Emulsified sausage is deeply loved by people because of its good taste, delicious taste and rich variety. Its processing technology is not complicated, but in the processing process, the products often produce oil and loose structure due to lax control of production conditions and improper operation, especially poor emulsification or poor stability of emulsified meat emulsion.
01.Basic principle of emulsion of minced meat
Emulsified minced meat consists of the matrix of muscle and connective tissue fibers (or fiber fragments) suspended in an aqueous medium containing soluble protein and other soluble muscle components. The dispersed phase is solid or liquid fat globules, and the continuous phase is an aqueous solution in which salt and protein are dissolved (or suspended).
In this system, it is the salt-soluble protein in the continuous phase that acts as the emulsifier, and the whole emulsion belongs to the oil-in-water type. Because the diameter of fat globules in the dispersed phase is generally greater than 50μm, emulsified meat emulsion is not a real emulsion. Myofibrils containing more myosin will coagulate when heated to 58~68℃, and connective tissue rich in collagen will shrink to 1/3 when heated to 68℃, and gelatin will be formed if heated further. Collagen will absorb a lot of water when it is chopped, but it will shrink in the subsequent heating process and squeeze out the water.
Myofibrillar protein has better emulsification, which is insoluble in water and dilute salt solution, but soluble in concentrated salt solution. Therefore, in the processing of emulsified sausage, salt must be added to help these protein dissolve out, so that it can be used as an emulsifier to completely wrap the dispersed fat particles, thus maintaining the stability of emulsion.
02.Factors affecting emulsion of minced meat
There are many factors that affect the formation and stability of emulsion, including the temperature during emulsification, the size of fat particles, pH, the number and type of soluble protein, and the viscosity of emulsion.
(1). Temperature during emulsification
In the process of chopping or emulsifying raw meat, a lot of heat is generated due to the friction between the chopping machine and the emulsifying machine. Proper heating can help the dissolution of salt-soluble protein, accelerate the formation of curing color and increase the fluidity of minced meat. However, if the temperature during emulsification is too high, it will lead to denaturation of salt-soluble proteins and lose emulsification; Secondly, it will reduce the viscosity of emulsion, make the fat particles with smaller specific gravity in the dispersed phase move to the surface of emulsion, and reduce the stability of emulsion; Thirdly, the fat particles will melt and become smaller particles more easily when chopped, mixed and emulsified, and the surface area will increase sharply, so that the soluble protein can't completely wrap them, that is, the fat can't be completely emulsified, so that the emulsified structure of sausage will collapse during the subsequent thermal processing, resulting in oil production.
It is best to chop lean meat to release salt-soluble protein at low temperature, and the best fat binding needs to be carried out at a slightly higher temperature. According to practical experience, the compromise is that the final temperature of chopping is between 12-15℃. Starch will accelerate the temperature rise of meat stuffing in the chopping and mixing machine, so in most cases, starch must be added as the last raw material to avoid exceeding the appropriate final temperature.
It is also important that all raw materials should reach a certain degree of chopping. If muscle tissue and adipose tissue are chopped too much, resulting in relatively little structural protein, it is called "excessive chopping". If the initial chopping time or total chopping time of lean meat is too short, too little salt-soluble protein is released from muscle cells or fat is not evenly distributed, it will cause the phenomenon of "insufficient chopping".
(2). Water and fat
The basic material of protein expansion and dissolution in emulsified sausage (ham) meat stuffing is water, so it is necessary to have enough water to produce successful sausage meat stuffing. Water should be added in batches, because the process of protein combining with water molecules (expansion) is a gradual and continuous process. It is usually recommended to add it in three batches, 40% when the muscle is chopped with salt, phosphate and other pickling agents, 30% when the fat is chopped, and 30% is finally added with starch.
Fat accounting for about 30% of meat stuffing plays an important role in stabilizing the meat stuffing system. Fat distributed in protein omentum can alleviate the shrinkage of protein structure caused by heating denaturation, and fat distributed in product structure with protein can prevent the product from aging, improve the freshness and thermal stability of the product.
However, when the fat content is too high, the required protein omentum is stronger, which is often impossible, so the proportion of fat in the product meat stuffing should be scientifically allocated. In the process of emulsification, in order to form a good emulsified meat emulsion, the fat in the raw meat must be chopped into particles of appropriate size. When the volume of fat particles becomes smaller, its surface area will increase, which requires more salt-soluble protein for emulsification.
(3). Quantity and types of salt-soluble protein.
When making minced meat emulsion, because salt can help to extract salt-soluble protein from lean meat, lean meat should be chopped first under the condition of salt, and then raw meat with high fat content should be added to chop. The more salt-soluble protein extracted, the better the stability of minced meat emulsion, and the more myosin, the greater the emulsifying ability. The amount of protein extracted is directly related to the pH of raw meat. When the pH is high, more protein is extracted, and the emulsion has good stability.
(4). the state of raw meat
The amount of salt-soluble protein (mainly myofibrillar protein) in hot fresh meat before rigor mortis is 50% more than that after rigor mortis, and the emulsifying effect of salt-soluble myofibrillar protein is far better than that of sarcoplasmic protein. Under the condition of the same weight of raw meat, hot fresh meat can emulsify more fat, but it is difficult for the factory to use hot fresh meat completely for production. If the factory can only use the meat after rigor mortis for production, it should add ice, salt and salt to the raw meat before emulsification.
(5). Salt concentration
The total concentration of salt (salt, nitrite and phosphate in curing agent) in meat stuffing is very important for the expansion and dissolution of actin and myosin. Actinin is insoluble in water, but only soluble in salt solution, and its solubility increases with the increase of salt concentration until the salt concentration reaches 5%~6% (based on lean meat). Therefore, from the technological point of view, the salt in emulsified sausage (ham) should be added to lean meat during pre-curing or the initial stage of chopping.
(6). pH value
When animals are slaughtered, the pH value of meat is about 7.2, and it drops below 5.8 after a few hours, which significantly affects the water holding capacity of actin. With the decrease of pH value, protein structure repels water more and more. The water-holding capacity of meat is the lowest at pH5.0-5.2 (isoelectric point of actin). From the point of view of technical safety, meat with pH above 5.7 should be used to make emulsified sausage (ham). Adding salt and phosphate or pickling agent containing phosphate can slightly increase the pH value, thus improving the water-holding capacity.
(7). raw meat chop.
Actin and myosin are filaments contained in muscle cells. Muscle cells are wrapped in a connective tissue membrane. As long as this membrane remains intact, actin and myosin can only combine with the water of the cell itself, but not with additional water. Therefore, in the chopping process, the cell membrane must be opened, so that the fragments of structural protein can be freed to absorb additional water and form a protein gel membrane through water absorption and expansion, thus absorbing the encapsulated fat, and preventing the fat particles from gathering and melting when heated.
Under the optimum concentration of salt and phosphate, the more cell membranes of muscle cells are opened, the more salt-soluble proteins are released from actin. Sharp kopis and "dry chopping" of lean meat are very effective. "Dry chopping" is to chop and mix lean meat with salt, phosphate and other curing agents at the beginning of chopping and mixing. Chop all muscle cells, chop the free structural proteins, and release salt-soluble proteins to the maximum at high salt concentration.
The fat in fat cells is wrapped in a layer of connective tissue network, that is, cell membrane, and the intact fat cells are stable to heat. In the process of chopping and mixing, the cell membrane is broken, and the fat is released, forming small fat particles or balls. The finer the fat tissue is chopped, the more fat is released, which is easy to aggregate when heated, leading to oil production. To prevent the fat from gathering, more protein is needed. In the sausage formula, there is less lean meat and more fat, and the protein omentum is unable to absorb all the free fat. Therefore, the adipose tissue should be cut evenly with the meat stuffing, and it should not be cut excessively.
03.Common problems and solutions in processing
(1). The temperature is too high during chopping.
In order to prevent protein denaturation caused by high temperature during emulsification, it is necessary to absorb the generated heat.
One method is to add ice in the chopping process, and the effect of adding ice is far better than that of adding ice water, because ice absorbs a lot of heat when it melts into ice water. Adding ice can not only absorb heat, but also make the fluidity of emulsion better, which is beneficial to subsequent filling. Another way to reduce the temperature is to add solid carbon dioxide (dry ice) or a part of frozen meat when chopping raw meat. In short, it is necessary to ensure that the temperature of minced meat is not higher than 12℃ at the end of chopping.
(2). Excessive chopping and mixing
The collapse of emulsion structure is mainly caused by the polymerization of dispersed fat particles into large fat balls. If all the fat globules are completely wrapped by salt-soluble protein, polymerization will be difficult to occur. However, when chopping excessively, the dissolved protein can't completely wrap all the fat globules. These fat globules that are not wrapped or loosely wrapped will melt during the heating process, and the melted fat will polymerize more easily, resulting in greasy sausage and even a fat lump at the top of the sausage. If this happens, the chopping process and parameters should be adjusted.
(3). Less lean meat and insufficient extraction of salt-soluble protein.
Less lean meat mainly means that the composition of myosin and collagen in raw meat is unbalanced, or the content of lean meat in raw meat is too low. The size of fat balls wrapped by myosin and collagen is the same. However, during the heating process, collagen will shrink, and further heating will generate gelatin droplets, which will flow away from the surface of the fat balls to expose the fat balls, so that the top of the final finished sausage will form a fat bag and the bottom will form a jelly block. If this happens in production, it is necessary to adjust the composition of raw meat to increase the lean meat content. Some compound phosphates should be properly added during chopping to improve the pH of meat and help the extraction of salt-soluble proteins. At the same time, some food-grade non-meat proteins, such as tissue protein, serum protein and soy protein isolate, can be appropriately added to help improve the emulsification effect of meat.
(4). heating too fast or cooking temperature is too high
Even if the composition of raw meat is reasonable and the pre-processing process is handled properly, if the heating is too fast or the temperature is too high, fat separation will occur. In the process of rapid heating, the protein on the surface of the fat ball solidifies and wraps the fat ball, and the fat ball continues to expand when heated, while the protein film wrapped on its surface tends to shrink. If this process continues, the solidified protein film will burst and the internal fat will flow out. When this happens in Frankfurt sausage production, it will make the sausage surface slightly greasy and produce oil spots on the smoking stick. Although this situation is not as serious as the problem caused by excessive chopping or insufficient lean meat, the parameters of smoking and cooking should be adjusted appropriately.
(5). The emulsion is left for too long.
The emulsified meat emulsion should be filled as soon as possible, because the stability time of the emulsion is about several hours. If the time is too long, the emulsified meat emulsion structure will collapse and oil will appear in the subsequent heating process.
