Effect Of Quality Improvers On The Storage Quality Of Instant Fresh Rice Noodle

Rice noodles as a traditional products were well received by consumers,but it is easy to go retrogradation during storage,which negative impact on the eating quality and shelf life of rice noodles.The main reason that affect the quality of rice noodle retrogradation(or storage)is starch retrogradation,but is not equal to the starch retrogradation,researches must be combined with starch retrogradation and cooking quality in order to fully describe the storage quality of rice noodle.This study based on starch retrogradation and rice noodles cooking quality,aims to clarify the effects of three quality improvers,hydroxypropyl distarch phosphate(HPDSP),soy protein isolate(SPI),transglutaminase(TGase),on the storage quality of instant fresh rice noodles,established the connection among additives amount,rice noodles retrogradaiton and storage quality,provides basic research data for application of quality improvers in the instant fresh rice noodles.First,the weight ratios in HPDSP/rice flour(RF)mixtures were 0%,5%,7.5%,10%,15%,long-term retrogradation of the instant fresh rice noodles was investigated by X-diffraction(XRD),differential scanning calorimetry(DSC),scanning electron microscope(SEM)and texture analyzer,the storage cooking quality of instant fresh rice noodles was investigated by determining the cooking loss and breaking rate of rice noodles in 4 ?,3,7,14,28 days storage,the results are as follows: HPDSP can significantly inhibited rice noodles retrogradation,decreased starch retrogradation characteristic peak intensity and the degree of crystallinity,decreased rice retrogradation enthalpy;The effect of different contents of HPDSP on rice noodles crystallinity,retrogradation enthalpy are significantly different(P<0.05),and with HPDSP contents increased,the inhibition of rice noodles retrogradation was enhanced,when HPDSP/rice flour was 15%,compared with the blank sample,the crystallinity of HPDSP/RF reduced from 10.17±1.54 to 2.22±0.51,retrogradation enthalpies reduced from 4.58±0.21(J/g)to 1.28±0.61(J/g),which was the best inhibition effect;Microstructure showed that rice noodles contained HPDSP were a porous honeycomb structure,with a large number of cavities;The hardness result further demonstrated HPDSP improving the flexible of rice noodles,and had retrogradation inhibition effect..Quality changes in storage was investigated by cooking quality.HPDSP amounts in the 0~10% range,the breaking rate and cooking loss of rice noodles decrease with the increase of amount.15% HPDSP amount remarkably damages the rice cooking quality.Although the retrogradation index shows that 15% HPDSP has optimal effect of antistaling,but combined with the rice quality,HPDSP amounts should be limit when it used in the industrial production.Second,the weight ratios in SPI/RF mixtures were 0%,2%,3%,4%,6%,the short-term retrogradation of the instant fresh rice noodles was investigated by Brabender-E viscograph(RVA),long-term retrogradation was investigated by Xdiffraction(XRD),differential scanning calorimetry(DSC),scanning electron microscope(SEM)and texture analyzer,the storage cooking quality of instant fresh rice noodles was investigated by determining the cooking loss and breaking rate of rice noodles in 4 ?,3,7,14,28 days storage,the results are as follows: SPI could significantly decrease peak viscosity,breakdown,final viscosity and Setback of SPI/RF system,inhibit the swelling of starch granules and short-term retrogradation;4 ?,7 days storage experiment showed that SPI could significantly inhibit recrystallization of rice noodles,reduced retrogradation enthalpy,inhibited the longterm retrogradation of rice noodles and the inhibitory effect significantly enhanced with the SPI content increased.When SPI/RF was 6%,compared with the blank sample,the crystallinity of SPI/RF rice noodle reduced from 9.53±0.43 to 3.36±0.30,retrogradation enthalpies reduced from 3.77±0.10(J/g)to 1.82±0.07(J/g);Microstructure of SPI/RF rice noodle was a hole-like network structure,showed that SPI could improve the water-holding ability of rice noodles in storage period;4?,3-28 days hardness results further proved SPI could inhibit retrogradation of instant fresh rice noodles in storage,reduced rice noodles hardness,the 6%(w/w)had the best inhibition effect.Monitoring rice noodles cooking qualities at 4?,3-28 days storage,found that when soybean protein isolate addition content in 0-4%,the cooking loss and breaking rate of rice noodles were decreased with SPI content increasing,6% SPI increased the cooking loss and breaking rate.These results showed that SPI could significantly inhibit the retrogradation of rice noodles in the storage,but adding excessive amounts of protein would damage to the edible quality of rice noodles.Third,adding different weight ratios(0%,0.03%,0.05%,0.1%,0.3%)TGase to rice flours,the short-term retrogradation of the instant fresh rice noodles was investigated by Brabender-E viscograph(RVA),long-term retrogradation was investigated by differential scanning calorimetry(DSC),scanning electron microscope(SEM),the storage cooking quality of instant fresh rice noodles was investigated by determining the cooking loss and breaking rate of rice noodles in 4 ?,3,7,14,28 days storage,the protein network was investigated by SDS-PAGE,the results are as follows: TGase had no significant effect on TGase/flour pasting properties,had slight impact on the short-term retrogradation;DSC results showed that TGase inhibited the long-term retrogradation of rice noodles.When TGase content below 0.1%,the effect of TGase inhibit long-term retrogradation enhanced with the content of enzyme increased,when TGase added up to more than 0.1%,there is no significant different between samples(P>0.05);Microstructure of TGase samples showed a porous honeycomb structure,which means that the TGase could improve the water holding capacity of rice noodles in storage period.Monitoring the cooking quality of rice during storage found when TGase content below 0.1%,the breaking rate and cooking loss of rice noodles reduced with TGase content increased;When TGase content up to 0.1%,the effect of reduing breaking rate reached balance,but cooking loss always significantly more than blank sample.Protein content in rice is low,the substrate concentrations limited was the reason that TGase improvement reached a bottleneck when the content up to 0.1%.Electrophoresis results showed that TGase treatment promoted a decrease in the intensity of 55,63 kDa bands,and produced a new band at the 180 kDa,the new bands intensity were increased when the TGase content above 0.1%.This further proved TGase could affect rice noodle storage quality by crosslinking rice proteins in rice flours.