Transparency of polymeric food packaging materials

Transparency is a very important technical parameter to evaluate and validate certain food packaging materials. In the recent scientific literature, several methods (i.e. transmittance, opacity, haze, and absorbance) have been used and such variety hinders a direct comparison of results from different authors. In this Review, we describe and discuss the most widely employed methods to measure transparency, with special emphasis on two main parameters: transmittance and opacity. Moreover, a comparison of the different techniques is addressed and the typical values of transmittance and opacity of common transparent food packaging materials are provided. Our current opinion is that transparency should be expressed as transmittance in the visible range due to both the quickness and easiness of the measurement and the standardization of data. This information should be accompanied by the thickness value and a graphical image of the analysed samples for a useful and complete characterization.

Automated summary

Transparency is an important parameter for evaluating and validating food packaging materials. Various methods such as transmittance and opacity have been used, making it difficult to compare results. This review discusses the most commonly used methods to measure transparency, with a focus on transmittance and opacity. The recommendation is to express transparency as transmittance in the visible range, accompanied by thickness value and sample images for comprehensive characterization.