LIQUID NITROGEN QUICK-FREEZING PRESERVATION METHOD FOR FRESH BAMBOO SHOOTS

Abstract

A liquid nitrogen quick-freezing preservation method for fresh bamboo shoots. The method includes performing a coating treatment on cuts of fresh bamboo shoots, which reduces the moisture loss through the cuts, slows down the degree of lignification of the bamboo shoots, mitigates color changes at the cuts, inhibits excessively fast reproduction of microorganisms at the cuts and prevents invasion of microorganisms from the cuts, so that a decrease in nutritional value is reduced, the deterioration of the appearance quality of the bamboo shoots is mitigated, and the nutritional value and commodity value of the bamboo shoots are maintained. The method further includes an intermittent ultrasonic treatment on the fresh bamboo shoots, so that coating substances form films on the surfaces of the cuts more easily, preventing the fresh bamboo shoots from being eroded by microorganisms and preventing nutrient substances from being decomposed and utilized by the microorganisms.

Claims

1. A liquid nitrogen quick-freezing preservation method for fresh bamboo shoots, comprising the following steps: 1) selecting cleaned and drained fresh bamboo shoots without other mechanical damages to bamboo shoot bodies except for cuts, and immersing cut sections of the bamboo shoots in a coating solution; wherein the coating solution contains 10-15% of sodium alginate, 0.3-0.5% of Kappa-Selenocarrageenan, 1.5-2.5% of Leucobryum glaucum extract, 3.2-4.5% of Pyrrhobryum spiniforme extract, and the remaining amount of water; 2) low-temperature microwave treatment: the intermittent ultrasonic treatment refers to treating the bamboo shoots at 0-4° C. and an ultrasonic power of 450-500 W for 5-8 s, taking the bamboo shoots out and allowing standing for 10-15 min, and then treating the bamboo shoots at 550-650 W for 3-5 s; these steps form one cycle, and three cycles are repeated; 3) immersing the whole fresh bamboo shoots in step 2) in a preservative solution; wherein the preservative solution includes the following raw materials in parts by weight: 15-25 parts of water-soluble chitosan, 5-8 parts of serum protein, 1-3 parts of aspartic acid, 1-3 parts of vitamins, 20-40 parts of konjac gluocomannan degradation products, and 100-200 parts of water; 4) putting the fresh bamboo shoots in step 3) into a container, and adding liquid nitrogen; and 5) putting the fresh bamboo shoots in step 4) into a cold storage for storing.

2. The liquid nitrogen quick-freezing preservation method for fresh bamboo shoots of claim 1, wherein the serum protein is bovine serum albumin.

3. The liquid nitrogen quick-freezing preservation method for fresh bamboo shoots of claim 1, wherein the vitamins are vitamin C, vitamin E and beta-carotene mixed at a mass ratio of 1:0.875:0.625.

4. The liquid nitrogen quick-freezing preservation method for fresh bamboo shoots of claim 1, wherein in step 3), 1000 g of fresh bamboo shoots are immersed in 1-3 L of preservative solution.

5. The liquid nitrogen quick-freezing preservation method for fresh bamboo shoots of claim 1, wherein in step 3), the fresh bamboo shoots are immersed in the preservative solution and placed at 0-4° C. and an ultrasonic frequency of 120-150 kHz for 10-20 min.

6. The liquid nitrogen quick-freezing preservation method for fresh bamboo shoots of claim 1, wherein in step 4), the temperature of liquid nitrogen is controlled at −40° C. to −150° C.; and in step 5), the fresh bamboo shoots are stored in the cold storage at −18° C. to −24° C.

7. The liquid nitrogen quick-freezing preservation method for fresh bamboo shoots of claim 1, wherein the fresh bamboo shoots are thawed by immersion at 70° C. for 5 min in an alcoholic solution containing 0.8% (mass concentration) of calcium lactate and 1.5% (mass concentration) of Bazzania trilobata extract.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 shows a process flow chart of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] In order to further describe the technical means adopted by the present invention and the effects of the technical means, the technical solution of the present invention will be further described below in combination with the preferred embodiments of the present invention, but the present invention is not limited to the scope of the embodiments.

[0038] The Bazzania trilobata extract, Leucobryum glaucum extract and Pyrrhobryum spiniforme extract used in the present invention are prepared by the following method: Fresh Bazzania trilobata, Leucobryum glaucum and Pyrrhobryum spiniforme are collected and crushed by a pulverizer under a liquid nitrogen condition, the crushed Bazzania trilobata, Leucobryum glaucum and Pyrrhobryum spiniforme are ethanol-extracted with 95% ethanol and centrifuged, and the resulting supernatant is dried to obtain an extract.

Example 1

[0039] Referring to FIG. 1, this example provides a liquid nitrogen quick-freezing preservation method for fresh bamboo shoots, including the following steps:

[0040] 1) cleaned and drained fresh bamboo shoots without other mechanical damages to bamboo shoot bodies except for cuts were selected, and 1-2 cm above cut sections of the fresh bamboo shoots were immersed in a coating solution; wherein the coating solution contained 10% of sodium alginate, 0.3% of Kappa-Selenocarrageenan, 1.5% of Leucobryum glaucum extract, 3.2% of Pyrrhobryum spiniforme extract, and the remaining amount of water;

[0041] 2) low-temperature microwave treatment: intermittent ultrasonic treatment was performed at 0-4° C.; the intermittent ultrasonic treatment included the following steps: the bamboo shoots were treated at 0-4° C. and an ultrasonic power of 450 W for 5 s, taken out and allowed standing for 10 min, and then treated at 550 W for 3 s; these steps formed one cycle, and three cycles were repeated;

[0042] 3) the whole fresh bamboo shoots in step 2) were immersed in a preservative solution; wherein 1000 g of fresh bamboo shoots were immersed in 1 L of preservative solution, and the preservative solution included the following raw materials in parts by weight: 15 parts of water-soluble chitosan, 5 parts of bovine serum albumin, 1 part of aspartic acid, 1 part of vitamins, 20 parts of konjac gluocomannan degradation products, and 100 parts of water; the vitamins were vitamin C, vitamin E and beta-carotene mixed at a mass ratio of 1:0.875:0.625; the fresh bamboo shoots were immersed in the preservative solution and placed at 0-4° C. and an ultrasonic frequency of 120 kHz for 10 min;

[0043] 4) the fresh bamboo shoots in step 3) were put into a container, and liquid nitrogen was added; and

[0044] 5) the fresh bamboo shoots in step 4) were put into a cold storage at −18˜−20° C. for storing.

[0045] The fresh bamboo shoots were thawed by immersion in an alcoholic solution containing 0.8% (mass concentration) calcium lactate and 1.5% (mass concentration) Bazzania trilobata extract at 70° C. for 5 min.

Example 2

[0046] Referring to FIG. 1, this example provides a liquid nitrogen quick-freezing preservation method for fresh bamboo shoots, including the following steps:

[0047] 1) cleaned and drained fresh bamboo shoots without other mechanical damages to bamboo shoot bodies except for cuts were selected, and 1-2 cm above cut sections of the fresh bamboo shoots were immersed in a coating solution; wherein the coating solution contained 12% of sodium alginate, 0.4% of Kappa-Selenocarrageenan, 1.8% of Leucobryum glaucum extract, 3.8% of Pyrrhobryum spiniforme extract, and the remaining amount of water;

[0048] 2) low-temperature microwave treatment: intermittent ultrasonic treatment was performed at 0-4° C.; the intermittent ultrasonic treatment included the following steps: the bamboo shoots were treated at 0-4° C. and an ultrasonic power of 480 W for 7 s, taken out and allowed standing for 12 min, and then treated at 600 W for 4 s; these steps formed one cycle, and three cycles were repeated;

[0049] 3) the whole fresh bamboo shoots in step 2) were immersed in a preservative solution; wherein 1000 g of fresh bamboo shoots were immersed in 2 L of preservative solution, and the preservative solution included the following raw materials in parts by weight: 20 parts of water-soluble chitosan, 6 parts of bovine serum albumin, 2 parts of aspartic acid, 2 parts of vitamins, 28 parts of konjac gluocomannan degradation products, and 120 parts of water; the vitamins were vitamin C, vitamin E and beta-carotene mixed at a mass ratio of 1:0.875:0.625; the fresh bamboo shoots were immersed in the preservative solution and placed at 0-4° C. and an ultrasonic frequency of 130 kHz for 15 min;

[0050] 4) the fresh bamboo shoots in step 3) were put into a container, and liquid nitrogen was added; and

[0051] 5) the fresh bamboo shoots in step 4) were put into a cold storage at −18˜−20° C. for storing.

[0052] The fresh bamboo shoots were thawed by immersion in an alcoholic solution containing 0.8% (mass concentration) calcium lactate and 1.5% (mass concentration) Bazzania trilobata extract at 70° C. for 5 min.

Example 3

[0053] Referring to FIG. 1, this example provides a liquid nitrogen quick-freezing preservation method for fresh bamboo shoots, including the following steps:

[0054] 1) cleaned and drained fresh bamboo shoots without other mechanical damages to bamboo shoot bodies except for cuts were selected, and 1-2 cm above cut sections of the fresh bamboo shoots were immersed in a coating solution; wherein the coating solution contained 15% of sodium alginate, 0.5% of Kappa-Selenocarrageenan, 2.5% of Leucobryum glaucum extract, 4.5% of Pyrrhobryum spiniforme extract, and the remaining amount of water;

[0055] 2) low-temperature microwave treatment: intermittent ultrasonic treatment was performed at 0-4° C.; the intermittent ultrasonic treatment included the following steps: the bamboo shoots were treated at 0-4° C. and an ultrasonic power of 500 W for 8 s, taken out and allowed standing for 15 min, and then treated at 650 W for 5 s; these steps formed one cycle, and three cycles were repeated;

[0056] 3) the whole fresh bamboo shoots in step 2) were immersed in a preservative solution; wherein 1000 g of fresh bamboo shoots were immersed in 3 L of preservative solution, and the preservative solution included the following raw materials in parts by weight: 25 parts of water-soluble chitosan, 8 parts of bovine serum albumin, 3 parts of aspartic acid, 3 parts of vitamins, 40 parts of konjac gluocomannan degradation products, and 200 parts of water; the vitamins were vitamin C, vitamin E and beta-carotene mixed at a mass ratio of 1:0.875:0.625; the fresh bamboo shoots were immersed in the preservative solution and placed at 0-4° C. and an ultrasonic frequency of 150 kHz for 20 min;

[0057] 4) the fresh bamboo shoots in step 3) were put into a container, and liquid nitrogen was added; and

[0058] 5) the fresh bamboo shoots in step 4) were put into a cold storage at −18˜−24° C. for storing.

[0059] The fresh bamboo shoots were thawed by immersion in an alcoholic solution containing 0.8% (mass concentration) calcium lactate and 1.5% (mass concentration) Bazzania trilobata extract at 70° C. for 5 min.

[0060] Comparative Example 1: the fresh bamboo shoots were harvested, trimmed, frozen in liquid nitrogen directly, and put into a cold storage for storing.

[0061] Comparative Example 2: fresh bamboo shoots were harvested and put into a cold storage for storing directly.

[0062] The fresh bamboo shoots stored in examples 1-3 and comparative examples 1 and 2 were thawed and tested after 7 days, 24 days and 60 days respectively. The results are shown in Table 1.

TABLE-US-00001 TABLE 1 Test Results Enzymatic Activity of Edible Rate/% Protein/% PPO (U/g .Math. min) 7 d 24 d 60 d 7 d 24 d 60 d 7 d 24 d 60 d Example 1 65.12 64.96 63.85 2.81 2.43 2.05 251.52 183.15 143.17 Example 2 64.84 63.74 61.95 2.78 2.38 2.01 252.51 184.07 147.08 Example 3 66.11 65.93 63.29 2.80 2.42 2.02 253.53 185.19 149.96 Comparative 59.75 55.01 49.73 2.51 2.05 1.48 255.05 226.03 206.03 Example 1 Comparative 45.58 40.36 35.17 1.75 1.23 0.92 303.57 289.43 273.33 Example 2

[0063] It will be seen from Table 1 that edible parts of the fresh bamboo shoots preserved by the methods of examples 1-3 remained stable above 60%, edible parts of the fresh bamboo shoots preserved by the methods of comparative examples 1 and 2 started to decline sharply after 7 days, indicating that a high edible rate can be maintained by the preservation method of the present invention;

[0064] No significant decrease was observed in protein contents of the fresh bamboo shoots preserved by the methods of examples 1-3 of the present invention, while the protein contents of the fresh bamboo shoots preserved by the methods of comparative examples 1 and 2 started to decline sharply after 7 days;

[0065] The enzymatic activity of PPO of the fresh bamboo shoots preserved by the methods of examples 1-3 of the present invention was obviously inhibited, indicating that the preservation method of the present invention reduced the browning speed of the fresh bamboo shoots.

[0066] The preservation method of the present invention weakens the metabolic consumption of bamboo shoot somatic cells, reduces the moisture loss through the cuts, slows down the degree of lignification of the bamboo shoots, mitigates color changes at the cuts, inhibits excessively fast reproduction of microorganisms at the cuts and prevents invasion of microorganisms from the cuts, thereby reducing the decrease in nutritional value, reducing the deterioration of appearance quality of the bamboo shoots, and keeping the nutritional value and commodity value of the bamboo shoots to the maximum extent; the preservation method of the present invention improves the thawing speed, increases the rupture strength of the fresh bamboo shoots, reduces the rupture deformation rate of the fresh bamboo shoots, mitigates the sponging, ensures the taste of the fresh bamboo shoots, and reduces the browning of the fresh bamboo shoots.

[0067] Those embodiments described above are only the preferred embodiments of the present invention, the protection scope of the present invention shall not be limited to these embodiments, and all technical solutions under the idea of the present invention shall fall into the protection scope of the present invention. It should be pointed out that some improvements and modifications may be made by those of ordinary skill in the art without departing from the principles of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.