In principle, the transportation, storage and sales of low-temperature meat products are required to be carried out under low temperature (0-4°C) conditions. Common bacon, ham, low-temperature emulsified sausages, hot dog sausage products, etc. are all low-temperature meat products. During the processing of low-temperature meat products, the protein is moderately denatured, the meat is firm, elastic, chewy, tender, crisp, soft, and juicy, and the original nutrition and inherent flavor are retained to the maximum extent. The quality is obviously better than that of high-temperature meat products, and it can be convenient for long-distance transportation and storage by establishing a sound cold chain system and adopting appropriate preservation technology to extend its shelf life. Low-temperature meat products have become the main trend of future development of meat products in my country due to their advanced processing technology, high technological content, less nutritional loss, special product flavor, and bright color. The processing technology of low-temperature meat products mainly includes marinating, rolling, kneading, chopping, baking, steaming, cooling, and packaging. Among them, the chopping process has a great influence on the yield and quality of low-temperature meat products.
01 Mechanism of chopping and mixing
Actin and myosin in meat are filaments embedded in muscle cells. Muscle cells are wrapped by a layer of connective tissue. As long as this membrane remains intact, actin and myosin are still wrapped in the membrane. They can only combine with their own water, but not with fat or external water. Therefore, this membrane must be cut to facilitate the release of structural protein fragments, absorb the added ice water, and expand by absorbing water to form a protein gel network, thereby containing fat and preventing fat particles from gathering during heating. Therefore, the chopping and mixing process is not only a chopping process, but also a good mixing and emulsification process, that is, chopping and mixing can promote the formation of closed network structure inside low-temperature meat products and the precipitation of salt-soluble proteins.
According to experiments, the finer the lean meat is chopped, the easier it is to increase the contact surface between the salt solution and the myofibrillar protein, and the amount of salt-soluble protein extracted will also increase, which is more conducive to the formation of a closed network structure and the better the emulsification and water retention of meat products. As a process of emulsifying meat, chopping is crucial in the processing of low-temperature meat products. The quality of chopping emulsification directly affects the quality of the product. The various process parameters in this process are quite strict. If the chopping is not properly controlled in actual production, it will lead to excessive processing temperature or poor chopping of raw materials, resulting in problems such as oil separation, sticking skin, and bag bulging. Only by fully understanding the chopping mechanism, grasping the key points of chopping, and conscientiously implementing the various process parameters required in the chopping process can the above problems be controlled and stable quality low-temperature meat products can be produced.
02 Temperature of chopping-related links
The ambient temperature, raw material temperature, chopping temperature, sharpness of the chopping knife, and chopping time during chopping can affect the emulsification degree of the meat. In order to facilitate the control of the temperature of the entire chopping process, the temperature of the operating workshop should not be higher than 15℃ or lower. The temperature of raw meat is controlled at 0~4℃. The temperature of auxiliary materials mainly refers to the temperature of starch and other auxiliary materials. Before production, they should be placed in the cooling room for precooling for more than 24 hours to below 15℃. The chopping process requires the use of a vacuum chopper and is carried out under low temperature conditions.
Related studies have shown that the optimal temperature for extracting salt-soluble protein from muscle is 0~4℃, and the optimal fat emulsification needs to be carried out at 8-12℃. Therefore, according to the processing characteristics and the different feeding time, the temperature control is mainly divided into three stages (4℃~8℃-12℃), that is, chopping lean meat at 0~4℃ to extract salt-soluble protein, and chopping at 8~12℃ to emulsify fat better. Therefore, in actual operation, in order to avoid the increase in meat temperature caused by the strong mechanical action during chopping, 7~10% ice chips from meat combs are often added to the meat during chopping, that is, ice is added in the early stage and ice water or ice salt water is added in the later stage to control the temperature. The amount of ice chips added should be included in the total amount of water added, which not only extracts salt-soluble protein well to enhance emulsification, but also makes fat emulsification better.
At the end of chopping, the temperature should be kept below 8~12℃ to ensure the chopping effect. If the chopping temperature is too high, it will affect the elasticity of the meat filling and reduce its oil and water holding properties, which will lead to the product's sensory dispersion, oil loss, and water leakage, ultimately affecting the product yield and shelf life.
03 Chopping sequence
(1) Full-mix chopping method Full-mix chopping means chopping all the raw materials in a chopper at the fastest speed. Add 1/3 to 1/2 of ice water at the beginning of chopping, and slowly add the remaining ice water when the temperature reaches about 10°C. Add starch and other auxiliary materials at the end of the chopping process. Adding certain auxiliary materials during chopping can not only improve the color, aroma and taste of the finished sausage, but also help improve the quality. Phosphates can improve the structure and consistency of the sausage filling and the color and taste of the finished product, so that the product does not leak water during steaming. Adding thickeners such as starch and soy protein can increase the yield and improve the slicing properties of the finished product. Citric acid can be added to some products at the end, but not together with mixed salt, otherwise it will not have the effect of coloring. Some products need to add fat. According to different varieties, the fat should be cut into fat blocks of different sizes and shapes. If the fat is cut into pieces manually, the fat pieces will be neat. If a machine is used, the fat must be cooled to 0°C to prevent the fat from breaking and melting. Generally, the fat content in sausage is more appropriate to be 15%.
(2) Staged chopping and mixing Staged chopping and mixing is the most commonly used method. The marinated lean meat is poured into the chopper and dry-chopping for 30 seconds at a low speed and then at a high speed. Then ice chips are added and chopped for 30 seconds. Then the auxiliary fat is added and chopped for 2 minutes at a low speed and then at a high speed. Finally, soy protein and starch are added and emulsified at a high speed for 2 minutes to chop into meat filling. Among them, the so-called dry chopping and mixing is to chop the marinated raw meat without adding water at the beginning of the chopping and mixing, cut all the muscle membranes, chop the free structural proteins, extract the salt-soluble proteins to the maximum extent, and then emulsify them evenly with water and fat. However, it is worth noting that the dry chopping time should not be too long and should be limited to within 30 seconds. Otherwise, due to the friction between the knife and the meat, the heat generated by the temperature rises and the meat protein denatures, affecting the taste and organizational structure of the product. Because the binding force between lean meat and fat is greater than the binding force between lean meat and fat after adding starch, the fat should be fully emulsified and combined with the meat filling before adding starch. Otherwise, the excessive free fat will penetrate into the meat filling after heating, which will reduce the binding force between the fat, starch and water in the meat filling, resulting in a loose organizational structure of the product and even oil precipitation. The chopped meat filling requires uniform, fine particles, relatively viscous and elastic, not watery, and uniform color.
04 Chopping degree and time
(1) Chopping degree It is very necessary to chop the connective tissue and fat tissue in the raw meat appropriately, so that the fat and salt-soluble protein in the minced meat are fully mixed, which is conducive to the closed network structure formed after heating to embed the free fat droplets and give the product a good chewing feel. If the initial chopping time or the total chopping time of lean meat is too short, too little salt-soluble protein will be released from the muscle cells or the fat will be unevenly distributed, resulting in insufficient chopping. Insufficient chopping will lead to poor product structure, uneven particles, and reduced water retention. However, it is not advisable to chop too finely, because excessive chopping will damage the texture of solid fat, promote fat free overflow, and require more closed mesh structures to embed it. When heated, it is easy to produce jelly and fat deposition, resulting in oily products.
(2) Chopping time The time of the entire chopping process is best controlled within 5-6 minutes, of which high-speed emulsification chopping is 3-4 minutes and low-speed chopping is 1-2 minutes. If the time is too short, the meat filling cannot be homogenized, the water content is low, and the meat filling is relatively rough. If the time is too long, the meat filling is too loose.
For beef, it is reported that the color, hardness, elasticity and cohesiveness of beef mince are best when it is chopped for 20 minutes. The sensory state of the minced meat after chopping should be: milky white and rose red color, with normal meat filling aroma, good oiliness, stable emulsification, certain viscosity and ductility, and no large white auxiliary material particles, fascia, etc.
05 Precautions for chopping
(1) Inspection before chopping Before starting work, the chopper, meat grinder and its blade used in production should be checked to see if they are operating normally, whether the parts are in place, whether the blade is absolutely sharp, whether the temperature detection equipment is in place, whether other machines and equipment are in good condition, and whether the entire chopper is guaranteed to operate in a hygienic state.
(2) The temperature of each link of chopping should not be too high or too low, otherwise it is easy for the staff to misjudge the degree of chopping. In addition, in controlling the chopping temperature, it is not advisable to simply add ice chips, ice water or ice salt water to cool it down, otherwise it is easy to cause excessive ice water, which will exceed the water holding capacity of lean meat, soy protein and starch, making the product soft and inelastic. Therefore, in actual operation, ice water must be added in batches and in several times. Do not add all the water to the stuffing at once or twice, especially when the stuffing is about to be chopped and mixed into shape. It is a taboo to add a large amount of water at once. At the same time, because the freezing point of salt water is low, it can not freeze at -3℃, so it can reduce the chopping temperature and prevent the chopping knife from being worn due to the hardness of ice chips. However, it should be noted that the total amount of salt in the salt water used should be equal to the amount of salt in the qualified product.
(3) pH value of meat The pH value of meat affects the water retention of muscle protein. When the pH value is close to the isoelectric point of actomyosin 5.4, that is, the positive charge in actin is neutralized by the negative charge generated by the muscle due to death and stiffness, and only the excess positive charge is used to retain water molecules. At this time, the water retention and swelling of the muscle are minimal. Choosing meat with a pH value less than 5.6 as raw material can affect the cohesiveness and water retention of the meat, which directly affects the chopping effect. Therefore, the pH value of the meat filling should be tested during the chopping process to evaluate the water retention of the meat filling.
(4) Timely transportation of minced meat after chopping When the temperature inside the minced meat rises to above 12°C, it is suitable for microbial reproduction, which not only makes it difficult to sterilize later, but also the remaining microorganisms proliferate rapidly under the high temperature and high humidity conditions after sale, decomposing starch, fat, protein, producing acid and gas, and finally swelling the bag and making the product lose its edible value. In summary, as low-temperature meat products become increasingly popular among the public, the chopping process has gradually gained the attention of technicians. Among them, the chopping temperature, time, order of adding raw materials and auxiliary materials, and the degree of chopping all have an important impact on the quality of meat products. With the advancement of science and technology, the intelligence of machinery and strict management of enterprises, scientific formulas plus reasonable chopping processes will surely produce low-temperature meat products that are suitable for various consumer groups.
