Evaluation of water sorption isotherm, glass transistion temperature, vitamin C and color stability of mango peel powder during storage
Cristhiane Caroline Ferrari, Marcelo Antônio Morgano, Sílvia Pimentel Marconi Germer
Abstract
Abstract The purpose of this work was to study the physical and chemical stability of the mango peel powder produced by hot-air drying. Sorption isotherms at 25 °C and glass transition temperatures (T g ) of the samples in equilibrium at different a w were determined. The degradation of vitamin C and color parameter b* was evaluated along storage under controlled conditions (relative humidity = 60%, temperature = 10, 25 and 35 °C) during 180 days. GAB model well-described water adsorption of the product, showing a monolayer moisture content (X m ) of 0.1260 g water/g dry solids and a critical a w of 0.56. The Gordon-Taylor model predicted the plasticizing effect of water on glass transition temperature, since T g of the powders kept at different relative humidity conditions decreased as water activity increased. No visual signs of agglomeration and darkening were observed for samples stored at a w ≤ 0.529. The powders are a source of calcium and rich in potassium, copper, magnesium and manganese. The concentration of inorganic contaminants and pesticide residues were below the maximum allowed limits. The degradation of vitamin C and color parameter b* followed the first and zero-order kinetic models, respectively. The study indicated good stability for the powders along the storage at 10 and 25 °C, which can be incorporated into different food products, showing high retention of vitamin C, phenolic compounds, antioxidant activity and maintenance of color characteristics.