AY Honors/Food - Freezing/Answer Key

1. Define the following terms:

a. Blanching: Blanching is a food preparation process wherein the food substance, usually a vegetable or fruit, is plunged into boiling water, removed after a brief, timed interval and finally plunged into iced water or placed under cold running water (shocked) to halt the cooking process.

b. Quick freeze: Quick freezing is used to quickly freeze perishable food items. In this case, water contained inside the food items is subjected to temperatures well below its melting/freezing point {{inits|0°C|32°F). This causes the water inside the foods to freeze in a very short period of time.

c. Freezer burn: Freezer burn is a condition that occurs when frozen food has been damaged by ice crystals, due to air reaching the food. It is generally caused by non-airtight packaging. Freezer burn often results in change of texture and discoloration of the affected food. It appears as grayish to brown leathery spots on the food. Although freezer burn affects the quality of food, it does not make it unsafe or unhealthful to eat.

2. What kinds of containers can be used for freezing foods?

Plastic containers work the best. Metal containers also work well. The important considerations are that the container be food-safe, air-tight, and not be damaged by freezing.

3. What are the essential things to be considered when selecting vegetables or fruits for freezing?

First check the quality as you would for any fresh fruit or vegetable. Wash thoroughly and make sure the fruit or vegetable has no salt on it. When you freeze the fruit or vegetable make sure that is is not bumped or otherwise damaged.

4. How do you thaw frozen vegetables for the table? How do you thaw frozen fruits for the table?

Vegetables

Most vegetables should be cooked without thawing first. Corn on the cob should be partially thawed before cooking, and leafy green vegetables should be completely thawed. Thawing should not be done at room temperature. Food is safe indefinitely while it is frozen, but as soon as the temperature rises above 4°C, it is susceptible to bacteria (which can cause food poisoning). Instead, thaw it in the refrigerator 6-8 hours ahead of time, or under cold (below 21°C) running water for 30 minutes. Do not remove the vegetables from their packaging, as this allows bacteria to get in. Turn the package every few minutes.

Drop frozen vegetables in boiling water, and quickly return the water to a boil. Pry the vegetables apart as it thaws so that it can cook evenly.

Fruits

Do not thaw fruit at room temperature, for the same reasons you do not thaw vegetables at room temperature. Instead, thaw fruit in the refrigerator 6-8 hours ahead of time. If you are in a hurry, you can also thaw fruit by running cold water over it, as long as the water temperature is below 21°C, turning the package every few minutes or so. This will take about half an hour for one pound of fruit. If you are going to use the fruit right away, you can thaw it in a microwave oven at a low setting. Do not thaw the fruit completely, as the ice crystals will give it a bit of firmness that freezing takes away.

5. Freeze two vegetables (corn and another of your choice), then prepare and serve for sampling.

Vegetables must be blanched before they are frozen. To blanch, drop the vegetable in boiling water for the "blanching time", then transfer to cold water.

Corn

For corn on the cob, blanch for seven minutes. For kernel corn, blanch for four minutes. Allow it to cool completely. For kernel corn, cut it from the cob leaving one third of the kernel on the cob. Package in freezer bags and place it in a freezer.

Carrots

Cut off the tops and wash. Freeze small carrots whole, but cut large carrots into thin slices or into 1.5cm cubes. Blanch small whole carrots for 5 minutes, and blanch sliced or cubed carrots for 2 minutes. Drain and package into freezer bags, then freeze.

Okra

Blanch small pods for 3 minutes, large pods for 4. Slice into "coins", package, and freeze.

Pumpkin

Cook in boiling water until the pulp is soft. Remove the rind and mash the pulp. To cool, place the container of pumpkin pulp in cold water. Package and freeze.

Summer Squash

Winter Squash

6. Quick freeze a vegetable for easy pouring.

7. Why is salt not put in vegetables to be frozen?

Salt lowers the freezing point of water from its normal temperature of 0°C to -21°C. Most food freezers operate at -18°C, which is higher than the freezing point of salt water. If food to be frozen contains enough salt, it will not freeze in a regular freezer. If it contains only a little salt, the freezing point will be lowered, but not by as much. Even a small amount of salt will prevent it from quick-freezing.

8. Freeze some peaches in light syrup and also some in orange or pineapple juice. What is the reason for using ascorbic acid in the syrup and not in the fruit juice? Why is ascorbic acid used in freezing peaches?