Method for reducing content of volatile odor compounds in malus micromalus fruit juice

Abstract

The invention discloses a method for reducing the content of volatile odor compounds in malus micromalus fruit juice, and belongs to the technical field of fruit juice processing. The method comprises the following steps: (1) cleaning and crushing malus micromalus to obtain malus micromalus pulp; (2) adjusting the pH value of the malus micromalus makino pulp to 1.0-3.0, freezing, unfreezing, and then heating and stirring at 50-60 DEG C for 10-60 minutes to obtain treated malus micromalus makino pulp; (3) directly filtering the treated malus micromalus pulp, and discarding first pomace to obtain malus micromalus normal juice; and (4) adjusting the pH value of the malus micromalus fruit juice to 3.5-4.5, centrifuging, removing second pomace, and homogenizing and instantaneously sterilizing the clear liquid to obtain the malus micromalus fruit juice. According to the method disclosed by the invention, the content of volatile odor compounds such as 2-amyl furan, 1-octylene-3-ketone, trans-2-decenal and trans-2, 4-decadienal in the malus micromalus fruit juice can be effectively reduced, and the whole flavor of the malus micromalus fruit juice is not obviously influenced.

Description

Technical Field

[0001] This invention relates to a method for reducing the content of volatile off-flavor compounds in sea buckthorn juice, belonging to the field of juice processing technology. Background Technology

[0002] Sea buckthorn is a nutritious fruit with both edible and medicinal properties. It is an important local specialty and a symbol of "longevity," possessing high processing value. Sea buckthorn is rich in various minerals, especially calcium, earning it the title of "King of Calcium Fruits." Every 100 grams of sea buckthorn fruit contains up to 66.59 milligrams of calcium, playing a vital role in maintaining bone health and preventing osteoporosis, making it particularly suitable for infants and the elderly. Sea buckthorn also contains a considerable amount of vitamins, especially vitamin C, vitamin B1, vitamin B2, and carotene. These vitamins are essential for maintaining normal metabolism and physiological functions. Furthermore, sea buckthorn is rich in organic acids and polysaccharides, which can protect the liver, act as antioxidants, scavenge free radicals, and relieve indigestion.

[0003] There are many types of deep-processed products made from sea buckthorn, including more than 40 kinds such as fruit wine, fruit juice beverages, dried fruit, fruit vinegar, and jam. Among them, fruit juice beverages have the greatest market development potential. As a specialty beverage with unique flavor and health benefits, sea buckthorn juice is gradually gaining popularity. If the issue of universal taste appeal can be resolved, its market potential should not be underestimated.

[0004] The flavor of fruit juice is one of the core elements that attracts consumers. It is mainly composed of volatile flavor compounds, including aldehydes, alcohols, esters, terpenes, ketones, sulfur-containing compounds, furans, and acids. These volatile flavor compounds are diverse. Based on consumer sensory acceptance and their positive or negative contribution to the overall flavor profile of the fruit juice, compounds that directly contribute positive sensory attributes such as the juice's uniqueness, appeal, freshness, ripeness, sweetness, and crispness are classified as pleasant flavor compounds. Compounds that contribute unpleasant odors (off-flavors, foul smells), making the juice smell or taste stale, spoiled, oxidized, or overcooked, leading to a decline in juice quality and consumer rejection, are classified as unpleasant flavor compounds, generally referred to as off-flavor compounds.

[0005] According to the literature (Yang Chun, Li Lili, Lin Qinbao, et al. Gas chromatography-mass spectrometry analysis of aroma components of sea buckthorn [J]. Food Science, 2009, 30(20): 285-287.), there are more than 60 volatile flavor compounds in sea buckthorn, mainly aldehydes, alcohols, esters, ketones, alkenes and alkanes. 2-Pentylfuran (green bean flavor, butter flavor, metallic flavor), 1-octen-3-one (metallic flavor, mushroom flavor, earthy flavor), trans-2-decenal (stale oil flavor, cardboard flavor), and trans,trans-2,4-decadienal (fried flavor, oil flavor) are typical volatile off-flavor compounds in fruit juice, and because they have low threshold values, they contribute significantly to the off-flavor of the juice. Reducing the content of these volatile off-flavor compounds is crucial for the quality control, flavor improvement and new product development of sea buckthorn juice.

[0006] Existing publicly available technologies primarily focus on the retention and enhancement of flavor compounds during fruit juice processing, as well as the inhibition and masking of off-flavor compounds. These technologies mainly cover the following aspects:

[0007] (1) Employ vacuum or cold-press juicing techniques to reduce the loss of heat-sensitive aromas; use non-thermal sterilization or high-temperature instantaneous sterilization instead of traditional heat sterilization to minimize the loss of "cooked" flavors and volatile aromas. For example:

[0008] CN119488132A discloses a process for preparing ultra-high pressure organic sea buckthorn juice, which preserves the nutritional components and flavor of sea buckthorn to the maximum extent by freezing, sterilizing, rinsing, crushing, vacuum cold soaking and juicing, and ultra-high pressure sterilization of sea buckthorn.

[0009] CN114794333A discloses a method for improving the loss of flavor in fruit juice by mixing fruit juice with pectin to obtain a mixture; subjecting the mixture to high static pressure treatment can effectively improve the loss and evaporation of flavor during fruit juice processing and shelf life.

[0010] (2) Precise enzymatic hydrolysis technology is used to release flavor precursors, avoid off-flavors, and enhance the characteristic flavor of the juice. For example:

[0011] CN103829345B discloses a method for increasing volatile components in citrus juice. The method involves juicing citrus fruits, adding naringinase, hydrolyzing at a constant temperature, heating the reaction, and then naturally cooling the juice. This process transforms naturally occurring flavor precursors in citrus juice into volatile flavor components, resulting in a significantly enhanced flavor in the prepared citrus juice.

[0012] (3) By adding natural antioxidants and flavor masking agents, off-odors produced by oxidation during processing can be suppressed or masked. For example:

[0013] CN102495147B discloses a method for detecting and improving the main undesirable flavors of bayberry juice. The method uses solid-phase microextraction and gas chromatography-mass spectrometry to analyze the cooked, spoiled, and fermented flavors in bayberry juice. Then, the flavors are improved by adding other fruit juices, β-cyclodextrin, ethyl maltol, and glucose oxidase through sterilization processes.

[0014] CN116965501A discloses a formula and method for slowing down the flavor degradation of lemon juice by combining flavor antioxidants. By taking whole lemon juice with peel and using the combined synergistic effect of different antioxidants, an effective formula for slowing down the flavor degradation of lemon juice was selected.

[0015] However, there are currently no reports on how to selectively reduce the content of volatile off-flavor compounds in sea buckthorn juice without significantly affecting its overall flavor. Summary of the Invention

[0016] [Technical Issues]

[0017] Existing processing technologies cannot selectively reduce the content of volatile off-flavor compounds in sea buckthorn juice without significantly affecting its overall flavor.

[0018] [Technical Solution]

[0019] To address the aforementioned problems, this invention provides a method for reducing the content of volatile off-flavor compounds in sea buckthorn juice. Specifically, the invention first washes and crushes the sea buckthorn fruits to obtain sea buckthorn pulp; then, it adjusts the pH of the pulp, freezes, thaws, and heat-treats; subsequently, it is directly filtered, discarding the first pulp residue to obtain sea buckthorn juice; the pH is then adjusted, centrifuged, and the second pulp residue is removed; the clarified liquid is homogenized and briefly sterilized to obtain sea buckthorn juice. This method can selectively reduce the content of volatile off-flavor compounds in sea buckthorn juice without significantly affecting its overall flavor.

[0020] The first objective of this invention is to provide a method for reducing the content of volatile off-flavor compounds in sea buckthorn juice without significantly affecting its overall flavor, comprising the following steps:

[0021] (1) Wash and crush the sea buckthorn fruit to obtain sea buckthorn pulp;

[0022] (2) Adjust the pH of the sea buckthorn pulp to 1.0 to 3.0, freeze it at -20 to -5℃ for 6 to 14 hours, take it out and thaw it, and then heat and stir it at 50 to 60℃ for 10 to 60 minutes to obtain the treated sea buckthorn pulp;

[0023] (3) Filter the processed sea buckthorn pulp directly, discard the first pulp, and obtain sea buckthorn juice;

[0024] (4) Adjust the pH of the original juice of sea buckthorn to 3.5-4.5, centrifuge, remove the second pulp, homogenize and sterilize the clear liquid to obtain sea buckthorn juice.

[0025] In one embodiment of the present invention, the particle size of the crushed sea buckthorn fruit in step (1) is 3-5 mm.

[0026] In one embodiment of the present invention, the solution used to adjust the pH in step (2) is an aqueous solution of citric acid with a concentration of 0.1 to 0.5 mol / L, more preferably 0.3 mol / L.

[0027] In one embodiment of the present invention, the pH is adjusted to 2.0 in step (2); freezing is performed at -18°C for 8 hours.

[0028] In one embodiment of the present invention, the thawing in step (2) is natural thawing at 20-30°C (room temperature).

[0029] In one embodiment of the present invention, the heating and stirring in step (2) is carried out in a water bath; the heating and stirring is carried out at 45-55°C and 100-500 rpm for 20-40 minutes, and more preferably at 50°C and 200 rpm for 30 minutes.

[0030] In one embodiment of the present invention, the solution used to adjust the pH in step (4) is an aqueous solution of sodium bicarbonate with a concentration of 0.01 to 0.1 mol / L, more preferably 0.05 mol / L.

[0031] In one embodiment of the present invention, the pH is adjusted to 4.0 in step (4).

[0032] In one embodiment of the present invention, the centrifugation in step (4) is performed at 3000-8000g for 5-30 minutes, and more preferably at 5000g for 15 minutes.

[0033] In one embodiment of the present invention, the homogenization pressure in step (4) is 20-50 MPa, and is further optimized to 30 MPa.

[0034] In one embodiment of the present invention, the instantaneous sterilization in step (4) is maintained at 105-110°C for 4-6 seconds, and more preferably at 108°C for 5 seconds.

[0035] The second objective of this invention is to prepare sea buckthorn juice using the method described herein.

[0036] A third objective of this invention is to provide a method for selectively reducing the content of 2-pentylfuran, 1-octen-3-one, trans-2-decenal, and trans,trans-2,4-decadienal in sea buckthorn juice, comprising the following steps:

[0037] (1) Wash and crush the sea buckthorn fruit to obtain sea buckthorn pulp;

[0038] (2) Adjust the pH of the sea buckthorn pulp to 1.0 to 3.0, freeze it at -20 to -5℃ for 6 to 14 hours, take it out and thaw it, and then heat and stir it at 50 to 60℃ for 10 to 60 minutes to obtain the treated sea buckthorn pulp;

[0039] (3) Filter the processed sea buckthorn pulp directly, discard the first pulp, and obtain sea buckthorn juice;

[0040] (4) Adjust the pH of the original juice of sea buckthorn to 3.5-4.5, centrifuge, remove the second pulp, homogenize and sterilize the clear liquid to obtain sea buckthorn juice.

[0041] The fourth objective of this invention is to provide a method for processing fruit wine, wherein the method first uses the method described in this invention to reduce the content of volatile off-flavor compounds in sea buckthorn juice without significantly affecting its overall flavor to prepare sea buckthorn juice, and then ferments it into sea buckthorn wine.

[0042] [Beneficial Effects]

[0043] (1) Compared with the prior art, the method of the present invention can selectively reduce the content of volatile off-flavor compounds in sea buckthorn juice, thereby significantly improving the flavor of sea buckthorn juice.

[0044] (2) The method of the present invention can effectively reduce the content of volatile odor compounds such as 2-pentylfuran, 1-octen-3-one, trans-2-decenal and trans, trans-2,4-decadienal in sea buckthorn juice, with reduction ratios of 45.11%, 51.37%, 60.95% and 63.28%, respectively. Attached Figure Description

[0045] Figure 1 The effect of freezing pH on the content of volatile off-flavor compounds in sea buckthorn juice in Example 2; wherein, (a) is 2-pentylfuran; (b) is 1-octen-3-one; (c) is trans-2-decenal; and (d) is trans,trans-2,4-decadienal.

[0046] Figure 2 The effect of heating temperature on the content of volatile off-flavor compounds in sea buckthorn juice in Example 3; wherein, (a) is 2-pentylfuran; (b) is 1-octen-3-one; (c) is trans-2-decenal; and (d) is trans,trans-2,4-decadienal. Detailed Implementation

[0047] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0048] Test method:

[0049] Determination of volatile compound content in fruit juice:

[0050] Headspace solid-phase microextraction-gas chromatography-olfactometry-mass spectrometry (HS-SPME / GC-MS) was used to analyze volatile compounds in the samples. SPME was employed for extraction of volatile compounds from the samples. 5.00 mL of fruit juice sample was placed in a 15.00 mL vial with a Teflon-coated rubber diaphragm on the cap. Simultaneously, 20 μL of 2-heptanone (20 μg / mL) was added as an internal standard. The sample in the vial was first placed in a stirred 50 °C water bath for 10 min, and then continuously adsorbed at 50 °C for 30 min using an extraction head (model 50 / 30 μm DVB / CAR on PDMS). After extraction, the extraction head was desorbed at 250 °C for 5 min. The volatile compounds were then separated using a Stabilwax-MS capillary column (30 m × 0.25 mm id, 0.25 μm).

[0051] The oven temperature program was set as follows: initial temperature was maintained at 40℃ for 3 min, then increased to 230℃ at a rate of 10℃ / min and maintained for 6 min. The helium flow rate as carrier gas was 1.0 mL / min. The gaseous distillate was fed into the MS, and mass spectrometry fragment detection was performed in electron collision (EI) mode (ionization energy 70 eV) and a full scan range of 33–400 m / z. Volatile compounds were qualitatively analyzed using the MS database (NIST 2017 mass spectrometry database), linear retention indices (LRIs), and mass spectrometry deconvolution. Quantitative data were obtained by measuring the area under the total ion current (TIC) peak, and the relative amounts of volatile compounds were calculated using the internal standard 2-heptanone.

[0052]

[0053] Note: The unit for volatile compound content is μg / kg.

[0054] In the examples and comparative examples, room temperature refers to 20–30°C; solutions for which the solvent is not specifically specified use deionized water; and operations for which the temperature is not specifically specified refer to room temperature.

[0055] Example 1

[0056] A method for reducing the content of volatile off-flavor compounds in sea buckthorn juice without significantly affecting its overall flavor includes the following steps:

[0057] (1) Wash the sea buckthorn fruit and crush it to a particle size of 3-5 mm to obtain sea buckthorn pulp;

[0058] (2) The pH of the sea buckthorn pulp was adjusted to 2.0 with 0.3 mol / L citric acid aqueous solution, frozen at -18℃ for 8 h, taken out and thawed at room temperature, and then heated and stirred at 50℃ for 30 min to obtain the treated sea buckthorn pulp;

[0059] (3) Filter the processed sea buckthorn pulp directly, discard the first pulp, and obtain sea buckthorn juice;

[0060] (4) Adjust the pH of the sea buckthorn juice to 4.0 with 0.05 mol / L sodium bicarbonate aqueous solution, centrifuge at 5000g for 15 min to remove the second fruit residue, homogenize the clear liquid (pressure 30 MPa) and sterilize it briefly (108℃, 5s) to obtain sea buckthorn juice.

[0061] Comparative Example 1

[0062] The standard processing technology for sea buckthorn juice is as follows:

[0063] (1) Wash the sea buckthorn fruit and crush it to a particle size of 3-5 mm to obtain sea buckthorn pulp;

[0064] (2) Filter the sea buckthorn pulp directly, discard the first pulp, and obtain the original sea buckthorn juice;

[0065] (3) Centrifuge the original juice of sea buckthorn fruit at 5000g for 15min to remove the second fruit residue. Homogenize the clear liquid (pressure 30MPa) and sterilize it briefly (108℃, 5s) to obtain sea buckthorn juice.

[0066] The volatile components of the sea buckthorn juice obtained in Example 1 and Comparative Example 1 were tested, and the results are as follows:

[0067] As shown in Table 1, the content of major volatile off-odor compounds in the sea buckthorn juice of Example 1 was significantly lower than that of Comparative Example 1. Compared with Comparative Example 1, the reduction rates of 2-pentylfuran, 1-octen-3-one, trans-2-decenal, and trans,trans-2,4-decadienal in the sea buckthorn juice of Example 1 were 45.11%, 51.37%, 60.95%, and 63.28%, respectively.

[0068] Table 1

[0069]

[0070] As shown in Table 2, compared with Comparative Example 1, the content of total volatile compounds in the sea buckthorn juice of Example 1 was not significantly reduced, remaining at 95.63% of that in Comparative Example 1. The contents of aldehydes, alcohols, and esters, which are the main volatile components, in the sea buckthorn juice of Example 1 were 90.07%, 93.15%, and 96.89%, respectively, compared to Comparative Example 1.

[0071] Table 2

[0072]

[0073] Comparative Example 2: Effect of non-freezing on the content of volatile off-flavor compounds in sea buckthorn juice

[0074] A processing method for sea buckthorn juice includes the following steps:

[0075] (1) Wash the sea buckthorn fruit and crush it to a particle size of 3-5 mm to obtain sea buckthorn pulp;

[0076] (2) Filter the sea buckthorn pulp directly, discard the first pulp, and obtain the original sea buckthorn juice;

[0077] (3) The pH of the sea buckthorn juice was adjusted to 2.0 with a 0.3 mol / L citric acid aqueous solution, and then heated and stirred at 50℃ for 30 min; the pH of the sea buckthorn juice was adjusted to 4.0 with a 0.05 mol / L sodium bicarbonate aqueous solution, centrifuged at 5000g for 15 min, the second pulp was removed, and the clear liquid was homogenized (pressure 30 MPa) and briefly sterilized (108℃, 5s) to obtain sea buckthorn juice. Comparative Example 3: Effect of non-freezing on the content of volatile off-flavor compounds in sea buckthorn juice.

[0078] A processing method for sea buckthorn juice includes the following steps:

[0079] (1) Wash the sea buckthorn fruit and crush it to a particle size of 3-5 mm to obtain sea buckthorn pulp;

[0080] (2) The pH of the sea buckthorn pulp was adjusted to 2.0 with 0.3 mol / L citric acid aqueous solution, and then heated and stirred at 50°C for 30 min to obtain the treated sea buckthorn pulp;

[0081] (3) Filter the processed sea buckthorn pulp directly, discard the first pulp, and obtain sea buckthorn juice;

[0082] (4) The pH of the sea buckthorn juice was adjusted to 4.0 with a 0.05 mol / L sodium bicarbonate aqueous solution. The mixture was centrifuged at 5000g for 15 min to remove the second pulp. The supernatant was homogenized (pressure 30 MPa) and briefly sterilized (108℃, 5 s) to obtain sea buckthorn juice. Comparative Example 4: Effect of filtration followed by freezing on the content of volatile off-flavor compounds in sea buckthorn juice.

[0083] A processing method for sea buckthorn juice includes the following steps:

[0084] (1) Wash the sea buckthorn fruit and crush it to a particle size of 3-5 mm to obtain sea buckthorn pulp;

[0085] (2) Filter the sea buckthorn pulp directly, discard the first pulp, and obtain the original sea buckthorn juice;

[0086] (3) Adjust the pH of the sea buckthorn juice to 2.0 with 0.3 mol / L citric acid aqueous solution, freeze at -18℃ for 8 h, take it out and thaw at room temperature, and then heat and stir at 50℃ for 30 min; adjust the pH of the sea buckthorn juice to 4.0 with 0.05 mol / L sodium bicarbonate aqueous solution, centrifuge at 5000g for 15 min, remove the second fruit residue, homogenize the clear liquid (pressure 30 MPa) and sterilize it briefly (108℃, 5s) to obtain sea buckthorn juice.

[0087] Comparative Example 5: Effect of filtration followed by freezing on the content of volatile off-flavor compounds in sea buckthorn juice

[0088] A processing method for sea buckthorn juice includes the following steps:

[0089] (1) Wash the sea buckthorn fruit and crush it to a particle size of 3-5 mm to obtain sea buckthorn pulp;

[0090] (2) The pH of the sea buckthorn pulp was adjusted to 2.0 with 0.3 mol / L citric acid aqueous solution, and then heated and stirred at 50°C for 30 min to obtain the treated sea buckthorn pulp;

[0091] (3) Filter the processed sea buckthorn pulp directly, discard the first pulp, freeze at -18℃ for 8 hours, take it out and thaw at room temperature to obtain sea buckthorn juice;

[0092] (4) The pH of the sea buckthorn juice was adjusted to 4.0 with a 0.05 mol / L sodium bicarbonate aqueous solution. The mixture was centrifuged at 5000g for 15 min to remove the second pulp. The supernatant was homogenized (pressure 30 MPa) and briefly sterilized (108℃, 5 s) to obtain sea buckthorn juice. Comparative Example 6: Effect of the order of freezing and heating on the content of volatile off-flavor compounds in sea buckthorn juice.

[0093] A processing method for sea buckthorn juice includes the following steps:

[0094] (1) Wash the sea buckthorn fruit and crush it to a particle size of 3-5 mm to obtain sea buckthorn pulp;

[0095] (2) Adjust the pH of the sea buckthorn pulp to 2.0 with 0.3 mol / L citric acid aqueous solution, heat and stir at 50℃ for 30 min, then freeze at -18℃ for 8 h, take it out and thaw at room temperature to obtain the treated sea buckthorn pulp;

[0096] (3) Filter the processed sea buckthorn pulp directly, discard the first pulp, and obtain sea buckthorn juice;

[0097] (4) The pH of the sea buckthorn juice was adjusted to 4.0 with a 0.05 mol / L sodium bicarbonate aqueous solution. The mixture was centrifuged at 5000g for 15 min to remove the second pulp. The supernatant was homogenized (pressure 30 MPa) and briefly sterilized (108℃, 5 s) to obtain sea buckthorn juice. Comparative Example 7: Effect of frozen fruit on the content of volatile off-flavor compounds in sea buckthorn juice.

[0098] A processing method for sea buckthorn juice includes the following steps:

[0099] (1) Wash the sea buckthorn fruit, freeze it at -18℃ for 8 hours, take it out and thaw it at room temperature, crush it to a particle size of 3-5 mm, and obtain sea buckthorn fruit pulp;

[0100] (2) The pH of the sea buckthorn pulp was adjusted to 2.0 with 0.3 mol / L citric acid aqueous solution, and then heated and stirred at 50°C for 30 min to obtain the treated sea buckthorn pulp.

[0101] (3) Filter the processed sea buckthorn pulp directly, discard the first pulp, and obtain sea buckthorn juice;

[0102] (4) The pH of the sea buckthorn juice was adjusted to 4.0 with a 0.05 mol / L sodium bicarbonate aqueous solution. The mixture was centrifuged at 5000g for 15 min to remove the second pulp. The supernatant was homogenized (pressure 30 MPa) and briefly sterilized (108℃, 5 s) to obtain sea buckthorn juice. Comparative Example 8: Effect of no heat treatment on the content of volatile off-flavor compounds in sea buckthorn juice.

[0103] A processing method for sea buckthorn juice includes the following steps:

[0104] (1) Wash the sea buckthorn fruit and crush it to a particle size of 3-5 mm to obtain sea buckthorn pulp;

[0105] (2) The pH of the sea buckthorn pulp was adjusted to 2.0 with 0.3 mol / L citric acid aqueous solution, frozen at -18℃ for 8 hours, and then thawed at room temperature to obtain the treated sea buckthorn pulp;

[0106] (3) Filter the processed sea buckthorn pulp directly, discard the first pulp, and obtain sea buckthorn juice;

[0107] (4) The pH of the sea buckthorn juice was adjusted to 4.0 using a 0.05 mol / L sodium bicarbonate aqueous solution. The mixture was centrifuged at 5000g for 15 min to remove the second pulp. The supernatant was then homogenized (at 30 MPa) and briefly sterilized (at 108℃ for 5 s) to obtain sea buckthorn juice. Comparative Example 9: Effect of pH Adjustment Timing on the Content of Volatile Off-Flavor Compounds in Sea Buckthorn Juice

[0108] A processing method for sea buckthorn juice includes the following steps:

[0109] (1) Wash the sea buckthorn fruit and crush it to a particle size of 3-5 mm to obtain sea buckthorn pulp;

[0110] (2) Freeze the sea buckthorn pulp at -18℃ for 8 hours, take it out and thaw it at room temperature, heat and stir it at 50℃ for 30 minutes, and then adjust the pH to 2.0 with 0.3mol / L citric acid aqueous solution to obtain the treated sea buckthorn pulp;

[0111] (3) Filter the processed sea buckthorn pulp directly, discard the first pulp, and obtain sea buckthorn juice;

[0112] (4) Adjust the pH of the sea buckthorn juice to 4.0 with 0.05 mol / L sodium bicarbonate aqueous solution, centrifuge at 5000g for 15 min to remove the second fruit residue, homogenize the clear liquid (pressure 30 MPa) and sterilize it briefly (108℃, 5s) to obtain sea buckthorn juice.

[0113] The volatile components of the sea buckthorn juices obtained in Comparative Examples 2-9 were analyzed, and the results are as follows:

[0114] Table 3

[0115]

[0116] As can be seen from Table 3, the content of the main volatile off-flavor compounds in the sea buckthorn juice obtained in Comparative Examples 2-9 is close to that in Comparative Example 1, and is much higher than that in Example 1.

[0117] Example 2: Effect of freezing pH on the content of volatile off-flavor compounds in sea buckthorn juice

[0118] (1) Wash the sea buckthorn fruit, crush it to a particle size of 3-5 mm, and obtain sea buckthorn pulp, which is divided into 7 equal portions;

[0119] (2) The pH of seven portions of sea buckthorn pulp was adjusted to 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 and 7.0 respectively using 0.3 mol / L citric acid aqueous solution or 0.05 mol / L sodium bicarbonate aqueous solution. The pulp was frozen at -18℃ for 8 hours, thawed at room temperature, and then heated and stirred at 50℃ for 30 minutes to obtain the treated sea buckthorn pulp.

[0120] (3) The processed sea buckthorn pulp was directly filtered, and the first pulp was discarded to obtain sea buckthorn juice with different frozen pH.

[0121] (4) The pH of 7 portions of sea buckthorn juice was adjusted to 4.0 by using 0.3 mol / L citric acid aqueous solution or 0.05 mol / L sodium bicarbonate aqueous solution. After centrifugation at 5000g for 15 min, the second fruit residue was removed. The clear liquid was homogenized (pressure 30 MPa) and instantaneously sterilized (108℃, 5s) to obtain sea buckthorn juice with different frozen pH.

[0122] The volatile components of the sea buckthorn juice obtained in Example 2 were tested, and the results are as follows:

[0123] from Figure 1 As shown in Table 4, lowering the pH of the fruit pulp during freezing can effectively reduce the content of off-flavor compounds such as 2-pentylfuran, 1-octen-3-one, trans-2-decenal, and trans,trans-2,4-decadienal in sea buckthorn juice. The effects of pH 2 and pH 1 are similar. With pH 2, less acid can be added, and less alkali can be added during the adjustment. Considering all factors, pH 2 is the optimal pH. However, raising the pH of the fruit pulp during freezing will actually increase the content of these off-flavor compounds.

[0124] Table 4

[0125]

[0126] Example 3: Effect of heating temperature on the content of volatile off-flavor compounds in sea buckthorn juice

[0127] (1) Wash the sea buckthorn fruit and crush it to a particle size of 3-5 mm to obtain sea buckthorn pulp;

[0128] (2) The pH of the sea buckthorn pulp was adjusted to 2.0 with 0.3 mol / L citric acid aqueous solution, and the pulp was divided into 5 equal portions. The pulp was frozen at -18℃ for 8 hours, thawed at room temperature, and then heated and stirred at 30℃, 40℃, 50℃, 60℃ and 70℃ for 30 minutes respectively to obtain the treated sea buckthorn pulp.

[0129] (3) The processed sea buckthorn pulp was directly filtered, and the first pulp was discarded to obtain sea buckthorn juice at different heating temperatures.

[0130] (4) The pH of five portions of sea buckthorn juice was adjusted to 4.0 with 0.05 mol / L sodium bicarbonate aqueous solution. After centrifugation at 5000g for 15 min, the second pulp was removed. The clear liquid was homogenized (pressure 30 MPa) and instantaneously sterilized (108℃, 5s) to obtain sea buckthorn juice with different heating temperatures.

[0131] The volatile components of the sea buckthorn juice obtained in Example 3 were tested, and the results are as follows:

[0132] from Figure 2 As shown in Table 5, freezing followed by heating of the sea buckthorn pulp can reduce the content of off-flavor compounds such as 2-pentylfuran, 1-octen-3-one, trans-2-decenal, and trans,trans-2,4-decadienal in the sea buckthorn juice. Considering all factors, a heating temperature of 50℃ is optimal.

[0133] Table 5

[0134]

[0135] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for reducing the content of volatile off-flavor compounds in sea buckthorn juice without significantly affecting its overall flavor, characterized in that, Includes the following steps: (1) Wash and crush the sea buckthorn fruit to obtain sea buckthorn pulp; (2) Adjust the pH of the sea buckthorn pulp to 1.0 to 3.0, freeze it at -20 to -5℃ for 6 to 14 hours, take it out and thaw it, and then heat and stir it at 50 to 60℃ for 10 to 60 minutes to obtain the treated sea buckthorn pulp; (3) Filter the processed sea buckthorn pulp directly, discard the first pulp, and obtain sea buckthorn juice; (4) Adjust the pH of the original juice of sea buckthorn to 3.5-4.5, centrifuge, remove the second pulp, homogenize and sterilize the clear liquid to obtain sea buckthorn juice.

2. The method according to claim 1, characterized in that, The solution used to adjust the pH in step (2) is an aqueous solution of citric acid with a concentration of 0.1 to 0.5 mol / L.

3. The method according to claim 1, characterized in that, In step (4), the solution used to adjust the pH is an aqueous solution of sodium bicarbonate with a concentration of 0.01 to 0.1 mol / L.

4. The method according to claim 1, characterized in that, In step (2), thawing is done naturally at 20-30°C.

5. The method according to claim 1, characterized in that, In step (4), centrifugation is performed at 3000-8000g for 5-30 minutes.

6. The method according to claim 1, characterized in that, In step (4), the instantaneous sterilization is carried out at 105-110℃ for 4-6 seconds.

7. The method according to claim 1, characterized in that, The homogenization pressure in step (4) is 20-50 MPa.

8. The sea buckthorn juice prepared by the method according to any one of claims 1-7.

9. A method for selectively reducing the content of 2-pentylfuran, 1-octen-3-one, trans-2-decenal, and trans,trans-2,4-decadienal in sea buckthorn juice, characterized in that, Includes the following steps: (1) Wash and crush the sea buckthorn fruit to obtain sea buckthorn pulp; (2) Adjust the pH of the sea buckthorn pulp to 1.0 to 3.0, freeze it at -20 to -5℃ for 6 to 14 hours, take it out and thaw it, and then heat and stir it at 50 to 60℃ for 10 to 60 minutes to obtain the treated sea buckthorn pulp; (3) Filter the processed sea buckthorn pulp directly, discard the first pulp, and obtain sea buckthorn juice; (4) Adjust the pH of the original juice of sea buckthorn to 3.5-4.5, centrifuge, remove the second pulp, homogenize and sterilize the clear liquid to obtain sea buckthorn juice.

10. A method for processing fruit wine, characterized in that, The processing method described above involves first preparing sea buckthorn juice using the method described in any one of claims 1-7 to reduce the content of volatile off-flavor compounds in sea buckthorn juice without significantly affecting its overall flavor, and then fermenting it into sea buckthorn wine.

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