Understanding product build up at packaging material surface to address food waste

Difficulty to empty the package is one of the main reason of food waste in yoghurt at consumer level with an estimated 5-10% of product residue being left on the packaging material. The phenomenon of product build up is explained by numerous hypothesis. However, these studies are empirical in nature. The purpose of this study is to develop a tool box to address the link between the physicochemical product properties and it’s macroscopic build up at a polymer surface. Build up was quantified using the gravimetric dip test in natural yoghurts with 0.5% and 3% fat content and vanilla yoghurts with 0.5% and 2.5% fat content. A theoretical build up value was calculated from the yield stress obtained from rotational rheometer and texture analysis. Limitations was observed in the yield stress values obtained from texture analysis, thus the values were not used for predicting the build up. Visualization of the morphology of protein content in yoghurt and build up on packaging material was done by fluorescence microscopy using Rhodamine B. In the gravimetric method the fat content was directly proportional to the build up and the effect was statistically significant. The theoretical assumption is that yield stress value obtained from rheometer is directly proportional to build up. Higher degree of correlation between yield stress value and product build up was observed in the low fat vanilla and natural yoghurt. In the high fat yoghurt, the build up could be an influence of other factors besides yield stress. Build up measurements with similar order of magnitude were seen in the experimental values from gravimetric test and theoretical values obtained from the rheometer. Good correlation was also obtained between rheometer measurements and images from the fluorescence microscope. Accumulation of aggregated protein flocs along the packaging material was observed with hollow structure of what appeared to be swollen starch granule. Clear distinction between protein and fat was not seen due to the fat globules being entrapped within the protein network.