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The use of dietary fiber to replace fat to develop healthy low-fat sausages is a research hotspot
in the processed meat industry.
From a nutritional point of view, dietary fiber is known as the "seventh major nutrient", which can improve the intestinal probiotic population and reduce the incidence
of cardiovascular disease.
The World Health Organization recommends that the daily intake of dietary fiber should reach 25 g
.
However, the results showed that different types of dietary fiber as fat substitutes had significant differences on the sensory texture of low-fat
sausages.
Konjac gum is extracted from the roots of konjac herbs, and its main component is konjac glucomannan
.
Konjac glucomannan is a non-ionic, water-soluble polymer polysaccharide made by polymerizing D-glucose and D-mannose
.
As a dietary fiber, konjac gum has zero calories, chelated cholesterol and promotes intestinal peristalsis
.
Therefore, Yuan Huagen of Jiangsu Vocational College of Agriculture and Animal Husbandry Science and Technology, Chen Yinji* of the School of Food Science and Engineering of Nanjing University of Finance and Economics, and the Collaborative Innovation Center of Modern Grain Circulation and Safety of Jiangsu Province used myofibrillar protein-konjac gum (MP-KG) as the simulation system to elucidate the regulatory mechanism of microstructure on protein gel texture through microstructure (paraffin section and scanning electron microscopy), image analysis software technology (fractional dimensional analysis and absence analysis) and texture characteristics.
It provides a certain theoretical basis
for the application of KG in low-fat meat products.
1.
Deformation characteristics of MP-KG gel
As shown in Figure 1, the amount of KG added had a significant
effect on the stress-strain during fracture and deformation of the composite gel.
With the increase of KG addition, the stress change during fracture deformation of the composite gel showed a parabolic shape, which indicated that the stress improvement of KG on the composite gel had the addition limit
.
The trend of strain and stress during fracture deformation of composite gels are similar, but the addition limits of the two are different
.
Figure 1 shows that the maximum stress is 13.
73 kPa when the fracture deformation is added to the 1% KG group and the maximum strain is 1.
02
when the fracture deformation of the KG group is added 0.
5%.
When the KG addition amount reached 2%, the stress strain during fracture deformation of the composite gel was the lowest, which was 16.
31 kPa and 0.
68
, respectively.
This shows that when KG exceeds the addition limit, the texture characteristics of the composite gel will be significantly reduced, even lower than that of the control group
.
2.
Low-field NMR
of water molecules in the three distribution states in the composite gel were supplemented with different proportions of KG.
The results showed that with the increase of KG addition, the relaxation time of water that was not easy to flow showed a hook-like trend, and the relaxation time of water that was not easy to flow was the lowest and its relative percentage was the highest when 1.
0% was added, which was 274 ms and 92.
79%,
respectively.
This shows that KG can effectively promote the formation of dense protein gel network structure and improve the binding
of water molecules.
When the addition amount was increased to 2%, the relaxation time and relative percentage of the treatment group were the highest, 343.
51 ms and 77.
51%,
respectively.
This shows that when KG exceeds the addition limit, it will inhibit the aggregation
of MP gel network structure.
In addition, the change of KG addition amount had no significant effect on the bound water, indicating that the change of the bound water was only related
to the MP ratio.
The amount of KG added significantly affected the percentage of free water, and the percentage of free water was lowest when 1.
0% KG was added, which indicated that the gel network structure could bind enough water that was not easy to flow, thereby reducing the proportion of
free water.
3.
Limiting behavior
The control group showed the MP gel microstructure, which is a porous irregular three-dimensional network structure
.
When KG was not added, the three-dimensional structure of the MP network in the control group was uniform, and white water holes
of different shapes and sizes were evenly distributed in the gap of the three-dimensional network structure.
When a small amount of KG is added, the KG is encapsulated in the MP gel network system in the form of a dispersed phase
.
The shape size of KG was significantly larger than that of water holes in the control group, so the microstructure of the composite gel was no longer uniform
.
When the KG addition amount exceeds 1%, KG is no longer embedded in the
MP network structure.
KG itself can be hydrated by hydrogen bonding to form a weak gel structure, and then interpenetrate and cross with the MP gel structure to form a bicontinuous phase
.
This experiment showed that the phase limit behavior of KG in MP gel network system changed with the amount added: when the KG addition amount was less than 1%, carbohydrates were wrapped in MP gel network system in the form of dispersed phase.
When the KG addition amount is higher than 1%, both carbohydrate and MP form a continuous phase, and the two penetrate and cross
each other.
4.
Scanning electron microscopy results
.
The observation results showed that the addition of different proportions of KG had a significant
effect on the structure of MP three-dimensional gel network.
The observation control group found that the MP gel network structure was coarse filamentous and even some areas showed a clump-like structure, indicating that the MP folding structure was not fully expanded during the heating process, and a large number of hydrophobic groups were still embedded in the molecule, and then there were no large number of hydrophobic groups crosslinking with each other to form a dense three-dimensional network structure
during the subsequent heating process.
In addition, there are a large number of black holes in the gap of the MP three-dimensional network structure, and these black holes are cross-linked with each other to form water gullies, which divide the MP three-dimensional network gel structure into sheets
.
In this experiment, image processing software was used to perform dimensional analysis of MP network structure (white part) and gap analysis (black part) (Figure 4).
The numerical size of the split-dimensional analysis structure is proportional to the density of the MP network structure.
The missing analysis is proportional
to the difference in the size and shape of the ravine.
THE ANALYSIS RESULTS SHOWED THAT THE DIMENSIONAL DIMENSION OF MP-GEL NETWORK STRUCTURE IN THE TREATMENT GROUP (1% KG) WAS SIGNIFICANTLY HIGHER THAN THAT OF OTHER KG GROUPS (P<0.
05), WHILE THE MISSING VALUE OF 0.
279 WAS SIGNIFICANTLY LOWER THAN THAT OF OTHER ADDED KG GROUPS (P<0.
05).
<b16> The dimensional dimension of MP gel network structure in the treatment group (2% KG added) was significantly lower than that of other KG groups (P<0.
05), while the missing value of 0.
345 was significantly higher than that of other KG addition groups (P<0.
05).
<b17>
5.
Regulation of sensory texture characteristics by the microstructure of MP-KG gel system
gels.
When the phase behavior of MP-KG is interpenetrating structure, the hydrogel formed by hydrogen bonding and hydration of KG is a weak gel, and its gel strength is significantly smaller than that of MP gel.
The hydrogel formed by KG will seriously hinder the exposure of MP hydrophobic groups and the subsequent crosslinking during heating, which in turn leads to the deterioration of the composite gel texture (that is, the stress and strain during fracture deformation are significantly reduced).
Conclusion
KG significantly affected the texture quality of MP gel, and the stress-strain during fracture deformation of composite gel increased significantly when the addition amount was less than 0.5%.
When the addition amount is greater than 1%, the stress strain during the fracture deformation of the composite gel is significantly reduced
.
Paraffin sections and scanning electron microscopy showed that when the amount of KG was less than 1%, the KG was uniformly dispersed in the protein matrix and showed a filling structure, and its stable aqueous phase reduced the formation of water grooves inside the protein network structure during the heat-induced gel, indirectly promoted the cross-linking between MPs, formed a dense and uniform network structure and improved the texture characteristics of the composite gel.
When the amount of KG added is greater than 1%, the continuous weak gel formed by KG through hydration forms a cross-penetrating structure with MP, which in turn seriously hinders the crosslinking of MP in the subsequent heating process, and then makes the composite gel texture deteriorate
.
This paper "Studying the Regulatory Mechanism of Microstructure Affecting Texture Properties Based on MP-KG Gel System" is from Food Science, Vol.
43, No.
16, 2022, pp.
129-134, authors: Yuan Huagen, Shi Shuai, Xi Zhaoshou, Pan Xuefeng, Chen Xia, Chen Yinji
.
DOI:10.
7506/spkx1002-6630-20210528-342
。 Click to view information about
the article.
