I do however recognise various limitations of the experiment which could reduce the reliability of the findings.
Limitation 1:
The cuvettes could have fingerprints or scratches on them.
If this is the case then the results will be a much higher absorbency rate i.e the light won’t be able to travel through the fingerprints or scratches as easily so the solution will be treated as being darker (and having more betacyanin) than there actually is.
The graph would be the same shape but the perceived point of denaturation could be at a lower temperature. Therefore I could have concluded the point of denaturated to be too low.
Limitation 2
In the treatment vessel, each of the disks were put into a test tube, and left for 20 minutes to leak the betacyanin from the damaged (high temperatures) cell membranes. In a lot of cases the disks stacked up.
Each of the disks measure 5mm diameter and 5mm dept. This means each of the disks surface area is:
117.7cm²
Therefore by using 6 disks the surface area should equal 6*117.7=706.2cm²
However if the disks stack up, as shown in the diagram below, the entire surface area will be:
133.4 cm²
This is a difference of upto 572.8cm²
It is the cells on the surface that are going to leak betacyanin, so a smaller surface are would mean less pigment leaked. Therefore if the disks in my experiment stacked I would make the conclusion that the point of denaturation is higher:
Possibly the most important limitation, is the genetic and natural variations of the beetroot. I had to use more than one beetroot in order to cut out the appropriate number of disks for the experiment. However each beetroot differs a lot.
Limitation 3
In one beetroot there may be more betacyanin than in another betacyanin.
If this was the case, more betacyanin would leak from the beetroot because there is more betacyanin to leak.
If a beetroot had more betacyanin in the cell vacuole the graph would change. My theory was that the graph levels off because there is a limited amount of betacyanin.
Limitation 4
The beetroot may not be homogenous.
Betalines are the red-purple pigments of beetroot. Betacyanines comprise of about 90% of beetroot betalines. The most important betacyanin is betain. This makes up 75-95% of the total colouring matter. In each beetroot the percent of the purple pigment may vary.
In a beetroot where there is a larger % of betacyanin, the absorbancy rate will be higher because the light will not be able to travel through the darker substance as well.
Limitation 5
Also there may be a difference in ages of the different beetroot I used. The beetroots develop red colouration during development at maturity, and during senescence. Many plants produce betacyanins as the basis of this colour. I.e the age of the beetroot affects how much betacyanin there is present in the cell vacuole.
This means, as I used more than one beetroot, as they could have been different ages there would be a different amount of betacyanin the each cell. This will render the same problems are in limitation 3.
This would affect the conclusion because an originally extraneous variable (amount of betacyanin in the cells) has turned into a confounding variable. The conclusions I originally made about the experiment are therefore less reliable.
Other limitations include:
Room temp change during the experiment
Difference in sizes of the disks as they can’t be cut exact
Different degrees of mechanical damage due to transferring beetroot disks
