One winter, my classmates and I went back to my hometown in Jingzhou. I saw someone wearing plastic clothes without breasts digging lotus roots in the cold pond, sunset, smoke trees, withered lotus flowers and lotus root diggers. The scene was indescribable sadness. Li Bai wrote: "If you pick a lotus girl by the Xiye River, you will smile at the lotus." It can be said that everyone loves a lotus girl and no one can recognize a lotus root digger. My classmate's mother made us lotus root ribs soup, and set up a red mud stove in the main room with a casserole on it. The lotus root sparerib soup has been stewed for several hours, and thousands of chrysanthemums are cooked in the soup and eaten in the seasoning plate, which makes people shudder.
The pace of life in the city is getting faster and faster, and people have no time or patience to simmer a pot of good soup in a casserole. The appearance of electric pressure cooker facilitates people's life. So, how to cook a good soup like a casserole with an electric pressure cooker? The research of the College of Food Science and Technology of Huazhong Agricultural University answered this question.
The traditional lotus root ribs soup needs to be boiled in a casserole and then simmered for two or three hours. Because of the high pressure and high temperature, cooking soup in pressure cooker can greatly save time and energy, which is more suitable for the fast-paced life of modern people. However, a lot of research and practice show that the sensory evaluation of casserole stewed pork ribs soup is obviously better than that of pressure cooker stewed pork ribs soup, and the taste is more mellow. This shows that the process of cooking soup in pressure cooker needs to be improved. The research of Huazhong Agricultural University made a comparative study on the influence of different cooking conditions of electric pressure cooker and casserole on the quality of the final sparerib soup, which provided a reference for the improvement of cooking technology of electric pressure cooker.
Processing technology of casserole soup
In this study, firstly, the effects of different bone-water ratio and decocting time on the quality of ribs soup were analyzed by sensory evaluation, and then the best technological conditions of casserole soup were obtained. First, according to the mass ratio of spareribs to water of 1:3, 1:4 and 1:5, the soup was boiled for 3 hours, and lotus root pieces 1 were added 0 hour before the ceasefire. Then sensory evaluation was made by several evaluators, and finally it was concluded that the quality of soup was the best when the mass ratio of ribs to water was 1: 3. Considering that more water evaporates during the boiling process, in order to ensure more soup, the best bone-water ratio is finally determined 1:4. Sensory evaluation criteria are shown in the following table.
Table 1. Sensory evaluation standard of lotus root ribs soup
Source: The author arranged according to relevant research.
According to the ratio of ribs to water 1:4, six control groups were set up and boiled for 1.0, 1.5, 2.0, 2.5, 3.0 and 3.5 hours, respectively, and then sensory scores were made to determine the content of soluble protein in the soup. The result is shown in figure 1.
Figure 1. Effect of boiling time on the quality of soup (casserole). Source: The author studies and draws according to relevant literature.
It can be seen that with the extension of boiling time, the sensory score of soup showed an upward trend, and the content of soluble protein also increased gradually. However, after boiling for 3 hours, the sensory score and soluble protein content of the soup decreased slightly. This may be due to the fact that the protein in the ribs gradually dissolved in the first 3 hours of boiling, and after 3 hours, a large amount of fat in the ribs dissolved, resulting in a slightly greasy taste of the soup, and the continuous heating also destroyed the protein to some extent.
To sum up, when the mass ratio of ribs to water is 1:4, stew for 3 hours, and lotus root slices are added 1 hour before the cease-fire, the quality of lotus root ribs soup made in casserole is the best.
Cooking technology of electric pressure cooker
The cooking technology of electric pressure cooker mainly analyzes the effects of the mass ratio of ribs to water, pressure and cooking time on the quality of soup. The comprehensive quality of ribs soup is analyzed by sensory evaluation, water-soluble protein content determination, texture analysis, chromaticity analysis and electronic nose flavor determination.
The best bone-water ratio of casserole ribs soup is 1:4. Because the whole process of electric pressure cooker cooking soup is in a closed environment, less water evaporates, so 1:3 is the best bone-water ratio for electric pressure cooker cooking soup.
Effect of pressure on soup quality
According to the above ratio of bone to water, put the spareribs in an electric pressure cooker, cook for 45 minutes under different pressures, then put them in lotus root blocks, continue to cook for 15 minutes under the same pressure, then stop the fire, and then conduct sensory evaluation and soluble protein content determination to investigate the effects of different pressures on the quality of the soup. The results are shown in Figure 2.
Figure 2. Effect of pressure on soup quality (electric pressure cooker). Source: The author studies and draws according to relevant literature.
As can be seen from Figure 2, the sensory score of soup is basically consistent with the change trend of soluble protein content, which generally increases first, then decreases and then increases with the increase of pressure. The pressure here refers to gauge pressure, which is numerically equal to the difference between absolute pressure and atmospheric pressure. Below 20kPa, with the increase of pressure, the soluble protein content of soup increased; In the range of 20 ~ 50 kPa, the content of soluble protein decreased with the increase of pressure. Above 50kPa, the soluble protein content increased with the increase of pressure, and finally stabilized.
The greater the pressure, the greater the boiling point of water, so the most direct influence of pressure is cooking temperature, which will affect the solubility of protein. Protein molecules have hydrophobic groups and hydrophilic groups. Polar hydrophilic groups have strong hydration with polar water molecules, and hydrophobic groups gather due to hydrophobic effect, which makes protein molecules fold, and hydrophobic groups are wrapped inside, which makes protein soluble in water. This process makes the entropy of water molecules increase and the free energy decrease.
At low temperature, the solubility of protein can be improved by increasing the temperature properly, so the soluble protein content of soup increases. When the temperature continues to rise, the secondary structure of protein is destroyed, and the hydrophobic groups inside are exposed, which enhances the hydrophobic effect, thus reducing the solubility of protein and the content of soluble protein in soup. When the temperature continues to rise, the content of soluble protein increases again, which may be related to the destruction of hydrophobic groups in protein, or to the destruction of the physical properties of ribs, so that they can be fully dissolved in water. The more basic principle needs further study. Reference to "protein's Free Folding Thermodynamic Hypothesis" first put forward by Anfinsen (1972 Nobel Prize in Chemistry) may help to further explain the changing mechanism of protein in the cooking process.
Christian anfinsen, image source: Nobel Prize.
Effect of decocting time on soup quality
As can be seen from Figure 2, the quality of soup is better when the pressure is 20kPa and 70kPa, so the influence of boiling time on the quality of soup under these two pressure conditions is investigated respectively. The boiling time is set to 15 ~ 90 min, and the time interval is 15min. Lotus root slices were added 65438 05 minutes before the cease-fire, and then the sensory score and soluble protein content were determined. The result is shown in Figure 3.
Figure 3. Effect of cooking time on soup quality (electric pressure cooker). Source: The author studies and draws according to relevant literature.
As can be seen from Figure 3, in the first 45 minutes of cooking, the quality of soup improved very rapidly, and after 45 minutes of cooking, the change trend of soup quality tended to be flat, even slightly decreased after 75 minutes of cooking. It can be seen that the soup reached the critical point after boiling for 45 minutes, and the curve of 70kPa was above the curve of 20kPa 45 minutes before boiling, so the quality of the soup was better. When boiling for 45 minutes, the curve of 70kPa and the curve of 20kPa intersect, and the whole curve changes to the fitting trend. This shows that in the first 45 minutes of boiling, pressure is an important factor affecting the quality improvement rate of soup, but after 45 minutes of boiling, pressure is no longer an important factor affecting the quality change rate of soup. Therefore, the boiling process of ribs soup can be divided into two working conditions: high pressure boiling and low pressure boiling. So we can sum up four factors that affect the quality of soup: A high pressure, B high pressure time, C low pressure, D low pressure time.
In order to obtain the best technology of making lotus root ribs soup with electric pressure cooker, four factors of ABCD can be orthogonal tested. The experimental parameters are shown in Table 2 below.
Table 2. Factors and levels of orthogonal test
Therefore, the orthogonal test table of L9 (3 4) can be designed, and the test results can be obtained according to the test table. As shown in Table 3.
Table 3. Design and test results of orthogonal test table
Source: The author studies and draws according to relevant literature.
It can be seen that the comprehensive quality of sparerib soup made by A2B 1C2D3 process scheme is the best, that is, it is boiled at 70kPa for 20 minutes and then at 20kPa for 45min minutes.
Through sensory evaluation, the scores of pork ribs soup made by this electric pressure cooker cooking technology and pork ribs soup made by casserole are very close. Specifically, compared with the casserole pork ribs soup, the pork ribs soup made by electric pressure cooker has less color and taste, but better aroma, which may be because the electric pressure cooker is in a closed environment with less oxygen, and the formation of color and flavor substances is not as favorable as that of purple casserole, but the closed environment also reduces the escape of aroma substances.
Table 4. Comparison of sensory scores of lotus root ribs soup with different techniques
Source: The author studies and draws according to relevant literature.
The soup was detected and analyzed by colorimeter and texture analyzer, which showed that the pork ribs soup made by casserole was brighter in color and thicker in soup. The pork quality and color of pork ribs soup made by electric pressure cooker are slightly pale, which may be due to the low oxidation degree of raw materials caused by the closed cooking process. From the taste point of view, the ribs cooked in casserole are more elastic, and the ribs cooked in electric pressure cooker are more soft and rotten.
The aroma characteristics of soup were detected and analyzed by electronic nose, and it was found that the aroma characteristics of pork ribs soup boiled in electric pressure cooker and casserole were highly similar.
To sum up, using electric pressure cooker to make lotus root ribs soup under reasonable technological conditions (70kPa 20min, 20kPa 45min) can achieve the same effect as casserole. This study not only provides an important basis for the improvement of cooking technology and the convenience of people's lives, but also provides an important direction for the research and development, design and technological innovation of cooking equipment in the future. Intelligent pressure cooker should have at least several functions: adjustable pressure, adjustable oxygen, automatic matching of the optimal pressure change curve with cooking time, etc.
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