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Chitosan is known as an antibacterial agent. The effective surface area ratio of chitosan can be increased by modification into nanoparticles. Nano-chitosan can be prepared with several simple methods, i.e. precipitation, ionic gelation, or the polyelectrolyte complex method. This study compared these three methods in terms of the targeted product characteristics, i.e. stability of the average nanoparticle size as well as the colloidal dispersion, and the antibacterial characteristics. All three methods resulted in nanoparticle formation, but in the precipitation method significant zeta potential reduction was observed due to the presence of negative ions from the alkali that neutralized the chitosan amine group. The ionic gelation method yielded higher zeta potential and higher inhibition of bacterial growth than those yielded by the polyelectrolyte complex method. Ionic gelation and the polyelectrolyte complex method resulted in much better colloidal dispersion stability than the precipitation method, where a significant particle size increase was observed after one week of storage. This result indicates that both ionic gelation and the polyelectrolyte complex method can be used for forming nano-chitosan for the purpose of food preservation. However, for fishery products it is advisable to use the polyelectrolyte complex method because the TPP usually used in ionic gelation is not allowed to be applied to fish.

The aqueous dispersion of nanochitosan was prepared by polyelectrolyte complex (PEC) method with various mixing ratios of chitosan and polyanions, i.e., chitosan-glucomannan, chitosan-hyaluronic acid, and chitosan-Arabic gum. The formation of nanochitosan was carried out by adding the polyanion solution dropwise into the acid solution of chitosan. The study aimed to determine the best polyanion among the variations tested in this study, concerning the targeted particle size and the stability of the dispersion over time. Particle size distribution was observed by Particle Size Analyzer (PSA). The result indicated that Arabic gum gave the smallest average particle size, i.e. 192.5 nm, at a chitosan/polyanion mass ratio of 3:1 and pH value of 4.

Chitosan utilization as a preservative agent for freshly caught fish has been studied intensively during the last ten years in Indonesia, but the effort was concentrated more on ponds-raised fresh water fish. In this paper we report our preliminary results of a study on using chitosan in the form of nanoparticle (nano-chitosan) to improve the shelf life of freshly caught wild young yellowfin tuna (YFT- Thunnus albacares, Bonnaterre 1788). Pharmaceutical grade chitosan was dissolved in 0.2 mM aqueous acetic acid and aqueous ammonium hydroxide was added to reach a certain value of pH at which 1% concentration of nano-chitosan particles was obtained. The YFT samples were immersed for 30 min in aqueous dispersion of nano-chitosan, and incubated afterwards at two different temperature settings (4 °C and 28 °C). The fish deterioration was measured in terms of Total Volatile Base (TVB) and bacterial Total Plate Count (TPC), with supporting data taken including organoleptic assessment, pH and water content. The nano-chitosan did not seem to decrease the number of bacteria. However, the TVB data indicated that nano-chitosan treatment significantly suppressed the bacteria activity and the effect was more pronounced at 28 °C.

The polyelectrolyte complexes (PECs) of chitosan with various polysaccharides such as alginate, carrageenan, Arabic gum, carboxymethylcellulose (CMC), pectin, and glucomannan were prepared and characterized. The complexation was performed by addition of polysaccharide solution as crosslinking agent into chitosan solution (0.01% and 2 %) under magnetic stirring. The size of the obtained modified chitosan was analyzed by Particle Size Analyzer (PSA). The turbidity and pH were measured to observe the stability of the modified chitosan during the storage. The stability of the complexes was investigated at room temperature (37°C) for 3 weeks. The existence of glucomannan and arabic gum resulted PECs when it reacted with the chitosan solution using ratio 1:1. The changed crosslinker resulted a hydrogel after it blended. The obtained PECs could be affected by the ratio between chitosan and polysaccharide and the molecular weight of both polymers. The crosslinker concentration gave a significantly influenced the ...

Nano-chitosan has antibacterial activity and can be used as fish preservative. Acetic acid concentration of 1% is commonly used to produce nano-chitosan but it affected consumer acceptance because of its acidity. This study aimed to reduce the concentration of acetic acid and observed its effects on particle size, pH, and bacterial growth inhibition activity. Besides, it was also observed the effect of nano-chitosan with acetic acid concentration reduction on total bacteria and sensory value when applied on tilapia fillets. The results showed that the higher concentration of acetic acid resulted smaller particle size of chitosan and higher bacterial growth inhibition. The similar trend was also shown by acetic acid solution in same concentration. However, the bacterial inhibition zone of nano-chitosan solution was higher than acetic acid solution for each variation of acetic acid concentrations. This was evidenced by the observation of the clear zone formation of Gram positive and negative bacteria culture grown on nutrient agar. The optimum acetic acid concentration in nano-chitosan production was 0.43% because it was able to inhibit the growth of bacteria on the tilapia fillet and resulted in good consumer acceptance even when tilapia fillet was soaked up to 25 minutes in the nano-chitosan solution.

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.

Nano-chitosan was tested as a novel preservation agent for fresh tilapia fish ( Oreochromissp ). The fish samples were immersed in 0.6% nano-chitosan for 30 minutes and were kept in storage at room temperature, low temperature (10-15 o C), and very low temperature (2-7 o C). In room temperature, nano-chitosan did not exhibit significant preservative effect to inhibit the growth of microbes to be compared to sample without nano-chitosan treatment and kept in room temperature (control). However at lower temperature, a significant difference was observed in term of decreasing fish deterioration rate for the nano-chitosan treated samples to be compared to control. The rate of deterioration was quantified using three parameter logistic model for objective comparison among treatments, based on measured parameters (total volatile base and total plate count).