Typically adding quotes around the word does it. i just tried that and it does return my quoted string - but it also matches on each word individually.
So my guess is the quotes don't work - the search engine just matches each word as a separate entity.
Try this:
In your Google search window type ["<word or string of words>" site:www.winemakingtalk.com]
Put your string in quotes, and leave a space between the last quotation mark and the word "site".