Quality Improvement And Shelf Life Extension Of Dried Whole Wheat Noodles

Dried whole wheat noodles（DWWN）are in line with consumers’pursuit of a healthy eating style and balanced dietary structure,and the consumer market is broad.However,DWWN has poor taste,and the raw materials are rich in unsaturated fatty acids,lipase and lipoxygenase activity is high,so DWWN is prone to rancidity easily during storage.For this reason,this project selects nine different varieties of wheat flour and adds bran to prepare reconstituted whole wheat flour（WWF）,exploring the effect of different reconstituted WWF on the quality of DWWN,and improving its foaming resistance by adding exogenous protein and enzymes.In addition,the co-extrusion treatment of chelating metal ions was used to inhibit lipid oxidation during storage of DWWN,to provide a theoretical basis for the industrial production of DWWN.First,nine different varieties of wheat flour were selected and added with bran to obtain different reconstituted WWF,and the effects of different reconstituted WWF on the quality of DWWN were analyzed.Among the 9 selected different varieties of wheat,the sensory evaluation score of DWWN prepared by AH was significantly higher than others（p<0.05）,and the foaming resistance was better.The tensile strength and elasticity were 6.66 g and 18.71 mm,respectively.Correlation analysis found that the protein content of WWF was significantly positively correlated with the breaking strength,hardness,chewiness,tensile strength,hardness after soaking,chewiness after soaking,and tensile strength of DWWN after soaking（p<0.01）,showing a very significant negative correlation with the cooking loss of DWWN（p<0.01）;the wet gluten content of WWF was significantly positively correlated with the hardness,chewiness,and tensile strength of DWWN after soaking（p<0.01）;GMP content of WWF was significantly positively correlated with the breaking strength and the chewiness of DWWN after soaking（p<0.01）.The total starch content of WWF was significantly positively correlated with the breaking strength of DWWN（p<0.05）,and was significantly positively correlated with the hardness and chewiness of DWWN after soaking（p<0.05）.The amylose/amylopectin ratio of WWF was significantly negatively correlated with the chewiness of DWWN（p<0.05）.WWF with protein content higher than 14%,wet gluten content higher than 25%,high total starch content,and low amylose/amylopectin ratio is more suitable for making DWWN.Secondly,the effects of adding exogenous protein and enzymes on the quality of DWWN were studied respectively.Adding an appropriate amount of exogenous protein can significantly reduce the cooking loss of DWWN（p<0.05）.The cooking loss is the lowest when the additions of gluten and whole egg liquid are 2%and 10%,respectively.The cooking loss of DWWN is no longer reduced when the addition of whole egg liquid exceeded 10%.Adding exogenous protein can improve the foaming resistance of DWWN.When 2%gluten is added,the hardness after soaking is 23.11%higher than that of the blank group,and the elasticity after soaking is25.17%higher than that of the blank group.When the amount of whole egg liquid is 10%,the hardness after soaking is 28.83%higher than that of the blank group,and the elasticity after soaking is 35.27%higher than that of the blank group.Adding an appropriate amount of exogenous protein can significantly increase the content of free sulfhydryl and disulfide bonds in DWWN（p<0.05）.SDS-PAGE results showed that the addition of whole egg liquid promoted the formation of macromolecular protein subunits.The addition of exogenous protein makes the protein network structure more dense by promoting the covalent cross-linking of protein,thereby improving the foaming resistance of the DWWN.When the addition amount（w/w）of TG enzyme,laccase and glucose oxidase is 2‰,1‰,and 2‰,it can effectively improve the foaming resistance of DWWN.When the addition amount of TG enzyme is 2‰,the improvement effect of foaming resistance is the best,the hardness after soaking is 21.03%higher than that of the blank group,and the elasticity after soaking is 21.91%higher than that of the blank group.The result of SDS-PAGE showed that adding an appropriate amount of enzyme could reduce the small molecular weight protein subunits,increase the macromolecular protein subunits,and deepen the degree of protein cross-linking,thereby improving the foaming resistance of DWWN.Then,the compound use of 10%whole egg liquid and 2‰TG enzyme significantly reduced the cooking loss of DWWN（p<0.05）,in addition,the foaming resistance of DWWN has also been improved,and the hardness after soaking is 35.92%higher than that of the blank group,and the elasticity after soaking increased by 35.38%compared with the blank group.Finally,the effect of metal ions chelation on lipid stability during storage of DWWN was investigated.Adding Fe SO₄ could accelerate the rancidity of DWWN while adding EDTA could significantly inhibit the peroxidase activity（p<0.05）.Chelating metal ions have significant effects on the shelf life,fatty acid value,fatty acid composition,and volatile components of DWWN during storage（p<0.05）.The increase in fatty acid value（54%,52%）of DWWN added with phytic acid and EDTA after accelerated storage for 9 weeks was much lower than that of other groups,the content of n-hexanal and 2-pentylfuran was lower,and the content of linoleic acid（7.46 mg/g,7.45 mg/g）were also higher than other groups.The shelf life of DWWN was prolonged by 3 weeks and 4 weeks,respectively.In conclusion,at low enzyme activity levels,metal ions can significantly promote the lipid oxidation of DWWN（p<0.05）,and chelating metal ions can effectively improve the lipid stability of DWWN during storage.