Protective effects of titanium dioxide packaging modification on sensory and oxidative changes in milk over 35 day shelf-life

Milk is often packaged in translucent containers providing little protection against flavor degradation from light. The effectiveness of TiO2 modifications of high density polyethylene (HDPE) packaging in affecting light-induced oxidation of extended shelf-life milk (2% total fat) and omega-3 fatty acid enriched milk (2% total fat) was studied. Packaging effectiveness was determined by assessing product quality, including changes in flavor, measuring changes in volatile compounds, thiobarbituric reactive substances and riboflavin concentrations.  Products were evaluated over a 35-day shelf-life when stored under fluorescent light (2200 lux) at 4"C. HDPE packaging included clear (no TiO2) serving as control (light exposed: no light barrier, light protected (foil overwrap) and three different TiO2 levels (low, medium, high) for the experimental treatments (total of five packaging treatments). TBARS was a good predictor of the perception of changes in sensory characteristics in 2% milk.. Under the experimental conditions used, a TBARS value of 1.3 mg/L could be considered the limiting sensory threshold for oxidized milk. Riboflavin concentration decreased by 10.5% in the light-protected control over 36 days and 28.5% in the high TiO2 packaged 2% milk, but losses were greater than 40% for all other packages. In omega-3 enriched milk, the high TiO2-HDPE package provided greater protection of sensory quality and riboflavin than clear, low and medium TiO2 packaging. However riboflavin decreased by 28% even in the light protected control which is a higher loss than observed in 2% fluid milk without omega-3 lipids. TBARS was greater than 4 mg/L in all products, including the light-protected control within three days, suggesting that oxidative stability was low. Omega-3 milk packaged in clear HDPE package exceeded MDA of 3 mg/L by day 7, suggesting the milk would have changes in sensory quality related to oxidation. The high TiO2 package protected riboflavin concentration from degradation and controlled MDA concentration the best of the TiO2 treatments through the test period in both fish oil enriched and non-enriched products.