Applying for a postdoc with degree from different fields I have a master and bachelor degree in Aerospace engineering. Master degree was from the most prestigious institute in my country (India). 

Then I moved on to my Ph.D., but this time into a different field. Physical Chemistry. Particularly because I wanted to do fundamental science rather than engineering. I am doing pretty good in my Ph.D. (in terms of publication and progress)

Will having a degree from different fields be a trouble when I apply for a postdoc (in Physical chemistry) in top universities (like Cambridge or Princeton)? Also will this affect me when I try for a tenure track position?
In my experience, people are much more interested in your publications and research specialty then your previous degrees.

A previous degree in a separate field is more of an asset that can open new doors; you are a credible person for any possible cooperation between your current and previous field (about which I know little; maybe creating or investigating materials that might be of use in aerospace engineering). Interdisciplinary work is difficult unless someone knows both of the fields and understands their concerns and languages.

I suppose someone might see a positive or negative signal in you having changed a field (learning an entirely new field in your PhD studies is certainly impressive, or maybe you lack some fundamentals in your new field, and almost certainly you stand out from among many other candidates whose master's degree is in a more usual field), but this could go either way and depends on the person doing the hiring. I would not be worried.