Biology Research Vitamin C

by lesleyraimondihotmailcouk (student)

GCSE Science

Biology Research – Vitamin C

Fruit and vegetables with the highest amounts of vitamin C

Peppers (red and green)
Guavas
Dark green leafy vegetables, Kale
Kiwi
Broccoli
Berries (strawberries, blackcurrants)
Citrus fruits (oranges and juice)
Tomatoes (cooked)
Peas
Papaya
Peaches

(1, 2)

Testing for vitamin C

Introduction

A blue substance called 2, 6-dichlorophenolindophenol (DCPIP) acts as an indicator. It changes from blue to red/orange with acids but loses its colour in the presence of certain chemicals; one is ascorbic acid (vitamin C). DCPIP solution can be used to test for the presence of vitamin C in food.

Equipment:

Test tubes and rack

Glass rod

Spatula

Pipette

Food samples, juice

DCPIP solution

Method

How different cooking methods affect vitamins in food

A Danish study showed that boiling for just 5 minutes caused 45 to 64 percent of vitamin C to be lost in broccoli. The most vitamins are retained when there is less contact with water and a shorter cooking time. Microwaving and stir-frying reduce vitamin loss because they cook food quickly. Deep frying also reduces vitamins in food; the high heat required for frying destroys heat-sensitive vitamins. (4)

Ascorbic acid, or vitamin C, is an extremely unstable water-soluble vitamin. The vitamin C content of foods can be reduced by exposure to extreme cold, heat, light, lengthy storage and water. All forms of cooking reduce vitamin C levels in foods. However, boiling foods destroys the highest percentage. In a study published in the August 2009 issue of the "Journal of Zhejiang University Science," researchers examined five methods of cooking broccoli. The methods were stir-frying, microwaving, steaming, boiling, and a combination of stir-frying and boiling. The study concluded that after five minutes of cooking broccoli florets, using each method, boiling ...

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Pasteurisation of fruit juice

Pasteurization is the process of treating juice, milk and other foods to kill harmful germs, usually by heating.

Beta-carotene (which is converted into vitamin A by the body) is stable during mild heating, but losses occur at high temperatures. Vitamin C leaches out during cooking because it is water soluble and it is also heat sensitive, so some is destroyed. Water-soluble B vitamins are lost if the cooking water is discarded. Vitamin E is destroyed at high temperature. (6)

The sugars and minerals in juices are typically unchanged by pasteurization and remain present in high concentrations. Pasteurized apple, orange, grape, pomegranate, tomato and carrot juices contain substantial amounts of the minerals potassium, phosphorus and magnesium.

Vitamins are more vulnerable to heat destruction than are sugars and minerals. Pasteurization may cause low-level loss of some of these micronutrients. Fresh-squeezed orange juice contains approximately 124 milligrams of vitamin C per cup; pasteurized orange juice contains approximately 84 milligrams, nearly one-third less. (7)

Dairy products, alcoholic beverages and fruit juices are commonly pasteurized. The pasteurization process typically involves heating beverages up to 180 degrees Fahrenheit in order to kill bacteria, although many fungi and parasites are also destroyed by the heat. Flash pasteurization uses higher temperatures and only needs about 10 seconds to complete, whereas traditional pasteurization needs up to 30 minutes. Before pasteurizing the juice, the majority of inorganic fruit is irradiated with high-frequency gamma rays in order to kill insect larvae, parasites and other pathogens. This method destroys more nutrients than pasteurization. (8)

Bibliography