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Appréciation
Concernant la présentation orale.
La durée est trop courte (4:03 mins),
Il a des mots mal prononcés dans certaines phrases comme "which is quiet?? question" et quelques erreurs comme "what make it up =} "what it is composed of"
"we place the plate in the tank" =} "we placed" the plate…car c'est une action au passé, donc il faut utiliser le prétérit.
Attention à la prononciation de certains mots comme "theme", "thought", "able", et certains mots "transparents" comme "consequence", "basic", "current"….
Il faut bien prononcer les "s" à la 3ème personne du singulier et après chaque mot au pluriel, exemple "conditions
C'est assez bien présenté et ton texte est bien écrit.
Cocoa powder
The beginning
First of all our group chose the hydroalcoholic gel but another group we already took. So we looked at cocoa because it's the food, interesting and understand why it is time used in the world. Moreover, one of the member had two cocoa powders of different dates, so we subject and then we started to use research on cocoa to understand how it works. We made a mental map with a all the different questions to be addressed.
We found answer and then asked questions about its conservation. So we started to look for matérials which are hermetic glass and metal boxes which will be tested shelters away from heat, light and humidity ( = darkness ) and the opposite to know their preservation and which best suited.
- Then we have two cocoa from 2015 and 2021 to know the difference between is in "expiration" and the other in "use" and to know if they have the same consevation.
- What use the goal the problematic : What will be the consequences if we don't respect the condition of preservation and conservation for cocoa powder ?
Research experience
To answer we have made experiments on microbiological and biotechnological tp develop our answer to the problematic.
First part of the PTA :
- A Thin - Layer - Liquid Chromatography
- A colony count in the mass on PCA
- A gram staining
- The flag technique
- Isolation TS Agar medium
Second part of the PTA
- A protein extraction
- The water content
- IMC
- Colorimetric for the proteins and the carbohydrates
- A TLC ( Thin - Layer - Liquid Chromatography )
- We made the TLC ( Thin - Layer - Liquid Chromatography ) on four plates of silica gel two for 2015 and two for 2021. We carried out the procedure using the solvent, the deposits while respecting safety. We used the molisch reagent ( = developer ) to determine which carbohydrates were in the cocoa powder. This given us mixed res
2 The résult of all the experiments
- TLC : Brown masses are observed at the level of the front line which perhaps characterize the cocoa particles which have followed the migration current because the molecules are too large to adhere to the plate and therefore to migrate correctly.
- A colony count in the mass on PCA : We found contaminants that came from the students walking near the pca and we found colonies not as we wanted. Cocoa powder has no microorganism.
- A gram staining : We then made grams in order to know the strains of different colonies that we had. It has been observed that particles therefore have no conclusive results for the type of bacteria that could be found.
- Isolation TS Agar Medium : To check for the presence of pure strains, isolates were made on TS for the two cocoas from the suspension initial. Almost nothing has grown on the TS, if only a small white colony, nothing else … But we think that to be expected to grow, cocoa should be liquid.
- Water content : Strangely enough, we have had incoherent results. We wanted to do it again but we didn't have enough time.
Conclusion :
To conclude the problem is the powder is well stored in airtight boxes such as metal and glass away from heat and humidity in a dark place.
For the experiments that of 2015 and 2021 have the same conservations because they have the same proteins and the water content is the same in the 2 cases. This proves that even if the cocoa has expired, it can still be stored.