Microwave Thawing Process for Salmon

Abstract

Provided is a continuous process to thaw salmon, by means of microwaves, where the salmon, once thawed, maintains its organoleptic, physical and biochemical characteristics, identical or superior to that of fresh salmon, obtaining a temperature in its thermal center of between 26.60 to 30.20 F. (3 C. to 1 C.). The process is carried out in a thawing tunnel that has an entrance and an exit, between which a conveyor belt is located, on which are deposited the boxes. The process includes the steps of (a) place said boxes into the tunnel at an initial temperature between 3.2 to 12.20 F. (16 C. and 11 C.); (b) advance said boxes towards the interior of the tunnel at a speed between 1,800 and 2,500 mm/min; (c) irradiating the boxes with microwaves at a power of between 35 to 70 Kilowatts for 1.5 to 2.4 minutes.

Claims

1. A continuous process to thaw salmon meat, salmon fillets or gutted whole salmon, by means of microwaves, where the salmon meat, salmon fillets or gutted whole salmon, once thawed, are at least identical to salmon meat, salmon fillets or gutted whole salmon, which have not been previously frozen, where said process is carried out in a thawing tunnel that has an entrance and an exit, between which a conveyor belt is located, on which are deposited boxes containing the salmon meat, salmon fillets or gutted whole salmon, wherein the process comprises the steps of: (a) place said boxes containing the salmon meat, salmon fillets or gutted whole salmon into the tunnel, wherein the thermal center of the salmon meat, salmon fillets or gutted whole salmon is at an initial temperature between 3.2 to 12.20 F. (16 C. and 11 C.), wherein the salmon meat, salmon fillets or gutted whole salmon enters the tunnel in the boxes, and wherein said boxes weigh between 22 and 66 lbs (10 and 30 kg); (b) advance the boxes containing the salmon meat, salmon fillets or gutted whole salmon towards the interior of the tunnel at a speed between 1,800 and 2,100 mm/min; (c) irradiating the boxes containing the salmon meat, salmon fillets or gutted whole salmon with microwaves at a power of between 35 to 70 Kilowatts for 1.7 to 2 minutes, until the temperature of the thermal center of the salmon meat, salmon fillets or gutted whole salmon is between 26.60 to 30.20 F. (3 C. to 1 C.).

2.-5. (canceled)

Description

BRIEF DESCRIPTION OF DRAWINGS

[0029] The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0030] The accompanying drawings are included to provide a greater understanding of the invention and constitute a part of this description and show one of the preferred executions.

[0031] FIG. 1 corresponds to a photograph that shows two cooking zones of a whole salmon when it is subjected to a radiofrequency thawing process.

[0032] FIG. 2 corresponds to a photograph that shows three cooking zones for salmon fillets when they are subjected to a radiofrequency defrosting process.

[0033] FIG. 3 corresponds to a photograph showing two cooking zones for salmon fillets when they are subjected to a radiofrequency defrosting process.

[0034] FIG. 4 shows a perspective view of a thawing tunnel, said tunnel having a conveyor belt inside, which allows the transit of packages or boxes with salmon.

[0035] FIG. 5 shows a cross-sectional perspective view of a thawing tunnel, said tunnel having a conveyor belt inside, which allows the transit of packages or boxes with salmon.

[0036] FIG. 6 shows a cross-sectional perspective view of a thawing tunnel, said tunnel having a conveyor belt inside, in which a package or box with salmon enters the tunnel, to begin its journey through the microwaves.

[0037] FIG. 7 shows a cross-sectional perspective view of a thawing tunnel, said tunnel having a conveyor belt inside, in which a package or box with salmon leaves the tunnel, to finish its passage through the microwaves.

[0038] FIG. 8 shows a ruler with the Salmofan salmon color scale.

[0039] FIG. 9 is a graph showing the comparative results of the mesophilic aerobic count in Colony Forming Unit per gram of product (CFU/g) for skin-on salmon fillets from the prior art processes and the process of the present invention.

[0040] FIG. 10 is a graph showing the comparative results of the mesophilic aerobic count in Colony Forming Unit per gram of product (CFU/g) for skin-on salmon fillets from the prior art processes and the process of the present invention.

[0041] FIG. 11 is a graph showing the comparative results of mesophilic aerobic count in Colony Forming Unit per gram of product (CFU/g) for fresh skinless salmon fillets from the prior art processes and the process of the present invention.

[0042] FIG. 12 is a graph showing the comparative results of dynamic shrinkage for 4-5 Lb. (1.81 to 2.26 kg) skin-on salmon fillets from the prior art processes and the process of the present invention.

[0043] FIG. 13 is a graph showing the comparative dynamic shrinkage results for 4-5 Lb. (1.81 to 2.26 kg) skin-on salmon fillets from the prior art processes and the process of the present invention.

DESCRIPTION OF THE INVENTION

[0044] The present invention relates to a microwave thawing process for salmon, salmon fillets and gutted whole salmon, which makes it possible to obtain a product with organoleptic, physical and biochemical characteristics identical to or superior to salmon meat in the fresh state. More specifically, the present invention relates to a microwave thawing process for salmon, salmon fillets and gutted whole salmon, for subsequent processing, distribution and sale to the market as fresh salmon meat, where the thermal center of the product reaches a temperature between 26.60 to 30.20 F. (3 C. to 1 C.).

[0045] As noted above, salmon meat processing plants obtain whole salmon or gutted salmon fillets at the end of their production line. Both whole salmon and salmon fillets are packed in boxes and subjected to a freezing process, where the packaged product reaches a temperature of between 40.00 to 22 F. (40 C. to 30 C.) and, in its thermal center, reaches a temperature of 0.40 F. (18 C.). This packaged product is taken to cold stores to maintain the freezing temperature, awaiting the dispatch to the distribution centers.

[0046] This packaged and frozen product is transported to the distribution areas, where the salmon is thawed, reaching a thermal center temperature of between 26.60 to F. (3 C. to 1 C.), leaving the product ready to be marketed.

[0047] In a preferred embodiment of the present invention, the salmon is packed in boxes that are in a range between 22 and 66 lbs. (10 and 30 kg).

[0048] The thawing process is carried out in a thawing tunnel (1) that has an inlet (4) and an outlet (5), said tunnel (1) having at least one microwave emitter and in whose lower interior part is located a conveyor belt (2) that transports the boxes (3) with the product inside, as shown in FIGS. 4 and 5.

[0049] As exemplified in FIGS. 6 and 7, a box (3) weighing between 22 and 66 lbs. (10 and 30 kg) of product to be thawing enters the thawing tunnel (1) through the entrance (4) and on the conveyor belt (2). The boxes (3) enter the tunnel (1) with an initial temperature of between 3.2 to 12.20 F. (16 C. and 11 C.), beginning their displacement or advance at a speed of between 1800 to 2500 mm/min and, during their displacement on the conveyor belt (2), are irradiated with microwaves at a power of between 35 to 70 Kilowatts for 1.7 to 2.4 minutes. Upon reaching the exit (5) in the tunnel (1), the boxes (3) have a final temperature of between 26.60 to 30.20 F. (3 C. to 1 C.), which corresponds to the temperature of the final center of the product.

[0050] Comparative Results Tests

[0051] In order to demonstrate the superior results of the process proposed by the present invention with respect to the processes of the prior art, comparative tests showing these results will be shown below.

[0052] Thawing Process in a Controlled Environment Chamber

[0053] The salmon thawing process in a controlled environment chamber was carried out with the parameters shown in the following table 1:

TABLE-US-00001 TABLE 1 Controlled environment chamber thawing parameters Relative Product surface Thermal center Quantity Time Time Product humidity temperature temperature Lb (hours-min) (min) Whole 100% 35.60 F. 28.40 F. 12-14 2 hours 30 min 150 min (2 C.) (2 C.) Fillet 100% 35.60 F. 28.40 F. 4-5 1 hour 60 min (2 C.) (2 C.)

[0054] Thawing Process in Room

[0055] The salmon thawing process with constant temperature in the room was carried out with the parameters shown in the following table 2:

TABLE-US-00002 TABLE 2 Room thawing parameters Termal Room center Quantity Time Product temperature temperature Lb (hours) Whole 46.04 F. 30.20 F. 12-14 24 hours (7.8 C.) (1 C.) Fillet 46.04 F. 30.20 F. 4-5 7 hours (7.8 C.) (1 C.)

[0056] Thawing Process with Water Bath

[0057] The salmon thawing process with a water bath at a constant temperature was carried out with the parameters shown in the following table. 3:

TABLE-US-00003 TABLE 3 Water Bath Thawing Parameters Thermal Water center Quantity Time Product temperature temperature Lb (hours) Whole 50 F. 33.26 F. 12-14 9 hours (10 C.) (0.7 C.) Fillet 50 F. 33.26 F. 4-5 4 hours (10 C.) (0.7 C.)

[0058] Comparative analysis of weight loss of whole salmon and salmon fillets, according to the type of thawing process applied and according to the industrial facility of the Applicant:

[0059] A comparative analysis of the weight loss, after the thawing processes carried out in three processing plants of the Applicant, is shown in tables 4 to 6 below:

TABLE-US-00004 TABLE 4 Weight loss of whole salmon per plant Process with Process Water Microwave chamber controlled with room bath Facility process conditions temperature process Facility 1 0.041% 0.265% 0.626% 1.025% Facility 2 0.361% 0.603% 0.717% 1.466% Facility 3 0.178% 0.788% 0.266% 0.748% Overall total: 0.187% 0.552% 0.535% 1.032%

[0060] The microwave thawing process was applied to whole frozen salmon, finding that microwave thawing generates weight losses of 0.187%, which are lower than those generated by the water thawing process, which corresponds to 1.032%.

[0061] A certain similarity is observed in the result between the thawing treatments in a chamber under controlled conditions and the thawing treatment at room temperatures for whole salmon (known in the art as HON). This is explained by the similarity of both processes with the difference that the controlled conditions chamber allows the defrosting time to be accelerated by controlling the relative humidity and temperature variables.

TABLE-US-00005 TABLE 5 Weight loss of salmon fillets per plant Process with Process Water Microwave chamber controlled with room bath Facility process conditions temperature process Facility 1 0.145% 0.614% 0.427% 1.215% Facility 2 0.156% 0.131% 0.338% 1.363% Facility 3 0.108% 0.372% 0.329% 0.643% Overall total: 0.137% 0.392% 0.367% 1.206%

[0062] The microwave thawing process was applied to salmon fillets with skin (TD) that were frozen by quick freezing in individual packages (IQF), finding that microwave thawing generates weight losses of 0.137%, which are lower than those produced by the process of thawing by water bath that corresponds to 1.206%.

[0063] Some similarity is observed in the result between the chamber thawing treatments with controlled conditions and the thawing treatment at room temperatures for frozen skin-on salmon fillets (referred to in the art as TD). This is explained by the similarity of both processes with the difference that the controlled conditions chamber allows the defrosting time to be accelerated by controlling the relative humidity and temperature variables.

TABLE-US-00006 TABLE 6 Weight loss of salmon fillets with skin (TD VP) per facility Process with Process Water Microwave chamber controlled with room bath Facility process conditions temperature process Facility 1 0.962% 1.509% 1.022% 1.204% Facility 2 0.435% 1.578% 1.665% 1.140% Facility 3 1.199% 1.673% 1.140% 1.280% Overall total: 0.823% 1.581% 1.266% 1.217%

[0064] In the case of skin-on salmon fillets (TD) that were frozen prior to vacuum sealing (VP), they were thawed with microwaves, resulting in lower losses of 0.823%.

[0065] Thawing processes that exceed 37.9 F. (3.3 C.) cannot be carried out due to the growth of anaerobic bacteria, which is regulated by US legislation.

[0066] Comparative analysis of color measurement, according to the SalmoFan scale, of whole salmon and salmon fillets, according to industrial plant:

[0067] The salmon subjected to the four thawing processes and from the three plants of the Applicant, were analyzed with the SalmoFan color scale, which is shown in FIG. 8 as a reference. The result of this comparative analysis is shown in the following table 7:

TABLE-US-00007 TABLE 7 Salmofan scale fillet color measurement Fresh fillet Thawed fillet color color (SalmoFan (SalmoFan Thawing process Facility scale) scale) Microwaves Facility 1 26 26 Facility 2 25 25 Facility 3 25 25 Total microwaves 25 25 Controlled condition Facility 1 26 26 chamber Facility 2 24 24 Facility 3 25 25 Total controlled condition chamber 25 25 Room temperature Facility 1 26 26 Facility 2 24 24 Facility 3 25 25 Total Room temperature 25 25 Water bath Facility 1 26 26 Facility 2 24 24 Facility 3 25 25 Total water bath 25 25

[0068] The results shown in table 7 indicate that the color parameter in each of the thawing processes is maintained.

[0069] Also, it is important to consider that the evaluation of color on the surface of the product was carried out at temperatures above 30.2 F. (1 C.) to observe the maximum expression of color once the water crystals had dissolved.

[0070] Shelf Life Analysis

[0071] To carry out the comparative analysis of the shelf life between the thawing processes of the prior art and the process of the present invention, the results of the mesophilic aerobic count tests of frozen skin-on salmon fillets and frozen salmon fillets will be shown. with skin that were frozen prior to vacuum sealing, in the following tables 8 to 10:

TABLE-US-00008 TABLE 8 Aerobic mesophilic count in Colony Forming Unit per gram of product (CFU/g) in salmon fillets with skin (DT) that were frozen by individual quick freezing (IQF). Fresh Controlled Room Water salmon Microwaves chamber temperature bath Day (UFC/g) (UFC/g) (UFC/g) (UFC/g) (UFC/g) 0 2.540 1.153 30 1.530 2.774 5 1.760 220 93 4.140 8.000 10 33.600 3.173 30.440 18.593 37.930 15 89.267 18.067 66.933 199.000 308.000 17 227.333 62.000 180.533 474.000 405.000 19 508.667 344.667 583.333 869.000 1.252.000 21 1.014.000 719.333 596.667 1.198.667 1.460.000 23 2.668.667 1.408.000 1.713.333 4.450.000 1.920.000

[0072] The results shown in Table 8 and FIG. 9 show that microwave-thawed salmon meat has a low propagation rate of mesophilic aerobes, which is lower than the propagation rate of fresh salmon meat.

TABLE-US-00009 TABLE 9 Aerobic mesophilic count in Colony Forming Unit per gram of product (CFU/g) in salmon fillets with skin (TD) that were thawing prior to vacuum sealing (VP). Fresh Controlled Room Water salmon Microwaves chamber temperature bath Day (UFC/g) (UFC/g) (UFC/g) (UFC/g) (UFC/g) 0 2.540 340 1.780 1.670 678 5 1.760 233 380 4.247 10.970 10 33.600 1.087 11.233 16.280 27.470 15 89.267 8.250 40.533 219.00 336.000 17 227.333 52.533 171.733 674.667 374.000 19 508.667 340.667 476.667 1.094.000 886.000 21 1.014.000 694.000 622.000 1.600.000 1.256.667 23 2.668.667 1.293.500 1.746.667 2.166.667 2.380.000

[0073] The results shown in Table 9 and FIG. 10 show that microwave-thawed salmon meat has a lower propagation rate of mesophilic aerobes than the propagation rate of fresh salmon meat. This means that the shelf life of microwave-thawed salmon is longer than that of fresh salmon.

TABLE-US-00010 TABLE 10 Aerobic mesophilic count in Colony Forming Unit per gram of product (CFU/g) for fresh TE from HON thawed by the technologies. Fresh Controlled Room Water salmon Microwaves chamber temperature bath Day (UFC/g) (UFC/g) (UFC/g) (UFC/g) (UFC/g) 0 2.540 0 0 6.580 400 5 1.760 0 0 3.867 780 10 33.600 9.327 9.973 23.147 12.320 15 89.267 198.667 342.667 373.000 255.000 17 227.333 655.333 699.333 611.000 611.000 19 508.667 1.072.667 1.001.333 944.000 944.000 21 1.014.000 1.323.333 1.540.000 1.580.000 1.580.000 23 2.668.667 2.180.000 2.153.333 2.360.000 2.360.000

[0074] The results shown in Table 10 and FIG. 11 show that microwave-thawed salmon meat has a low propagation rate of mesophilic aerobes, which is lower than the propagation rate of fresh salmon meat.

[0075] Dynamic Shrinkage Analysis

[0076] Within the parameters that allow the effectiveness of the process of the present invention to be compared with the processes of the prior art, is the dynamic reduction that consists of determining the amount of salmon meat that is lost by dripping. This analysis is shown in Table 11 below:

TABLE-US-00011 TABLE 11 Dynamic loss for skin-on (TD) salmon fillets that were frozen by individual quick freezing (IQF) of 4-5 Lb (1.81 to 2.26 kg). Process 24 Hrs. 48 Hrs. 72 Hrs. 96 Hrs. Microwaves 0.825% 1.488% 2.131% 2.316% Controlled chamber 1.177% 1.984% 2.857% 3.043% Room temperature 0.808% 1.946% 2.514% 2.895% Water bath 0.862% 1.966% 2.568% 2.945%

[0077] The results shown in table 11 and in FIG. 12 show that the salmon meat has less loss when thawed with the microwave process of the present invention, compared to the processes of the prior art, due to the fact that it presents less loss by drip (drip-loss).

TABLE-US-00012 TABLE 12 Dynamic loss for salmon fillets with skin (TD) that were frozen prior to vacuum sealing (VP) 4-5 Lb (1.81 to 2.26 kg). Process 24 Hrs. 48 Hrs. 72 Hrs. 96 Hrs. Microwaves 0.862% 1.632% 2.298% 2.494% Controlled chamber 1.259% 2.086% 2.767% 2.966% Room temperature 0.853% 1.982% 2.560% 2.948% Water bath 0.820% 1.903% 2.517% 2.891%

[0078] The results shown in table 12 and in FIG. 13 show that the salmon meat has less loss when thawed with the microwave process of the present invention, compared to the processes of the prior art, due to the fact that it presents less loss by drip-loss.

[0079] The results shown above demonstrate that the process for thawing whole salmon or filleted salmon according to the present invention is superior to prior art thawing processes, since it is a process that is carried out continuously in a short time, between 1.7 to 2.4 minutes and, where the phenotypic properties of raw salmon are maintained and even improved with this process.

[0080] Analysis of the Effect of Microwave Thawing on Nutritional Components Between Fresh Salmon and Thawed Salmon

[0081] In the analysis of the salmon thawing process, it was evaluated whether the nutritional characteristics of fresh salmon are the same or different from salmon that has been stored for a few months and thawed by non-thermal microwave treatment.

[0082] In general, the moisture content of the salmon sample appeared to be inversely related to the total extractable lipid content. This is shown in the following table 13:

TABLE-US-00013 TABLE 13 Total Extractable Lipid Content and Total Moisture of Fresh and Microwave Thawed Salmon Nutrient Fresh Microwave thawed Lipids (%) 15.15 0.49 11.87 1.60 Humidity (%) 63.19 0.86 66.45 1.63

[0083] When applying a one-factor ANOVA, it is concluded: The fresh and microwave-thawed salmon did not show significant differences in the lipid content. Even so, an analysis was carried out on the fatty acids that make up the total fat, obtaining the following results, shown in table 14:

TABLE-US-00014 TABLE 14 Fatty acid content (% total fatty acids) in fresh. microwave-thawed Atlantic Salmon Microwave Fatty acid Fresh thawing Total saturated fatty acids 2.46 0.04 1.82 0.26 Total monounsaturated fatty acids 6.87 0.86 4.91 0.72 C20:5n3 eicosapentaenoic acid (EPA) 0.32 0.03 0.26 0.01 C22:5w3 docosapentanoic acid (DPA) 0.16 0.01 0.13 0.00 C22:6w3 docoahexaenoic acid (DHA) 0.46 0.01 0.36 0.05 Total polyunsaturated fatty acids 4.79 0.19 3.75 0.49 Total fatty acids identified 14.12 0.17 10.48 1.48 Total Omega 3 1.78 0.01 1.4 0.170 Total Omega 6 2.94 0.32 2.36 0.33 n-3/n-6 ratio 0.61 0.59

[0084] According to the results shown in table 14, it can be concluded: [0085] 1. The most abundant fatty acids for fresh fish in the following order: Monounsaturated (49%), Polyunsaturated (34%) and Saturated (17%) [0086] 2. The most abundant fatty acids for microwave-thawed fish in the following order: Monounsaturated (47%), Polyunsaturated (36%) and Saturated (17%). [0087] 3. For fresh and microwave-thawed salmon Monounsaturated fatty acids are present in the highest amounts and oleic acid (C18:1) predominates. [0088] 4. Microwave-thawed fresh salmon did not show significant differences in monounsaturated fatty acid content. [0089] 5. For fresh and microwave-thawed salmon, polyunsaturated fatty acids predominate with 18:2n6c-linoleic acid, cis-linolenic acid as the omega-6 fatty acid, and DHA and EPA as the omega-3. [0090] 6. Fresh and microwave-thawed salmon showed similar levels of polyunsaturated fatty acids. [0091] 7. For fresh and microwave-thawed salmon, saturated fatty acids predominantly palmitic acid (C16:0) and stearic acid (C18:0) [0092] 8. Microwave-thawed fresh salmon did not show significant differences in saturated fatty acid content. [0093] 9. The results show that the content of omega-3 fatty acids (as % total fatty acids) in fresh and microwave-thawed fish was 13%, respectively, these provided the fatty acids DHA, EPA and DPA. [0094] 10. Microwave-thawed fresh salmon showed no significant differences in DHA, EPA and DPA content. [0095] 11. Fresh as well as frozen and microwave-thawed fish is a good source of omega-3 fatty acids. [0096] 12. The types and levels of fatty acids found in fish vary by species, age, size, stage of reproduction, season, geographic location, and diet.

TABLE-US-00015 TABLE 15 Total content of Astaxanthin. Vitamin D and E of fresh and microwave-thawed salmon. Nutrient Fresh Microwave thawing Astaxanthin (mg/Kg) 6.9 0.00 6.85 1.06 Vitamin D3 (/100 g) 8.73 3.92 8.20 2.52 Vitamin E (/100 g) 57.0 0.00 42.55 5.162

[0097] The results for microwave-thawed fresh salmon are within the nutritional values for the Salmo Salar species, according to sources such as the United States Food and Drug Administration (FDA) and the World Food and Agriculture Organization (FAO).

[0098] The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawings will be provided by the office upon request and payment of the necessary fee.