Application of Weibull Hazard analysis to the determination of the shelf life of roasted and ground coffee

Roasted and ground coffee was stored at constant O-2 partial pressure (0.5-21.3 kPa), a(w), (0.106-0.408) and temperature (4-35 degreesC). Product acceptability was monitored by use of a modified Weibull Hazard sensory method where the end of shelf-life was the time at which 50 % consumers found the product unacceptable. The effect of O-2, a(w) and temperature was studied from a kinetics standpoint. Oxygen increase from 0.5 to 21.3 kPa accelerated deterioration 20-fold. A water activity increase of 0.1 led to a 60 % increase in deterioration suggesting non-enzymatic browning activity, while a temperature increase of 10 degreesC rose the rate of deterioration about 15-23 %. The activation for sheaf life was congruent to 13 kJ/mole indicating diffusion within the glassy matrix is controlling deterioration.