| Malicacid corn starch ester(MCS) was preparation with corn starch and malic acid using dry method. The effects of various factors on the degree of substitution were studied, and the process conditions were optimized. The properties of the prepared malicacid corn starch were determined, and the digestibility of the MCS was studied,and the influence of MCS on the product was studied.. The results were as follows:1.The effects of various factors on the degree of substitution of MCS were studied, and the response surface experiment was carried out to optimize the preparation process. The optimized preparation process conditions were as follows:the reaction temperature is 146.9℃, the time is 5.5 h, the pH is 1.41, and the malic acid-to-starch ratio of 0.580(m/m). Under the experimental conditions, the degree of substitution of the prepared MCS was 0.331. At the same time, the influence order of the MCS was as follows: temperature> malic acid and starch mass ratio>pH> reaction time2.The properties of the prepared MCS were determined, the results were as follows:(1) the overall degree of whiteness of decreased with the increase of the degree of substitution. RVA and DSC results showed that:MCS of starch gelatinization viscosity with the increase of the degree of substitution decreases,when the DS reached a certain value, MCS did not gelatinize, it had high thermal stability and starch paste was easy to precipitate.(2)FT-IR result showed that there was a significant new characteristic peak in the carbonyl absorption bands of the1739 cm-1, which indicated that the esterification reaction did occur.(3) XRD patterns showed that when the degree of substitution of MCS is low, the crystal form of starch is similar to that of corn starch. With the increase of DS, the diffraction peak near 15.1°gradually disappeared, and this indicated that the reaction had a certain effect on the crystalline region of the starch.(4) With the increase of DS, thesurface of starch granule became rough and polarizing phenomenon gradually disappeared.3. Digestibility of MCS was analyzed,the results were that(1) the DNS method for determination of reducing sugar as: sample weigh 0.1 g, λ=540 nm, dosage of DNS 1.5 ml and in boiling water boil for 6 min.(2) with the increase of DS, the content of RS in MCS gradually increased. And the content of SDS and RDS decreased gradually. After boiling, the content of RDS and SDS increased, The reason was that the internal structure of starch was destroyed, the reaction point of completely exposed in solution and was suitable for amylase, which resulted that digested starch increased and digestion starch(RS) content decreased.4.The study of the effect of MCS on the flour products showed that : The water absorption of dough increased gradually and the dough development time,stability time and C2 decreased with the increase of adding amount of MCS.The addition of MCS diluted gluten protein, weakened the interaction between the protein, and influenced the formation of gluten network and extension. The properties of dough and the whiteness, specific volume, quality and structure features of steamed bread were better when the adding amount was 3%. Different degree of substitution of MCS had a certain effect on the dough rheological properties when the MCS addition was 3%. With the increase of substitution degree, the water absorption of dough increased gradually and the dough development time, stability time and C2 showed a trend of decline. |
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