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The use of natural pigments such as lobster carotenoids in fish feed formulations offers advantages over the use of the synthetic alternatives. Microencapsulation of the pigments, with or without the addition of antioxidants to the formulation, may be of benefit in terms of stabilizing pigment colour. In the present study, lobster carotenoids were extracted from lobster shell into petroleum ether and microencapsulated by phase separation and salt coacervation within (poly vinyl alcohol) and poly(vinyl alcohol)/poly(D,L-lactic acid) membranes. Spherical microcapsules, with smooth, thin and resilient membranes were obtained with mean diameters ranging from 50 to 150 microns, depending on the membrane material, and source of pigment. The microcapsules were pink-orange in colour, and colour stability was followed spectrophotometrically. Enhanced stability was observed in both membrane materials, in comparison to the non-encapsulated control. Rates of discoloration were determined under a variety of storage conditions, including the absence of light, reduced temperatures and under nitrogen atmosphere. The best stability of lobster carotenoids was observed under a nitrogen atmosphere within PVA/PLA membranes, representing an 11-fold enhancement of pigment stability in comparison to the controls. Under ambient conditions, the enhancement in pigment stability was approximately 6-fold. The optimum concentration of PVA during microencapsulation was 3-4%, and the microencapsulated pigments appeared most stable under acidic conditions. The rate of discoloration appeared independent of pigment concentration.

Co-guanidine membranes were shown to form intact, ionically complexed membranes on alginate beads, serving as an alternative to the commonly used polymers, poly-L-lysine and chitosan. DNA was encapsulated and membrane thickness, the level of DNA protection from nuclease diffusion and the degree of DNA-complexation with co-guanidine membranes were all shown to be dependent on both polymer concentration and coating time. The highest level of DNAse exclusion was possible within beads coated with a polymer concentration of 5 mg/ml. Recovery of double-stranded DNA after nuclease exposure for 60 min reached 90% of that initially encapsulated. The molecular weight cut-off for these co-guanidine membranes was approximately 31 kDa, sufficient to exclude extracapsular nuclease. The level of DNA protection was found to be comparable to high molecular weight poly-L-lysine membranes (197.1 kDa). Intracapsular DNA was accessible to the carcinogen ethidium bromide, which showed a 4-fold increase in uptake in uncoated beads and 2-fold uptake in co-guanidine coated beads compared to beads lacking in DNA. Co-guanidine membranes coating alginate result in a molecular weight cut-off sufficient to retain DNA and exclude 31 kDa DNAse, while providing access to the low molecular weight carcinogen, ethidium bromide.

The use of natural pigments such as lobster carotenoids in fish feed formulations offers advantages over the use of the synthetic alternatives. Microencapsulation of the pigments, with or without the addition of antioxidants to the formulation, may be of benefit in terms of stabilizing pigment colour. In the present study, lobster carotenoids were extracted from lobster shell into petroleum ether and microencapsulated by phase separation and salt coacervation within (poly vinyl alcohol) and poly(vinyl alcohol)/poly(D,L-lactic acid) membranes. Spherical microcapsules, with smooth, thin and resilient membranes were obtained with mean diameters ranging from 50 to 150 microns, depending on the membrane material, and source of pigment. The microcapsules were pink-orange in colour, and colour stability was followed spectrophotometrically. Enhanced stability was observed in both membrane materials, in comparison to the non-encapsulated control. Rates of discoloration were determined under a variety of storage conditions, including the absence of light, reduced temperatures and under nitrogen atmosphere. The best stability of lobster carotenoids was observed under a nitrogen atmosphere within PVA/PLA membranes, representing an 11-fold enhancement of pigment stability in comparison to the controls. Under ambient conditions, the enhancement in pigment stability was approximately 6-fold. The optimum concentration of PVA during microencapsulation was 3-4%, and the microencapsulated pigments appeared most stable under acidic conditions. The rate of discoloration appeared independent of pigment concentration.