It is a good question. However, this is a serious question. PUT is one of the bulk chemicals that have been tested for pre-and postharvest.So far, there are still no exact reports for its limit residual permossible. At least I have not seen it so far. Nevertheless, here is a discribnation from wikipedia, https://en.wikipedia.org/wiki/Putrescine. Normally, the pre- or postharvest treatment is around 10 to 100 ppm. So you can try to analyse the residual after treatments.

Dietary PAs from plant origin are considered very important for human nutrition and health because they contain relatively high amounts of Put and/or Spd, which are major sources of PAs to the body pool. Some of the health-beneficial effects of dietary PAs in humans are related to protection against oxidative stress, maintenance of gut integrity, modulation of inflammation and immune functions, among others. It is well known that PAs act in the control of relevant human pathologies including cancer, immunological, neurological and gastrointestinal diseases. In general, it seems that high PA-containing diets are beneficial for cell growth (i.e. in infants), whereas low PA-containing diets are beneficial for avoiding unwanted high rates of cell proliferation (i.e. tumor growth).

https://www.frontiersin.org/research-topics/7767/polyamines-in-plant-biotechnology-food-nutrition-and-human-health