Hello Everyone, during the completion of the research about edible coated strawberry.I should check microbial plate count using PDA and PCA. However the result of CFU for both coated and uncoated strawberry showed that PDA had higher CFU compare to PCA. Can anyone give the possible explanation for my results?
Dear Meilina,
PCA and PDA are used to make two different counts. You use PDA to detect yeast and mould and you use PCA to detect bacteria in general. As pH of both medium are different they tend to show different counts even if they come from the same sample.
One possible explanation is that all yeasts that could not grow at the "high" pH (around 7) of PCA are able to grow only on PDA (pH 3.5). Which would be very likely as fresh fruit tend to have a high count of yeasts and strawberries have a low pH.
It should be easy to verify this just by taking a look of at the microscope of some of your colonies just to make sure you have two different populations on each medium.
Good luck!
@ Phil Geis PCA is utilized as medium for total plate count, while PDA is utilized to count molds.
Dear Meilina,
PCA and PDA are used to make two different counts. You use PDA to detect yeast and mould and you use PCA to detect bacteria in general. As pH of both medium are different they tend to show different counts even if they come from the same sample.
One possible explanation is that all yeasts that could not grow at the "high" pH (around 7) of PCA are able to grow only on PDA (pH 3.5). Which would be very likely as fresh fruit tend to have a high count of yeasts and strawberries have a low pH.
It should be easy to verify this just by taking a look of at the microscope of some of your colonies just to make sure you have two different populations on each medium.
Good luck!
As Paola said, there is a pH difference between the media. FDA reports pH of strawberries is about that of PDA medium. However recovery from the fruit doesn't mean the bugs were growing on the fruit and plant growth conditions and fruit handling will affect what is recovered.
- Badges
- Science topic
- Similar topics
- Medicine
- Nutrition and Dietetics
- Nutritional Medicine
- Food Science