Fresh fruits and vegetables are an integral part of the human diet, and their preservation during storage and transportation is extremely important. The use of modified atmosphere packaging can significantly extend the shelf life of fresh fruits and vegetables and reduce food waste. Modified atmosphere packaging is based on the differences and changes in the respiration of fresh fruits and vegetables, and the permeability of packaging materials can dynamically adjust the oxygen and carbon dioxide content inside the packaging, slow down the respiration rate of fruits and vegetables, inhibit the growth and reproduction of microorganisms and the generation of ethylene, so as to prolong the shelf-life of fresh fruits and vegetables.
The effect and quality of modified atmosphere packaging are affected by many factors, mainly including the respiration rate of fruit and vegetable products, gas composition, characteristics of packaging film, packaging capacity, storage temperature, humidity, etc. Modified atmosphere packaging can be applied to a variety of fresh fruits and vegetables, as well as fresh-cut fruits and vegetables, including cantaloupe, apples, grapes, strawberries, blueberries, pineapples, carrots, tomatoes, celery, lettuce and broccoli, etc.
Factors affecting the quality of modified atmosphere packaging for fresh fruits and vegetables
The modified atmosphere packaging quality of fresh fruits and vegetables mainly depends on the packaging material, gas ratio, storage environment temperature, and many more details
The packaging material is the most important part of the modified atmosphere packaging of fresh fruits and vegetables. MAP packaging material must have high gas barrier properties to ensure that the mixed gas in the packaging does not leak. With the development of polymer materials, polymer films are increasingly used in modified atmosphere packaging materials. At present, polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), biaxially oriented polystyrene (BOPS), polystyrene (PS) ) shrink film, polybutadiene (PB) stretch film, ethylene-vinyl acetate copolymer film (EVA), etc. are all polymer film materials commonly used in MAP packaging. In the production of films, different process technologies and filling ingredients can be used to manufacture suitable packaging materials. The following table lists the properties of common food packaging materials.
|Packaging material||WVP water vapor permeability （g/m2▪d）||OTR oxygen transmission rate （cm3/m2▪d▪atm）||CO2 transmission rate（cm3/m2▪d▪atm）||Melting temperature （℃）|
Many studies have clarified the preservation properties of various materials for modified atmosphere packaging of fresh fruits and vegetables. Some studies have used different polyethylene plastic wraps to package the Agaricus bisporus, and found that the browning intensity, physiologically related enzyme activities and the content of senescent substances are lower than those of the unpackaged control group, which can better prolong the shelf life and maintain the quality of product
Relevant studies have found that modified atmosphere packaging with different thicknesses of film has a significant effect on the storage quality of peaches. The determination of total sugar content, weight loss rate, titratable acid content, and changes in the volume fraction of O2 and CO2 in the packaging show that modified atmosphere packaging can significantly preserve the honey. Peaches can titratable acid levels and inhibit the reduction of their total sugar content.
New packaging materials
Oxidation reaction is one of the main reasons for food spoilage, so the use of film materials with antioxidant activity to package fresh fruits and vegetables has gradually become a trend in recent years.Antioxidant active film is by adding antioxidants to packaging materials or coating them on packaging materials, and within a certain time or space, the active antioxidants inside the packaging materials can be released to the inside of the packaging at a slower rate, so as to prevent food pollution.
The rapid development of nanotechnology has provided some new methods in the field of food preservation. In the research of fresh food modified atmosphere packaging, the addition of nanoparticles can improve the mechanical properties, biodegradability, and antibacterial properties of the packaging film. The traditional packaging film has insufficient regulation of CO2 and O2 permeation. Nano cling film can solve this problem. After adding certain ingredients, it can also achieve special effects such as anti-mildew and antibacterial. However, there are few types of film-forming substrates for nano cling film, and the cost is relatively high.
Gas mixture ratio
Gas mixture ratio means the mixing ratio of oxygen, carbon dioxide and nitrogen in the modified atmosphere. For fruits and vegetables, the concentration of O2 and CO2 in the storage environment is one of the important factors affecting the respiration rate. Vacuum packaging can inhibit respiration and oxidation reaction, but it is not suitable for the packaging of fresh fruits and vegetables, because the anaerobic respiration of fruits and vegetables will speed up the spoilage of fresh fruits and vegetables. Modified atmosphere packaging technology can effectively make up for the shortcomings of vacuum packaging and effectively improve the shelf life of fresh vegetables.
Using modified atmosphere packaging to keep betel nut fresh, through the measurement and calculation of the respiration type and rate of betel nut, the test shows that the temperature is 6 ℃, and the gas composition is O2: CO2: N2 = 2%: 5%: 93% is active modified atmosphere packaging and optimal parameters for storage temperature. For the modified atmosphere packaging of mushrooms, the storage temperature is 4℃, and the initial gas concentration is O2:CO2=15%:5%, which has the lowest breathing intensity and the best storage effect. High CO2 concentration can better maintain the integrity of the cell wall of Pleurotus eryngii, and maintain a higher content of cell wall proteins and polysaccharides.
Storage temperature is closely related to the respiration of fresh fruits and vegetables, so it also directly affects the shelf life of fresh fruits and vegetables in modified atmosphere packaging. At higher temperatures, fruits and vegetables have vigorous respiration and metabolism, rapid physiological changes, rapid water loss, and reduced quality of fruits and vegetables. If the temperature is too low, chilling damage may occur, resulting in imbalance of physiological metabolism and shortening the life of fruits and vegetables. Moderate cooling can reduce respiration to the lowest value that does not affect normal physiological functions, inhibit the consumption of nutrients, and maintain good nutritional and sensory quality. The following table shows the optimal gas mixture ratio and storage temperature of several kinds of fruit and vegetable in modified atmosphere packaging.
|Product||Gas mixture ratio||Storage temperature （℃）|
|Apple||2~3% O2/1~2% CO2/97~95% N2||0~5|
|Strawberry||10% O2/15~20% CO2/70~75% N2||0~5|
|Pear||2~5% O2/3~10% CO2/85~95% N2||5~13|
|Broccoli||1~2% O2/5~7% CO2/91~94% N2||0~5|
|Lettuce||2~5% O2/0~2% CO2/93~98% N2||0~5|
|Mushroom||10~15% CO2/85~90% N2||0~5|
|Tomatoes||3~5% O2/95~97% N2||5~13|
In addition to the above factors, the quality of modified atmosphere packaging of fresh fruits and vegetables also depends on parameters such as the respiration rate of fruits and vegetables, the weight of fruits and vegetables, the thickness of the packaging film, the air permeability and the surface area of the container, which need to be fully considered before launching the project.
How to design a modified atmosphere packaging scheme for fresh fruits and vegetables
Due to the variety of fruits and vegetables and the complexity of the environment, the design of modified atmosphere packaging for fresh fruits and vegetables is a complex project. The general process is as follows:
(1) First, determine the target modified atmosphere environment in the package that can maximize the shelf life. This information can be obtained by searching the literature, or by preliminary experiments to obtain the most correct modified atmosphere components of fruits and vegetables.
(2) After the target modified atmosphere environment is determined, the next step is to determine the respiration quotient and respiration rate of the packaged fresh fruit in the target environment. This can be done by experimental measurement or establishment of a fresh fruit respiration model. Trends are simulated and forecasted.
(3) Determine the relevant parameters of the packaging film. You can first determine the thickness, specifications, and loading of fruits and vegetables of the packaging film, and then calculate the gas permeability of the required packaging film according to the target gas concentration and the respiration rate of fruits and vegetables, and find the film material that is closest to the ideal value.
(4) A verification test is required. The verification includes two aspects: ① whether the target gas concentration can be formed and maintained in the packaging container according to the expected design purpose; ② whether the package effectively extends the shelf life of the packaged fruit. If the verification result meets the intended purpose, the designed packaging parameters are valid. Otherwise, parameter design and experimental verification need to be repeated.
Fresh fruits and vegetables modified atmosphere packaging machines
After determing all the other factors that effect MAP packaging quality, including gas mixture ratio, packaging material, storage environment, and so on, the last step to launch the modified atmosphere packaging project for fresh fruits and vegetables is packaging machines. We manufacture and supply various types of MAP packaging machines fit for packaging of fresh fruits and vegetables, according to the machine specifications and packaging materials they use, :
1. Modified atmosphere packaging machine uses rigid tray and flexible top sealing film: This series of MAP machine can do the REAL modified atmosphere packaging by vacuum the air out of the rigid tray and replace it with a premixed atmosphere. The rigid tray can be premade of thermoformed by the MAP machine itself. For machine details, please visit the product page.
2. Double chamber vacuum packaging machine and rotary premade pouch sealing machine with gas filling function, use premade vacuum bags: This machine also use the vacuum-gas filling process to replace the atmosphere inside the bags with nitrogen or mixed gas to prolong shelf life of fresh vegetables and fruits. Following video for reference
3. HFFS flow wrapping machines with gas flushing function: HFFS flow wrapping machine automatic packs and wraps fresh fruits and vegetables with a roll of plastic film. Before the package is sealed, the machine can flush nitrogen into the package to prolong shelf life of products. This is an optional function for HFFS flow wrapping machine.
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