Shelf life of whole pasteurized milk in Greece: effect of packaging material

Chemical, microbiological and sensorial changes in whole pasteurized milk stored under fluorescent light at 4 °C in 500 ml bottles, made of: (a) multilayer pigmented [HDPE + 2% TiO2/HDPE + 4% carbon black/HDPE + 2% TiO2], 550–600 μm in thickness, (b) monolayer pigmented [HDPE + 2% TiO2], 550–600 μm in thickness, (c) clear PET, 300–350 μm in thickness and (d) pigmented [PET + 2% TiO2], 300–350 μm in thickness, were monitored for a period of 7 days. Milk packaged in coated paperboard cartons and stored under the same experimental conditions served as the “control” sample. Data were obtained for lipid oxidation, lipolysis, proteolysis, vitamin A and riboflavin contents, microbial growth including mesophilic and psychrotrophic counts and sensorial attributes (odour and taste) of whole pasteurized milk. Results showed satisfactory protection of milk packaged in all packaging materials with regard to microbiological and chemical parameters assessed over the 7 day period. Vitamin A losses, recorded after 7 days of storage, were, respectively, 8.8%, 10.5%, 29.8%, 50.9% and 14.0% in samples packaged in multilayer HDPE, monolayer HDPE, pigmented PET, clear PET bottles and control samples. Respective losses of riboflavin were 18.4%, 20.6%, 30.9%, 47.1% and 19.8%. Based on organoleptic analysis, the shelf life of whole pasteurized milk in Greece is 5 days. The best overall protection to the product was provided by the multilayer and monolayer pigmented HDPE bottles at a thickness of 550–600 μm. Such packaging materials are currently finding their way into the fresh milk packaging market.