Controlled Release of Antioxidants via Biodegradable Polymer Films into Milk and Dry Milk Products
van Aardt, Marleen
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Thermogravimetric analysis (TGA) was used to determine the oxidative stability of edible oils (olive oil, milkfat) and triacylglycerides (triolein, trilinolein), while the effect of natural (-tocopherol, ascorbic acid) and synthetic antioxidants (butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and tertiary butyl hydroquinone (TBHQ)) were evaluated on stability of trilinolein. Trilinolein was oxidatively less stable than triolein, olive oil, and milkfat, while triolein was less stable than olive oil and milkfat. When comparing effectiveness of antioxidants, a combination of 0.01% BHA and 0.01% BHT increased trilinolein stability the most. Sensory testing showed that the addition of a combination of 0.025% -tocopherol and 0.025% ascorbic acid to milk did not influence milk flavor. However, when adding -tocopherol and ascorbic acid to milk at these levels, light-induced oxidation off-flavor was significantly reduced in comparison to unspiked milk after 10 h of light exposure (1100-1300 lx). The effect of antioxidants (added in a single initial dose, and in weekly additions) on light-exposed extended shelf-life milk over six weeks of light-exposed storage was measured by volatile analysis. An initial single addition of -tocopherol and ascorbyl palmitate significantly reduced hexanal content in light exposed milk throughout the first four weeks of storage, whereas the weekly addition of a combination of BHA and BHT reduced heptanal content of milk to such a degree that no significant difference was observed when compared with light-protected control milk. Poly(lactide-co-glycolide) (50:50) films loaded with 2% -tocopherol and a combination of 1% BHT and 1% BHA were used in an antioxidant release study in water and Miglyol 812Ã â at 4oC and 25oC, as well as a study on the effect of these films on dry whole milk and dry buttermilk stability. BHT was released through the hydrolytic degradation of the polymer when stored in water at room temperature for eight weeks. However, it was expected that hydrolytic polymer degradation would not take place when antioxidant-loaded films were stored in dry whole milk (3.01% moisture) and dry buttermilk (4.60% moisture). -Tocopherol, BHA, and BHT migrated into whole milk powder through diffusion over four weeks of storage at 25oC, and significantly reduced light-induced oxidation compounds.
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