"I want them alive, and unspoiled."

[William Cloud Hicklin]

Difficult to tell, since while Tolkien would have been well aware of the original meaning of "spoil" (loot), there's no reason to think that PBJ were, so in the movie-universe "not eaten" might have been intended.

spoil (v.)
c. 1300, "to strip (someone) of clothes, strip a slain enemy," from Old French espillier "to strip, plunder, pillage," from Latin spoliare "to strip, uncover, lay bare; strip of clothing, rob, plunder, pillage," from spolia, plural of spolium "arms taken from an enemy, booty;" originally "hide, skin stripped from a killed animal," from Proto-Italic *spolio- "skin, hide," from PIE *spol-yo-, probably from a root *spel- (1) "to split, to break off" (see spill (v.)) on the notion of "what is split off."

From late 14c. in English as "strip with violence, rob, pillage, plunder, dispossess; impoverish with excessive taxation." Used c. 1400 as the verb to describe Christ's harrowing of Hell. Sense of "destroy, ruin, damage so as to render useless" is from 1560s; that of "to over-indulge" (a child, etc.) is from 1640s (implied in spoiled). Intransitive sense of "become tainted, go bad, lose freshness" is from 1690s.

In the book,
"Why don't we search them and find out? We might find something we can use ourselves."
"That's a very interesting remark," sneered a voice, softer than the others but more evil. "I may have to report that. The prisoners are NOT to be searched or plundered: those are my orders."
"And mine too," said the deep voice. "Alive and as captured, no spoiling. That's my orders."

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"In addition to unspoiled simply not being used in English to refer to spoils of war or plunder,"

Um, no.

unspoiled (adj.)
c. 1500, "not plundered," from un- (1) "not" + past participle of spoil (v.). Meaning "not deteriorated" is attested from 1732. A verb unspoil is attested from c. 1400, but it meant "despoil."