A method for preparing black garlic

Abstract

This application provides an efficient method for preparing black garlic, comprising: (1) peeling and washing the garlic; (2) soaking the garlic in a seaweed extract solution; (3) pre-treating the garlic at low temperature; (4) subjecting the garlic to high temperature and high humidity; and (5) drying the garlic. The method can maintain the content of sulfur-containing compounds such as alliin during the browning process and produce melanoidins with enhanced antioxidant properties.

Description

Field of the Invention

[0001] The present application relates to the field of food, and specifically, provides a method for preparing black garlic. Background Art

[0002] Black garlic is a common processed garlic food in East Asian countries such as China and South Korea. Made from garlic, black garlic is produced through fermentation or the Maillard reaction under high temperature and humidity. It is rich in protein, amino acids, polysaccharides, and trace elements. Chinese research has shown that the polyphenols and polysaccharides in black garlic can provide significant antioxidant benefits. Alliin compounds, such as alliin and deoxyalliin, have demonstrated anti-tumor and immune-modulating effects.

[0003] Melanoidins are a class of nitrogen-containing macromolecular compounds with varying structures, molecular weights, and compositions, produced by the Maillard reaction during food processing. In addition to affecting food color and flavor, melanoidins also have antioxidant and immune-enhancing properties.

[0004] The preparation process of black garlic is time-consuming, during which the content of various active ingredients and the physical properties of the product are constantly changing. Balancing various indicators and quickly obtaining black garlic products with balanced properties in all aspects is an important research direction in this field. Summary of the Invention

[0005] To address the above issues, the applicant attempted to introduce a small amount of red algae extract by soaking, and to influence the Maillard reaction through the various phycobiliproteins and sulfated polysaccharides contained in the red algae, thereby improving the nutritional / health-promoting components of black garlic products.

[0006] In one aspect, the present application provides a method for preparing black garlic, comprising:

[0007] (1) Cut off the stem of the garlic, peel off the outermost 1-2 layers of skin, and wash to obtain washed garlic;

[0008] (2) soaking the washed garlic obtained in step (1) in a seaweed extract solution for 10-30 minutes to obtain soaked garlic;

[0009] (3) freezing the soaked garlic obtained in step (2) for 18-36 hours to obtain low-temperature pretreated garlic;

[0010] (4) treating the garlic obtained from the low-temperature pretreatment in step (3) at a temperature of 70-75° C. and a humidity of 70-80% for 11-13 days;

[0011] (5) Drying.

[0012] Furthermore, the seaweed extract solution in step (2) is a 1-3% w / v red algae extract solution.

[0013] Furthermore, the preparation method of the red algae extract is:

[0014] (A) Add red algae to water 3-5 times the mass of the red algae and perform freeze-thaw cycles 2-3 times to obtain a freeze-thaw mixture;

[0015] (B) filtering and centrifuging the freeze-thaw mixture obtained in step (A) to remove residual algae and impurities to obtain an extract;

[0016] (C) Concentrating and freeze-drying the extract obtained in step (B) to obtain a red algae extract.

[0017] Furthermore, the red algae is Porphyra yezoensis ( Porphyra yezoensis ) or Gracilaria ( Gracilaria sjoestedtii ).

[0018] Furthermore, in step (2), the washed garlic obtained in step (1) is soaked in a 2% w / v red algae extract solution for 20 minutes.

[0019] Furthermore, in step (3), the soaked garlic obtained in step (2) is frozen for 24 hours.

[0020] Furthermore, in step (4), the low-temperature pretreated garlic obtained in step (3) is subjected to high temperature and high humidity treatment at 70°C and 75°C for 13 days;

[0021] Furthermore, in step (5), the drying is performed until the moisture content is less than 45%.

[0022] Furthermore, the method also includes (6) sterilization and packaging.

[0023] On the other hand, the present application provides a black garlic product prepared using the above method.

[0024] On the other hand, the present application provides a melanoidin component extracted from the above-mentioned black garlic product.

[0025] Furthermore, the extraction method of the above-mentioned melanoidin component includes: peeling black garlic; adding it to a 20-30% ethanol solution at a solid-liquid ratio of 1:15-30 g:mL and mixing evenly; stirring and extracting in a 40-50°C water bath for 40-60 minutes; extracting 2-3 times and combining the extracts; filtering, concentrating and then freeze-drying.

[0026] On the other hand, the present application provides the use of the above-mentioned melanoidin component in the preparation of health products with antioxidant and / or immune-enhancing effects.

[0027] In addition to the Cangshan garlic material used in the examples, based on the similarity of the basic components of garlic, the method of the present application can be used for various garlic varieties after appropriate changes, including but not limited to Soviet garlic, soft leaf garlic, Puning garlic, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the changing trend of reducing sugar and total phenols in black garlic during high temperature and high humidity treatment.

[0029] Figure 2 This is the changing trend of sulfur compounds in black garlic during high temperature and high humidity treatment.

[0030] Figure 3 This is the trend of browning degree change of black garlic during high temperature and high humidity treatment. DETAILED DESCRIPTION

[0031] Example 1 Basic preparation method of black garlic

[0032] Cangshan garlic harvested from the same planting enterprise in Shandong during the same period was selected as the raw material (the quality grade used in each group of experiments was the same).

[0033] (1) Cut off the stem of the garlic, peel off the outer 1-2 layers of skin, and wash;

[0034] (2) freezing the washed garlic obtained in step (1) for 24 hours to obtain low-temperature pretreated garlic;

[0035] (3) treating the garlic obtained from step (2) at a high temperature and high humidity at 70° C. and 75% humidity;

[0036] (4) Dry until the product moisture content is about 45%.

[0037] Detection of total phenols, alliin, deoxyalliin and γ-glutamylcysteine:

[0038] Chop different cloves from the batch of black garlic to be tested. Accurately weigh 15 g of sample and add it to 100 mL of water containing 10% methanol. Crush the sample in a food processor. Ultrasonic extraction is performed at room temperature for 30 minutes. Filter the filtrate, centrifuge it, and dilute it to 200 mL to prepare the black garlic extract sample for the detection of total phenols, alliin, deoxyalliin, and γ-glutamylcysteine.

[0039] Analyses were performed on an LC-20A chromatograph (Shimadzu) using a C18 column (Venusil MP C18). The mobile phase consisted of methanol and 0.1% phosphoric acid in a 1:9 volume ratio, with detection at 220 nm. Standard solutions were prepared using alliin, deoxyalliin, and γ-glutamylcysteine ​​standards purchased from Shanghai Shidande, and a calibration curve was plotted. The average value of three replicate samples was used.

[0040] Total phenolics were determined using the Folin-Ciocalteu method: 1 mL of sample was mixed with 1 mL of Folin-Ciocalteu reagent and 3 mL of 20% Na₂CO₃. The mixture was incubated in a 50°C water bath for 30 minutes. The absorbance at 765 nm was measured. A standard solution was prepared using gallic acid, and a standard curve was plotted. The average value of three replicate samples was used.

[0041] Detection of reducing sugar:

[0042] Take different cloves from the batch of black garlic to be tested and chop them; accurately weigh 10g of sample and add it to 100mL of water; grind it in a food processor; extract it in boiling water for 30 minutes; centrifuge it and collect the supernatant; take 10mL of the supernatant and dilute it to 200mL as the black garlic extract sample for reducing sugar detection.

[0043] DNS method: Mix 1 mL of sample with 1 mL of DNS solution; react in a boiling water bath for 3 minutes. After cooling, dilute to volume and measure absorbance at 540 nm. Prepare a standard solution with glucose and plot a standard curve. Measure the average of three replicates.

[0044] Browning degree determination

[0045] Use Trixon Colorimeter (TS8290) to test L, a, and b values ​​(average value of the cross-section of 5 random garlic cloves):

[0046] Browning degree = [(L 样品 -L 标准 ) 2 +(a 样品 -a 标准 ) 2 +(b 样品 -b 标准 ) 2 ] 1 / 2

[0047] The test results showed that reducing sugar and total phenols were basically stable on the 10th to 12th day of high temperature and high humidity treatment, with no significant changes ( Figure 1 ); Regarding sulfur-containing compounds, although the level of γ-glutamylcysteine ​​maintained a significant increase for about the first 13 days, alliin and deoxyalliin, which have relatively clear health benefits (the biological / health benefits of γ-glutamylcysteine ​​are far less than those of alliin and deoxyalliin), peaked on the 5th to 7th day and then declined by more than 20% ( Figure 2 ); combined with the change in browning degree ( Figure 3 ), in order to achieve ideal quality in terms of browning degree (one of the most important appearance qualities of black garlic), reducing sugar and total phenols, high temperature and high humidity treatment is required for more than 13 days, at least more than 10 days, but at this time the content of alliin and deoxyalliin will inevitably be lost.

[0048] Example 2 Effect of soaking with red algae extract

[0049] The Korean food industry is abuzz with research on the use of laver and black garlic in food and condiments. The applicant attempted to use a red algae extract containing various phycobiliproteins (red algae contain erythrophycocyanin, allophycocyanin, and phycocyanin) and sulfated polysaccharides to influence the Maillard reaction, accelerating the browning process and altering the content of sulfur compounds in the black garlic product and the efficacy of the Maillard reaction products.

[0050] The red algae used are Porphyra yezoensis, Agar-agar, Gracilaria lemaneiformis, and Eucheuma chinensis, all of which are purchased from breeding enterprises. In order to distinguish similar red algae species such as Porphyra hainanensis and Gracilaria euphorbia, manual control identification and sorting are used to ensure that the raw materials are Porphyra yezoensis 、 Gelidium amansii 、 Gracilaria sjoestedtii 、 Eucheuma denticulatum The manually identified raw materials were drained, chopped, and frozen for later use. The same batch of red algae raw materials were used in the experiment.

[0051] Preparation method of red algae extract:

[0052] Frozen red algae were added into water with 4 times its mass, thawed in a 30°C water bath, frozen at -20°C, and then thawed in a 30°C water bath to obtain a dark red mixture; the obtained mixture was stirred at low speed at room temperature overnight; filtered with gauze and centrifuged to remove residual algae; the solution was partially rotary evaporated and freeze-dried to obtain the red algae water extract.

[0053] The protein content and total sugar content of several red algae extracts were determined by Kjeldahl nitrogen determination and sulfuric acid-phenol method. The results are shown in Table 1:

[0054] Table 1 Protein content and total sugar content of several red algae extracts

[0055]

[0056] The protein content in Porphyra yezoensis is higher than that in Gelidium agar-agar, Gracilaria lemaneiformis and Eucheuma in comparison with that in Gelidium tataricum.

[0057] Before freezing, the washed garlic was soaked in a 2% w / v red algae extract solution for 20 minutes, and then frozen and subjected to high temperature and high humidity treatment according to the method in Example 1 to prepare black garlic products. In terms of total phenols, reducing sugars and browning degree, the change trends in Example 1 were basically maintained. In terms of alliin and deoxyalliin, as shown in Figure 1, Figure 4 As shown in the results, among the four red algae extracts, soaking in Porphyra yezoensis extract and Gracilaria lemaneiformis extract produced a significant protective effect on the two. The total content did not decrease significantly after the 7th day, but instead showed a slight upward trend between the 9th and 13th days, while Gelidium amanita and Eucheuma were basically unaffected. Therefore, this effect may depend on the combination of specific sulfur-containing phycobiliproteins and sulfated polysaccharides, especially the type of polysaccharides.

[0058] The applicant subsequently verified the effects of other concentrations of Porphyra yezoensis extract and Gracilaria lemaneiformis extract, and the results showed that concentrations of 1-5% could achieve similar effects (the fishy smell caused by too high a concentration may affect the flavor of the product).

[0059] Example 3 Extraction and Effect of Black Garlic Melanin-like Components

[0060] According to the general understanding in the field of food processing and health care products, the production and properties of melanoidins are mainly affected by the substrate of the Maillard reaction:

[0061] Melanoidin extraction method:

[0062] Melanoidins were extracted from black garlic using an ethanol extraction method: peel the black garlic; mix thoroughly with a 20% ethanol solution at a solid-liquid ratio of 1:20 (g / mL); stir in a 40°C waterbath for 60 minutes; combine the two extracts; filter, concentrate, and freeze-dry. The yield was calculated based on the weight of the peeled black garlic. Three replicate samples were tested.

[0063] Melanoidin antioxidant effect test:

[0064] Melanoidin components were prepared into a 0.05% w / v solution as the test sample. DPPH free radical scavenging rate was determined using a commercially available kit: 2.5 mL of the liquid sample was mixed with 2.5 mL of DPPH anhydrous ethanol solution (reaction solution) or 2.5 mL of anhydrous ethanol (control reaction solution). The reaction was incubated at 25°C in the dark for 30 minutes. The absorbance of the reaction solution, control reaction solution, and reference solution (2.5 mL of anhydrous ethanol plus 2.5 mL of DPPH anhydrous ethanol solution) was measured spectrophotometrically at 519 nm.

[0065] DPPH free radical scavenging rate = (1-(A 反应液 -A 对照反应液 ) / A 参比液 ) × 100%; the average value was taken from three experiments.

[0066] Macrophage proliferation activity assay:

[0067] Mouse mononuclear macrophage RAW264.7 cells were purchased from Sean Biosciences to verify the immune-enhancing activity of melanoidin.

[0068] The cells were cultured in serum-containing DMEM medium until the logarithmic growth phase; 1×10 5Cells (100 μl) were cultured at 37°C for 2 hours to allow them to adhere, and the culture medium was aspirated. 100 μl of DMEM culture medium containing 0.05 mg / mL melanoidin and serum was added. Serum-free DMEM culture medium without melanoidin was used as a control (100% standard). The cells were cultured at 37°C for 24 hours in an atmosphere of 5% carbon dioxide.

[0069] Add 10 μL of 5 mg / mL MTT working solution and continue culturing for 4 hours; discard the culture medium, wash and add 150 μL of DMSO solution, shake for 15 minutes, and measure the 570 nm OD value (preliminary actual counting tests have shown that the low concentration of melanoidin used has no significant effect on OD570 detection of cell density); average the three parallel groups.

[0070] The method of Example 1 was used to verify the black garlic product treated with high temperature and high humidity for 15 days, as well as the black garlic product treated with high temperature and high humidity for 13 days after being soaked in Porphyra yezoensis extract and Gracilaria lemaneiformis extract in Example 2. The results are shown in Table 2:

[0071] Table 2 The yield of black garlic melanin-like components and their antioxidant and immune-enhancing effects

[0072]

[0073] The results showed that soaking in Porphyra yezoensis and Gracilaria lemaneiformis extracts had no significant effect on the yield of melanoidins, but significantly improved their antioxidant and immune-enhancing effects, with the Gracilaria lemaneiformis extract soaking providing the most significant improvement. This provides a promising foundation for the preparation of health supplements based on melanoidin extracts.

Claims

1. A method for preparing black garlic, characterized in that, The method comprises: (1) cutting off the stem of garlic, peeling off the outermost 1-2 layers of skin, and washing to obtain washed garlic; (2) soaking the washed garlic obtained in step (1) in a seaweed extract solution for 10-30 minutes to obtain soaked garlic; (3) freezing the soaked garlic obtained in step (2) for 18-36 hours to obtain low-temperature pretreated garlic; (4) treating the low-temperature pretreated garlic obtained in step (3) at 70° C. and 75% humidity for 13 days; (5) Drying; The seaweed extract solution in step (2) is a 1-3% w / v red algae extract solution; the red algae is Gracilaria lemaneiformis; and the preparation method of the red algae extract is: (A) adding red algae to water 3-5 times the mass of the red algae and performing a freeze-thaw cycle 2-3 times to obtain a freeze-thaw mixture; (B) filtering and centrifuging the freeze-thaw mixture obtained in step (A) to remove residual algae and impurities to obtain an extract; (C) concentrating and freeze-drying the extract obtained in step (B) to obtain a red algae extract.

2. The method according to claim 1, wherein in step (2), the washed garlic obtained in step (1) is soaked in a 2% w / v seaweed extract solution for 20 minutes.

3. The method according to claim 1, wherein the soaked garlic obtained in step (2) is frozen for 24 hours in step (3).

4. The method according to claim 1, wherein the drying step (5) is performed until the moisture content is lower than 45%.

5. The method according to claim 1, further comprising (6) sterilization and packaging.

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