Food technology is the part of biotechnology. Biotechnology have wider scope.

Biotechnology and agricultural engineering are very different. B.tech in biotechnology deals with the use of microorganisms such as bacteria or yeasts or biological substances.

B.tech in agricultural engineering deals with farm machinery, food processing, soil and water engineering.

All the course have good scope but agricultural engineering have good scope in both private as well as public sector and rest depends on your interest.