To study the presence of oxalate ions in guava fruit at different stages of ripening Project PDF Class 12
Introduction
Guava, a tropical fruit popular in India and worldwide, belongs to the Myrtle family (Myrtaceae) and the genus Psidium, encompassing around 100 species of tropical shrubs and small trees. Known for its sweet flavour and high vitamin C content, guava is also a rich source of oxalate ions, which are organic compounds of interest due to their potential impact on health, particularly in relation to kidney stones.
As guavas ripen, they undergo significant changes in colour, texture, and chemical composition. Initially green and firm, the fruit softens and turns yellow when fully ripe. During this ripening process, the concentration of oxalate ions within the fruit varies, influencing its nutritional profile.
Additionally, guavas are recognized for their distinctive aroma, similar to lemon rind but less intense, adding to their appeal. This project aims to study the presence and variation of oxalate ions in guava fruits at different stages of ripening.
What is Oxalate?
It is a carboxylic acid, primarily found in plants and animals. It is not an essential molecule and is excreted from our body, unchanged. Our body either produces oxalate on its own or converts other molecules like Vitamin C to oxalate. External sources like food also contribute to the accumulation of oxalate in our body. The oxalate present in the body is excreted in the form of urine as waste. Too much of oxalate in our urine results in a medical condition called hyperoxaluria, commonly referred to as kidney stones. Diet is looked upon as a preventive measure in addition to medication to treat kidney stones.
Aim
To study the presence of oxalate ions in guava fruit at different stages of ripening
Theory
Oxalate ions are extracted from the fruit by boiling the pulp with dilute H2SO4 . The extracted oxalate ions are then measured volumetrically through titration with a KMnO4 solution. In this process, a reagent known as the titrant, which has a known concentration (standard solution) and volume, is used to react with the solution containing the analyte or titrand, whose concentration is unknown. By using a calibrated burette or a chemistry pipetting syringe to add the titrant, the exact amount consumed can be determined when the endpoint is reached. The endpoint, identified by an indicator, marks the completion of the titration and ideally coincides with the equivalence point. The equivalence point is where the number of moles of titrant equals the number of moles of analyte or a multiple thereof, as seen in polyprotic acids. In a typical strong acid-strong base titration, the endpoint is reached when the pH of the reactant is close to 7, often indicated by a persistent colour change, such as the pink hue of phenolphthalein indicator.
Material Required
Apparatus
100ml Measuring Flask
Pestle and Mortar
Beaker
Burette
Funnel
Weighing Machine
Filter Paper
Chemicals
Dil. H2SO4 Solution
N/10 KMnO4
Guava fruit at different stages of ripening
Procedure
- Take three fresh pieces of guava of small size. Number these as 1, 2, and 3, keep these at room temperature.
- Take 50g of guava from piece and crush it into fine pulp using pestle and mortar.
- Transfer the crushed guava to a beaker and add 50 ml dil.. Boil the contents for 10 minutes.
- Cool and filter the contents in a 100 ml measuring flask. Make up the volume up to the mark by adding distilled water.
- Fill the burette with standard
- Note down the initial reading of solution in the burette.
- Pipette out 20ml of this solution into a conical flask/titration and add 20 ml of dil. Sulphuric Acid to it. Heat it to 60-70 .
- Add solution from the brute into Titration flask slowly till permanent light pink colour is obtained. Note the reading of upper meniscus in the burette.
- Repeat steps 6, 7, 8—3-4 times so as to get concordant readings.
- Repeat steps 2-9 with guava sample 2 after 1 day and with guava sample 3 after 2 days.
Observation
- Weight of the guava fruit for each time was 50 g.
- Volume of guava extract taken for each titration was 20 ml.
- Normality of KMnO4 solution was- 1/10
- End Point: Colour Changes to pink
Guava Solution | Burette Reading (Initial) | Burette Reading (Final) | Volume of | Concurrent Reading |
Raw | 150 | 18 | 132 | 136.06 |
Semi-ripened | 150 | 13 | 137 | |
Ripened | 150 | 10.8 | 139.2 |
Calculation
Result
- The normality of oxalate ions of;
- Fresh guava solution is = 1.32 ml
- Semi-ripen guava solution is = 1.37 ml
- Ripened guava solution is = 1.39 ml
- The strength of oxalate ions of;
- Fresh guava solution is = 0.58 ml
- Semi-ripened guava is = 60 0. ml
- Ripened guava is = 61 0. ml
Conclusion
The investigation successfully determined the presence and variation of oxalate ions in guava fruit at different stages of ripening. The experimental results revealed that the content of oxalate ions increases as the guava ripens. The strength of oxalate ions was found to be 0.581 g/L in raw guava, 0.603 g/L in semi-ripened guava, and 0.612 g/L in fully ripened guava. This trend indicates a clear increase in oxalate concentration as the fruit matures.
The normality of oxalate ions also showed a gradual increase from 1.32 ml in raw guava to 1.39 ml in ripened guava. This aligns with the hypothesis that oxalate content changes during the ripening process.
The content of oxalate ions in guava was found to be 59.67%, which is close to the literature value of 60%. This further validates the accuracy of the experimental procedure. It is evident from the study that the content of oxalate ions increases as the guava ripens, making the fruit’s ripeness a critical factor in its oxalate concentration.
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