Thank you for contacting eXtension with your food preservation question. The Ohio State University fact sheet, Freezing Vegetables, available at http://ohioline.osu.edu/hyg-fact/5000/pdf/5333.pdf provides this information:
"Freezing foods retards the growth of the microorganisms and slows down chemical changes that may cause food to spoil. While freezing slows down spoilage, when the food is thawed the growth of bacteria, yeasts, or mold will continue. Proper handling of vegetables is important before freezing....Blanching vegetables to inactivate the enzymes that change the flavor or color and nutrients is important. Blanching helps to destroy microorganisms on the surface of the vegetable. Blanching also makes vegetables like broccoli or spinach be more compact and take less room in the freezer."
This fact sheet also provides recommended blanching times and techniques.