Why we as food profesionals prefer the (fresh milk) than (UHT milk), from processing side and nutrition side ?

Ultra-pasteurization is an extremely harmful process to inflict on the fragile components of milk.  Milk proteins are complex, three-dimensional molecules, like tinker toys. They are broken down and digested when special enzymes fit into the parts that stick out. Rapid heat treatments like pasteurization, and especially ultra-pasteurization, actually flatten the molecules so the enzymes cannot do their work. If such proteins pass into the bloodstream (a frequent occurrence in those suffering from “leaky gut,” a condition that can be brought on by drinking processed commercial milk), the body perceives them as foreign proteins and mounts an immune response. That means a chronically overstressed immune system and much less energy available for growth and repair.

% free from microbial contamination , and nutritional loss was very less

UHT causes loss of nutritional content due to high temperature processing, it howerver has the benefits of a longer shelf life which causes it, to be popular among the public.