You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Effect of high-pressure treatment on biogenic amines formation in vacuum-packed trout flesh (Oncorhynchus mykiss). The effects of vacuum packaging followed by high pressure processing on the shelf-life of fillets of rainbow trout (Oncorhynchus mykiss) were examined. Samples were pressure-treated at 300 and 500 MPa and were stored at 3.5 and 12 °C for up to 28 days (control--0 MPa) and 42 or 70 days (pressure-treated; 12 and 3.5 °C resp.). The content of eight biogenic amines (putrescine, cadaverine, spermidine, spermine, histamine, tyramine, tryptamine and phenylethylamine) were determined. Putrescine, cadaverine and tyramine showed very good correspondence with the level of applied pressure and organoleptic properties. Samples of very good quality contained less than 10 mg/kg of each of these amines. Polyamines spermidine and spermine did not show statistically significant changes with the level of applied pressure and the time of storage. Tryptamine, phenylethylamine and histamine (with the single exception of a sample stored for 70 days) were not detected in pressure-treated samples kept at 3.5 °C.
{"Chemical": ["tyramine", "amines", "Tryptamine", "cadaverine", "spermine", "Putrescine", "phenylethylamine", "putrescine", "histamine", "Polyamines", "spermidine", "tryptamine"]}