Sucs Naturals o Sucs Envasats
Autor: Judit Nadal Bigas
Centre: INST.HUG ROGER III
Document:
The most important aim I devote my project to is vitamin C determination in different drinks. This has helped me to make a further study of its presence in packed fruit juices
and in natural ones to observe its large oxidation capacity.
What is more, to answer the questions: ‘Which is the relation between vitamin C and colds?’, ‘Why have I always been told to drink orange juice when flu started?’ or ‘Why was my mother so obsessed to make me drink the orange juice immediately after preparing it?’, which I asked myself when I was looking for a shocking topic, I have gone deep into the vitamin C beneficial effects for health and its relation with the fruit juices.
The method we used to found the concentration of an ascorbic acid solution was the one with N-bromosuccinimide (NBS), which has the ability to liberate iodine when it reacts with potassium iodide in acid medium (in our case, acetic) but in ascorbic acid presence the last one is oxidized first.
A slight NBS excess when all the ascorbic acid has been oxidized will give the iodine appearance in the solution (we can detect this if we add a few drops of starch 2% which, together with the iodine, will dye blue/purple the solution).
To determine the vitamin C amount that is contained in the sample problem (natural or bottled fruit juice) we first needed to know the NBS solution volume required to react with all the ascorbic acid contained in five different beakers.
For each experiment we needed five beakers (numbered from 1 to 5 with labels) and in which we added different juice amounts (among other products); immediately we observed them behaviour and their coloration once the agent had been added.
The results had been obtained from calculations made after the five beakers containing juice with the five beakers containing a pattern solution (made, among other products, with 99% purity ascorbic acid in place of different sample juices) comparisons.
After its realization, it has been confirmed the vitamin C inestability due to its large capacity to oxidation by contact with air, water or even to its fotosensivity. That is to say any juice which is exposed in one of these contexts is more sensitive to its oxidation.
The practices done with kiwis, have allowed us to verify that the different ripe fruit states determine the amount of vitamin C.
Thanks to the mandarin practice I have been able to observe the variation of the vitmain C content depending on the time spent between it’s squezeed and it’s valorated.
The vitamin C determination in brick packed juices or ecological in transparent glass bottles didn’t give the expected results. The main cause was the different chemical components presence used by manufacturers for juices’ conservation, such as antioxidants. These have been the responsible for stopping the action which the NBS had to produce in the practice, therefore they have prevented, slowed or masked the ascorbic acid oxidation.
In short, we were using an oxidative method in antioxidants presence, so this means that the NBS amount spent was higher than in the natural juices practices, consequently the value which determines the vitamin C amount exponentially increased giving completely illogical results.
Finally I have been aware of the large errors amount which can be committed in the laboratory, not only because of its small and precise products uses. In my case for example, I have done two types of errors: the visual and the one related with the handling.
and in natural ones to observe its large oxidation capacity.
What is more, to answer the questions: ‘Which is the relation between vitamin C and colds?’, ‘Why have I always been told to drink orange juice when flu started?’ or ‘Why was my mother so obsessed to make me drink the orange juice immediately after preparing it?’, which I asked myself when I was looking for a shocking topic, I have gone deep into the vitamin C beneficial effects for health and its relation with the fruit juices.
The method we used to found the concentration of an ascorbic acid solution was the one with N-bromosuccinimide (NBS), which has the ability to liberate iodine when it reacts with potassium iodide in acid medium (in our case, acetic) but in ascorbic acid presence the last one is oxidized first.
A slight NBS excess when all the ascorbic acid has been oxidized will give the iodine appearance in the solution (we can detect this if we add a few drops of starch 2% which, together with the iodine, will dye blue/purple the solution).
To determine the vitamin C amount that is contained in the sample problem (natural or bottled fruit juice) we first needed to know the NBS solution volume required to react with all the ascorbic acid contained in five different beakers.
For each experiment we needed five beakers (numbered from 1 to 5 with labels) and in which we added different juice amounts (among other products); immediately we observed them behaviour and their coloration once the agent had been added.
The results had been obtained from calculations made after the five beakers containing juice with the five beakers containing a pattern solution (made, among other products, with 99% purity ascorbic acid in place of different sample juices) comparisons.
After its realization, it has been confirmed the vitamin C inestability due to its large capacity to oxidation by contact with air, water or even to its fotosensivity. That is to say any juice which is exposed in one of these contexts is more sensitive to its oxidation.
The practices done with kiwis, have allowed us to verify that the different ripe fruit states determine the amount of vitamin C.
Thanks to the mandarin practice I have been able to observe the variation of the vitmain C content depending on the time spent between it’s squezeed and it’s valorated.
The vitamin C determination in brick packed juices or ecological in transparent glass bottles didn’t give the expected results. The main cause was the different chemical components presence used by manufacturers for juices’ conservation, such as antioxidants. These have been the responsible for stopping the action which the NBS had to produce in the practice, therefore they have prevented, slowed or masked the ascorbic acid oxidation.
In short, we were using an oxidative method in antioxidants presence, so this means that the NBS amount spent was higher than in the natural juices practices, consequently the value which determines the vitamin C amount exponentially increased giving completely illogical results.
Finally I have been aware of the large errors amount which can be committed in the laboratory, not only because of its small and precise products uses. In my case for example, I have done two types of errors: the visual and the one related with the handling.