Shelf-life prediction of instant coffee by mathematic method

The limiting factor of instant coffee shelf-life is the gain of moisture from the external environment, which causes the total agglomeration of the product. One of the ways to estimate instant coffee shelf-life is through the mathematic method, which relates the product moisture increase by means of its moisture sorption isotherm with the water vapour permeability rate of the packaging material. In order to assess the adequacy of this technique, instant coffee was packaged in three types of materials / two sizes of package, and stored at 30,0 ± 1,0°C and 80% of relative humidity. Instant coffee isotherm achieved by the disiccator method was adjusted by the following four equations: linear, Halsey, Oswin and GAB. The conclusion was that instant coffee shelf-life does not depend on the package size (25 and 50g) for the materials being studied and was of 15 days in low density polyethylene (LDPE) - 30µm), 3 months in bioriented polypropylene / bioriented pearlized polypropylene (BOPP/BOPPP - 20µm/40µm) and of 3.5 to 4 months in metallized polyester/PEBD (PETmet/PEBD - 12µm/70µm). The instant coffee moisture gain determined experimentally was similar to the estimated through the mathematic method for values lower than 12%, independently from the equation used to adjust the moisture sorption isotherm of the product.

instant coffee; package; shelf-life prediction