The expression じゅわっと appears in the text of 佐賀のがばいばあちゃん in a scene where the protagonist, 昭広, steals some mandarins from somebody's backyard. He bites into one and that phrase pops up.
The full sentence is as follows:
p. 181, ch. 14
Maybe: "When I put it into my mouth, the sweet and sour juice burst into my mouth"?
I couldn't find a definition of じゅわっと in the dictionary which fits the sentence here. The dictionary says it has something that has to do with meat that is cooked to perfection, or something like that. However, I assume a mandarin is not meat. Perhaps it refers to the way the liquid bursts into your mouth with all the flavour. In context, it seems to suggest something strong and refreshing. He is very pleased with the flavour.
Please let me know the exact meaning of じゅわっと. Thanks.