Method for improving the cooking quality of brown rice by lactic acid bacteria fermentation

Abstract

The invention discloses a method for improving the cooking and eating quality of brown rice by using Lactic acid bacteria fermentation, which belongs to the technical field of food processing. The method comprises the steps of mixing activated lactic acid bacteria with water and brown rice, loading the mixture into a one-way outgassing container, removing excess air or filling up the container, and sealing the container and performing fermentation. The invention is very simple and easy to operate, and has very low energy consumption. It is suitable to be up scaled for industrial production and will significantly promote brown rice to become a staple food.

Claims

1. A method for improving brown rice quality, comprises the steps of: 1) mixing 510.sup.7-210.sup.8 cfu/g activated Lactobacillus plantarum with water and brown rice to obtain a fermentation mixture, wherein the fermentation mixture has an initial moisture content of 25-35%; 2) loading the fermentation mixture into a one-way outgas sing fermentation container; 3) removing air or filling up the fermentation container with the fermentation mixture; and 4) sealing the fermentation container and performing fermentation at 25-40 C. for 16-24 hours to obtain fermented brown rice having more GABA than that of brown rice.

2. The method of claim 1, wherein said one-way outgassing container has a one-way air outlet valve; and wherein the container meets the requirements of food safety.

3. The method of claim 1, wherein said Lactobacillus plantarum can produce lactic acid from carbohydrates.

4. The method of claim 1, wherein said brown rice is whole grain caryopsis with inedible outer hull removed while retaining the husk, the bran and the aleurone layer.

5. The method of claim 1, further comprising drying said fermented brown rice and packing them in a sealed package.

6. The method of claim 1, wherein moisture content of said fermented brown rice is 14%.

Description

BRIEF DESCRIPTION OF FIGURES

(1) FIG. 1 is a picture of cooked rice from fermented brown rice and raw brown rice in Example 1. a: raw brown rice, b: fermented brown rice.

(2) FIG. 2 is a comparison chart of the water absorption rate of fermented brown rice and raw brown rice at 30 C. as in Examples 1-3.

EXAMPLES

(3) The following examples are intended to further illustrate but not limit the scope of the invention.

(4) Determination/Measurement Methods:

(5) The optimum cooking time is determined as follows: add 150 mL water into a 250 mL beaker, place it on a heating plate and heat to boil, then carefully pour in 5 g whole grain brown rice and record the start timer. Take out 10 grains of rice after 15 minutes, press the rice with a glass slide to see if there is a white core, and repeat it every minute until the white core number is 1, and record the stop time. The minutes between the start and the stop time plus 2 min for braising is the optimum cooking time.

(6) Determination of iodine blue value: weigh 7.0 g dry whole grain brown rice to a wire basket, wash it five times with tap water and once with distilled water, put it into a 250 mL beaker and add 50 C. distilled water to the total volume of 150 mL. Cook 20 min in a boiling water pan (start to count the time when the temperature reaches 100 C.). Put the wire basket on top of the beaker until no rice soup drops from it. Dilute the rice soup to 100 mL when it is cooled to room temperature. Take 1 mL supernatant of the rice soup after centrifugation, and add it to 50 mL distilled water, add 5 mL 0.5 mol/L HCl and 1 mL 0.2 g/100 mL iodine reagent, and make the final volume to be 100 mL. The absorbance of the above solution is measured at 660 nm by a spectrophotometer.

(7) Determination of hardness and viscosity of cooked rice: parameters of physical property tester: Operation type is Compression; Pre-Test Speed is 2 mm/sec; Test Speed is 0.5 mm/sec; Post-Test Speed is 0.5 mm/sec; Test cycle index is 1; Target unit is Strain; Target strain is 70.0%; Trigger is 5.0 g; and Detector head is P/35 (35 mm dia cylinder aluminium).

(8) Remove the upper layer of cooked rice, take 3 grains of rice randomly from the middle layer and place symmetrically on the object stage of the physical property tester with the position of the rice grain fixed. Each sample should be determined 8 times, abandon the maximum and minimum value and take the average value of the remaining six results.

(9) Sense assessment is used to assess the acidity of rice: smell the evaporated water vapor during cooking process and taste the rice to assess its acidity.

(10) The method of GABA determination is slightly modified from the reference NY/T 2890-2016: weigh 1 g samples into a 50 mL centrifuge tub; add 10 mL 5% TCA; extract for 30 min using ultrasound-assisted extraction; let it stand for 5 min after 2 min oscillation in vortex mixer; transfer the supernatant to a 25 mL volumetric flask after 2 min centrifugation at the speed of 5000 r/min; repeat the same extraction once with the residue and combine both extracts; and make the final volume to be 25 mL. Filter the extract with double layer filter paper; take 1 ml filtrate and centrifuge it at 10,000 rpm for 10 minutes; and take 400 l supernatant for the test. The chromatographic conditions are as follows: C.sub.18 chromatographic column: 250 mm4.6 mm, 5 m; detection wavelength: 436 nm; column temperature: 30 C.; injection volume: 10 L; mobile phase: acetonitrile with sodium acetate solution; and flow rate: 1.0 mL/min.

(11) Determination of moisture content in brown rice: put a clean aluminum box with a lid beside into a 105 C. oven for 1 hr; take it out, cover it, cool it in a dryer for 0.5 hr, weigh the cooled aluminum box with the lid; and repeat drying and weighing the box after drying until the difference of two consecutive values is less than 2 mg. The last weight is the mass of the aluminum box (m.sub.3). Ground the brown rice and sift it by a 60 mesh sieve; weigh 2 g (accurate to 0.0001 g) into the aluminum box with sample thickness less than 5 mm. This is the combined mass of the aluminum box and the sample before drying (m.sub.1). Place it in the 105 C. oven for 1 hr, take it out, cover it, and cool it for 0.5 h in the dryer; weigh the cooled aluminum box with the lid; and repeat drying and weighing the box after drying until the difference of two consecutive values is less than 2 mg. This last weight is the combined mass of the aluminum box and the dry sample (m.sub.2).

(12) The water content in the sample can be calculated by using formula (1).
X=(m.sub.1m.sub.2)/(m.sub.1m.sub.3)100formula (1)
Wherein,
XThe moisture content in the sample (%);
m.sub.1Mass of the aluminum box and the sample before drying (g);
m.sub.2Mass of the aluminum box and the sample after drying (g);
m.sub.3Mass of the aluminum box (g).

(13) Determination of water absorption rate at 30 C.: add 220 mL deionized water in a 250 mL beaker; incubate at 30 C. in a water bath; weigh 5.0000 g whole grain rice and pour into a copper wire mesh placed in the 250 mL beaker and start the timer; take out the brown rice after soaking for 15, 30, 45, 60, 80, 100, 130, 160 and 200 minutes, respectively; after drying the surface moisture with gauze, weight the brown rice using an electronic analytical balance.
Water absorption rate (%)=(mass after soaking-mass before soaking)/(mass after soaking(1the moisture content))100%

Example 1

(14) Weigh 1000 g sorted whole grain brown rice; add activated Lactobacillus plantarum liquid at the inoculation rate of 5.010.sup.7 cfu/g; mix evenly and pour the mixture into a fermentation bag with a one-way air outlet valve; add water to make the initial moisture content of the fermentation system at 25%; perform the fermentation at 35 C. for 24 hours. Dry the fermented rice and seal it in a degassed bag.

Example 2

(15) Weigh 1000 g sorted whole grain brown rice; add activated Lactobacillus plantarum liquid at the inoculation rate of 2.010.sup.8 cfu/g; mix evenly and pour the mixture into a fermentation bag with a one-way air outlet valve; add water to make the initial moisture content of the fermentation system at 35%; perform the fermentation at 25 C. for 20 hours. Dry the fermented rice and seal it in a degassed bag.

Example 3

(16) Weigh 1000 g sorted whole grain brown rice; add activated Lactobacillus plantarum liquid at the inoculation rate of 1.010.sup.8 cfu/g; mix evenly and pour the mixture into a fermentation bag with a one-way air outlet valve; add water to make the initial moisture content of the fermentation system at 30%; perform the fermentation at 40 C. for 16 hours. Dry the fermented rice and seal it in a degassed bag.

Comparative Example 1

(17) Weigh 1000 g sorted whole grain brown rice; add activated Lactobacillus plantarum liquid at the inoculation rate of 1.510.sup.8 cfu/g; mix evenly and pour the mixture into a fermentation bag with a one-way air outlet valve; add water to make the initial moisture content of the fermentation system at 20%; perform the fermentation at 35 C. for 24 hours. Dry the fermented rice and seal it in a degassed bag.

Comparative Example 2

(18) Weigh 1000 g sorted whole grain brown rice; add activated Lactobacillus plantarum liquid at the inoculation rate of 1.510.sup.8 cfu/g; mix evenly and pour the mixture into a fermentation bag with a one-way air outlet valve; add water to make the initial moisture content of the fermentation system at 40%; perform the fermentation at 35 C. for 16 hours. Dry the fermented rice and seal it in a degassed bag.

Summary of the Results

(19) The pictures of brown rice before (FIG. 1a) and after (FIG. 1b) the fermentation with lactic acid bacteria are shown in FIG. 1. It can be seen in FIG. 1 that the endosperm grin rate and the cracking degree of rice cortex were significantly higher in fermented brown rice than those in raw brown rice, indicating that the cooking quality of brown rice after fermentation was well improved.

(20) The cooking method of brown rice is as follows: weigh and wash 100 g rice from Example 1 and raw brown rice, respectively; put them into respective rice cookers and add 190 g tap water; and cook for 60 minutes including 25 min holding time.

(21) The water absorption of fermented brown rice from Example 1-3 is compared with the raw brown rice in FIG. 2. The quantity and rate of water absorbability in fermented brown rice increased significantly compared to that of the raw brown rice.

(22) The optimum cooking time, the iodine blue value, the rice hardness, the rice viscosity and GABA content are shown in Table 1.

(23) TABLE-US-00001 TABLE 1 Comparison of cooking quality, acidity and GABA content of brown rice before and after fermentation Optimum cooking Iodine Rice Rice GABA time blue hardness viscosity Rice content Project (min) value (g) (g .Math. s.sup.1) acidity (mg/kg) Raw brown rice 28.20 0.139 1417.2 37.1 none 61.4 Example 1 22.99 0.213 932.6 69.2 slight 175.2 Example 2 23.11 0.204 942.3 67.3 slight 184.2 Example 3 23.20 0.207 951.1 65.9 slight 179.5 Comparative 25.31 0.161 1209.4 49.1 slight 73.7 Example 1 Comparative 23.17 0.205 949.3 68.7 heavy 181.1 Example 2

(24) The results of Table 1 show that the fermentation treatment in Example 1-3 significantly shortened the cooking time and improved the cooking quality of brown rice. The increase of iodine blue content indicates increased release of starch and other soluble substances and improved rice taste. Rice hardness is decreased and the viscosity is significantly increased in fermented brown rice, indicating better taste and eating quality. These data show that suitable fermentation conditions can improve brown rice taste and quality. The acidity of rice is due to the accumulation of lactic acid in the fermentation process. When the fermentation is not adequate as shown in comparative Example 1, the brown rice quality and taste improvement is limited, and cannot meet customers' requirement. When the fermentation is over done as shown in comparative Example 2, increased acidity of the rice is not acceptable to customers, either. It is also shown in Table 1 that GABA content is greatly increased during the fermentation process.

(25) While the present invention has been described in some detail for purposes of clarity and understanding, one skilled in the art will appreciate that various changes in form and detail can be made without departing from the true scope of the invention. All figures, tables, appendices, patents, patent applications and publications, referred to above, are hereby incorporated by reference.