| Pulsed electric field(PEF)technology,a new non-thermal processing technology,had been successfully applied to liquid food,but not been widely applied in solid food.In our previous work,we found that PEF can be used in discontinuous solid materials.To understand the effect of PEF on the food qualities and processing properties of solid food,starch and gluten protein were studied.Firstly,the output energy regular pattern of pulse power supply was explored,then the structure and physicochemical properties of A-type,B-type and C-type starches were analyzed after PEF treatment.Finally,on the basis of the above research,the effect on wheat starch-wheat gluten protein(WS-WG)mixture system was explored after PEF treatment.The main results were as follows:(1)With the increase of electric field intensity and pulse frequency,the input energy of PEF increased in unit time.The input energy of PEF would reduced obviously by increasing air humidity,air movement rate and reducing the area of the top plate;glass could hinder the energy input of PEF,and the effect was more obvious with the increase of field strength.(2)The granules of three kinds of crystalline starches were destroyed,and the polarization cross became weaker after PEF treatment.With the increase of electric field intensity,the relative crystallinity and ordered structures of all starches(except pea starch)first increased and then decreased,and pea starch increased.The effect of PEF on the properties of different crystalline starches were different.With the increase of the electric field strength,the range of gelatinization temperature of A-type starches were increased and then decreased,and the ?H were decreased;the range of gelatinization temperature and ?H of B-type starches were decreased;the range of gelatinization temperature of the C-type starches were decreased and then increased,and the ?H were increased and then decreased.The thermal stability of starches(except corn starch)were changed by PEF.The freezing and thawing stability of A-type starches(except corn starch)were increased firstly and then decreased,and the freezing and thawing stability of B-type and C-type starches were increased.The solubility and expansion degree of A-type starches(except rice starch)were increased firstly and then decreased.The solubility of B-type starch were decreased and then increased,the expansion degree were decreased significantly;the solubility of C-type starches were decreased firstly and then increased,and the expansion degree were not changed obviously.The RDS of starch were increased,and the SDS were decreased after PEF treatment.(3)With the increase of wheat gluten protein content,the thermal characteristic parameters of wheat starch was increased,and the ?H was decreased and those changes were increased after PEF treatment.In the infrared spectrum,the peak intensity of the WS-WG mixtures was changed obviously in the fingerprint area 1200?800 cm-1,the strength of the starch band was gradually subsided and the strength of the amide band was gradually appeared with the increase of the WG content.There were four infrared absorption peaks of the mixtures at wavelength 1700?1600 cm-1,and the relative peak area were changed after PEF action.With the increase of WG content,the effect on the apparent viscosity of the mixtures was more obvious by PEF treatment.PEF increased the storage modulus of mixtures.With the increase of WG content,the gel properties of the mixtures were weakened,and the changes were increased after PEF treatment.To sum up,the influences of PEF were varied with the different crystal types and starch species,but the root cause was that the changes of the starch molecular structure under the effect of pulsed electric field,which changed the macroscopic physical and chemical properties of starch. |
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