Characterization of the Pore Structure of Starch Based Food Materials

Macroscopic pore structure parameters (bulk density, true density and porosity) and microscopic pore structure parameters (percentage closed pore volume and pore size distribution) for a highly expanded type (Wonder White Sandwich Bread) and a relatively compact type (Chessmen Butter Cookies) starch based food material were determined and their pore structures were compared. Bulk density determined by solid displacement and true density determined by pycnometry yielded porosity measurement s o f 0.9 for bread and 0.6 for cookies. Percentage closed pore volume calculated by comparing the true density of porous samples of bread and cookies with the true density of !heir compacted pellet s showed that both bread and cookies contained closed pores. Pore size distributions representative of the mercury porosimetry range (pores less than 200 um in diameter) indicated that the smallest pore diameter was 6 um for both bread and cookies. Pore size distributions obtained corresponded to about 16% and 65% of the total pore volume in bread and cookies, respectively. Both bread and cookie samples were found to undergo capillary hysteresis. Unidimensional mercury intrusion studies revealed a highly interconnected pore structure both in bread and cookies. Scanning electron microscopy (SEM) photomicrographs used to evaluate the pore structure qualitatively showed no directional orientation of the pore structure

APPLICABILITY AND COMPARISON OF VARIOUS TECHNIQUES FOR MEASUREMENT OF WETTABILITY AND CONTACT ANGLES BETWEEN OIL-BASED LIQUID AND STARCH-BASED SOLID FOOD MATERIALS

Contact angles of various oils and chocolate syrup were estimated on a commercial brand of white sandwich bread and a commercial brand of butter cookies using three different methods sessile drop geometry, sedimentation volume and immersion techniques. It was concluded that estimation of contact angles from the sessile drop geometry by photographic techniques is not possible for oils due to absorption into the starch-based solid In such cases, the sedimentation volume and immersion techniques were found to be practical methods for rough estimates of contact angles when needed. For the non-Newtonian chocolate syrup, estimation of contact angles with the starch-based solids by sedimentation volume was not possible due to the yield stress of chocolate syrup However, in this case, contact angles could be estimated from sessile drop geometry

Effect of polydextrose-substitution on the cell structure of the high-ratio cake system

Effect of polydextrose-substitution on the cell structure of the high-ratio cake system was investigated in terms of the bubble size distribution and foam drainage time of the cake batter, and the cake height, true and bulk densities, porosity, cell size and shape distributions of the cake crumb. Sugar-replacement levels were 0%, 25%, 50%, 75%, and 100% of the sugar content of the conventional high-ratio cake formulation

CHARACTERIZATION OF THE EXTRACELLULAR POLYSACCHARIDE FROM FRESH-WATER MICROALGAE CHLORELLA SP

The aim of this study was the characterization of the extracellular polysaccharide (gum) from freshwater microalgae Chlorella sp. For this purpose, determination of the component monosaccharides and minerals were chosen as the structural properties, while the thickening effect on aqueous systems and the effect on the dispersed phase volume fraction of oil in water (o/w) emulsions were selected as the functional properties. The gum was found to contain the monosaccharides: glucuronic acid (385 g/kg); arabinose (325 g/kg); glucose (193 g/kg); fucose [alpha- and beta-anomers (31 g/kg and 14 g/kg, respectively)]; and the minerals: calcium (16.3 g/kg); sodium (7.7 g/kg); potassium (20.4 g/kg); and zinc (1.1 g/kg) reported on a dry weight basis. The gum from Chlorella sp. was found to be a potential thickening agent. Its thickening and secondary emulsifying effects were found to be compatible with most of the food-grade salts when these salts are used in the recommended range (1 to 30 g/L) for foods. It was found that its thickening and secondary emulsifying effects are confined to the acidic range (pH 4 to 6)