| Starch is widely used in many food processing fields,as a staple food and an important raw material for humans.However,the application of natural starch is limited due to insufficient shear resistance and thermal stability,and easy to retrogradation.Therefore,in actual production and processing,the starch needs to be modified to meet different processing needs.The addition of hydrocolloids and fatty acids can be used to improve starch processing properties and extend the utilization of starch.In this paper,maize starch,three kinds of hydrocolloids,and four kinds of fatty acids with different chain lengths were used as raw materials to study the effect of the combination of hydrocolloids and fatty acids on the physicochemical properties and in vitro digestion properties of maize starch.Then starch-xanthangum-stearic acid ternary blend was added to the ice cream as a fat replacer in order to test its fat replacement effect.The main findings are as follows:(1)The effects of the combinations of three kinds of hydrocolloids(xanthan gum,sodium carboxymethylcellulose(CMC)and Hydroxypropylmethylcellulose(HPMC))and lauric acid on the physicochemical and in vitro digestion properties of maize starch were investigated.We proposed that the interaction between hydrocolloid and starch and the formation of starch-lauric acid complex together influence the physicochemical and digestive properties of starch-hydrocolloid-lauric acid ternary mixed system.Different combinations of hydrocolloids and lauric acid had different effects on the properties of the ternary mixed system.Compared with starch alone,the final viscosity of the starch-hydrocolloid-lauric acid ternary mixed system increased from 1357 c P to 1486-1672 c P,the consistency factor and dynamic modulus increased,and the gel hardness decreased from 123 g to 24-37 g.It was also observed that the type ? amylose-lauric acid complex was formed in the ternary mixed system.The in vitro digestion results showed that the content of slowly digestible starch and resistant starch in the ternary mixed system were increased by 7-11% and 5-6 %,respectively.Among the three kinds of hydrocolloid-lauric acid combinations added,starch with the addition of xanthan gum-lauric acid combination showed the highest viscosity,viscoelasticity,slow digestible starch and resistant starch content and the lowest gel hardness,followed by CMC-lauric acid combination,and the properties of starch were least affected by HPMC-lauric acid combination(2)The effects of the combination of xanthan gum and fatty acids with different chain lengths(lauric acid,myristic acid,palmitic acid and stearic acid)on maize starch pasting,rheological,gel,thermal properties,microstructure and in vitro digestion properties were investigated.The changes in fatty acid chain length had a pronounced effect on the physicochemical and in vitro digestion porperties of the starch-xanthan gum-fatty acid ternary mixed system.Compared with starch alone,the final viscosity of the starch-xanthan gum-fatty acid ternary mixed system increased from 1357 c P to 1563-1672 c P,the consistency factor and dynamic modulus increased,and the gel hardness decreased from 123 g to 24-60 g.And as the fatty acid chain length increasesd,the viscosity,consistency factor and dynamic modulus were decreased,and the gel hardness was increased.The thermal properties results showed that the type I amylose-fatty acid complexes were formed in the ternary mixed system.The endothermic enthalpy of the amylose-fatty acid complexed decreased and the endothermic temperature increased with the increase of fatty acid chain length,which indicated that the amount of complexes were reduced and the crystal structure of complexes were more closely ordered.Compared with the starch alone,the content of slowly digestible starch and resistant starch in the ternary mixed system increased by 8-12% and 5-11%,respectively.As the fatty acid chain length increased,the content of slowly digestible starch decreased and the content of resistant starch increased in the ternary mixed system.(3)The physicochemical and in vitro digestion properties of the maize starch-xanthan gum-fatty acid(palmitic acid,stearic acid)ternary mixed system after long-term pasting were studied.It was found that type II amylose-fatty acid complexes are formed after long-term pasting,and xanthan gum could interact with amylose-fatty acid complexes,which led to the significant change of physicochemical and digestive properties of the ternary mixed system.After a long-term pasting process,the final viscosity of the starch-xanthan gum-fatty acid ternary mixed system increased from 1153 c P to 2054-2479 c P,the consistency factor and dynamic modulus increased,and the starch gel exhibited paste-like behavior with non-gelling properties.The starch-xanthan gum-stearic acid ternary mixed system has higher viscosity and lower gel hardness.The in vitro digestion results showed that after long-term pasting,the content of slowly digestible starch and resistant starch in the ternary mixed system were increased by 14-17% and 8-10%,respectievely.(4)The maize starch-xanthan gum-stearic acid ternary blend prepared by long-term gelatinization was used as a fat replacer in the preparation of ice cream.The swelling rate,melting rate,hardness and sensory evaluation of the fat-reduced ice cream with the addition of the starch-xanthan gum-fatty acid ternary blend were measured to evaluate the effect of the blend in replacing fat.The results showed that as the replacement rate increased,the expansion rate of ice cream and the appearance morphology score increased,the melting rate,the hardness,the flavor score and color score decreased.The sensory evaluation score was close to the control,when the replacement rate was 50% and the taste was better.Based on results of expansion rate,melting rate,hardness and sensory evaluation of ice cream,the maximum replacement rate of ternary blend as fat replacer is 50%. |
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