The weather outside is making me think about freezing! Most foods can be frozen with a few exceptions like mayonnaise or shelled eggs. Freezing is so common we think we know all about it. Today, I’m going to focus on the science along with some facts, fiction, and tips.
The Science: Freezing at 0 degrees F (-18C) does two things: It halts the growth of bacteria, yeasts, and molds. This is known as microbial stasis. Freezing also retards the enzymatic processes that are responsible for reducing quality. As foods freeze, crystals are formed. When freezing occurs quickly, the crystals are small but when freezing is slow the crystals are larger and can puncture the membranes of food causing a mushy texture. When ice crystals evaporate on the surface of foods, evaporation happens (sublimation). This is what we know as “freezer burn”.
Optimal freezing Conditions:
Freezer temperature at zero F
Freeze as quickly as possible which means cooling food first, putting food in smaller, flatter containers or freezer bags
FIFO: Label and date all frozen foods and follow the “first in, first out” rule
Use food-grade freezer bags, butcher paper, freezer containers, Mason jars or silicone molds as well as vacuum sealing. The right containers will maintain quality and safety.
Optimal Thawing Conditions
Best option is to thaw in the refrigerator. The rule of thumb is one day for every 5 lbs of food. So, a 15 lb turkey will take about 3 days to thaw in the fridge.
Thawing food under cool running water or in the microwave are acceptable if the food is cooked immediately after thawing.
Never thaw frozen foods at room temperature (no counters, garages, decks). As freezing does not kill microbes, when thawing occurs bacteria begin to multiply. If food enters the temperature danger zone of 40-140 degrees F, microbes replicate at an astounding rate which is unsafe.
Always slash holes into vacuum sealed frozen foods during the thawing period. While vacuum sealing preserves the quality of food during freezing, it also creates an anerobic environment (no oxygen) which is the environment that is needed by some of the worst pathogenic bacteria. So, give vacuum sealed frozen foods some air during thawing.
Facts & Fiction
Freezing Kills Bacteria: False. It halts the growth but does not kill bacteria and other microbes.
Frozen Food Lasts Forever: False. Well, technically it will but the quality diminishes over time. Soups, left-overs, prepared foods should be used in 3 months. Raw meats, poultry etc. are generally good for up to 12 months. Always label and date frozen foods.
Frozen Vegetables and Fruit are Less Nutritious: False! When fruits and vegetables are blanched and frozen at their peak (including commercially frozen foods), they are more nutritious than those we buy fresh in the grocery store.
You Can’t Refreeze Frozen Foods: False! It is possible to refreeze frozen food if it has been thawed in the fridge for no more than 3 days. This includes meat, fish, poultry, fruit, and vegetables.
Foods expand during freezing: True! Always leave at least 1 inch of headspace to allow for expansion.
Exposure to air causes crystallization: True! Keep air out during freezing. Press air out of freezer bags, double wrap meats, if using plastic containers, leave headspace but scrunch parchment paper or wax paper and place on top of liquid beneath the lid thus reducing air and crystal formation.
I am a big fan of freezing. I always have lasagnas, pot pies, meatballs, meatloaf, chard, or spinach in bechamel sauce, pesto, ice cream, lemon or lime curd, egg whites for a pavlova, and meats, fish, and poultry at my fingertips. An impromptu meal with friends or a quick supper, something is always available in the freezer. Just one of the many food preservation methods at our disposal.
preservingwithmartha@gmail.com
www.thevalleypreservery.ca
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