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UBC Theses and Dissertations

Optimizing the loading of vitamin A and vitamin D into re-assembled casein micelles and investigating the effect of micellar complexation on vitamin D stability Loewen, Anisa Joy


Food products may be fortified with vitamins A and D as public health intervention strategies. However, vitamin instability is a problem during storage before and after addition to foods. Re-assembled casein micelles (rCM) are reported to be effective carriers of hydrophobic compounds providing enhanced stability. The aim of this research was to form rCM with high loading of vitamin A palmitate (VA) or vitamin D₃ (VD). The protection given to VD by rCM was compared to that given by the controls composed of the re-assembly components not in micellar form, and to commercial vitamin products (CWS D₃, AD premix). Stability was investigated during storage of dry powders and of fortified skim milk exposed to light. Response surface methodology was employed to ascertain the influence of phosphate, citrate and calcium on vitamin loading during CM re-assembly, and to identify optimal vitamin loading conditions. Average optimal VD loading of 14.0 or 15.1 mg VD/g casein was found at 4.9 or 10.5 mM phosphate, 4.0 mM citrate and 26.1 mM calcium, respectively. VA loading was optimal at 9.7 mM phosphate, 5.5 mM citrate and 30.0 mM calcium, resulting in 14.7 mg VA/g casein. Significantly more vitamin was retained in VD-rCM powders than control powders during storage at 37°C and 75% relative humidity for 48 and 72 hours. Additionally, loss of VD was not significantly different in VD-rCM powders compared to CWS D₃ during storage at 37°C and 75% relative humidity. Significantly more VD was retained in VD-rCM powders than control powders when stored at ambient temperature and humidity for up to 42 days. Retention of VD in skim milk fortified using different formulations and exposed to light for 21 days conformed to the following order: CWS D₃ > VD-rCM L, CD > AD premix. In conclusion, response surface methodology was an effective tool to optimize vitamin loading of rCM. Stability of VD was improved by incorporation into rCM for some storage conditions. Protection may depend on the physical state of the VD-rCM and on the applied stress.

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Attribution-NonCommercial-NoDerivs 2.5 Canada