It won't show up straight away. Google will cache your old info for a period of time before it will index your new title and description. It might take a week or a month before your new title and description shows in Google.
As a general rule, be "careful" when updating titles and descriptions. The google bot crawls your website once a day or maybe even once a week (depending on fresh) content.
Keep in mind that Google will also rank you for keywords in the title and description and this takes time! So, by changing it frequently will only hurt you in the long run.
You can call on google bot to re-crawl your website in Webamster tools.
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