THE EFFECTS OF GLUCOSE SYRUP AND GLYCEROL ON SOME PHYSICAL PROPERTIES OF DRIED FIGS

Abstract

The effects of glucose syrup and glycerol (40%, w/w) on moisture sorption isotherms, textural hardness, sugar crystallization and color of dried figs equilibrated at different water activities at 25C were studied. The additives caused significant increases in the equilibrium moisture level in fig samples. The Guggenheim-Anderson-deBoen equation was able to fit the experimental data and gave the lowest monolayer moisture level for the control without additives while this value for fig–glycerol mixture was greater than fig–glucose syrup. In the presence of glucose syrup or glycerol, the texture of fig was softer than the corresponding control and glycerol was more effective than glucose syrup. Sugar crystallization in figs decreased in the presence of glucose syrup/glycerol and its maximum level occurred at low water activities while this value for control sample was observed at intermediate water activity region. The color of fig–glycerol sample was darker than the control and fig–glucose syrup sample. PRACTICAL APPLICATIONS Plasticizers that bind water in food systems and lower the water activity of food materials have good potential in acting as texture modifiers in fruits with hard texture like dried figs. They can also reduce sugar crystallization, which is one of the most important factors determining consumer acceptability of dried and semidried fruits with high amount of sugars. This work evaluates the effects of glucose syrup and glycerol (at 40%, w/w) on moisture sorption isotherms, textural hardness, sugar crystallization and color of dried figs equilibrated at different water humidities. With these results, glucose syrup/glycerol may be introduced as new additives having good potential to be used as hygroscopic ingredients in figs to have more water with greater microbial stability.