Moisture sorption isotherms and evaluation of quality changes in extruded snacks during storage

• Sorption isotherms were found to be typical type II sigmoid.
• Storage study in terms of quality parameters was investigated in this study.
• The study revealed that snacks in LDPE and LP were acceptable upto four months.
• Overall analysis suggested snacks were more stable in laminated pouch than LDPE pouch.

In this study moisture sorption and storage study of extruded snacks were investigated. Four temperature conditions of 20, 30, 40, 50 °C were used to determine the isotherm of extruded snacks using a gravimetric technique. Sigmoid curve of Type II was found for sorption isotherms. The data were analysed using several models such as, GAB, BET, Oswin, Smith, Caurie, and Iglesias and Chirife. A non-linear least square regression analysis was used to evaluate the model constants. The GAB followed by Oswin, BET and smith model best fitted the data. The effect of storage on the quality of extruded snacks packed in pouches of low density polyethylene (LDPE) and laminated pouches (LP) at ambient temperature condition of 25 ± 2 °C were examined. Storage stability in terms of quality parameters such as moisture, hardness, bulk density, color, lateral expansion, sensory characteristics and total plate count (TPC) was evaluated. On the basis of packaging material used the extruded snacks packed in LDPE pouches showed greater changes to quality parameters in comparison to LP during storage, suggesting the use of LP for longer storage period of extruded snack product.