Characterization of lipid spray beads for delivery of glycine and tyrosine to early marine fish larvae

Lipid spray beads (LSB) composed singly or of mixtures of trilaurin, methyl palmitate (MP), menhaden stearine (MS), spermaceti and coconut oil were prepared and their performances were compared for delivering glycine and tyrosine to the early stages of fish larvae. Measures of performances of LSB included inclusion (IE), encapsulation (EE), retention (RE) and delivery efficiencies (DE) in addition to T50 (time to 50% retention) values. Tyrosine and both particulate and aqueous solutions of glycine were successfully incorporated within LSB using a melt-spray method, with incorporation efficiencies ranging from 81.0% to 91.1%. A maximum encapsulation efficiency of 21.0% was achieved for LSB composed of 100% MS with a core of particulate tyrosine. In order to modify their hardness, LSB containing particulate glycine were prepared with 100% MS with and without additions of coconut oil or spermaceti. Highest retention and delivery efficiencies were achieved by LSB composed of 100% MS, indicating that substitution of MS with coconut oil or spermaceti had no beneficial effects on LSB performance. LSB composed of 100% MS had a retention efficiency of 34% after I h of suspension, corresponding to a delivery efficiency of 0.523 mg glycine 10 mg(-1) lipid. LSB composed of 75% MS+25% spermaceti containing aqueous glycine had a significantly higher retention efficiency compared to that of LSB containing particulate glycine (P<0.05, Tukey's HSD). Furthermore, delivery efficiencies indicated that LSB (75% MS+25% spermaceti) containing an aqueous core delivered significantly higher concentrations of glycine (0.291 mg 10 mg(-1) lipid after I h suspension in water) compared to LSB with a core of particulate glycine. Tyrosine was better retained by LSB compared with glycine, probably due to differences in the water solubilities of these two amino acids. LSB (100% MS) containing 6.2% and 21.0% (w/w) of tyrosine had identical retention efficiencies indicating that higher tyrosine concentrations did not result in higher percent leaching rates. LSB (100% MS) containing 21.0% tyrosine had a T50 value of 654 min with a delivery efficiency of 1.10 mg tyrosine 10 mg(-1) lipid. Visual observations indicated that LSB composed of 50% MS + 50% coconut oil or 100% MS can effectively deliver nutrients to 3-day-old clownfish, Amphiprion percula, larvae. Particles in fecal strands and in guts of larvae were compacted, confirming the ability of larvae to form pellets from digested particles. Release of Poly-red was evident by a pink coloration in the lumen of the hindgut. LSB show promising potential for delivery of dietary amino acids to marine fish larvae. (C) 2004 Elsevier B.V. All rights reserved.