C# :: Looping Through Text File And Recalculating Some Values

I have chosen C# as our language . Students have to enter a name of a recipe, followed by the number of people it will serve, followed by a list of ingredients for a recipe. This, then, needs to be exported to a text file. This bit I am fine with.

They then have to import the file back into C# and recalculate for a new number of people. This is the bit I am struggling with. The calculation is fine, I can do that. The issue is getting it to loop around each column of data to not only perform a calculation (I have just set it up to multiply by an entered value for now). I have set up a text file with the following data in it:

2 grams sugar
350 ml milk
4 tsp lemon
5 tsp vanilla
6 cloves garlic

I want it to come back with, (if multiplied by 2 for example) something like:

4 grams sugar
700 ml milk
8 tsp lemon
10 tsp vanilla
12 cloves garlic

At present, it comes back with

4 grams sugar
4 grams sugar
4 grams sugar
4 grams sugar
4 grams sugar

Code is below.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
namespace ConsoleApplication1{

[Code] .....