Studi disolusi bromelain hasil pemurnian parsial dari bonggol nanas (ananas comosus [l.] merr) terenkapsulasi pada kitosan-guar gum serta uji aktivitasnya sebagai antiplatelet = Dissolution study of bromelain resulting from partial purification of pineapple stem (ananas comosus [l.] merr) encapsulated in chitosan-guar gum and its activity test as an antiplatelet