Microwave and Conduction Combined Heating Method for Improving Gel Strength of Surimi Products

Abstract

The present invention discloses a microwave and conduction combined heating method for improving the gel strength of surimi products, belonging to the technical field of food processing. According to the present invention, surimi is first fully gelatinized by conduction heating, and then heated by microwave heating so that surimi gel can pass through a gel cracking zone quickly. This kind of microwave and conduction combined heating way can not only increase the gel strength of the surimi to achieve the desired elasticity, but also can save a lot of time and improve the production efficiency. Compared with ordinary microwave heating, the microwave and conduction combined heating method of the conduction and microwave heat preservation, i.e. holding the temperature of the surimi products for a period of time by adjusting the microwave power level at a specified temperature range, can effectively improve the gel strength of the surimi and comply with the new trend of applying microwave heating to surimi products.

Claims

1. A method for improving the gel strength of surimi products, comprising the following steps: obtaining surimi products from frozen surimi through performing thawing, empty chopping, salt chopping, spicery chopping, pasting, and forming-and-cooking; wherein the forming-and-cooking comprises forming a surimi paste with a specific shape after pasting by a grouting die or a manual extrusion method, heating by a microwave and conduction combined heating method, and obtaining the surimi products with high gel strength; wherein the microwave and conduction combined heating comprises: gelling for 20-40 min under a condition of 40-50 C. in a water bath, then rising the temperature of the surimi products to 802 C. at microwave power level of 31 W/g by using an intermittent heating method, and holding the temperature for 3 to 9 minutes.

2. The method for improving the gel strength of surimi products according to claim 1, wherein the microwave and conduction combined heating comprises: gelling for 30 min under a condition of 40 C. in a water bath by a conduction heating method, then rising the temperature of the surimi products to 80 C. at a microwave power level of 31 W/g by using the intermittent heating method, and holding the temperature for 7 min.

3. The method for improving the gel strength of surimi products according to claim 1, wherein the intermittent heating method comprises heating for 20 to 30 s with microwave and stopping heating for 20 to 30 s to form a cycle, repeating the cycle until surimi products are heated to 80-90 C., and holding the temperature for 51 min.

4. The method for improving the gel strength of surimi products according to claim 2, wherein the intermittent heating method comprises heating for 20 to 30 s with microwave and stopping heating for 20 to 30 s to form a cycle, repeating the cycle until surimi products are heated to 80-90 C., and holding the temperature for 51 min.

5. The method for improving the gel strength of surimi products according to claim 3, wherein the intermittent heating method comprises heating for 24 s with microwave, and stopping heating for 24 s to form a cycle, repeating the cycle until the surimi products are heated to 802 C., and holding the temperature for 51 min.

6. The method for improving the gel strength of surimi products according to claim 4, wherein the intermittent heating method comprises heating for 24 s with microwave, and stopping heating for 24 s to form is a cycle, repeating the cycle until the surimi products are heated to 802 C., and holding the temperature for 51 min.

7. The method for improving the gel strength of surimi products according to claim 1, wherein the thawing comprises thawing the frozen surimi stored at 20 C. for 10-14 h at 4 C. so that a surface temperature of a block of the surimi products is below 10 C., while a center temperature of the block of the surimi products is below 3 C.

8. The method for improving the gel strength of surimi products according to claim 2, wherein the thawing comprises thawing the frozen surimi stored at 20 C. for 10-14 h at 4 C. so that the surface temperature of a block of the surimi products is below 10 C., while the center temperature of the block of the surimi products is below 3 C.

9. The method for improving the gel strength of surimi products according to claim 1, wherein the empty chopping comprises: putting thawed surimi with a center temperature of less than or equal to 5 C. to a chopping machine for empty chopping for 2-3 min at a chopping machine cutter shaft rotation speed of 2000-3000 r/min in a chopping machine until surimi stick together, then adding 10.1% of phosphate to the surimi for continued chopping and mixing until no hard particles of surimi exist, and finally obtaining empty chopped surimi.

10. The method for improving the gel strength of surimi products according to claim 2, wherein the empty chopping comprises: putting the thawed surimi with a center temperature of less than or equal to 5 C. to a chopping machine for empty chopping for 2-3 min at a chopping machine cutter shaft rotation speed of 2000-3000 r/min until the surimi stick together, then adding 10.1% of phosphate to the surimi for continue chopping and mixing until no hard particles of surimi exist, and finally obtaining empty chopped surimi.

11. The method for improving the gel strength of surimi products according to claim 3, wherein the empty chopping comprises: putting the thawed surimi with a center temperature of less than or equal to 5 C. to a chopping machine for empty chopping for 2-3 min at a chopping machine cutter shaft rotation speed of 2000-3000 r/min until the surimi stick together, then adding 10.1% of phosphate to the surimi for continue chopping and mixing until no hard particles of surimi exist, and finally obtaining empty chopped surimi.

12. The method for improving the gel strength of surimi products according to claim 4, wherein the empty chopping comprises: putting the thawed surimi with center temperature being less than or equal to 5 C. to a chopping machine for empty chopping for 2-3 min at a chopping machine cutter shaft rotation speed of 2000-3000 r/min until the surimi stick together, then adding 10.1% of phosphate to the surimi for continue chopping and mixing until no hard particles of surimi exist, and finally obtaining empty chopped surimi.

13. The method for improving the gel strength of surimi products according to claim 5, wherein the empty chopping comprises: putting the thawed surimi with center temperature of less than or equal to 5 C. to a chopping machine for empty chopping for 2-3 min at a chopping machine cutter shaft rotation speed of 2000-3000 r/min until the surimi stick together, then adding 10.1% of phosphate to the surimi for continue chopping and mixing until no hard particles of surimi exist, and finally obtaining empty chopped surimi.

14. The method for improving the gel strength of surimi products according to claim 8, wherein the empty chopping is as follows: putting the thawed surimi with center temperature being less than or equal to 5 C. to a chopping machine for empty chopping for 2-3 min at a chopping machine cutter shaft rotation speed of 2000-3000 r/min until the surimi stick together, then adding 10.1% of phosphate to the surimi for continue chopping and mixing until no hard particles of surimi exist, and finally obtaining empty chopped surimi.

15. The method for improving the gel strength of surimi products according to claim 1, wherein the salt chopping comprises: adding salt to the surimi after empty chopping at a ratio of 2-4% of the weight of the surimi, and performing salt chopping for 3-8 min at a cutter shaft rotation speed of 2000-3000 r/min until the surimi is completely dispersed and the paste becomes viscous.

16. The method for improving the gel strength of surimi products according to claim 14, wherein the salt chopping comprises: adding salt to the surimi after empty chopping at a ratio of 2-4% of the weight of the surimi, and performing salt chopping for 3-8 min at a cutter shaft rotation speed of 2000-3000 r/min until the surimi is completely dispersed and the paste becomes viscous.

17. The method for improving the gel strength of surimi products according to claim 1, wherein the spicery chopping comprises: adding 181% of soy emulsified paste to the surimi after salt chopping, then performing mixed chopping for 4-10 min at a cutter shaft rotation speed of 3000-4000 r/min, adding spices until the paste is fully mixed without particles touched by hands; wherein a soy emulsified paste is a fine emulsified paste made by soy protein, chicken skin and ice water at a ratio of 1 to 1 to 5 in a chopping pan through emulsifying for 5-6 min; wherein the pasting comprises adding 141% of starch after spicery chopping, and performing mixed chopping for 2-4 min at a cutter shaft rotation speed of 2000-3000 r/min so that the starch is distributed into surimi evenly, so as to obtain a paste of the surimi.

18. The method for improving the gel strength of surimi products according to claim 16, wherein the spicery chopping comprises: adding 181% of soy emulsified paste to the surimi after salt chopping, then performing mixed chopping for 4-10 min at a cutter shaft rotation speed of 3000-4000 r/min, adding spices until the paste is fully mixed without particles touched by hands; wherein a soy emulsified paste is a fine emulsified paste made by soy protein, chicken skin and ice water at a ratio of 1 to 1 to 5 in a chopping pan through emulsifying for 5-6 min; wherein the pasting comprises adding 141% of starch to the material after spicery chopping, and perform mixed chopping for 2-4 min at a cutter shaft rotation speed of 2000-3000 r/min so that the starch is distributed into surimi evenly, so as to obtain a paste of the surimi product.

19. The method for improving the gel strength of surimi products according to claim 1, wherein the surimi products comprise fish intestines, fish sticks, fish sausages, crab sticks, fish noodles, fish cakes, fish rolls and others with surimi as the main raw material; wherein raw material fishes of the surimi comprises white fishes silver carp, pagrosomus major or nemipterus virgatus, red fishes skipjack tuna, saury, mackerel or sardine, as well as cuttlefish and shrimp.

20. The method for improving the gel strength of surimi products according to claim 18, wherein the surimi products comprise fish intestines, fish sticks, fish sausages, crab sticks, fish noodles, fish cakes, fish rolls and others with surimi as the main raw material; wherein raw material fishes of the surimi include white fishes silver carp, pagrosomus major or nemipterus virgatus, red fishes skipjack tuna, saury, mackerel or sardine, as well as cuttlefish and shrimp.

21. Surimi products made by the method according to claim 1.

22. Surimi products made by the method according to claim 20.

Description

BRIEF DESCRIPTION OF FIGURES

[0023] FIG. 1 shows a heat preservation curve of a microwave combined conduction heating method;

[0024] FIG. 2 shows the influence of different microwave combined conduction heating conditions on the quality of surimi products. A represents the gel strength at a microwave power level of 3 W/g, B represents the gel strength at a microwave power level of 5 W/g, C represents the gel strength at a microwave power level of 7 W/g; a represents the water-holding capacity at a microwave power level of 3 W/g, b represents the water-holding capacity at a microwave power level of 5 W/g, c represents the water-holding capacity at a microwave power level of 7 W/g;

[0025] FIG. 3 shows an optimization diagram of a conventional microwave heating method, A: gel strength, B: water-holding capacity;

[0026] FIG. 4 shows a breaking force diagram of surimi products treated with different heating methods under an optimal condition;

[0027] FIG. 5 shows a breaking distance diagram of surimi products treated with different heating methods under an optimal condition;

[0028] FIG. 6 shows a gel strength diagram of surimi products treated with different heating methods under an optimal condition;

[0029] FIG. 7 shows a photograph of fish intestines cooked with different heating methods under an optimal condition; and

[0030] FIG. 8 shows a scanning electron micrograph (1000) of surimi products after gel cooked with different heating methods under an optimal condition; in FIGS. 4 to 8, A represents a microwave combined conduction heating method of the present invention, B represents a conventional microwave heating method, and C represents a conventional two-step step conduction heating method.

DETAILED DESCRIPTION

[0031] The surimis used in the following embodiments are products available on the markets, for example, the frozen pagrosomus major surimi sold by Ningbo Jinhai Aquatic Product & Food Co., Ltd.

[0032] High-speed emulsifiers used in the following embodiments are products available on the markets, for example, FA25 high-speed emulsifiers sold by FLUKO.

[0033] Chopping machines used in the following embodiments are Shenfa brand high-speed chopping machines sold by Shanghai Shenfa Machinery Co., Ltd. or XiaoJin brand high-speed chopping machines sold by Hebei XiaoJin Machinery Manufacturing Inc.

Embodiment 1

[0034] This embodiment adopts an optimized microwave combined conduction heating method, which is as follows:

[0035] A. Thawing

[0036] Thawing the frozen pagrosomus major surimi of Ningbo Jinhai Aquatic Product & Food stored at 20 C. for 10-14 h at 4 C., so that the surface temperature of the surimi block is below 10 C. while the center temperature of the surimi block is below 3 C.

[0037] B. Soy Emulsified Paste

[0038] Adding soy protein, chicken skin and ice water at a ratio of 1 to 1 to 5 to a chopping pan, and emulsifying for 5-6 min until the materials become fine emulsified paste.

[0039] C. Empty Chopping

[0040] Putting the thawed surimi with center temperature being less than or equal to 5 C. to a chopping machine for empty chopping for 2-3 min at a chopping machine cutter shaft rotation speed of 2000-3000 r/min until the surimis stick together, then adding 10.1% of phosphate to the surimis for continue chopping and mixing until no hard particles of surimis exist, and finally obtaining empty chopped surimi.

[0041] D. Salt Chopping

[0042] Adding salt to the surimi after empty chopping obtained in step C at a ratio of 2-4% of the weight of the surimi, and performing salt chopping for 3-8 min at a cutter shaft rotation speed of 2000-3000 r/min until the surimi is completely dispersed and the paste becomes viscous.

[0043] E. Spicery Chopping

[0044] Adding 181% of soy emulsified paste obtained in step C to the surimi after salt chopping obtained in step D, then performing mixed chopping for 4-10 min at a cutter shaft rotation speed of 3000-4000 r/min, and adding spices until the paste is fully mixed without particles touched by hands.

[0045] F. Pasting

[0046] Adding 141% of starch in the step E, and performing mixed chopping for 2-4 min at a cutter shaft rotation speed of 2000-3000 r/min so that the starch is distributed into the surimi system evenly to obtain the surimi product paste.

[0047] G. Forming and Cooking

[0048] The surimi paste obtained in step F is made into special shape by means of a grouting die or a manual extrusion method. The formed surimi products are gelatinized for 30 min in a 38-42 C. (preferably 40 C.) water bath in a conduction heating way, then the surimi products after water bath conduction heating undergo intermittent heating to 70, 80, 90 C. at the power level of 31 W/g, 51 W/g, 71 W/g (preferably 3 W/g) and keep warm for 3-9 min (preferably 80 C., 5 min).

[0049] The intermittent heating is to heat for 24 s by microwave heating and stop for 24 s, then repeat the procedure until the temperature reaches the set temperature.

[0050] The microwave heating temperature is detected online by fiber probes provided by FISO, Canada. When the temperature of microwave heating reaches the set temperature, the microwave stops heating. When the temperature is lower than the set temperature, the microwave continues to heat at the original power level until the set temperature is reached. This process is repeated at the set temperature for a certain period of time (FIG. 1). At the end of microwave heating, surimi products with higher gel strength are obtained. The optimum condition of the microwave combined conduction heating method: heating to 802 C. and holding 5 min at the power level of 31 W/g (FIG. 2). The holding process allows a fluctuation of 2 C. at the set temperature.

Embodiment 2

[0051] The difference between embodiment 2 and embodiment 1 is as follows: for the microwave combined conduction heating method, when the temperature of microwave heating reaches the set temperature, reduce the microwave power and continue to heat at a power level of - of the original power level, so as to maintain the central temperature of surimi to fluctuate at the set temperature for 2 C. If the temperature of the surimi is higher than the set temperature, reduce the power level at this time until the temperature returns to the set temperature and maintains for a period of time.

Comparative Embodiment 1

[0052] This comparative embodiment adopts optimized conditions of the conventional microwave heating method.

[0053] The specific procedures of comparative embodiment 1 are the same as those in embodiment 1, with the difference as follows: after the surimi is formed in step G, the conventional microwave heating mode is adopted, i.e., the formed fish tofu is heated at a constant power level of 3 W/g, 5 W/g, and 7 W/g in an intermittent heating way for 24 s, and stopped for 24 s, with a total microwave heating time of 24, 48, 72, 96, 120 s; after heating, the surimi products through conventional microwave heating are obtained. Wherein, the optimal condition of the conventional microwave heating method is power level of 5 w/g and heating time of 72 s.

Comparative Embodiment 2

[0054] The procedures of comparative embodiment 2 are the same as those in embodiment 1, with the difference as follows: in the forming and cooking step, a well-known conventional two-step heating mode is adopted rather than a microwave combined conduction heating mode, that is, first perform conduction heating for 30 min at 40 C. water bath, then take out and immediately put to 90 C. water bath to perform conduction heating for 20 min. At the end of heating, the surimi products of conventional conduction heating are obtained.

TABLE-US-00001 TABLE 1 Determiantion of whiteness of surimi products treated by different heating methods at an optimal condition Heating way L* a* b* Whiteness A 85.96 0.36 1.62 0.05 7.74 0.08 83.89 0.12 B 85.69 0.38 1.6 0.05 7.75 0.09 83.64 0.23 C 85.93 0.26 1.62 0.03 7.94 0.05 83.76 0.1

TABLE-US-00002 TABLE 2 Water loss rate and water-holding capacity of surimi products treated by different heating methods at an optimal condition Heating way Water loss rate % Water-holding capacity % A 4.06 0.38 73.96 0.27 B 4.25 0.35 72.56 0.36 C 3.89 0.29 69.02 0.13

[0055] In the tables above, A represents microwave combined conduction heating method in the present invention, B represents conventional microwave heating way, and C represents conventional two-step conduction heating method.