Sources of Uncertainty
One of the main sources of uncertainty was the moisture in the room during the experiment. The experiment was conducted on three different days for each of the trials, all with different kinds of weather. Out of the three days, one of the days was snowy, the other was rainy, and the last was dry. The rain created a slightly more humid environment in the room that the experiment was conducted in, as the warmth and moisture of the rain entered through cracks in the windows, or open doors. Polyphenol oxidases need a sufficient supply of water to be properly activated, so on dryer days, there may not have been enough water in the air to fully sustain the enzymes. This could have possibly altered the results.
Accurately measuring the different shades of brown on the cubes of fruit was also a difficult task, as the chart had many different shades of brown which were all extremely similar to each other. The fruits that were cut of first also began to oxidize seconds before the others, allowing for it to possibly become a slightly darker shade of brown. The type of knife that was used also affected the oxidation process of the fruits. Stain-less steel metal knives accelerate the process because they are usually made up of a mixture of iron and copper which react with the polyphenol oxidase enzymes. A ceramic knife would have kept the oxidation process to be completely natural and would not have sped up the oxidation process unnaturally. Lastly, the polyphenol oxidase enzyme concentration and the phenolic substrate concentration was not known beforehand.
Accurately measuring the different shades of brown on the cubes of fruit was also a difficult task, as the chart had many different shades of brown which were all extremely similar to each other. The fruits that were cut of first also began to oxidize seconds before the others, allowing for it to possibly become a slightly darker shade of brown. The type of knife that was used also affected the oxidation process of the fruits. Stain-less steel metal knives accelerate the process because they are usually made up of a mixture of iron and copper which react with the polyphenol oxidase enzymes. A ceramic knife would have kept the oxidation process to be completely natural and would not have sped up the oxidation process unnaturally. Lastly, the polyphenol oxidase enzyme concentration and the phenolic substrate concentration was not known beforehand.
Validity and Reliability
There are a few sources that can affect the validity and reliability of the experiment. Based on many different studies done, it states that there are many factors that cause enzymatic browning, thus causing different reactions of the same fruits. As polyphenoloxidase activity is highly affected by temperature, the data we collected were all within the same temperature ranges during the same season; thus this data has not been tested across different temperature to see the different results. Although we chose to use 3 different types of fruits, we only used one variety of each fruit. With this experiment, we generalized that the results would be the same for all apples, pears, and avocados. This data is not very reliable because the effects can be completely different between Fuji apples, Golden Delicious apples, or Gala apples. Other factors that can affect the validity and reliability are the liquids used for this experiment. For example the concentration of the chemical composition of the liquids can vary between different brands, which can also then alter the results of this experiment. For this experiment, we used freshly squeezed orange juice, which when compared with store bought has a significantly lower level of sugar content which is a factor for the rate of enzymatic reactions. The rate of enzymatic browning are caused by a few important elements; the amount of phenol compounds, popyphenoloxidase activity, the growing conditions and fruit maturity. When we were choosing our fruits, the ripeness of the fruits were not all the same which again could alter the results. The pears and apples were a little bit more to the ripe side, whereas the avocado due it not being grown in its peak season, was not ripe.
Possible Improvements During Future Experimentation
In future experimentation, it would be wise to expand to vegetables as well as fruits. This can compare the different levels of polyphenol oxidases in both fruits and vegetables, creating a better understanding of the distribution of polyphenol oxidases in nature. Expanding to many different liquids with distinctly different pH levels will also create a more accurate depiction of the effect that pH levels play on the oxidation of produce. The six different liquids should be organized based on pH levels, allowing an easier comparison process. This will in turn, create a more concise conclusion. Having an even number of acidic, neutral, and basic solutions will also allow the comparison of the effects of the different solutions to be more simple and more accurate. As well, experimenting with binary mixtures in different concentrations can demonstrate the effectiveness of two different solutions together. Complex mixtures in certain concentraions may be involved in the enhancement of the inhibitory action as shown by a publication done by Francesco Pizzocaro, Danila Torreggiani and Gianluca Gilardi ⁴. It showed that ascorbic acid and sodium chloride alone increased the polyphenol oxidase activity whereas when both solutions were combined, the polyphenol oxidase activity was inhibited. Lastly, choosing different kinds of produce with different polyphenol oxidase concentrations will create a better understanding of the role that the enzymes play in the oxidation of fresh produce.