TESTING THE EFFECT RIPENING HAS ON THE ph OF APPLES, LEMONS, AND ORANGES

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1 TESTING THE EFFECT RIPENING HAS ON THE ph OF APPLES, LEMONS, AND ORANGES Sheridan Page Cary Academy ABSTRACT The experiment was performed to determine if the ripeness of fruit affected its ph level and smell intensity. It was hypothesized that the ripeness of the fruit would result in a higher ph level. The experiment was performed by squeezing out the oranges and lemons and taking a core sample of apples and allowing the juice to drain into a plastic tub, and measuring the juice with a ph probe. The smell intensity was determined by smelling of ammonia and using that as a smell intensity of 10. Then, each fruit was smelled each week. The results of the experiment were: the smell intensity of fruit increases with ripening, but the ph of fruit fluctuates randomly as the fruit ripens. As an example, the smell intensity of an apple on a scale of one to ten was: 1 when the apple was new, 2 when the apple had 1 week to ripen, and 3 when it had 2 weeks to ripen. The apple s ph was 3.9 when the apple was new, 3.8 when the apple had 1 week to ripen, and 4 when it had 2 weeks to ripen. INTRODUCTION The experiment was conducted to determine what effect ripening had on fruit. Fruit was tested to see if ripening had any effect on the ph. Inside fruits, there are polymers and there is sugar inside these polymers. There are also acids inside the fruit. In order for the sugar to be released, the polymer needs to be broken down and the acids neutralized. Fruits ripen because they produce enzymes (catalysts) that break down the sugar polymers and neutralize the acids. The ripening process is started when the fruit produces an odorless gas called ethylene that begins the production of enzymes.

2 An acid is any substance that increases in hydronium ions when it is dissolved into water. A base is any substance that increases in hydroxide ions when dissolved in water. When an acid and base are mixed, they react in a neutralization reaction. The hydrogen and hydroxide ions react to form water. The other ions from the acid and base dissolve into the water. If the water is removed, a salt is created. Wet and cold weather at the time of blooming will stop pollenating insects from pollinating the fruit bloom, and this will delay ripening. Wet weather will also affect openpollenated crops that rely on dry winds to spread pollen. Some crops bloom again weeks later, causing the production of fruit to be delayed even further. The soil that the plant is grown in affects the ripening time as well. Soil with lots of organic matter affects plans by improving drainage and allowing the plant to take in more nutrients. The ph level of the soil affects growth rate as well. Many fruits and vegetables grow best with a soil ph of 6.0 to 6.5. Planting time affects growth rate of vegetables and fruit. If warm season crops, like melons, are planted in cold weather, then they will not grow as well as they would if they had been planted during warm weather, and vice versa for cold season crops such as onions. The climate will affect bearing of fruit and fruit ripening. Cold climates will bear fruits and ripen fruits later than warm climates. Fruit trees planted in the North will bear fruit and ripen after fruit trees planted in the South. If a fruit tree lacks certain nutrients, it will not grow as well. For good plant growth, a plant must have its necessary nutrients in the soil around it. For example, a lack of phosphorus will slow down or stop blooming and the bearing of fruit. The cultivar, or type, of fruits and vegetables, will affect its growth time. If one cultivar will bear fruit in 65 days and another will bear fruit in 85 days, then the cultivar with the date of maturity that falls in its growth season will grow faster than the other. Because there were multiple pieces of fruit to be tested, one of each fruit was chosen to be the representative fruit. The representative apple has a mass of grams. The

3 orange had a mass of grams and the lemon had a mass of grams. The apple is dark red with light red spots. It has a stem coming out of the top. Around the bottom of the stem, the apple is green. The apple is wider at the top and slimmer at the bottom. It is dotted with small white spots, and has a diameter of 79 mm. The orange has a diameter of 6.5 mm. It is bright orange, and is slightly rough due to small indentations on its surface. The lemon has a diameter of 6.0 cm and is 8.0 cm long. The lemon is slightly rough and has two small "humps" on each end of the lemon. The lemon had a ph of 4.7. The orange had a ph of 3.1and the apple had a ph of 3.9. It was then hypothesized that riper fruit would have a higher ph than unripe fruit because there are acids in the fruit before it is ripe, and they are neutralized during ripening, thus making the fruit less acidic. MATERIALS AND METHOD ph pen 5 apples, 5 lemons, 5 oranges 100 ml beaker Apple Corer Ammonia Small Ziploc plastic tub The experiment was conducted by allowing the fruit to ripen and then collecting a juice sample. To test the ph of the lemons, a wedge was cut out and squeezed into a beaker. To test the ph of the oranges, a slice was cut out and squeezed into a beaker. To test the ph of the apples, the apple corer was stuck into the side of an apple and the juice was collected. The ph pen was dipped into the liquid. Once each week, one of each fruit was ph tested and the data recorded. The intensity of the smell of the fruit was also tracked using a scale of The smell of ammonia was used as a control, and was considered to have a smell strength of 10.

4 ph One of each fruit was then smelled and its intensity relative to the ammonia was recorded. The control of the experiment was unripe fruit. The independent variable, or the aspect of the experiment that was being manipulated, was the ripeness of fruit. The dependent variable, the aspect of the experiment that was being measured, was the ph of the fruit. The controls are the amount of time the fruit was allowed to ripen between measurements, the location the fruit was kept the same during the experiment, and the source of the fruit was the same. RESULTS AND DISCUSSION New Fruit ph 1 Week (ph) 2 Weeks (ph) Age of Fruit Apple Orange Lemon Figure 1: ph of 3 Types of Fruit Over Time

5 Smell Intensity Apple Orange Lemon 1 0 New Fruit (Smell Intensity) 1 Week (Smell Intensity) 2 Weeks (Smell Intensity) Age of Fruit Figure 2: Smell Intensity of 3 Types of Fruit Over Time The maximum ph (least acidic) of an apple was 4.0. The minimum ph (or most acidic reading) of an apple was 3.8. The strongest smell of an apple on a scale of 1-10 was a 3, and the weakest smell of an apple was 1. The maximum ph of an orange was a 3.9, and an orange s minimum ph was 3.1. An oranges highest smell intensity was a 6, and its lowest smell intensity was a 2. The maximum ph of a lemon was a 4.7, and the minimum ph of a lemon was 2.2. The maximum smell intensity of a lemon was 4, and its minimum smell intensity was a 2. During the experiment, seeds came out of the lemon when it was juiced. No pulp came out of the orange. Small bits of the apple came out when it was juiced. During the experiment, some of the fruit developed trace amounts of mold as time passed, but one lemon was covered completely with mold at the end of the experiment. CONCLUSIONS The hypothesis was neither confirmed nor denied because the ph of the fruit seems to fluctuate randomly. The orange seemed to change in ph level extremely randomly: when it was new, it had a ph of 3.1, when it had ripened for one week it had a ph of 3.9,

6 and when it had ripened for two weeks it had a ph of 3.4. Notice that none of the fruit had a ph greater than seven and therefore all ph readings were acidic. The experiment could have turned out the way it did because the fruit may not have been from the same farm, and may not have been harvested at the same time. Also, the fruit could have had a chemical applied to it to keep it from ripening. The experiment could be improved by storing the fruit separately, and in the open air. It could also be improved by running the juice through a very fine strainer so solid parts of the fruit could not be measured. The beakers could have been dried after thoroughly rinsing them to prevent water from affecting the results of the experiment. The fruit could have been tested at a higher frequency (such as every three days). A future experiment could be to find how sugar affects the ph of different liquids. This would help determine if sugars being released into the fruit from the ripening process could have affected the experiment. REFERENCES Batt, Carl. "Archives of Ask A Scientist! Glucose Sweetens Fruits as it Ripens." Cornell Center for Materials Research. CCMR. 29 Sept Web. 27 Jan Borgford, Christie and Sally Ann Vonderbrink. "Acids and Bases." Interactions of Matter. Austin: Holt, Rinehart, and Winston, Print. Kendrick, Mandy. "The Origin of Fruit Ripening." Scientific American. Scientific American. 17 Aug Web. 27Jan Richford, Nanette. "Conditions That Affect the Speed at Which Fruits and Vegetables Ripen." Gardenguides. Demand Media Web. 27 Jan Tree Fruit Research & Extension Center. "Ethylene: The Ripening Hormone." Postharvest Information Network. Washington State University. 29 Oct Web. 27 Jan

7 Wikipedia. "ph." Wikipedia. Wikimedia Foundation, Inc. 26 Jan Web. 27 Jan