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Risk assessment
Evaluation and conclusion

How does the conversion of starch to glucose in nectarines (prunus persica) under two different fruit ripening techniques change over the course of seven days?

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Figure 1 - Glucose Molecule
Figure 1 - Glucose Molecule

One of the most crucial carbohydrates in biochemistry, glucose plays a crucial role in the two most fundamental biological processes, photosynthesis and cellular respiration. Digestional enzymes convert starch molecules (polysaccharides) into glucose (monosaccharide) during the ripening process. The introduction of ethene gas allows for the completion of this procedure. Ethene gas is a biological hormone that plants employ to drive important processes like seed germination, fruit abscission, and fruit ripening. It is more easily produced by some fruits, like bananas and apples, and will speed up fruit ripening when placed in a constrained space, such a plastic bag or box. Burying the fruit in rice has been suggested as a different approach. The ethylene gas produced by the fruit should last longer in it.


The three ripening conditions that will be simulated in this experiment are all thought to cause the ripening process. A banana and a nectarine will be combined in a sealed bag for the first test. In the second, rice will be placed in a plastic box with a nectarine underneath it. Thirdly, the null hypothesis will be established by placing a nectarine alone in a plastic bag as the control, supporting the idea that the creation of ethene gas and the level of glucose are unrelated processes. It is crucial that all three trials be carried out in enclosed spaces since they encourage the retention of ethene gas.


The level to which ethene gas has impacted the metabolism of starch and the concentration of simple sugars in nectarines has been determined in this experiment by the presence of glucose.


A coloured indicator made of potassium permanganate (KMn04) solution and an acid, in this case sulphuric acid (H2SO4), can be used to identify the presence of glucose. Alkenes are converted to glycols by the powerful oxidising agent KMn04 solution, allowing for a quantitative test for the existence of unsaturated bonds in a sample. The pink tint of the KMn04 solution shows how starch is converted to glucose during metabolism.


The amount of time it takes for the pink colour to go away is indicative of the amount of glucose present in the filtrate sample; the shorter the time it takes for the colour to go away, the more glucose is present in the sample.


The nectarines subjected to the rice packing trial are anticipated to mature the quickest. They are placed in a controlled atmosphere that will encourage the retention of ethene gas around the nectarine. As a result, in this trial, the concentration of monosaccharides (glucose) would rise faster and the concentration of polysaccharides (starch) will fall faster. Because the ethane produced by the banana will supplement that produced by the nectarines themselves, the nectarines kept with the banana will also ripen more quickly than the control.



  • 36 nectarines
  • 12 bananas
  • Snap lock bags, plastic containers
  • Basmati Rice (approximately 3kg)
  • 560ml Sulphuric Acid 1M (H2S04)
  • 230ml Potassium Permanganate solution 0.01M (KMnO4)
  • Knife, cutting board, food processor, sieve
  • Stop watch
  • Syringes - 3ml, 5ml and 10ml
  • 4x 750ml beaker (each repeat)
  • 12x 50ml beaker (each repeat)


The purpose of this experiment is to ascertain how ethene gas influences nectarines' glucose content. Two popular fruit ripening techniques, rice and banana packaging, were examined alongside a control in order to draw a conclusion. The techniques listed below are appropriate for each of these situations.


It was agreed that steps should be done to reduce this inaccuracy as much as possible because the "end point" of the solution, or when the pink colour vanishes and the stop-watch is stopped, is subjective. Four nectarines were ground up and successfully tested on each day of the three different circumstances (banana, rice, and control). Three different tests were performed on each nectarine's filtrate. This was done in order to avoid discrepancies in the results and to eliminate any inaccuracy that might have been caused by the solution's stirring.


On Day 1 of the experiment the following were set up:


  • A snap-lock bag contained a banana and a nectarine. The bag was sealed once the air inside it was taken out.
  • One nectarine was put into a box made of plastic. The box was sealed once the container had been completely filled with rice to completely encase the nectarine.
  • I put one nectarine in a snap-lock bag. The bag was sealed when the air was taken out of it.


This was repeated in four trials for each treatment.


One untreated nectarine was retained on Day 1 to establish the initial glucose levels.


Fruit was stored at room temperature for 3, 5, or 7 days. Following the removal of the nectarines at the conclusion of the time period, qualitative observations and measurements of the glucose levels were taken.


  • The nectarine's flesh was taken out and put in a food processor. The identical processor was then used to pulse 500ml of distilled water for 30 seconds. A sieve was used to filter the liquid into a 750 ml beaker.
  • In a 50ml beaker, 10ml of the nectarine filtrate was added. In addition, the beaker concurrently received 5ml of H2SO4 solution and 2ml of KMn04 solution. The stopwatch was instantly begun. The solution was continuously swirled at a consistent rate.
  • The stopwatch was stopped, and the amount of time taken was noted, once the pink tint of the solution had vanished.


From the filtrate of each nectarine, this was done three times.


Figure 2 - Table On Variables
Figure 2 - Table On Variables

Risk assessment

All apparatus was labelled with relevant information (name, date class nature of materials and experiment)


All unnecessary materials were cleared away from the work space.


Glassware is fragile it was used towards the centre of the bench with stable supports.


Sharp cutting tools and the blender were used with care.

Electrical apparatus

The connections of the balance, magnetic stirrer and blender, were kept away from running water and trailing cables were avoid


Spills were cleaned up


Sulphuric acid is corrosive and toxic.


KMnO4 is a powerful oxidiser and can cause fires.


Eye protection, gloves and lab jacket were worn when handling these chemicals.


Figure 3 - Table On Observations Of The Three Methods On The Ripening Process
Figure 3 - Table On Observations Of The Three Methods On The Ripening Process
Figure 4 - Table On Amount Of Time Taken For The Pink Colour Of The Potassium Permanganate Solution To Disappear
Figure 4 - Table On Amount Of Time Taken For The Pink Colour Of The Potassium Permanganate Solution To Disappear

N.B Since only one nectarine was used to measure the starting levels of glucose, there is only one value for Day 1. For all following trials, this value served as the baseline (Day 1 value).

<p>Figure 5 - Table On Time Taken To Decolorise KMnO<sub>4</sub>, By Extract Of Nectarines Inclubated With Banana, Rice Or Nothing. Error Bars = &plusmn; 1 Standard Deviation</p>

Figure 5 - Table On Time Taken To Decolorise KMnO4, By Extract Of Nectarines Inclubated With Banana, Rice Or Nothing. Error Bars = ± 1 Standard Deviation


The data for the banana treatment and the control reveal no variation in the amount of time required, with the exception of the first seven days. Day 7: The control appears to have a higher glucose content than the banana treatment. I made the decision to assess the importance of this discrepancy.


Null Hypothesis = there is no difference between the results for the banana treatment and the control on Day 7


Alternative Hypothesis = There is a difference between the results for the banana treatment and the control on Day 7


t-test equation


\(t = \frac{|\bar{X_1}\ -\ \bar{X_2}|}{\sqrt{\frac{S^2_1}{n_1}\ +\ \frac{S^2_2}{n_2}}}\)


tcalc = 2.93


For p = 0.05 using a two tailed test


tcrit = 2.07


Consequently, there is a big disparity. The null hypothesis is disproved but the alternative hypothesis is kept. However, this difference is only significant to p = 0.01 and is not very significant.


Standard Reference Curve for Glucose Concentration

Glucose / %
Time taken / s ± 0.05s
Figure 6 - Table On Glucose Calibration
Figure 7
Figure 7

Unfortunately, the collected data fell outside of the standard curve's acceptable range, making it impossible to estimate the filtrate's glucose concentration using this curve.

Error and limitations

mistake-reducing techniques were used when possible, although it was noted that the experiment's methodology had several shortcomings and that the trial results were prone to mistake.


Uncertainties were accounted for and are recorded below:

Identify uncertainty
Degree of uncertainty
Reaction time ± 0.05 s
3ml syringe
± 0.1ml
5ml syringe
± 0.1ml
10ml syringe
± 0.2ml
± 1.0m
Figure 8

The level of uncertainty in each trial would have remained consistent because the experiment's glassware was not changed from trial to trial. Care was taken to measure precise values, such as the volume of sulphuric acid, potassium permanganate solution, and nectarine filtrate added to each trial, as well as the amount of water put to the food processor. Due to its reliance on the experimenter's reaction time, the stopwatch would have introduced the most uncertainty into the methodology. While the observer remained the same during each trial, a variety of circumstances could have had an impact on how quickly the stopwatch was started and stopped, and consequently, the time that was recorded. The 'end-point' might be unbiased checked using colorimetric techniques to improve the process. The colorimeter could be used to measure the amount of time it took for a standard solution to absorb a specific amount of light. Similar tests would be conducted for each experiment.


The indicator solution for this experiment, potassium permanganate, is a potent oxidising agent. The potassium permanganate may have reacted with contaminants in the nectarine filtrate due to its capacity to transform alkenes to glycols and subsequently identify the existence of unsaturated bonds in a solution. In this situation, the results would have been significantly impacted because the time it took for the pink colour of the potassium permanganate solution to vanish might not have been used to test for glucose alone. In truth, the experimenter was checking for a different variable—the metabolism of contaminants in the filtrate, which had not been taken into consideration in the methodology. Another indicator solution, such as iodine solution, that does not react with contaminants to the same degree as potassium permanganate could be used to reduce this mistake. Iodine solution, which is dark blue in colour, can identify the presence of starch in biological materials. Iodine might be used to demonstrate how the concentration of starch in the nectarine filtrate decreases with fruit ripeness since starch hydrolyzes into glucose molecules. An alternative would be to utilise a particular glucose test, like the one diabetics use.


The time it took for the pink tint of the potassium permanganate solution to vanish when placed with the filtrate was tested three times using a constant solution, and it was concluded that each individual fruit should be examined three times. Testing each solution three times reduced any error that might be related to the stirring of the solution and reduced the possibility of outliers in my results because the "end-point" test is subjective and looks for a change in colour to indicate the metabolism of carbohydrates to glucose.


The nectarines from the Day 3 and Day 5 trials had no bearing on one another because each repetition was independent of the others. The presence of pesticides, artificial ripening agents, prior exposure to ethene gas, and other variables that were not taken into consideration in this experiment but may have been present in the duplicates might all have affected the outcomes. This effectively meant that in order to establish a connection between the production of ethene gas and glucose levels, the method was dependent on features that were shared by all nectarines. With the exception of the rice packing procedure on Day 7, the standard deviations are still within reason. In general, the standard deviation grew longer as the fruit ripened. Given that fruits will change at slightly different rates, this might be expected.


It has been demonstrated that the area of the fruit closest to the stem, known as the abscission zone, contains higher glucose contents. The person doing the experiment used all of the flesh from all of the nectarines before pulverising them into a filtrate to limit this factor. This implied that throughout the trial, the variation in glucose concentration within the fruit would not change.


One of the main sources of mistake in this experiment was the biodegradation process, in which bacteria chemically consume materials. In the banana and rice trials, after Day 5, mould, which arises from an excess of moisture in an environment, was seen on all nectarines. The estimated standard deviation values for the rice packing trial show how much of an impact mould growth had on the outcomes. A huge standard deviation (16.18 s) on Day 7 in particular showed how widely distributed the data were. Furthermore, because chance had a significant role in these findings, they cannot be trusted and are unlikely to be repeated. Temperature has an impact on microorganism reproduction. Due to the fact that the enzymes involved in the conversion of polysaccharides to monosaccharides only function within a limited range of temperatures, maintaining a constant and relatively low temperature (around 15°C) would prevent the development of microorganism reproduction without significantly altering the temperature needed for ripening. By ensuring sure the fruit is fully washed on its surface before use, the risk of the fruit becoming contaminated by germs may be decreased. One option is to sterilise the item.


To achieve environmental controls, certain steps were taken, such as controlling temperature and light exposure. The experiment was carried out at room temperature, with two daily temperature readings taken in the laboratory. During the day, it was noted that the temperature varied between 28°C and 29.5°C degrees Celsius. Between 3 p.m. and 8 a.m., no recordings were made. There would have been significant variation at night, but for practical reasons, the observer was unable to control this. Ideally, the experiment would be left in a consistently controlled environment, such as an incubator, where a constant temperature could be maintained.


The generated standard reference curve for glucose concentration turned out to be unrelated to the data. The acquired data fell below the standard curve's acceptable bounds. The standard curve could not be extrapolated to encompass the range of outcomes, making it impossible to deduce the glucose concentration resulting from the experimental trials. It would be necessary to duplicate a calibration curve using glucose values that are greater.


Only four times were repeated for each trial due to time restrictions. There would need to be 20 repeats in order to reach a conclusion. This was taken into consideration when analysing the data, and it was acknowledged that any interpretations made in light of the experiment's findings might not be entirely accurate.

Evaluation and conclusion

It was predicted that the nectarines subjected to the rice-packaging experiment would have the highest glucose content. It was believed that the rice would help retain the ethane gas that nectarines produce around the fruit, accelerating ripening and speeding up the pace at which starch is broken down into glucose. The rice and nectarines were also kept in a container that had not had the air removed. The plastic bags containing the fruit from the other two trials, however, had been devoid of air. It's likely that the elevated oxygen content in the box aided in the growth of mould by promoting its metabolism.


Because they produce ethene, bananas are used both traditionally and commercially to accelerate the ripening of fruit. The data, however, do not support this claim. Even though the bananas may have produced only a small amount of ethene on Day 7, the control trial's glucose concentration was higher. Although the results are not significantly different from those of the banana treatment, the ttest performed on these data indicates that this difference is significant. There are two plausible interpretations based on the fact that nectarines placed separately in plastic bags matured more quickly than nectarines placed with the bananas. First, due to a methodological flaw, the conditions in which the bananas were stored did not favour ethene formation. Or, alternatively, that the nectarines used in the control trial were influenced by elements that were not taken into consideration in this study, such as the fact that they started out with higher glucose concentrations.


Figure 1 illustrates how nectarines grew their glucose concentration from Day 1 to Day 3 in all three trials at a comparable rate. Thus, we can assume that during this time, nectarines metabolised starch at a similar pace and generated roughly the same amount of ethene gas. Except for Nectarines 1 and 4 of the banana study, there were no definite evidence of mould on Day 3 as can be seen in the Qualitative Data Table.


The banana and controlled trials both increased their glucose concentrations at a similar rate on Day 5 of the experiment, but more slowly than they had from Day 1 to Day 3. However, the rice packing experiment's glucose concentration had been rising at the same rate, showing that the glucose concentration (y-axis) and time (x-axis) have a linear connection. The nectarines that had been exposed to these conditions were all mouldy and were exuding a white residue. This was not true for the nectarines in the controlled test with bananas, which had very little to no mould. One can infer that the reason for the sudden rise in glucose content was the presence of mould. The nectarines' starch is likely being hydrolyzed by the mold's enzymes.


From Day 5 to Day 7, the nectarines in the banana and controlled trials' glucose concentrations grew steadily higher, whereas the nectarines in the rice packaging trial's glucose concentration started to fall. Most likely eaten by the bacteria. At the same time, it was noted that all of the nectarines in this trial had started to become more and more mouldy, with at least 90% of them being covered with the growth. Additionally, it was noted that all nectarines were secreting a white residue. A possible inference from this data is that there is a "threshold" at which an increase in the glucose concentration is balanced by an increase in the growth of mould colonies. Increasing glucose levels result from the metabolism of big starch molecules. This process progresses in tandem with the development of bacterial and fungal colonies, which feed on the fruit's rising concentration of simple sugars and'spoil' it. According to the findings of this experiment, the greatest concentration of glucose that may be achieved is that which corresponds to the duration of 29.53 seconds it took for the pink colour of the potassium permanganate solution to vanish. Following this, the amount of glucose produced by the hydrolysis of starch is outweighed by the amount of glucose eaten by the microbial colonies, leading to a drop in glucose concentration. As seen in all three trials, the emergence of mould before this "threshold" had no appreciable impact on the rising glucose levels.


The removal of air (oxygen) from the plastic bags served as the only distinguishing characteristic in this experiment. Day 5 glucose levels in the controlled and banana trials were comparable, and the air had been removed from both of these experiments. Therefore, it seems improbable that the banana's ethene gas had a substantial role in the transformation of starch into glucose. The rice trial's glucose content was noticeably greater because the box's air was not removed. Because ethene gas would have been kept around the fruit in the control trial as well, the theory that the presence of rice caused the ethene to be concentrated around the fruit is unsupportable. It is more plausible that the presence of air, specifically oxygen, encouraged the development of mould and increased glucose levels.


With the exception of Day 7 of the rice treatment, all of the trials yielded results that were essentially identical (the final values all fell within a 4-second window). Qualitatively, it was noted that all of the nectarines were mouldy and rotting. The high standard deviations that were determined as a result of these findings highlighted the wide variation in the data around these three points and showed how unreliable the information from the rice treatment's Day 7 data was. Although the R2 values for the control and banana treatments are still high, the R2 for the rice treatment is lower, which reflects the issues with these fruits.


It was likely that other substantial chemical reactions were occurring inside the nectarines at this point because they were seen to be coated in mould. The rice packaging trial produced an error bar that covered all of the experimental findings from the other trials, with a standard variation of 17.8 seconds (see Figure 1). The experiment's findings are partially the outcome of processes that were not anticipated at first.


J.Beruter and Ph. Droz Studies on locating the signal for fruit abscission in the apple tree., Swiss Federal Research Station for Fruit-Growing, Viticulture and Horticulture, CH-8820 WadenswilSwitzerland, Accepted 8 October 1990- Available online 14 October 2003


Antony Brach and Christopher Perkins 20/01/05


J.H.LaRue & R.S.Johnson (1989) Peaches Plumbs and Nectarines U Cal Google Books ce=bl&ots=8Iab1znGzd&sig=bjD1Nk0gCGTwj3zlbRenFlbREms&hl=en&sa=X&ei=wzo6T_C3LYfL0QW Kk42QCw&redir_esc=y#v=onepage&q=starch%20in%20nectarines&f=false


Matthew Rogers 14/06/11