Share of food in total consumption expenditure has been coming down as per capita income grew over time in last sixty years because

The phenomenon described is a classic application of Engel's Law, which states that as household income increases, the proportion of income spent on food decreases, even if the absolute expenditure on food rises [2]. This occurs because the income elasticity of demand for food is typically between 0 and 1, meaning food demand is income-inelastic [2]. Consequently, while people may diversify their diets toward higher-value items like meat, fruits, or processed foods as their disposable income grows [4], the growth rate of food expenditure remains lower than the growth rate of per capita income [2]. Over the last sixty years, as per capita income has risen, households have allocated a larger share of their budget to non-food items such as health, education, and recreation, leading to a declining share of food in total consumption expenditure [2].

Sources

1. [1] https://pmc.ncbi.nlm.nih.gov/articles/PMC2935126/
2. [2] https://en.wikipedia.org/wiki/Engel%27s_law
3. [4] Indian Economy, Vivek Singh (7th ed. 2023-24) > Chapter 12: Supply Chain and Food Processing Industry > Facts of Food processing sector/industry in India: > p. 364