Fruits and Vegetables
Texture changes in fruits and vegetables can be related to transformations in cell wall and middle lamella polysac- charides due to enzymatic and non-enzymatic reactions [129]. Most of these changes are strongly influenced by the raw material properties, the (pre-) processing steps and conditions. Substrates, ions and enzymes which are located in different compartments in the cells can be liberated and interact with each other during heat treatment. Since pectic substances make up about 30 % of the dry matter in the primary cell wall and are the primary macromolecules of the middle lamella, chemical pectin changes play a role in process-induced textural changes: (1) enzymatic degrada- tion by the successive demethoxylation and depolymer- isation by pectin methylesterase and polygalacturonase, respectively, and (2) chemical degradation via a b-elimi- nation reaction or acid hydrolysis [150]