Sterilization method of dregs vinegar

Abstract

The invention relates to the technical field of food sterilization, and discloses a dreg vinegar sterilization method which comprises the steps of ultrasonic pretreatment, intensive pulse light sterilization, gradient low-temperature heat sterilization and cooling, specifically, ultrasonic pretreatment destroys a microbial structure, intensive pulse light and gradient low-temperature heat synergistic sterilization is carried out under the nitrogen protection condition, and the dreg vinegar is obtained. According to the steps, the microbial structure is destroyed through the physical effect, the follow-up sterilization load is reduced, and the unification of efficient sterilization and high-quality preservation is achieved. According to the sterilization method based on combined use of intensive pulse light and low-temperature heat sterilization, the shelf life of the dregs vinegar is prolonged, and meanwhile the beneficial ingredients and flavor of the dregs vinegar are reserved to the maximum extent.

Description

Technical Field

[0001] This invention relates to the field of food sterilization technology, and more specifically, to a method for sterilizing vinegar made from fermented grains. Background Technology

[0002] Zhaobo vinegar is a unique traditional fermented food from Hainan. It is made primarily from rice or glutinous rice, which is fermented to produce lees, which are then blended with chili oil and garlic oil. Zhaobo vinegar is characterized by its sour, spicy, savory, and fragrant flavor, and is rich in protein, polypeptides, amino acids, and various organic acids, exhibiting potential health benefits. In recent years, as a newly emerging hot pot condiment, Zhaobo vinegar has gradually evolved into a signature consumer product for Hainan tourism, with significant growth in market demand.

[0003] However, the shelf life of commercially available vinegar made from fermented grains currently varies from a few days to several months, and the limitations of sterilization methods severely restrict the development of the vinegar industry. Pasteurization leads to the loss of nutrients and flavor in vinegar made from fermented grains. Adding additives such as potassium sorbate raises consumer concerns. Pulsed light sterilization is a cold sterilization technology that uses high-intensity, broad-spectrum pulsed light to inactivate microorganisms, thus better preserving the product's flavor. Combining this with low-temperature heat sterilization extends the shelf life of vinegar made from fermented grains, maximizing the preservation of its beneficial components and flavor.

[0004] Therefore, developing a synergistic sterilization method based on "ultrasonic pretreatment, pulsed intense light, and gradient low-temperature heat" is of great practical significance. This method can achieve a balance between efficient sterilization and high-quality preservation by physically disrupting the structure of microorganisms and reducing the subsequent sterilization load. Summary of the Invention

[0005] In view of this, the present invention proposes a sterilization method for vinegar made from fermented grains, aiming to solve the problems of large nutrient loss, high energy consumption and short shelf life in the current sterilization technology for vinegar made from fermented grains.

[0006] This invention proposes a method for sterilizing vinegar made from fermented grains, comprising the following steps: (1) Ultrasonic pretreatment: Take unsterilized vinegar residue and pretreat it under ultrasonic conditions; (2) Pulsed light sterilization: The ultrasonically pretreated vinegar is sterilized under nitrogen protection by controlling the flow rate of the vinegar under pulsed light to obtain pulse-sterilized vinegar. (3) Gradient low-temperature heat sterilization: The pulse-sterilized lees vinegar is subjected to heat preservation treatment, which includes a first stage heat preservation and a second stage heat preservation, to obtain pulse and low-temperature heat-sterilized lees vinegar. (4) Cooling: The vinegar residue after sterilization in step (3) is cooled immediately to obtain sterilized vinegar residue.

[0007] Furthermore, the unsterilized vinegar in step (1) has a pH of 3-4 and a turbidity of 5-15 NTU.

[0008] Furthermore, the frequency of the ultrasonic wave in step (1) is 20~40kHz, the power is 150~350W, and the processing time is 3~8min.

[0009] Furthermore, the pulsed intense light parameters in step (2) are: wavelength 200~1100nm, intensity 200~400J, number of pulses 30~70, and irradiation distance 10~15cm.

[0010] Furthermore, the flow rate of the vinegar in step (2) is 5-8 mL / s.

[0011] Furthermore, in step (3), the first stage heat preservation temperature is 45-50℃ and the heat preservation time is 2-5min, and the second stage heat preservation temperature is 55-70℃ and the heat preservation time is 1-4min.

[0012] Furthermore, the cooling described in step (4) is cooling to 15~25°C.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: The sterilized vinegar prepared by this invention has improved the retention rate of total flavonoids, total phenols and total acids, which can effectively maintain the nutritional and health value of the vinegar.

[0014] The technical solution of this invention can achieve the triple action of microbial cell membrane destruction, DNA inactivation and spore inactivation, with qualified total colony count and extended shelf life under sealed conditions at room temperature. Its sterilization efficiency and shelf life performance are good.

[0015] The overall energy consumption of this invention is 80% of that of existing pulsed high-intensity light-low-temperature thermal technology. It does not require the addition of chemical preservatives, avoids safety hazards, and is both energy-efficient and safe.

[0016] This invention achieves a balance between efficient sterilization and high-quality preservation by physically disrupting the structure of microorganisms and reducing the subsequent sterilization load.

[0017] This invention, through parameter gradient design, can be adapted to raw materials of vinegar made from lees with different turbidity or pH, has a wide range of applications, and strong process stability. Detailed Implementation

[0018] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0019] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0020] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0021] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0022] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0023] This invention provides a method for sterilizing vinegar made from fermented grains, comprising the following steps: (1) Ultrasonic pretreatment: Take unsterilized vinegar residue and pretreat it under ultrasonic conditions; (2) Pulsed light sterilization: The ultrasonically pretreated vinegar is sterilized under nitrogen protection by controlling the flow rate of the vinegar under pulsed light to obtain pulse-sterilized vinegar. (3) Gradient low-temperature heat sterilization: The pulse-sterilized lees vinegar is subjected to heat preservation treatment, which includes a first stage heat preservation and a second stage heat preservation, to obtain pulse and low-temperature heat-sterilized lees vinegar. (4) Cooling: The vinegar residue after sterilization in step (3) is cooled immediately to obtain sterilized vinegar residue.

[0024] The unsterilized vinegar in step (1) of this invention has a pH of 3-4 and a turbidity of 5-15 NTU.

[0025] In the method for sterilizing vinegar residue, this invention selects the pH and turbidity of the vinegar residue raw material, as excessively high turbidity will weaken the ultrasonic air effect.

[0026] This invention does not impose any specific limitations on the type of raw material for vinegar made from fermented grains; any fermented grains known to those skilled in the art can be used.

[0027] The preferred parameters of the ultrasonic wave in step (1) of this invention are: frequency 20~40kHz, power 150~350W, and processing time 3~8min, and more preferably, frequency 20~30kHz, power 150~300W, and processing time 3~5min.

[0028] In the sterilization method of vinegar residue, the present invention selects ultrasonic pretreatment of vinegar residue. The ultrasonic pretreatment is to generate a "cavitation effect" in the vinegar body by ultrasonic waves, the microbubbles formed rapidly expand and rupture, release local shear force and shock wave, destroy the cell membrane of lactic acid bacteria and yeast (causing leakage of contents), and cause micro-damage to the spore wall of spore-forming microorganisms, thereby increasing the sensitivity of microorganisms to subsequent sterilization steps.

[0029] The pulsed high light parameters in step (2) of this invention are preferably: wavelength 200~1100nm, intensity 200~400J, number of pulses 30~70, and irradiation distance 10~15cm. More preferably, wavelength 200~1000nm, intensity 200~350J, number of pulses 30~60, and irradiation distance 10~13cm.

[0030] The flow rate of the vinegar made from lees in step (2) of this invention is preferably 5-8 mL / s, and more preferably 5-7 mL / s.

[0031] This invention introduces nitrogen gas throughout the sterilization process. On the one hand, this avoids the oxidation and browning of polyphenols and esters in the vinegar caused by strong light exposure. On the other hand, nitrogen gas acts as an insulator, preventing any reaction with the components in the vinegar. The continuous introduction of nitrogen gas gradually replaces the air in the sterilization system, reducing the oxygen content and minimizing the generation of reactive oxygen species at the source. If no nitrogen gas is added and the system is exposed to air, the oxidation loss rate of polyphenols and esters in the vinegar will increase, and the brightness of the color will decrease.

[0032] The irradiation distance described in this invention is a selectively controlled distance. Too close a distance can easily lead to localized overheating, while too far a distance results in insufficient light intensity. The pulse wavelength can destroy the dimer of microbial DNA, preventing its replication and assisting in the destruction of the cell membrane. This is suitable for vulnerable microorganisms after ultrasonic pretreatment, without requiring additional high energy. The pulse intensity is designed to match the synergy of ultrasonic pretreatment. Since ultrasound has already destroyed the microbial cell membrane through cavitation, inactivation can be achieved without high energy. If the intensity is too high, it will over-excite reactive oxygen species, potentially leading to an increase in polyphenol oxidation. If the intensity is too low, it cannot completely inactivate the spore precursors that were not completely destroyed by ultrasound, resulting in an excessive total colony count. Furthermore, it is matched with a gradient low-temperature heat treatment. The intensity is controlled at 200-350J to inactivate only the vegetative cells and some spores. The remaining damaged spores are completely removed by subsequent low-temperature heat treatment, avoiding the drawbacks of requiring high energy to inactivate spores with a single strong light source. The selection of the number of pulses is to balance the thoroughness of inactivation with process efficiency, and to adapt to the flow rate parameters, ensuring inactivation while avoiding component degradation due to prolonged irradiation.

[0033] This invention selects and controls the flow rate of the vinegar residue during the sterilization process. The flow rate control is to ensure that the vinegar body is in full contact with the strong light and there are no sterilization dead spots. In particular, the pulsed strong light energy can destroy the DNA structure, thereby achieving efficient inactivation of fragile microorganisms after ultrasonic pretreatment.

[0034] In step (3) of the present invention, the first stage heat preservation temperature is 45~50℃ and the heat preservation time is 2~5min, and the second stage heat preservation temperature is 55~70℃ and the heat preservation time is 1~4min. More preferably, the first stage heat preservation temperature is 45~48℃ and the heat preservation time is 2~4min, and the second stage heat preservation temperature is 55~65℃ and the heat preservation time is 1~3min.

[0035] The first stage of heat preservation in this invention is to inactivate the remaining microbial vegetative cells and spore precursors, with the temperature below the spore germination threshold to avoid spore activation; the second stage of heat preservation is to inactivate the damaged spores; compared with the prior art, the heat preservation time is shortened and the heat preservation temperature is lowered, which can reduce the impact of high temperature on the quality of the lees vinegar.

[0036] The cooling in step (4) of the present invention is preferably cooled to 15~25°C, and more preferably cooled to 20~25°C.

[0037] This invention cools the vinegar residue to below 25°C immediately after gradient low-temperature heat sterilization, thus avoiding the degradation of components caused by continuous preheating.

[0038] The sterilized vinegar made from fermented grains according to this invention shall have its total acidity, total phenols, total flavonoids, DPPH free radical scavenging rate, viable bacteria count, color, shape, aroma, and taste measured.

[0039] This invention uses spectrophotometry to determine the content of total phenols and total flavonoids and the DPPH free radical scavenging rate, acid-base titration to determine the total acid content, PCA plate counting to determine the total bacterial count, and sensory evaluation to determine color, appearance, aroma, and taste.

[0040] In this invention, the fermented product, vinegar made from fermented grains, contains total acid, total phenol, and total flavonoids. The total acid content is an important indicator for evaluating the flavor and stability of the vinegar. The content of total phenols and total flavonoids reflects the antioxidant and anti-inflammatory health benefits of the vinegar; the DPPH free radical scavenging rate reflects the antioxidant capacity of the vinegar; the viable bacteria count is a direct indicator of sterilization effectiveness; and color, appearance, aroma, and taste are important sensory evaluation indicators of the vinegar, reflecting its product quality.

[0041] In this invention, unless otherwise specified, all raw materials required for preparation are commercially available products well known to those skilled in the art.

[0042] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0043] Example 1 (1) Ultrasonic pretreatment: Take unsterilized vinegar with pH 3.8 and turbidity 8 NTU, and pretreat it for 3 min under ultrasonic conditions at a frequency of 20 kHz and a power of 150 W. (2) Pulsed light sterilization: The ultrasonically pretreated lees vinegar is sterilized by pulsed light with a flow rate of 5 mL / s for 30 pulses under nitrogen protection conditions by controlling the flow rate of lees vinegar and using pulsed light with a wavelength of 200 nm, an intensity of 200 J, and an irradiation distance of 10 cm. Pulsed sterilized lees vinegar is obtained. (3) Gradient low temperature heat sterilization: The pulse-sterilized lees vinegar is subjected to heat preservation treatment, which includes a first stage heat preservation and a second stage heat preservation. The first stage heat preservation is at 45℃ for 2 minutes, and the second stage heat preservation is at 55℃ for 1 minute, to obtain lees vinegar sterilized by pulse strong light and low temperature heat. (4) Cooling: The vinegar residue after sterilization in step (3) is immediately cooled to 20°C to obtain sterilized vinegar residue.

[0044] Example 2 (1) Ultrasonic pretreatment: Take unsterilized vinegar with pH 3.2 and turbidity 15 NTU, and pretreat it for 5 min under ultrasonic conditions at a frequency of 35 kHz and a power of 300 W. (2) Pulsed light sterilization: The ultrasonically pretreated lees vinegar is sterilized by pulsed light with a flow rate of 7 mL / s for 60 pulses under nitrogen protection conditions by controlling the flow rate of lees vinegar and 1000 nm wavelength, 350 J intensity, and 13 cm irradiation distance. Pulsed sterilized lees vinegar is obtained. (3) Gradient low temperature heat sterilization: The pulse-sterilized lees vinegar is subjected to heat preservation treatment, which includes a first stage heat preservation and a second stage heat preservation. The first stage heat preservation is at 48°C for 4 minutes, and the second stage heat preservation is at 65°C for 3 minutes, to obtain lees vinegar sterilized by pulse strong light and low temperature heat. (4) Cooling: The vinegar residue after sterilization in step (3) is immediately cooled to 25°C to obtain sterilized vinegar residue.

[0045] Example 3 (1) Ultrasonic pretreatment: Take unsterilized vinegar with pH 3.5 and turbidity 12 NTU, and pretreat it for 4 min under ultrasonic conditions at a frequency of 25 kHz and a power of 250 W. (2) Pulsed light sterilization: The ultrasonically pretreated lees vinegar is sterilized by pulsed light with a flow rate of 6 mL / s for 45 pulses under nitrogen protection conditions by controlling the flow rate of lees vinegar and irradiation distance of 600 nm, 300 J, and 12 cm, to obtain pulse-sterilized lees vinegar. (3) Gradient low temperature heat sterilization: The pulse-sterilized lees vinegar is subjected to heat preservation treatment, which includes a first stage heat preservation and a second stage heat preservation. The first stage heat preservation is at 47°C for 3 minutes, and the second stage heat preservation is at 60°C for 2 minutes, to obtain lees vinegar sterilized by pulse strong light and low temperature heat. (4) Cooling: The vinegar residue after sterilization in step (3) is immediately cooled to 22°C to obtain sterilized vinegar residue.

[0046] Comparative Example 1 Unsterilized vinegar residue with pH 3.5 and turbidity 12 NTU, the same as in the example, was heated from room temperature to 68°C at a rate of 5°C / min using the industry's traditional heat sterilization method. The temperature was maintained at a stable 68°C for 25 minutes. After sterilization, it was naturally cooled to 25°C and tested using the same method as in Example 1.

[0047] Comparative Example 2 Unsterilized vinegar residue with pH 3.5 and turbidity 12 NTU, the same as in the example, was used to directly test the raw material.

[0048] Performance testing: This invention uses spectrophotometry to determine the content of total phenols and total flavonoids, as well as the DPPH free radical scavenging rate; acid-base titration to determine the total acid content; and PCA plate counting to determine the total bacterial count. Sensory evaluation is also conducted to assess color, appearance, aroma, and taste. The test results of the sterilized vinegar prepared in Examples 1-3 and the unsterilized vinegar prepared in Comparative Examples 1-2 are shown in Table 1 below: Table 1. Detection results of vinegar made from fermented grains in Examples 1-3 and Comparative Examples 1-2

[0049] In summary, compared to traditional heat sterilization and non-sterilization processes, the sterilization method of this invention, which combines pulsed intense light and low-temperature heat sterilization, extends the shelf life of vinegar while preserving its beneficial components and flavor to the greatest extent. It also eliminates pathogenic bacteria residue, exhibits good stability, allows for large-scale production, and facilitates easy control of inoculation amounts during preparation and processing. This method is suitable for continuous production and industrialized vinegar manufacturing. Furthermore, it solves the problems of significant nutrient loss, high energy consumption, and short shelf life associated with traditional vinegar sterilization technologies, as well as the safety and short shelf life of unsterilized raw materials, thus achieving a technological breakthrough.

[0050] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. The scope of protection of the present invention is determined by the appended claims.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for sterilizing vinegar made from fermented grains, characterized in that, Includes the following steps: (1) Ultrasonic pretreatment: Take unsterilized vinegar residue and pretreat it under ultrasonic conditions; (2) Pulsed light sterilization: The ultrasonically pretreated vinegar is sterilized under nitrogen protection by controlling the flow rate of the vinegar under pulsed light to obtain pulse-sterilized vinegar. (3) Gradient low-temperature heat sterilization: The pulse-sterilized lees vinegar is subjected to heat preservation treatment, which includes a first stage heat preservation and a second stage heat preservation, to obtain pulse and low-temperature heat-sterilized lees vinegar. (4) Cooling: The vinegar residue after sterilization in step (3) is cooled immediately to obtain sterilized vinegar residue.

2. The sterilization method for vinegar made from fermented grains according to claim 1, characterized in that, The unsterilized vinegar in step (1) has a pH of 3-4 and a turbidity of 5-15 NTU.

3. The sterilization method for vinegar made from fermented grains according to claim 1, characterized in that, The ultrasonic frequency in step (1) is 20~40kHz, the power is 150~350W, and the processing time is 3~8min.

4. The sterilization method for vinegar made from fermented grains according to claim 1, characterized in that, The pulsed high light parameters in step (2) are: wavelength 200~1100nm, intensity 200~400J, number of pulses 30~70, and irradiation distance 10~15cm.

5. The sterilization method for vinegar made from fermented grains according to claim 1, characterized in that, The flow rate of the vinegar in step (2) is 5~8 mL / s.

6. The sterilization method for vinegar made from fermented grains according to claim 1, characterized in that, Step (3) The first stage of heat preservation temperature is 45~50℃ and the heat preservation time is 2~5min. The second stage of heat preservation temperature is 55~70℃ and the heat preservation time is 1~4min.

7. The sterilization method for vinegar made from fermented grains according to claim 1, characterized in that, The cooling mentioned in step (4) is to cool to 15~25℃.

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