Tuesday, June 18, 2024
Home Uncategorized Is it better to wrap vegetables and fruits in plastic wrap or directly expose them to the air?

Is it better to wrap vegetables and fruits in plastic wrap or directly expose them to the air?

by admin
0 comment

like the human body, food needs metabolism every day, and there is a process of “aging”. Fruits and vegetables will dehydrate, meat will rot, and processed products will mildew. In order to slow down the “aging” process of food and prolong the shelf life, various storage technologies such as cold storage, vacuum and heat treatment are widely used. Fresh-keeping film is one of the most simple and commonly used fresh-keeping methods

the fresh-keeping films have moderate air permeability and moisture impermeability. The fresh-keeping films made of different materials are wrapped outside the food. On the one hand, the proportion of oxygen and carbon dioxide around the fresh-keeping products can be adjusted; Second, it can maintain the moisture content in the bag and prevent the water loss in the food; Third, it can block the dust in the air and reduce the infection of bacteria, so as to prolong the fresh-keeping period of food

generally speaking, foods with proper use of preservative film can be kept fresh at room temperature for about a week. However, the fresh-keeping effect of fresh-keeping film is relative, and the fresh-keeping effect of fresh-keeping film with different quality and composition is very different. If the permeability of the membrane is poor, the carbon dioxide produced by food respiration cannot be emitted, and the water will deposit in the bag, resulting in chemical reaction and deterioration of the food

in addition, if the raw materials used in the production of preservative film do not meet the production regulations of healthy products, the harmful components in inferior raw materials may also penetrate into the food or react with the components in the food, which can not keep the food fresh, but turn the healthy food into harmful food. PVC, which is often mentioned recently, is one of the raw materials for making fresh-keeping film – PVC
at present, the fresh-keeping film circulating in the market is mainly processed from three kinds of raw materials: the first is polyethylene, which is called PE for short. Most household fresh-keeping films sold in supermarkets are made of polyethylene; The second is polyvinyl chloride, or PVC for short, which is often used to package cooked food, vegetables, fruits, bread, pastries, semi-finished products, etc. in supermarkets; The third is polyvinylidene chloride, PVDC for short, which is mainly used for the packaging of some cooked foods and ham

among the three raw materials, PE is recognized as the safest because it can not add any plasticizer in the production process. PVC and PVDC contain chlorine, so they are considered to have potential health hazards. Due to the high price of PVDC and the technical difficulty of film making process, there are few fresh-keeping films produced with PVDC as raw materials in the market. Relatively speaking, PVC is widely used in families and supermarkets. PVC is a thin film polymerized by a large number of vinyl chloride monomers added with processing aids under high pressure. Because PVC is a hard plastic, it must be added with a large amount of plasticizer to pull it into a transparent and soft fresh-keeping film

at present, most PVC fresh-keeping films used in the domestic market use DEHA as plasticizer. DEHA is a substance added to synthetic resin materials to increase the flexibility and elasticity of products. The content of DEHA in PVC fresh-keeping films is about 40% – 50%; In addition, dioctyl phthalate (DOP) is used as plasticizer, but the price of DOP is much higher than DEHA, so it is not commonly used

PVC itself is a super stable compound, non-toxic and harmless. However, the food packaging products produced by PVC contain free vinyl chloride monomer that is not involved in polymerization. A large number of animal tests and human epidemiological data show that vinyl chloride can induce liver cancer, lung cancer, gastric cancer and lymphatic cancer, and can cause chromosome abnormalities in animals and humans. Therefore, it is classified as a class of carcinogens by the International Center for cancer research (IARC)
in addition, DEHA, the plasticizer used in the production of PVC fresh-keeping film, can be released from the fresh-keeping film and infiltrated into food at room temperature, especially with foods with high fat content, such as meat products

when heating food, DEHA in the preservative film will also accelerate the release. The International Center for cancer research classified DEHA into three categories of carcinogens. DEHA will not only cause cancer to human body, but also cause endocrine dysfunction, reduce male reproductive function, and even cause mental diseases

in addition to the processing aids mentioned above, antistatic agent, smooth and anti adhesion agent, stiffening agent, heat stabilizer, antioxidant and barrier agent are also added according to different needs in the processing of food packaging film to ensure the transparency, flexibility, oxidation resistance and other properties of the film. However, these processing aids are composed of chemicals with different structures, which will gradually accumulate in the human body after long-term use, resulting in varying degrees of toxic and side effects or related diseases

■ identify materials and master several methods

because the price of polyethylene fresh-keeping film is reasonable and the safety is high, it can be used as the first choice for families when purchasing. Some consumers equate the household plastic wrap sold in supermarkets with the PVC plastic wrap described in the article, which is wrong

1. Transparency. The transparency of PE material is poor, and the color is white, and the covered food is blurred; PVC material has good gloss and looks clear and thorough, just like through glass

2. Flexibility. PE material is relatively soft, but its toughness is poor, and it can break after stretching; PVC material has strong toughness, can be greatly widened and elongated without breaking, and is easy to stick to hands<
combustibles. After PE fresh-keeping film is ignited by fire, the flame is yellow and will not go out when leaving the fire source. There is oil dripping and there is no pungent smell; The PVC fresh-keeping film contains chlorine. After being ignited by fire, the flame is yellow green without oil dripping. It will be extinguished after leaving the fire source, and has a strong pungent odor

although some fresh-keeping films comply with international safety standards and appear to be safe and non-toxic on the surface, some harmful substances such as DEHA have the characteristics of accelerated release in case of heat and oil

■ proper use is important

1. Avoid contact. Cover the utensils with fresh-keeping film and do not fill them to avoid touching food, especially meat and other foods with high fat content

2. Master the temperature. Pay attention to the temperature that the fresh-keeping film can withstand when heated, and heat it in strict accordance with the temperature marked on the brand, or choose a fresh-keeping film with better heat resistance

3. Container substitution. In daily life, we can have many substitutes that can replace fresh-keeping film, such as ceramic or glass containers. Such substitutes are safe, non-toxic and oil-resistant, which is conducive to ensuring human health.

You may also like

Leave a Comment

Soledad is the Best Newspaper and Magazine WordPress Theme with tons of options and demos ready to import. This theme is perfect for blogs and excellent for online stores, news, magazine or review sites.

Buy Soledad now!

Edtior's Picks

Latest Articles

u00a92022u00a0Soledad.u00a0All Right Reserved. Designed and Developed byu00a0Penci Design.