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Appréciation
Concernant la présentation orale.
La durée est parfaite (5:42 mins),
"we choose" =} "we chose" …car ce sont des actions au passé, donc il faut utiliser le prétérit.
Attention à la prononciation de certains mots comme "kept", "mould", "whether", et certains mots "transparents" comme "microorganisms",….
Il faut bien prononcer les "s" à la 3ème personne du singulier et après chaque mot au pluriel, exemple "that finds, "excludes", "which allows", "no colonies, ….
C'est très bien présenté et ton texte est bien écrit.
Potatoes
Cultural and social issues of the project:
We have chosen organic and non organic potatoes because nowadays we often eat this tuber. We are also interested in the conservation of organic and non-organic potatoes. We have noticed that the French are consuming more and more organic products.
In fact, 9 out of 10 French people consume organic products. Organic farming is a mode of production that finds its originality in the use of farming and livestock practices concerned with respecting natural balances. Thus, it excludes the use of synthetic chemicals, GMOs. We also found that the consumption of potatoes in France per year per person is 27.5 kg.
We therefore wanted to work on the cold sweetening of organic and non-organic potatoes which consists of storing the potatoes at low temperature (below 5 ° C), helps to limit weight loss, to control silver scab. and dartrose and 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 cold sweetening and a lower value (6 ° C), limiting the sweetening of senescence (limits aging of the potatoes) by keeping them at different temperatures (7-8°C / 20 ° C / 37 ° C).
We also decided to study the potato because it is a tuber on which we can perform many experiments such as the dosage of carbohydrates as well as the study of the microbial flora of the potato.
We will ask ourselves whether organic and non-organic potatoes can be stored in the same way according to their storage temperature.
To answer this question, we will first present our reflections as well as the process of developing our problem, then we will present our handling protocols and then we will presentation of our results.
Context and problematic:
We first thought of studying the difference between organic and non-organic carrots in order to determine which ones are better for health.
Subsequently, we found that studying cold sweetening on potatoes would be a better idea because potatoes are easier to grind than carrots.
We then chose to answer the following question:
Do organic and non-organic potatoes keep the same way according to their storage temperature?
For cold sweetening in organic and non-organic potatoes, we first thought that they had to be placed at different temperatures (7-8 ° C; 20 ° C; 37 ° C) several weeks before the experiments to be able to observe the effects of these temperatures on the different potatoes.
To study this we chose several experiments:
• Contact agar plate which allow us to observe if there are microorganisms on the potato slices stored at different temperatures.
• A TLC to determine which carbohydrates are present in organic and non-organic potatoes placed at different storage temperatures.
• Colony count on different growth media which allow us to calculate the concentration of microorganisms on an organic and a non-organic potato kept at the same temperature.
• A GOD-POD test which allows us to determine the glucose concentration in the different potatoes that we previously placed at different temperatures.
The purpose of this experiment is to observe the effect of temperatures on the amount of glucose present in potatoes and to determine whether glucose has been degraded at low temperatures.
To be able to carry out these experiments we started by washing the potatoes with a washing protocol.
-To start you have to wash your hands with an anti-bacterial soap so as not to transfer microorganisms from our hands to the potatoes.
-Then we washed the potatoes in cold water to remove the soil.
-Then we rub the potatoes to remove all the impurities.
-Finally we wiped the potatoes with a paper towel.
We started with contact agar plates which allow us to observe if there are microorganisms on the potato slices stored at different temperatures.
For this, after washing the potatoes, we cut each organic and non-organic potato from each storage temperature. Then, we placed the potato slice for 10 seconds on the contact agar plate, then we incubated them for 48 hours at 37°C. After 48 hours we looked at the results.
Results of contact agar plate:
We could see that on organic potatoes there were moulds that has grown on the agar plate. Whereas on non-organic potatoes no moulds had grown. And this result is the same for all storage temperatures.
-Results of others experiments:
TLC:
potatoes kept at 5 °C:
We can notice that the frontal ratio of the spots of the organic and non-organic potatoes stored at 5°C approach is equal to that of glucose. We can conclude that organic and non-organic potatoes contain glucose.
Potatoes kept at 20°C:
We can notice that the frontal ratios of organic and non-organic potatoes are close to those of fructose and glucose. It can therefore be concluded that organic and non-organic potatoes stored at 20 ° C have glucose and fructose.
Potatoes kept at 37°C:
We can notice that the frontal ratios of the spots of organic and non organic potatoes approach the frontal Ratio of fructose and maltose. We can conclude that organic and non-organic potatoes stored at 37 ° C contain fructose and maltose.
Conclusion:
We have seen 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.
Colony count on Slanetz: faecal streptococcus
Potatoes kept at 5°C:
We can observe that the colons are more numerous on the boxes of the organic potato. Faecal streptococci are more present on organic potatoes than on non-organic potatoes.
C (UFC; pomme de terre biologique)=(14/((1+0.1*0)*10-2))*1/1*10
=1,4.10^5UFC.mL-1
Potatoes kept at 20°C:
We can notice that the colonies are more numerous on the boxes of the organic potato. We can therefore conclude that faecal Streptococci are more numerous on organic potatoes than on non-organic potatoes.
Potatoes kept at 37°C:
We can notice that there are 0 faecal streptococci on Slanetz agars at 37°C. We can conclude that the colonies do not develop at 37°C.
Conclusion:
Slanetz agar allows the detection of faecal streptococci. It can be noted that there are more colonies on the Petri dish of organic potatoes than on the Petri dish of non-organic potatoes. At 37 ° C, no colony developed. At 20 ° C and 5 ° C, the concentration of UFC.mL-1 is higher on the boxes of the organic potato. So there are more faecal streptococci because manure is used for organic potatoes.
Total flora counts:
Potatoes kept at 5°C:
We calculated the content of microorganisms in an organic and a non-organic potatoes that were stored at 5 ° C. For organic potatoes, the content is 4.75.10^5 CFU / g and for non-organic potatoes, the content is 1.05.10^5 CFU / g. It can therefore be concluded that the organic potatoes contains slightly more microorganisms than the non-organic potatoes.
Potatoes kept at 20°C:
We were able to calculate the microorganism content of organic potatoes stored at 20 ° C, it is 1.7.10 ^ 5 CFU / g. But we could not calculate this content for non-organic potatoes because on the Petri dish there were less than 10 colonies.
Potatoes kept at 37°C:
We were able to calculate the microorganism content of the organic potatoes which is 1.06.10 ^ 6 CFU / g and that of the non-organic potatoes is 1.2.10 ^ 5 CFU / g. There are therefore 10x more microorganisms in the organic potatoes than in the non-organic potatoes.
Conclusion:
We can conclude that the PCA medium was used to count the total flora of the potatoes. We have observed that organic potatoes contains more microorganisms than non-organic ones. Regarding the storage temperatures of potatoes, we can say that those that were stored at 5 ° C and 20 ° C have about the same content of microorganisms, but those stored at 37 ° C a much higher microorganism content than others temperatures.
GOD-POD test:
C (glucose; standard) = 10mg / L
C (glucose; test) = (A test / A standard)* C (glucose; standard)
We can notice that the glucose concentration in potatoes is higher than in organic non-organic potatoes. We also see that the lower the storage temperature, the higher the glucose concentration in the potatoes.
General conclusion:
Through our experiments 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 prevents the growth of fecal streptococci. Organic and non-organic potatoes contain the same carbohydrates but the concentration varies depending on whether the potato is organic or non-organic and also depending on its 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.
To conclued, organic potatoes are not stored in the same way and the storage temperature also changes certain elements of the composition of the potato.
