Final answer:
The text lacks details about the specific candles and soap used at the welcoming dinner for American POWs; thus no accurate ingredient can be inferred.
Step-by-step explanation:
The provided text does not contain specific information about the candles and soap used at a welcoming dinner for American POWs, nor does it mention ingredients. The text provided speaks of different events where food and gifts were offered, which suggests a historical context. Without more information on the specific time period or the event in question, it is impossible to accurately answer what the main ingredient of the candles and soap was at the welcoming dinner. Typically, historical soaps and candles may have been made of animal fat (tallow) or plant oils, but without the specific context, this remains an educated guess.