The importance of respiratory fresh-keeping packaging for the preservation of fruit and vegetable products
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The fresh-keeping technology of fresh fruit and vegetable products is a relatively mature technology in developed countries and regions such as Europe and the United States, and has a history of more than 20 years. However, such technologies have not been widely used in the Chinese market. In the European and American markets, the shelf life of pretreated fruits and vegetables is generally 1 to 3 weeks (in the cold chain state of 0 to 4 °C), while the fresh pretreated vegetables in China have a shelf life of only 3 days in the whole cold chain state. This greatly limits the logistics and sales range of fresh fruit and vegetable products, and it is also extremely easy to cause huge waste of resources.
Therefore, it has become very important to develop a respiratory fresh-keeping package suitable for the preservation of fruit and vegetable products in China. In this paper, the author verified the effectiveness and importance of the respiratory fresh-keeping packaging to extend the shelf life of fresh fruit and vegetable products through the case of soybean sprouts breathing fresh-keeping packaging. I would like to share with you, I hope to be inspired by the industry research and development related products.
Design of respiratory fresh-keeping packaging
The design process of respiratory fresh-keeping packaging products can be divided into four steps: 1 to study the respiratory process of fruit and vegetable products and the factors affecting breathing; 2 to comprehensively consider the packaging needs of customers, including capacity, machinery, storage and transportation environment, etc.; 3 according to fruit and vegetable products Respiratory rate, well-designed packaging structure and packaging respiration rate; 4 actual tests verify the effect of extending the shelf life.
1. The breathing process of fruit and vegetable products
Whether it is a newly harvested fruit and vegetable product or a pre-processed product, it is alive and has a breathing process throughout the life cycle. The breathing of fruit and vegetable products is divided into two categories, namely aerobic and anaerobic respiration (the basics of the introduction of these two aspects, I will not repeat them here), these two ways of breathing will affect the preservation effect of the package.
2. Analysis of factors affecting the respiration rate and shelf life of fruit and vegetable products
The respiration rate of fruit and vegetable products directly affects its shelf life. The higher the respiration rate, the faster the corrosion rate, and the shorter the shelf life, and vice versa. The factors affecting the respiration rate of fruit and vegetable products are mainly as follows.
(1) Product category
The product type is the biggest factor affecting the respiration rate. For example, the respiration rate of leafy vegetables is significantly higher than that of carrots and other root vegetables.
(2) Processing and pretreatment of products
For example, peeled, shredded and washed potato silk, the breathing rate is significantly faster than the whole potato. That is, any treatment that destroys the integrity of the product, such as cutting, bumping, etc., will speed up the breathing rate of the product itself.
(3) Ambient temperature of the product
For every 10 °C increase in the ambient temperature of the product, the breathing rate will increase by 2 to 3 times.
(4) Environmental oxygen/carbon dioxide content
The oxygen content in the environment is high, and the respiration rate of fruit and vegetable products is fast, and vice versa. Breathing and fresh-keeping packaging technology is to adjust the oxygen/carbon dioxide content in the package through the respiration of the packaging film, so as to extend the shelf life of the fruit and vegetable products.
(5) Agricultural factors such as growing conditions and seasons of crops
These aspects depend on the origin of the fruit and vegetable products, but the origin is difficult to change and quantify.
(6) Maturity at the time of picking
For products that are too old or too old, the breathing rate will be very fast.
(7) Microorganisms
Microorganisms that grow on the surface of fruit and vegetable products accelerate the process of decay.
(8) Ethylene content in the environment
Ethylene is a catalyst for the "aging" of fruit and vegetable products. Some products are very sensitive to ethylene, and some products themselves produce ethylene.
The preservation technology of fruit and vegetable products is a comprehensive technology, and only when the various links are properly controlled can the desired effect be achieved. Designing a fresh-keeping package with a suitable breathing rate is one of the essential core tasks for the preservation of fruits and vegetables, while packaging that does not have a respiratory function cannot achieve the preservation effect.
3. Breathing and fresh-keeping packaging design
The design of respiratory fresh-keeping packaging needs to comprehensively consider the requirements of respiratory preservation of fruit and vegetable products and the basic functional requirements of customers for packaging.
(1) Respiratory preservation requirements
Respiratory fresh-keeping packaging needs to discharge the carbon dioxide exhaled from the fruit and vegetable products, and inhale the oxygen required for aerobic respiration of the fruit and vegetable products; it is necessary to avoid the occurrence of anaerobic respiration and to reduce the rate of aerobic respiration as much as possible.
(2) Water dispersion loss requirements
Respiratory fresh-keeping packaging should reduce the loss of water, prevent fruit and vegetable products from becoming cockroaches, and maintain a crisp state.
(3) Basic packaging requirements
Respiratory fresh-keeping packaging needs to have good mechanical strength, can run well on packaging equipment, and has good heat-sealing effect. It also needs to consider properties such as transparency and waterproof fog.
4. Respiratory preservation packaging test verification
It can be seen from the above analysis that the respiratory fresh-keeping packaging must be specially designed and matched according to the different needs of the specific packaged products, especially according to the respiration rate of the fruit and vegetable products. Therefore, testing and verifying the designed packaging is one of the important aspects of packaging design, and it is also a process that can visually explain the function of breathing fresh-keeping packaging with data.
The test verification process needs to package the real content and perform real simulation tests on the storage, transportation and sales links. The test content of the verification process usually includes two aspects: one is the oxygenation/carbon dioxide content in the data test package; the other is the comprehensive evaluation of the performance of the packaged product, usually including the smell, appearance, feel and so on. Of course, if you can simultaneously test indicators such as microbes and specific composition changes, the test results will be more perfect.
Figure 1 and Figure 2 show the oxygen/carbon dioxide content curves in the ideal respiratory fresh-keeping package and non-preservation package. The ideal respiratory fresh-keeping package can keep the oxygen in the bag at a low level and the carbon dioxide is at a high level. The slow aerobic respiration process is maintained; instead of the fresh-keeping packaging, the gas content in the packaging bag cannot be adjusted, the oxygen in the packaging bag is quickly consumed, and the fruit and vegetable products enter the anaerobic respiration process, thereby causing the fruit and vegetable products to quickly spoil.
Soybean sprouts normal temperature breathing preservation packaging case analysis
Based on the above design of respiratory fresh-keeping packaging, the author made a research and analysis on a yellow bean sprout respiratory fresh-keeping packaging. The storage and transportation environment of the soybean sprouts is normal temperature, and the normal temperature in the summer of South China means that the product will be at a temperature of about 30 °C for a long time. This situation is different from the whole process of the cold chain in the European and American markets, but can be extended according to the above theory, through a reasonable respiratory fresh-keeping packaging design, to extend the shelf life of soybean sprouts.
1. The original condition of fresh soybean sprouts packaging
The product in the package is fresh soybean sprouts weighing 300g. The original packaging film is ordinary PP film. The storage and transportation conditions are normal temperature environment, and the original shelf life is <15 hours.
Customer Description: During the sales process, the bean sprouts have been emitting a sour smell, only to control the taste within an acceptable range.
The original production and sales operation of soybean sprouts is shown in Figure 3.
2. Customer expectations for respiratory fresh-keeping packaging
Keep the existing operation links unchanged, so that the shelf life of soybean sprouts at room temperature is stable for 24 hours.
3. Development and testing of respiratory fresh-keeping packaging
Based on theoretical analysis and calculation, we designed the corresponding respiratory fresh-keeping packaging for soybean sprouts. For comparative testing and analysis, the original packaging film and the respiratory fresh-keeping packaging film were compared and tested, and another film with a lower breathing rate was used for comparison.
(1) Test packaging film
The original film is the original ordinary PP film of the customer; the A film is a newly designed respiratory fresh-keeping packaging film; the B film is a respiratory fresh-keeping packaging film with a breathing rate of about 1/2 of the A film.
(2) Test verification conditions
Under the more severe conditions, we compared the three types of packaging films of the original film, A film and B film. The test conditions are as follows.
Packing products: Take 300g of bean sprouts online at the same time; test the ambient temperature is 27~30°C, keep the temperature, no ice cubes to cool down; Packing time: consistent with normal products, packed at 21:00 in the evening.
This test condition is more demanding than the customer's original logistics and sales. Because the packaging test process has been in the high temperature environment of 27 ~ 30 ° C, and the customer's conventional logistics links usually use ice cubes to cool down, before the arrival of the supermarket sales, the product environment can be maintained at around 18 °C.
(3) Oxygen/carbon dioxide content tracking test and analysis
The measured oxygen/carbon dioxide content curve is shown in Figures 4 and 5. It can be seen from the test results that the original membrane (ordinary PP membrane) has a measured oxygen content close to zero after being loaded with the soybean sprouts for 3 hours, that is, it quickly enters an anaerobic respiration state. As anaerobic respiration progresses, the amount of carbon dioxide in the package continues to rise to about 50%. After 18 hours, the contents were completely corrupt and inedible.
The A film keeps a certain amount of oxygen within 24 hours after loading the bean sprouts, maintaining the slow sprouting of the bean sprouts, and the carbon dioxide content is up to 20% to 25%.
The B film is also a respiratory fresh-keeping packaging film, but the breathing rate is about half that of the A film. After 15 hours of loading the bean sprouts, the internal oxygen content was measured to have dropped to an extremely low level, and the bean sprouts entered the anaerobic respiration and eventually spoiled.
(4) Comprehensive evaluation of soybean sprouts
During the test, a comprehensive evaluation of the bean sprouts opening was carried out, and the evaluation results are shown in Table 1. In the comprehensive evaluation, the difference between the original film and the respiratory fresh-keeping packaging film is reflected in the following aspects.
Shelf life of breathable plastic wrap: After 24 hours, the product status is still very good, that is, the actual shelf life is much higher than 24 hours.
Odour difference: Soybean buds in the normal packaging have always been sour and smelly; while the bean sprouts in the respiratory fresh-keeping package have remained fresh.
Differences in color and appearance: The color of the bean sprouts in the ordinary packaging becomes darker and effluent, and the signs of corruption are obvious; the yellow bean sprouts in the respiratory fresh-keeping package are slightly greenish, with no signs of spoilage, such as signs of slight growth and aging.
In conclusion
Through the test analysis of the soybean fresh bean bud fresh-keeping packaging, we can draw the following conclusions.
(1) Respiratory fresh-keeping packaging technology can effectively extend the shelf life of fruit and vegetable products.
(2) The breathing rate of the respiratory fresh-keeping package must match the breathing rate of the fruit and vegetable products, otherwise the effect of prolonging the shelf life of the fruit and vegetable products is not obvious.
(3) The respiratory fresh-keeping packaging of fruit and vegetable products needs to be designed and tested according to the breathing characteristics of the product to achieve the desired fresh-keeping effect.