Instructions:

1. Ask students if they've ever eaten strawberries in January or peppers in November. Explain that because of food processing, foods that used to be out of season during much of the year are now available and affordable all year long.
2. Explain that in much of the United States, tomatoes are harvested only in the summer. However tomatoes are sold year-round.
3. Ask students: If tomatoes grow in the summer months, how are we able to buy them year-round at the grocery store? For the rest of the year, they are grown in greenhouses so that the climate (weather) is controlled or they are grown in warmer climates and shipped to the United States.
4. Point out that another way to enjoy tomatoes year-round is by eating products made from processed tomatoes. 
5. Ask students: What are some products that are made using processed tomatoes? Likely answers include pizza sauce, pasta sauce, sun-dried tomatoes, salsa, ketchup, diced tomatoes, tomato paste, tomato soup, tomato juice, etc.
6. Grapes are another example of a food that has several products made from it. Ask students: What are some foods that are made from grapes? Raisins, grape juice, vinegar, jam, jellies, and marmalade are some examples.
7. Tell the class that they are going to do an activity focusing on how raisins are made using a type of food processing called dehydration or drying. Ask students: How do you think raisins are made from grapes? By drying the grapes. What are the pros and cons of buying raisins versus fresh grapes? Raisins have a longer shelf life and are readily available year round. Grapes may be more expensive during the off season and go bad after a few days. The taste and texture of each is different.

Activity: Make raisins

Follow the steps below to make your own raisins:

1. Wash the grapes and spread them onto the cookie sheet. Make sure the grapes are not touching one another.
2. Find a sunny spot outdoors where you can place your grapes to dehydrate. (For example, place them on a table in a courtyard and label them so no one will disturb them.) Make sure they are safe from animals. Put the towel over the grapes to protect them from pests.
3. Turn the grapes from side to side twice a day to keep them from sticking.
4. In 3-7 days, the grapes will change into raisins.

Note: Environmental factors such as direct sunlight, the type of surface under the grapes, and humidity can affect how long the process will take. For areas that experience high humidity levels, you may wish to dry your grapes in a dehydrator or oven. Set your oven for 160° F  and leave the grapes to dry for up to 7 hours. Check the progress each hour and turn the grapes frequently to avoid sticking.