AU2020103824A4 - Low-Salt Pickle Preservation Method by High-Voltage Electric Field Cold Plasma-Based Sterilization - Google Patents
Low-Salt Pickle Preservation Method by High-Voltage Electric Field Cold Plasma-Based Sterilization Download PDFInfo
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- 235000021110 pickles Nutrition 0.000 title claims abstract description 110
- 230000001954 sterilising effect Effects 0.000 title claims abstract description 92
- 238000004659 sterilization and disinfection Methods 0.000 title claims abstract description 88
- 230000005684 electric field Effects 0.000 title claims abstract description 71
- 238000000034 method Methods 0.000 title claims abstract description 36
- 238000004321 preservation Methods 0.000 title claims abstract description 20
- 230000005495 cold plasma Effects 0.000 claims abstract description 40
- 238000004806 packaging method and process Methods 0.000 claims abstract description 36
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims abstract description 35
- 238000000855 fermentation Methods 0.000 claims abstract description 33
- 230000004151 fermentation Effects 0.000 claims abstract description 31
- 239000011780 sodium chloride Substances 0.000 claims abstract description 17
- 238000005554 pickling Methods 0.000 claims abstract description 12
- 230000009471 action Effects 0.000 claims abstract description 6
- 235000006140 Raphanus sativus var sativus Nutrition 0.000 claims description 31
- 235000010149 Brassica rapa subsp chinensis Nutrition 0.000 claims description 15
- 235000000536 Brassica rapa subsp pekinensis Nutrition 0.000 claims description 15
- 241000499436 Brassica rapa subsp. pekinensis Species 0.000 claims description 15
- 239000002994 raw material Substances 0.000 claims description 7
- 238000012545 processing Methods 0.000 claims description 6
- 239000012267 brine Substances 0.000 claims description 5
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 claims description 5
- 244000088415 Raphanus sativus Species 0.000 claims 2
- 240000007124 Brassica oleracea Species 0.000 claims 1
- 235000003899 Brassica oleracea var acephala Nutrition 0.000 claims 1
- 235000011301 Brassica oleracea var capitata Nutrition 0.000 claims 1
- 235000001169 Brassica oleracea var oleracea Nutrition 0.000 claims 1
- 244000000626 Daucus carota Species 0.000 claims 1
- 235000002767 Daucus carota Nutrition 0.000 claims 1
- 241000233866 Fungi Species 0.000 abstract description 23
- 230000000694 effects Effects 0.000 abstract description 20
- 238000004519 manufacturing process Methods 0.000 abstract description 5
- 235000013305 food Nutrition 0.000 abstract description 4
- 239000000796 flavoring agent Substances 0.000 abstract description 3
- 235000019634 flavors Nutrition 0.000 abstract description 3
- 206010040030 Sensory loss Diseases 0.000 abstract description 2
- 241000894006 Bacteria Species 0.000 description 30
- 241000220259 Raphanus Species 0.000 description 29
- 238000003860 storage Methods 0.000 description 18
- 244000005700 microbiome Species 0.000 description 17
- 238000009928 pasteurization Methods 0.000 description 12
- 230000001681 protective effect Effects 0.000 description 12
- 239000007788 liquid Substances 0.000 description 7
- 238000009448 modified atmosphere packaging Methods 0.000 description 7
- 235000013311 vegetables Nutrition 0.000 description 7
- 230000006866 deterioration Effects 0.000 description 6
- 238000009832 plasma treatment Methods 0.000 description 6
- 230000001953 sensory effect Effects 0.000 description 6
- 230000006378 damage Effects 0.000 description 4
- 239000003651 drinking water Substances 0.000 description 4
- 235000020188 drinking water Nutrition 0.000 description 4
- 230000000844 anti-bacterial effect Effects 0.000 description 3
- 238000012136 culture method Methods 0.000 description 3
- 235000021121 fermented vegetables Nutrition 0.000 description 3
- 238000012856 packing Methods 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- 241001148470 aerobic bacillus Species 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 239000005452 food preservative Substances 0.000 description 2
- 235000019249 food preservative Nutrition 0.000 description 2
- 230000036541 health Effects 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 description 2
- 235000013372 meat Nutrition 0.000 description 2
- 239000002086 nanomaterial Substances 0.000 description 2
- 235000016709 nutrition Nutrition 0.000 description 2
- 230000001699 photocatalysis Effects 0.000 description 2
- 238000007146 photocatalysis Methods 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 230000002195 synergetic effect Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000001066 destructive effect Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 206010016766 flatulence Diseases 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 235000014655 lactic acid Nutrition 0.000 description 1
- 239000004310 lactic acid Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 235000015097 nutrients Nutrition 0.000 description 1
- 230000035764 nutrition Effects 0.000 description 1
- 239000005022 packaging material Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- -1 salt ions Chemical class 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 230000004936 stimulating effect Effects 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 238000007669 thermal treatment Methods 0.000 description 1
Classifications
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- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
- A23B7/00—Preservation or chemical ripening of fruit or vegetables
- A23B7/015—Preserving by irradiation or electric treatment without heating effect
-
- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23V—INDEXING SCHEME RELATING TO FOODS, FOODSTUFFS OR NON-ALCOHOLIC BEVERAGES AND LACTIC OR PROPIONIC ACID BACTERIA USED IN FOODSTUFFS OR FOOD PREPARATION
- A23V2002/00—Food compositions, function of food ingredients or processes for food or foodstuffs
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A40/00—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production
- Y02A40/90—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production in food processing or handling, e.g. food conservation
Abstract
The present invention relates to a low-salt pickle preservation method by high-voltage
electric field cold plasma-based sterilization, which pertains to the field of food sterilization
and preservation. The technical solution of the method is as follows: putting pickled and
fermented low-salt pickles in a packaging bag (box), adjusting a NaCl concentration of a
pickling fermentation broth to 2.5-4.0% and a total acidity thereof to 0.4-0.6%, adding the
pickling fermentation broth to the packaging bag (box) at a ratio of pickles to pickling
fermentation broth being 1:1 (w/v), and air-filled packaging; and placing the packaging bag
(box) between two electrodes of a high-voltage electric field cold plasma-based sterilization
device under conditions of 50-70% RH and 15-20°C, and sterilizing the packaging bag
(box) by a repeated short-duration sterilization method in which sterilization is repeated 2-5
times at intervals of 20-60 s with a voltage intensity of 55-65 kV/cm, a frequency of 70-120
Hz, a current of 0.3-0.8 mA, and a single electric field action duration of 20-60 s. By
adopting the repeated short-duration cold plasma-based sterilization method for low-salt
pickles, the method has the effects of killing flatulent fungi while ensuring low sensory loss
of the pickles, significantly improves the sterilization effect and shelf life, and can meet the
requirements of large-scale automatic production of the pickles with unique flavors.
FIG. 1
1/1
Description
FIG. 1
1/1
Technical Field
The present invention specifically relates to a low-salt pickle preservation method by high-voltage electric field cold plasma-based sterilization, which pertains to the technical field of food sterilization and preservation.
Related Art
Low-salt pickle refers to a type of traditional fermented vegetable product formed by anaerobic fermentation of lactic acid bacteria on the surface of vegetables by pickling vegetables containing about 6-8% sodium chloride salt solution in a pickle jar at room temperature. The pickling fermentation process of pickle is "cold processing", which not only maintains the nutrients of the vegetables, but also produces unique flavors through anaerobic fermentation, which is widely loved by consumers. In order to avoid the destruction of the texture characteristics of vegetables, the vegetable raw materials will not be thermally sterilized before the production of pickles. Therefore, various microorganisms are brought into the fermentation system by vegetables, which increases the uncontrollable risk of product quality. In order to ensure the safety and quality of products, food preservatives or thermal sterilization are used to inhibit or kill the microorganisms in commodities in order to achieve the purpose of product preservation. However, although the above two methods can effectively inhibit or kill the microorganisms in the products, they still have the following effects on the products: 1) thermal sterilization: affecting the taste, crispness and color of the products; 2) adding food preservatives: affecting the nutrition and health characteristics of the products. Therefore, how to carry out cold sterilization on pickles without destroying the sensory, nutritional and health characteristics of fermented vegetables is the key to improve the quality of pickles.
High-voltage electric field cold plasma-based sterilization is a novel cold sterilization technology for food, which has the advantages of low energy consumption, no secondary pollution and less sensory quality loss of heat sensitive raw materials. The high-voltage electric field cold plasma-based sterilization achieves the sterilization effect mainly by stimulating the medium gas around the food to produce photoelectrons, ions, active free radicals, etc., which cause the destruction of microorganism cells. At present, the research of high-voltage electric field cold plasma-based sterilization method has made certain progress. Patent Application No. ZL201410347682.3 discloses a high-voltage field plasma and nano photocatalysis synergistic sterilizing and preserving method for fresh meat. The method is to make a modified coating solution of nanomaterials and dry it into antibacterial packaging materials to carry out the modified atmosphere packaging (MAP) on the fresh meat and then perform continuous cold sterilization treatment. Patent Application No. ZL.201510182548.7 discloses a method of cold sterilization in package under the synergistic effect of plasma and nanometer material photocatalysis, which is to mix microorganisms with nanomaterials and then put them into plasma device for sterilization treatment. Since low-salt pickles are fermented products, and contain more initial microorganisms than fresh products, the above methods are not suitable for sterilization of low-salt pickles. Therefore, it is an urgent technical bottleneck to develop an efficient, green, low-carbon and low-sensory-loss sterilization method for packaged pickles.
The salt concentration of low-salt pickles is usually between 2.5% and 4.0%. Because salt ions can promote the ionization in the system, the photoelectrons, ions, free radicals and other particles generated by high-voltage electric field plasma under this salt concentration can enhance the sterilization effect, thus shortening the sterilization time and reducing the deterioration of the sensory quality of the products in the sterilization process. Therefore, high voltage electric field plasma has the advantages of short sterilization time and low sensory deterioration when applied to low-salt pickles. At present, there is no preservation method by high-voltage electric field cold plasma-based sterilization for low-salt pickles.
An objective of the present invention is to provide a low-salt pickle preservation method by high-voltage electric field cold plasma-based sterilization for the above technical problems, and to provide a safe, efficient and easy-to-operate sterilization method for fermented vegetable products that can effectively extend the shelf life of low-salt pickle products. It is convenient for industrialized production of pickle with good flavor and taste.
The above objective of the present invention is achieved by the low-salt pickle preservation method by high-voltage electric field cold plasma-based sterilization, characterized in that: the method includes the following steps:
(1) Preparation of liquid packaging contents of the products: adjusting the total acidity, NaCl concentration, and total number of colonies of the pickling fermentation broth with drinking water;
(2) Fermentation of pickle raw materials: controlling the NaCl concentration of the fermentation brine of the pickles at 6.0-8.0%, and controlling the packaged pickles by fermentation to have certain total acidity, NaCl concentration and total number of colonies;
(3) Packaging: packing the products in step (2) with MAP or adding the liquid packaging contents of the products in step (1) at a ratio of 1:1 (w/v) for packaging; and
(4) Sterilization treatment: placing the packaged pickles in step (3) between two electrodes of a plasma generator, and carrying out plasma-based sterilization treatment under high-voltage electric field conditions.
Under optimal conditions, the liquid packaging contents of the products in step (1) are prepared by adding drinking water to the low-salt pickling fermentation broth, and adjusting the NaCl concentration to 2.5-4.0% and the total acidity to 0.4-0.6%.
Under optimal conditions, the fermentation temperature in step (2) is controlled at 25-30°C, the fermentation time is 3-7 days, and the fermentation is complete until the NaCl concentration of the pickles is 2.5-4.0%, the total acidity is 0.4-0.6%, and the total number of colonies is 104-106 CFU/mL.
Under optimal conditions, the pickles in step (2) is prepared by fermenting one or any combination of Chinese cabbage, summer radish, and roseheart radish by low-salt fermentation.
Under optimal conditions, step (3) adopts MAP packaging, and the atmosphere condition of MAP packaging is 02/CO2/He/N2= 30±5/30±5/10±5/30±5%.
Under optimal conditions, the plasma generator in step (4) includes a voltage regulator, a high-voltage electric field generator, an upper electrode, a lower electrode and an insulating protective plate. The pickles packaged by MAP are placed between the upper and lower electrodes. An upper insulating protective plate is arranged between the upper surface of the packaging box and the upper electrode, and a lower insulating protective plate is arranged between the lower surface of the packaging box and the lower electrode.
Under optimal conditions, in step (4), the packaging bag (box) is placed between the two electrodes of the high-voltage electric field cold plasma-based sterilization device at 15-20°C and a relative humidity of 50-70% RH, and sterilized by a repeated short-duration sterilization method in which sterilization is repeated for 2-5 times at intervals of 30-60 s with a processing voltage intensity of 55-65 kV/cm, a frequency of 70-120 Hz, a current of 0.3-0.8 mA, and a single electric field action time of 30-60 s.
The beneficial effects of the present invention are:
(1) The present invention utilizes the sterilization effect of high-voltage electric field plasma on spoilage bacteria in low-salt pickles, to effectively control the quantity of spoilage bacteria in the pickle products, thereby prolonging the shelf life of the products. The production method is simple and suitable for industrialized production, avoids the loss of the sensory quality of the products, and improves the storage stability of the products. The products are convenient to eat, and have broad market prospect.
Figure 1 shows the flatulence of radish pickles after 7 days of storage after being treated by high-voltage electric field plasma-based sterilization (right) and without being treated (left).
The present invention is described in detail with reference to the accompanying drawing and embodiments. The present invention can be better understood through the following embodiments.
Example 1 Low-salt summer radish pickle preservation method based on high-voltage electric field cold plasma-based sterilization
(1) Preparation of liquid packaging contents of the products: adjusting the total acidity of the pickling fermentation broth to 0.4% and the NaCl concentration thereof to 2.5% with drinking water;
(2) Fermentation of pickle raw materials: controlling the NaCl concentration of the fermentation brine of the pickles at 4%, controlling the fermentation temperature at 25°C, and fermenting for 3 days, where the fermentation is complete until the NaCl concentration of the pickles was 2.5%, the total acidity was 0.4%, and the total number of colonies was 104 CFU/ml;
(3) Packaging: adding the products in step (2) to the liquid packaging contents of the products in step (1) at a ratio of 1:1 (w/v) for packaging; and
(4) Sterilization treatment: A plasma generator including a voltage regulator, a high-voltage electric field generator, an upper electrode, a lower electrode, and an insulating protective plate was used. The packaged pickles were placed between the upper and lower electrodes. An upper insulating protective plate was arranged between the upper surface of the packaging box and the upper electrode. A lower insulating protective plate was arranged between the lower surface of the packing box and the lower electrode. The packaged pickles in step (3) underwent high-voltage electric field plasma-based sterilization under the conditions of 15°C and 50% RH, where the packaging bag (box) was placed between the two electrodes of the high-voltage electric field cold plasma-based sterilization device, and sterilized by a repeated short-duration sterilization method in which sterilization is repeated for 2 times at intervals of 45 s with a processing voltage intensity of 55 kV/cm, a frequency of 70, 80, 90, and 100 Hz, a current of 0.3 mA, and a single electric field action time of 45 s.
Summer radish pickles without plasma treatment under the same conditions were used as a control group, and were compared with pasteurized pickles. The summer radish pickles were stored at 30°C for 7 days. After plasma treatment (0 d) and storage for 7 days (7 d), the total number of colonies of summer radish pickles was measured according to GB 4789.2-2016, the total number of fungi in summer radish pickles was measured according to GB 4789.15-2016, and the number of coliform bacteria in summer radish pickles was measured according to GB 4789.3-2016. The quantity of aerogenic bacteria in summer radish pickles was measured by a picking culture method, and the hardness of summer radish pickles was measured by a texture analyzer.
The total numbers of colonies, fungi, and aerogenic bacteria and the hardness of summer radish pickles after sterilization were recorded as shown in Table 1 and Table 2.
Table 1. Changes in the number of microorganisms (Log (CFU/g)) during storage of low-salt summer radish pickles that have not been treated, have been pasteurized, and have been treated by high-voltage electric field cold plasma-based sterilization
Types of Time Control High-voltage electric field cold plasma Pasteurization microorganisms (d) group 70 Hz 80 Hz 90 Hz 100 Hz Total number of 0 6.00±0.22a ND 5.28±0.09b 4.88±0.05c 4.56±0.09d 4.03±0.13e colonies Fungus 0 5.50±0.08a ND 4.89±0.05b 4.56±0.04c 4.20±0.23d 3.83±0.05e Aerobic 0 5.50±0.08a ND 4.89±0.05b 4.56±0.04c 4.20±0.23d 3.83±0.05e bacteria Coliform 0 ND ND ND ND ND ND Total number of 7 7.12±0.06a ND 5.45±0.04b 4.95±0.04c 4.60±0.01d 4.12±0.08e colonies Fungus 7 6.72±0.10 ND ND ND ND ND Aerobic 7 6.72±0.10 ND ND ND ND ND bacteria Coliform 7 ND ND ND ND ND ND
Note: Different letters in the same row indicate significant differences between treatment groups, i.e. P<0.05; ND: not detected
Table 2. Changes in hardness (kg) during fresh-keeping storage of low-salt summer radish pickles that have not been treated, have been pasteurized, and have been treated by high-voltage electric field cold plasma-based sterilization
Time (d) Control group Pasteurization High-voltage electric field cold plasma 70Hz 80Hz 90Hz 100Hz 0 15.00±0.27cd 12.76±0.12a 14.23±0.75bc 15.98±0.59d 15.42±0.88d 13.43±0.24ab 2 10.57±0.55a 10.29±0.21a 11.78±0.67bc 12.16±0.02c 12.08±0.73c 10.84±0.95ab 7 9.43±0.67a 9.01±0.54a 11.19±0.81b 12.84±0.52c 11.76±0.13b 10.02±0.65a
Note: Different letters in the same row indicate significant differences between treatment groups, i.e. P<0.05
It can be seen from the above tables that colonies, aerogenic bacteria and fungi in the control group proliferated rapidly during storage, which were rotten after 7 days of storage. Pasteurization can kill almost all microorganisms in the pickles. The sterilization effect of high-voltage electric field plasma on low-salt summer radish pickles increased with the increase of frequency. The main bactericidal effect of high-voltage electric field plasma on fungi and flatulent bacteria was mainly post-treatment effect. After treatment (0 d), fungi and flatulent bacteria still existed, but were significantly less than those of the control group. After 7 days of storage, the fungi and flatulent bacteria were basically killed, indicating that the high-voltage electric field plasma had a very significant bactericidal effect on fungi and flatulent bacteria. High-voltage electric field plasma can also reduce the total number of colonies. After sterilization (0 d) and storage (7 d), the total number of colonies in the high-voltage electric field plasma group was significantly lower than that of the control group, indicating that high-voltage electric field plasma had better sterilization and preservation effects.
In terms of texture, the pickles in the control group softened rapidly due to the spoilage of microorganisms, and the thermal treatment of pasteurization also caused significant damage to the texture of vegetables. The high-voltage electric field plasma can significantly inhibit the texture deterioration of the pickles during storage. When the frequency was lower than 80 Hz, the texture protection effect of the high-voltage electric field plasma increased with the frequency, but when the frequency further increased, the texture protection effect gradually weakened. Comprehensive comparison of the sterilization effect and texture protection effect indicated that the high-voltage electric field cold plasma-based sterilization had a better sterilization effect than the traditional pasteurization.
Example 2 Low-salt roseheart radish pickle preservation method based on high-voltage electric field cold plasma-based sterilization
(1) Fermentation of pickle raw materials: controlling the NaCl concentration of the fermentation brine of the pickles at 6%, controlling the fermentation temperature at 30°C, and fermenting for 3 days in step (1), fermenting until the NaCl concentration of the pickles was 3.0%, the total acidity was 0.6%, and the total number of colonies was 105 CFU/mL;
(2) Packaging: packaging the products in step (1) by MAP, where the atmosphere condition of MAP was 0 2 /CO 2 /HE/N 2 = 30±5/30±5/10±5/30±5%; and
(3) Sterilization treatment: A plasma generator including a voltage regulator, a high-voltage electric field generator, an upper electrode, a lower electrode and an insulating protective plate was used. The MAP-packaged pickles were placed between the upper and lower electrodes. An upper insulating protective plate was arranged between the upper surface of the packaging box and the upper electrode, and a lower insulating protective plate was arranged between the lower surface of the package box and the lower electrode. The packaged pickles in step (2) underwent high-voltage electric field cold plasma-based sterilization under the conditions of 15°C and 60% RH, where the packaging bag (box) was placed between the two electrodes of the high-voltage electric field cold plasma-based sterilization device, and sterilized by a repeated short-duration sterilization method in which sterilization is repeated for 4 times at intervals of 30 s with a processing voltage intensity of 60 kV/cm, a frequency of 80, 90, 100, and 110 Hz, a current of 0.5 mA, and a single electric field action time of 30 s.
Roseheart radish pickles without plasma treatment under the same conditions were used as a control group, and were compared with pasteurized pickles. The roseheart radish pickles were stored at 30°C for 7 days. After plasma treatment (0 d) and storage for 7 days
(7 d), the total number of colonies of roseheart radish pickles was measured according to GB 4789.2-2016, the number of coliform bacteria in roseheart radish pickles was measured according to GB 4789.3-2016, and the total number of fungi in roseheart radish pickles was measured according to GB 4789.15-2016. The quantity of flatulent bacteria in roseheart radish pickles was measured by a picking culture method, and the hardness of roseheart radish pickles was measured by a texture analyzer.
The total numbers of colonies, fungi, and flatulent bacteria and the hardness of roseheart radish pickles after sterilization were recorded as shown in Table 3 and Table 4.
Table 3. Changes in the number of microorganisms (Log (CFU/g)) during storage of low-salt roseheart radish pickles that have not been treated, have been pasteurized, and have been treated by high-voltage electric field cold plasma-based sterilization
Types of Time Control High-voltage electric field cold plasma Pasteurization microorganisms (d) group 80Hz 90Hz 100Hz 110Hz Total number of 0 5.98±0.21a ND 5.35±0.15b 5.11±0.06b 4.85±0.10c 4.52±0.25c colonies Fungus 0 5.09±0.12a ND 4.67±0.05b 4.31±0.06c 3.98±0.13d 3.56±0.23e Aerobic 0 5.09±0.12a ND 4.67±0.05a 4.31±0.06a 3.98±0.13c 3.56±0.23e bacteria Coliform 0 ND ND ND ND ND ND Total number of 7 7.19±0.05a ND 5.48±0.02b 5.30±0.02c 5.00±0.31c 4.65±0.lld colonies Fungus 7 6.61±0.02 ND ND ND ND ND Aerobic 7 6.61±0.02 ND ND ND ND ND bacteria Coliform 7 ND ND ND ND ND ND
Note: Different letters in the same row indicate significant differences between treatment groups, i.e. P<0.05; ND: not detected
Table 4. Changes in hardness (kg) during fresh-keeping storage of low-salt roseheart radish pickles that have not been treated, have been pasteurized, and have been treated by high-voltage electric field cold plasma-based sterilization
Time High-voltage electric field cold plasma Control group Pasteurization (d) 80Hz 90Hz 100Hz 110Hz 0 14.85±0.38bc 13.72±0.53a 15.14±0.72cd 15.07±0.32cd 15.85±0.22d 14.23±0.15ab 2 10.04±0.95a 10.86±0.17ab 11.68±0.78b 12.78±0.13c 13.89±0.77d 11.72±0.01b 7 9.96±0.25b 8.94±0.12a 10.29±0.86bc 11.48±0.99d 11.96±0.15d 11.10±0.23cd
Note: Different letters in the same row indicate significant differences between treatment groups, i.e. P<0.05
It can be seen from the above tables that for roseheart radish pickles, various microorganisms in the control group proliferated rapidly, which eventually caused spoilage and soft texture. Although pasteurization can kill fungi, bacteria, flatulent bacteria and other microorganisms, the thermal effect during sterilization severely damaged the texture of the pickles. It should be noted that the numbers of fungi, bacteria and flatulent bacteria in the pickles decreased slightly (0 d), but during storage (7 d), all fungi and flatulent bacteria in the pickles were killed, and the total number of colonies decreased significantly, which showed that that the high-voltage electric field plasma had post-treatment effects. On the other hand, the sterilization effect of high-voltage electric field plasma gradually increased with the frequency. When the frequency is higher than 100 Hz, the high frequency damages the texture of the pickles to some extent. Therefore, compared with the traditional pasteurization, the high-voltage electric field cold plasma-based sterilization had a better preservation effect.
Example 3 Low-salt Chinese cabbage pickle preservation method based on high-voltage electric field cold plasma-based sterilization
(1) Preparation of liquid packaging contents of the products: adjusting the total acidity of the pickling fermentation broth to 0.6% and the NaCl concentration thereof to 4% with drinking water;
(2) Fermentation of pickle raw materials: controlling the NaCl concentration of the fermentation brine of the pickles at 8%, controlling the fermentation temperature at 25°C, and fermenting for 7 days until the NaCl concentration of the pickles was 4%, the total acidity was 0.6%, and the total number of colonies was 106 CFU/mL;
(3) Packaging: adding the products in step (2) to the liquid packaging contents of the products in step (1) at a ratio of 1:1 (w/v) for packaging; and
(4) Sterilization treatment: A plasma generator including a voltage regulator, a high-voltage electric field generator, an upper electrode, a lower electrode, and an insulating protective plate was used. The packaged pickles were placed between the upper and lower electrodes. An upper insulating protective plate was arranged between the upper surface of the packaging box and the upper electrode. A lower insulating protective plate was arranged between the lower surface of the packing box and the lower electrode. The packaged pickles in step (3) underwent high-voltage electric field plasma-based sterilization under the conditions of 20°C and 70% RH, where the packaging bag (box) was placed between the two electrodes of the high-voltage electric field cold plasma-based sterilization device, and sterilized by a repeated short-duration sterilization method in which sterilization is repeated for 5 times at intervals of 60 s with a processing voltage intensity of 65 kV/cm, a frequency of 90, 100, 110, and 120 Hz, a current of 0.8 mA, and a single electric field action time of 60 s.
Roseheart radish pickles without plasma treatment under the same conditions were used as a control group, and were compared with pasteurized roseheart radish pickles. The Chinese cabbage pickles were stored at 30°C for 7 days. After plasma treatment (0 d) and storage for 7 days (7 d), the total number of colonies of Chinese cabbage pickles was measured according to GB 4789.2-2016, and the number of coliform bacteria in Chinese cabbage pickles was measured according to GB 4789.3-2016, and the total number of fungi in Chinese cabbage pickles was measured according to GB 4789.15-2016. The quantity of flatulent bacteria in Chinese cabbage pickles was measured by a picking culture method, and the hardness of Chinese cabbage pickles was measured by a texture analyzer.
The total numbers of bacteria, fungi, and flatulent bacteria and the hardness of Chinese cabbage pickles after sterilization were recorded as shown in Table 5 and Table 6.
Table 5. Sterilization results of low-salt Chinese cabbage pickles by high-voltage electric field cold plasma (total number of colonies: Log (CFU/g))
Types of Time Control Pasteurization High-voltage electric field cold plasma microorganisms (d) group 90 Hz 100 Hz 110 Hz 120 Hz Total number of 0 5.95±0.25a ND 5.12±0.13b 4.80±0.05b 4.43±0.02d 3.63±0.31e colonies Fungus 0 4.93±0.04a ND 4.57±0.08b 4.41±0.03c 4.10±0.06d 3.34±0.43e Aerobic bacteria 0 4.93±0.04b ND 4.57±0.08b 4.41±0.03c 4.10±0.06d 3.34±0.43e Coliform 0 ND ND ND ND ND ND Total number of 7 7.20±0.12a ND 5.21±0.06b 4.91±0.03c 4.53±0.10d 3.81±0.15e colonies Fungus 7 6.58±0.11 ND ND ND ND ND Aerobic bacteria 7 6.58±0.11 ND ND ND ND ND Coliform 7 ND ND ND ND ND ND
Note: Different letters in the same row indicate significant differences between treatment groups, i.e. P<0.05; ND: not detected
Table 6. Changes in hardness (kg) during fresh-keeping storage of low-salt Chinese cabbage pickles that have not been treated, have been pasteurized, and have been treated by high-voltage electric field cold plasma-based sterilization
Time High-voltage electric field cold plasma Control group Pasteurization (d) 90 Hz 100 Hz 110 Hz 120 Hz 0 14.77±0.12cd 13.70±0.22a 14.52±0.51bc 15.71±0.30e 15.22±0.47de 14.01±0.12ab 2 10.02±0.25a 10.79±0.13b 11.73±0.62c 13.80±0.lld 12.08±0.59c 11.99±0.26c 7 9.10±0.31a 9.02±0.17a 10.57±0.15b 12.77±0.54d 11.66±0.25c 11.42±0.36c
Note: Different letters in the same row indicate significant differences between treatment groups, i.e. P<0.05
It can be seen from the above tables that pasteurization can kill almost all the microorganisms in Chinese cabbage pickles, but it also had a strong destructive effect on the texture of Chinese cabbage pickles. The sterilization effect of high-voltage electric field plasma increased with the increase of frequency, especially had post-treatment effects on fungi and flatulent bacteria. After 7 days of storage, these two types of microorganisms were basically killed. Compared with the control group, the texture of the sterilized samples was significantly improved during the entire storage period, indicating that the high-voltage electric field cold plasma-based sterilization treatment can inhibit the sensory quality deterioration of Chinese cabbage pickles. But when the frequency was higher than 100 Hz, the suppression effect of the high-voltage electric field plasma on the texture deterioration weakened.
In summary, the high-voltage electric field plasma-based sterilization method can be applied to pickles to kill fungi, bacteria and flatulent bacteria, and also can inhibit the texture deterioration, so as to extend the shelf life of the products.
The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims (5)
1. A low-salt pickle preservation method by high-voltage electric field cold plasma-based sterilization, characterized by comprising the following steps:
(1) putting pickled and fermented low-salt pickles into a packaging bag (box), adjusting a NaCl concentration of a pickling fermentation broth to 2.5-4.0% and a total acidity thereof to 0.4-0.6%, adding the pickling fermentation broth to the packaging bag (box) at a ratio of pickles to pickling fermentation broth being 1:1 (w/v), and air-filled packaging; and
(2) putting the pickle product packaged in bag (box) between two electrodes of a high-voltage electric field cold plasma-based sterilization device, with processing parameters being as follows: a voltage intensity of 55-65 kV/cm, a working frequency of 70-120 Hz, and a working current of 0.3-0.8 mA, and sterilizing by a repeated short-duration sterilization method.
2. The low-salt pickle preservation method by high-voltage electric field cold plasma-based sterilization according to claim 1, characterized in that: under conditions of 50-70% RH and 15-20°C, the putting the packaging bag (box) between the two electrodes of the high-voltage electric field cold plasma-based sterilization device and sterilizing by the repeated short-duration sterilization method is: repeating sterilization 2-5 times at intervals of 20-60 s with a single electric field action duration of 20-60 s.
3. The low-salt pickle preservation method by high-voltage electric field cold plasma-based sterilization according to claim 1, characterized in that: the low-salt pickles are fermented using a fermentation brine having a NaCl concentration of 6.0-8.0% (w/v) at a fermentation temperature controlled at 25-30°C for 3-7 days until the NaCl concentration of the pickles is 2.5-4.0%, the total acidity is 0.4-0.6%, and the total number of colonies is 104-106 CFU/mL.
4. The low-salt pickle preservation method by high-voltage electric field cold plasma-based sterilization according to claim 1, characterized in that: the pickle raw materials comprise one or any combination of Chinese cabbage, cabbage, summer radish, carrot and roseheart radish.
5. The low-salt pickle preservation method by high-voltage electric field cold plasma-based sterilization according to claim 1, characterized in that: an atmosphere condition of air-filled packaging is 02/CO2/He/N2 = 30+5/30 5/105/305%.
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| CN114931200A (en) * | 2022-04-28 | 2022-08-23 | 苏州屹润食品科技有限公司 | Fresh wet noodle plasma active water preparation synergistic medium barrier cold sterilization fresh-keeping method |
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