Foods and Nutrition 12: Food Preservation Name

Foods and Nutrition 12: Food Preservation Name:

Fresh * Frozen* Freeze Dried *Individaully Quick Frozen* Smoked *Dehydrated* Salted* Canned* Sugar

As a class, discuss the questions and fill in the answers.

1. Why does food deteriorate over time?

1. List the 6 methods of food preservation that were used by ancient people, and still used today.

1. In the days before refrigeration, how was fresh meat preserved?

1. Microbes are very sensitive to ______.

1. Which foods are microbes used to produce?

1. How can the temperature of food be brought above boiling temperature?

1. Most food preservation methods remove ______from the food.

1. When we refrigerate food, what happens to the microbes?

Complete the chart by filling in the last column. Also, highlight any nutrient losses/health concerns that occur due to the food preservation method.

Method / Advantages / Disadvantages / Food and Equipment Example
Drying (e.g. freeze-drying, spray-drying, sun-drying, oven drying, food dehydrator) / Produces concentrated form of food.
Inhibits microbial growth & autolytic enzymes.
Retains most nutrients. / Can cause loss of some nutrients, particularly thiamin & vitamin C.
Sulphur dioxide is sometimes added to dried fruits to retain vitamin C, but some individuals are sensitive to this substance. / Food examples:
Equipment:
Smoking / Preserve partly by drying, partly by incorporation of substances from smoke and/or chemical nitrates/nitrites , which are used to preserve the pink colour. / Eating a lot of smoked foods has been linked with some cancers in some parts of the world – the evidence is not conclusive whether the carcinogen is the smoke, or the nitrates, or some other factor. / Food examples:
Equipment:
Refrigeration / Slows microbial multiplication.
Slows autolysis by enzymes / Slow loss of some nutrients with time / Food examples:
Equipment:
Freezing / Prevents microbial growth by low temperature & unavailability of water.
Generally good retention of nutrients. / Blanching of vegetables prior to freezing causes loss of some B-Group vitamins and vitamin C.
Unintended thawing due to variations in the freezer temperature can reduce product quality = foods can get freezer burn, deteriorate in quality / Food examples:
Equipment:
Adding salt or sugar / Makes water unavailable for microbial growth.
Process does not destroy nutrients. / Increases salt and sugar content of food. / Food examples:
High heat processing (e.g. pasteurisation) / Inactivates autolytic enzymes
Destroys microorganisms. / Loss of heat-sensitive nutrients. / Food Examples:
Canning (involves high heat processing) / Destroys microorganisms & autolytic enzymes. / Water-soluble nutrients can be lost into liquid in can. / Food Examples:
Equipment:
Chemical preservatives / Prevent microbial growth
No loss of nutrient. / Some people are sensitive to some chemical preservatives. / See question C
Ionizing radiation / Sterilizes foods (such as spices) whose flavour would change with heating.
Inhibits sprouting potatoes
Extends shelf life of strawberries and mushrooms / Longer shelf life of fresh foods can lead to greater nutrient losses than if eaten sooner after harvesting. / Food Examples:

A.) Chemical Preservatives

Look at the food items in the pantry in the classroom and at home. Can you find ingredients that are chemical preservatives? Use the additive handouts to discover the function of the ingredient, and its safety status.

Food item / Chemical preservative / Function of the preservative / Safety status

Look at the “Additives to Avoid” – List ten types of foods that are most likely to contain these most concerning food additives.

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Stability of nutrients in food: Vitamins can be altered during processing conditions such as exposure to high heat, air, light, water. Once altered, it won’t be able to serve its function in the body. Highlight the vitamins and the conditions under which the vitamins can be damaged.

Nutrient / Stability Characteristics
Vitamin A / Quite stable during processing and cooking
Vitamin D / Very stable to heat but sensitive to exposure to air and light.
Vitamin E / Relatively stable except at deep frying temperatures
Vitamin K / Stable in cooking but sensitive to light.
Thiamin / Quite unstable to heat and alkaline conditions. Lost during refining of cereals. Dissolves in cooking water.
Riboflavin / Very sensitive to light: 50% lost from milk left in sun for 2 hours.
Relatively stable to most home cooking methods (unless bicarbonate of soda added).
Niacin / Stable to most processing but leaches into cooking water.
Vitamin B-6 / Moderate retention during most processing.
Vitamin B-12 / Moderate retention, but losses occur when heated under acid and alkaline conditions.
Folic acid / Large losses can occur during cooking. Presence of copper aids
destruction.
Pantothenic acid / Relatively stable during most home processing.
Biotin / Good retention during most home processing.
Vitamin C / Unstable. Losses occur from exposure to air, light, heat and copper. Also dissolves in cooking water.

1.)  Milk is pasteurized and then typically packaged in opaque (not clear) containers. Why? (2)

2.)  Why is fresh food “healthier” than processed, preserved food? (2)

3.)  Why does our food supply and typical eating habits rely on processed and preserved foods when they aren’t the most nutritious choice? (4)

Read the article Food That Lasts Forever and answer the following questions.

4.)  How does the article propose that food preservation techniques will change the way we shop for and use food?

5.)  Describe the “indestructible sandwich”. Why was this item developed?

6.)  What is the life expectancy of a can of SPAM compared with its actual expiration date? Why is there such a large difference between these numbers?

7.)  How is the old method of sterilization different from the new HPP (high pressure processing)? What benefits are there for the consumer?

8.)  In what situations are processed, shelf stable (no refrigeration required) foods especially important?

9.)  According to the food science expert quoted in the article, how much food is lost to rot and decay in the world? (2)

Reasons to Preserve Food:

Canning Notes and Diagram