| Lily bulbs are commonly consumed as a vegetable and also used as a Chinese traditional medicine,which is a popular health food.Lily starch is the main component in lily bulbs,accounting for 60-70%of the dry weight of lily bulb scales.Lily resources were rich,different varieties of lily starch showed different shape and structure,so its functional properties.In order to expand the application of lily starch in different products,the structure and function of different varieties of lily starch were studied.Natural starch had showed some defects,which was limited to use in some extent,and often through physical modification or chemical modification to meet the demand for starch in different foods.However,the effect of heat-moister treatment and acid treatment on the structure and properties of lily starch was still in the blank stage.Lily starch was modified to obtain the required functions and could be suitable for various food and non-food applications.In this paper,the structure and characteristics of different varieties of lily starch were studied,and the different modification methods and the effect of different kinds of hydrocolloids to the structure and characteristics of lily starch were studied,in order to provide theoretical guidance for the application of lily starch in different foods.Starches were isolated from bulbs of seven lily cultivars grown in China and their morphological,structural,and physicochemical properties were investigated.All the isolated starch samples showed triangular,elliptical,less scalloped,round,and irregular shaped granules.Starch of different lily cultivars exhibited B-type crystalline pattern.The median diameters(D50)was found to be in range from 17.79?m to 45.06?m and the amylose content in range from 23.63 to 30.38 g/100 g starch.The weight average molar mass(M_w)of amylopectin ranged from 4.03×10~7 g/mol to11.00×10~7 g/mol and root-mean-square rotation radius(R_z)ranged from 203.90 nm to264.20 nm.HPAEC-PAD chain distribution analysis revealed that the average chain length of amylopectin ranged from DP 23.19-25.29.Starch samples of different lily cultivars showed peak viscosity ranging from 1699.7 cp to 2963.0 cp,and pasting temperature varying from 63.83?to 71.00?.Furthermore,the transition temperatures of the starch samples isolated from different lily cultivars were found to be in range from 50.76?to 57.59?for onset temperature(T_o),54.57?to64.30?for peak temperature(T_p),and 68.07?to 77.16?for conclusion temperature(T_c).The gelatinization temperature range(?T_r)was found to be from16.66?to 21.65?and enthalpy(?H)was in range from 11.46 J/g to 16.29 J/g.These results indicated that lily starch properties were significantly different depending on lily variety,which could help in understanding the convenience of these starches for the application in different food and non-food industries.The morphology,particle size distribution,long-range ordered structure and short-range ordered structure,swelling and solubility,gelatinization characteristics,thermal,rheological and digestibility properties of lily starch treated with different moisture content and hydrochloric acid concentration were observed and analyzed.The results showed that after heat-moister treatment,the surface of the starch became rough,starch granules began to aggregate,and the growth point of starch appeared pore structure.The black area of the cross became larger than before.The particle size and distribution range of starch granule increased after heat and humidity treatment.The crystal structure of starch changed from B-type to C-type with increasing crystallinity.After acid treatment,the surface of lily starch became rough,the intensity of polarized cross light were weakened,the particle size and distribution range of starch particle size increased with the hydrochloric acid concentration,the crystal structure of starch was still B type,while the crystallinity decreased.After modification,the swelling power of lily starch was decreased.The solubility of lily starch was decreased by heat-moister treatment,while and the hydrochloric acid showed the opposite tendencies.The modified starch showed a reduced resistant starch content than the native starch under uncooked conditions,but showed a increased resistant starch content after boiling gelation.It indicated that the crystal structure of the heat-moisture treated starch was more orderly and stable.The interaction between the molecules of acid-treated lily starch were strengthened,while the crystal structure of the starch was destroyed,the enzyme sensitivity was also improved.The changes of the properties of modified starch after different heat-moister treatment and different acid concentration treatment were clarified,which could provided a reference for the production of lily modified starch.By adding hydrocolloids(guar gum,xanthan gum,gum arabic,pectin,konjac gum,hydroxypropyl methylcellulose)from different sources to the lily bulb starch,the effects of hydrocolloids on the functionality of lily starch were investigated through the determination of gelatinization,viscosity and thermal and rheological properties.The results showed that those properties of the mixed system were significantly different.The peak viscosity,the trough viscosity and the final viscosity of the guar gum mixed system were significantly increased,while the other hydrocolloids mixed system were reduced.In the DSC measurement,hydroxypropyl methylcellulose reduced the peak temperature and conclusion temperature of the mixed system,and the gelatinization temperature of the mixed system became higher after the addition of the other hydrocolloids,the gelatinization temperature range and the thermal enthalpy value after the addition of the hydrocolloids were reduced.Lily starch and the mixture of hydrocolloids and lily starch from different sources showed shear thinning phenomenon with the increased shearing frequency,all of which were pseudoplastic fluids.The elastic modulus(G')and viscous modulus(G?)of the guar gum mixture were significantly increased,while the G'and G?of other hydrocolloids mixed system showed different tendencies.The molecular interaction between hydrocolloids and lily starch was studied,which could provided a reference for the application of lily starch and hydrocolloids mixed system in food. |
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