The Investigation Of Lamellar Structural Model And Anti-Retrogradation Mechanism Of Canna Starch

With the development of economic globalization and improvement of people’s living level,more colorful,convenient semi-manufactured or finished products are being the favorite for humans,and they are taking instead of traditional cooking raw materials.Most of these products are of starch system,and will be retrograded with hard texture,loose tissue,rough skin and low elasticity after storage.Retrogradation study has been carried out for a long time,however,most of them are limited on crop starch not tuber starch.Canna edulis Ker,is an important economic,low-carbon agriculture product,which contains over 66%starches in their rhizome.However,the fundamental research on the canna starch are restricted to chemical modification and simple physicochemical characterization.The effect of lamellar structure on the physicochemical properties of starch with the aid of SAXS is still the hot-spot and difficulty of the present study.Therefore,this study focus on the lamellar structure and anti-retrogradation mechanism of degraded canna starch,and the main research contents are as follows:Firstly,the physicochemical and structural differences of the six tuber starches were compared.The results show that canna starch has amylose content of 30.88%,crystallinity of 22.18%,and is a traditional B-type starches.Within the six tuber starches,canna starch has the highest WSI（17.83 g/100g）,the second highest SP（20.83 g/g）,and the lowest gelatinization temperature.The paracrystalline model fitting demonstrates that canna starch and the other two B-type starches（potato and lotus root）are not satisfactorily fit,which was attributed to their high amylose content.High amylose starches are likely to be more stable and will tolerate less decoupling from the backbone due to their shorter amylose tie-chains.This structure leaves little room for compression across the lamellar structure,and therefore,overall layer bending must occur to accommodate internal stresses.Then,the limitation of paracrystalline model on the fitting of B-type starches lead to the application of two-phase lamellar model and one-dimensional correlation function.Both A-and B-type starches fit well with the two models（r²>0.99）.Compared with paracrystalline model,one-dimensional correlation function could be adapted to all kinds of starches;compared with two-phase lamellar model,it can supply more information of starch lamellar structure.It is easy to distinguish between A-and B-type starches via one-dimensional correlation function,as B-type starches always have lower value of E and R_g compared with A-type starches,demonstrating that the transition of B-type starches are sharper.After the lamellar structure was established,canna starch based anti-retrogradation starches were prepared and characterized.The results show that thermal degradation perfected the starch crystal via plastication,while enzymatic degradation by preferential hydrolysis.After thermal degradation,the edges of canna starch granules were gelatinized in the samples of 60-TDCS.Fortunately,Maltese-cross were still existed,demonstrating that a mild treatment conducted.Compared to NCS,samples of TDCS has a higher heat/enzyme stability and short-range ordering.Enzymatic degradation has even more severe destruction on the starch granules.This process formed a sponge-like structure（numerous radial pores）at the initial stage of hydrolysis,and fragmentation occurred at the final stage.As the hydrolysis progressed,the transition between crystal and amorphous regions becomes diffused,with an increased d,E,and a decrease of?_??.Importantly,α-amylase could relieve the destruction of heat on the long-range ordering and stimulate the increasement of short-range ordering.Finally,the anti-retrogradation mechanism of TDCS and EDCS were tentatively discussed.The results show that samples of TDCS has a higher anti-retrogradation effect than that of EDCS.Latent variable-structure was obtained by scoring of the four lamellar structure parameters,while the latent variable-retrogradation was obtained by scoring of the six retrogradation index,by using the PLS algorithm,the anti-retrogradation prediction model was established.The model concludes that structure correlates well with retrogradation,providing scientific basis for the starch retrogradation prediction.In this paper,the physicochemical and structural properties of canna starch were compared with other tuber starches,and the limitation of paracrystalline model in B-type starches were found.Thereafter,one-dimensional correlation function was constructed and applied in the process of thermal and enzymatic degradation.Moreover,the anti-retrogradation mechanism of the degraded starches was also tentatively established,which has characteristics of representativeness,easily obtained,sensitive response of physicochemical properties,and is expected to be applied in the field of physicochemical,especially retrogradation prediction.