Packaging Trends: Moving Towards Transparency

Dairy beverages in PET is set to be one of the major trends on the dairy product market. Consumers prefer transparent packages, they want to see the product concerned. That’s why many dairy firms now want to offer not only the classical whey-based, yoghurt or “Milk & Fruit” products with pH values below four in PET, but also the pH-neutral milk-based mixed beverages. Microbiologically safe bottling of pH-neutral dairy products in transparent PET, particularly when it comes to products intended for sale outside the refrigerated shelves, constitutes a rather special challenge. The reason is the high microbial susceptibility of pHneutral products in comparison to beverages with a pH value of less than four. Today, however, this is possible using an optimized aseptic bottling process. The success achieved over recent years for aseptic bottling of acid soft drinks in PET has proved particularly helpful for progressing the technical advances required.

Danger of light-struck flavor

After overcoming the microbiological obstacle, particular attention is now being devoted to the stability of the end-product under different storage conditions. The products concerned have to be chemically/physically stable, and above all taste-retentive, if they are also to be distributed and sold outside the cold chain.Milk is a particularly demanding challenge in this regard.

Storage experiments and sensory tests, for example, carried out by the Döhler Group with classic milk-based mixed beverages, show that even in colored PET bottles without a special protective coating a definite taste impairment is already detectable after only a few days. This sensory impairment is essentially attributable to the constituents of the milk. Riboflavin (Vitamin B2), for example, an important ingredient of milk, is exceptionally photosensitive. That’s why this unwanted taste is referred to as "light-struck flavor".

Transparent PET bottles with light protection Experiments in regard to packaging technology for solving this problem are nowadays aiming to offer special transparent PET bottles with light protection. These do not differ visually from standard PET bottles, but incorporate a light protection feature active in the UV range up to a maximum of 380 nm. The photosensitive range of milk, however, lies between 300 and 500 nm, so that complete protection by the packaging material is not possible. If the aim is to protect the product beyond 380 nm, the package would exhibit a yellowish-to-reddish color. It’s true that transparent packages for milk are not a revolutionary invention: after all, milk in glass bottles has been on the market for years. But since this is offered only in refrigerated form, with a maximum shelf-life of one week, light-struck flavor is only a minor, though definitely existent problem. HDPE is more oxygen-permeable and not transparent Because of milk’s photosensitivity, dairies have up till now mostly been selling their longer-shelf-life products in light-proof packages. The subject of oxygen-permeability was not the focus here, although oxygen, too, can have a crucially adverse effect on appearance and taste. Meanwhile, dairy products are now being offered in plastic bottles as well, but so far only for the refrigerated shelves as short-life products for consumption within 12 and 30 days. One commonly used packaging material for products of this kind up until now has been HDPE bottles (high-density polyethylene). Compared to PET, this HDPE is more affordable, but also significantly more oxygen-permeable, and in most cases colored white, and thus opaque. Recipes to combat the light problem When transparent plastic packages are now used, however, there is an inevitable interaction between light and oxygen. The light “activates” the oxygen, causing it to accelerate the beverage’s aging even more severely. The producers of modern day dairy beverages will in future have to attach higher priority to low-oxygen filling, all the more when a transparent package is desired. As a supplier of fruit-juice concentrates, compounds, flavorings and dyestuffs, the Döhler Group is working on basic-ingredient recipes designed to combat this light problem. The combination of special technologies with basic ingredients and fruit preparations for dairy beverages is a natural means of helping to ensure that the product is protected against harmful light energy and penetrating oxygen. The trend towards PET packages for dairy products is unmistakable, despite all the technological challenges involved. This type of package is familiar to consumers from other beverage categories and very popular: the material is lightweight, unbreakable, reclosable and has a young, mobile image. For the dairies, moreover, the advantage is that the packaging material provides a broad spectrum of design options and is ideally suited for innovations. More Information Dohler Group www.doehler.com