Emulsified sausages are popular among people due to their good taste, delicious flavor and rich varieties. The processing technology of emulsified sausages is not complicated, but problems such as oil leakage and loose structure often occur during processing due to poor control of production conditions, improper operation, especially poor emulsification of meat paste or poor stability of emulsified meat paste.
1. Basic Principles
Emulsified meat paste is composed of a matrix of muscle and connective tissue fibers (or fiber fragments) suspended in a water medium containing soluble proteins and other soluble muscle components. The dispersed phase is solid or liquid fat globules, and the continuous phase is a water solution containing dissolved (or suspended) salts and proteins.
In this system, the emulsifier is the salt-soluble protein in the continuous phase. The entire emulsion is of the water-in-oil type. Since the diameter of the dispersed fat globules is generally greater than 50 μm, emulsified meat paste is not a true emulsion. Myofibrils containing more myosin, myosin will coagulate when heated to 58-68°C. Connective tissue rich in collagen will shrink to one-third of its original size when heated to 68°C. If heated further, it will form gelatin. During chopping, collagen absorbs a large amount of water, but during subsequent heating, it shrinks and expels the water.
Myofibrillar proteins have better emulsifying properties and are insoluble in water and dilute salt solutions but soluble in concentrated salt solutions. Therefore, in the processing of emulsified sausages, salt must be added during chopping to help these proteins dissolve and act as emulsifiers to completely wrap the dispersed fat particles, thereby maintaining the stability of the emulsified meat paste.
2. Influencing Factors
There are many factors that affect the formation and stability of emulsified meat paste, including the temperature during emulsification, the size of fat particles, pH, the quantity and type of soluble proteins, and the viscosity of the emulsion.
(1) Temperature during emulsification During the chopping or emulsification of raw meat, a large amount of heat is generated due to friction in the chopper and emulsifier. Appropriate temperature increase can help the solubilization of salt-soluble proteins, accelerate the formation of cured color, and increase the fluidity of the meat paste. However, if the temperature during emulsification is too high, it will cause the denaturation of salt-soluble proteins and loss of emulsifying function; it will also reduce the viscosity of the emulsion, causing the smaller fat particles in the dispersed phase to move to the surface of the emulsified meat paste, reducing the stability of the emulsion; and it will cause the fat particles to melt and become smaller micro-particles during chopping and emulsification, with a sharp increase in surface area, making it impossible for the soluble proteins to completely wrap them, that is, the fat cannot be completely emulsified. As a result, the emulsion structure collapses during subsequent thermal processing, causing oil leakage in the sausage.
The best release of salt-soluble proteins from lean meat occurs at low temperatures, while the best fat binding occurs at slightly higher temperatures. Based on practical experience, a compromise solution is to keep the final temperature of chopping between 12-15°C. Starch will accelerate the temperature rise of the meat paste in the chopper, so in most cases, starch must be added as the last ingredient to avoid exceeding the appropriate final temperature.
It is equally important that all ingredients reach a certain degree of chopping. If the muscle and fat tissues are chopped too finely, resulting in relatively too few structural proteins, it is called "over-chopping". If the initial chopping time of lean meat or the total chopping time is too short, too few salt-soluble proteins are released from the muscle cells or the fat is not evenly distributed, it will cause the "under-chopping" phenomenon.
(2) Water and Fat The base material for the swelling and dissolution of proteins in emulsified sausage (ham) meat paste is water. To produce successful sausage meat paste, there must be sufficient water. Water should be added in batches because the process of protein binding water molecules (swelling) is gradual and continuous. It is usually recommended to add in three batches. 40% should be added during the chopping process when the meat is mixed with salt, phosphate, and other curing agents. 30% should be added during the chopping of fat. The remaining 30% should be added at the end along with starch and other ingredients.
Fat, which accounts for about 30% of the meat mixture, plays a crucial role in stabilizing the meat mixture system. Fat is distributed within the protein network, which can alleviate the shrinkage of the protein structure caused by heat denaturation. As fat is distributed along with proteins in the product structure, it can prevent product aging and improve the tenderness and thermal stability of the product.
However, when the fat content is too high, the required protein network becomes stronger, which is often difficult to achieve. Therefore, the proportion of fat in the meat mixture should be scientifically configured. During the emulsification process, to form a good emulsified meat paste, the fat in the raw meat must be chopped into appropriately sized particles. As the volume of fat particles decreases, their surface area increases, and more salt-soluble proteins are required for emulsification.
(3) The quantity and type of salt-soluble proteins: When making emulsified meat pastes, since salt can help extract salt-soluble proteins from lean meat, lean meat should be chopped first under salt conditions, and then raw meat with a high fat content should be added for chopping. The more salt-soluble proteins extracted, the better the stability of the emulsified meat paste. Moreover, the more myosin there is, the greater the emulsification capacity. The amount of extracted protein is directly related to the pH of the raw meat. When the pH is high, more proteins are extracted, and the stability of the emulsion is better.
(4) The state of raw meat: The amount of salt-soluble proteins (mainly myofibrillar proteins) that can be extracted from fresh meat before rigor mortis is 50% more than that from meat after rigor mortis. The emulsification effect of salt-soluble myofibrillar proteins is much better than that of sarcoplasmic proteins. Under the same weight of raw meat, fresh meat can emulsify more fat. However, it is difficult for factories to completely use fresh meat for production. If factories can only use meat after rigor mortis for production, the raw meat should be chopped with ice, salt, and curing agents before emulsification, and then placed at 0-4°C for 12 hours. This can extract more proteins.
(5) Salt concentration: The total concentration of salt (table salt, nitrite, and phosphate in curing agents) in the meat mixture is very important for the swelling and dissolution of actomyosin and myosin. Actomyosin is insoluble in water but soluble in salt solutions, and its solubility increases with the increase of salt concentration, reaching a maximum when the salt concentration is 5% to 6% (based on the lean meat weight). Therefore, from a process perspective, salt in emulsified sausages (ham) should be added during pre-curing or the initial stage of chopping lean meat.
(6) pH value: The pH value of meat at the time of slaughter is about 7.2, and it drops below 5.8 within a few hours, significantly affecting the water-holding capacity of actomyosin. As the pH value decreases, the protein structure becomes increasingly water-repellent. The water-holding capacity of meat is the lowest at pH 5.0-5.2 (the isoelectric point of actomyosin). Technically speaking, meat with a pH value above 5.7 should be used to make emulsified sausages (ham). Adding table salt and phosphate or curing agents containing phosphate can slightly increase the pH value, thereby improving the water-holding capacity.
(7) Chopping of raw meat: Actomyosin and myosin are filamentous structures contained within muscle cells. Muscle cells are wrapped in a layer of connective tissue membrane. As long as this membrane remains intact, actomyosin and myosin can only bind to the water within the cells themselves and cannot bind to added water. Therefore, during the chopping process, the cell membrane must be broken to allow the fragments of structural proteins to be released and absorb added water, and through water absorption and swelling, form a protein gel membrane, thereby absorbing and encapsulating fat and preventing fat particles from aggregating and melting out during heating. Under the optimal concentrations of salt and phosphate, the more the cell membranes of muscle cells open, the more salt-soluble proteins are released from actomyosin. Sharp knives and "dry chopping" of lean meat are very effective. "Dry chopping" means that at the beginning of the chopping process, lean meat is strongly chopped together with salt, phosphate and other curing agents. All muscle cells are chopped open, and the released structural proteins are further chopped. Under high salt concentration, the salt-soluble proteins are released to the maximum extent. Fat cells contain fat wrapped in a connective tissue network, the cell membrane. Intact fat cells are stable to heat. During the chopping process, the cell membranes are broken, and the fat is released, forming very small fat particles or spheres. The finer the fat tissue is chopped, the more fat is released, and it is easy to aggregate during heating, causing the product to become oily. To prevent the aggregation of fats, more proteins are needed. When there is less lean meat and more fat in the sausage formula, the protein network is unable to absorb all the free fat. Therefore, the fat tissue should be chopped until it is evenly mixed with the meat paste, and should not be over-chopped.
3. Common Problems and Solutions
(1) Excessive temperature during chopping To prevent protein denaturation due to excessive temperature during emulsification, the generated heat must be absorbed.
One method is to add ice during chopping. The effect of adding ice is far better than adding ice water because ice absorbs a large amount of heat when melting into ice water. In addition to absorbing heat, adding ice can also improve the fluidity of the emulsion, which is beneficial for subsequent filling. Another method to lower the temperature is to add solid carbon dioxide (dry ice) during the chopping of raw meat or to add some frozen meat during chopping. In summary, it is necessary to ensure that the temperature of the meat paste does not exceed 12°C at the end of chopping.
(2) Excessive chopping The collapse of the emulsification structure is mainly caused by the re-aggregation of dispersed fat particles into large fat spheres. If all fat spheres are completely wrapped by salt-soluble proteins, the aggregation phenomenon is difficult to occur. However, when chopping is excessive, the released proteins cannot completely wrap all fat spheres. These unwrapped or poorly wrapped fat spheres will melt during heating, and the melted fat is more likely to aggregate, resulting in an oily sausage and even a fat layer at the top of the sausage. If this occurs, the chopping process and parameters need to be adjusted.
(3) Insufficient salt-soluble protein extraction due to low lean meat content Low lean meat content mainly refers to an imbalance in the composition of myosin and collagen in the raw meat or too low lean meat content in the raw material. The fat spheres wrapped by myosin and collagen are of the same size. However, during heating, collagen shrinks and further heating generates gelatin droplets that flow away from the surface of the fat spheres, exposing them. As a result, a fat layer forms at the top of the final sausage, while a gelatin block forms at the bottom. If this occurs during production, it is necessary to adjust the composition of the raw meat, increase the lean meat content, and add some complex phosphates during chopping to increase the pH of the meat and help extract salt-soluble proteins. Additionally, some food-grade non-meat proteins, such as tissue protein, serum protein, and soy protein isolate, can be added to improve the emulsification effect of the meat.
(4) Rapid heating or excessive cooking temperature Even if the composition of the raw meat is reasonable and the previous processing is proper, if the heating is too rapid or the temperature is too high, fat separation can still occur. During rapid heating, the proteins on the surface of the fat spheres coagulate and wrap the fat spheres. Continued heating causes the fat spheres to expand, while the protein film on their surface tends to contract. If this process continues, the coagulated protein film will be broken, and the internal fat will flow out. When this situation occurs in the production of Frankfurt sausages, it will make the surface of the sausages slightly greasy and cause oil stains on the smoking rods. Although this problem is not as serious as over-mixing or insufficient lean meat, the parameters of smoking and cooking should also be adjusted appropriately.
(5) The emulsion is left for too long. The emulsified meat paste should be filled as soon as possible because the stability time of the emulsion is only a few hours. If it is left for too long, the structure of the emulsified meat paste will collapse, and oil will come out during the subsequent heating process.
1. Basic Principles
Emulsified meat paste is composed of a matrix of muscle and connective tissue fibers (or fiber fragments) suspended in a water medium containing soluble proteins and other soluble muscle components. The dispersed phase is solid or liquid fat globules, and the continuous phase is a water solution containing dissolved (or suspended) salts and proteins.
In this system, the emulsifier is the salt-soluble protein in the continuous phase. The entire emulsion is of the water-in-oil type. Since the diameter of the dispersed fat globules is generally greater than 50 μm, emulsified meat paste is not a true emulsion. Myofibrils containing more myosin, myosin will coagulate when heated to 58-68°C. Connective tissue rich in collagen will shrink to one-third of its original size when heated to 68°C. If heated further, it will form gelatin. During chopping, collagen absorbs a large amount of water, but during subsequent heating, it shrinks and expels the water.
Myofibrillar proteins have better emulsifying properties and are insoluble in water and dilute salt solutions but soluble in concentrated salt solutions. Therefore, in the processing of emulsified sausages, salt must be added during chopping to help these proteins dissolve and act as emulsifiers to completely wrap the dispersed fat particles, thereby maintaining the stability of the emulsified meat paste.
2. Influencing Factors
There are many factors that affect the formation and stability of emulsified meat paste, including the temperature during emulsification, the size of fat particles, pH, the quantity and type of soluble proteins, and the viscosity of the emulsion.
(1) Temperature during emulsification During the chopping or emulsification of raw meat, a large amount of heat is generated due to friction in the chopper and emulsifier. Appropriate temperature increase can help the solubilization of salt-soluble proteins, accelerate the formation of cured color, and increase the fluidity of the meat paste. However, if the temperature during emulsification is too high, it will cause the denaturation of salt-soluble proteins and loss of emulsifying function; it will also reduce the viscosity of the emulsion, causing the smaller fat particles in the dispersed phase to move to the surface of the emulsified meat paste, reducing the stability of the emulsion; and it will cause the fat particles to melt and become smaller micro-particles during chopping and emulsification, with a sharp increase in surface area, making it impossible for the soluble proteins to completely wrap them, that is, the fat cannot be completely emulsified. As a result, the emulsion structure collapses during subsequent thermal processing, causing oil leakage in the sausage.
The best release of salt-soluble proteins from lean meat occurs at low temperatures, while the best fat binding occurs at slightly higher temperatures. Based on practical experience, a compromise solution is to keep the final temperature of chopping between 12-15°C. Starch will accelerate the temperature rise of the meat paste in the chopper, so in most cases, starch must be added as the last ingredient to avoid exceeding the appropriate final temperature.
It is equally important that all ingredients reach a certain degree of chopping. If the muscle and fat tissues are chopped too finely, resulting in relatively too few structural proteins, it is called "over-chopping". If the initial chopping time of lean meat or the total chopping time is too short, too few salt-soluble proteins are released from the muscle cells or the fat is not evenly distributed, it will cause the "under-chopping" phenomenon.
(2) Water and Fat The base material for the swelling and dissolution of proteins in emulsified sausage (ham) meat paste is water. To produce successful sausage meat paste, there must be sufficient water. Water should be added in batches because the process of protein binding water molecules (swelling) is gradual and continuous. It is usually recommended to add in three batches. 40% should be added during the chopping process when the meat is mixed with salt, phosphate, and other curing agents. 30% should be added during the chopping of fat. The remaining 30% should be added at the end along with starch and other ingredients.
Fat, which accounts for about 30% of the meat mixture, plays a crucial role in stabilizing the meat mixture system. Fat is distributed within the protein network, which can alleviate the shrinkage of the protein structure caused by heat denaturation. As fat is distributed along with proteins in the product structure, it can prevent product aging and improve the tenderness and thermal stability of the product.
However, when the fat content is too high, the required protein network becomes stronger, which is often difficult to achieve. Therefore, the proportion of fat in the meat mixture should be scientifically configured. During the emulsification process, to form a good emulsified meat paste, the fat in the raw meat must be chopped into appropriately sized particles. As the volume of fat particles decreases, their surface area increases, and more salt-soluble proteins are required for emulsification.
(3) The quantity and type of salt-soluble proteins: When making emulsified meat pastes, since salt can help extract salt-soluble proteins from lean meat, lean meat should be chopped first under salt conditions, and then raw meat with a high fat content should be added for chopping. The more salt-soluble proteins extracted, the better the stability of the emulsified meat paste. Moreover, the more myosin there is, the greater the emulsification capacity. The amount of extracted protein is directly related to the pH of the raw meat. When the pH is high, more proteins are extracted, and the stability of the emulsion is better.
(4) The state of raw meat: The amount of salt-soluble proteins (mainly myofibrillar proteins) that can be extracted from fresh meat before rigor mortis is 50% more than that from meat after rigor mortis. The emulsification effect of salt-soluble myofibrillar proteins is much better than that of sarcoplasmic proteins. Under the same weight of raw meat, fresh meat can emulsify more fat. However, it is difficult for factories to completely use fresh meat for production. If factories can only use meat after rigor mortis for production, the raw meat should be chopped with ice, salt, and curing agents before emulsification, and then placed at 0-4°C for 12 hours. This can extract more proteins.
(5) Salt concentration: The total concentration of salt (table salt, nitrite, and phosphate in curing agents) in the meat mixture is very important for the swelling and dissolution of actomyosin and myosin. Actomyosin is insoluble in water but soluble in salt solutions, and its solubility increases with the increase of salt concentration, reaching a maximum when the salt concentration is 5% to 6% (based on the lean meat weight). Therefore, from a process perspective, salt in emulsified sausages (ham) should be added during pre-curing or the initial stage of chopping lean meat.
(6) pH value: The pH value of meat at the time of slaughter is about 7.2, and it drops below 5.8 within a few hours, significantly affecting the water-holding capacity of actomyosin. As the pH value decreases, the protein structure becomes increasingly water-repellent. The water-holding capacity of meat is the lowest at pH 5.0-5.2 (the isoelectric point of actomyosin). Technically speaking, meat with a pH value above 5.7 should be used to make emulsified sausages (ham). Adding table salt and phosphate or curing agents containing phosphate can slightly increase the pH value, thereby improving the water-holding capacity.
(7) Chopping of raw meat: Actomyosin and myosin are filamentous structures contained within muscle cells. Muscle cells are wrapped in a layer of connective tissue membrane. As long as this membrane remains intact, actomyosin and myosin can only bind to the water within the cells themselves and cannot bind to added water. Therefore, during the chopping process, the cell membrane must be broken to allow the fragments of structural proteins to be released and absorb added water, and through water absorption and swelling, form a protein gel membrane, thereby absorbing and encapsulating fat and preventing fat particles from aggregating and melting out during heating. Under the optimal concentrations of salt and phosphate, the more the cell membranes of muscle cells open, the more salt-soluble proteins are released from actomyosin. Sharp knives and "dry chopping" of lean meat are very effective. "Dry chopping" means that at the beginning of the chopping process, lean meat is strongly chopped together with salt, phosphate and other curing agents. All muscle cells are chopped open, and the released structural proteins are further chopped. Under high salt concentration, the salt-soluble proteins are released to the maximum extent. Fat cells contain fat wrapped in a connective tissue network, the cell membrane. Intact fat cells are stable to heat. During the chopping process, the cell membranes are broken, and the fat is released, forming very small fat particles or spheres. The finer the fat tissue is chopped, the more fat is released, and it is easy to aggregate during heating, causing the product to become oily. To prevent the aggregation of fats, more proteins are needed. When there is less lean meat and more fat in the sausage formula, the protein network is unable to absorb all the free fat. Therefore, the fat tissue should be chopped until it is evenly mixed with the meat paste, and should not be over-chopped.
3. Common Problems and Solutions
(1) Excessive temperature during chopping To prevent protein denaturation due to excessive temperature during emulsification, the generated heat must be absorbed.
One method is to add ice during chopping. The effect of adding ice is far better than adding ice water because ice absorbs a large amount of heat when melting into ice water. In addition to absorbing heat, adding ice can also improve the fluidity of the emulsion, which is beneficial for subsequent filling. Another method to lower the temperature is to add solid carbon dioxide (dry ice) during the chopping of raw meat or to add some frozen meat during chopping. In summary, it is necessary to ensure that the temperature of the meat paste does not exceed 12°C at the end of chopping.
(2) Excessive chopping The collapse of the emulsification structure is mainly caused by the re-aggregation of dispersed fat particles into large fat spheres. If all fat spheres are completely wrapped by salt-soluble proteins, the aggregation phenomenon is difficult to occur. However, when chopping is excessive, the released proteins cannot completely wrap all fat spheres. These unwrapped or poorly wrapped fat spheres will melt during heating, and the melted fat is more likely to aggregate, resulting in an oily sausage and even a fat layer at the top of the sausage. If this occurs, the chopping process and parameters need to be adjusted.
(3) Insufficient salt-soluble protein extraction due to low lean meat content Low lean meat content mainly refers to an imbalance in the composition of myosin and collagen in the raw meat or too low lean meat content in the raw material. The fat spheres wrapped by myosin and collagen are of the same size. However, during heating, collagen shrinks and further heating generates gelatin droplets that flow away from the surface of the fat spheres, exposing them. As a result, a fat layer forms at the top of the final sausage, while a gelatin block forms at the bottom. If this occurs during production, it is necessary to adjust the composition of the raw meat, increase the lean meat content, and add some complex phosphates during chopping to increase the pH of the meat and help extract salt-soluble proteins. Additionally, some food-grade non-meat proteins, such as tissue protein, serum protein, and soy protein isolate, can be added to improve the emulsification effect of the meat.
(4) Rapid heating or excessive cooking temperature Even if the composition of the raw meat is reasonable and the previous processing is proper, if the heating is too rapid or the temperature is too high, fat separation can still occur. During rapid heating, the proteins on the surface of the fat spheres coagulate and wrap the fat spheres. Continued heating causes the fat spheres to expand, while the protein film on their surface tends to contract. If this process continues, the coagulated protein film will be broken, and the internal fat will flow out. When this situation occurs in the production of Frankfurt sausages, it will make the surface of the sausages slightly greasy and cause oil stains on the smoking rods. Although this problem is not as serious as over-mixing or insufficient lean meat, the parameters of smoking and cooking should also be adjusted appropriately.
(5) The emulsion is left for too long. The emulsified meat paste should be filled as soon as possible because the stability time of the emulsion is only a few hours. If it is left for too long, the structure of the emulsified meat paste will collapse, and oil will come out during the subsequent heating process.
