How to selectively choose values in a composite key in hadoop mapreduce

I have the following csv files with 5 columns and a number of rows. But I’m showing only first 6 rows.

Date,Food,Vitamin,Protein,NumStudents
01/01/17, Pasta, A, Yes, 560
01/01/17, Pizza, A, Yes, 730
01/01/17, Burrito, C, Yes, 240
02/01/17, Pizza, A, Yes, 340
02/01/17, Pasta, B, Yes, 450
02/01/17, Beef, B, Yes, 450

Now I want to find the sum of NumStudents on a particular day who had only Pizza and Pasta.

In essence for 01/01/17 I only have to sum NumStudents for Pizza and Pasta but not Burrito.

Expected Output

01/01/17 1290
02/01/17 790

Output I’m getting

01/01/17 1530
02/01/17 1240

In my code I’m able to sum NumStudents for all 3 types of food but don’t know how to selectively exclude some type of food from my composite key in mapper. Any idea how should I go about it?