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 one or more of thawing, chopping, chopping with salt, chopping with spices, and pasting, and forming-and-cooking the surimi product by: a) forming a surimi paste with a specific shape after pasting with a grouting die or a manual extrusion apparatus; b) gelling for 20 to 40 minutes under at 40? C. to 50? C. in a water bath, c) heating for 20 second to 30 seconds in a microwave followed by no heating for 20 seconds to 30 seconds to form a cycle at a microwave power level of 3?1 W/g; d) repeating the cycle of step c) until the surimi products are heated to 80? C.?2? C.; and e) holding the temperature for 5?1 minutes, thereby obtaining surimi products with high gel strength.

2. The method for improving the gel strength of surimi products according to claim 1, wherein the method comprises: gelling for 30 minutes at 40? C. in a water bath by a conduction heating method, and raising the temperature of the surimi products to 80? C. at a microwave power level of 3?1 W/g by intermittent heating.

3. The method for improving the gel strength of surimi products according to claim 1, wherein the cycle comprises: heating for 24 seconds with a microwave followed by no heating for 24 seconds.

4. The method for improving the gel strength of surimi products according to claim 1, wherein thawing comprises thawing the frozen surimi stored at ?20? C. for 10 to 14 hours at 4? C. such 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.

5. The method for improving the gel strength of surimi products according to claim 2, wherein thawing comprises thawing the frozen surimi stored at ?20? C. for 10 to 14 hours at 4? C. such 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.

6. The method for improving the gel strength of surimi products according to claim 1, wherein chopping comprises: inserting thawed surimi with a center temperature of less than or equal to 5? C. into a chopping machine for to 3 minutes at a chopping machine cutter shaft rotation speed of 2000 to 3000 rotations per minute until the surimi sticks together, then adding 1?0.1% of phosphate to the surimi for continued chopping and mixing until no hard particles of surimi exist.

7. The method for improving the gel strength of surimi products according to claim 2, wherein chopping comprises: inserting thawed surimi with a center temperature of less than or equal to 5? C. into a chopping machine for 2 to 3 minutes at a chopping machine cutter shaft rotation speed of 2000 to 3000 rotations per minute until the surimi sticks together, then adding 1?0.1% of phosphate to the surimi for continue chopping and mixing until no hard particles of surimi exist.

8. The method for improving the gel strength of surimi products according to claim 1, wherein chopping comprises: inserting thawed surimi with a center temperature of less than or equal to 5? C. into a chopping machine for 2 to 3 minutes at a chopping machine cutter shaft rotation speed of 2000 to 3000 rotations per minute until the surimi sticks together, then adding 1?0.1% of phosphate to the surimi for continue chopping and mixing until no hard particles of surimi exist.

9. The method for improving the gel strength of surimi products according to claim 3, wherein chopping comprises: inserting the thawed surimi with center temperature of less than or equal to 5? C. into a chopping machine for 2 to 3 minutes at a chopping machine cutter shaft rotation speed of 2000 to 3000 rotations per minute until the surimi sticks together, then adding 1?0.1% of phosphate to the surimi for continue chopping and mixing until no hard particles of surimi exist.

10. The method for improving the gel strength of surimi products according to claim 5, wherein chopping comprises: inserting thawed surimi with center temperature being less than or equal to 5? C. to a chopping machine for 2 to 3 minutes at a chopping machine cutter shaft rotation speed of 2000 to 3000 rotations per minute until the surimi sticks together, then adding 1?0.1% of phosphate to the surimi for continue chopping and mixing until no hard particles of surimi exist.

11. The method for improving the gel strength of surimi products according to claim 1, wherein chopping with salt comprises: adding salt to the surimi after chopping at a ratio of 2 to 4% of the weight of the surimi, and chopping with the salt for 3 to 8 minutes at a cutter shaft rotation speed of 2000 to 3000 rotations per minute until the surimi is completely dispersed and the paste becomes viscous.

12. The method for improving the gel strength of surimi products according to claim 10, wherein chopping with salt comprises: adding salt to the surimi after chopping at a ratio of 2 to 4% of the weight of the surimi, and chopping with the salt for 3 to 8 minutes at a cutter shaft rotation speed of 2000 to 3000 rotations per minute until the surimi is completely dispersed and the paste becomes viscous.

13. The method for improving the gel strength of surimi products according to claim 1, wherein: i) chopping with spices comprises: adding 18?1% of soy emulsified paste to the surimi after chopping with salt, then chopping for 4 to 10 minutes at a cutter shaft rotation speed of 3000 to 4000 rotations per minute, and adding spices until the paste is fully mixed without particles touched by hands; wherein the soy emulsified paste is an emulsified paste comprising soy protein, chicken skin, and ice water added at a ratio of 1 to 1 to 5 in a chopping pan through emulsifying for 5 to 6 minutes; ii) pasting comprises: adding 14?1% of starch after chopping with spices, and chopping for 2 to 4 minutes at a cutter shaft rotation speed of 2000 to 3000 rotations per minute such that the starch is distributed into the surimi evenly.

14. The method for improving the gel strength of surimi products according to claim 12, wherein: i) chopping with spices comprises: adding 18?1% of soy emulsified paste to the surimi after chopping with salt, then chopping for 4 to 10 minutes at a cutter shaft rotation speed of 3000 to 4000 rotations per minute, and adding spices until the paste is fully mixed without particles touched by hands; wherein the soy emulsified paste is a fine emulsified paste comprising soy protein, chicken skin, and ice water at a ratio of 1 to 1 to 5 combined in a chopping pan through emulsifying for 5 to 6 minutes; ii) pasting comprises: adding 14?1% of starch to the material after chopping with spices, and chopping for 2 to 4 minutes at a cutter shaft rotation speed of 2000 to 3000 rotations per minute such that the starch is distributed into surimi evenly.

15. 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; and wherein the raw material comprises silver carp, pagrosomus major, Nemipterus virgatus, skipjack tuna, saury, mackerel, sardine, cuttlefish, and/or shrimp.

16. The method for improving the gel strength of surimi products according to claim 14, 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 the raw material comprises silver carp, pagrosomus major, Nemipterus virgatus, skipjack tuna, saury, mackerel, sardine, cuttlefish, and/or shrimp.

17. The method of claim 1, wherein the chopping is performed using a Shenfa brand high-speed chopping machine or XiaoJin brand high-speed chopping machine.

Description

BRIEF DESCRIPTION OF FIGURES

(1) FIG. 1 shows a heat preservation curve of a microwave combined conduction heating method;

(2) 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;

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

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

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

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

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

(8) 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

(9) 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.

(10) High-speed emulsifiers used in the following embodiments are products available on the markets, for example, FA25 high-speed emulsifiers sold by FLUKO.

(11) 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

(12) This embodiment adopts an optimized microwave combined conduction heating method, which is as follows:

(13) A. Thawing

(14) 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.

(15) B. Soy Emulsified Paste

(16) 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.

(17) C. Empty Chopping

(18) 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 1?0.1% of phosphate to the surimis for continue chopping and mixing until no hard particles of surimis exist, and finally obtaining empty chopped surimi.

(19) D. Salt Chopping

(20) 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.

(21) E. Spicery Chopping

(22) Adding 18?1% 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.

(23) F. Pasting

(24) Adding 14?1% 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.

(25) G. Forming and Cooking

(26) 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 3?1 W/g, 5?1 W/g, 7?1 W/g (preferably 3 W/g) and keep warm for 3-9 min (preferably 80? C., 5 min).

(27) 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.

(28) 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 80?2? C. and holding 5 min at the power level of 3?1 W/g (FIG. 2). The holding process allows a fluctuation of 2? C. at the set temperature.

Embodiment 2

(29) 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

(30) This comparative embodiment adopts optimized conditions of the conventional microwave heating method.

(31) 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

(32) 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.

(33) 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

(34) 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

(35) 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.