Encourage children in the kitchen as soon as they are able to imitate motions or activities that you are doing--usually between two and three years old.
Early-age activities could include:
-shaking sugar, cinnamon or cocoa from a sprinkle-top jar
-inserting toothpicks in melon or pineapple chunks and arranging on a plate
-picking grapes from the stem and putting in a bowl
-pulling the string on the salad spinner to dry greens
-using a melon baller with soft cantalope or small melon
-leveling off the ingredients for you on your measuring cup
-juicing a lemon or orange with a hand juicer
-peeling and grating veggies
-slicing cheese with a cheese slicer
-roll out small balls of pie crust dough, cookie dough, bread dough
-cut wedge shapes with pizza cutter, or pastry cutter
Below are some of the utensils a preschool child should be able to handle at some point. Yes, you do see a small paring knife; but note the child-size gardening gloves adjacent to it. With the gloves on, the child will not get cut using a small knife, especially given that they apply a lighter pressure than an adult when using these tools. I gave my daughter her first knife and gloves when she was three; and as an adult, she still talks of how special her first knife was to her. (She's now a chef)
Engage children in food preparation tasks that are required for making meals from scratch. If they want to make a salad, have them wash the lettuce, peel the carrots, etc; using fresh garden produce (not peeled, cut and prepackaged items) . Use smaller produce that is appropriate for their skills. Have them slicing green onions, versus larger onions; use plum and cherry tomatoes, versus slicing large tomatoes; use thinner and shorter carrots for slicing, peel or grate carrots, versus chopping a carrot.
Most importantly, let children decide what they want to make and how they want it to look like. Let them create and experiment. Do not hover and force a right or wrong way (unless necessary--like if they are using salt when recipe calls for sugar) Children absolutely swell with pride when they can contribute to a meal--"Kalyn's salad tonight"! "Mae fixed dessert for us"!
Think of this; if you child starts at three and learns one thing per week about how to prepare food, use utensils, correct kitchen terms, etc; then by the time they start school, they will know at least 100 kitchen tasks for preparing their own food. Their interest and confidence in food prep will be life-long.
For more posts on Kids In The Kitchen, see list of preserving diary posts under "Kids Kitchen"