Explain about the Browning Reactions?

The Browning Reactions are complex reactions which occur when foods are processed. In some the brown flavour is highly desirable and is intimately associated in our mind with the delicacy of the product. In coffee, maple syrup, the brown crust of bread and all baked goods, potato chips, roasted nuts and many other processed foods controlled browning is necessary. Yet in other foods, browning during processing is undesirable and forms off flavour and dull appearance or even objectionable colors. In drying of fruits or vegetables and in canning or concentrating orange juice, it is highly desirable to avoid browning. The presence of carbohydrates in foods is intimately connected with the browning, which occurs. Other compounds are sometimes important but they are the ones which have some of the reactive groups of the reducing sugars and are similar to them in properties. The pigments, which are formed, are high molecular weight polymers whose constitution is difficult to determine. The browning reactions appear to be complicated not only as to the final product but also as to the course of numerous reactions. It has been exceedingly difficult to assess the chemistry of this change in the complex mixtures, which is encountered in almost every food.