Effects of flavour absorption on foods and their packaging materials

Keywords: flavour absorption, scalping, packaging, food matrix, lldpe, ldpe, pp, pc, pet, pen,b-lactoglobulin, casein, pectin, cmc, lactose, saccharose, oil, modelling, storage, oxygen permeability, taste perception, sensory quality.

Absorption of flavour compounds by linear low-density polyethylene (LLDPE) was studied in model systems representing differences in composition of the food matrix. Proteins,b-lactoglobuline and casein, were able to bind flavours, resulting in suppression of absorption of flavour compounds. Polysaccharides, pectin and carboxymethylcellulose, increased viscosity, and consequently decreased absorption. Disaccharides, lactose and saccharose, increased absorption, probably caused by a "salting out" effect of less apolar flavour compounds. The presence of a relative small amount of oil (50 g/l) decreased absorption substantially. Combined oily model systems, oil/casein and oil/pectin, showed a similar effect. The extent of absorption of flavour compounds by LLDPE was influenced by food components in the order: oil or fat >> polysaccharides and proteins > disaccharides. A model based on the effect of the polarity (log P) of flavour compounds and on their partitioning coefficients between food(matrix) and packaging material was developed. The model is able to predict absorption of flavour compounds from foods into LLDPE when lipids in the food matrix are the determining factor in flavour absorption. Results show that the model fits nicely with experimental data of real foods skim and whole milk.

LLDPE, polypropylene (PP), polycarbonate (PC), polyethylene terephthalate (PET film and PET bottle) and polyethylene naphthalate (PEN) were immersed in a model flavour solution at different temperatures up to 14 days. The absorption rate and/or total amount of absorbed compounds increased considerably with increasing temperature. Depending on temperature, the total absorption of flavour compounds by the polyolefins (LLDPE and PP) was up to 2400 times higher than by the polyesters (PC, PET and PEN).

The effect of absorbed flavour compounds on the oxygen permeability of low-density polyethylene (LDPE), PP, PC and PET was studied. Due to swelling of the polymers as a result of absorption of flavour compounds, LDPE and PP showed a significant increase of oxygen permeability of 21% and 130%. The oxygen permeability of PC showed a significant decrease of 11% due to occupation or blockage of the "micro-cavities" by the absorbed flavour compounds. Flavour absorption by PET did not affect the oxygen permeability significantly.

The influence of flavour absorption LDPE, PC and PET on the taste perception of a flavour model solution and orange juice stored in glass bottles was studied with and without pieces of the respective plastic films. Although the content of flavour compounds between controls and polymer treated samples decreased substantially due to absorption, no significant effect on the taste perception of the model solution and orange juice were observed by triangular taste panel tests.