Combine pineapple chunks (with juice), walnuts, orange juice and ginger. Toss and combine fruit and juices. Add berries and toss well. Divide fruit mixture into 4 equal servings and pack in airtight plastic freezer containers. Freeze. Keep in the freezer and use as an ice pack in your insulated lunch bag. The fruit will partially thaw before lunchtime and remain chilled and tasty.