Low-nitrite rose-flavored pickled vegetables and preparation method thereof

Abstract

The invention discloses low-nitrite rose-flavored pickled vegetables and a preparation method thereof, a rose immersion liquid is added into a pickled vegetable fermentation system, and the addition amount of the rose immersion liquid is 25-100% of the total liquid volume. Experimental data show that the method can significantly inhibit the generation of nitrite, and the peak content is reduced to 0.92 mg / kg or below, which is far lower than that of traditional pickled vegetables (about 3.0 mg / kg). Meanwhile, the total phenol content of the obtained rose-flavored pickled vegetables is up to 12.8-13.0 mg / g, the total flavone content is up to 2.23-6.32 mg / g, the DPPH free radical scavenging rate and the FRAP iron ion reducing capacity can be 3-10 times or above that of traditional pickled vegetables, and the rose-flavored pickled vegetables have unique rose flavor and a more stable fermentation pH environment. According to the method, the edible safety, the nutritional functionality and the flavor of the pickled vegetables are synchronously improved, and high-value utilization of rose processing byproducts is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of food processing technology, in particular to a functional rose-flavored pickle with low nitrite content and high antioxidant activity prepared from rose by-product and a preparation method thereof. BACKGROUND

[0002] As a traditional fermented vegetable food with a long history and unique flavor, pickle has a wide consumer group and cultural foundation worldwide, especially in East Asia. Pickle is mainly made of vegetables as raw materials, and is naturally fermented by microorganisms such as lactic acid bacteria. The process not only gives the product a unique sour and fresh flavor, but also produces certain probiotic functions. According to the Records of Materia Medica, pickle has the effect of "invigorating the spleen, appetizing, and removing greasy food", and is a good food to accompany meals.

[0003] However, there is a significant safety hazard in the production process of traditional naturally fermented pickles—high content of nitrite. Studies have shown that nitrate contained in vegetables can be reduced to nitrite by microorganisms (mainly nitrate-reducing bacteria). Nitrite can combine with amine substances in the human body to form strong carcinogens, nitrosamines, which can increase the risk of cancer if consumed for a long time, posing a potential threat to human health. Therefore, effectively controlling the content of nitrite in pickles is a key issue to improve the safety quality of pickles and promote the healthy development of the industry.

[0004] Currently, the main technical approaches to control nitrite in pickles include inoculating excellent lactic acid bacteria and adding natural inhibitors (such as vitamin C, tea polyphenols, etc.). These methods have certain effects, but still have limitations. Inoculating bacteria may have fermentation adaptability or flavor conflict problems; while adding chemical inhibitors may bring negative perception of "artificial addition" to consumers, and has limited contribution to the diversification of product flavor.

[0005] At the same time, in the processing of rose essential oil and rose flower products, a large amount of by-products—rose flower residue will be produced. These residues are usually discarded directly, not only causing waste of biological resources, but also bringing environmental pressure. It is worth noting that rose flower residue still retains rich active ingredients, including polyphenols and flavonoids, etc. These ingredients have been proven to have significant antioxidant, antibacterial, and other biological activities. How to realize the high-value utilization of such agricultural processing by-products has become an important issue in the deep processing and circular economy development of agricultural products.

[0006] In view of the above background, the application of rose processing by-products to the pickle fermentation system may open up a new path of "waste to treasure" to solve the nitrite safety problem of pickles. The active ingredients in rose infusion are expected to directly scavenge or inhibit the generation of nitrite through its strong antioxidant capacity, and its natural antibacterial properties may also have a beneficial regulatory effect on the fermentation microbial community. This combination of by-product resource utilization and food safety control not only fundamentally improves the safety of pickles, but also creates new growth points for the rose processing industry chain, in line with the current comprehensive needs of the food industry to pursue safety, health and sustainable development.

[0007] Therefore, the present study innovatively introduces rose infusion into the pickle fermentation system, aiming to develop a new type of functional rose-flavored pickle with low nitrite and high antioxidant activity and coordinated flavor, providing a new solution to the safety problems of traditional pickles and the high-value utilization of rose by-products. SUMMARY

[0008] The purpose of the present application is to overcome the shortcomings of the prior art and provide a rose-flavored pickle and a preparation method thereof, which can significantly reduce nitrite and greatly improve antioxidant function while imparting a unique flavor to the product.

[0009] The technical solution of the present application is a preparation method of low-nitrite rose-flavored pickle (as shown in Figure 1 The core of the method is to use rose infusion as a functional pickling liquid in the pickle fermentation system. The method uses active ingredients in rose infusion to inhibit the accumulation of nitrite.

[0010] Compared with the prior art, the beneficial effects of the present application (strongly supported by experimental data) are as follows: 1. Extremely low nitrite content: The present application uses pure natural rose infusion without the need for adding chemical preservatives or antioxidants, which can reduce the nitrite in pickles, as shown in Figure 2 The peak value of nitrite in rose-flavored pickle (0.92 mg / kg) is much lower than that in traditional pickle (3.0 mg / kg), with an inhibition effect of more than 69%.

[0011] 2. Excellent antioxidant performance: As can be seen from Figures 7-10 The total phenol content of rose-flavored pickle is as high as 12.8-13.0 mg / g, the total flavonoid content is 2.23-6.32 mg / g, and its DPPH free radical scavenging capacity and FRAP iron ion reducing capacity are several to ten times higher than that of traditional pickle, indicating that it has clear in vitro antioxidant function.

[0012] 3. Fermentation process is more gentle and stable: As can be seen from Figure 3It was found that the pH value of the rose-scented kimchi remained within a slightly acidic range of 3.92-4.08 throughout the 10-day fermentation period, while the pH value of traditional kimchi could drop below 3.3. This suggests that the rose infusion may have buffered the drastic changes in acidity during the fermentation process, contributing to a milder flavor and more stable quality.

[0013] 4. Flavor and Resource Utilization: The aromatic components of roses harmonize with the flavor of pickled vegetables, creating a novel sensory experience; at the same time, this invention uses inexpensive rose processing by-products as the main functional raw materials, turning waste into treasure, reducing production costs, and adding value to the rose industry chain, which meets the requirements of green and sustainable development.

[0014] 5. The process of this invention is simple, requires no complicated equipment, and is easy to improve and promote in traditional kimchi production processes. Attached Figure Description

[0015] Figure 1 Flowcharts of the production process for rose-scented pickles and traditional pickles.

[0016] Figure 2 Dynamic changes in nitrite content during fermentation of rose-scented pickles and traditional pickles.

[0017] Figure 3 A graph showing the dynamic changes in pH during the fermentation process of rose-scented pickles and traditional pickles.

[0018] Figure 4 Dynamic changes in electrical conductivity during the fermentation process of rose-scented pickles and traditional pickles.

[0019] Figure 5 A graph showing the dynamic changes in soluble solids content during fermentation of rose-flavored pickles and traditional pickles.

[0020] Figure 6 Dynamic changes in total acid content during fermentation of rose-scented pickles and traditional pickles.

[0021] Figure 7 Dynamic changes in total phenol content during fermentation of rose-scented pickles and traditional pickles.

[0022] Figure 8 Dynamic changes in total flavonoid content during fermentation of rose-scented pickles and traditional pickles.

[0023] Figure 9 Dynamic changes in DPPH scavenging rate during fermentation of rose-scented pickles and traditional pickles.

[0024] Figure 10 A graph showing the dynamic changes in the reducing power of iron ions during the fermentation process of rose-scented pickles and traditional pickles. Detailed Implementation

[0025] To better understand the present invention, the following embodiments and accompanying drawings further illustrate the content of the present invention. However, the content of the present invention is not limited to the following embodiments, and the embodiments should not be regarded as limiting the scope of protection of the present invention.

[0026] Materials and Methods Materials and Equipment Ingredients: Fresh Chinese cabbage (purchased from local Jiajiayue chain supermarket); food-grade refined salt and cane sugar; rose infusion (made from rose petal residue, a byproduct of rose essential oil processing, added to sterile water at a material-to-liquid ratio of 8:1-12:1 (g / mL), boiled for 20-40 minutes, filtered while hot to remove residue, and the collected filtrate is the rose infusion).

[0027] Equipment: pH meter; conductivity meter; ultraviolet spectrophotometer; colorimeter; Abbe refractometer.

[0028] 1.2 Preparation process of rose-scented pickled vegetables (1) Raw material processing: Select fresh cabbage, remove the outer old leaves and roots, keep the inner core, wash with clean water and dry the surface moisture, and cut into 2 cm wide strips.

[0029] (2) Preparation of auxiliary materials and jar filling: Boil water and rose infusion for 20-40 minutes to sterilize, and cool to room temperature for later use. Put the prepared shredded cabbage, 5%-7% salt, 2%-4% sucrose, and the above pickling solution into a sterilized fermentation jar, ensuring that all ingredients are completely submerged in the liquid. Set up a blank control group (distilled water + salt + sugar) and a rose experimental group (rose infusion + salt + sugar).

[0030] (3) Sealed fermentation: Seal the mouth of the jar using the water seal method (spray with 75% alcohol for disinfection before use), and then place the fermentation jar in a constant temperature incubator at 25-30℃ and let it ferment for 6-10 days.

[0031] 1.3 Measurement methods and conditions (1) Determination of nitrite content in kimchi: Referring to GB5009.33-2016, the naphthylethylenediamine hydrochloride method was adopted; (2) Determination of pH, conductivity and soluble solids in kimchi: The pH and conductivity of the solution were measured using the potentiometry method; the soluble solids content was determined using an Abbe refractometer.

[0032] (3) Determination of total acidity in kimchi: Refer to the phenolphthalein indicator titration method in GB12456-2021. Weigh 25 g of the sample (accurate to 0.01 g) and place it in a 150 ml Erlenmeyer flask equipped with a condenser. Add approximately 50 ml of carbon dioxide-free water at 80 °C, mix well, and boil in a boiling water bath for 30 min (stirring 2-3 times to ensure all organic acids in the sample are dissolved in the solution). Remove from the bath, cool to room temperature, and dilute to 250 mL with carbon dioxide-free water. Filter through rapid filter paper and collect the filtrate for determination. Based on the possible total acid content of the sample, pipette 25 mL of the solution into a 250 mL Erlenmeyer flask, add 2 drops (10 g / L) of phenolphthalein indicator, and titrate with 0.01 mol / L sodium hydroxide standard titration solution until a faint red color persists for 30 seconds. Record the volume of 0.01 mol / L sodium hydroxide standard titration solution consumed.

[0033] (4) Determination of antioxidants in kimchi: Total phenols and total flavonoids were determined by the Folin-Ciocalteu method and the aluminum salt colorimetric method, respectively. (5) Determination of DPPH free radical scavenging power and FRAP Fe3+ reducing power in kimchi: Accurately weigh 5,000 g of kimchi sample into a 50 mL centrifuge tube, add 40 mL of 80% methanol solution, extract ultrasonically for 0.5 h, filter, and repeat the extraction process twice on the remaining residue in the centrifuge tube. Combine the filtrates, evaporate the solvent under reduced pressure at 45 °C, collect the concentrated liquid, and make up to 25 mL with 80% methanol solution. This is the extract, which should be stored at -25 °C in the dark.

[0034] Take 2 mL of the extract, add 2 mL of 0.2 mM DPPH-ethanol standard solution, mix thoroughly, and let stand for 20 min. Measure the absorbance at 516 nm to calculate the DPPH free radical scavenging power. Prepare the FRAP working solution fresh. Take 0.6 mL of the extract, add 3.4 mL of FRAP working solution, and incubate in a water bath at 37℃ in the dark for 0.5 h. Measure the absorbance at 593 nm to calculate the FRAP Fe3+ reducing power. For the blank control of the FRAP Fe3+ reducing power, use 80% methanol solution instead of the sample extract. Plot a standard curve using Trolox as the standard, and express the results as μmol FeSO4 / g.

[0035] (6) Sensory evaluation Using a 100-point system, a judging panel of 10 professionally trained food science students drained the kimchi, chopped it into pieces about 1cm in size, and placed it on a disposable white plate. They observed its color and shape, smelled its aroma, and tasted its flavor and texture. Each group rinsed their mouths with purified water and rested before continuing to taste. The kimchi products were evaluated from four aspects: color, aroma, texture, and flavor. The sensory score was the average of the judging panel's scores.

[0036] 1.4 Data Processing All physicochemical and antioxidant index measurements were performed in triplicate, and the results are expressed as mean ± standard deviation. Significance analysis was performed using SPSS 22.0 software (p < 0.05), and graphs were generated using Origin 2021 software.

[0037] Results and Analysis Determining the optimal amount of rose infusion added The effects of different amounts of rose infusion (25%-100%) on the peak nitrite content of kimchi were investigated through single-factor experiments. The results showed that the peak nitrite content in all experimental groups with added rose infusion was significantly lower than that in the blank control group.

[0038] 2.2 Inhibitory effect of rose infusion on nitrite in pickled vegetables The dynamic changes in nitrite content during fermentation of rose-scented pickles and traditional pickles are as follows: Figure 2 As shown, the nitrite content of both types of kimchi exhibited a "nitrite peak" characteristic, first increasing and then decreasing. However, the peak nitrite content of the traditional kimchi appeared on day 3, reaching as high as 3.0 mg / kg; while the peak of the rose-flavored kimchi was significantly lower, at only 0.92 mg / kg, with an inhibition rate of 69.3%. This indicates that the addition of rose infusion can effectively inhibit the formation and accumulation of nitrite during fermentation.

[0039] 2.3 Comparison of Physicochemical and Functional Indicators between Rose-Scented Pickles and Traditional Pickles The key indicators were compared as follows based on a multi-dimensional quality evaluation of the product after fermentation (data is the average of three replicates): Basic physicochemical indicators: Rose-scented pickles are significantly superior to traditional pickles in basic physicochemical indicators. Their pH value remains stable within the range of 3.92-4.08, and their conductivity fluctuates very little, both indicating that the rose infusion creates a milder and more stable fermentation environment. Simultaneously, the soluble solids content of rose-scented pickles is consistently significantly higher than that of traditional pickles (e.g., Figure 5 As shown), it retains more flavor and nutrients, and the total acid content remains stable at about 0.4%, significantly lower than the sourness of traditional kimchi, which reaches a maximum of 6.8% in the later stages. In contrast, traditional kimchi not only has a pH as low as 3.28, but also a dramatic increase in conductivity in the early stages (as shown). Figure 4As shown in the figure, the intense metabolism also leads to a large consumption of soluble solids, further demonstrating the comprehensive advantages of rose-flavored pickles in terms of fermentation stability, substance retention, and mild flavor.

[0040] Functional ingredients and activities: (1) Total phenol content: Muscat kimchi has a total phenol content of 12.8-13.025 mg / g, while traditional kimchi has only 3.74 mg / g, which is about 4 times higher.

[0041] (2) Total flavonoid content: 2.23-6.32 mg / g for Muscat kimchi and 1.24 mg / g for traditional kimchi, which is about 3.1 times higher.

[0042] (3) Antioxidant activity: The DPPH free radical scavenging rate and FRAP iron ion reducing capacity (53.4 μmol FeSO4 / g) of the rose-scented pickles are more than 3 times that of traditional pickles (14.36 μmol FeSO4 / g).

[0043] 2.4 Exploration of the Mechanism of Action Based on the above test results, the mechanism by which rose extract reduces the nitrite content in kimchi is mainly attributed to its direct chemical reduction effect. The polyphenols (≥12.8 mg / g) and flavonoids (≥2.23 mg / g) abundant in rose extract possess strong antioxidant and reducing properties, enabling them to directly and rapidly react with the nitrite generated in the fermentation system, reducing and decomposing it, thereby significantly reducing the peak accumulation of nitrite.

[0044] 2.5 Sensory Quality Evaluation of Products Sensory evaluation results (Table 1) show that rose-scented pickles are significantly superior to traditional pickles in aroma and taste. They have a harmonious rose fragrance and fermented sourness, without excessive sourness or astringency, and a crisp and tender texture, making them more generally acceptable.

[0045] Table 1. Comparison of sensory scores between rose-scented kimchi and traditional kimchi (out of 100)

[0046] in conclusion This invention successfully developed a novel rose-scented kimchi by introducing rose infusion (25%-100%) into the traditional kimchi fermentation system. This product significantly inhibits nitrite formation (peak value ≤0.92 mg / kg) and is rich in natural antioxidants (total phenols ≥12.8 mg / g, total flavonoids ≥2.23 mg / g), with antioxidant activity more than three times that of traditional kimchi. Simultaneously, the product possesses a unique rose flavor and more harmonious sensory qualities. This invention not only provides an effective solution for improving the safety of kimchi consumption but also opens up a new path for the high-value utilization of rose processing byproducts.

Claims

1. Application of rose infusion in the preparation of low-nitrite pickles.

2. The method for preparing the rose infusion according to claim 1, characterized in that, It is obtained by water extraction of rose petal residue, a by-product of rose essential oil processing. The specific preparation method is as follows: take rose petal residue, add sterile water at a material-to-liquid ratio of 8:1-12:1 (g / mL), boil and extract for 20-40 minutes, filter while hot to remove residue, and collect the filtrate as rose extract.

3. A method for preparing low-nitrite rose-flavored pickles, characterized in that, Includes the following steps: (1) Raw material processing: Select fresh cabbage, remove the outer old leaves and roots, keep the inner core, wash with clean water and dry the surface moisture, and cut into 2 cm wide strips. (2) Preparation of auxiliary materials and filling of jars: Boil water and rose infusion for 20-40 minutes to sterilize and cool to room temperature for later use; put the prepared cabbage shreds, 5%-7% salt, 2%-4% sucrose and the above pickling liquid into the sterilized fermentation jar, ensuring that all ingredients are completely submerged below the liquid surface. (3) Sealed fermentation: Seal the mouth of the jar using the water seal method (spray with 75% alcohol for disinfection before use), and then place the fermentation jar in a constant temperature incubator at 25-30℃ and let it ferment for 6-10 days.

4. The method for preparing low-nitrite rose-flavored pickles according to claim 3, characterized in that, In step (2), the amount of salt added is 6% of the weight of the cabbage, and the amount of sucrose added is 3% of the weight of the cabbage.

5. The method for preparing low-nitrite rose-flavored pickles according to claim 3, characterized in that, The fermentation temperature in step (3) is 27°C and the fermentation time is 10 days.

6. The method for preparing low-nitrite rose-flavored pickles according to claim 3, characterized in that, The nitrite content during fermentation was detected using the naphthylethylenediamine hydrochloride method. The nitrite content in the finished product was ≤0.92mg / kg, which was significantly lower than the final nitrite content of ordinary pickled vegetables (≥2.5mg / kg).

7. A low-nitrite rose-flavored pickle, prepared by the method according to any one of claims 3-5.

8. The rose-scented pickled vegetables according to claim 7, characterized in that, Its total phenol content is not less than 12.8 mg / g, and its total flavonoid content is not less than 2.23 mg / g.

9. The rose-scented pickled vegetables according to claim 7, characterized in that, Its DPPH free radical scavenging rate and FRAP iron ion reducing ability are at least 3 times that of traditional kimchi (without rose infusion).

10. The low-nitrite rose-flavored pickles according to claim 4, characterized in that, Its FRAP iron ion reducing power is not less than 53.4 μmol FeSO4 / g.

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