Determination of the spreading pressure and shelf-life of spray-dried coffee powder: quality assurance of a water-soluble food

In this work, the values of monolayer (M_o) of the GAB model, generalized GAB model, and minimum change in spreading pressure (MCSP) of the adsorbed water were compared to determine the optimal storage conditions of spray-dried coffee powder. The effect of the adsorption models on estimating the water-vapor permeance of the packaging material and the product’s shelf-life was also evaluated. For this, the powder was packed in a plastic film and stored at three temperatures and two relative humidities (RH). As a result, the best physicochemical stability of the powder was achieved at water contents corresponding to MCSP, from 0.01-0.04 g water/g dry solids. It was also observed that the most extended shelf-life was 246 days, obtained at 25 °C/75 HR with a permeance of 1.45 x 10^-4 g/m²dPa, and the shortest was 8 days at 45 °C/97 HR with a permeance of 4.2 x 10^-4 g/m²dPa. Additionally, it was determined that the degradation rate tripled (Q₁₀ ≈ 3) every 10 °C with activation energies greater than 90 kJ/mol. The results show that the spreading pressure contributes to ensure the quality of water-soluble foods.

Keywords: Spreading pressure, Shelf-life, Water-vapor permeance, Monolayer, Adsorption model.