Apple bio lab

Determining the Effects of Temperature, pH and Oxygen Enzymatic activity on Browning Apples

Roni Hasan

20964697

Lab Partners: Ivanka Liu, Manthira Jayendran, Pooja Chumber, Dima Ahmad

TA: Prakriti Chhabra

BIOL 130L Section 003

Sunday 11:59 pm

September 26, 2021

Introduction

Purpose: To determine if the change in either temperature, pH, or oxygen levels will affect the enzymatic reaction with the browning of apples.

Background: Apple browning occurs because of an enzyme called polyphenol oxidases. When the enzyme is exposed to oxygen, the polyphenols break down. This results in many reactions including colouring (Hartel, 2008). “This reaction, called enzymatic browning, is a form of plant defence against pests and pathogens” (Hartel, 2008) These chemicals generated are been found to be very effective against these pests and pathogens.

Materials and Methods

All procedures were carried out as outlined in Browning Apple Lab, BIOL 130L lab manual pages 18 - 24 (Department of Biology, 2018). No deviations were made to these protocols

Results

Table 1: Degree of apple browning at 3 hours

(✓) represents brown colour, (x) represents no colour

Table 1 showcases the degree of browning that occurred to each apple in 3 hours. More browning was indicted by more ✓ for example (✓✓✓) was the most, and the opposite for lower amounts of ✓. x indicted the apple had no browning.

Figure 2: The degree of Apple browning over time

Figure 2 showcases the rate of apple browning, this is accomplished through an analysis of the extent the effect of each variable has on each apple slice browned every 15- minute time intervals, this is because it was checked every 15 minutes in 3 hours. The graph showcases which variable had the greatest effect on browning.

Discussion

From the experiment, it was found all variables put on the apple reduced the browning, with lemon juice having no browning. This is due to lemon juice has citric acid, “citric acid react with metal ions and change their chemical make-up.” (Fox, 2019) Figures 1 and 2 showcases that lemon juice is most effective at reducing browning to being 100% effective. Since it was stated that the reaction to happen oxidation is required, it was unexpected that the apple did brown because in water it is not exposed to oxygen, therefore oxidation should not occur. This could have been due to the apple was taken out of the water during the 15-minute intervals when it was recorded, exposing it to oxygen, giving a source of error; because they could have browned here. To fix this taking photos in the water allow the apple to always be in the water, fixing this issue.

References

Department of Biology. (2020). Introductory cell biology laboratory. Waterloo, Canada: University of Waterloo Print + Retail Solutions.

Fox, R., & 21, A. (2019, August 21). Why do apples turn brown after you cut them? Let's Talk Science. Retrieved September 26, 2021, from https://letstalkscience.ca/educational-resources/stem-in-context/why-do-apples-turn-brown-after-you-cut-them.

Hartel, R. (2008, October 20). Curiosities: Why do apple slices turn brown? News. Retrieved September 26, 2021, from https://news.wisc.edu/curiosities-why-do-apple-slices-turn-brown/.