Role of glass transition temperature in color and textural changes of dried fig

Fresh fig is a highly perishable fruit with a very short storage life. Therefore, drying is the most common method for fig preservation. Changes in water content during storage may lead to undesired physical changes in dried fig which is of great importance in its structure and quality. The objective of this study was to assess the effect of water on the physical properties of dried fig, using glass transition temperature (Tg). Tg, melting temperature (Tm) and the melting enthalpy (ΔH) of dried figs at different moisture contents were measured using differential scanning calorimetry (DSC). DSC thermogram showed that dried fig has a semi-crystalline structure. Tg and Tm decreased while ΔH associated with the melting of the ordered structure increased with increasing moisture content of fig. The results showed that water is a strong plasticizer for dried fig and reduced flesh firmness of fig significantly. Measuring color differences of dried fig at different moisture contents showed that by increasing water, fig flesh became darker significantly. Changes in texture, color and crystallinity of the dried fig as function of moisture were assessed using temperature difference (ΔT) between the fig temperature (T) and Tg. By increasing ΔT, the rate of firmness reduction, ΔE value and the extent of crystallinity increased.