A physical synergistic spice sterilization and preservation method for fresh dried bean curd sticks

Abstract

The application discloses a physical synergistic spice sterilization and preservation method for fresh dried beancurd sticks and belongs to the technical field of fresh dried beancurd stick storage and preservation. The application combines ultraviolet, spices and irradiation methods to perform composite treatment on fresh dried beancurd sticks, and better preservation advantages are shown, the composite treatment effectively inhibits the growth of microorganisms, and the fresh dried beancurd stick preservation period can be prolonged by at least 5 days. The ultraviolet sterilization can not only sterilize the surface of the fresh dried beancurd sticks, but also reduce the microbial pollution in the environment; the spices are safe and have the dual effects of seasoning and sterilization; and the final irradiation sterilization can further reduce the content of microorganisms, so that the preservation period is prolonged. The material and operation method are simple and convenient, safe, and more suitable for normal temperature and low temperature preservation of the fresh dried beancurd sticks.

Description

Technical Field

[0001] This invention relates to the field of fresh bean curd storage and preservation technology, specifically to a physical synergistic spice sterilization and preservation method for fresh bean curd. Background Technology

[0002] Dried bean curd sticks contain 45%-50% protein and about 20% fat, as well as carbohydrates, vitamins, and minerals. They are a good source of plant-based protein, providing essential nutrients and potentially helping to lower blood cholesterol and prevent Alzheimer's disease. Fresh bean curd sticks are undried and can be eaten directly without rehydration. They typically have a moisture content of over 50% and a smooth texture. Compared to dried bean curd sticks, fresh bean curd sticks are softer and more nutritious, but due to their higher moisture content and the absence of preservatives, they are more prone to the growth of spoilage microorganisms.

[0003] In production, dried bean curd sticks are easy to preserve and do not easily spoil. Many scholars have focused on the impact of soybean varieties, 7S / 11S protein ratio, soaking temperature, and additives on the quality of dried bean curd sticks. However, with rising living standards and changing lifestyles, additive-free, natural fresh bean curd sticks are becoming increasingly sought after, leading to a gradual increase in their consumption. Currently, the main storage methods for fresh bean curd sticks are refrigeration and freezing. Refrigeration has a short storage time, while freezing affects the texture and taste. In addition, physical and chemical sterilization are commonly used preservation methods. Physical sterilization mainly includes microwave, ultraviolet, and irradiation methods, while chemical methods primarily use natural and synthetic preservatives. In recent years, research on the preservation of fresh bean curd sticks has focused primarily on chemical preservation methods, with sodium diacetate, natamycin, tea polyphenols, and natural plant extracts all being used. For example, Chinese patent CN 105285140B discloses a method for preserving fresh dried bean curd sticks, mainly using natamycin as a preservative and employing vacuum packaging and microwave sterilization technology, which can preserve fresh dried bean curd sticks for 46-52 days. However, the use of natamycin poses safety risks. Chinese patent CN 114947038 A discloses a compound preservative for fresh dried bean curd sticks, mainly using sodium propionate, calcium propionate, and sodium diacetate as preservatives. Orthogonal experiments determined the optimal compound concentrations of the three preservatives to be 0.15%, 0.10%, and 0.08%, but the preservation time is short. Chinese patent CN 114287551 A discloses a preservative for fresh dried bean curd sticks and a method for preparing fresh dried bean curd sticks, mainly utilizing 10... 5 -10 6 A CFU / ml suspension of *Lactobacillus plantarum* LY-78 eliminates the safety concerns posed by food additives to consumers, but it significantly alters sensory quality. Therefore, designing and developing a safe physicochemical synergistic sterilization, flavoring, and preservation method is of significant practical importance for the preservation of fresh dried bean curd sticks. Summary of the Invention

[0004] In view of the above-mentioned prior art, the purpose of this invention is to provide a physical synergistic spice sterilization and preservation method for fresh dried bean curd sticks.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A first aspect of the present invention provides a spice extract, made from the following raw materials in parts by weight:

[0007] 0.1-5 parts fennel, 0.1-5 parts Sichuan pepper, 0.1-5 parts cloves, 0.1-5 parts cinnamon.

[0008] In a second aspect, the present invention provides the application of the spice extract in the sterilization and preservation of fresh dried bean curd sticks.

[0009] A third aspect of the present invention provides a physical synergistic spice sterilization and preservation method for fresh dried bean curd sticks, comprising the following steps:

[0010] Fresh dried bean curd sticks were irradiated under ultraviolet light, then soaked in the spice extract, drained, and treated with electron beam irradiation.

[0011] Furthermore, the ultraviolet irradiation wavelength is 254 nm, the irradiation distance is 10-50 cm, and the irradiation time is 0-60 min.

[0012] Furthermore, the mass ratio of fresh dried bean curd sticks to spice extract is 1:(1-10), the soaking temperature is 10-25 ℃, and the soaking time is 0.5-5 h.

[0013] Furthermore, the electron beam irradiation is β-ray, the sterilization dose is 0-10 kGy, and the sterilization time is 1-30 min.

[0014] The beneficial effects of this invention are:

[0015] This invention combines ultraviolet light, spices, and irradiation to treat fresh dried bean curd sticks, resulting in superior preservation. The combined treatment effectively inhibits microbial growth, extending the shelf life of fresh bean curd sticks at room temperature by at least 5 days. Ultraviolet sterilization not only disinfects the surface of the fresh bean curd sticks but also reduces microbial contamination in the environment; spices are not only highly safe but also have both flavoring and sterilizing effects; and the final irradiation sterilization further reduces the microbial content, thus extending the shelf life. The materials and equipment used in this invention are simple and readily available, the operation is convenient and easy, and the safety is high, making it particularly suitable for the room temperature and low temperature preservation of fresh bean curd sticks. Attached Figure Description

[0016] Figure 1The effects of ultraviolet sterilization on the sensory properties, color, and total bacterial count of fresh dried bean curd sticks.

[0017] Figure 2 The effects of spice type on the sensory properties, color, and total bacterial count of fresh dried bean curd sticks.

[0018] Figure 3 The effects of different spice ratios on the sensory properties and color of fresh dried bean curd sticks.

[0019] Figure 4 The effect of irradiation treatment on the total bacterial count of fresh bean curd sticks.

[0020] Figure 5 Effects of UV, spice compound extract, irradiation and compound treatment on sensory scores of fresh dried bean curd sticks. Detailed Implementation

[0021] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0022] To enable those skilled in the art to better understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to specific embodiments.

[0023] The test materials used in the embodiments of this invention, unless otherwise specified, are all conventional test materials in the art and can be purchased through commercial channels. The room temperature in the embodiments was 15±1℃.

[0024] Example 1: Effects of UV sterilization on the sensory properties, color, moisture content, and total bacterial count of fresh dried bean curd sticks

[0025] 50 g of fresh dried bean curd sticks were placed 30 cm away from a UV lamp (254 nm), with a UV irradiation intensity of 2 W / m². 2The UV sterilization time was set to 0 min, 15 min, 30 min, and 60 min. After storage at 4 ℃ for 5 days, sensory evaluation, color difference, moisture content, and total bacterial count were determined. Sensory evaluation uses a 100-point scale, scoring taste, color, aroma, and texture. Scores are divided into five levels: Level 1: Tender and smooth texture, pure flavor, pale yellow and bright color with a glossy sheen, aroma of soy products, and good chewiness (81-100 points); Level 2: Relatively tender and smooth texture, relatively pure flavor, pale yellow color, lacking gloss, weak soy product aroma with no off-odors, and good chewiness (61-80 points); Level 3: Average taste and flavor, dark yellow color without gloss, lacking soy product aroma, slightly sour taste, and average chewiness, with no commercial value (41-60 points); Level 4: Poor taste and flavor, yellowish-brown color without gloss, rancid odor, poor chewiness, sticky, and with no commercial value (21-40 points); Level 5: Extremely poor taste and flavor, brownish-brown color without gloss, strong rancid odor, sticky and soft with no chewiness, and with no commercial value (0-20 points).

[0026] Moisture content was determined according to the direct drying method in GB 5009.3-2016 "National Food Safety Standard - Determination of Moisture in Food". Total bacterial count was determined according to GB 4789.2-2016 "National Food Safety Standard - Microbiological Examination of Food - Determination of Total Bacterial Count". Sensory evaluation standards were developed according to GB / T 21172-2022 "Guidelines for Sensory Evaluation of Product Color". Color was measured using a conventional colorimeter, and the results were recorded. L , a , b Value. The effects of ultraviolet sterilization on the color and moisture content of fresh dried bean curd sticks are shown in Table 1:

[0027] Table 1. Effects of UV sterilization on the color and moisture content of fresh dried bean curd sticks

[0028]

[0029] As shown in Table 1, with the extension of sterilization time, L The value decreased from 75.49 to 68.34, and the color of the dried bean curd sticks became duller. a Value and b The moisture content of fresh dried bean curd increased. Meanwhile, the moisture content decreased with increasing UV sterilization time, reaching 44.85% after 60 minutes. Overall, both 15-minute and 30-minute treatments had minimal impact on the quality of fresh dried bean curd.

[0030] according to Figure 1China A Figure 1 In section B, with the extension of UV sterilization time, the edges of fresh dried bean curd treated for 30 minutes began to turn yellowish-brown due to moisture loss, but it still had commercial value. The edges of the bean curd treated for 60 minutes showed significant wrinkling, affecting its sensory appeal and rendering it commercially worthless. Figure 1 As shown in Figure C, after 6 days of storage at 4 ℃, there was no significant difference in the total bacterial count of fresh bean curd sticks after UV sterilization at 0 min and 15 min, which were 7.70 lg CFU / g and 7.60 lg CFU / g, respectively. However, the total bacterial count after UV sterilization at 30 min and 60 min decreased by 75.61% and 78.78% respectively compared with the control group, indicating a good inhibitory effect on microbial growth.

[0031] In summary, UV treatment for 30 minutes is the most effective method for treating fresh dried bean curd sticks.

[0032] Example 2: Effects of spice type on the sensory properties, color, and total bacterial count of fresh dried bean curd sticks

[0033] Eight spices—cinnamon, Sichuan pepper, cloves, nutmeg, star anise, fennel, garlic, and ginger—were divided into eight treatment groups. After drying, the samples were passed through a 120-mesh sieve. For each treatment group, 25g of spices were packaged in gauze and boiled in 250ml of distilled water for 30 minutes. After filtration and cooling, spice extracts were obtained. 50g of fresh dried bean curd sticks were soaked in 150ml of the extract for 2 hours, drained, and then placed in a sealed plastic bag. A distilled water treatment was used as a control group. Each treatment was repeated three times. Sensory evaluation, color difference, and total bacterial count were determined at room temperature. The effect of spice type on the color of fresh dried bean curd sticks is shown in Table 2.

[0034] Table 2. Effects of spice type on the color of fresh dried bean curd sticks

[0035]

[0036] Table 2 shows that, after 24 hours of storage at room temperature, fresh bean curd skin soaked in spice extract showed better results than fresh bean curd skin treated with nutmeg and garlic. L The values ​​were higher than those in the water treatment group and the treatment groups containing fennel, cloves, Sichuan pepper, and cinnamon. L The value decreased significantly, and the color of the dried bean curd sticks darkened; the fennel, clove, and cinnamon treatment groups... a The value increased significantly; the cinnamon and fennel treatment groups showed higher b values. value.

[0037] like Figure 2As shown in Figures A and B, after being placed at room temperature (16±1℃) for 24 hours, the fennel, clove, cinnamon, Sichuan pepper, and star anise treatments darkened in color, and none of the treatments exhibited a noticeable rancid odor; all displayed the unique aroma of the spices. Compared to the water treatment, the nutmeg, garlic, and ginger treatments maintained a better appearance and color, while the clove treatment resulted in a dark brown color. The fresh fennel, garlic, clove, and nutmeg treatments exhibited a spice aroma. The garlic and ginger treatments showed significant softening and loss of elasticity after soaking for 2 hours.

[0038] like Figure 2 As shown in Figure C, after soaking fresh bean curd sticks in spice extracts and storing them at room temperature for 24 hours, the total bacterial count in the bean curd sticks treated with cinnamon, cloves, and fennel decreased compared to those treated with water, indicating a better antibacterial effect, especially cinnamon. Furthermore, although cloves did not receive high sensory evaluation, they had a certain bactericidal effect. While nutmeg alone had a poor antibacterial effect, it had little impact on the sensory characteristics of the fresh bean curd sticks. Garlic and ginger showed poor treatment effects and were not used. Future experiments will focus on reducing the amount of spices used in combination to improve the bactericidal effect while mitigating the influence of spices on the color and aroma.

[0039] Example 3: Effects of different spice ratios on the sensory properties, color, and total bacterial count of fresh dried bean curd sticks

[0040] Star anise, fennel, Sichuan pepper, cloves, cinnamon, and nutmeg were dried, mixed according to the proportions in Table 3, wrapped in gauze, and boiled in distilled water for 30 minutes. After filtration and cooling, the spice extract was obtained. The proportions in Table 3 are the weight percentages of each spice in the solvent distilled water.

[0041] Table 3 Specific implementation schemes for different spice ratios

[0042]

[0043] 50 g of fresh dried bean curd sticks were soaked in 150 mL of extract for 2 h, drained, and then placed in a plastic bag and stored at room temperature. The results are shown in Table 4.

[0044] Table 4. Effects of spice extract compounding on color difference and total bacterial count of fresh dried bean curd sticks

[0045]

[0046] like Figure 3 China A and Figure 3 As shown in Table B, the sensory scores of all four compound treatments were above 65 points. Among them, compound 1, compound 2, and compound 4 showed better sensory evaluation results, exceeding 70 points, and all exhibited a pleasant braising aroma. Table 4 shows that the fresh tofu skin treated with water... L The highest value was found in the four compound treatments of fresh dried bean curd sticks.L The values ​​all decreased, and the color became slightly darker; the compound 2 of dried bean curd sticks... b The compound treatment showed the highest value and significantly higher yellowness than other treatments. Therefore, the compound treatment can improve the sensory quality and enhance the flavor of fresh bean curd sticks. Compared with water, the total bacterial count of bean curd sticks treated with compound 3 did not change significantly, while compound 1, compound 2, and compound 4 significantly inhibited the growth of microorganisms in fresh bean curd sticks, reducing them by 2.8%, 11.3%, and 21.3% respectively compared with the control group.

[0047] Overall, the fresh dried bean curd treated with compound 4 showed the best results.

[0048] Example 4: Effect of spice concentration on the color and total bacterial count of fresh dried bean curd sticks

[0049] The spices were mixed according to the compound ratio of 4 (fennel: Sichuan pepper: clove: cinnamon = 0.49%: 0.49%: 0.25%: 0.49%) in Example 3, wrapped in gauze, and boiled in distilled water for 2 hours. The mass-volume ratio of the spices was 10 g / L, 20 g / L, and 50 g / L. After filtration and cooling, the spice extract was obtained and stored at 4 °C for later use. 50 g of fresh dried bean curd was soaked in 150 mL of the spice extract for 5 minutes, drained, and then placed in a plastic sealed bag. Fresh dried bean curd soaked in distilled water was used as a control group. The color difference and total bacterial count were determined after 24 hours at room temperature. The results are shown in Table 5.

[0050] Table 5. Effects of spice concentration on the color and total bacterial count of fresh dried bean curd sticks.

[0051]

[0052] As shown in Table 5, after treatment with spice extracts of different concentrations, L The value decreased. a Among several concentrations, the 20 g / L treatment showed the best color effect. Regarding the total bacterial count, the inhibitory effect on microbial growth became more pronounced with increasing spice extract concentration. The 50 g / L treatment group showed a 20.5% reduction in total bacterial count compared to the control group. While the 50 g / L treatment group showed better antibacterial effect than the 20 g / L treatment, its sensory appeal was diminished. The color and concentration of flavor compounds in the spice extract significantly impacted the sensory quality of fresh bean curd sticks; higher concentrations resulted in a darker extract color, more significant color changes in the soaked bean curd sticks, and a stronger spice flavor. Therefore, considering both the sensory quality and antibacterial effect of the fresh bean curd sticks, a 20 g / L spice concentration was ultimately chosen for treatment.

[0053] The preparation steps for the compound extract in subsequent experiments are as follows: The spices were mixed according to the mass ratio (fennel: Sichuan pepper: clove: cinnamon = 0.49%: 0.49%: 0.25%: 0.49%), wrapped in gauze, and boiled in distilled water for 2 hours. The mass-to-volume ratio of spices to distilled water was 20 g / L. After filtration and cooling, the compound extract was obtained and stored at 4 ℃ for later use.

[0054] Example 5: Effects of irradiation treatment on the sensory properties, color, moisture content, and total bacterial count of fresh dried bean curd sticks

[0055] Fresh dried bean curd sticks were packaged in 50 g units using thickened self-sealing bags. The bean curd sticks were then irradiated with β-electron beams at doses of 4 kGy, 6 kGy, and 8 kGy for 1 min, with untreated samples serving as controls. Each treatment was repeated three times. Color difference, moisture content, and total bacterial count were measured. The results are shown in Table 6.

[0056] Table 6. Effects of irradiation sterilization on the color and moisture content of fresh dried bean curd sticks.

[0057]

[0058] As shown in Table 6, after irradiation treatment, the fresh bean curd sticks... L value, a and b All decreased slightly, with the 6 kGy irradiation treatment showing the following: L It decreased by 1.28% compared to the control group. b The value decreased by 4.60%. Compared with the control, fresh bean curd treated with 8 kGy irradiation... L The value decreased by 4.52%. b The moisture content was reduced by 10.43% compared to the control, and the fresh bean curd sticks had a dull and lackluster color. In terms of moisture content, compared to the control, the moisture content of the irradiated bean curd sticks was slightly lower; the decrease was only 2.06% after 6 kGy irradiation, while the decrease was significant (2.65%) after 8 kGy irradiation. Figure 4 It can be seen that different doses of irradiation treatment significantly inhibited microbial growth. The total number of colonies in the control group was 6.06 lg cfu / g. The total number of colonies in the 6 kGy irradiated bean curd was significantly lower than that in the control group, only 3.38 lg cfu / g, which was 99.79% lower than that in the control group. The 8 kGy irradiation treatment reduced the number of colonies by 99.89% compared with the control group, but there was no significant difference between the 6 kGy and 8 kGy treatments.

[0059] This demonstrates that 6 kGy irradiation treatment achieves a good overall effect without affecting the sensory quality of fresh dried bean curd sticks.

[0060] Example 6: Effects of UV, Spices, Irradiation and Combined Treatments on the Preservation of Fresh Tofu Skin

[0061] Fresh dried bean curd sticks of uniform condition were taken and divided into five groups of 50 g each. Each group was designed with three replicates. The experimental environment temperature was 15±1 ℃.

[0062] Control group: 50 g of fresh dried bean curd sticks were soaked in distilled water for 2 hours.

[0063] UV treatment: Place 50 g of fresh dried bean curd sticks at a UV lamp (254 nm) 30 cm away for 30 min, with an irradiation intensity of 2 W / m. 2 .

[0064] Treatment of compound extract: Soak 50 g of fresh dried bean curd in the compound extract prepared according to the method in Example 4 for 2 hours, then remove and drain the surface water.

[0065] Irradiation treatment: Place 50 g of fresh bean curd sticks in a sterilized No. 5 thickened self-sealing bag and irradiate the bean curd sticks with an electron beam of 6 kGy for 1 min.

[0066] Composite treatment: Fresh dried bean curd sticks were subjected to UV treatment, compound extract treatment, and irradiation treatment in sequence. Specifically, 50 g of fresh dried bean curd sticks were placed under a UV lamp (254 nm) at a distance of 30 cm for 30 min, with an irradiation intensity of 2 W / m². 2 Afterwards, the UV-treated fresh bean curd sticks were soaked in the compound extract prepared according to the method in Example 4 for 2 hours, and then drained of surface moisture. Finally, the fresh bean curd sticks treated with the compound extract were placed in a sterilized No. 5 thickened self-sealing bag and treated with 6 kGy electron beam irradiation for 1 min.

[0067] The five groups of treated samples were stored at 15±1 ℃, and sensory evaluation and total bacterial count were performed. The experimental results are shown in Table 7.

[0068] Table 7. Effects of UV, spice, irradiation, and combined treatments on total bacterial count in fresh dried bean curd sticks.

[0069]

[0070] As shown in Table 7, with the extension of storage time, the total number of colonies in the control group increased significantly. Among the three single treatment groups (UV treatment group, compound extract treatment group, and irradiation treatment group), the irradiation treatment had the best effect, followed by the compound extract and UV treatment. Compared with the control group, although all three treatment methods reduced the number of microorganisms, the effect was significantly lower than that of the compound treatment group. After 10 days of storage at room temperature, the total number of colonies in the compound treatment group was only 4.50 lg cfu / g.

[0071] From the perspective of sensory evaluation scores ( Figure 5 The control group scored only 40.27 points on day 5, having lost its commercial value, while the combined treatment group still had a higher sensory evaluation score of 62.39 points on day 5, and still possessed commercial value.

[0072] Regarding the relationship between total bacterial count and shelf life, since there is currently no standard for the total bacterial count of dried bean curd sticks, especially fresh dried bean curd sticks, the agricultural industry standard NY / T 1052-2014 "Green Food Soy Products" sets the limit for total bacterial count of bulk soy products at 1.0 × 10⁻⁶. 5 The limit for cfu / g in pre-packaged soy products is 7.5 × 10⁻⁶. 2 cfu / g; Hubei Provincial Local Standard DB 42 / 255-2003 "Soy Products" sets the upper limit for total bacterial count in pre-packaged, non-fermented soy products at 1.0 × 10⁻⁶ cfu / g. 5 CFU / g; Zhejiang Provincial Local Standard DB 33 / 529-2005 "Quality and Safety Requirements for Bulk and Prepackaged Bean Products" sets the upper limit for bacterial colonies in non-ready-to-eat prepackaged bean products and gluten products at 1.0 × 10⁻⁶. 5 The upper limit of bacterial colonies for ready-to-eat prepackaged soy products is 7.5 × 10⁻⁶ CFU / g. 2 cfu / g. However, experiments show that these standards are not suitable for fresh dried bean curd sticks, as the total bacterial count in fresh dried bean curd sticks reaches 1.0 × 10⁻⁶. 5 CFU / g does not affect the sensory quality of fresh dried bean curd sticks, but levels exceeding 1.0 × 10⁻⁶ do not. 6 CFU / g may exhibit stickiness and an unpleasant odor.

[0073] Therefore, based on the comprehensive experimental results, we believe that the combined treatment effectively inhibits the growth of microorganisms and can extend the shelf life of fresh bean curd sticks by at least 5 days. The combined treatment has the best effect on the preservation of fresh bean curd sticks.

[0074] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A physical synergistic spice sterilization and preservation method for fresh dried bean curd sticks, characterized in that, Includes the following steps: Fresh bean curd sticks were irradiated under ultraviolet light, then soaked in spice extract, and the soaked bean curd sticks were drained and treated with electron beam irradiation. The spice extract is made from the following raw materials in parts by weight: 0.1-5 parts fennel, 0.1-5 parts Sichuan pepper, 0.1-5 parts cloves, 0.1-5 parts cinnamon.

2. The physical synergistic spice sterilization and preservation method for fresh dried bean curd sticks according to claim 1, characterized in that, The ultraviolet irradiation wavelength is 254 nm, the irradiation distance is 10-50 cm, and the irradiation time is 15-60 min.

3. The physical synergistic spice sterilization and preservation method for fresh dried bean curd sticks according to claim 1, characterized in that, The mass ratio of fresh dried bean curd sticks to spice extract is 1:(1-10), the soaking temperature is 10-25 ℃, and the soaking time is 0.5-5 h.

4. The physical synergistic spice sterilization and preservation method for fresh dried bean curd sticks according to claim 1, characterized in that, The electron beam irradiation is β-ray, with a bactericidal dose of 4-10 kGy and a bactericidal time of 1-30 min.

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