| Water caltrops are rich in nutrition and balanced amino acids, which also haveanti-cancer and other physiological effects. Water caltrops are favorite medicinal and edibleproducts for people. Water caltrops can be processed into water caltrop flour which is rich innutrition, easy for storage, and convenient to eat. The water caltrop starch can be extractedand used in the food and chemical industry as a new natural starch. Therefore, the applicationchannels of water caltrop can be broadened, conquering the low consumption andinconvenience of this high-quality raw material.Firstly, the preparation methods of the water caltrop flour and water caltrop starch werestudied and the basic components of them were measured. Based on the property of proteinsin water caltrop, the high purity food grade water caltrop starch with a low protein content(less than0.5%) was obtained by a physical separation method.Secondly, the physicochemical properties of water caltrop flour and water caltrop starchwere studied, and were compared with that of the tuber starch (potato starch) and cereal starch(corn starch). The results showed that the amylose content of water caltrop was17.11%,which was between that of the potato starch (13.72%) and corn starch (25%). It had smallparticle size (20.86μm), which was smaller than the potato starch (30.01μm) and corn starch(45.46μm). Water caltrop starch belonged to A-type high crystalline starch by X-raydiffraction analysis, and it had high diffraction intensity in the characteristic peaks. Thecrystallinity (36.47%) was higher than potato starch (29.88%) and corn starch (34.34%). Byscanning electron microscopy, it was observed that the water caltrop starch granule surfacewas smooth and most of them were oval in shape. The water caltrop starch had goodtransparency (51.66%), which was similar to potato starch (61.18%) and significantly higherthan that of corn starch (27.25%). Its solubility was between that of potato starch and cornstarch, and the expansion degree was lower than that of potato starch but close to corn starch.The water caltrop starch paste had good thermal stability and was not easy to retrogradate. Itbelonged to pseudoplastic fluid. Its apparent viscosity was lower than that of potato starch andcorn starch, and decreased with the increase of shear rate it presented the shear thinnedpseudoplastic phenomenon. The hardness of water caltrop starch gel (568.60g) wassignificantly higher than that of potato starch (295.57g) and corn starch (174.10g).Compared with water caltrop starch, water caltrop flour had better solubility, higherswelling degree,transparency improved (57.66%), but weaker gel hardness (185.71g). Thegelatinization characteristics and rheological properties of them were close, and the othercharacteristic difference was not significant.Thirdly, the different water caltrop aging pulverizing processes were studied. Therehydration was taken as the main indicators and the different curing process optimumparameters were obtained. The optimum cooking pulverizing flour conditions were60%water content and cooking time of40minutes. The optimum microwave pulverizing flourconditions were70%water content, microwave power600w and microwave time of150s.The optimum roasting pulverizing flour conditions were120℃roasting temperature and roasting time of6.5min. The optimum extrusion pulverizing flour conditions were130℃screw temperature, screw rotation at130r/min and26%water content.Then, the qualities of water caltrop powder with different pulverizing processes werecompared. Changes in nutrients (starch content, reducing sugar content, free amino acids,starch, protein hydrolysis curve) and physicochemical properties (gelatinization, rehydration,rheology) were analyzed. The results showed that the extrusion process was the best way tofurther develop instant water caltrop powder.Finally, the instant water caltrop starch with good dispersibility was developed. In orderto get the instant water caltrop starch with best water soluble dispersibility, particle size of thepowder was changed and lecithin and white sugar were added. Caking rate was chosen as themain indicators. At last, the best process conditions were obtained as follows: the lecithincontent0.21%, the white sugar content11.70%, particle size of powder250～420μm. |
PDF Full Text Request