EFFECT OF WRAPPERS, TEMPERATURE, HUMIDITY AND MODIFIED ATMOSPHERE ON PHASE-TRANSITIONS DURING STALING OF BREAD

The mechanism of bread staling and associated phase transition of stor ed bread, when packed in different wrappers under vaccum and nitrogen atmosphere and exposed to different humidities and temperatures were d etermined, using differential scanning calorimeter (DSC) and Instron u niversal testing machine. Thermal events measured by DSC showed the fo rmation of crystallites, which melted at about 59 degrees C, 95 degree s C and 111 degrees C after different intervals of storage. However, a fter 15 days of storage, the bread showed a single endotherm peak in t hermogram, suggesting inter link of all crystallites through network. The mechanical properties determined by Instron in compressive mode sh owed three stages of hardening development. Up to 48 h, the rate of in crease in stored bread was less. Between 48 and 72 h, the late of incr ease in firmness increased appreciably. After 72 h, the rate of increa se in firmness began to decline and became almost constant after 15 da ys. These changes in firmness development coincided with phase transit ions in DSC studies. Breads wrapped in waxed paper and polypropylene a nd stored at 55 degrees C gave minimum staling compared to those packe d in other wrappers.