All it depends on your interest, as the name suggest food quality assurance has very limited application, just quality assurance, that too in foods/flavors/dairies that will be the extend of your job opportunities.

The other degree food science and technology has much wider scope, it opens the door to production floor, where pure science grads will not cut it. And being a food science and technology grad you always have a chance to go to assurance side.

After completing Msc in food technology and quality assurance you can become a food technologist.

As a food technologist, you need to:
Provide correct information for labeling of food
Research ways to improve the freshness of food
Find quick and cheap ways of producing food
Test the quality of food
Understand and ensure the safety of food

You can even go for specializations in the below mentioned fields:

Cereals
Dairy
Sugar
Alcohol
Bakery and confectionary items
Fruits and vegetables
Meat/fish
Oil and oil seed processing

You can earn upto 20-30 K initially depending upon your skills and experience if any.

Hope this helps.
Good luck!