Title: The effect of temperature on enzymatic browning and how to treat them on fruits, such as, pears, banana and apple.

Transcription

1 Sarah Sutantyo November 27, 2007 Final Individual Project Title: The effect of temperature on enzymatic browning and how to treat them on fruits, such as, pears, banana and apple. Hypothesis and objective: Null hypothesis: the temperature on the fruit juices will not have an effect on enzymatic browning. The independent variable will be the different temperatures three fruits and they are bananas, apples, and pears. The dependent variable will be measured are the difference of the color, the wavelength and the viscosity of the fruit juices. The objective of this experiment is to evaluate the effect of temperature on enzymatic browning reaction by measuring the wavelength and viscosity, to observe the enzymatic discoloration of the fruits and to treat such enzymatic browning with various treatments, such as, lemon juice (acid), sugar syrup, and sulfur dioxide. Background: Appearance, significantly color, is one of the first characteristics used by consumer in analyzing food quality. Enzymatic browning is one of the crucial color reactions that affect vegetables, fruits, and seafood. It is caused by oxidation of pigment in the foods. Enzymatic browning is a chemical reaction catalyzed by the enzyme, polyphenol oxidase that creates melanins. The melanin is the result of the brown color in the foods, in which also affect the nutritional value and flavor of the foods. According to Lee Whitaker, forty percent losses of fruits and vegetables are caused by enzymatic browning. Such loss affects the economic side for many agriculturist and Food Company. Polyphenol oxidase catalyses in two reactions, they are hydroxylation and oxidation. Both basic reactions needed oxygen as a co-substrate, and survive in optimal ph of Below is an example of a reaction of melanins from a basic polyphenol, tyrosine (that can be found in plants). 1

2 (Toussa int and Lerch, 1987) Many of these reactions can be controlled in several treatments, such as, acid solution, heat blanching, freezing, ascorbic acid, sugar solutions and many more. Most of these treatments control the ph and a great antioxidant. These compounds prevent browning by reducing the chemical enzyme, quinones, back to their original o-diphenols. The metabisulfite can also operate as reducing agent that reacts with the quinine intermediates to make sulfoquinones, and therefore inhibit o-diphenol oxidase. These compounds will eventually gives off flavors and odors. Approach: In this experiment there will be 3 different temperature used (see table 1). Table 1.The three temperature controls in this experiment Condition Degrees (estimation) 2

3 Freezing 0ºC Room Temperature 22ºC High Temperature 45ºC 1 Temperatures will be measured before the experiment start; table above is the estimation of temperature. Then the fruits will be peel and cut into thin slices. The fruits will be weigh about 30.0 g and placed into a beaker with 60 ml of deionized water. Afterwards, let the fruits and the deionized water sits for 10 minutes. The purpose of this is to homogenized the sample and let the tissue dissolved in the solution. Then blender the solution and filter it so that the chunks of fruits wouldn t mix with the pure solution. After the pure solution is ready, they are to be put in different temperatures and observe within hours. To decrease enzymatic browning, it will be necessary to use several different treatments on the fruits. Acid will help with enzymatic browning because it s a great antioxidant and it can be found in many citrus fruits/ vegetables such as, lemon, lime, and oranges. The other treatment is Fruits Fresh. It is a white powder that is used by sprinkle in the sliced fruits or vegetables. The Fruits Fresh contains dextrose, ascorbic acid (vitamin C), citric acid, silicon dioxide, and contains no sulfites. The product is great antioxidants and will protect browning up to eight hours. Table 2 below will list the different treatments. Table 2. The treatments use for decreasing the effect of enzymatic browning Treatment Description Acid (lemon juice) Great antioxidant Fruit Fresh Great antioxidant and stops browning Then the fruits will be peel and cut into thin slices. After the fruits have been sliced, they will be put into each treatment and observe within hours. There will be also a control to compare the texture of each fruit. Work Plan: Time Description 3

4 Preperation of the experiment. Clean objects to be used (such as blender, knive, etc) and get the 9:00 objective tools ready to used (like spectrophometer, thermometer, etc) 10:00 cut and get the fruits ready 11:00 Put the fruits in different temperature 11:30 Leave for class 2:00 Check and observe the results of the temperature effect Preperation of the experiment. Clean objects to be used (such as blender, knive, etc) and get the 9:00 objective tools ready to used (like spectrophometer, thermometer, etc) 10:00 cut and get the fruits ready 11:00 Put the fruits in different treatments to control the browning effect 11:30 Leave for class 2:00 Check and observe the results of the treatments The experiment will be done until satisfying results are obtained. Results Table 1. Description of various sample codes used during trials Sample number Description Sample 801 (1) Apple, banana, and pear juice at 0 C Sample 802 (2) Apple, banana, and pear juice at 22 C Sample 803 (3) Apple, banana, and pear juice at 45 C water bath Sample 901 (4) Apple, banana, and pear in lemon juice (control) at 22 C Sample 902 (5) Apple, banana, and pear in Fruit Fresh at 22 C Trial 1 Table 2. Average data for subjective test, based on visually looking at the color of each juice Sample Sample Sample Sample Sample

5 Figure 1. The overall rating of five samples for trial one Table 3. The wavelength of each juice and its condition at 600 nm using spectrometer Sample Sample Sample Sample Sample Figure 2. The wavelength of apple, banana, and pear in its conditions at 600 nm 5

6 Table 4. The viscosity of each juice using the Brookfield viscometer Sample Sample Sample Sample Sample Trial 2 Table 5. Average data for subjective test, based on visually looking at the color of each juice Sample Sample Sample Sample Sample Figure 3. The overall rating of five samples for trial two Table 6. The wavelength of each juice and its condition at 600 nm using spectrometer Sample Sample Sample Sample Sample

7 Figure 4. The wavelength of apple, banana, and pear in its conditions at 600 nm Table 7. The viscosity of each juice using the Brookfield viscometer Sample Sample Sample Sample Sample Trial 3 Table 8. Average data for subjective test, based on visually looking at the color of each juice Sample Sample Sample Sample Sample

8 Figure 5. The overall rating of five samples for trial three Table 9. The wavelength of each juice and its condition at 600 nm using spectrometer Sample Sample Sample Sample Sample Figure 6. The wavelength of apple, banana, and pear in its conditions at 600 nm 8

9 Table 10. The viscosity of each juice using the Brookfield viscometer Sample Sample Sample Sample Sample Discussion The panelists used in the rating were about people and the age of 20 s. Some of the panelists were in the food science or nutrition majors, so therefore they had some knowledge about the subject. The results of the overall rating of all the three trials were very close, as the temperature went up, the darker the discoloration of apples, bananas, and pears. In the 0 C the color of the fruits didn t change that much and still showed the origin light color. However, in the 22 C and 45 C, the discolorations of the fruits were darker, especially in the 45 C. The fruit that showed the most change was bananas because the original color of the banana is very light yellow in the beginning, as it went to enzymatic browning, the color became very dark brown, almost black color. As for the apples and pears, they were brown to begin with, so it was really hard to see the changes compare to banana where it was very clear. This means that in 0 C, the cold temperature suppressed the enzymatic reaction. While at room temperature, the enzymatic reaction went on but in a steady rate. In the 45 C water bath, the rate of the enzymatic browning was fast; it took only a couple of minutes for the juices to turn dark brown color. The proteins were denatured as the temperature goes up, but there are other factors that may affect the color to go darker such as exposing to oxygen, and the fruit juices weren t actually boiled, so the enzyme might not be denatured. The other two were controlled by lemon (acid) and Fruit Fresh. They both showed similar results and were at the lighter color. Lemon contains a great source of Vitamin C. The Vitamin C 9

10 is used as an antioxidant and oxidizes instead of forming the tannin pigments. As mention above, the Fruits Fresh contains dextrose, ascorbic acid (vitamin C), citric acid, silicon dioxide, and contains no sulfites. Dextrose is D-glucose that act as a physical barrier; it coats the juice and protects the juice from oxygen contact. The ascorbic acid and citric acid are same as the lemons, they all act as antioxidant. There are many ways to stop enzymatic browning. Some of them include reducing oxygen by vacuum pack or inserting gas (such as Helium, Carbon Dioxide, etc) into the product, heat blanching where the product is boiled before freezing, and removing substrate. In the second experiment, the wavelength is done at 600 nm absorbance. All trials had almost the same results. For all the fruits, as the temperature goes up the wavelength goes down. The banana has a higher wavelength compare to apple and pear, respectively. According to Whitaker and Lee, the wavelength is obtained by oxidizing catechin for an hour and the presence of polyphenolxidase (PPO). This means, the room temperature sample shows the most presence of PPO. The other samples showed a very mixed results but not as much PPO compare to room temperature sample and freezing, respectively. The PPO is the enzyme that catalyses the browning reaction. PPO catalyzes the oxidation into o-diphenols and finally produced o- quinones. The quick production of the quinones resulted in the browning of the fruits. The thickness of the fruit cell wall has a play in the flavor, color, and texture. In experiment three, viscosity of the fruit juices will tell how the texture of the fruits as it ripens. From looking at table 4, table 7, and table 10, apple is the least viscosity, then banana and pear. The apples might have ripened when is used for the experiment and might have a factor on the experiment. The bananas showed mixed results, but mostly it has normal viscosity. Finally, the 10

11 pear is the most viscosity, and some of the pear had little bruises, therefore it had an effect on the test results. In conclusion, the experiment went really well. Apples, bananas, and pears showed the most browning in the 45 C, while not so much in the 0 C. In the 22 C, the browning happened in a very steady rate. Some of the errors during the experiment include, not working quick enough (exposing the product to oxygen), the equipment used not working properly (having mixed data results) and the temperature wasn t stabile (because opening/closing of the temperature place). 11

12 Date: Please Rate the following (Samples are in order, apple, banana, and pear, respectively) (1= very light, 5= normal (not too dark/too light) 10= the darkest) Sample 801 Sample 802 Sample 803 Sample 901 Sample 902 Comments: Thank you! 12

13 References: Whitaker, J.R. & Lee, C.Y Recent advances in chemistry of enzymatic browning. In C.Y. Lee & J.R.Whitaker, eds. Enzymatic Browning and Its Prevention, p ACS Symposium Series 600, Washington, DC, American Chemical Society. Toussaint, O. & Lerch, K Catalytic oxidation of 2-aminophenols and ortho hydroxylation of aromatic amines by tyrosinase. Biochem., 26: Waganingen University Browning Reactions. Netherlands. Marshall, Maurice R., Kim, Jeongmok, and Wei, Cheng-I Enzymatic Browning in Fruits, Vegetables, and Seafoods. Nutrition and Food Science Department of University of Florida. FAO. p X. Dong, R.E. Wrolstad and D. Sugar. (2000) Extending Shelf Life of Fresh-cut Pears. Journal of Food Science 65:1,