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Appréciation
Concernant la présentation orale.
La durée est parfaite (5:21 mins),
N'oublie pas de bien prononcer le morphème –ed : "interested", "performed", "if it has "degraded",
"The following problematic" =} "the following problem-question"
"which experiment we do =} did OU "we also do =} did car ce sont des actions au passé, donc il faut utiliser le prétérit.
Quelques erreurs à éviter : il faut utiliser le futur pour introduire le sujet, par exemple "we will show/speak out…."
Attention à la prononciation de certains mots (surtout "transparents") comme "microorganisms", "petri-dishes",
Il faut bien prononcer les "s" à la 3ème personne du singulier et après chaque mot au pluriel.
C'est très bien présenté et ton texte est bien écrit.
Potatoes
I-The socio-cultural challenges of the project
We chose the theme of organic and non-organic potatoes because nowadays we often eat this tuber. We were also interested in the conservation of organic and non-organic potatoes. We have also noticed that the French are consuming ever more organic products.
In fact, 9 out of 10 French people consume organic products. Organic farming is a mode of production which finds its originality in the use of agricultural and breeding practices concerned with respecting environment. It also excludes the use of synthetic chemicals, GMO.
By consuming organic products, we fight against pollution and against the use of chemicals. It also allows you to eat healthy and balanced foods. We also found that the consumption of potatoes in France per year and per person is 27.5 kg.
We therefore wanted to work on the cold sweetening of organic and non-organic potatoes which consists in keeping the potatoes at low temperature (below 5°C), helps to limit weight loss of the potato, to control the scurf silver and the dartrose and also to reduce or suppress germination. But it also promotes the formation of soluble sugars, in minimum quantity at maturity of the tuber. It is therefore necessary to find a compromise between a fairly high value (9-10°C), making it possible to avoid sugars in the cold and a lower value (6°C), limiting the sweetening of senescence (limits aging of potatoes).
Organic potatoes have a higher glucose intake than non-organic potatoes because non-organic potatoes are grown with pesticides unlike organic potatoes. To study that we used the following problematic:
Do organic and non-organic potatoes keep the same way depending on their storage temperature?
II-Choice of experiments
To answer to the problematic, we performed four experiments. First, we chose to do the dosage of glucose enzymatic. We chose it to do the GOD-POD test which will let us determine if it has degraded the glucose. This will allow us to compare the quantity of glucose in the organic potatoes and non-organic potatoes. Then we will do a thin layer chromatography in order to show which carbohydrates are present in organic and non-organic potatoes at each temperature of preservation. The study of microbial flora allows us to see if an organic potato kept at a given temperature contains more or less microorganisms than a potato kept at the same temperature but which is not organic.
We have also do an enumeration of cells on:
-PCA in order to do the enumeration of the total flora on the potatoes
-Slanetz agar in order to do the enumeration of faecal cells
-Sabouraud in order to the enumeration of enumeration of yeast
The objective of these experiments is to demonstrate that organic potatoes are better for the health of the consummators than the non-organic potatoes.
I will present you the experiment of contact agar.
The purpose of this experiment is to observe whether there are microorganisms on the potato slice stored at different temperature.
We think that for contact agar, more mold will be present on contact agar of organic potatoes than on those of non-organic potatoes.
In this experiment, first we apply the potato on the contact agar during 10 seconds, then we incubated the contact agar at 37°C during 48h and, to finish, we read the results.
III- Presentation and interpretation of results
1/Results of enumeration of cells
On PCA:
We have calculated the microorganism content of organic potato kept at 37°C which is 1.06.10^6 CFU/g and that of non-organic potato is 1.2.10^5 CFU/g. There are therefore 10 times more microorganisms in the organic potato than in the non-organic potato.
We have calculated the microorganism content of the organic potato kept at 20°C, it is 1.7.10^5 CFU/g. But we couldn’t calculate this content for the non-organic potato because on the Petri dish there were less than 10 colonies.
We have calculated the microorganism content of the organic potato kept at 5°C. For the organic potato, the content is 4.75.10^5 CFU/g and for the non-organic potato, the content is 1.05.10^5 CFU/g. We can therefore be concluded that the organic potato contains more microorganisms than the non-organic potato.
Conclusion:
We can conclude that organic potatoes contain more microorganisms than non-organic ones. Concerning the storage temperatures of potatoes, we can say that those that were kept at 5°C and 20°C have about the same content of microorganisms, but those kept at 37°C a much higher microorganism content than other temperatures.
On Slanetz :
We can notice that there is absence of faecal streptococci on Slanetz agars at 37°C. We can conclude that the colonies don't develop at 37°C.
We can notice that the colonies are more numerous on the Slanetz agar of the organic potato kept at 20°C. We can therefore conclude that the faecal Streptococci are more numerous on the organic potato more than on the non-organic potato.
We can observe that the colonies are more numerous on the agar plates of the organic potato stored at 20°C. Fecal streptococci are present on organic potatoes more than on non-organic potatoes.
Conclusion:
Slanetz agar allows the detection of faecal streptococci. It can be noted that the colonies are more numerous on the petri dishes of the organic potato than on the petri dishes of the non-organic potato. At 37°C, no colony developed. At 20°C and 5°C, the concentration in UFC.mL-1 is higher on the petri dishes of the organic potato. So, there are more fecal streptococci because manure is used for organic potatoes.
On Sabouraud:
On all the agars, no colony was visible, so there was no mold growth on the Sabouraud plates.
2/Results of contact agar
We have seen that on all contact agar of organic potatoes we observe mold at any storage temperature. Whereas on non-organic potatoes we saw no mold at any storage temperature.
3/Results of TLC
We can notice that the frontal ratio of the spots of organic and non-organic potatoes stored at 5 ° C is equal to that of glucose. We can conclude that organic and non-organic potatoes contain glucose.
We can notice that the frontal ratios of organic and non-organic potatoes are close to those of fructose and glucose. we can therefore conclude that organic and non-organic potatoes kept at 20 °C have glucose and fructose.
We can notice that the frontal ratios of the spots of the organic and non-organic potatoes approach the frontal ratio of fructose and maltose. We can conclude that organic and non-organic potatoes kept at 37 °C contain fructose and maltose.
Conclusion:
We could see that at each storage temperature the potatoes, whether organic or not, contain the same carbohydrates. We have seen that potatoes stored at 5 ° C contain glucose and fructose. Potatoes stored at 20 ° C also contain fructose and glucose. Finally, potatoes stored at 37 ° C contain fructose but do not have glucose but maltose.
4/Results of the GOD-POD test
We can notice that the glucose concentration in potatoes is higher in organic potatoes than non-organic. We also see that the lower the storage temperature, the higher the glucose concentration in the potatoes.
IV-Conclusion
Through the experiments that we have produced we have been able to observe that organic potatoes contain more microorganisms than non-organic potatoes. A high temperature (37°C) can affect the concentration of microorganisms on the potatoes which is higher, however this temperature supports the growth of fecal streptococci. Organic and non-organic potatoes contain the same carbohydrates but the concentration varies depending on the organic or non-organic potato and also depending on the storage temperature. In fact, if the potato is organic it will contain less glucose and the lower the storage temperature, the higher the concentration of glucose.
In conclusion, organic potatoes are not stored in the same way and the storage temperature also changes certain elements of the composition of the potato.
