Lupa is quietly grateful for it, although he's not acknowledging the flinch happened at the moment. This stranger is... kind. Probably. Lupa likes the new word, even if a part of him does not know how to relax and trust in kindness.

"I had not tasted sweet in the Junkyard. There were only rations, moldy rolls and rancid gravy. The rations tasted very similar to Oran Berries."

How does Lupa know that? Well, if mold and rancid still count as foodstuffs... why would someone balk at Berries that are supposed to taste bad?