I sent my piece on the pronunciation of these spices to the Maestro David Crystal and that erudite gentleman was kind enough to reply as follows:

Many thanks for your message. I’ve just had a look in the 15th edition of the English Pronouncing dictionary, 1997, and they recognize the alternative pronunciation of ‘cumin’ that you’ve heard. In fact they give three, in this order: ‘come in’, ‘coo-min’ and ‘queue-min’. So it does look as if this word is in the process of change. They don’t give an alternative for ‘turmeric’, though, so the change here must be more recent. There’s nothing Indian about this. There is always unpredictability about the pronunciation of words beginnig with cu- in English – compare ‘cup’ and ‘cure’, and with unfamiliar words it’s not surprising to find some vacillation. The same applies to tu- (‘tutor’ and ‘turn’).

David Crystal

His analysis of the Obama speech should be read by anyone with an interest in language, in oratory, in history, or in modern politics. It has already been extensively quoted in the Sunday Times and I (were I the minister for education) would distribute it for study to schools and universities.
You can find it if you click on to his blog on the link at the side of my page.