Polyethylene terephthalate (PET) can be semi-rigid to rigid, depending on its thickness, and is very lightweight. It makes a good gas and fair moisture barrier, as well as a good barrier to solvents. It is strong, impact-resistant and naturally colorless with a high transparency. Bottles made from PET are excellent barrier materials and are widely used for soft drinks. PET packaging has clearly established itself as a superior container for a wide variety of consumer food and beverage products. Clarity similar to glass, wide flexibility in form, shatter resistance, and effective oxygen barriers and scavengers are qualities that combine to make PET the product of choice for a growing number of specialty beverage processors each year. Despite these advantages, a threat looms large that has not been universally addressed: the impact of UV light on colours, nutritional values and tastes in PET packaging. The complex issue of how UV light can impact beverage quality has now come to the forefront. To learn more about how UV light impacts beverages in PET packaging, Milliken Chemical commissioned an extensive research study. A series of lab tests assessed the impact of various levels of UV protection on formulation ingredients common to beverages and foods, including FD&C colourants (colourants certified for use in the colouring of food, drugs and cosmetics), vitamins and flavour components. The company's goal was to learn more about how UV exposure at different wavelengths can impact colour, flavour and nutritional content. It was also interested in learning more about potential interactions between ingredients when exposed to UV light at various levels of intensity and duration. The tests were carried out on pure aqueous solutions of single beverage ingredients. Ingredients were also tested mixed with other common beverage components, such as citric acid, vitamin C and trace minerals. The interactions of beverage components were called 'matrix' effects. The test models are the following: • PET control - standard PET container • Unexposed - standard PET wrapped in aluminium foil • UV 370 - PET container with Milliken's ClearShield® UV absorber at the 370 level, providing less than 10% transmission at 370nm • ClearShield 390 - PET with Milliken ClearShield at the 390 level, providing less than 5 per cent transmission at 390nm The samples were subjected to accelerated UV testing in a refrigerated (4°C) chamber equipped with Sylvania 351 UV bulbs, which were selected to simulate sunlight passing through glass, thus simulating a retail environment. Although oxygen was not eliminated from the test samples in these studies, the structure of the tests enabled a distinction to be made between purely oxidative effects and photo-oxidative effects. Several important findings emerged from this research. Milliken conducted UV exposure testing on the FD&C colourants Blue #1, Red #40 and Yellow #5. Here, the matrix effect was simulated by the addition of citric acid to a pH of 3.5 and 1ppm of iron. Over an exposure period of 14 hours, each of the colours showed substantially increased stability in PET bottles enhanced with 390 protections, and to a lesser extent with 370 protections. Vitamins and nutrients are generally sensitive to the effects of temperature, oxygen and light. A slight change in the molecular structure of a nutrient can render it biologically ineffective. Many vitamins are known to be specifically vulnerable to degradation by UV light, including vitamin A, B2 (riboflavin), B6, B12 and folic acid. Light also accelerates the destructive interaction between vitamins. For example, the degradation of both folic acid and vitamin C is accelerated by the combined presence of riboflavin and light. This is the cause of vitamin C degradation in milk exposed to light. In order to maintain compliance with food labeling regulations throughout practical shelf life of the product requires that nutrient levels in the food or beverage remain at or above a level relative to the declared value on the label. Milliken Chemical conducted UV exposure testing on several vitamins, including A, B2 (riboflavin), B6, B12 and folic acid. In general, each of these vitamins showed substantial sensitivity to UV and each was significantly more stable in PET bottles enhanced with 390 coverage. The 370 level of coverage, on the other hand, showed a more modest degree of protection. The degradation of flavour and fragrance ingredients can lead to a diminished sensory profile and the formation of unpleasant qualities detectable by taste and smell at low concentrations. Milliken investigated the lemon aroma complex due to its widespread application across a range of products in beverages, food and other consumer products. Lemon flavour is composed of several light-sensitive components including terpene hydrocarbons and oxygen-containing compounds that degrade upon exposure to UV light. One of the significant contributors to lemon flavour, and one of the most photosensitive, is 'citral'. When exposed to UV light, citral degrades into several byproducts, including 'photocitral-A' and 'photocitral-B', which are readily detectable by laboratory analytical methods. Another compound is also formed that exhibits a strong off-flavour at levels that are hard to detect through analytical methods. Milliken conducted exposure testing on citral to assess the differential impact of various degrees of UV protection. In this case, green PET bottles without a UV additive were also used in the test because many citrus beverages are packaged in such bottles. The test results show that PET with 390 protections retains the integrity of the citrus-flavoured beverage to a much greater extent than either 370 protection, green PET or standard PET, though the 370 protected bottles are much better than either PET or green PET. Also, sensory panels are a much more sensitive measure than analytical instruments and can easily detect flavour changes not indicated by the instruments. The use of UV protection is likely to grow as consumer packaged goods companies UV protection for PET containers is essential to assuring extended shelf life and the protection of UV-sensitive formulations, such as beverages with unique tastes, nutritional benefits and colour.