A protein-rich extrusion-cooked snack based on tapioca starch, sorghum flour and rennet casein (moisture, 3.96%; protein, 19.75%; fat, 0.75%; carbohydrate, 73.04% and ash, 2.5%) packaged in metalized polypropylene/polyethylene (PP/PE) laminate pouches, under air (without nitrogen flushing) or with nitrogen flushing was stored for 6 weeks at 37±1?C and 80% RH. The moisture content and TBA value of the product increased (p<0.01) and crispness decreased (p<0.01) with storage period. Nitrogen flushing had no significant impact on the storage-induced change in the moisture content or crispness but tended to retard the storage-induced increase in the TBA value (p< 0.01); also, the difference between the TBA value of the product with and without nitrogen flushing generally increased with the storage time, the relevant interaction being significant (p<0.01). The product became darker in appearance during storage as evidenced by decreased Hunter L* value (p < 0.05); there was no significant change in Hunter a* value but Hunter b* value declined (p< 0.01). However, the packing atmosphere had no perceivable effect on the colour parameters of the snack during storage. The sensory scores for flavour, colour, texture and overall acceptability (OA) of the product significantly decreased during storage (p< 0.01), but the packing atmosphere influenced only the flavour and OA scores (p< 0.01). Further, the rates of decline in the flavour and OA scores of the stored snack packed under air were higher (p< 0.01) as indicated by the corresponding interactions. Thus the air-packed snack can be considered to have a shelf-life of at least 12 weeks under ambient conditions.