Perhaps nothing can ruin baking plans -- and appetites -- quite as much as opening a bag of baking flour to find an infestation of grain weevils, pantry moths, grain beetles, ants or mealybugs that are commonly found in flour, meals, cereal and processed grain foods. In many cases, an insect lays an egg inside a grain and they hatch inside the bag after a few months. After hatching, they make their way to any other grain product in your pantry. The keys to protecting your cake flour are preventing eggs from hatching and blocking access to the flour.
Discard all infested grain products in your pantry immediately. Open each bag or box and inspect it carefully for signs of bugs. Take the garbage bag outdoors immediately after discarding the grain products.
Clean the pantry or cabinet shelves thoroughly. Vacuum all shelves and any small crevices within the pantry or cabinet, including neighboring cabinets if there are signs of infestation. Wipe everything down with white vinegar. In addition to cleaning the pantry at the sign of infestation, you should clean it thoroughly at least once every few months, particularly to remove any grain crumbs that could feed the bugs.
Place the cake flour bag inside an airtight plastic, glass or metal storage container, using a container large enough to fit the entire bag inside if possible. Many bugs can chew through paper and cardboard packaging typically used for cake flour, and some can even chew through plastic food storage bags, so hard plastic, glass and metal are the best options.
Store the container of cake flour in your freezer for at least a week to kill any eggs that might be present inside the bag. If desired, you can simply keep the flour in the freezer or refrigerator, because bugs don't like cold temperatures.
Fill small, breathable bags with whole black peppercorns and place them in several places within the pantry or storage cabinet. You can use mesh fabric, nylon stockings or even an old T-shirt cut into small pieces to make satchets for the pepper. Additionally, bay leaves placed throughout the pantry can ward off bugs.