Are these actual words in Swedish, or, as I suspect, Swedish-sounding gibberish?
It’s mock swedish (or as you put it “Swedish sounding gibberish”). They take typical vowel (and consonant I guess but it seems tor evolve aorund vowel sounds) sounds of Swedish and screw with it from there. Though I wouldn’t be surprised if they put a couple of actual Swedish words in there occasionally. Not that it’s hard to speak Swedish… just learn German and speak it while fully submerged in water! 
It may be mock Swedish, but you can tell Google to present its results in the chef’s dialect.
In high school a Swedish foreign exchange student said Swedish Chef sounded Norwegian.
EDIT (because I know someone will say something): He didn’t mean that he was actually speaking Norwegian; just that he sounded Norwegian.
Wikipedia says it’s gibberish which is what I’ve read in previous threads (including responses from some actual Swedes):
For fun on a slow day, run some of the latest email directives from your boss through the Swedish Chef Dialectizer and read them out loud.
Um bork bork bork.
We’ve been watching the old Muppet Show (we’re now midway through Season Two) and I’m surprised at how much of the Swedish Chef’s dialogue (well, monologue, mostly) is…English! He does a lot of “bord de bork de bork bork the chicken go poof!” kind of stuff.
A Swedish Doper once told us that in Sweden, the character is called “The Norwegian Chef”.
Swedglish?
My 9th grade year, I had to do a presentation in Science class on Nutrition. Mr. Anklam, being awesome, would give bonus points if your presentation was done with flair. He suggested a chicken costume.
Well, being desperate for points, I did up my little signs on the nutritional value of a bowl of cereal (copied that morning from the side of the cereal box), brought some cereal, and some milk.
For my presentation, I ducked down behind his desk, sang the “Swedish Chef Song” and then popped up and did my best Swedish Chef imitation. Cereal flying, milk EVERYWHERE. Then a brief run down of the “witamoonsa, bery bery gooda, jaaaa!”.
Mr. Anklam had tears running down his face, he was laughing so hard. First and only A for me in the class. Hehehehe
There was an episode where they had a Swedish guest. It was a long time ago and I’m going by memory but I recall that when someone asked the guest what the chef was saying the response was “I don’t know, I don’t speak mock Swedish”.
There’s an occassional real word, like “Ya” “mit” thrown in there, but yes, it’s 90%+ mock Swedish.
In the context of the Muppet Show universe, it is officially Mock Swedish. But it’s not his native tongue…
From Muppet Wiki.
Remarkable how often we end up talking about The Muppet Show. Why did it go away?
A Swedish guy once told me it was gibberish, but it was Swedish gibberish.
That’s actually the segment I was remembering. I had it totally wrong.
All the good things end too early. But we get 127 seasons of The Flavor of Love with 32 spinoffs. Go figure.
That’s basically the same thing as the commercial for the 1988 Swedish Chef cereal, Croonchy Stars (Wiki link).
Youtube link to commercial Ooh…scroompshious.
Wow, if I had known that stuff existed, I would have BEGGED my mother for it. Dang it.
Of course, neither “ya”, nor “mit” are actual swedish words…
Hey, am I completely crazy, or is the Swedish chef pretty much ripped off from a character that Arte Johnson used to do on Laugh-In? This has been bugging me for 30+ years 
Or Swenglish.