Fruit and Vegetable Report

INTRODUCTORY FOODS

FRUIT and VEGETABLE LABORATORY REPORT

1. a) The chef wishes to garnish a platter of stuffed pork tenderloin with pink apple wedges. Using the Apple Compote recipe (Product III, Fruit Lab) he adds red, cinnamon-flavoured candies to the sugar syrup in which the apple wedges are cooked.

Explain why the apples become pink in colour.

Apple cooks in the sugar syrup (hypertonic solution). Red pigments in candies is water-soluble. Those red pigments are attached to the sugar. Diffusion occurs in a hypertonic solution. Red sugar moves into apples; water in the cell sap moves out of apples. In addition, the water dilutes the red colour, and it becomes pink.

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b) Explain why the apple slices will be more translucent (clear) in appearance after cooking.

Intercellular space contains pectic substances and oxygen. Oxygen gives raw fruits opaque appearance. Some oxygen in apple cell is replaced by water after cooking it in a medium. Refractive index is closer to a value of 1, and water in intercellular space means translucent.

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c) Explain why the apple slices in this recipe maintain their shape.

Candies and sugar syrup both contain high amount of sugar. High concentrations of sugar slow down the tenderization process by interfering with the solubilizaiton of protopectin. Besides, Sugar in the cooking medium slows down protopectin solubilization because it forms hydrogens bonds with protopectin. Therefore, fruit retains its shape longer.

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2. Explain the colour change that occurs to the broccoli in the Garden Vegetable Stir-Fry (Plate I, Vegetable Lab) during cooking.

Chlorophylls are responsible for the green colour in broccoli before cooking in the vegetable oil. However, chlorophyll pigments are fat soluble because they contain a phytol group which, if removed, results in the molecule becoming water soluble. Its colour changes green to bright green. Steaming the broccoli for 2 minutes and adding white vinegar causes it to produces pheophytin (drab olive green). Then, adding soy sauce results in phytol and Methyl groups removed, forming water soluble chlorophyllin (vivid green).

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3. a) Explain the effect on the colour of the red cabbage if you use a cast iron frying pan to prepare the Braised Red Cabbage recipe (Plate VII, Vegetable Lab).

Iron frying pan contains Fe form complexes, which is able to react with Anthocyanins contained in red cabbage. Green coloured complexes will be formed between the pigment and the metal ion, and there will be a green colour left on the pan. In this recipe, adding the vinegar (acid condition) will cause its colour that changes purple to purple-red. Besides, acid will react with iron metal.

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