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Professor Chen Fusheng of Henan University of Technology, et al.: Application of alkaline salt in fresh wet noodle preservation and quality control

 Last Update: 2022-11-14
 Source: Internet
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Fried instant noodles and low-moisture noodles are popular
for their low moisture content, long shelf life, and ease of consumption.
However, the long-term drying and dehydration process will make the hanging noodles taste poor, the wheat aroma is insufficient, and the quality is reduced
.
The high-temperature frying process not only greatly reduces the flavor, texture and nutritional properties of the noodles, but also may produce toxic and harmful substances
such as acrylamide.
On the contrary, as the traditional form of Chinese noodles, raw wet noodles have always been favored
by consumers because of their smooth taste, rich nutrition and strong noodle aroma, which is more in line with the "green, healthy and convenient" consumption concept pursued by the contemporary public.
At present, the most serious production problem facing fresh wet noodles is the short shelf life, which seriously hinders large-scale industrialization
.

In the preliminary study, the raw noodles were made using the alkaline salt allowed by fresh flour products in GB 2760-2014 "Food Additive Use Standard", and the total number of colonies after 24 h storage at room temperature was detected, and finally five alkaline salts (sodium carbonate, potassium carbonate, trisodium phosphate, tripotassium phosphate and sodium bicarbonate) with obvious antibacterial effect were finally screened for follow-up research
。 Tian Yu, Liu Boye*, Chen Fusheng* and other students from the College of Cereals, Oils and Foods of Henan University of Technology systematically studied the inhibitory effect of different alkaline salts (sodium carbonate, potassium carbonate, trisodium phosphate, tripotassium phosphate and sodium bicarbonate) on microorganisms in fresh wet noodles, and compared the effects of different alkaline salts on the rheological characteristics of dough, noodle quality characteristics (such as cooking characteristics, texture characteristics, sensory quality) and internal microstructure during storage, so as to provide reference value
for alkaline salt in the research and quality improvement of fresh wet noodles.

1.
Effect of alkaline salt on the total number of colonies of fresh wet noodles

As shown in Figure 1, the total number of colonies in all samples showed a rapid growth trend
during storage.
When stored for 24 h, the total number of colonies in the control group was close to the detection threshold, and when stored for 36 h, the total number of colonies reached 6.
82 (lg (CFU/g)), which had no edible value
.
In the same storage time, the total number of colonies in the experimental group was always lower than that of the control group, among which sodium carbonate had the best antibacterial effect on fresh wet noodles, and the effect of tripotassium phosphate and sodium bicarbonate was relatively poor, which may be caused by the different effects of alkaline salt on the pH value of noodles and the influence of metal salt ions on the internal charge and structure of noodles, which in turn made the storage stability of fresh wet noodles different
。 In addition, the shelf life of fresh wet noodles with 2.
0% sodium carbonate was 1.
5 times that of the control group (24 h), and the shelf life of the remaining four alkaline salts (the addition amount was 1.
5% and 2.
0%) was 36 h, but the growth trend was slightly different, indicating that the addition of alkaline salts significantly inhibited the growth of microorganisms, and its bacteriostatic effect was related
to the type, amount and ionic strength of alkaline salts.

2.
The effect of alkaline salt on the L* value of fresh wet noodles

As can be seen from Figure 2, the L* value of the control group first decreased and then increased, which was due to the browning reaction of the noodles in the early stage of storage, and its surface brightness became darker.
After storage for 24 h, microorganisms continued to multiply, resulting in the disintegration of the noodle matrix, loose structure, and changes in the diffuse reflection and absorption of light by noodle molecules, which in turn caused the L* value to increase back, and the re-increase time of L* value in all experimental groups was later than that in the control group, indicating that the addition of alkaline salt could delay the rate
of destruction of the noodle structure.
At the beginning of storage (0 h), sodium ions and carbonate ions can increase the brightness value
of noodles.

3.
The effect of alkaline salt on the apparent state of fresh wet noodles

As shown in Figure 3, the apparent state of the control group decreased significantly during storage, which was due to the browning reaction of the noodles, the rejection of the noodle substrate, the production of sour odor, the weakening of water binding, the migration of more free water to the surface of the noodles, the brightness became darker, and it was easier to break and stick
。 However, the apparent state score of the experimental group was higher, indicating that the addition of alkaline salt effectively delayed the deterioration rate of noodles, and its apparent state could still be maintained well in the late stage of storage, which was due to the fact that alkaline salt could induce the endogenous flavonoid substances in natural wheat flour to undergo chromogenic displacement in alkaline environment, and open the ring to form a chalcone structure, thereby showing a bright yellow appearance and being more attractive.
The introduction of alkaline salt can strengthen the binding degree of water in the noodles with other non-aqueous components, so that the surface of the noodles is dry and not easy to stick.

In the early stage of storage (0 h), the apparent state score of the experimental group was low, which was due to the addition of alkaline salt to make the noodles emit an unacceptable alkaline odor, and in the late storage period, the "alkaline" taste dissipated and the apparent state tended to be stable
.
According to the above study, taking into account the cost consumption and consumer acceptance, the amount of alkaline salt added in the follow-up study was selected: sodium carbonate was 1.
0%, potassium carbonate, tripotassium phosphate, trisodium phosphate and sodium bicarbonate were all 1.
5%.

4.
The effect of alkaline salt on the pH value of fresh wet surface

As shown in Figure 4, the pH value of all samples showed a downward trend, the pH value of the control group decreased from 6.
04 to 5.
21 within 72 h of the storage time, the pH value of the experimental group was always in the alkaline range, and the pH value of the sample with 1.
0% sodium carbonate decreased from 9.
82 to 8.
78, the decrease was the smallest, which indicated that the addition of sodium carbonate could make the fresh wet surface matrix more stable, which may be due to the rearrangement/bonding of starch molecular chains caused by alkali treatment, which enhanced the ordered molecular structure of long and short chains.
Moreover, there is an electrostatic interaction between the metal ions introduced by the alkaline salt and the starch hydroxyl group, and the hydroxide ions in the alkali solution will enhance the bonding force in the starch granule components, thereby enhancing the stability of the starch granule.
In addition, Li Man et al.
have shown that noodle pH can effectively delay the spoilage
of noodles when the pH value is lower than 6 or greater than 9.
This shows that the higher the pH value of the noodles, the more stable its state, the slower the growth of microorganisms, the difference in pH value between the experimental groups is because of the different types of alkaline salts, different alkaline salts in the form of electrolysis in water electrolytic forms are different, the degree of ion after electrolysis and starch and protein binding degree is different, which in turn will lead to changes in the structure of gluten protein and starch components, Bharti et al.
found that with the gradual increase of alkali concentration, the decomposition of alkali-modified mango kernel starch is significantly reduced (P<0.
05).
<b11> 。 Within 12 h before storage, the pH values of noodles from low to high were the control group, sodium bicarbonate, tripotassium phosphate, sodium carbonate, trisodium phosphate and potassium carbonate, and the change trend was very significantly correlated with the change of the total number of colonies (P<0.
05); after 24 h of storage, the pH value of sodium carbonate experimental group gradually exceeded that of trisodium phosphate and potassium carbonate, and the growth rate of the total number of colonies of fresh wet noodles remained unchanged, which indicated that the inhibitory effect of alkaline salt on microorganisms in noodles was manifested in the regulation of the pH value of the noodle matrix and the salt-soluble effect of salt ions.
Strengthen the gluten network and strengthen the internal structure<b12> of the noodles.

5.
Effect of alkaline salt on the rheological properties of dough

As shown in Table 2, compared with the control group, the addition of five alkaline salts significantly increased the water absorption rate of dough, except for sodium bicarbonate, the remaining four alkaline salts all shortened the stability time and formation time of dough to varying degrees, because alkaline salt can speed up the formation rate of gluten, participate in water competition, and increase dough water
absorption 。 Sodium bicarbonate significantly prolongs the stability time and formation time of dough, which is due to the decomposition of bicarbonate ions in water, the ionization balance between carbonate ions and bicarbonate ions, so that it binds slowly to gluten protein, the stability time and formation time are extended, and the salt solubility of metal ions can strengthen the gluten structure, enhance the elasticity and kneading resistance of the dough, and improve
the flour characteristics of the dough.
In addition, alkaline salts reduce the weakening of dough, and the improvement effect of carbonate ions on the powder characteristics of dough is better than that of phosphate ions, and sodium ions are better than potassium ions
.
It can be seen from Table 3 that when the dough proofing time is 45 min and 90 min, the maximum tensile resistance of all samples increases and the ductility decreases, indicating that with the extension of the proofing time, the dough gluten network continues to form and is more resistant to stretching.
When the proofing time is 135 minutes, the stretching properties of the dough decrease, because the dough proofing time is too long, the dough becomes soft and the strength decreases
.
Compared with the control group, the maximum tensile resistance of the dough in the experimental group was increased, and the dough elongation decreased except for sodium bicarbonate, indicating that the dough was more tough, resistant to stretching, not easy to rheologize, and elastic increased
.
Therefore, alkaline salt is able to increase the strength of the dough and improve the tensile properties
of the dough.
In summary, the influence of alkaline salt on the rheological properties of dough mainly depends on the type and amount of alkaline salt added, on the one hand, metal salt ions can promote the formation of gluten network and enhance gluten strength; On the other hand, acid ions change the acid-base environment of the noodle matrix, dissolve some starch particles and protein molecules, and cause changes in the rheological properties of dough
.

6.
Effect of alkaline salt on the cooking quality of fresh wet noodles

As shown in Figure 5, compared with the control group, the cooking loss in the experimental group increased significantly because a small amount of alkaline salt was dissolved during the cooking process, resulting in an increase in the pH value of the boiling water, leaching of amylose, and an increase in the solubility of water-soluble protein.
During the heating process, alkaline salt induces rapid polymerization of noodle gluten network, while starch gelatinization expansion rate is slow, so that the starch particles after water absorption expansion are difficult to embed into the gluten network, resulting in an increase
in the dissolution rate of starch particles 。 In addition, with the extension of storage time, the cooking loss of all samples increased, which may be due to the hydrolysis of endogenous hydrolytic enzymes (protease, α-amylase, etc.
) in flour and microbial metabolism during storage, that is, the use of the main nutrients in the noodles, namely starch and protein, to continuously carry out fermentation type acid production, so that the noodle matrix collapses, the gluten network structure is destroyed, resulting in more noodle fragments being brought into the
noodle soup during the cooking process.

7.
Effect of alkaline salt on texture characteristics of cooked noodles

It can be seen from Table 4 that with the extension of storage time, the hardness of the control group decreases, while the hardness of the noodles in the experimental group increases, indicating that the noodles in the control group are easy to spoil, the pH value drops rapidly, the noodle structure is seriously damaged, and the hardness decreases, while the alkaline salt can participate in the formation process of the noodle structure, so that the starch particles are more tightly wrapped in the gluten network, enhance the stability of the noodle structure, compete for limited moisture, and improve the hardness
of the noodles.
The harder noodles were more chewy, and the noodles in the experimental group were more
chewy.
During storage, the cohesion of the experimental group was always maintained at a high level, and the elasticity of the experimental group was significantly higher than that of the control group
in the later stage of storage.
It can be seen from Figure 6 that in the early stage of storage, except for sodium bicarbonate, the tensile breaking distance and maximum tensile strength of all experimental groups were significantly higher than those of the control group
.
During storage, the tensile properties of all samples continued to decrease, indicating that the noodle structure was destroyed, which was due to the endogenous enzymatic hydrolysis in flour and the depletion of nutrients in noodles by microbial metabolism, which destroyed the protein-starch network structure
in noodles.
In addition, noodles with potassium carbonate have the highest hardness value, the highest tensile strength, and the elasticity is closer to fresh noodles; However, the hardness value of noodles with the addition of tripotassium phosphate and sodium bicarbonate is relatively low.
Noodles with 1.
5% trisodium phosphate, tripotassium phosphate and sodium bicarbonate with a maximum tensile strength of less than 1.
0% of the added amount
of sodium carbonate noodles.

8.
Effect of alkaline salt on the sensory quality of fresh wet noodles

It can be seen from Table 5 that in the early stage of storage, the quality of noodles is better, compared with the control group, the color, elasticity, palatability, taste, viscosity and total score of the experimental group are significantly improved, because the alkaline salt is conducive to enhancing the gluten structure, making the noodles more elastic and chewy, and the taste is smooth and non-sticky
.
The smoothness of the experimental group showed no significant decrease due to the rough surface of the noodles due to the increased cooking loss
.
After 24 h of storage, the scores of the control group decreased, and the total score was lower than 60 points, because the growth of microorganisms damaged the noodle structure and the sensory quality decreased.
The sensory score of the experimental group was higher, indicating that alkaline salt could improve the sensory quality of
noodles.
The sensory score of noodles with sodium carbonate was the highest, and the palatability and smoothness of noodles with trisodium phosphate and potassium carbonate were poor, which may be because alkaline salt overly strengthened the gluten structure of noodles, resulting in excessive hardness and cooking loss of noodles.
The experimental group with sodium bicarbonate and tripotassium phosphate had lower scores in terms of color and taste because its inhibition effect on microorganisms in noodles was weak and the noodle structure was damaged
.
As can be seen from Figure 7, compared with the control group, the addition of alkaline salt can make the noodles have a bright light yellow appearance, and different alkaline salts have different degrees of influence on the color of the noodles, and sodium carbonate has a greater
effect on the color of the noodles.

9.
Effect of alkaline salt on the microstructure of fresh wet noodles during storage

As shown in Figure 8, the freshly made noodles had obvious large holes inside the control group, and obvious starch grain shedding, the surface of sodium carbonate and sodium bicarbonate showed a continuous gluten network structure, the starch particles were evenly distributed, dense, the gluten network structure was complete, and the surface was smooth; The potassium carbonate and trisodium phosphate experimental groups were able to see that the small holes and trace starch particles fell off due to the rapid formation of a strong gluten network during dough formation, resulting in fewer surface connections, which further explained the increased
cooking loss of alkaline noodles during the cooking process.
There was no significant exposure of starch particles in the tripotassium phosphate experimental group, which indicated that compared with the control group, alkaline salt caused the gluten network to tend to be membranous, more closed, and less ditched, forming a stronger and more resistant gluten network structure, which can wrap more starch particles and make the components tightly
bound.

Conclusion

The addition of alkaline salt can effectively inhibit the proliferation of microorganisms in noodles and delay the spoilage rate of noodles, among which sodium carbonate is more conducive to regulating and maintaining the alkaline environment of fresh wet noodles, which is more effective in extending the shelf life of noodles, and 2.
0% sodium carbonate can extend the shelf life of fresh wet noodles from 24 h to 60 h
.
Based on the analysis of the preservation effect and apparent state of alkaline salt on fresh wet noodles, the addition amount of sodium carbonate was 1.
0%, and the addition of potassium carbonate, trisodium phosphate, tripotassium phosphate and sodium bicarbonate was 1.
5% as the optimal addition level
.
In addition, alkaline salt can improve the apparent state of noodles, give a light yellow appearance, make the surface dry and non-sticky, increase the attractiveness of raw wet noodles, improve the hardness and tensile strength of noodles, improve the texture characteristics of noodles, and enhance sensory quality, mainly in improving the elasticity, viscosity, palatability and taste
of noodles.
The addition of alkaline salt significantly enhanced the degree of cross-linking of gluten and starch, and the structure of gluten network was dense, among which sodium carbonate had the best effect on improving the quality of fresh wet noodles, the cooking loss was relatively small, and the water absorption rate and sensory score were relatively high
.

About the corresponding author

Chen Fusheng, male, born in 1963, professor (second level), Ph.
D.
/master tutor, vice president
of Henan University of Technology.
He has won the titles of National Model Teacher, National Talent Project Candidate, National Young and Middle-aged Experts with Outstanding Contributions, Experts Enjoying Special Government Allowances of the State Council, and Academic and Technical Leaders of Henan Province; He is the leader of the outstanding scientific and technological innovation team of Henan Province, the winner of the Henan Outstanding Talent Innovation Fund, and the winner of the Henan Outstanding Scientific Research Talent Innovation Project Fund for Colleges and Universities
.
He has presided over 33 projects such as the "13th Five-Year Plan" National Key R&D Program (Chief), the National "863" Program, and the National Natural Science Foundation of China; He has won 21 science and technology awards, including 1 second prize of National Science and Technology Progress Award and 8 provincial and ministerial science and technology progress awards; He has published 386 academic papers in important journals at home and abroad, including 108 papers included in SCI and EI; published 13 books; He has applied for 38 national invention patents, including 23 authorized invention patents
.
It has trained 119 postdoctoral fellows, doctoral and master students
.

Liu Boye, lecturer of the College of Cereals, Oils and Foods of Henan University of Technology, member of the Communist Party of China, doctor, selected as the Henan Province Young Talents Sponsorship Project, the "Wisdom Zhengzhou ▪1125 Talent Gathering Program" innovation and entrepreneurship leading team and the young backbone teacher of Henan University of Technology, taught in the Department of Oleooil Engineering, College of Grain, Oil and Food of Henan University of Technology in
2017 。 During his work, he won the honorary titles of Arowana Young Teacher Award and Teaching Grant, "Challenge Cup" Henan Province College Student Entrepreneurship Plan Competition Outstanding Instructor and school-level excellent class teacher; Guide undergraduates to participate in the 2020 "Challenge Cup" Henan Province College Student Entrepreneurship Plan Competition, the 2021 "Challenge Cup" Henan Province College Students Extracurricular Academic Science and Technology Works Competition and the 7th China International "Internet +" College Student Innovation and Entrepreneurship Competition, and won the provincial special prize, the provincial second prize and the provincial third prize
respectively.
At present, he has presided over projects such as the National Natural Science Foundation of China Youth Science Fund, Henan University of Technology High-level Talents Scientific Research Start-up Fund Project, Henan University of Technology Undergraduate Education Teaching Reform Research and Practice Project, and Zhengzhou Haite Machinery Co.
, Ltd.
Horizontal Project
.
He has published 40 papers in major academic journals at home and abroad, including 6 SCI papers, 1 EI paper and 1 education reform paper as the first author or corresponding author, and 10 authorized invention patents
.

About the first author

Tian Yu, 2020 master student of protein processing theory and technology team of the College of Cereals, Oil and Food of Henan University of Technology, graduated from Henan University of Technology with a bachelor's degree, the main research direction: the application of alkaline salt in flour products and the research of preservation mechanism, won the excellent graduate pacesetter, excellent student cadre, has published 1 EI article
.

This article "Application of alkaline salt in the preservation and quality control of fresh wet noodles" is from Food Science, Vol.
43, No.
16, pp.
26-35, 2022, authors: Tian Yu, Liu Boye, Chen Fusheng, Cao Han
.
DOI:10.
7506/spkx1002-6630-20210927-328
。 Click to view information about
the article.

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