Storage method for improving cooking performance of brown rice and delaying quality deterioration

Abstract

The invention discloses a storage method for improving the cooking performance of brown rice and delaying quality deterioration. The method comprises the following steps: firstly, naturally drying newly harvested unhulled rice, and then carrying out rice hulling operation to prepare high-moisture brown rice; then, a high-temperature instantaneous treatment technology is adopted; then carrying out electron beam irradiation and vacuum packaging; and finally storing the high-moisture brown rice at 25 DEG C. The high moisture content (15-20%) is favorable for keeping the high nutritional value of the brown rice, and the high-temperature instantaneous treatment can effectively eliminate the unpleasant odor such as rice bran flavor, increase cracks on the surface of the brown rice to promote moisture permeation and kill microorganisms in the brown rice. The electron beam irradiation and the vacuum packaging treatment can synergistically kill microorganisms, inhibit the respiration of the brown rice, passivate the lipase activity and slow down the rising rate of the fatty acid value, so that the nutritional value and the taste quality of the high-moisture brown rice are maintained.

Description

Technical Field

[0001] The patent of this invention relates to the technical field of grain storage and preservation, and in particular to a storage method for improving the steaming performance of brown rice and delaying quality deterioration. Background Art

[0002] Brown rice is the original form of rice grains that have been husked but not further milled, with the bran, germ and endosperm intact. In terms of dietary fiber, protein, fat, vitamins and minerals, it far exceeds that of finely processed white rice and rice with the bran removed and germs retained. Brown rice is also rich in polyphenols and oryzanol and other bioactive ingredients. These nutrients play a key role in promoting the balance of human sugar and lipid metabolism and optimizing the intestinal microbial environment, and are essential for maintaining human health. However, since brown rice retains more outer tissue, it still has vitality and is prone to problems such as mildew and insect pests, which increases the difficulty and cost of storage and preservation. At the same time, since brown rice retains the bran layer, it has a heavier rice bran taste, which makes it difficult for consumers to accept.

[0003] At present, the industry mainly reduces the respiration of brown rice and inhibits the growth of microorganisms and pests by reducing the moisture content of brown rice, regulating the atmosphere and storing it at low temperature, but the moisture content has a significant impact on the freshness, processing and taste quality of brown rice. When the moisture content of brown rice itself is lower than a certain level (such as 14%), the cooked rice tastes rough. In contrast, the rice cooked from brown rice with a moisture content of more than 15% can better maintain its viscosity, making the rice taste softer and smoother, but the higher moisture content is not conducive to the storage of brown rice. Brown rice with high moisture content is prone to mildew after being stored for a period of time, and its fatty acid esters will continue to rise, thereby affecting the taste and edible quality of brown rice. In order to improve the storage stability of brown rice, patent CN 109105485B discloses a method for storage using instantaneous high-temperature fluidized treatment combined with oxygen absorbent and ethanol sustained-release agent. Although this method can extend the shelf life of brown rice, the prepared brown rice has poor storage stability and a short storage period. After 35 days of storage, the fatty acid value rises rapidly and the quality declines. In addition, due to the addition of ethanol slow-release agent during storage, the residual ethanol may affect the flavor of the food, thereby causing food safety problems, and is not suitable for special populations such as pregnant women and infants. Patent CN 114451451 B discloses a method for appropriately moistening rice combined with electron beam irradiation to extend the shelf life of embryo-retained rice. Although this method can extend the shelf life of embryo-retained rice to a certain extent, the processing technology of embryo-retained rice is relatively complicated, and the rice bran layer needs to be removed before storage, and then the rice soaking treatment is carried out, which leads to an increase in actual application costs. And the method of electron beam irradiation after moistening the rice makes it difficult for the embryo-retained rice to retain moisture, and the palatability of rice is difficult to maintain. At the same time, the shelf life of the embryo-retained rice after the method is processed still needs to be improved.

[0004] In order to improve the rice bran flavor in brown rice, existing technologies mainly adopt methods such as soaking and germinating, using enzyme preparations, or adopting flavor encapsulation technology to cover it up. To a certain extent, these methods can extend the storage time limit of brown rice and reduce its rice bran flavor, but there are also problems such as the decline in the quality of brown rice, especially in the case of long-term storage, the more significant decline in the quality of brown rice, and the substantial increase in storage costs. This seriously restricts the promotion of high-quality brown rice in China. Summary of the Invention

[0005] In view of the above problems, the object of the present invention is to provide a storage method for improving the cooking performance of brown rice and delaying the deterioration of its quality. By combining high-temperature instantaneous treatment, electron beam irradiation technology and vacuum technology, newly harvested and shelled high-moisture brown rice is processed, aiming to maintain the nutritional value of brown rice, improve its edible quality and taste, and at the same time extend its shelf life. During this process, the moisture content of brown rice completely comes from the rice itself, and no exogenous moisture is added.

[0006] In view of the above object, the present invention first provides a storage method for improving the cooking performance of brown rice and delaying the deterioration of its quality. The specific method is as follows:

[0007] (1) Hull the newly harvested paddy rice to obtain high-moisture brown rice;

[0008] (2) Perform high-temperature instantaneous treatment on the high-moisture brown rice;

[0009] (3) Perform electron beam irradiation treatment on the treated high-moisture brown rice obtained in step (2);

[0010] (4) Vacuum package and store the irradiated high-moisture brown rice obtained in step (3).

[0011] In an embodiment of the present invention, the hulling in step (1) means only removing the outer shell of the paddy rice, and retaining the bran layer, germ and endosperm.

[0012] In an embodiment of the present invention, the moisture content of the high-moisture brown rice in step (1) is 15-20%, preferably 15.6-20%, more preferably 16-19%, and even more preferably 16.5-18.5%. The moisture all comes from the brown rice itself and is not artificially added.

[0013] In an embodiment of the present invention, the temperature of the high-temperature instantaneous treatment in step (2) is 130-135°C, and the treatment time is 1-3 s.

[0014] In an embodiment of the present invention, the electron beam irradiation dose rate in step (3) is 0.5-4 kGy, the energy of the accelerated electrons is 10 MeV, the beam current rate is 1.3 mA, and the irradiation time is 2 s.

[0015] In one embodiment of the present invention, the vacuum degree of the vacuum packaging in step (4) is -60 to 85 KPa, and the air suction flow rate is 15 to 25 L / min.

[0016] In one embodiment of the present invention, the storage temperature in step (4) is 25-30°C.

[0017] The invention also provides application of the brown rice obtained according to the storage method in the food field.

[0018] Beneficial effects:

[0019] (1) The brown rice selected by the present invention has a moisture content of 15%-20%, and the moisture comes from the brown rice itself and is stored inside the brown rice. This can effectively solve the problem of high hardness and rough taste of brown rice due to the impermeability of the surface bran layer during the cooking process of brown rice.

[0020] (2) The present invention first performs high-temperature instantaneous treatment on high-moisture brown rice, then performs electron beam irradiation treatment on it, and finally vacuum-packs the irradiated brown rice. The high-temperature instantaneous treatment can effectively reduce unpleasant odors such as rice bran smell, and at the same time increase cracks on the surface of brown rice, which is conducive to water penetration and improves the stickiness of rice. The synergistic electron beam irradiation and vacuum packaging can effectively kill microorganisms in brown rice and inhibit the respiration of high-moisture brown rice, thereby effectively controlling the problem of water loss of high-moisture brown rice during storage, ensuring that the brown rice maintains an appropriate high moisture content throughout the storage period, thereby maintaining the nutritional value and taste quality of the high-moisture brown rice and extending the shelf life of the high-moisture brown rice.

[0021] (3) The present invention can effectively reduce the rate of increase of fatty acid value by subjecting high-moisture brown rice to high-temperature instantaneous treatment, electron beam irradiation and vacuum air conditioning synergistic treatment, thereby maintaining the nutritional value and taste quality of high-moisture brown rice.

[0022] (4) The electron beam irradiation used in the present invention is an emerging non-thermal processing method for food. Electron beam irradiation does not produce radioactive waste, and has higher irradiation efficiency and low cost, and can effectively maintain the commercial value of high-moisture brown rice. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The actual picture of the cooked rice of Examples 1 to 2 and Comparative Examples 1 to 12;

[0024] Figure 2 It is a sensory evaluation diagram of the cooked brown rice of Examples 1 to 2 and Comparative Examples 1 to 12. DETAILED DESCRIPTION

[0025] The technical solution of this invention patent will be clearly and completely described below in conjunction with the embodiments of this invention patent. Obviously, the described embodiments are only a part of the embodiments of this invention patent, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of this invention patent without creative efforts belong to the scope of protection of this invention patent.

[0026] Test method for brown rice properties:

[0027] The moisture content is determined according to the standard method of GB 5009.3-2016; the determination of fatty acid value refers to GB / T20569-2006 "Rules for Judging the Storage Quality of Paddy Rice"; the determination of lipase activity refers to GB / T 5523-2008 "Inspection of Grain and Oil - Determination of Lipase Activity of Grain and Oil Seeds"; the determination of the total number of mold colonies is based on GB 4789.15-2016 "National Food Safety Standard - Microbiological Examination of Foods - Determination of Total Number of Colonies".

[0028] Test method for rice texture:

[0029] Weigh 30 g of brown rice and 42 g of water, cook according to the cooking program for 30 min, and the cooked rice is measured using an XTPlus texture analyzer. Use a cylindrical probe (P / 35), and the test speeds are as follows: speed before test = 1 mm / s, test speed = 1 mm / s, speed after test = 1 mm / s. The compression ratio is 75%, and the rice sample is compressed 2 times.

[0030] Example 1

[0031] A storage method for improving the cooking performance of brown rice and delaying the deterioration of quality, including the following steps:

[0032] (1) Place the newly harvested paddy rice (N Liangyou 8424) in an environment of 20 - 30 °C and naturally dry it for 4 hours until the moisture content drops to 17 - 18%, then hull and dehull to obtain high-moisture brown rice;

[0033] (2) Take 10 kg of the high-moisture brown rice obtained in step (1) and perform high-temperature instantaneous treatment at a temperature of 135 °C for a treatment time of 2 s;

[0034] (3) Perform electron beam irradiation treatment on the high-moisture brown rice obtained in step (2), with an irradiation dose of 2 kGy, the energy of the accelerated electrons being 10 MeV, and the beam current rate being 1.3 mA.

[0035] (4) Vacuum package the high-moisture brown rice obtained in step (3) with a vacuum degree of -85 Kpa and an air extraction flow rate of 15 L / min; after vacuum packaging, store it at a temperature of 25 °C.

[0036] Example 2

[0037] Example 2 is different from Example 1 in that the newly harvested paddy rice is naturally air-dried at 20-30°C for 6 hours until the moisture content is reduced to less than 14%, and then hulled to obtain low-moisture brown rice.

[0038] Comparative Example 1

[0039] Comparative Example 1 is different from Example 1 in that step (3) is omitted, and in step (4), the high-moisture brown rice is not vacuum-packed but directly put into a fresh-keeping bag and sealed.

[0040] Comparative Example 2

[0041] Comparative Example 2 is different from Example 1 in that step (2) is omitted, and in step (4), the high-moisture brown rice is not vacuum-packed but directly put into a fresh-keeping bag and sealed.

[0042] Comparative Example 3

[0043] Comparative Example 3 is different from Example 1 in that steps (2) and (3) are omitted.

[0044] Comparative Example 4

[0045] Comparative Example 4 is different from Example 1 in that step (3) is omitted.

[0046] Comparative Example 5

[0047] Comparative Example 5 is different from Example 1 in that step (2) is omitted.

[0048] Comparative Example 6

[0049] Comparative Example 6 is different from Example 1 in that the order of steps (3) and (4) is changed, that is, the high-moisture brown rice obtained in step (2) is vacuum-packed, and then the vacuum-packed brown rice is subjected to electron beam irradiation treatment.

[0050] Comparative Example 7

[0051] Comparative Example 7 is different from Example 1 in that the time of high-temperature instantaneous treatment in step (2) is 4 s.

[0052] Comparative Example 8

[0053] Comparative Example 8 is different from Example 2 in that step (3) is omitted, and in step (4), the low-moisture brown rice is not vacuum-packed but directly put into a fresh-keeping bag and sealed.

[0054] Comparative Example 9

[0055] The difference between Comparative Example 9 and Example 2 is that step (2) is omitted, and in step (4), the low-moisture brown rice is not vacuum-packed, but directly put into a fresh-keeping bag and sealed.

[0056] Comparative Example 10

[0057] The difference between Comparative Example 10 and Example 2 is that step (2) and step (3) are omitted.

[0058] Comparative Example 11

[0059] The difference between Comparative Example 11 and Example 1 is that step (2) and step (3) are omitted, and in step (4), the high-moisture brown rice is not vacuum-packed, but directly put into a fresh-keeping bag and sealed.

[0060] Comparative Example 12

[0061] The difference between Comparative Example 12 and Example 2 is that step (2) and step (3) are omitted, and in step (4), the low-moisture brown rice is not vacuum-packed, but directly put into a fresh-keeping bag and sealed.

[0062] Table 1 shows the corresponding index data of the brown rice in Examples 1-2 and Comparative Examples 1-12 after being stored for 0 and 180 days respectively

[0063]

[0064] Table 1 gives the corresponding index data of the brown rice in Examples 1-2 and Comparative Examples 1-12 after being stored for 0 and 180 days respectively, and this data is much lower than the standards specified in GB / T 18810-2002 "Brown Rice". The above results show that the combination of electron beam irradiation and controlled atmosphere technology can effectively delay the water loss of high-moisture brown rice, inhibit the increase of lipase activity and fatty acid value content, and the growth of microorganisms. In addition, it can be seen from Table 1 that the extension of the storage period of the present invention is based on the synergistic effect of high moisture content, high temperature instantaneous, electron beam and vacuum packaging. Omitting one of these methods or changing the treatment sequence will have a great impact on the final result.

[0065] Weigh 30 g of brown rice and 42 g of water. The physical picture of the cooked rice after steaming according to the steaming program for 30 min is as Figure 1 shown. It can be seen from Figure 1 that the grain morphology of the cooked rice in Example 1 is not affected by electron beam irradiation. The brown rice grains before and after storage are plump, with normal color and luster, and the grain morphology is uniform. There are more or less some defects in the cooked rice in the comparative examples. Among them, the cooked rice in Comparative Example 1 and Comparative Example 2 is dry, fluffy and the grains are rough, while the water absorption of the cooked rice in Comparative Example 2 is poor, and it is difficult for water to enter the inside of the rice grains, and there is more water outside the cooked rice after steaming. In addition, compared with Example 1, the color of the cooked rice in Example 2 is worse, and the grain morphology of the cooked rice is also much worse.

[0066] Table 2 Rice Scoring Criteria

[0067]

[0068] Figure 2 The sensory scoring results of Examples 1-2 and Comparative Examples 1-12 are given, where the sensory scoring is the result of evaluation by professionally trained reviewers according to the scoring criteria in Table 2. According to Figure 2 the shown sensory evaluation results, after 180 days of storage, Example 1 treated by high-temperature short-time treatment, electron beam irradiation and vacuum packaging in combination demonstrated the most excellent eating quality. Its comprehensive score reached 94.65 points, significantly higher than other treatment groups (P<0.05), specifically shown as: rice smell (18.95 / 20), taste (23.80 / 25) and palatability (28.80 / 30), indicating that this treatment can effectively maintain the fresh flavor and texture characteristics of brown rice. In contrast, the comprehensive scores of untreated Comparative Examples 11 and 12 were only 11.50 and 10.80 points, showing obvious sour taste and texture deterioration. In addition, in terms of smell scoring, Example 1 treated by high-temperature short-time treatment and Comparative Example 1 were superior to other examples and comparative examples. It was verified that high-temperature short-time treatment can effectively reduce the bad smell such as the bran smell of brown rice and maintain better smell quality after 180 days of storage. However, it should be noted that for the groups using high-temperature treatment alone (Comparative Example 1) or electron beam irradiation alone (Comparative Example 2), there was still a decrease in taste scoring and deterioration of the texture of cold rice after storage, and for Comparative Examples 4, 5, and 7 using the combination of the two technologies, the sensory quality also deteriorated at the end of storage, indicating that the combination of high-temperature short-time treatment, electron beam irradiation and vacuum packaging can delay the deterioration of brown rice quality, while a single treatment method or the combination of two methods cannot achieve the inhibition of the deterioration of brown rice quality.

[0069] Table 3 Texture Data of Brown Rice in Examples 1-2 and Comparative Examples 1-8 at 0 days of storage

[0070]

[0071]

[0072] Table 4 Texture Data of Brown Rice in Examples 1-2 and Comparative Examples 1-8 at 180 days of storage

[0073]

[0074] Table 3 and Table 4 respectively give the texture characteristic data of the cooked rice from the brown rice in Examples 1-2 and Comparative Examples 1-12. According to Table 3, it can be observed that Example 1 with a higher moisture content showed significant advantages in terms of hardness, elasticity, stickiness, and chewiness, thus having better palatability of the rice. Specifically, the initial hardness of Example 1 was 1628.8 ± 150.89 g, and after 180 days of storage, its hardness value increased to 2118.35 ± 82.17 g. It is worth noting that whether before or after storage, the hardness value, stickiness, and elasticity of Example 1 were significantly better than those of Example 2. In contrast, the initial hardness value of Example 2 in the early stage of storage had reached 3361.93 ± 505.45 g, such a high hardness of the rice led to a relatively rough taste. This result indicates that appropriately increasing the moisture content in brown rice can effectively improve the cooking quality problems such as the hardness and stickiness of brown rice. In addition, for the rice in Comparative Examples 1-12, after 180 days of storage, the hardness of the brown rice increased rapidly, while the stickiness and elasticity decreased rapidly, which led to a significant deterioration in the palatability of the rice. This further shows that the synergistic effect of the three methods of high-temperature short-time treatment, electron beam irradiation, and modified atmosphere packaging has a significant effect in effectively inhibiting the rapid deterioration of the cooking quality of high-moisture brown rice and other problems.

[0075] In summary, for the brown rice in the present invention that is synergistically treated by high-temperature short-time treatment, electron beam irradiation, and vacuum packaging, its respiration is significantly inhibited, and the moisture content can be stably maintained at 15%-20%. This moisture distribution characteristic effectively solves the cooking problem caused by the water-impermeability of the bran layer. Specifically manifested as: through high-temperature short-time treatment at 130-135°C, microcracks are formed on the surface of the brown rice to promote water penetration, reducing the hardness of the cooked rice to 1628.8 g and increasing the stickiness to 0.90, while eliminating the off-flavor of rice bran; combined with electron beam irradiation and vacuum packaging, the fatty acid value only increases by 18.95% after 180 days of storage, and the total number of mold colonies is controlled within 9 CFU / g. This synergistic mechanism not only delays the activity of lipase and the loss of nutrients, but also extends the shelf life under the storage condition of 25°C to more than 180 days, and the comprehensive score of the eating quality remains 94.65 points.

[0076] The embodiments provided above are not intended to limit the scope covered by the present invention, nor are the described steps intended to limit their execution order. Obvious improvements made by those skilled in the art to the present invention in combination with the existing common general knowledge also fall within the protection scope defined by the claims of the present invention.

Claims

1. A storage method for improving the cooking performance of brown rice and delaying the deterioration of quality, characterized in that, It includes the following steps: (1) Hull the newly harvested paddy rice to remove the husk and obtain high-moisture brown rice; (2) Conduct high-temperature instantaneous treatment on the high-moisture brown rice; (3) Conduct electron beam irradiation treatment on the treated high-moisture brown rice obtained in step (2); (4) Vacuum package and store the irradiated high-moisture brown rice obtained in step (3). Among them, the hulling and husk removal in step (1) means only removing the outer husk of the paddy rice and retaining the bran layer, germ, and endosperm.

2. The storage method according to claim 1, wherein The moisture content of the high-moisture brown rice in step (1) is 15-20%.

3. The storage method according to claim 1, characterized in that, The moisture content of the high-moisture brown rice in step (1) is 15.6-20%.

4. The storage method according to claim 1, wherein The temperature of the high-temperature instantaneous treatment in step (2) is 130-135°C, and the treatment time is 1-3 s.

5. The storage method according to claim 1, characterized in that, The electron beam irradiation dose rate in step (3) is 0.5-4 kGy, the energy of the accelerated electrons is 10 MeV, the beam current rate is 1.3 mA, and the irradiation time is 2 s.

6. The storage method according to claim 1, characterized in that The vacuum degree of the vacuum packaging in step (4) is -60-85 Kpa, and the air extraction flow rate is 15-25 L / min.

7. The storage method according to claim 1, characterized in that, The storage temperature in step (4) is 25-30°C.

8. Application of the brown rice obtained by the storage method according to claims 1-7 in the food field.

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