A MALDI-ToF study on the proteinic fraction of different packaged milk samples

The type of packaging may also substantially affect milk quality by directly controlling the amount of oxygen and light available to interact with the product as well as by providing perfect seals in order to avoid post-pasteurisation contamination by microorganisms. To this regard, modern technologies adopted for the production of the flexible barrier packaging materials (i.e. vacuum coating and coextrusion) have significantly contributed to shelf-life extension of a variety of foodstuffs at a substantially reduced cost as compared to conventional packaging materials. In particular many attempts to improve milk packaging have been conducted and apart from traditional glass bottles, polypaired multi-layer (polyethylene/paper/low density polyethylene) and plastic (polyethylene terephthalate PET) containers have been used. Several related studies put in evidence that light exposure is responsible of many changes in milk nutritional and flavour milk characteristics. These changes are related to destruction of light sensitive vitamins and chemical reactions affecting proteins and lipids, while light induced flavour development is dependent on the availability of oxygen, controlled by reducing the amount of head-space in the container, avoiding agitation and by using impermeable containers. To check the influence of different packaging and shelf-life on milk quality, a research have been conducted on samples of fresh pasteurised milk and the proteinic fraction have been chosen as molecular marker of milk genuineness and nutritional value. All major proteins have been detected including caseins (-, -, -caseins), as well as -La, -Lg and the polypeptide fraction “proteose-peptone” arising from the activity of psychrotrophic microorganisms producing proteases (plasmin) able to degrade -casein in -casein and proteose-peptone. The aim of the study is the evaluation of the qualitative features of fresh pasteurised milk samples packed in Tetra-Brik, Tetra-Rex, PET and glass using the MALDI-Tof technique, considering the effects on the proteinic fraction at different shelf-life