Green apples on a burger?

The listing of green apples on the “Mainah” at the Mainely Burgers food truck in Portland took me by surprise.

At first, I couldn’t wrap my mind around apples and ground beef together. But then I saw that the Mainah ($7) also came with cheddar cheese, sauteed onions, bacon and maple mayonnaise. So I figured there was enough other stuff to hide the apples.

But the apples didn’t need to hide. They were cut razor-thin, so they had a texture similar to cabbage, and went really well with the burger and other toppings. The meat itself was thick and juicy.

With food trucks blossoming around Portland this summer, it’s fun to see how each one tries to stand out. The focus of the Mainely Burgers truck is on innovative gourmet burger toppings, high-quality ground beef and outstanding buns.

Buns are usually an afterthought to a hamburger with me, but the bun on the Mainah was a work of bakery art. It was big, light, fluffy and perfect for catching and containing the juice from the burger and all the other drippings that melted cheese and mayo can create. I also liked the way my burger was half-wrapped in wax paper and served in a paper basket, like I was at some 1950s drive-in.

I had an order of hot and crisp hand-cut fries for $3.50 to accompany my burger. They were big enough to share — but I didn’t.

The day I visited Mainely Burgers, the truck was in a parking lot near the sidewalk at the corner of Congress and Pearl streets in Portland, across from the fire station. Other days it’s down on St. John Street, and the owners say people should check Facebook for daily locations. They have another mobile eatery that’s usually at Scarborough Beach State Park on summer days.

Other burgers being served when I went included “The Beast” with cheddar cheese, sauteed onions, bacon, barbecue sauce and pickles; the “El Classico,” featuring American cheese, pickles, lettuce, tomato and house sauce; and the “Tortas,” with Swiss cheese, sauteed mushrooms, lettuce, tomato and house sauce. They ranged in price from $5 to $7.

There also are hot dogs on the menu, but it’s mainly a burger truck.

Which, on a summer day, is sometimes exactly what one is looking for.

The staff of GO anonymously samples meals for about $10.