Method for reducing zearalenone in coix seeds

Abstract

The invention provides a method for reducing zearalenone (ZEN) in coix lacryma-jobi kernels, which comprises the following steps: firstly, crushing coix lacryma-jobi kernels to obtain coix lacryma-jobi kernel powder; and then the coix seed powder is subjected to heating treatment. Wherein the temperature of the heating treatment is 160 to 200 DEG C, and the time of the heating treatment is 30 to 60 minutes. According to the method, the temperature and the time are accurately controlled, on the premise that the quality of the coix seeds is guaranteed, efficient reduction of the ZEN and the derivatives of the ZEN is achieved, and the reduction rate can reach 80% or above at most. The method does not need to add any chemical reagent or complex equipment, is safe and environment-friendly, conforms to the development trend of green agriculture, and is suitable for large-scale popularization and application. Reliable technical support is provided for reduction of ZEN pollution in coix seeds, the market competitiveness of coix seed products is improved, and healthy development of the coix seed industry is promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of zearalenone reduction, and particularly to a method for reducing zearalenone in coix seeds. Background Art

[0002] Coix Seed, also known as coix seed, is a common medicinal and edible grain with rich nutritional value. In recent years, with the continuous exploration of various values of coix seed and the increasing annual export volume, the production and research of coix seed have developed rapidly, and the number of people consuming coix seed and the consumption amount have also increased. Mycotoxins are toxic secondary metabolites produced by fungi. Coix seed is prone to fungal infection during field growth, resulting in the production of mycotoxins. Improper transportation and storage methods after coix seed harvesting can also cause the accumulation of mycotoxins. Multiple studies have shown that the contamination of zearalenone (ZEN) in coix seed is quite serious, seriously threatening food safety and the health of humans and animals. However, in the existing technology, there are few studies on reducing ZEN in coix seed by temperature regulation, and there is a lack of systematicness and in-depthness.

[0003] Zearalenone (ZEN), also known as F-2 toxin, is a steroid-like estrogenic mycotoxin. The main derivatives of ZEN are α-zearalenol (ZEL) and zearalanone (ZAN). As a strong estrogen analogue, ZEN can have an adverse impact on the reproductive system, leading to reproductive dysfunction. The existing ZEN reduction technical solutions mainly include the following several types:

[0004] (1) Physical adsorption method: Using adsorbents such as activated carbon and diatomaceous earth to adsorb ZEN, the operation is simple, but there are problems such as adsorbent residue and loss of nutritional components. Adsorbent residue may cause secondary pollution and will also adsorb some nutritional components, affecting the quality of coix seed.

[0005] (2) Chemical reduction method: Using oxidants such as ozone and hydrogen peroxide to reduce ZEN, with high efficiency, but may produce toxic by-products, posing a safety hazard, and having high requirements for equipment and high costs.

[0006] (3) Biological reduction method: Using microorganisms or enzymes to reduce ZEN, which is safe and environmentally friendly. However, the reduction efficiency is unstable, greatly affected by environmental factors, and the process of strain screening and cultivation is complex, making it difficult to achieve large-scale application.

[0007] (4) Pressurized heat treatment detoxification technology: Research shows that under the pressurized cooking conditions of 120-140 °C, 73%-83% of ZEN in contaminated food can be removed. However, heat treatment and pressure cooking mainly act on the fungi that produce zearalenone. Moreover, if the conditions of the pressurized heat treatment method are not properly controlled, it may change the nutritional value of feed and food, resulting in economic losses.

[0008] The common problems in the existing technologies are high cost, low efficiency or damage to the quality of coix seeds. In addition, they are often difficult to precisely control, especially in large-scale applications, it is difficult to ensure the consistency and effectiveness of treatment. Moreover, most of the existing methods only involve ZEN and ignore α-ZEL and ZAN with higher toxicity. Therefore, developing an efficient, safe and economical method for reducing ZEN and its derivatives is of great significance for ensuring the food safety of coix seeds and their products. Summary of the Invention

[0009] The purpose of the present invention is to provide a method for reducing zearalenone in coix seeds. By heating the coix seeds, that is, heating at 160-170 °C for 45-60 min or heating at 180-200 °C for 30-45 min, while sterilizing and reducing ZEN, the original nutritional value and taste characteristics of coix seeds are maintained.

[0010] The present invention solves its technical problems by adopting the following technical solutions.

[0011] The present invention provides a method for reducing zearalenone in coix seeds, comprising the following steps:

[0012] S1. Crush the coix seeds to obtain coix seed powder;

[0013] S2. Perform heat treatment on the coix seed powder, the temperature of the heat treatment is 160-200 °C, and the heat treatment time is 30-60 min.

[0014] The beneficial effects of the method for reducing zearalenone in coix seeds according to the embodiments of the present invention are:

[0015] The present invention provides a method for promoting the reduction of zearalenone and its derivatives (α-ZEL, ZAN) in coix seeds by temperature regulation. By precisely controlling the temperature and time, on the premise of ensuring the quality of coix seeds, the efficient reduction of ZEN and its derivatives is achieved, and the highest reduction rate can reach more than 80%. The present invention first targets the reduction of ZEN, α-ZEL, and ZAN in coix seeds. This method can achieve the reduction of toxins only by controlling the temperature and time, without adding any chemical reagents, which is safe, environmentally friendly, and in line with the development trend of green agriculture. In addition, the present invention does not require complex equipment, meets the needs of families and processing manufacturers, and is suitable for large-scale popularization and application. The present invention provides reliable technical support for the reduction of ZEN pollution in coix seeds, helps to enhance the market competitiveness of coix seed products, and promotes the healthy development of the coix seed industry.

[0016] The reduction method of the present invention is specifically designed for coix seeds, can achieve the efficient degradation of ZEN and its derivatives in coix seeds, and has matrix specificity. By precisely controlling the temperature and time, using the lowest temperature and the least time, the nutritional components and sensory quality of coix seeds are retained to the greatest extent, and problems such as the decline of nutrition and quality caused by high-temperature treatment are solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can also be obtained based on these drawings without creative efforts.

[0018] Figure 1 It is the extracted ion flow MRM chromatogram of the ZEN standard sample;

[0019] Figure 2 It is the extracted ion flow MRM chromatogram of the ZAN standard sample;

[0020] Figure 3 It is the extracted ion flow MRM chromatogram of the α-ZEL standard sample;

[0021] Figure 4 It is the change curve graph of the ZEN reduction rate of the positive coix seed sample in Test Example 1 at different temperatures and times. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Those not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0023] The following specifically describes the method for reducing zearalenone in coix seeds according to the embodiments of the present invention.

[0024] A method for reducing zearalenone in coix seeds provided by an embodiment of the present invention includes the following steps:

[0025] S1. Crush the coix seeds to obtain coix seed powder.

[0026] S2. Heat-treat the coix seed powder at a temperature of 160 - 200°C for 30 - 60 min. High temperature can not only change the chemical structure of ZEN in coix seeds, but also inhibit or kill the residual fungi in coix seeds, and has strong antibacterial and anti-corrosion capabilities. By heat-treating the coix seed powder at high temperature in the present invention, the concentration of mycotoxins can be significantly reduced in a short time, and there is no need to use chemical agents, thus avoiding the problems of chemical residues in food and environmental pollution. It is more convenient and effective than traditional methods and is suitable for large-scale sample processing. In addition, high temperature can also promote the reduction of ZEN and its derivatives, converting them into non-toxic or low-toxic substances. It should be noted that temperatures above 200°C may cause loss of nutritional components in coix seeds. Therefore, the heat treatment temperature in the present invention is 160 - 200°C to ensure the nutritional value and taste of coix seeds.

[0027] Further, in a preferred embodiment of the present invention, the heat treatment is carried out in a constant temperature forced air drying oven. The operation of the present invention is simple, economical and environmentally friendly. The required constant temperature forced air drying oven can be taken from kitchen small appliances, such as ovens, etc. It can not only be widely used in daily life to prevent long-term and large-scale intake of zearalenone, but also be applicable to actual processing by enterprises and large-scale production, etc., to improve the food safety of products.

[0028] Further, in a preferred embodiment of the present invention, the heat treatment temperature is 160 - 170°C and the heat treatment time is 45 - 60 min.

[0029] Further, in a preferred embodiment of the present invention, the heat treatment temperature is 180 - 200°C and the heat treatment time is 30 - 45 min.

[0030] The effectiveness of the mycotoxin detoxification method depends on the type of mycotoxin, its concentration, the toxin-producing mechanism, and the degree of binding between the mycotoxin and the components of the food matrix, etc. The present invention is designed for coix seed and provides a simple, safe, efficient, and low-cost method for reducing zearalenone (ZEN) and its derivatives α-zearalenol (α-ZEL) and zearalanone (ZAN). This method uses a thermostatic forced-air drying oven to heat the coix seed, that is, heating at 160 - 170 °C for 45 - 60 min (ZEN reduction rate 30% - 58%), or heating at 180 - 200 °C for 30 - 45 min (ZEN reduction rate 48% - 80%). While sterilizing and reducing ZEN, it can also maintain the original nutritional value and taste characteristics of the coix seed. Using this method to reduce ZEN in coix seed, the reduction rate can reach about 45 - 80%, and the effect is good.

[0031] The features and properties of the present invention will be further described in detail below in conjunction with the embodiments.

[0032] Example 1

[0033] This example provides a method for reducing zearalenone in coix seed, which includes the following steps:

[0034] (1) Grind 100 g of coix seed to obtain homogeneous coix seed.

[0035] (2) Use a thermostatic forced-air drying oven to set the temperature to 160 °C and keep it stable.

[0036] (3) Place the homogeneous coix seed sample obtained in (1) in the thermostatic forced-air drying oven and heat for 60 min.

[0037] Example 2

[0038] This example provides a method for reducing zearalenone in coix seed, which includes the following steps:

[0039] (1) Grind 100 g of coix seed to obtain homogeneous coix seed.

[0040] (2) Use a thermostatic forced-air drying oven to set the temperature to 170 °C and keep it stable.

[0041] (3) Place the homogeneous coix seed sample obtained in (1) in the thermostatic forced-air drying oven and heat for 45 min.

[0042] Example 3

[0043] This example provides a method for reducing zearalenone in coix seed, which includes the following steps:

[0044] (1) Grind 100 g of coix seed to obtain homogeneous coix seed.

[0045] (2) Use a thermostatic forced-air drying oven to set the temperature to 180 °C and keep it stable.

[0046] (3) Place the homogenized coix seed sample obtained in (1) in the thermostatic forced-air drying oven for 30 min of heating.

[0047] Example 4

[0048] A method for reducing zearalenone in coix seeds is provided in this example, which includes the following steps:

[0049] (1) Crush coix seeds (100 g) to obtain homogenized coix seeds.

[0050] (2) Use a thermostatic forced-air drying oven to set the temperature to 190 °C and keep it stable.

[0051] (3) Place the homogenized coix seed sample obtained in (1) in the thermostatic forced-air drying oven for 30 min of heating.

[0052] Comparative Example 1

[0053] A method for reducing zearalenone in coix seeds is provided in this comparative example, which includes the following steps:

[0054] (1) Crush coix seeds (100 g) to obtain homogenized coix seeds.

[0055] (2) Use a thermostatic forced-air drying oven to set the temperature to 150 °C and keep it stable.

[0056] (3) Place the homogenized coix seed sample obtained in (1) in the thermostatic forced-air drying oven for 90 min of heating.

[0057] Test Example 1

[0058] In this test example, the zearalenone-positive coix seed samples (background concentration of 151 ± 17 μg / kg, purchased from Xiamen Xinlehai Department Store Co., Ltd., No. 599 Guankou South Road, Guankou Town, Xiamen, brand: The Catcher in the Rye, origin: Qianxinan Buyei and Miao Autonomous Prefecture, Guizhou Province) were detoxified according to the method for reducing zearalenone in coix seeds of the present invention (each experiment was repeated 6 times in parallel), and then the contents of ZEN, α-ZEL, and ZAN in coix seeds before and after treatment at different temperatures (160, 170, 180, 190, 200, and 150 °C) and different times (15, 30, 45, 60, 75, and 90 min) were measured, and the reduction rate was calculated according to formula (1):

[0059] Reduction rate (%) = (background concentration - concentration after treatment) / background concentration × 100% (1)

[0060] Among them, the coix seeds were heated at different temperatures and times using a constant temperature forced air drying oven. Before and after the treatment, ZEN, α-ZEL, and ZAN in the coix seeds were extracted with an acetonitrile-water-(70 + 30, volume ratio) solution. After the extract was diluted, centrifuged, and filtered, a certain concentration 13 of C-labeled mycotoxin isotope internal standard solution was added, and it was determined by the multiple reaction monitoring mode (negative ion mode) of a liquid chromatography-tandem mass spectrometer. The stable isotope dilution internal standard method was used for quantification. The specific steps were as follows:

[0061] (1) Sample extraction and purification:

[0062] Accurately weigh 5 g of the homogenized sample into a 50 mL centrifuge tube, add 20 mL of an acetonitrile-water (70:30, volume ratio) solution, shake and extract for 20 min, and then centrifuge the mixture at 8000 rpm for 10 min. Pipette 500 μL of the supernatant into a 2 mL microcentrifuge tube, add 500 μL of pure water, and mix well. Centrifuge at 10000 rpm for 5 min, and pipette the supernatant through a 0.22 μm filter membrane. Pipette 200 μL of the treated sample filtrate into a 300 μL inner insert tube, add 20 μL of the isotope mixed internal standard solution, vortex and mix well, and wait for injection.

[0063] (2) Liquid chromatography conditions: Liquid chromatography column: Shim-pack Scepter C18-120 [Metal free] column (2.1 mm × 100 mm, 1.9 μm); Mobile phase: A - water; B - acetonitrile; Flow rate: 0.3 mL / min; Column temperature: 40 °C; Injection volume: 5 μL; The gradient elution program is shown in Table 1.

[0064] Table 1 Liquid chromatography gradient elution program

[0065]

[0066] (3) Mass spectrometry conditions: Ion source: Electrospray ionization source (ESI); Scanning mode: Positive and negative ion scanning; Detection mode: Multiple reaction monitoring (MRM); Qualitative ion pairs, quantitative ion pairs, collision voltage, etc. are shown in Table 2.

[0067] Table 2 Ion information and mass spectrometry parameters of three mycotoxins

[0068]

[0069] In the present invention, ZEN, α-ZEL, and ZAN before and after the treatment of each sample were determined by HPLC-MS / MS to ensure the accuracy of method evaluation. As Figure 1 shown is the MRM chromatogram of the extracted ion current (quantitative, qualitative, and internal standard quantitative ions) of the ZEN standard sample (added with internal standard). Figure 2It is the MRM chromatogram of the extracted ion current (quantitative, qualitative and internal standard quantitative ions) of the ZAN standard sample (added with internal standard). Figure 3 Shown is the MRM chromatogram of the extracted ion current (quantitative, qualitative and internal standard quantitative ions) of the α-ZEL standard sample (added with internal standard). Figure 4 This is the change curve of the ZEN reduction rate of the coix positive sample in this test example at different temperatures and times. The removal effect of zearalenone in coix is shown in Table 3:

[0070] Table 3 Removal effect of zearalenone in coix

[0071]

[0072] From Figure 4 and Table 3, it can be seen that the reduction efficiency of ZEN in coix varies greatly at different temperatures and times: within 60 min of heating at 150 °C, there is no obvious change in ZEN. When heating for 75 - 90 min, it can be reduced by about 32 - 49%; when heating at 160 - 170 °C for 45 - 60 min, the ZEN reduction rate is 30 - 58%. However, the reduction rate may decrease when heating exceeds 60 min; when heating at 180 - 200 °C for 30 - 45 min, the ZEN reduction rate is 48 - 80%. However, the reduction rate for more heating time is not significantly improved.

[0073] This test example analyzed the contents of 3 pollutants including ZEN, its derivative ZAN and α-ZEL in 40 coix samples. It was found that coix samples with a ZEN content level greater than or equal to 61.4 μg / kg had the phenomenon of ZAN pollution at the same time, and from the content level, ZAN accounted for 1.9% - 7.7% of ZEN. α-ZEL was not detected in all samples. The contents of ZAN and α-ZEL in coix were low, and the removal effect was not obvious. But when reducing ZEN in coix by this method, it will not cause the obvious generation or increase of ZAN and α-ZEL.

[0074] Test example 2

[0075] To verify the matrix specificity of the method of the present invention, this test example selected coix tea (containing Jinsha coix, adzuki beans, euryale ferox, poria cocos, Chinese yam, tangerine peel) ZEN positive samples (the background concentration was 133 ± 13 μg / kg, purchased from the supply and marketing store in Xianyou County, Putian City, and the origin was Longhua Town, Xianyou County) and carried out elimination treatment at 170 °C and 200 °C respectively. The results are shown in Table 4:

[0076] Table 4 Removal effect of zearalenone in coix tea

[0077]

[0078] As can be seen from Table 3 and Table 4, under the same treatment conditions, the degradation rate of ZEN in coix seed tea heated at 170°C for 45 - 60 minutes is only about 11 - 15%, significantly lower than that in coix seeds (32 - 58%). The degradation rate of ZEN in coix seed tea heated at 200°C for 30 minutes is only about 24%, significantly lower than that in coix seeds (78%). The results show that the method for degrading zearalenone involved in the present invention has obvious matrix specificity and only has an obvious effect on ZEN in coix seeds.

[0079] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

Claims

1. A method for reducing zearalenone in coix seeds, characterized in that, It includes the following steps: S1. Crush coix seed to obtain coix seed powder; S2. Conduct heat treatment on the coix seed powder, the temperature of the heat treatment is 160 - 200 °C, and the heat treatment time is 30 - 60 min.

2. The method for reducing zearalenone in coix seeds according to claim 1, characterized in that, In step S2, the heat treatment is carried out in a constant temperature forced air drying oven.

3. The method for reducing zearalenone in coix seeds according to claim 1, wherein In step S2, the temperature of the heat treatment is 160 - 170 °C, and the heat treatment time is 45 - 60 min.

4. The method for reducing zearalenone in coix seeds according to claim 1, characterized in that, In step S2, the temperature of the heat treatment is 180 - 200 °C, and the heat treatment time is 30 - 45 min.

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