A friend and I were curious about this particular claim, and we each did the following with our partner after getting them on board with it : Every 48 hours, the male in the relationship (both were hetero couples) would receive a blowjob in the evening. Two hours before the blowjob, the male would flip a coin and either drink a small carton of pineapple juice or not based on the result. The woman would then try to indentify if the pineapple flavor was present in the semen. This was done ten times over 20 days for both couples.

At the end, both women had 100% accuracy in indentifying the days when pineapple had been consumed. It’s only n=2, but I have to believe theres some truth to the claim that pineapple is detectable in semen.