The most economical process of increasing the nutritive value of food grains is milling.

Milling is the process of removing the outer layers of grains, such as the bran and germ, to produce refined grains. This process helps to increase the nutritional value of the grains by removing impurities and improving their digestibility.

Germination, which is option 1, is a process in which the grains are soaked in water to initiate the growth of a new plant. While germination can enhance the nutritional composition of grains by increasing the availability of certain nutrients, it is not always the most economical process as it requires additional time and resources.

Parboiling, which is option 3, involves partially cooking the grains in boiling water before milling or further processing. This process can also enhance the nutritional value of grains by making certain nutrients more available for absorption. However, it may not always be the most economical option as it requires additional cooking time and energy.

Pearling, which is option 4, is a process of removing the outer husk or seed coat from grains. While this process can improve the appearance and texture of grains, it may not significantly increase their nutritional value.

Therefore, based on these considerations, milling is the most economical process for increasing the nutritive