| Quick-frozen Tang-yuan in the market has some quality problems at present, such as frost crack or frozen breaking, the soup isn't clear after boiling, and it is tasted too viscous and so on. Hydroxypropylated waxy rice starch (HPWRS) is seized of freeze-thaw stability, boiling resistance, non-ionic. This paper expects to solve the existing problems based on the excellent physicochemical properties of HPWRS, and improves the quality of quick-frozen Tang-yuan.The concentration of related factors influencing degree of substitution of HPWRS were studied through single factor experiment, the six factors were waxy rice starch, NaOH, Na2SO4, epoxy propane, reaction time and reaction temperature. According to single factor experiment, while Na2SO4 reaching to 20%, and reaction time achieving 20h, selected waxy rice starch, NaOH, epoxy propane, reaction temperature to design experiment with Design-expert, got the optimal process condition: concentration of waxy rice starch was 38.82%, NaOH was 1.01%, epoxy propane was 13.49%, Na2SO4 was 20%, reaction temperature was 40.81℃, reaction time was 20h.Physicochemical properties of HPWRS were researched. HPWRS kept the shape of raw starch basically. And all of gelatinization temperature, peak viscosity, trough viscosity, final viscosity, breakdown value, and recovery value decreased gradually, with the degree of substitution increasing; HPWRS had a rather low apparent viscosity under acid surroundings, when cane sugar consistency and pH increasing, apparent viscosity of HPWRS was improved by the raising of degree of substitution, however, apparent viscosity of HPWRS was decreased with the increasing of NaCl consistency; As the substitution degree augmenting, both transparency and freeze-thaw stability of starch paste were improved; at the same time, HPWRS had a wonderful compatibility with glutinous rice flour, and it could enhance softness of structure. The influence on quick-frozen Tang-yuan were studied by four kinds of hydroxypropyl starches, research objects were HPWRS, hydroxypropyl corn starch, hydroxypropyl potato starch, hydroxypropyl tapioca starch. According to the comparison of quality of quick-frozen Tang-yuan, SEM of quick-frozen dumping powder, dynamic rheological properties and texture profile analysis of glutinous rice ball, the result could be showed that: HPWRS was more suitable for quick-freeze Tang-yuan.Through frost cleft rate, water loss rate, sensory evaluation, soup turbidity rate, visual estimation and cooked time, compared HPWRS with common additives of quick-frozen Tang-yuan, the result showed that:HPWRS could improve product quality of quick-frozen Tang-yuan. And then, selected HPWRS, DHC, glycerel monostearte and quick-frozen oil to design orthogonal tests, got the optimal proportion: HPWRS was 1%, DHC was 1%, glycerel monostearte was 0.22%, quick-frozen oil was 1.5%. |
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