How does the ketchup spout bag keep fresh by sealing?

In the process of food packaging innovation, the ketchup spout bag, as a packaging form with unique advantages, is gradually changing consumers' perception of ketchup storage and preservation. Its excellent preservation ability depends largely on good sealing, and how this feature plays a key role in maintaining the quality of ketchup is worth further exploration.

From the microchemical level, the composition of ketchup is complex, including a variety of organic substances, such as sugars, organic acids, proteins, and oils rich in unsaturated bonds. Among them, unsaturated fatty acids and natural pigments are extremely sensitive to oxygen. Oxygen, as a strong oxidant, is very easy to react with these ingredients when it comes into contact with ketchup. Taking unsaturated fatty acids as an example, the carbon-carbon double bonds in their molecular structure will undergo a free radical chain reaction under the action of oxygen. During the reaction, oxygen molecules will attack the double bonds to form peroxide free radicals, which will then trigger a series of complex oxidation products. These products will not only change the flavor of the ketchup, causing it to produce an unpleasant "rancid taste", but also destroy the nutritional components of the ketchup and reduce its nutritional value. However, the conjugated double bond structure of natural pigments such as lycopene is easily destroyed in an oxidative environment, causing the original bright red color of ketchup to gradually fade and become dull.

The design of the ketchup spout bag fully considers the need for oxygen barrier. Its sealing structure adopts a precise process, whether it is a common press-type nozzle or a more complex screw-cap nozzle, it can form a tight fit when closed. This fit is not a simple physical contact, but through special materials and structural design, it greatly reduces the passage for air to enter. From the material point of view, the spout bag usually uses a multi-layer composite polymer material. The outer layer is generally a material with good mechanical strength and printing adaptability, such as biaxially oriented polypropylene (BOPP), which can protect the internal structure and provide a beautiful printed display surface; the middle layer is the key barrier layer, and the common one is ethylene-vinyl alcohol copolymer (EVOH). This material has a very low oxygen permeability and can effectively block the invasion of external oxygen; the inner layer is mostly polyethylene (PE) with good heat sealing properties, ensuring that it can be firmly composited with other layers during processing and provide a safe and hygienic contact interface for ketchup.

When the consumer has finished using the ketchup, he closes the nozzle, and the entire nozzle bag forms a relatively closed space. Due to the tight fit of the seal and the barrier properties of the material itself, oxygen molecules need to overcome many obstacles to enter the bag. Compared with traditional packaging, this design significantly reduces the rate of oxygen entry. In traditional open packaging, oxygen can freely contact the ketchup over a large area, and the oxidation reaction is rapid and comprehensive. The nozzle bag presses the ""slow down button"" for the oxidation reaction of ketchup by reducing the entry of oxygen. Under the slow oxidation process, the oxidation rate of unsaturated fatty acids in ketchup is greatly reduced, thereby effectively maintaining its original flavor. When eating, consumers can still taste the rich, mellow, sweet and sour ketchup flavor, rather than the sauce that produces odor due to oxidation. Due to the reduced degree of oxidation of natural pigments, the color of ketchup can maintain a bright red color for a long time, which can visually stimulate consumers' appetite. From a nutritional perspective, the degree of damage to various nutrients due to oxidation is reduced. While enjoying the delicious taste, consumers can also ingest richer nutrients. Antioxidants such as vitamin C and vitamin E are better preserved, providing more protection for health.