3.1. Yield of astaxanthin and production of astaxanthin in alginate-chitosan beads
The ethanol extracted astaxanthin yield (24.66 ± 2.91 mg extract/g shrimp shell) was derived in the form of orange-red paste containing 1.70 ± 0.05 mg astaxanthin/g extract (average of three independent extractions). The production of alginate-chitosan beads by ultrasonic atomizer resulted in uniform beads (Table 1). No significant differences were found in weight and size of the beads from all treatments which had an average weight and diameter of 55.47 mg and 4.23 mm, respectively. However, it was reported that the bead size became bigger when the alginate concentration was increased (Chan, 2011) as well as the increasing concentration of chitosan (Anal et al., 2003 and Lim et al., 1997). The appearance of beads with uniform rounded outer surface found in this study is attributed to the advantage of employing ultrasonic atomizer instead of a conventional syringe. Besides, the benefits include atomization at any flow rate and non-clogging for reliable performance that can overcome the problem of obtaining beads with different size. The application of ultrasonic atomizer was successfully reported for fish oil encapsulation (Klaypradit & Huang, 2008).