| Cold storage is easy to cause the rearrangement of starch molecules,and the phenomenon of freeze-thaw cycle(FTC)occurs in the process of freezing because of the temperature fluctuation,which affects the physical and chemical properties of starch,and then causes the quality deterioration of frozen starchbased food and shortens its shelf life.In this paper,protein hydrolysates cooperating with hydrocolloids were added to rice starch to explore the effect of the complex on the retrogradation and freeze-thaw stability improvement of rice starch.The main objectives of this work were to investigate the effect of grass carp protein hydrolysates(GCSPHs)in combination with xanthan gum(XT)or guar gum(GG)on the retrogradation characteristics of rice starch(RS);investigate the synergistic effects of different plant protein hydrolysates(soybean protein hydrolysates,wheat protein hydrolysates,rice protein hydrolysates and corn protein hydrolysates)with xanthan gum on the short-term and long-term retrogradation of rice starch;investigate the synergistic effect of soybean protein hydrolysates and xanthan gum on the freeze-thaw stability of rice starch;investigate the synergistic effect of soybean protein hydrolysates and xanthan gum on the quality and low-temperature storage stability of rice sponge cake.The specific research results are as follows:1.The texture analysis showed that after GCSPHs-XT(GCSPHs cooperating with XT)were added into rice starch,the hardness decreased from 1181.8 g to249.3 g after stored at 4 ℃ for 14 days,and the hardness of RS/XTGCSPHs was lower than that of RS/GG-GCSPHs,indicating that GCSPHs-XT could inhibit the retrogradation of RS,and the inhibition effect of GCSPHs-XT on retrogradation of RS was stronger than that of GCSPHs-GG(GCSPHs cooperating with GG).On this basis,the mechanism of GCSPHs-XT inhibiting rice starch retrogradation was analyzed by differential scanning calorimetry,Xray diffraction,Fourier transform attenuated total reflection infrared spectroscopy,Low field nuclear magnetic resonance and scanning electron microscopy.It is found that GCSPHs-XT can form electrostatic interaction and hydrogen bond interaction with RS molecules,so as to significantly reduce the crystallization area of RS,increase the amorphous area of RS,delay the decrease of transverse relaxation time,inhibit the flow of free water,reduce the loss of water,form a more uniform continuous phase,and then slow down the retrogradation of RS.2.The results of pasting properties showed that the retrogradation values of RS/XT-SPHs,RS/XT-RPHs,RS/XT-WPHs and RS/XT-CPHs were significantly lower than those of RS,and RS/XT-SPHs was the lowest.The results show that SPHs-XT,RPHs-XT,WPHs-XT and CPHs-XT can inhibit the short-term retrogradation of RS,and SPHs-XT has the best inhibition effect.The results of dynamic viscoelasticity properties and pasting properties were shown that SPHs-XT increases the tangent of loss angle(tanδ)of RS gels,reduces the storage modulus(G’)of RS gels,indicating that SPHs-XT enhances the fluid properties of RS gels,thus inhibiting the short-term retrogradation of RS.In addition,after 14 days storage at 4 C,the quality of RS gel was further analyzed by texture,X-ray diffraction,differential scanning calorimetry,low field nuclear magnetic resonance and scanning electron microscopy.The results showed that compared with RS,SPHs-XT decreased the mobility of water molecules in RS gel system,and promoted the gel structure to form smooth thin layers and filaments,thereby reducing the hardness of RS/XT-SPHs from 1382.5g to 201.4 g,the relative crystallinity decreased from 18.18% to 8.15%,and the enthalpy of retrogradation decreased from 1.23 J/g to 0.96 J/g.It can be seen that SPHs-XT can not only inhibit the short-term retrogradation of RS,but also inhibit the long-term retrogradation of RS.3.The results of syneresis measurements showed that compared with RS,RS/XT,syneresis percentage of RS/SPHs and RS/XT-SPHs was obviously decreased.Among them,RS/XT-SPHs have the lowest syneresis percentage after each FTC.The results showed that XT,SPHs and SPHs-XT could improve the freeze-thaw stability of rice starch.And SPHs-XT has the best improvement effect.In addition,the results of texture and dynamic viscoelasticity showed that SPHs-XT decreased the hardness,gumminess and G’ of RS gel under different FTC times,increased its springness,cohesiveness and tanδ,indicating that SPHs-XT enhances the ability of RS to resist the adverse physical changes caused by FTC,improving the freeze-thaw stability of RS.Further,differential scanning calorimetry,low field nuclear magnetic resonance and scanning electron microscopy were used to explain the mechanism of SPHs-XT on improving the freeze-thaw stability of RS.The results showed that SPHs-XT reduced the retrogradation enthalpy,retrogradation rate and free water content of RS,inhibited the flow of water,and promoted appearance of the thin layer and filaments in the gel structure after FTC-3,5 and 7.The inhibitive effect of SPHs-XT on RS retrogradation and its strong water-locking function determine the improvement effect of SPHs XT on RS freeze-thaw stability.4.It can be found from the measurement results of texture characteristics that adding a certain amount of SPHs,XT and SPHs-XT can increase the springness and cohesiveness of rice sponge cake,and reduce the hardness and chewiness of rice sponge cake.Among them,SPHs-XT has the largest springness and cohesiveness,and the smallest hardness and chewiness.The results show that SPHs and XT can improve the texture properties of rice sponge cake,and SPHs-XT has better improvement effect.Furthermore,the effects of SPHs-XT on the quality of rice sponge cake were characterized by determination of specific volume and internal texture structure.The results showed that SPHs-XT significantly increased the specific volume,porosity and pore density of rice sponge cake,decreased the average pore area of rice sponge cake(P<0.05),showed that SPHs-XT could improve the quality of rice sponge cake.In addition,the effect of SPHs-XT on the stability of rice sponge cake during low temperature storage was also analysised by determination of texture properties.The results showed that SPHs-XT reduced the hardness and chewiness of rice sponge cake during low temperature storage,and increased the springness and cohesiveness of rice sponge cake.This shows that SPHs-XT can improve the storage stability of rice sponge cake which stored at low temperature.It should be proved that SPHs-XT can improve the retrogradation and freeze-thaw stability of RS. |
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