Revision 1

White bread (store-bought, with preservatives) Whole wheat bread (store-bought, with preservatives) Homemade white bread (no preservatives) Resealable plastic bags Water spray bottle Magnifying glass Ruler

1. Cut one slice from each bread type into equal-sized pieces (5cm × 5cm). 2. Lightly mist each piece with 3 sprays of water. 3. Place each piece in a separate sealed plastic bag. 4. Store all bags in the same dark cabinet at room temperature (~22°C). 5. Observe daily for 14 days without opening the bags. 6. Record the date of first visible mold, color of mold, and estimated coverage area.

Homemade bread: first mold visible day 3, covered ~60% by day 7, ~95% by day 14. Multiple colors (white, green, black). Store-bought white: first mold day 7, ~15% by day 10, ~40% by day 14. Primarily green mold. Store-bought whole wheat: first mold day 6, ~25% by day 10, ~55% by day 14. Green and white mold. Homemade bread developed a noticeable smell by day 5 even through the sealed bag.

Preservatives clearly extend shelf life. The homemade bread's rapid mold growth demonstrates why preservatives exist in commercial baking. Calcium propionate is the typical preservative in store-bought bread. Good tie-in to food science and chemistry of preservation.