Effect of dumpling wrapper improver on quick-frozen dumplings

As a traditional delicacy, quick-frozen dumplings are prone to skin cracking, drying, hardening, browning, etc. Frozen cracking is the most critical quality problem. According to research, the addition of dumpling wrapper improver to the production of quick-frozen dumplings is helpful to improve the frost cracking resistance of quick-frozen dumplings. There are many factors inducing the cracking of quick-frozen dumplings, such as repeated freezing, flour quality, water content, temperature changes, etc.

First, the production theory of quick-frozen dumplings and the problem of frozen cracking

From the production practice of quick-frozen food, the temperature in the cold chain environment is usually relatively low, mainly at-30 C, quick freezing is completed within 15-30min, and storage and circulation are carried out in small packages at-18 C .. As the temperature of the whole cold chain of the quick-frozen boiled dumplings is relatively low, the water in the boiled dumplings will form ice crystals, thus achieving the goal of inhibiting microbial activity under the condition of lacking the liquid water required by due biochemical reaction, thus improving the quality of the quick-frozen boiled dumplings and maintaining the original nutrition. However, for quick-frozen dumplings, the freezing cracking rate is an important indicator related to the quality of quick-frozen dumplings. During the production process of quick-frozen dumplings, the dumplings are quickly frozen in a short period of time, the skin temperature drops sharply, and the plasticity is enhanced, while the inside of the stuffing freezes slowly. During the freezing process, some horizontal or liquid ice crystals may be generated in the water inside the stuffing, causing the dumpling wrapper to expand and crack. Under the quick-freezing processing technology, the appearance of the product caused by the freezing crack will also affect the quality of the dumplings.

Second, the analysis of the cracking factors of quick-frozen dumplings

(a) dumpling flour quality

From the production process and technology of quick-frozen dumplings, the flour used should have the following requirements. One is lower ash content. Ash is mainly cellulose, which constitutes flour, and reflects the processing precision of flour. If cellulose is too high, it may destroy the network strength of gluten. In addition, cellulose absorbs more water, which is more likely to bring about the accumulation of water in the dumpling skin, causing ice crystals to expand and crack during freezing. Second, wet gluten is more important. According to the content of flour wet gluten, under the quick freezing process, when the content of wet gluten is less than 2 6%, the cracking problem of dumpling wrappers after freezing is prominent. When the wet gluten content is higher than 29%, there is basically no cracking problem of dumpling wrappers. Analysis of the causes is related to the amount of frozen water ice crystals caused by different wet gluten contents. When the specific gravity of wet gluten is high, the ice crystal expansion stress it bears is high, while when the specific gravity of wet gluten is low, the ice crystal expansion stress of water in stuffing exceeds the bearing capacity of dumpling wrappers and cracks occur. The third is high protein content. Through the analysis of the protein content of flour from different manufacturers, it is found that the protein enhances the elasticity and extensibility of flour in the process of gluten formation, which is helpful to reduce the swelling stress of water in the filling caused by "ice crystals".

(B) the impact of water

In the production of quick-frozen dumplings, the amount of water added and the quality of the water are very important. In the dough mixing process, if the moisture content of the dough is increased, the viscosity of the dough will be enhanced and the cracking rate will be reduced, but the process operation difficulty will be increased. For example, the roller and the conveyor belt may stick together when making dumpling wrappers, affecting the quality of dumpling wrappers. On the one hand, the conveying air permeability can be enhanced by changing the material of the conveying belt and using canvas material; on the other hand, the smoothness of dumpling wrappers can be enhanced by adding the amount of dry flour, especially using modified starch, and the adhesion problem with the rolling roller and the conveying belt can be reduced. Similarly, in the control of water content, we should also pay attention to the proportion of gluten. Experiments show that when the moisture content of the dough is high, it is favorable for yeast propagation and easy to expand, but when the water content is low, the dough is easy to harden, yeast fermentation effect is not good, and the subsequent frost cracking problem will also be affected. In addition, enough attention should be paid to the water quality problem. Under different regional conditions, the water quality conditions are quite different. The use of soft water to make dough is easy to soften gluten and difficult to wake up, but it will lead to gluten hardening and will also affect dough awakening, especially the influence of inorganic salt content in hard water, which will affect the viscoelasticity and extensibility of gluten. The high content of some inorganic salts will also affect the combination of starch and inorganic salts, causing the dough to become brittle and hard. Usually, tap water is used in the production of industrial dumplings.

(3) Changes in water temperature

During dough mixing, changes in water temperature will also affect gluten and dough processing properties. From the analysis of dough composition, gluten and protein will swell after absorbing water. At 30°C, the protein absorbs water best, while at 40°C, too high a temperature will affect the chemical stability of the protein. When the temperature rises further, it will affect the non-polar groups of flour, and the protein will denature and cannot be used. Usually, due to the hydrophobic phenomenon of non-polar groups caused by high water temperature during flour mixing, protein molecules cannot be adsorbed and gluten cannot be formed. Some industrial quick-frozen dumpling production enterprises choose deep underground water with a relatively constant water temperature of less than 30C, which has good hydrophilicity, will not cause starch gelatinization and protein thermal denaturation, and will also improve the quality of dumpling wrappers and reduce the rate of frozen cracking.

(4) the influence of meat stuffing and water content

For the meat stuffing of quick-frozen dumplings, the amount of water added will also affect the freezing cracking rate. In the production process of quick-frozen dumplings, the change of temperature first freezes the dumpling wrapper, and then freezes the stuffing. If there is too much water in the stuffing, during the quick freezing process, the water in the meat stuffing crystallizes and expands, resulting in greater stress on the dumpling wrapper and increasing the frost cracking rate. However, when analyzing the taste index of meat fillings, too little water content will lead to deterioration of taste. Therefore, it is necessary to reasonably control the water content of the meat stuffing to enhance the taste and reduce the frost cracking rate.

III. Effect of Dumpling Skin Modifier on Frozen Cracking Rate of Quick-frozen Dumpling

(2) Production and Methods

In the process of making the fabric, 1,000 g of flour is added with dumpling wrapper modifier, and the mixture is fully stirred for about 5 min. Dissolve 440 mL of water into 3g of salt, fully dissolve, mix with flour raw materials, and turn on the dough mixer for 7min. After dough is kneaded and proofed for 2min, the dough is then loaded into a dough pressing machine to press the dough for 10 times. Then cut into 8-10cm wide strip noodles for later use. Pork is minced according to the ratio of fat to lean of 1: 1, totaling 500g; Add 50 g onion respectively; 350 g cabbage, 20 mL soy sauce, 20 mL peanut oil, salt, monosodium glutamate, cooking wine, etc. In the forming and making line of boiled dumplings, the ratio of skin to stuffing is adjusted to 1: 1 by using a bag-and-type boiled dumpling machine to make boiled dumplings, and after forming, the boiled dumplings are placed on a tray and transported to a freezing channel. In the freezing step, the surface of the dumplings is wetted by an automatic sprayer, and then the dumplings are sent into a -35 C quick-freezing tunnel, and the quick-freezing is delayed for 15 min. After the inside of the dumplings is cooled to -18 C, the frozen cracking condition of the quick-frozen dumplings is counted, all batches of the dumplings are inspected from the quick-freezing tunnel, and the selection standard of "cracks regardless of crack size and thickness" is determined to calculate the frozen cracking rate, wherein the frozen cracking rate = (frozen cracking number/total number) X100%.

(3) Results Analysis

The dumpling wrapper modifier is compounded with vegetable gum, emulsifier, antioxidant, modified starch, phosphate, etc. Through experiments, it can be found that the addition of the modifier improves the whiteness of the dumpling wrapper and ensures that the dumpling maintains a good hue. According to the data calculation, the frozen cracking rate of dumplings is obviously reduced after adding the dumpling wrapper modifier. The reason is that the emulsifier of the modifier helps to form a stable net structure on the dumpling wrapper, enhances the elasticity and toughness of quick-frozen dumplings, promotes balanced dispersion of crystals, and reduces expansion stress caused by water crystallization. Among them, vegetable gum and antioxidant have the function of reinforcing agent. With the increase of dosage, the frozen cracking rate of dumplings decreases obviously. However, the color of dumplings was significantly improved by the addition of compound phosphate.