| Fernery is roots of pteris fern plants, rich in starch, which is edible after prepared and applied to the food and pharmaceutical industries. The process of washing method and hydrogen peroxide bleaching of four samples was optimized. The pasting properties, rheological property, aging properties and puffing characteristics of fernery starch were studied and analyzed as well as the affects of the factors of processing on properties of fernery starch.The optimum conditions for extracting fernery were Limewater pH8.0, ratio of sample and water 1:4, extracting time 3 hours, subsiding time 7 hours. On these conditions, the starch extraction ratios were above 82.61%.The visible black polarization was observed by the polarizing microscopy, showing a black cross or "X"-shaped. The crystalline pattern of fern starch was C type. The shape of fern starch granule was various, irregularly, and its starch content was over 6.0%. Meanwhile, the content of fat and pectin in fernery starch were more than others, and bleaching technics had less effection to granule characteristic. With temperature rising, both solubility and turgidity values of fernery starch were inclined to increase.The bleaching with H2O2 improved the color effectively; the whitness increased 45.3%-132.4% in the optimazed conditions. And the effect of blaching on the micro-structure of starch was less. The solubility was improved a little during bleaching, and freezing stability was improved great during bleaching.Gelatinization temperature of four fernery starchs is between 55℃and 76℃. Freeze-thaw stability of starch paste was worse than potato starch, but better than corn starch. The transmittance value of fernery starch's starch paste was lower. And it got higher as the pH value and the sugar concentration value increasing, and got lower as 1% and 3% NaCl or CaCl2 added.The analysis by RVA shows:with the increasing of concentration of starch, peak viscosity, final viscosity and breakdown value improved remarkably; with the salt concentration increasing, the peak viscosity and final viscosity inproved while breakdown value droped; the lowest value of peak viscosity, final viscosity appear in strong acid condition while the peak viscosity, final viscosity were higher in neutral and alkaline condition; as the concentration of sucrose increasing, the peak viscosity, final viscosity and breakdown value improved, too.Four samples all have thixotropy, which was increase in sample 1 and the others decreased. Viscosity of four samples was increased with the increased starch concentration, sugar concentration, decreased with the increasedspeed, temperature, concentration of NaCl; The viscosity decreased in strong acid and strong alkaline conditions. The stinffess of gel was 120.75, which was degree of soft condensed.The study shows that the retrogradation was occurred during the paste storage by optical microscope and X-diffraction analysis. Starch paste viscosity was increased and then decreased during 72 hour's storage; the euphotic ratio was decreased, too.The retrogradation stability of paste was stable both in strong acid and in strong alkali. It decrease in 1-3% NaCl, glucose and sucrose can make starch retrogradation increased, sucrose was better than glucose.Fernery starch showed stability both in microwave puffing and fried puffing, which was hindered by the existence of salt, sodium bicarbonate, sucrose and fat; the more the concentration of salt, sodium bicarbonate and fat are, the more the hardness of the production will be. Salt has a great effect on microwave puffing of starch while so do sodium bicarbonate on fried puffing. The hardness of production was improved in low concentration of sucrose while was decreased in high. Salt make the pore of puffing production bigger, and fat make it small. Sodium bicarbonate enlarge pore of fried puffing production, but has almost no effect on microwave puffing production; Sugar enlarge the pore ofthe fried puffing production, but reduce which of the microwave puffing production. |
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