Study On Physicochemical Properties And Bleaching Technics Of Lily Starch

Lily is a perfect food and drug resource, and its bulb contains rich starch. Chemistry constitutes, granules properties, solubility, swelling, gelatinization and viscosity of three samples and bleaching process were studied based on physicochemical analysis, X-ray diffraction examination, orthogonal test and so on in order to offer theoretical guidance to production of lily starch, which are Lilium. lancifolium Thunb starch sampled from Zhuzhou (Sample 1), Lilium. lancifolium Thunb starch (Sample 2) and Lilium. lancifolium Thunb starch (Sample 3) from Yizhang. The results are as follows:(1) The contents of starch from three samples are 78.74%, 87.33% and 78.36%, respectively. The contents of amylose are 24.36%, 26.04%, 21.38% respectively. The visible black polarization cross like "X" was observed by the polarizing microscopy. The X-ray diffraction graph of the lily starch appeared as B-type crystallinity. Gelatinization temperature of the three starches was 51.9~ 54.3癈, 55.7~61.0癈, 57.3~~60.7癈 respectively. The swelling power and solubility of the samples increased with the rising in temperature. The swelling power is small below 65癈, while rapidly increased at 75~95癈. Accordingly, lily starch was a restrictive swelling starch due to consisting of two phases.(2) The three samples poor freeze-thawing stability and could be freeze-thawed only once. The sediment of lily starch was very strong, and food additives such as sucrose and NaCl had the influences on the sediment. The sediment of the three samples is enhanced affter adding 0.1% NaCl to starch paste. But 0.1% sucrose added could restrain the sediment of the paste. The transparency of lily starches paste was very low, and the euphotic ratio was below 14%. The 5% starch exhibit a better hot stability of paste, and a bad cool stability of paste. The viscosity was measured by NDJ-8S viscometer under different starch concentrations, pH, rotation speed, sucrose and NaCl. The viscosity increased with the raising in the concentration of the starches and decreased with the rising in rotation speed and temperature. The viscosity was higher comparatively in c. pH 7.0.(3) The influencing factors such as oxidant demand, starch concentration, reaction time and temperature, and pH were tested to determine the technics conditions for oxidation bleaching of lily starches. The results showed that the whiteness of starch had an exponent interrelation to the concentration of starches, logarithm interrelation to the reaction temperature, the whiteness increased with the increase in H2O2, reaction time, acidity and alkalinity. These five factors had no marked effects on whiteness through orthogonal test and analysis of variance. The optimum bleaching conditions would be starch concentration 50%, H2O2 5.0%, temperature 40癈, time 30 min and pH3.0, respectively. The whiteness is more than 90% in these conditions.