Why should someone who is using food grade agar to grow cultures switch to bacteriological grade agar?
Take care when using food grade agar for bacteriological purposes. Many food grade agars are produced with gracilaria or gelidiella seaweed’s and the gel strength of food-grade agar that’s produced is between 300 and 500 gms/cm2. What does that mean?
The real problem is the gelling temperature of food-grade agar, that is 40° – 44° Celsius. High-quality bacteriological grade agar MUST be extracted from selected gelidium sesquipedalis seaweed’s (not gracilaria or gelidiella seaweed’s). This requirement gives bacteriological grade agar a gelling temperature of 34° – 35.5 Celsius.
Agar is a colloidal substance, it is insoluble in cold water, but soluble in boiling water. When cooled to 34° – 43°C, it forms a firm gel which does not melt again below 85°C.
Our bacteriological grade agar has a gel strength of 920 gms/cm2
Important Factors for Bacteriological Grade Agar
– gel strength that must be over 800 gr/cm2
– transparencies must be lower than 10 NTU but top qualities agar are even lower than 5 NTU
– divalent captions that must not be higher than 1.000 PP
To view The Certificate of Analysis for our Bacteriological Grade Agar, please click here