The acts of buying foodstuffs needed to prepare meals is known as

Purchasing means buying items you need. When you go to the market and buy food ingredients, you are purchasing foodstuffs.

The purchasing process involves selecting items and paying for them. This is different from planning (budgeting) or storing (preserving) food.

Budgeting is planning money. Preserving is storing food. Pricing is setting costs. Only purchasing describes the act of buying foodstuffs.