Optimization of antioxidant and emulsifier combinations in model nutritional formula oil blends for peroxide quenching

Oxidation in nutritional formulas is challenging, commonly mitigated by antioxidants including ascorbyl palmitate and tocopherols. Increasing polyunsaturated fatty acids including arachidonic acid from M. alpina and docosahexaenoic acid from Schizochytrium can further exacerbate oxidation. However, increasing antioxidant levels is not always a solution due to ingredient solubility challenges, country specific regulations, and potential pro-oxidation concerns. Lecithin, an emulsifier commonly used in nutritional formulas, has been used to increase solubility of ascorbyl palmitate previously, potentially increasing antioxidant efficacy.

The goal of this study was to optimize ratios of ascorbyl palmitate, mixed tocopherols, and lecithin by monitoring their peroxide quenching potential within an oxidized oil blend model representative of lipids in infant formula.

A full factorial design was used with five levels of ascorbyl palmitate (0, 450, 1200, 2000, 3500 ppm oil), four levels of mixed tocopherols (0, 350, 550, 1000 ppm oil) and two levels of lecithin (0, 15 g/kg oil). Model systems were prepared with soy, high-oleic safflower, coconut, Schizochytrium spp. and M. alpina oils to mimic blends in infant formulations. The combined oils were heated and mixed vigorously to incorporate oxygen and generate peroxides. Oil was aliquoted, reheated (125°F), and 40 different ratios of antioxidants and lecithin were incorporated for 5 minutes.  Peroxide value was measured in initial oil blend and after antioxidant incorporation.

As expected, ascorbyl palmitate reduced peroxides dose dependently. Lecithin alone did not impact peroxide value; however, it improved the antioxidants’ ability to quench peroxides by ~60%. Mixed tocopherols, nor their interaction with lecithin or ascorbyl palmitate, did not significantly impact peroxide value.

This study highlights the potential for antioxidant and emulsifier mixtures to combat preliminary oxidation in highly susceptible oil blends in infant formula. Data from the current study will be utilized to select optimal compositions and monitor oxidation in nutritional formulas over shelf life.