Fermented cauliflower and fermentation method thereof

Abstract

According to the fermented cauliflower and the fermentation method thereof, an efficient and safe process for fermenting the cauliflower by single bacteria of plant lactobacillus is developed, flower balls, stems and leaves of the cauliflower are processed into fermented vegetables, the high retention rate of thioglycoside and phenolic compounds in the cauliflower is achieved, the content of nitrite is reduced, and the yield of the cauliflower is improved. The broccoli fermentation broth shows great advantages in color, aroma, texture and taste, is simple in process, low in cost and high in efficiency, and provides technical support for the broccoli fermentation industry.

Description

Technical Field

[0001] This invention relates to the field of cauliflower fermentation technology, specifically to a fermented cauliflower and its fermentation method. Background Technology

[0002] Currently, cauliflower is primarily consumed fresh and can be cooked with various vegetables. However, people are only accustomed to eating the florets, which are highly nutritious and have potential cancer-preventive properties. Because fresh cauliflower florets are prone to spoilage and have a short shelf life after harvesting, processing methods such as fresh-cutting, freezing, blanching, and drying are used to extend their shelf life, discarding the stems and leaves. Therefore, finding improved preservation methods to enhance cauliflower quality is extremely important. Currently, research on cauliflower stems and leaves is relatively limited, focusing mainly on silage. Further exploration and development are needed to explore other processing methods for cauliflower stems and leaves.

[0003] The resource utilization of cruciferous vegetable by-products such as cauliflower stems and leaves mainly relies on lactic acid bacteria fermentation, with *Lactobacillus plantarum* becoming a core strain due to its acid and temperature resistance. Existing technologies largely focus on multi-strain synergistic fermentation or compound additive processes, such as using *Lactobacillus brevis* and *Lactobacillus plantarum* in combination, and improving the total acid content and vitamin C retention rate of the product through wet or dry pickling. For the high-value utilization of glucosinolates and phenolic compounds, some studies have achieved partial retention of glucosinolates and biotransformation of phenolic compounds through strain screening and metabolic regulation. Furthermore, to address the inhibition of fermentation efficiency by high-temperature environments, existing technologies propose optimizing silage quality by adjusting the moisture content of raw materials or adding auxiliary materials such as bran; however, these methods still suffer from high process complexity and increased costs. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings and deficiencies of the existing technology and to provide a fermented cauliflower and its fermentation method.

[0005] The technical solution adopted by this invention is as follows: The first aspect of this invention provides a fermentation method for fermented cauliflower, comprising the following steps: S1. Inoculate *Lactobacillus plantarum* into MRS liquid medium and culture to obtain a viable bacterial count concentration of 1 × 10⁻⁶. 6 -2×10 6 Fermentation agent at CFU / ml; S2. Prepare a 5-7% salt solution to obtain the fermentation broth; S3. Using fresh cauliflower heads and / or stems and / or leaves as raw materials, wash and cut the raw materials into pieces, add them to the fermentation container along with the fermentation liquid, add the fermentation agent, stir well, and ferment at a constant temperature of 20-30℃ until the total acid content reaches 0.45-0.55% and fermentation is complete.

[0006] Preferably, step S1 specifically includes the following steps: dissolving freeze-dried *Lactobacillus plantarum* powder in MRS liquid culture medium to obtain a bacterial suspension; activating the bacterial suspension by culturing it at 37 ℃ for 24–48 h in a constant temperature incubator; mixing the activated bacterial suspension with MRS liquid culture medium and then culturing it at 37 ℃ for 1 day in a constant temperature incubator for expansion; inoculating the expanded bacterial suspension into MRS liquid culture medium at an inoculation rate of 2% (v / v) and incubating it statically at 37 ℃ for 24 h.

[0007] Preferably, in step S1, the MRS liquid culture medium comprises the following components: 10 g / L peptone, 10 g / L beef extract, 5.0 g / L yeast extract, 20 g / L glucose, 3.0 g / L sodium acetate, 2.0 g / L diammonium hydrogen citrate, 1 mL / L Tween-80, 2.0 g / L dipotassium hydrogen phosphate, 0.2 g / L magnesium sulfate, and 0.04 g / L manganese sulfate; the pH of the culture medium is 5.5-5.9.

[0008] Preferably, in step S1, the viable cell concentration of the fermentation agent is 1.5 × 10⁻⁶. 6 CFU / ml.

[0009] Preferably, in step S3, the mass ratio of raw materials to fermentation broth is 1:(3-5).

[0010] Preferably, in step S3, the amount of fermenting agent added is 1-3 wt%.

[0011] A second aspect of the present invention provides a fermented cauliflower, which is prepared by the fermentation method described above.

[0012] The beneficial effects of this invention are as follows: This invention develops a highly efficient and safe single-strain fermentation process for cauliflower using *Lactobacillus plantarum*, processing cauliflower heads, stems, and leaves into fermented vegetables. This process achieves a high retention rate of glucosinolates and phenolic compounds in cauliflower while reducing nitrite content. It demonstrates significant advantages in cauliflower fermentation, especially in the color, aroma, texture, and flavor of fermented cauliflower stems and leaves. Furthermore, the process is simple, low-cost, and highly efficient, successfully turning waste into treasure and providing technical support for the cauliflower fermentation industry. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0014] Figure 1 The dynamic changes in nitrite content during the fermentation of cauliflower stems and leaves in Example 1 and Comparative Example 1; Figure 2 The dynamic changes in nitrite content during the fermentation of cauliflower heads in Example 1 and Comparative Example 1; Figure 3 The dynamic changes in total acid content during the fermentation of cauliflower stems and leaves in Example 1 and Comparative Example 1 are shown. Figure 4 The dynamic changes in total acid content during the fermentation of cauliflower heads in Example 1 and Comparative Example 1 are shown. Figure 5 The dynamic changes in pH content during the fermentation of cauliflower stems and leaves in Example 1 and Comparative Example 1; Figure 6 The dynamic changes in pH value during the fermentation of cauliflower heads in Example 1 and Comparative Example 1; Figure 7 The dynamic changes in lactic acid bacteria count during the fermentation of cauliflower stems and leaves in Example 1 and Comparative Example 1 are shown. Figure 8 The dynamic changes in lactic acid bacteria count during the fermentation of cauliflower heads in Example 1 and Comparative Example 1 are shown. Figure 9 The dynamic changes in L-value content during the fermentation of cauliflower stems and leaves in Example 1 and Comparative Example 1; Figure 10 The dynamic changes in L-value content during the fermentation of cauliflower heads in Example 1 and Comparative Example 1; Figure 11 The dynamic changes in A value content during the fermentation of cauliflower stems and leaves in Example 1 and Comparative Example 1; Figure 12 The dynamic changes in A value content during the fermentation of cauliflower heads in Example 1 and Comparative Example 1; Figure 13 The dynamic changes in B-value content during the fermentation of cauliflower stems and leaves in Example 1 and Comparative Example 1; Figure 14 The dynamic changes in B-value content during the fermentation of cauliflower heads in Example 1 and Comparative Example 1 are shown. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0016] The bacterial strain involved in the following examples is Lactiplantibacillus planttarum CICC 20765, which was purchased from the China Industrial Microbial Culture Collection Center. The MRS liquid culture medium involved includes the following components: peptone 10 g / L, beef extract 10 g / L, yeast extract 5.0 g / L, glucose 20 g / L, sodium acetate 3.0 g / L, diammonium hydrogen citrate 2.0 g / L, Tween-80 1 mL / L, dipotassium hydrogen phosphate 2.0 g / L, magnesium sulfate 0.2 g / L, and manganese sulfate 0.04 g / L; the pH of the medium is adjusted to 5.7 ± 0.2.

[0017] Example 1 This embodiment provides a method for fermenting cauliflower with Lactobacillus plantarum, specifically including the following steps: (1) Activation and expansion of *Lactobacillus plantarum*: Using a sterile pipette, dissolve 0.1 g of lyophilized *Lactobacillus plantarum* powder completely in approximately 0.5 mL of MRS liquid culture medium in a lyophilized tube. Transfer the dissolved bacterial suspension to a test tube containing 4–5 mL of MRS liquid culture medium and mix well. Incubate the test tube at 37 °C for 24–48 h to activate the bacterial suspension. Pipette 1–2 mL of the activated bacterial suspension into a test tube containing MRS liquid culture medium and mix well. Incubate the test tube at 37 °C for 1 day to expand the bacterial suspension.

[0018] (2) Preparation of fermentation agent: The expanded bacterial suspension was inoculated into MRS liquid medium at an inoculation rate of 2% (v / v) and incubated at 37 ℃ for 24 h to obtain a viable bacterial count concentration of 1.5 × 10⁻⁶. 6 Fermentation agent at CFU / ml.

[0019] (3) Preparation of fermentation broth: Boil water from the ultrapure water apparatus, let it cool, and then add salt at a low salt concentration of 6% to obtain the fermentation broth.

[0020] (4) Cauliflower fermentation: Fresh cauliflower florets, stems and leaves are used as raw materials. They are washed, cut into pieces, and placed in a 1.2 L ceramic fermentation tank with fermentation liquid at a material-to-liquid ratio of 1:4. Then, 2 wt% of fermentation agent is added, stirred evenly, and fermented at a constant temperature of 25℃. When the total acid (calculated as lactic acid) content reaches about 0.5%, the fermentation endpoint can be considered reached.

[0021] Comparative Example 1 This comparative example provides a method for naturally fermenting cauliflower, which specifically includes the following steps: (1) Preparation of fermentation broth: Boil water from the ultrapure water apparatus, let it cool, and then add salt at a low salt concentration of 6% to obtain the fermentation broth.

[0022] (2) Cauliflower fermentation: Fresh cauliflower heads, stems and leaves are used as raw materials. They are washed, cut into pieces, and placed in a 1.2 L ceramic fermentation tank with fermentation liquid at a material-to-liquid ratio of 1:4. 2% MRS liquid culture medium is added, stirred evenly, and sealed for fermentation at room temperature. When the total acid (calculated as lactic acid) content reaches about 0.5%, the fermentation endpoint can be considered reached.

[0023] Samples from Example 1 and Comparative Example 1 were taken and tested at 0 d, 0.5 d, 1 d, 1.5 d, 2 d, 3 d, 4 d, and 5 d, respectively. The results are as follows: 1. Dynamic changes in nitrite levels During fermentation, the nitrates in the cauliflower head, stems, and leaves are reduced to nitrites by nitrate reductase. Nitrate reductase is produced by bacteria, and different bacterial species have a significant impact on its production. Once ingested, nitrites combine with nitrogenous compounds in the body to form nitrosamines, potent carcinogens that seriously endanger human health. National and local standards impose strict requirements on nitrite content, stipulating that nitrites (calculated as sodium nitrite) in fermented vegetables should not exceed 20 mg / kg.

[0024] from Figure 1 and Figure 2 It can be seen that in Example 1, the cauliflower heads, stems, and leaves fermented with *Lactobacillus plantarum* and in Comparative Example 1, which were naturally fermented, all showed peak values ​​between 0.5 and 1.5 days of fermentation, and these peak values ​​were far below the national standard. The peak values ​​of the four fermentation groups were different, from highest to lowest: cauliflower heads fermented naturally in Comparative Example 1 (1.93 mg / kg), cauliflower heads fermented with *Lactobacillus plantarum* in Example 1 (1.78 mg / kg), cauliflower stems and leaves fermented with *Lactobacillus plantarum* in Example 1 (1.77 mg / kg), and cauliflower stems and leaves fermented naturally in Comparative Example 1 (1.70 mg / kg). This indicates that *Lactobacillus plantarum* fermentation can effectively reduce the peak nitrite content of cauliflower heads. Subsequently, the nitrite content decreased rapidly, remaining relatively stable after 3 days except for the naturally fermented cauliflower heads; the naturally fermented cauliflower heads remained stable after 4 days. Furthermore, after fermentation, the nitrite content of *Lactobacillus plantarum* fermentation was lower than that of naturally fermented cauliflower. Therefore, fermentation with Lactobacillus plantarum can further reduce the nitrite content in fermented cauliflower, greatly improving its safety for consumption.

[0025] 2. Dynamic changes in total acidity The amount of acid produced by fermented vegetables is an important indicator for measuring fermentation performance. Figure 3 , Figure 4The dynamic changes in total acid content during the fermentation of cauliflower stems and leaves in Example 1 and Comparative Example 1, and during the fermentation of cauliflower heads in Example 1 and Comparative Example 1, are shown respectively. The total acid content of cauliflower heads, stems, and leaves fermented in both Comparative Example 1 and Example 1 gradually increased, with the acid production rate of Example 1 being greater than that of Comparative Example 1. This demonstrates that *Lactobacillus plantarum* fermentation can accelerate the fermentation rate and shorten the fermentation cycle.

[0026] After fermentation, the total acid content of cauliflower heads fermented with *Lactobacillus plantarum* reached 3.50 g / kg, which is higher than the 3.24 g / kg of naturally fermented cauliflower heads. The total acid content of cauliflower stems and leaves fermented with *Lactobacillus plantarum* reached 2.96 g / kg, which is higher than the 2.52 g / kg of naturally fermented cauliflower stems and leaves. This indicates that *Lactobacillus plantarum* fermentation can increase the production of total acid in the fermentation products, which is highly beneficial for the fermentation of cauliflower heads, stems, and leaves using *Lactobacillus plantarum*.

[0027] 3. Dynamic changes in pH Figure 5 , Figure 6 The figures show the dynamic changes in pH value during the fermentation of cauliflower stems and leaves in Example 1 and Comparative Example 1, and during the fermentation of cauliflower heads in Example 1 and Comparative Example 1. As can be seen from the figures, the pH value of cauliflower heads, stems, and leaves gradually decreased during both natural fermentation and fermentation with *Lactobacillus plantarum*, with the rate of pH decrease being greater during *Lactobacillus plantarum* fermentation than during natural fermentation. This indicates that *Lactobacillus plantarum* fermentation can accelerate the fermentation process and shorten the fermentation cycle.

[0028] After 1 day of fermentation, the pH values ​​of cauliflower heads, stems, and leaves fermented with *Lactobacillus plantarum* were all less than 4.0. After fermentation, the pH values ​​of these fermentations were all below 3.2. Throughout the fermentation process, the pH values ​​of *Lactobacillus plantarum* fermentation were consistently lower than those of natural fermentation. These results indicate that *Lactobacillus plantarum* fermentation accelerates the decrease in the total pH value of the fermentation products. Natural fermentation, on the other hand, involves a higher number of miscellaneous bacteria and a slower rate of growth, resulting in a slower pH decrease. This advantage is highly beneficial for the fermentation of cauliflower heads, stems, and leaves using *Lactobacillus plantarum*.

[0029] 4. Dynamic changes in the count of *Lactobacillus* from lactic acid plants Figure 7 , Figure 8The figures show the dynamic changes in *Lactobacillus plantarum* counts during the fermentation of cauliflower stems and leaves in Example 1 and Comparative Example 1, and during the fermentation of cauliflower heads in Example 1 and Comparative Example 1. As can be seen from the figures, the lactic acid bacteria counts in cauliflower heads, stems, and leaves during both natural fermentation and *Lactobacillus plantarum* fermentation reached their peak after 0.5 days of fermentation, with the count in Example 1 being higher than that in Comparative Example 1. After fermentation was complete, the *Lactobacillus plantarum* count in Example 1 was higher than that in Comparative Example 1. The experimental results indicate that during natural fermentation, other microorganisms inhibited the growth of *Lactobacillus plantarum*, and that *Lactobacillus plantarum* fermentation could accelerate the growth of lactic acid bacteria in the fermentation products.

[0030] 5. Dynamic changes in chromaticity Figure 9 , Figure 10 This figure shows the dynamic changes in L-values ​​of cauliflower heads, stems, and leaves fermented in Example 1 and Comparative Example 1. The L-value represents the degree of brightness. As shown in the figure, the L-values ​​of both *Lactobacillus plantarum* fermentation and natural fermentation gradually decrease, indicating that the gloss of the fermentation product gradually darkens during fermentation. After fermentation, the L-value of *Lactobacillus plantarum* fermentation is greater than that of natural fermentation. This indicates that *Lactobacillus plantarum* fermentation can improve the gloss of the fermentation product.

[0031] Figure 11 , Figure 12 This figure shows the dynamic changes in the A value of cauliflower heads, stems, and leaves fermented in Example 1 and Comparative Example 1. The A value represents both red and yellow colors. As shown in the figure, the A value gradually increases during both *Lactobacillus plantarum* fermentation and natural fermentation, indicating that the color of the fermentation product gradually changes from red to yellow during the fermentation process. After fermentation, the A value of *Lactobacillus plantarum* fermentation is greater than that of natural fermentation. This indicates that *Lactobacillus plantarum* fermentation can make the fermentation product more yellow.

[0032] Figure 13 , Figure 14 This figure shows the dynamic changes in the B-values ​​of cauliflower heads, stems, and leaves fermented in Example 1 and Comparative Example 1. The B-value represents both green and blue colors. As shown in the figure, the B-values ​​of *Lactobacillus plantarum* fermentation and natural fermentation gradually increase, indicating that the color of the fermentation product gradually changes from green to blue during fermentation. After fermentation, the B-value of *Lactobacillus plantarum* fermentation is greater than that of natural fermentation. This indicates that *Lactobacillus plantarum* fermentation can make the fermentation product color further away from green.

[0033] 6. Sensory evaluation results Ten sensory evaluators were selected to conduct sensory evaluations on cauliflower heads, stems and leaves fermented with Lactobacillus plantarum and naturally fermented. They scored the cauliflower heads, stems and leaves on color (20 points), aroma (20 points), texture (20 points), taste (20 points) and overall evaluation (20 points) during the fermentation process.

[0034] Sensory evaluation standards for low-salt pickled vegetables were formulated in accordance with "A Discussion on the Quality Assessment and Standards of Chinese Pickled Vegetables". The sensory evaluation standards are shown in Table 1, with a total score of 100 points for each item. The results are shown in Table 2.

[0035] Table 1 Sensory Evaluation Criteria Table 2 Sensory evaluation results of cauliflower heads, stems and leaves fermented with Lactobacillus plantarum and naturally fermented. The scores show that Lactobacillus plantarum fermentation has advantages in terms of color, aroma, texture and taste of cauliflower stems and leaves, as well as overall evaluation.

[0036] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A fermentation method for fermented cauliflower, characterized in that, Includes the following steps: S1. Inoculate *Lactobacillus plantarum* into MRS liquid medium and culture to obtain a viable bacterial count concentration of 1 × 10⁻⁶. 6 -2×10 6 Fermentation agent at CFU / ml; S2. Prepare a 5-7% salt solution to obtain the fermentation broth; S3. Using fresh cauliflower heads and / or stems and / or leaves as raw materials, wash and cut the raw materials into pieces, add them to the fermentation container along with the fermentation liquid, add the fermentation agent, stir well, and ferment at a constant temperature of 20-30℃ until the total acid content reaches 0.45-0.55% and fermentation is complete.

2. The fermentation method for fermented cauliflower according to claim 1, characterized in that, Step S1 specifically includes the following steps: dissolving freeze-dried *Lactobacillus plantarum* powder in MRS liquid culture medium to obtain a bacterial suspension; activating the bacterial suspension by culturing it at 37 ℃ for 24–48 h in a constant temperature incubator; mixing the activated bacterial suspension with MRS liquid culture medium and then culturing it at 37 ℃ for 1 day in a constant temperature incubator for expansion; inoculating the expanded bacterial suspension into MRS liquid culture medium at an inoculation rate of 2% (v / v) and incubating it statically at 37 ℃ for 24 h.

3. The fermentation method for fermented cauliflower according to claim 1, characterized in that: In step S1, the MRS liquid culture medium comprises the following components: 10 g / L peptone, 10 g / L beef extract, 5.0 g / L yeast extract, 20 g / L glucose, 3.0 g / L sodium acetate, 2.0 g / L diammonium hydrogen citrate, 1 mL / L Tween-80, 2.0 g / L dipotassium hydrogen phosphate, 0.2 g / L magnesium sulfate, and 0.04 g / L manganese sulfate; the pH of the culture medium is 5.5-5.

9.

4. The fermentation method for fermented cauliflower according to claim 1, characterized in that: In step S1, the viable cell concentration of the fermentation agent is 1.5 × 10⁻⁶. 6 CFU / ml.

5. The fermentation method for fermented cauliflower according to claim 1, characterized in that: In step S3, the mass ratio of raw materials to fermentation broth is 1:(3-5).

6. The fermentation method for fermented cauliflower according to claim 1, characterized in that: In step S3, the amount of fermenting agent added is 1-3 wt%.

7. A fermented cauliflower, characterized in that: It is prepared by the fermentation method described in any one of claims 1-6.

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