Using ready-to-use MS medium, and put in Raypa AES-75 autoclave for 20 min at 121C according to the protocol. But it becomes yellow when it gets cold. Even tried with aluminum foil. What can be the reasons effecting the MS to become yellow? How can I change it??
Sugar caramelization might occur. Temperature of sucrose caramelization is around 160 oC, fructose can be caramelized at 110 oC so under normal autoclaving conditions it should not take place. Check your autoclave program and temperature sensor accuracy. Try to autoclave pure sucrose solution.
You should prepare oridnary receipt not ready to use. And you have to prepare trace elements separately and than sterlize it by filter sterlization.
Sugar caramelization might occur. Temperature of sucrose caramelization is around 160 oC, fructose can be caramelized at 110 oC so under normal autoclaving conditions it should not take place. Check your autoclave program and temperature sensor accuracy. Try to autoclave pure sucrose solution.
You may ensure that pH is around 5.6-5.8. Sometimes, acidic and alkaline pH may change the colour
I agree with Yuriy. In addition, there is another factor may be has effect , such as stay the medium inside autoclave for long time after autoclaving, convert the medium into yellow color due to the reasons that were mentioned above.
yes, i am also agree with the answer posted by Yuriy. Prolonged autoclaving can improves the sugar caramelization and may increases the final pH of the medium, which might leads to the softening of agar (agar does not solidify at higher pH).
@ Raja,
1. Autoclave of medium with sucrose will lower the medium pH. pH value of post-autoclave will significantly decrease if glucose or fructose is used (see below ref).
[https://books.google.com/books?id=55X_Wjct7f0C&pg=PA147&lpg=PA147&dq=pH+change+and+sucrose+autoclave&source=bl&ots=s4gFEgIgaZ&sig=e4semuKqrm2SZZNywc7o7MdZitU&hl=en&sa=X&ved=0ahUKEwiojKGhqqXLAhUV62MKHQfdDtEQ6AEIKjAB#v=onepage&q=pH%20change%20and%20sucrose%20autoclave&f=false].
2. Lower pH will decrease agar strength for gelling (see attachments 1 and 2).
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