelf life of fresh and minimally processed fruits and vegetables. Their beneficial effects are due to their higher solubility and diffusivity in water making them more effective in displacing O2 from cellular sites and enzymatic O2 receptors.

There has been a debate regarding the use of carbon monoxide (CO) in the packaging of red meat due to its possible toxic effect to packaging workers. Its use however results to a more stable red color of carboxymyoglobin in meat which leads to another concern that it can mask evidence of spoilage in the product.

Effect on microorganisms
Low O2 and high CO2 concentrations in packages are effective in limiting the growth of Gram negative bacteria, molds and aerobic microorganisms, such as Pseudomonas spp. High O2 combined with high CO2 could have bacteriostatic and bactericidal effects by suppression of aerobes by high CO2 and anaerobes by high O2. CO2 has the ability to penetrate bacterial membrane and affect intracellular pH. Therefore, lag phase and generation time of spoilage microorganisms are increased resulting in shelf life extension of refrigerated foods. Since the growth of spoilage microorganisms are suppressed by MAP, the ability of the pathogens to grow is potentially increased. Microorganisms that can survive under low oxygen environment such as Campylobacter jejuni, Clostridium botulinum, E. coli, Salmonella, Listeria and Aeromonas hydophila are of major concern for MA packaged products. Products may appear organoleptically acceptable due to the delayed growth of the spoilage microorganisms but might contain harmful pathogens. This risk can be minimized by use of additional hurdles such as temperature control (maintain temperature below 3 degrees C), lowering water activity (less than 0.92), reducing pH (below 4.5) or addition or preservatives such as nitrite to delay metabolic activity and growth of pathogens.

Packaging materials
Flexible films are commonly used for products such as fresh produce, meats, fish and bread seeing as they provide suitable permeability for gases and water vapor to reach the desired atmosphere. Pre-formed trays are formed and sent to the food packaging facility where they are filled. The package headspace then undergoes modification and sealing. Pre-formed trays are usually more flexible and allow for a broader range of sizes as opposed to thermoformed packaging materials as different tray sizes and colors can be handled without the risk of damaging the package. Thermoformed packaging however is received in the food packaging facility as a roll of sheets. Each sheet is subjected to heat and pressure, and is formed at the packaging station. Following the forming, the package is filled with the product, and then sealed. The advantages that thermoformed packaging materials have over pre-formed trays are mainly cost-related: thermoformed packaging uses 30% to 50% less material, and they are transported as rolls of material. This will amount in significant reduction of manufacturing and transportation costs.

When selecting packaging films for MAP of fruits and vegetables, the main characteristics to consider are gas permeability, water vapor transmission rate,

mechanical properties, transparency, type of package and sealing reliability. Traditionally used packaging films like LDPE (low-density polyethylene), PVC (polyvinyl chloride), EVA (ethylene-vinyl acetate) and OPP (oriented polypropylene) are not permeable enough for highly respiring products like fresh-cut produce, mushrooms and broccoli. As fruits and vegetables are respiring products, there is a need to transmit gases through the film. Films designed with these properties are called permeable films. Other films, called barrier films, are designed to prevent the exchange of gases and are mainly used with non-respiring products like meat and fish.

MAP films developed to control the humidity level as well as the gas composition in the sealed package are beneficial for the prolonged storage of fresh fruits, vegetables and herbs that are sensitive to moisture. These films are commonly referred to as modified atmosphere/modified humidity packaging (MA/MH) films.

Equipment
In using form-fill-seal packaging machines, the main function is to place the product in a flexible pouch suitable for the desired characteristics of the final product. These pouches can either be pre-formed or thermoformed. The food is introduced into the pouch, the composition of the headspace atmosphere is changed within the package; it is then heat sealed. These types of machines are typically called pillow-wrap, which horizontally or vertically form, fill and seal the product. Form-fill-seal packaging machines are usually used for large scale operations.

In contrast, chamber machines are used for batch processes. A filled pre-formed wrap is filled with the product and introduced into a cavity. The cavity is closed and vacuum is then pulled on the chamber and the modified atmosphere is inserted as desired. Sealing of the package is done through heated sealing bars, and the product is then removed. This batch process is labor intensive and thus requires a longer period of time; however, it is relatively cheaper than packaging machines which are automated.

Additionally, snorkel machines are used to modify the atmosphere within a package after the food has been filled. The product is placed in the packaging material and positioned into the machine without the need of a chamber. A nozzle, which is the snorkel, is then inserted into the packaging material. It pulls a vacuum and then flushes the modified atmosphere into the package. The nozzle is removed and the package is heat sealed. This method is suitable for bulk and large operations.

Products
Many products such as red meat, seafood, minimally processed fruits and vegetables, salads, pasta, cheese, bakery goods, poultry, cooked and cured meats, ready meals and dried foods are packaged under MA. A summary of optimal gas mixtures for MA products are shown in Table 1. _______________________________________________________________________________________________________________ end of writing for 4/26Proposed Outline:undefined


 * Scientific terms:-Ana- done
 * Add CAP: Controlled atmosphere packaging
 * Add VP: Vacuum packaging
 * Introduction (Done - Maria Khalil)
 * Products-Ana (Include specific application examples from review articles for each commodity type, if applicable)
 * Modified Atmosphere Packaging (MAP); Equilibrium Modified Atmosphere Packaging (EMAP)
 * These two sections can be combined; Rename sub topic as “Theory, summarize concepts and add citations (?)
 * Packaging Materials (Done - Maria Khalil)
 * Gases
 * Add mode of action for the gases used (as needed), add new gases used (from review articles)
 * Add section: Effect on microorganisms: Information from review articles/books on how spoilage microorganisms and pathogens are affected by MAP
 * Add section: Equipment (Maria Khalil - In Process)
 * QA of MAP Packages (Maria Khalil - In Process)

Sunday, April 1st, 2018 Update

List of Potential Topics for Maria Khalil and Ana Marie Estrada:
 * Modified Atmosphere Packaging (Rated C-Class)
 * Food Extrusion (Rated C-Class)
 * Flash Freezing (Rated Stub with High-Importance)
 * Caramelization (Rated Stub with Mid-Importance)
 * Low temperature cooking (No Rating found - requires improvement)

Very good evaluation Maria.

Article Evaluated: Food packaging

'''Is everything in the article relevant to the article topic? Is there anything that distracted you?'''

The sections discussed related directly to the article, however, there was a large section, "Gallery", which had some pictures that seemed random in terms of their distribution and of their content. In addition, sections like "Reducing food packaging" and "Recycling of food packaging" that are very scarce in terms of information and citations.

'''Is the article neutral? Are there any claims, or frames, that appear heavily biased toward a particular position?'''

The article is neutral and conveys information about the sections included.

Are there viewpoints that are overrepresented, or underrepresented?

Several information is underrepresented seeing as a few sections don't elaborate much on specific content, thus leaving the reader with less-than-sufficient knowledge on the topic.

'''Check a few citations. Do the links work? Does the source support the claims in the article?'''

The links for the citations work, but some of them redirect the link to a blogpost or another form of unofficial source of information.

'''Is each fact referenced with an appropriate, reliable reference? Where does the information come from? Are these neutral sources? If biased, is that bias noted?'''

Not all facts in the article are supported with references. The information could be originating from the experience or knowledge of the writers, rather than from a cited source. The sources used include official sources as well as primary research papers, however, some of them include links to blogposts, which are not very accurate sources of information.

'''Is any information out of date? Is anything missing that could be added?'''

The information is not outdated, but its main issue is the absence of sources in-text. All information should be cited with valid and accurate sources.

'''Check out the Talk page of the article. What kinds of conversations, if any, are going on behind the scenes about how to represent this topic?'''

The main points addressed in the Talk page of the article revolve around the absence of sources for several pieces of information in the article, as well as the need for an expert to differentiate between the Food Packaging article and the Packaging and Labeling article.

'''How is the article rated? Is it a part of any WikiProjects?'''

The article is rated as C-Class on the quality scale, which means a lot of improvements can be done to promote it to the B-Class.