Fruit and Vegtable Lab Report

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University of Guelph *

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2700

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Health Science

Date

Apr 3, 2024

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docx

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4

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1 HTM*2700 Winter 2024 UNDERSTANDING FOODS FRUIT and VEGETABLE LABORATORY REPORT 1. Before drying, some fruits such as apples and pears are dipped in an ascorbic acid solution. Name and describe (in detail) the browning reaction that the manufacturer is trying to prevent by using this procedure. Why are these two fruits susceptible to this browning reaction? (10 marks) The browning reaction that the manufacturer is trying to prevent is called enzymatic oxidative browning. The reason these fruits are dipped in the ascorbic acid is that it will disrupt the reaction by lowering the pH below the ideal level of 7.0 which will allow phenol oxidase to function. Since ascorbic acid is an antioxidant, it can stop enzymatic oxidative browning by neutralizing free radicals along with directly inhibiting polyphenol oxidase activity. When fruits are peeled, cut, damaged or bruised they are vulnerable to browning. This is because the cell structure of the outside of the fruit is disrupted when the fruit has been tampered with. When this cell structure has been disrupted, the enzymes are exposed to polyphenol oxidase which causes brown-coloured pigments such as melanin’s to form. These Fruits are susceptible to this browning reaction because they are light in colour, raw or uncooked, and low on acid. Fruit Live Lecture b) Explain the two (2) ways that ascorbic acid prevents browning of the apples and pears. (4 marks) The two ways ascorbic acid prevents browning are through antioxidant activity and the inhibition of enzymatic activity. Browning is unable to occur when the fruits and ascorbic acid come into contact because the ascorbic acid acts as an antioxidant. The antioxidants can prevent intermediate products from being transformed into melanin’s. 2. You want your Applesauce to be very smooth. What ingredient could be added to the recipe? Explain the effect of this ingredient. When should this ingredient be added to the recipe? (5 marks) If I wanted my applesauce to be smoother, I would add an ingredient such as acid. Acid can lower the pH of applesauce as well as inhibit enzymes. The effect of adding acid is that acid will cause the fruit will lose its shape and soften much faster than without adding acid. This happens through the acid being diffused into the cell which will then speed up the rate of the solubilization of protopectin. 3. You add raspberries when you make Apple Crisp (Fruit Lab, Product VII). Explain the effects on the colour of the apples after cooking. (5 marks) When adding raspberries into an apple crisp the colour of the apples will have a darker pink/red colour to them. Since lemon juice, (an acid) is added to the apple crisp, the apples and raspberries will start to lose their shape and soften. This will cause the juice and pigments from the raspberry to bleed onto the apples and make them a different colour. Since apples are pale and colourless on the inside, they can easily take on a much brighter, solid colour. Diffusion also plays a part in this colour change as well. The particles from the higher area of
concentration to a lower area of concentration across the cell membrane to achieve an equilibrium. Fruit Pre Recorded Lecture 4. Describe, with reasons, the recommended method for boiling rutabaga to ensure optimum flavour and odour characteristics (8 marks) The recommended method for cooking rutabaga is to boil it because it is a starchy vegetable with strong flavours and odours. By cooking the rutabaga until it is soft, the taste of starch will be eliminated. When boiling rutabaga, you must use a lot of water to make sure the sulphur compounds are diluted, have the lid off to ensure volatile sulphur compounds can escape and finally only boil the rutabaga for a short period of time to stop more sulphur compounds from producing. Vegetable Pre-Recorded Lecture 5. Zucchini is a vegetable with a high-water content and only takes a few minutes to cook. Explain the effect the tomato juice has on the texture of the zucchini in Zucchini in Tomato Sauce (Plate III, Vegetable Lab) after 15 minutes of cooking. ( 3 marks ) Since Zucchini is a vegetable, it has a high proportion of cellulose and hemicellulose. When zucchini is cooked in water it softens faster because the cellulose and hemicellulose absorb water. Since the tomato juice is acidic it will slow the softening of the cellulose and hemicellulose and make the zucchini still have some firmness. The acidity and heat from the tomato juice also make the chlorophyll in the zucchini turn into pheophytin. Vegetable Pre-Recorded Lecture 6. Explain why someone might want to add baking soda to the water when cooking the Asparagus (Product IV, Vegetable Lab). Why would you not recommend it (7 marks) When cooking asparagus someone might feel like they want to add baking soda to preserve the bright green colour by neutralizing acids in the cooking water. But, by doing this it can soften the texture of the asparagus and make it slimy or mushy. This happens through the pectin in the cell walls breaking down because of the baking soda. The alkaline conditions of the baking soda and water when heated will turn the chlorophyll to chlorophyllin. Vegetable Live Lecture 7. What are the advantages of cooking vegetables in the microwave oven? (4 marks) The advantages of cooking vegetables in the microwave oven are dependent on whether the vegetables are canned, frozen or fresh. Overall, microwaves can cook vegetables much quicker than other methods due to the longer wavelengths that can penetrate the vegetable. Frozen and canned vegetables take a shorter amount of time because they are both precooked beforehand. Microwaves also can preserve the nutrients and retain the texture and colour of the vegetables, by cooking the vegetables quickly without using excessive heat exposure.
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