Crawling advice

I have around 7000 new additional products that I want to be available on my store to purchase, but dont want them crawled by google. There will be around 50 sub categories under one main category.
Is the only way to create in robots.txt a dissalow for each category/ and is it reliable …or is there a better way.

If you use the category in the product’s SEO url, that should work. I can’t think of any other way.