Effect of starch types on the gelling behavior of Hsian-tsao leaf gum extracted by sodium carbonate

• Main Authors: Fang Lung-June, 方亮鈞
• Other Authors: Lih-Shiuh Lai
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/33350992112013835493

碩士 === 靜宜大學 === 食品營養研究所 === 86 === Effects of gum concentration (0.3 - 1.8%), starch types (wheat, corn and cassava) and concentration (2-4%) on the gelling behavior of Hsian-tsao (Mesona procumbens Hemsl) leaf gum extracted by sodium carbonate solutions were studied. Steady and dynamic shear rheological measurements, rapid visco analysis, texture profile analysis, color as well as microstucture of the starch/gum mixtures were performed during or after a controlled heating and cooling process. It is found that the starch/gum mixture showed higher rheological/textural properties than starch or gum alone at comparable concentration, indicating significant interactions between starch and Hsian-tsao leaf gum. The gel viscosity as determined by rapid visco analysis, storage modulus as determined by dynamic shear measurement, apparent viscosity as determined by steady shear measurement, as well as firmness as determined by texture profile analysis, of the mixed system increased with increasing gum concentration to a certain extent, then leveled off or decreased with higher gum concentration. The critical gum concentration, which provide an optimum interaction with starch, depended on starch types and increased with increasing starch concentration. The mixed systems showed typical biopolymer gel behavior since their tan delta values were found to be less than one or close to one. In addition, the mixed systems exhibited shear thinning behavior since their apparent viscosity decreased with increasing shear rate. A power law model was used to simulate the flow behavior of the mixed systems. The flow behavior index in the power law model was found to decrease, whereas, the consistency index increase with increasing gum concentration in the mixed systems. A comparison between the steady shear and dynamic shear rheological properties of the mixed system showed that Cox-Merz superposition principle was not suitable for the Hsian-tsao gel system. In general, mixed systems containing wheat or corn starch were brighter than the one containing cassava starch, as indicated by the Hunter''s L values. Scanning electron microscopy observation revealed that a denser and ordered network was formed as the amount of starch and gum increased to a certain extent.