a farahnaki

Crystallization is an important phenomenon that affects some quality attributes such as appearance, texture and shelf life in many food materials. Sugar crystallization is a major challenge for dried fruits such as figs with low moisture levels and high sugar contents. In this study, the effect of glycerol and glucose syrup (DE = 38) on the amount of sugar crystallization in figs with different moisture contents was investigated using X-ray diffraction. The addition of glycerol and glucose syrup increased equilibrium moisture content and reduced sugar crystallization significantly. In the presence of glycerol, sugar crystallization was one third of the control. Glycerol also had greater effect compared to glucose syrup. Changes observed due to the presence of glycerol and glucose syrup could be attrinuted to the hygroscopic behavior of these additives and their ability to keep more water at a specific water activity.

Salad dressing is a semisolid emulsion and a colloidal system with high consumer demand. Food polysaccharides (e.g starch) are used in the formulation of salad dressing to improve its physical properties and sensory attributes. In this research, 10% mixture of wheat or maize starches were used to produce pregelatinized starches by a double drum drier, followed by milling and sieving. The pregelatinized starches (10%) were applied in the formulation of a salad dressing instead of native starch. Viscosity (at 25 and 35◦C), Hunter color parameters of the samples were evaluated and compared. Pregelatinized starches were more effective in increasing viscosity of the samples compared to corresponding native starches, and the effect of maize starch was greater than wheat starch. Significant differences were recorded in terms of color parameters of the samples. Pregelatinized starch caused higher L values (lighter samples) while the native starch samples were creamy-light yellow. In general, it can be concluded that the pregelatinized starches had better functional properties in salad dressing compared to native starches, and the produced pregelatinized starches can be used instead of native starch in the formulation of salad dressing.

In this research, tomato peel and waste seed obtained from tomato paste processing were dried and milled. The obtained powder was added to tomato ketchup sauce in different proportions (1, 2, 5, 7 and 10%). To study the effect of tomato peel and seed powder on physicochemical and nutritional properties of the tomato ketchup samples, the parameters including lycopen, total solid, brix, total sugars, reducing sugars, protein, fat, ash, fiber, vitamin C, pH, color (L, a/b) were evaluated. Rheological properties of the ketchup samples (consistency and viscosity) were determined and compared with control samples. Sensory evaluation of the ketchup samples was carried out after 1, 2 and 5 months of storage by a group of panelists. Addition of tomato peel and seed powder resulted in an increase in total solid, brix, ash, fiber, protein, fat, consistency and viscosity of the ketchup samples. Sensory evaluation tests did not show any significant difference between the color, flavor, texture and overall acceptability of the control and samples containing 1 or 2 % of tomato peel and seed powder. In addition, sensory evaluation tests did not show any significant changes in the ketchup samples during storage. Thus, it can be concluded that nutritional and rheological properties of tomato ketchup can be improved by addition of tomato peel and seed powder.

‏ In this research the effects of two common cooking processes of foods, namely, autoclave and extrusion cooking on the molecular and physicochemical properties of wheat starch were investigated. The results showed that the solubility of the autoclaved samples increased with increasing the temperature while their relative viscosity decreased. These findings indicated that the molecular degradation of starch could occur during autoclave cooking. Moreover, constant sedimentation coefficient (s-value) of amylose and decreasing the s-value of amylopectin with increasing the temperature further confirmed degradation of amylopectin in particular. The results of the extruded samples showed that reduction in water content may increase the shear and pressure produced during extrusion cooking, which in turn could cause several changes in starch properties including degradation of starch granules, formation of amylose-lipid complex and degradation of amylopectin (as determined by reduction of the s-values). Also, reduction in water content could increase the puffiness of the final products and reduce the cold-water and final viscosities of the extruded samples. These observations may indicate the importance of the molecular studies of starch for better interpretation of physical changes of the final products.