Mosr often, they are called pressurized portafilters. They are found on a lot of the lower end pump machines. Saeco, Starbuck's Barista (made by Saeco), Solis SL70/90 and others.
What this does is: as pressure in the portafilter builds and when it reaches a predetermined pressure, a spring in the portafilter opens and forces the espresso out a pin hole(s) opening. This forces foaming of the espresso and they call it crema enhancer. I've used both and personally think the "enhanced" crema takes away from the taste of the espresso.
When I first got my Isomac Tea, I used fresh, home roast beans and got more crema from it than I ever did with enhanced types - even using the same fresh/home roasted beans. Of course, the shot was much better and really isn't fair to compare apples to oranges, or in this case, lower end machines to high end machines. It is however, my experiences so I pass them on for whatever they are worth.
Symbols: = New Posts since your last visit = No New Posts since last visit = Newest post
Forum Rules: No profanity, illegal acts or personal attacks will be tolerated in these discussion boards. No commercial posting of any nature will be tolerated; only private sales by private individuals, in the "Buy and Sell" forum. No cross posting allowed - do not post your topic to more than one forum, nor repost a topic to the same forum. Who Can Read The Forum? Anyone can read posts in these discussion boards. Who Can Post New Topics? Any registered CoffeeGeek member can post new topics. Who Can Post Replies? Any registered CoffeeGeek member can post replies. Can Photos be posted? Anyone can post photos in their new topics or replies. Who can change or delete posts? Any CoffeeGeek member can edit their own posts. Only moderators can delete posts. Probationary Period: If you are a new signup for CoffeeGeek, you cannot promote, endorse, criticise or otherwise post an unsolicited endorsement for any company, product or service in your first five postings.