Investigating the Browning of a Fruit or Vegetable

Aim: To design, carry out and report on an experiment which investigates the browning of red delicious, pink lady, granny smith, braeburn and royal gala apples with regard to temperature and pH levels. Hypothesis: It is expected that each apple will brown at a faster rate at warmer temperatures and at an optimal pH level. The degree and speed at which each apple portion browns will depend upon the strength and amount of the enzyme phenolase present in each portion. Background Information: Apples will turn brown when cut and exposed to air. This can be partly attributed to the action of enzymes which are organic catalysts. They speed up chemical reactions without taking part in the reaction. Enzymes are sensitive to temperature and pH and have optimal levels of each variable at which they will function at the fastest rate.For the browning reaction of an apple to occur, three conditions are necessary; 1. The enzyme know as phenolase must be present 2. The target/substrate of the phenolase called phenols must be present 3. Oxygen must be present in the surrounding atmosphere. Apple browning occurs close to the fruit?s flesh surface. This is because cells beneath the fruit?s skin are damaged and exposed to oxygen. In whole apples, the phenolase and phenols are kept separate. However, when one cuts or bites into any type of apple, the cells are opened and the enzyme and target are free to react with one another. The phenolase proceeds to combine the phenols and oxygen into the different chemical of polyphenol oxidase which is yellow/brown in colour. This type of reaction is an oxidation reaction. The brown colouring of polyphenol oxidase is what is seen on the apple surface. Materials needed: Ø Thermometer Ø Universal indicator Ø 4 small plates Ø Small bowl Ø 10 teaspoons of citric acid Ø Alkaline solution, 1t Jif quarter cup water Ø 6 royal gala apples Ø 6 red delicious apples Ø 6 granny smith apples Ø 6 braeburn apples Ø 6 pink lady apples Ø Apple corer Ø 1 teaspoon Method: 1. Place a thermometer in the freezer with the bulb not touching any frozen items, (this will create a false reading) for 5 minutes. Record the result. 2. Proceed to test the temperatures of the fridge, a kitchen cupboard and on an outdoor table exposed to the full sun. Record the results. 3. Core 3 royal gala apples and slice them into quarters. 4. Sprinkle 1 teaspoon of citric acid on 3 of the apple quarters and 1 teaspoon of Alkaline Jif solution on a different 3 apple quarters. Leave the remaining 4 quarters untouched. 5. Immediately place 1 acidic quarter, 1 alkaline quarter and 1 plain quarter of apple on separate 4 small plates. 6. Place 1 plate in the freezer, 1 plate in the fridge, 1 plate in a cupboard and 1 plate outside with full sun exposure. 7. Check on the apple quarters at 30 seconds, 1 minute, 1 minute 30 seconds, 2 minutes, 3 minutes, 4 minutes, 5 minutes and 8 minutes recording the % of the flesh surface area which has oxidized by each check time. 8. Determine the % of the exposed flesh area oxidized and record in a table. 9. Repeat steps 1-8 for red delicious, granny smith, pink lady and braeburn apples. 10. Repeat steps 1-9 again to verify results. Control: The entire experiment was carried out at the following temperatures which were determined by the same thermometer. Full Sun (FS) = 23C Freezer (fre) = -13C Fridge (fri) = 5C Cupboard (cup) = 20C Also, each apple quarter was placed on the same size plate in the same position in each location. Each quarter had the same amount and brand of citric acid and Jif applied. The time was also recorded using the same stopwatch. Safety precautions: The coring of each apple should be supervised by an adult if the user is inexperienced, as should the cutting of each apple into quarters. This prevents injury to all involved. Also, when sprinkling the 20 apple quarters with citric acid and Jif solution, avoid contact with open cuts and eyes as this will cause an intense sting in the affected area. If this does occur wash out immediately with water and alert an adult Results: Are averages of two tests. Red Delicious % of exposed flesh brown Time FS Fre Fri cup 1 minute Citric acid applied 7 2 3 5 jif soln applied 14 10 20 13 Control 15 10 10 14 2 mins Citric acid applied 10 8 13 18 jif soln applied 38 28 35 36 Control 36 25 28 35 3 mins Citric acid applied 11 9 14 18 jif soln applied 46 33 40 41 Control 44 30 32 45 4 mins Citric acid applied 16 12 15 20 jif soln applied 53 40 44 46 Control 51 34 39 50 5 mins Citric acid applied 20 16 17 23 jif soln applied 61 41 55 56 Control 62 41 43 54 8 mins Citric acid applied 27 18 21 32 jif soln applied 85 75 85 80 Control 82 48 51 72 [image] Pink Lady % of exposed flesh browned Time FS Fre Fri cup 1 minute Citric acid applied 10 0 2 5 jif soln applied 26 2 3 12 Control 35 2 4 14 2 mins Citric acid applied 31 5 7 20 jif soln applied 44 8 20 35 Control 68 20 26 41 3 mins Citric acid applied 50 10 13 28 jif soln applied 61 12 22 41 Control 79 24 29 46 4 mins Citric acid applied 60 15 18 34 jif soln applied 69 17 29 44 Control 84 30 34 61 5 mins Citric acid applied 63 18 30 44 jif soln applied 81 25 33 57 Control 91 34 40 75 8 mins Citric acid applied 67 20 32 52 jif soln applied 88 38 42 65 Control 95 40 44 82 [image] Royal Gala% of exposed flesh browned Time FS Fre Fri Cup 1 minute Citric acid applied 2 0 0 1 jif soln applied 10 1 4 8 Control 4 0 2 3 2 mins Citric acid applied 10 1 4 6 jif soln applied 27 8 16 21 Control 20 3 12 15 3 mins Citric acid applied 15 3 7 11 jif soln applied 39 20 24 32 Control 30 6 15 25 4 mins Citric acid applied 30 5 10 16 jif soln applied 54 30 38 44 Control 50 8 31 40 5 mins Citric acid applied 33 7 13 18 jif soln applied 71 42 55 63 Control 57 10 35 51 8 mins Citric acid applied 36 9 17 22 jif soln applied 85 64 73 79 Control 65 14 40 60 [image] Braeburn% of exposed flesh browned Time FS Fre Fri cup 1 minute Citric acid applied 22 0 0 6 jif soln applied 29 0 1 8 Control 40 0 3 17 2 mins Citric acid applied 46 4 6 22 jif soln applied 51 7 10 25 Control 55 13 16 34 3 mins Citric acid applied 57 6 8 30 jif soln applied 62 11 16 34 Control 72 19 23 44 4 mins Citric acid applied 63 15 11 38 jif soln applied 69 24 32 43 Control 76 37 40 54 5 mins Citric acid applied 74 20 14 42 jif soln applied 77 29 35 52 Control 84 40 44 64 8 mins Citric acid applied 88 30 30 51 jif soln applied 92 42 56 69 Control 94 65 72 76 [image] Granny Smith % of exposed flesh browned Time FS Fre Fri cup 1 minute Citric acid applied 4 0 0 1 jif soln applied 2 0 0 0 Control 8 2 3 6 2 mins Citric acid applied 6 0 1 3 jif soln applied 9 2 4 5 Control 15 5 8 11 3 mins Citric acid applied 11 2 4 6 jif soln applied 17 8 14 15 Control 24 6 10 18 4 mins Citric acid applied 17 2 6 10 jif soln applied 31 10 24 28 Control 34 8 15 29 5 mins Citric acid applied 21 3 7 11 jif soln applied 44 20 30 38 Control 56 12 25 51 8 mins Citric acid applied 26 5 9 16 jif soln applied 58 35 38 71 Control 67 17 45 60 [image] [image][image]Variables: Independent Variables: Amount of citric acid Amount of Jif solution Temperature of environment around apple Type of apple Dependant Variable: Time taken for apple quarter to oxidize i.e. Turn brown. Conclusion: It is clear from the above tables and graphs, apples oxidize at different rates to one another due to the amount of phenolase and phenol present in each individual type of apple. pH level Apple browned most Sun (23Ù?C) in: Freezer (-15 Ù?C) Fridge (5 Ù?C) Cupboard (20 Ù?C) Citric (2) Braeburn (88%) Braeburn (30%) Pink Lady (32%) Pink Lady (52%) Alkaline (12) Braeburn (92%) Red Delicious (75%) Red Delicious (85%) Red Delicious (80%) Control Pink Lady (95%) Braeburn (65%) Braeburn (72%) Pink Lady (82%) pH level Apple browned least Sun (23Ù?C) in: Freezer (-15 Ù?C) Fridge (5 Ù?C) Cupboard (20 Ù?C) Citric (2) Granny Smith (26%) Granny Smith (5%) Granny Smith (9%) Granny Smith (16%) Alkaline (12) Granny Smith (58%) Granny Smith (35%) Granny Smith (38%) Pink Lady (65%) Control Royal Gala (65%) Royal Gala (14%) Royal Gala (40%) Granny Smith and Royal Gala (60%) The experiment thus investigates the browning of red delicious, pink lady, granny smith, braeburn and royal gala apples with regard to temperature and pH levels. The original hypothesis was correct as all apples browned at a faster rate as the temperature increased and at a lower rate as the pH decreased. As each apple browned at a slightly different rate in each of the environments, we can conclude each must contain different amounts of the enzyme phenolase and substrate phenols which react to form polyphenol oxidase. Sources of error: Possible sources of error include; v Due to the ambiguity of how brown the flesh surface area of the apple quarter was, it was difficult to obtain an exact reading. v The opening of the fridge, freezer and cupboard may provide sources of error as these actions would alter the initial temperature or the specific environment changing the rate of browning of the apple quarter. v The bruising of any apples would make parts of the flesh brown at a faster rate than unbruised areas as the phenolase and phenols would have already reacted making the brown polyphenol oxidase. v How ripe each apple was would affect the amount of the enzyme and substrate thus affecting the reaction rate and % of exposed flesh browned. Possible improvements: The above experiment could be improved in the following ways: v More accurate method of determining % of apple flesh oxidized. v A wider variety of apples could be used rather than a mere 5. v Altering of environment temperatures e.g. opening of freezer and fridge doors, could be eliminated. v A natural alkaline substance could be used rather than the chemically enhanced cleaning product of jif. This would produce clearer results as the rate of reaction differed greatly between apple types when the Jif solution was applied. v Cary experiment out more than twice to get more accurate results Applications to contemporary society: Chefs and cut produce sellers around the world should treat their various types of apples with fruit juice from lemons, grapefruit, limes or other citrus fruits if they wish them to have flesh exposed to air but not brown. Covering with and acidic substance can delay the browning process by preventing the oxygen from reacting with phenolic compounds leading to the colour changes. But would this affect flavour? More research needs to be done in contemporary society to test the best methods of apple preservation which impacts least on the apple flavour. Possible future directions and investigations: The non- browning apple is a possibility being investigated by scientists worldwide. Benefits of the non browning apple: Used in the production of ready to eat apple slices making the fruit more appetizing to people around the world, particularly younger generations, increasing health of millions. Grower Impact: Reduced levels of cullage due to superficial harvest bruising meaning larger harvests and increased profits. Processor Impact: Less product shrinkage due to bruising on packing line. If apple is fresh cut, less flavour altering additives needed to control browning process. Retail Sector Impact: As bruising won?t show as much, product cullage will be significantly reduced to about 4% of total produce rather than the current rate of 10%. Consumer Impact: Gain access to apples that don?t require additives to control browning. Better health due to the more appetizing thought of non browning apples

Investigating the Browning of a Fruit or Vegetable 8.1 of 10 on the basis of 4292 Review.