Study On Browning Inhibition And The Mechanism Of Fresh Wet Noodles

Fresh wet noodles have the advantages of freshness,refreshing taste,and chewiness.Due to the relatively higher water content in fresh wet noodles,they undergo browning during storage,resulting in the darkening of the noodles and the formation of dark spots.In South China,sodium carbonate or potassium carbonate is typically added during the production of fresh wet noodles,which exacerbates the degree of browning.The deterioration of the appearance of fresh wet noodles significantly affects consumer choices and hinders sales.This study explored the influencing factors of browning in fresh wet noodles.SHMP,dihydrogen phosphate,and ascorbic acid were used to improve the browning,and their mechanisms were investigated in depth.Firstly,the effects of PPO,sodium carbonate,phenolic compounds,and gluten proteins on the browning of fresh wet noodles were investigated.The degree of browning in fresh wet noodles increased with the increase in PPO activity in the wheat flour.After inhibiting PPO activity with tropolone,the formation of dark spots in fresh wet noodles was completely suppressed.The addition of sodium carbonate aggravated the browning of fresh wet noodles,with the most severe browning observed at 0.3% of sodium carbonate,resulting in a decrease of 3.21 in L* value compared to the sample without sodium carbonate.The addition of different phenolic compounds was found to intensify the browning.When catechol and gallic acid were added at a concentration of 0.03%,the L* values decreased by 18.67 and 7.87,respectively,while ferulic acid resulted in a brighter color of fresh wet noodles.The addition of glutenin and gliadin to fresh wet noodles led to an increase in L* value from 75.68 to 78.37 and a decrease in L* value to 73.40,respectively.Next,the effects and mechanisms of SHMP on the browning of fresh wet noodles(with0.3% of sodium carbonate)were studied.With an increase in the addition of SHMP,the color of fresh wet noodles became brighter.Specifically,the sample with 0.5% of SHMP showed an increase of 4.32 in L* value,and it significantly inhibited the number and area of dark spots(p<0.05),reducing the number of dark spots from 627 to 12.The mechanism of SHMP on browning was explored using PPO solution and PPO-catechol system.The results demonstrated that SHMP could significantly inhibit PPO activity(p<0.05),with a reduction of 80% in PPO activity when added at 0.5%.SHMP was found to inhibit PPO activity by chelating the copper ions in the active center of PPO,and this inhibitory effect was irreversible.HPLC analysis revealed that SHMP reduced the formation of browning products,leading to a lighter color.HPLC and MS results showed that SHMP could inhibit the auto-oxidation,converting melanin(m/z 248.97,723.50,836.58)to lighter substances(m/z 137.11).Additionally,the effects and mechanisms of dihydrogen phosphate on the browning of fresh wet noodles were investigated.With an increase in the addition of sodium dihydrogen phosphate and sodium hydrogen phosphate(0% to 0.5%),the color of fresh wet noodles became brighter.Specifically,when the addition was 0.5%,the L* values increased 2.79 and 2.05,respectively,and the number of dark spots decreased from 627 to 127 and 109.The mechanism of dihydrogen phosphate on browning was studied,and the results showed the following: the addition of these phosphates could reduce PPO activity in fresh wet noodles,possibly due to the decrease in p H and chelation of copper ions;sodium dihydrogen phosphate enhanced the ability of ferulic acid to scavenge DPPH free radicals;sodium dihydrogen phosphate inhibited the increase of protein carbonyl content in fresh wet noodles,promoted the formation of hydrophobic interactions between proteins,and disrupted hydrogen bonding between proteins,indicating that sodium dihydrogen phosphate suppressed protein oxidation and structural changes in fresh wet noodles.Finally,the effects and mechanisms of the combination of 0.012% of ascorbic acid(Vc)and 0.5% of phosphates(SHMP,sodium dihydrogen phosphate,sodium hydrogen phosphate)on the browning of fresh wet noodles were studied.The combination of Vc and phosphates did not show further improvement in browning compared to using Vc or phosphates alone.However,when compared to the individual addition of Vc or s dihydrogen phosphate,the combination showed a synergistic effect in inhibiting browning,leading to further improvement in the color of fresh wet noodles.The noodles appeared brighter,with an increase of 1.77 and2.43 in L* value,and the number of dark spots decreased from 127 and 109 to 10 and 4,respectively.Compared to the individual use of the three phosphates,the combination of phosphates and Vc did not further reduce PPO activity,but it significantly reduced the content of quinones in fresh wet noodles(p<0.05).Measurement of the antioxidant capacity of Vc in the PPO-catechol reaction system showed that in the system without dihydrogen phosphate,Vc had a DPPH radical scavenging rate of 20%,while in the presence of dihydrogen phosphate,the DPPH radical scavenging rate of Vc increased to 95%,indicating that dihydrogen phosphate maintained the antioxidant activity of Vc.Additionally,quantum chemical calculation results indicated that the hydroxyl group of dihydrogen phosphate formed hydrogen bonds with the hydroxyl group on the carbon-carbon double bond of Vc,suggesting that the formation of hydrogen bonds might protect the antioxidant activity of Vc.