Method for keeping kelp fresh by combining ultrasonic waves with subacid electrolyzed water

Abstract

The invention discloses a method for keeping kelp fresh by combining ultrasonic waves with slightly acidic electrolyzed water, and belongs to the technical field of food fresh keeping. According to the method for preserving the kelp by combining the ultrasonic waves with the slightly acidic electrolyzed water, the kelp is preserved by optimizing parameters of the slightly acidic electrolyzed water and optimizing ultrasonic treatment time and power, and a storage experiment is carried out on the kelp. According to the kelp preserved by the method, the number of microorganisms of the kelp can be reduced to the maximum extent, nutritional ingredients in the kelp can be well reserved, the kelp has good oxidation resistance, the method is simple in process, efficient and environmentally friendly, and processing benefits are greatly improved. The invention not only provides a novel industrial method for fresh keeping of kelp, but also provides theoretical guiding significance for fresh keeping of aquatic products.

Description

Technical Field

[0001] The invention relates to a method for preserving kelp by combined treatment with ultrasonic wave (US) and slightly acidic electrolyzed water (SAEW), belonging to the technical field of food preservation. Background Art

[0002] Kelp, also known as kelp and Jiangbaicai, is an important marine resource with low cost and rich functions. As a kind of seaweed, it mainly contains chemical components such as polysaccharides and amino acids, and has the functions of anticoagulation, anti-tumor, lowering blood sugar and improving the body's immunity. Fresh seaweed has a very high moisture content (about 75-90% by weight) and is very easy to rot due to enzyme deterioration, loss of nutrients and attack by microorganisms. Therefore, how to effectively inhibit the growth and reproduction of microorganisms and extend the shelf life has become a difficult problem faced by the kelp preservation industry.

[0003] The current preservation technologies include physical preservation, chemical preservation and biological preservation. Among them, biological preservation is limited in use due to its high cost, and chemical preservation is controversial due to the introduction of chemical preservatives. Therefore, compared with biological preservation and chemical preservation, physical preservation is more widely used. Physical preservation includes ultra-high voltage, pulsed electric field, microwave, irradiation and ultrasound. Ultrasound is widely used because of its low cost, no need to add additives, safety and environmental protection. Ultrasound (US) is an efficient, promising and sustainable non-thermal sterilization technology used in food processing and preservation. The cavitation effect associated with ultrasound decomposes the cell wall and cell membrane of microorganisms, generates hot spots, forms free radicals, and destroys the DNA of microorganisms. However, the sterilization ability and range of ultrasound alone are limited. In addition, in actual food processing and preservation, ultrasonic treatment will generate large energy consumption due to long-term high-intensity operation, and food quality will also be affected. Therefore, it can be combined with other technologies to produce a synergistic effect to achieve a better preservation effect.

[0004] Slightly acidic electrolyzed water (SAEW) has the characteristics of high efficiency, broad-spectrum sterilization operation, low cost, and environmental protection. It has a positive effect on the sterilization and preservation of aquatic products. It is mainly used as a disinfectant for cleaning food, and has a good preservation effect. It can partially replace common disinfection methods for food storage. SAEW contains hypochlorous acid (HClO), which has a strong and effective bactericidal effect in the pH range of 5.0-6.5. Biomolecules will be potentially oxidized under its action. Studies have shown that slightly acidic electrolyzed water can chlorine oxidize microbial intracellular enzymes and destroy the spatial structure of enzymes, so it can effectively destroy the respiratory metabolism and antioxidant system of microorganisms. SAEW is widely used to improve the quality of fruits and vegetables and to disinfect these products. When using slightly acidic electrolyzed water for sterilization, high concentrations and long-term immersion are required to destroy the cell membrane of microorganisms, and the quality and flavor of the food itself will also be affected. Therefore, using a single slightly acidic electrolyzed water for preservation cannot achieve the ideal effect.

[0005] The combined treatment of ultrasound and slightly acidic electrolyzed water (US+SAEW) can effectively destroy the cell membrane and intracellular substances of microorganisms and enhance the sterilization effect. US+SAEW can not only better exert the sterilization effect, but also reduce the loss of ultrasonic equipment, improve processing efficiency and economic benefits, and ensure food quality. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for preserving kelp by combined treatment of ultrasound and slightly acidic electrolyzed water. The method can significantly improve the storage quality of kelp and extend its shelf life, and it is low-cost, highly efficient and environmentally friendly.

[0007] The objective of the present invention is achieved through the following technical solutions:

[0008] Step 1: Processing of kelp:

[0009] Select fresh kelp with uniform color and cut it into slices (4cm×4cm×2mm).

[0010] Step 2: Screening of slightly acidic electrolyzed water parameters and ultrasonic parameters:

[0011] The kelp treated in step 1 is immersed in slightly acidic electrolyzed water with different effective chlorine concentrations, and is subjected to ultrasonic treatment for a certain period of time.

[0012] Step 3: Storage experiment on kelp

[0013] The kelp processed in step 2 is placed in a polyethylene bag and stored at room temperature of 25°C.

[0014] Preferably, in step 2, the effective chlorine concentration of the slightly acidic electrolyzed water is 40-80 mg / L, and the pH is 6.28-6.41.

[0015] Preferably, the mass of the slightly acidic electrolyzed water in step 2 is 2 to 6 times the mass of the kelp.

[0016] Preferably, the ultrasonic power in step 2 is 200-400W.

[0017] Preferably, the ultrasonic time in step 2 is 3 to 10 minutes.

[0018] The present invention utilizes ultrasound combined with slightly acidic electrolyzed water to preserve kelp, utilizes the sterilization effect of ions in slightly acidic electrolyzed water and the cavitation effect of ultrasound, so that the kelp processed by the method has high nutritional content and good antioxidant capacity. The method is green and environmentally friendly, has a simple process, is an environmentally friendly and efficient method for preserving kelp, and has high application value.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) Simple, efficient, environmentally friendly and processing-efficient:

[0021] The present invention adopts ultrasound combined with slightly acidic electrolyzed water. Ultrasound is an efficient and sustainable sterilization technology. Slightly acidic electrolyzed water has the characteristics of high efficiency, broad-spectrum sterilization operation, low cost, and environmental protection. The combination of the two has high environmental protection and can better improve processing efficiency.

[0022] (2) Has antioxidant and kelp nutrient retention effects:

[0023] The invention processes kelp by combining ultrasound with slightly acidic electrolyzed water, thereby prolonging the shelf life of the kelp, maintaining its moisture, total sugar content and total content, and effectively reducing the growth of microorganisms. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Summary Figure;

[0025] Figure 2 Storage stability of kelp under the conditions of Example 2;

[0026] Figure 3 The nutritional components of kelp under the conditions of Example 2;

[0027] Figure 4 Antioxidant properties of kelp under the conditions of Example 2. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and beneficial effects of the present invention more clear, the present invention is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings, but the protection scope of the present invention is not limited thereto;

[0029] Embodiment 1:

[0030] Step 1: Processing of kelp:

[0031] Select fresh kelp with uniform color and cut it into slices (4cm×4cm×2mm).

[0032] Step 2: Screening of slightly acidic electrolyzed water parameters and ultrasonic parameters:

[0033] The kelp treated in step 1 is soaked in slightly acidic electrolyzed water and assisted with ultrasonic treatment, wherein the slightly acidic electrolyzed water has an effective chlorine concentration of 40 mg / L, a pH of 6.28, a mass twice that of the kelp, an ultrasonic power of 200 W, and an ultrasonic time of 3 min.

[0034] Step 3: Storage experiment on kelp:

[0035] The kelp processed in step 2 is placed in a polyethylene bag and stored at room temperature of 25°C.

[0036] Embodiment 2:

[0037] Step 1: Processing of kelp:

[0038] Select fresh kelp with uniform color and cut it into slices (4cm×4cm×2mm).

[0039] Step 2: Screening of slightly acidic electrolyzed water parameters and ultrasonic parameters:

[0040] The kelp treated in step 1 is soaked in slightly acidic electrolyzed water and assisted with ultrasonic treatment, wherein the slightly acidic electrolyzed water has an effective chlorine concentration of 60 mg / L, a pH of 6.37, a mass of 4 times that of the kelp, an ultrasonic power of 300 W, and an ultrasonic time of 5 min.

[0041] Step 3: Storage experiment on kelp:

[0042] The kelp processed in step 2 is placed in a polyethylene bag and stored at room temperature of 25°C.

[0043] Embodiment 3:

[0044] Step 1: Processing of kelp:

[0045] Select fresh kelp with uniform color and cut it into slices (4cm×4cm×2mm).

[0046] Step 2: Screening of slightly acidic electrolyzed water parameters and ultrasonic parameters:

[0047] The kelp treated in step 1 is soaked in slightly acidic electrolyzed water and assisted with ultrasonic treatment, wherein the slightly acidic electrolyzed water has an effective chlorine concentration of 80 mg / L, a pH of 6.41, a mass of 6 times that of the kelp, an ultrasonic power of 400 W, and an ultrasonic time of 10 min.

[0048] Step 3: Storage experiment on kelp:

[0049] The kelp processed in step 2 is placed in a polyethylene bag and stored at room temperature of 25°C.

[0050] Example 2: Experimental test on storage of kelp preserved by ultrasound combined with slightly acidic electrolyzed water;

[0051] (1) Determination of storage stability:

[0052] Total colony count: Homogenize the kelp in 45 mL of sterile saline for 60 seconds and then let it stand. Dilute the supernatant 10 times and inoculate it into 0.1 mL of sterile saline. Inoculate 0.1 mL of the dilution onto plate count agar. Then incubate the plate at 37°C for 48 hours and count.

[0053] Water activity: Use a water activity meter to measure the water activity of kelp. Spread the processed kelp sample on the scale of the water activity sample plate, making sure there are no gaps. Place the sample plate in the water activity meter and read the reading.

[0054] (2) Analysis of storage stability results:

[0055] like Figure 2 As shown in the figure, the total colony count results showed that with the extension of storage time, the total colony count of kelp showed an increasing trend (P<0.05). The total colony count of kelp without any treatment reached the end of the shelf life on the 5th day (4.47log 10 CFU / g), while the kelp treated with US+SAEW reached the end of its shelf life on the 15th day. The water activity results showed that the water activity of kelp gradually decreased with the extension of storage time (P<0.05). When the storage time was 5 days, the water activity of kelp without any treatment was 0.9377, while the water activity of kelp in the US+SAEW treatment group was 0.9267, which was lower than that of the control group.

[0056] (3) Determination of nutritional components:

[0057] Moisture content: Take 2g~10g of kelp, wipe the surface moisture with sterile filter paper, and chop it. After weighing the aluminum box, put the chopped kelp into it and place it in a drying oven at 101℃~105℃. After drying for 2h~4h, take it out and put it in a dryer to cool for 0.5h before weighing. Then put it in a drying oven at 101℃~105℃ again, dry for about 1h, take it out, put it in a dryer to cool for 0.5h before weighing again. Repeat the above steps until the difference in mass before and after does not exceed 2mg, which is constant weight.

[0058]

[0059] Wherein, W1: mass before drying (g); W0: mass after drying (g).

[0060] Total sugar content: The total sugar content was determined by the phenol-sulfuric acid method. Accurately measure 0.5 mL of the kelp sample solution diluted to an appropriate concentration, add 0.5 mL of 6% phenol solution, then add 2.5 mL of concentrated sulfuric acid and mix quickly. After standing for 30 minutes, measure the absorbance at 490 nm to determine the total sugar content.

[0061] (4) Analysis of nutritional components:

[0062] like Figure 3 As shown in the data, with the extension of storage time, the total sugar content and moisture content of kelp decreased significantly (P<0.05), and US+SAEW treatment delayed the decrease of total sugar and moisture content of kelp. On the 15th day of storage, the total sugar content and moisture content of kelp in the US+SAEW treatment group increased by 12.34% and 5.83% compared with the untreated group.

[0063] (4) Antioxidant performance test:

[0064] Total phenol content: Accurately weigh 0.1g of gallic acid, dissolve it in 50ml of distilled water, and dilute to 100ml. Obtain a gallic acid standard stock solution with a mass concentration of 1000mg / L. Take 0, 2.5, 5, 10, and 20mL of the standard stock solution in a 100mL volumetric flask, dilute to the scale with distilled water, and prepare a series of standard solutions with mass concentrations of 0, 25, 50, 100, and 200mg / L (μg / ml). Take 100μL of each and add 750μL of 0.2N Folin phenol. After 5min, add 750μL of 6% (w / v) 6g / 100ml NaHCO3. After reacting in the dark for 1h, measure the absorbance at 725nm. Take 100 μL of sample extract, add 750 μL of 0.2N Folin, and after 5 minutes, add 750 μL of 6% (w / v) NaHCO3. After reacting in the dark for 1 hour, measure the absorbance at 725 nm.

[0065] M=X×V / M

[0066] Where: M——total phenol content in the sample, mgGAE / g; X——sample concentration calculated according to the standard curve, mg / mL; V——volume of sample extract after dilution, mL; W——dry weight of raw material.

[0067] ABTS free radical scavenging rate: After freeze drying the kelp sample in a freeze dryer, grind it into powder, pass through a 60-mesh sieve and store it in a sealed container at -18°C. Take 2.0 g of freeze-dried kelp sample in a 50 mL stoppered centrifuge tube, dissolve it in 20 mL of 60% ethanol aqueous solution, and rotate the sample at 210 rpm for 24 h at room temperature at 2100 × g for 10 minutes, collect the supernatant, and extract the precipitate twice under the same conditions. Combine the two supernatants, remove the ethanol solution by rotary evaporation, make the volume to 50 mL, and store it at -20°C.

[0068] Prepare mother solution: dilute 0.0384g ABTS powder to 10mL, dilute 0.0134g potassium persulfate to 10mL, mix in a volume ratio of 1:1, and react for 12-16 hours in the dark. Prepare working solution: dilute 50 times with methanol (water) until OD 734 =0.7±0.02.

[0069] Take 3.9mL ABTS+, add 0.1mL sample solution, shake for 30s, let stand for 5min in the dark, and measure the absorbance at 734nm (A1). Control: 0.1mL methanol mixed with 3.9mL ABTS+ free radical solution at 734nm (A0).

[0070]

[0071] (6) Analysis of antioxidant performance results:

[0072] like Figure 4As shown in Figure 2, the antioxidant properties showed that the ABTS radical scavenging activity of all kelps continued to decrease throughout the storage period. On day 0, there was no significant difference in the ABTS radical scavenging rate among the groups (P>0.05). However, with the extension of storage time, the ABTS radical scavenging effect of the kelp samples treated with US+SAEW was the most significant (P<0.05). In addition, the ABTS radical scavenging rate of the kelp with a storage time of 15 days was 1.65% higher than that of the control group. The maintenance of antioxidant capacity in kelp may be attributed to the improvement of bioactive components, among which total phenols play a vital role in enhancing antioxidant activity. The total phenol content was positively correlated with the ABTS scavenging rate, indicating that the higher the total phenol content, the higher the ABTS scavenging rate and the overall antioxidant capacity. The total phenol content of each group generally decreased over time. Although the total phenol content gradually decreased with the extension of storage time, the total phenol content of kelp treated with US+SAEW was always higher compared with the control group (P<0.05), increasing by 13% compared with the control group. This suggests that US+SAEW treatment can improve the preservation of bioactive components in Laminaria japonica during storage.

[0073] In summary, the present invention has discovered a method for preserving kelp by combining ultrasound with slightly acidic electrolyzed water, which is an environmentally friendly and efficient method. Kelp preserved by combining ultrasound with slightly acidic electrolyzed water can maintain a high nutritional content, have good storage stability and antioxidant capacity, thereby achieving a higher value for the kelp.

[0074] Note: The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention; therefore, although this specification has described the present invention in detail with reference to the above embodiments, a person skilled in the art should understand that the present invention can still be modified or replaced by equivalents; and all technical solutions and improvements thereof that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for preserving kelp by using ultrasound combined with slightly acidic electrolyzed water, characterized in that: The following steps are involved: Step 1: Processing of kelp: Select fresh kelp with uniform color and cut it into slices (4cm×4cm×2mm); Step 2: Screening of slightly acidic electrolyzed water parameters and ultrasonic parameters: The kelp treated in step 1 is immersed in a certain amount of slightly acidic electrolyzed water with different effective chlorine concentrations and different pH values, and is subjected to ultrasonic treatment for a certain time and power; Step 3: Storage experiment on kelp The kelp processed in step 2 was placed in a polyethylene bag and stored at a room temperature of 25°C to explore the effects of the combined treatment and storage time on the quality of the kelp.

2. The method for preserving kelp by using ultrasound combined with slightly acidic electrolyzed water according to claim 1, characterized in that: Step 2: The effective chlorine concentration of slightly acidic electrolyzed water is 60 mg / L.

3. The method for preserving kelp by using ultrasound combined with slightly acidic electrolyzed water according to claim 1, characterized in that: Step 2: The pH of slightly acidic electrolyzed water is 6.

37.

4. The method for preserving kelp by using ultrasound combined with slightly acidic electrolyzed water according to claim 1, characterized in that: Step 2: The mass ratio of kelp to slightly acidic electrolyzed water is 1:

4.

5. The method for preserving kelp by using ultrasound combined with slightly acidic electrolyzed water according to claim 1, characterized in that: The ultrasonic treatment time in step 2 is 5 min.

6. The method for preserving kelp by using ultrasound combined with slightly acidic electrolyzed water according to claim 1, characterized in that: The ultrasonic treatment power in step 2 is 300W.

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