Influence of salt addition and freezing-thawing on particle size and zeta potential of nano-chitosan

Abstract Antibacterial properties of nano-chitosan used for fish preservation would achieve optimum effect when combined with cooling. Applying nano-chitosan incorporated in ice can reduce the cooling cost of conventional fish industry. On the other hand, during fish handling, nano-chitosan has a high probability to be contaminated by salt in seawater. This study was aimed to test the effect of salt and freezing-thawing on nano-chitosan antibacterial activity. Nano-chitosan was prepared using ionic gelation and polyelectrolyte complex methods. NaCl (3%m/v) was added into nano-chitosan solutions to evaluate the effect of salt. Chitosan solution in diluted acetic acid was also tested as blank. The effect of freezing was undertaken by placing nano-chitosan and chitosan solution in the freezer until the solutions were completely frozen and then thawing the frozen solution in ambient temperature. The addition of salt not only reduced the particle size but also reduced zeta potential due to the possible neutralization. It also might reduce its antibacterial activity. Freezing effect increased particle size because low temperature triggered particle agglomeration but it did not show any changes in zeta potential. The result of this preliminary study indicated that nano-chitosan ice would give more benefit as fish preservative compared to plain ice.