Hydroxymethylfurfural (HMF), colour. It is a complete index of the quality of foods submitted to heat treatment, which reflects the degree of developing the degradation processes in the product. HMF is an intermediary product and is the result of the so-called Maillard reaction, forming melanoidine in the process of tomato drying. Melanoidine - dark coloured compounds are the products of reactions between reducing sugars and components containing the aminic group (aminoacids, proteins, etc.).