Gıdalarda renk değişikliklerine neden olan başlıca enzimatik olmayan esmerleşme reaksiyonları karamelizasyon, askorbik asit degradasyonu ve Maillard reaksiyonudur. İşlem görmüş gıdaların kalitesi üzerinde başlıca rolü üstlendiğinden dolayı Maillard reaksiyonu, en önemli esmerleşme reaksiyonu olarak ele alınmaktadır. Maillard reaksiyonu indirgen şekerler ve amino grupları arasında gerçekleşmektedir ve esmerleşme düzeyi gıdanın bulunduğu ortam koşullarına göre değişmektedir.    

Nonenzymatic browning reactions which cause color changes in foods are mainly caramelization, degradation of ascorbic acid and Maillard reaction. Maillard reaction is considered the most important browning reaction because it undertakes the main role in the quality of processed foods. Maillard reaction takes place between reducing sugars and amino groups and the intensity of browning changes according to conditions of food media.Maillard reaction cause also formation of antioxidative and antibacterial compounds as well as compounds that give characteristic taste and odor to tots of foods such as bread, coffee and meat. In addition to this, it is known that some of products occurred during Maillard reaction possess mutagenic properties. Because of aminoacids which take role into its formation, Maillard reaction causes also loss of nutrition in foods.