We propose a new test for the triplet majoron model by using neutrino bursts from supernova explosions. These pulses suffer scatterings on the cosmological majoron background. As a consequence, they get spread and their energy spectrum is changed with respect to the conventional expectation. We find that positive evidence of distinct neutrino pulses of all species corresponding to muon and tau-neutrinos heavier than 70 eV would rule out the model.