Under ultra-high pressure food packaging
The latest advances in high pressure technology of high pressure technology is the current concern, and the countries extensive study of a food high-tech. It is put flexible packaging food in sealed, high strength, pressure vessels, water or mineral oil as pressure transmitting medium for the imposition of the 100MPa one to 1000MPa the hydrostatic pressure and to maintain a certain amount of time to achieve sterilization blunt enzyme molecules modification and change some of the effects of physical and chemical reactions speed. In recent years, with consumers increasingly high demand for fresh food, nutrition, safety and functionality, greatly promoted the ultra-high pressure food processing technology, basic research and industrial processes (iv) inflatable bags. In August 2004, the U.S. Department of Agriculture Food Safety Inspection Service (USDAFsIS) approved HPP technology for ready-to-eat foods such as cooked meat.
Pressure assisted thermal sterilization process can be used for low acid food sterilization. , Fruit and vegetable products, jams, fruit juice products, ultra-high pressure processing technology matures, the continuous pressure treatment full aseptic packaging rice, rice cakes, rice desensitization and rice, semi-finished products have been successfully listed, high pressure technology in the oyster, sea cucumber , salmon, shrimp and other aquatic applications have obvious advantages. In addition, high pressure technology is also used in yogurt, pickles and other fermented foods.
Not yet covered by the state of aggregation changes in packaging materials under the HPP role and ignores the volume compression and compression of the thermal effect has a better flexibility of HPP packaging materials, by one or more of the different nature of the monomer polymerization. From the molecular scale, we can form linear, star, comb, random grafting and cross-linked like polymer. Their aggregation state is different from low molecular weight compounds, but under different thermodynamic conditions, with its unique three forms exist: that is, the glassy state, the state of high elasticity, and viscous flow regime. In principle, various forms of molecular motion and change under external pressure stress caused by the polymer physical properties change, embodied in the microscopic structure of the main aggregation transition of the polymer, the polymer motor unit rotation, moving ( rearrangement exercise), the thermal motion of polymer conformational state (spatial form), the molecular stacking mode change and the phase transition, and the bond breaking of the molecular chain, thereby affecting the macroscopic properties of packaging materials.

 

HPP volume compression effect is also a factor to be considered, 600MPa pressure the volume of water can be compressed 15v/tCz3- archery, atomic or molecular spacing of shortening caused by changes in the material structure (crystal structure, molecular structure, atomic arrangement mode), thereby causing the electronic structure rearrangement changes affect other properties. And ultra-high pressure, the polymer reversible converted to atmospheric pressure crystalline (polymorphic changes) to reduce the pressure and then restore the original crystalline state and crystalline state of polymers has a direct relationship with the properties of the materials. Better the higher the usually higher degree of crystallinity, molecular compound strength, hardness and stiffness, heat resistance and chemical stability, chain-related performance, such as flexibility, elongation, impact strength, the lower. In addition, HPP will lead to the heat of compression [23.2a], temperature changes will affect the movement of molecular chains leading to stress, so that material properties change.
Our ultra-high pressure food already begun in the mid-1970s, during the "Eleventh Five-Year" period, but also independent successful development of the processing capacity of 500L, the largest to deal with stress 700MPa, intelligent, continuous ultra-high pressure equipment, and to achieve industrial production equipment. Two the EHV role of food packaging technology to study the progress of food packaging materials and food in direct contact with the external environment, the formation of the barrier protective effects of food packages are complete, whether the superior packaging performance determines the final quality of the food container inflatable bags. Of HPP-based works. -194 Tang Yali, such as: food packaging issues in the ultra-high pressure under the thematic discourses foods are generally required in advance using a certain flexible packaging materials such as polyethylene (PE), polypropylene (PP), ethylene vinyl alcohol copolymer (EVOH) or composite PE / polyamide (PA), EVOH / PE, PP / EVOH / PP, PMPE packaging, then HPP deal with Sichuan. This means that a variety of packaging materials will be accompanied by all kinds of food, subjected to traditional heat the material mode of action and energy manifestations distinct physical field - the role of ultra-high pressure and subsequent storage and transportation.