| In the present study, the potential of low-melting point lipids, namely methyl palmitate (MP) and menhaden stearine (MS), were studied for delivery of water-soluble materials to fish larvae.; Addition of the solid emulsifier, sorbitan monopalmitate (SMP) resulted in higher RE compared to the liquid emulsifier sorbitan sesquioleate (SSO). Additions of SMP were found to have a positive effect on the stability of lipid spray beads (LSB) at concentrations >10% (w/w) of lipid. LSB were shown to retain riboflavin with the highest RE when the lipid matrix was composed of a mixture of MP+10% SMP+10% ethyl cellulose (w/w). Use of MP facilitated digestive breakdown of LSB by larvae of zebrafish, Brachydanio rerio , and glowlight tetra, Hemigrammus erythrozonus, as indicated by release of riboflavin from ingested LSB.; LSB composed of MS performed better than LSB composed of MP when particulate glycine was incorporated within LSB. Highest retention efficiencies (RE) and delivery efficiencies (DE) were achieved by LSB composed of 100% MS. RE and DE of LSB were further improved when glycine was encapsulated as aqueous droplets rather than in a particulate form. The overall performance of LSB containing tyrosine showed that nutrients with similar water-solubilities to tyrosine can be very effectively delivered to early fish larvae. Visual observation indicated that LSB composed of 100% MS were broken down by larvae of clownfish, Amphiprion percula.; Zein-bound particles (ZBP) were not efficient in delivering riboflavin to fish larvae due to high leaching rates. In an attempt to improve ZBP, we developed complex particles (CP) containing LSB incorporated in a dietary mixture bound by zein, to obtain a single particle type. The potential of LSB for delivery of free amino acids (FAA) was evaluated when LSB were incorporated within CP. RE and DE for tyrosine were significantly greater than those for alanine, glycine and serine. There was a significant inverse correlation between RE for FAA and their solubilities where FAA with low solubilites resulted in higher RE. Develoment of CP with high RE and DE for amino acids is an important step towards formulating a diet to allow early weaning of fish larvae onto artificial diets. |
