The role of macromolecules in materials in puffing
1. The role of starch in puffing
The content and distribution of water in starch pellets depend to a large extent on the density of polysaccharide chains and the regularity of stacking. This is very important for the physical and chemical properties and puffing processing characteristics of starch.
Under hot pressing conditions, the changes inside the pellets roughly involve four different processes:
① Introduce bound water to the crystallite area;
②Limited wetting and swelling of the gel phase in the amorphous zone;
③The melting of the crystallites, and the co-hydration and wetting of the melted crystallites and the amorphous gel zone at the same time;
④The hydration of the molten crystallites leads to the redistribution of water in the pellets, and finally the stress generated by the wetting and swelling causes the crystallites to deform and accelerate the melting.
2. The role of protein in puffing
In the process of puffing, protein, as a component of puffed materials, is mainly because the structural protein is easily affected by external energy and undergoes molecular structure changes, such as deformation and denaturation. Such changes in structural proteins usually occur simultaneously with their functional changes in the expansion process.
The main functions of protein in the puffing process are:
① Maintain part of the water content of the material by means of hydration, hydration water retention, membrane encapsulation water retention and network structure water absorption.
②As a plastic wall material for a closed gas chamber, it achieves expandable stretching and gradual denaturation when the gas expands, and then it is solidified due to the drying effect of water loss and self-carrying heat during the instantaneous rupture of the chamber wall and steam leakage.