Recently, I was doing some reading and while I found a lot of research on veggies, fruits and red meats, there seemed to be less on poultry and modified atmosphere packaging. Two of the studies are reviewed in brief below.
In a study published in August of 2006 (Food Microbiol. 2006 Aug;23(5):423-9. Epub 2005 Oct 18.), the lab of Dr. Kontominas examined the effect of three different MAP gas blends on the shelf-life of precooked chicken. The three blends CO2/N2 tested (along with an aerobic control) were:
M1: 30% CO2/70% N2
M2: 60% CO2/40% N2
M3: 90% CO2/10% N2
The team monitored total viable counts (TVC), Lactic acid bacteria (LAB), Brochothrix thermosphacta, pseudomonads, yeasts and molds, and Enterobacteriaceae at 0, 4, 8, 12, 16 and 20 days. They found that using MAP extended the shelf life in all cases. The M1 gas mixture extended the shelf-life by 4 days, while the shelf-life was extended by greater than 6 days for the M2 and M3 gas mixtures. Additionally, they found that the M2 and M3 preserved the taste and smell of the precooked chicken right up until the 20th day of the testing. (For the full study, click here).
Dr. Kontominas’ lab also conducting an interesting set of experiments to examine the impact of adding oregano essential oil when packaging fresh chicken under modified atmosphere (Food Microbiol. 2007 Sep; 24(6):607-17. Epub 2007 Jan 12.).
In this study, oregano essential oil was added during MAP at either 0.1% or 1.0% (w/w). The MAP gas blends utilized were 30% CO2/70% N2 (M1 above) and 70% CO2/30% N2. The fresh chicken breasts were evaluated over the course of 25 days. As in the first study, the team monitored total viable counts (TVC), Lactic acid bacteria (LAB), Brochothrix thermosphacta, pseudomonads, yeasts and molds, and Enterobacteriaceae, as well as examining odor and taste. They also checked pH and color.
In brief, they found:
A “more pronounced effect” on microbial reduction when oregano essential oil was combined with MAP (1-5 log cfu/g).
No real effect on color with MAP or with a combination of MAP and essential oil.
A strong taste effect with oregano oil at a concentration of 1%, and it was therefore excluded from the final evaluation/comparison.
Sensory evaluation (taste and smell) showed a shelf-life extension of 3-4 days when containing 0.1% essential oil, 2-3 days for samples using MAP and 5-6 days when the two were used in combination.
In conclusion, they found oregano essential oil (at low concentration) and MAP exhibited an additive preservation effect of the uncooked chicken breast (For the full study, click here).
Click here for more information on MAP gas blenders.
modified atmosphere packaging
A recent study, published in TResearch, the Teagasc research and innovation magazine, examined the effect of modified atmosphere packaging (MAP) on the bioactives in carrots.
Bioactives refer to natural compounds found in foods that reduce the risk of one or more diseases. Carrots are rich in polyacetylenes that have been correlated to a reduced risk of certain cancers and a variety of other diseases. The compound Falcarinol has been identified as the most active polyacetylene in carrots in terms of its effect on cancer cells in research studies. Dr. Juan Valverde and colleagues focused on a variety of polyacetylenes in carrots that had undergone MAP versus those that had not. MAP is a common way of packaging carrots “sticks” and “chips” for sale.
In their study, two different gas blends were used. Gas 1 consisted of 5% CO2, 5% O2 and 90% N2 while Gas 2 contained 10% CO2, 80% O2 and 10% N2. In addition, each gas blend was used with both polyester -polyethylene and a polyamide-based
breathable material in order to evaluate the effect of the packaging itself. All samples were stored at 4°C for six day with polyacetylene levels determined at days zero, three and six.
The results of the study were clear. Modified Atmosphere Packaging did not diminish the level of any of the three major polyacetylenes found in carrots when compared to the controls.
To read the full article, click here (pdf, page 20).
modified atmosphere packaging
Do you buy precut and packaged veggies? Bagged salad? Packaged meat or seafood? Cheese? Then you most likely have purchased food enveloped in a modified atmosphere. More and more food packaging companies are utilizing Modified Atmosphere Packaging (MAP) or Equilibrium Modified Atmosphere Packaging (EMAP) to preserve the shelf life and/or appearance of their packed food.
What, you might ask, does that mean? And why are they packaged that way? Are there any risks? There is a great deal of research on MAP and EMAP, the proper gase mixtures, temperatures, methods and packaging materials. We'll just look at the tip of the proverbial iceberg.
Modfication of the packaged atmosphere attempts to lower the oxygen level and increase the carbon dioxide level to slow bacterial growth and the respiration of fruits and vegetables. Carbon monoxide may also be introduced to keep the red color of fresh meats by binding to the hemoglobin. We'll go back to that in a minute. The atmosphere can be introduced to the package by flushing or by exposure through a permeable membrane (EMAP). For more on the process and MAP systems, click here.
Back in the 1930's, ships transporting fruits pumped high levels CO2 into the storage rooms to increase shelf-life. By the 1970s, modified atmosphere packaging was appearing in your local stores, primarily for meats and fish.
In the years since, the technology and the science has rapidly developed and evolved. MAP is used in numerous circumstances. In each case, the gas mixture and the packaging materials are selected to optimize the conditions for the items being packaged. Foods such as meat, fish and cheese are non-respiring, meaning they do not need breath. For these, a film that does not allow gas exchange is used to hold in the MAP gases that are introduced during packaging.
Items that breath (fruits and vegetables) must be treated differently. They must be given enough oxygen to "breathe" while still extending shelf life. A more permeability packaging film allows an optimal equilbrium of oxygen and carbon dioxide to be created.
There is no direct risk to consumers based on the use of MAP or EMAP. In recent years, there has been debate regarding the use of carbon monoxide (CO) in the packaging of red meat. While no risk was found in the use of low levels of CO, the fact that CO maintains the color of the meat and can, in that way, hide visual evidence of spoilage was raised. The European Food Information Council (EFIC) released a report in 2004 reviewing the data. The report is available here.
The field continues to develop and expand as they attempt to minimize waste and loss in the delivery of food to consumers.
modified atmosphere packaging