Can alkaline batteries withstand reverse current transients?
Even an amp for a few milliseconds isn't going to harm them at all and a mA for a few seconds isn't going to much either, you'd need to be pushing several watts for quite some time before you would experience any real problems (you can always swap out the alkalines for rechargeables if you are still worried, there are NiZn cells that have the same voltage as alkalines but they're hard to find)