Stabilized rice aleurone slurry and processing method thereof

Abstract

The invention relates to rice bran stabilization. The method sequentially comprises the following steps: adding 30-40% (preferably 35%) of water into the rice bran, and performing colloid milling to 70-100 meshes; filling a pressure-resistant polyethylene bag with the rice bran paste, bagging by 50-80%, sealing and exhausting air; treatment is conducted for 100-300 s (preferably 600 MPa / 180 s) in an HPP cavity with water as a pressure conduction medium at the pressure of 500-650 MPa; and then carrying out one-time passing-type instantaneous airflow drying at the air inlet temperature of 210 + / -1 DEG C and the air outlet temperature of 90 + / -1 DEG C to obtain the stabilized rice bran powder. Under representative conditions, the activity of the residual lipase is 9.33 + / -0.55%, the retention rate of alpha-tocopherol is 85.13 + / -2.06%, and the acid value reaches the standard after being stored at normal temperature (25-35 DEG C) for 12 weeks. Parameters can be quantified and copied, and the method is suitable for industrial amplification.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of deep processing of agricultural products / food processing technology, and in particular to a processing method for stabilizing rice aleuronium slurry by using high-frequency ultrasonic treatment followed by ultra-high pressure treatment, and a stabilized rice aleuronium slurry obtained by the method. BACKGROUND

[0002] A large amount of rice aleuronium components are generated during rice processing. The rice aleuronium components are composed of pericarp, seed coat, outer endosperm, aleuronium layer and embryo, wherein the aleuronium layer is located between the seed coat and the endosperm, and accounts for about 7% to 9% of the total mass of the seed, and is rich in nutritional active ingredients such as dietary fiber, minerals, alpha-tocopherol, oryzanol, phytic acid, squalene, phenolic acid and lignan, and has high development and utilization value.

[0003] During the milling and separation process, after the integrity of the rice is destroyed, lipase and peroxidase are rapidly activated, and triacylglycerol is hydrolyzed to generate free fatty acids, which easily causes oxidative rancidity, leading to rapid deterioration of quality. Public data and industrial practice show that fresh rice aleuronium deteriorates obviously within 6 hours if not effectively treated, and the content of free fatty acids can reach 7% to 8% after 24 hours, and then still rises at a rate of about 5% per day. In order to realize storage and food utilization, it is necessary to first implement stabilization treatment to inhibit the quality decay caused by enzymatic reaction and fat oxidation.

[0004] There are mainly two types of existing technologies for the stabilization of rice aleuronium / aleuronium layer (and related systems such as rice bran): one is a heat treatment-drying route represented by steam, microwave, extrusion, hot air / roller (scraper), etc.; the other is the separate application or loose connection of non-thermal treatment units such as ultra-high pressure or high-frequency ultrasound. The former can improve enzyme inactivation and shelf stability to a certain extent, but often has problems such as loss of active ingredients, high energy consumption and equipment burden, or insufficient adaptability to liquid / slurry systems; the latter also has the situation of incomplete enzyme inactivation or insufficient room temperature shelf stability when only high-frequency ultrasound or only ultra-high pressure is used in some grain and oil by-product systems. Overall, it is still a challenge to simultaneously achieve "complete enzyme inactivation, high retention of active ingredients, and room temperature shelf stability" under low heat history conditions.

[0005] The research and industrialization exploration of rice aleurone components started early in China, but mostly focused on powder. The feasibility of the stabilization approach has been verified (e.g., CN201910958800.7), but there are still problems in practical application, such as large equipment investment, long production cycle, limited retention rate of functional components such as oryzanol and α-tocopherol, etc. Compared with this, the liquid / slurry system with rice aleurone components as the main solid (i.e., "rice aleurone slurry") is relatively insufficient in public reports and mass production experience. The stabilization path and parameter window that balances enzyme inactivation, nutrient retention, and storage hygiene requirements under the conditions of short process and low heat history are still unclear.

[0006] Based on the above status, the key technical problems concerned in the field mainly include: ① efficient and repeatable inactivation of lipase / peroxidase, and long-term controllable acid value / fatty acid value during shelf life; ② reducing heat history to protect heat-sensitive active ingredients such as α-tocopherol and oryzanol in liquid / slurry system; ③ achieving microbiological safety and shelf stability at room temperature; ④ forming a stabilization process with clear parameters, scalable and strong adaptability to rice aleurone slurry under the premise of process simplification, acceptable energy consumption and cost. SUMMARY

[0007] The existing stabilization technology for rice aleurone (including aleurone layer, etc.) cannot simultaneously balance sufficient enzyme inactivation, active ingredient retention, and room temperature shelf stability under low heat history conditions, and lacks clear constraints on filling and bagging, exhaust, ultra-high pressure (HPP) pressure-time window, and the sequence of each unit operation, which lacks consistency and reproducibility in industrial scaling. To solve the above problems, the present application proposes a set of rice aleurone slurry stabilization method and its product with fixed sequence, quantifiable parameters, and suitable for industrial scaling.

[0008] To achieve the above purpose, the following technical scheme is proposed: a processing method for stabilizing rice aleurone slurry, at least including and limiting the following steps and conditions: (1) slurry preparation: mixing rice aleurone components with water, with water addition amount of 30%-40% based on rice aleurone components, and processing by colloid mill to solid particle size of 70-100 mesh to obtain uniform rice aleurone slurry; (2) high-frequency ultrasonic treatment: treating the rice aleurone slurry at a frequency of 20-40 kHz, a power of 500-1000 W, and a temperature of 50-100°C for 60-300 s; (3) filling and exhaust: filling the high-frequency ultrasonic treated rice aleurone slurry into a pressure-resistant polyethylene bag, with bagging capacity of 50%-80% of the bag volume and not more than 80%, and sealing after exhausting the air in the bag; the volume of the polyethylene bag is preferably 5-15 L; (4) High pressure processing (HPP): the sealed bag is placed in a high pressure processing chamber, water is used as pressure conducting medium and the water level is higher than the bag, and the processing is performed at 500-650 MPa for 100-300 s; The order of the above steps is fixed, i.e., high frequency ultrasonic treatment is performed first, and then high pressure processing is performed; any change in the order or omission of any step is difficult to achieve the expected stabilization effect.

[0009] Preferably, the amount of water added in step (1) is 35%, and the preferred particle size of the colloid mill is 80 mesh; the preferred parameters of high frequency ultrasonic in step (2) are 25 kHz, 800 W, 60 ℃, and 180 s; the preferred parameters of high pressure processing in step (4) are 600 MPa for 180 s. The high pressure processing can be performed in batch or continuous mode, and the pressure conducting medium is water and the water level is higher than the bag.

[0010] In another aspect, the present application also provides a stabilized rice aleuronate slurry prepared by the above method. Preferably, the product meets all the following detectable indicators: residual lipase activity ≤ 7%; α-tocopherol retention rate ≥ 87%; GPC retention rate ≥ 89%; total bacterial count < 100 CFU / g, no detection of coliform group, mold and yeast after 12 weeks of storage at room temperature; acid value is 20-30 mg KOH / 100 g.

[0011] In yet another aspect, the stabilized rice aleuronate slurry is used to prepare food, including but not limited to instant cereal products, solid beverages, beverages (including plant-based beverages), baked products, snack foods, meal replacement powders, plant dietary fiber products, and rice products, which can be used as a base for plant-based beverages or as a nutritional functional ingredient added to the above-mentioned foods.

[0012] Compared with the processing route using only high frequency ultrasonic or only high pressure, the present application exhibits synergistic and threshold characteristics when the bagging capacity is ≤ 80%, the air is exhausted after filling, and the processing is performed in the fixed order of "high frequency ultrasonic first, then high pressure" in the pressure-time window around 600 MPa x 180 s: sufficient enzyme inactivation is achieved under low heat history conditions, while the higher retention of heat-sensitive active ingredients such as α-tocopherol and GPC is also considered, and the above microbiological and acid value criteria are met after 12 weeks of storage at room temperature; if any key condition is missing or exceeds, it is difficult to achieve the comprehensive effect, indicating that the order constraint, bagging and air exhaust control, and pressure-time window are necessary process conditions, which are suitable for batch or continuous industrial scale-up.

[0013] Unless otherwise stated, the percentage is by mass; the temperature is in °C, the pressure is in MPa, the time is in s, and the acid value is in mg KOH / 100 g. Any preferred value within the above range and combinations thereof constitute optional embodiments of the present application.

[0014] Beneficial effects Compared with the treatment route using only high-frequency ultrasound or only ultra-high pressure, the present application presents significant synergy and threshold characteristics in the fixed order of "high-frequency ultrasound first and then ultra-high pressure" at a pressure-time window of about 600 MPa x 180 s under the conditions of bag filling capacity ≤ 80% and air exhaust after filling. The parameter window is clear, detectable and suitable for industrial replication, while considering enzyme inactivation, active ingredient retention and room temperature shelf stability under low heat history. The specific performance is as follows: (1) Sufficient enzyme inactivation: Under the preferred window conditions, the residual lipase activity of rice paste slurry is ≤ 7%, and the representative condition is about 6.5%. If any unit is missing or the order is changed, the residual enzyme will significantly increase, which is difficult to meet the stabilization requirements.

[0015] (2) Higher retention of active ingredients: The retention rates of α-tocopherol and other heat-sensitive active ingredients such as γ-oryzanol are ≥ 87% and ≥ 89%, respectively, which maintains key nutritional activity while reducing heat history.

[0016] (3) Shelf and hygiene stability: After 12 weeks of storage at room temperature, the total number of colonies is < 100 CFU / g, and no coliform bacteria, mold and yeast are detected; the acid value is stably maintained at 20-30 mg KOH / 100 g. The above indexes are consistent with product criteria, which reflects the shelf stability of the system.

[0017] (4) Threshold and necessary process conditions: The non-linear inflection point of the pressure-time relationship appears near 600 MPa x 180 s; when the bag filling capacity is > 80% or the air is not exhausted, the residual enzyme significantly increases or the bag expands / explodes; any change in the order of "high-frequency ultrasound → ultra-high pressure" makes it difficult to meet the comprehensive indicators, indicating that the order constraint, bag filling and air exhaust control, and the pressure-time window are necessary process conditions.

[0018] (5) Simple process and suitable for scaling up: The process consists of two units of high-frequency ultrasound and ultra-high pressure, with water as the pressure transmission medium, and the bag and equipment are both conventional and available, with controllable energy consumption and modification cost. The stable production can be realized in batch or continuous mode on the existing production line.

[0019] (6) Detectable and replicable: The product and process are defined by quantitative thresholds and detectable parameters (such as bag filling capacity, air exhaust, pressure and holding time, microorganisms and acid value indicators), which facilitate quality control and large-scale replication, and improve the stability and consistency of industrial implementation. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Comparison of lipase activity residual rate of examples and comparative examples; Figure 2 Comparison of α-tocopherol content and retention rate; Figure 3 Comparison of oryzanol content and retention rate; Figure 4 Acid value-time curve under accelerated storage conditions (1-untreated; 2-high frequency ultrasound only; 3-ultra-high pressure only; 4-high frequency ultrasound followed by ultra-high pressure); Figure 5 Effect of different water addition amounts on lipase activity residual rate. DETAILED DESCRIPTION

[0021] The following examples are used to illustrate the present application, and are intended to show representative process parameters and test results, not to limit the present application. Unless otherwise specified, percentages are mass percentages (%), temperatures are in °C, pressures are in MPa, and times are in s; test items and methods are performed according to the description in “Test Methods and Statistics”, and “not detected” in microbiology means below the method detection limit. Test methods use national standards or their verified equivalent methods, as follows: (1) Lipase activity According to the current version of GB / T 5523 or its verified equivalent method. The result is expressed in relative residual rate (%), and the calculation formula is: Relative residual rate (%) = 100 × (activity value after treatment / initial activity value).

[0022] (2) α-tocopherol and oryzanol (HPLC) Determined using the high performance liquid chromatography conditions (chromatographic column, mobile phase, detection wavelength, flow rate, etc.) specified in the current version of GB 29942. Agilent 1260 or an HPLC system with equivalent performance can be used. The result is expressed in retention rate (%), and the calculation formula is: Retention rate (%) = 100 × (content after treatment / initial content).

[0023] (3) Acid value / fatty acid value Determined according to the current version of GB / T 5510 or its verified equivalent method. Acid value is expressed in mg KOH / 100 g; fatty acid value is expressed in units and conversion method according to the corresponding standard.

[0024] (4) Microbiological examination According to the current version of GB 4789 series standards: - Total number of colonies: GB 4789.2 (current version); - Coliforms: GB 4789.3 (current version); - Moulds and yeasts: GB 4789.15 (current version).

[0025] “Not detected” in the results is determined according to the respective method and the detection limit.

[0026] (5) Treatment and equipment High hydrostatic pressure treatment (HPP) uses equipment with a maximum working pressure ≥ 600 MPa (such as HPP-600 or equivalent equipment), with water as the pressure transmission medium and ensuring that the water level is above the bag; the model and key parameters (frequency, power, temperature, time) of the ultrasonic treatment device are as described in the examples, but are not limited to specific brands and models, and performance equivalent devices can also be used.

[0027] (6) Statistical analysis and data presentation Each group of experiments uses independent repeats n ≥ 3; if there are technical repeats, they are marked separately. First, perform the Shapiro-Wilk normality test and the Levene variance homogeneity test; when both are satisfied, use the two-tailed t-test or one-way ANOVA; for multiple group post-hoc comparisons, use the Tukey HSD method or the Dunnett method (compared with the control). When either normality or variance homogeneity is not satisfied, use non-parametric methods: two-group comparisons use the Mann-Whitney U test (also known as the Wilcoxon rank-sum test), and multiple-group comparisons use the Kruskal-Wallis H test, and perform Dunn-Bonferroni correction as needed. When the variance is not homogeneous but approximately normal, use Welch-corrected ANOVA, and use the Games-Howell method for post-hoc comparisons. The significance level a = 0.05 (two-sided); p < 0.05 is considered to be statistically significant. The results are expressed as mean ± standard deviation (x̄ ± s), and 95% confidence intervals can be given, with sample size n placed in the figure / table notes.

[0028] Example 1 Sample and conditions: weigh 5000 g of rice paste powder components, add 35% water, pass through a colloid mill with a mesh size of 80 to obtain a rice paste powder slurry; sample No. S3 is treated in the order of “high-frequency ultrasound → ultra-high pressure”. The control samples are Comparative Example 1 (high-frequency ultrasound only) and Comparative Example 2 (ultra-high pressure only).

[0029] Process parameters: high-frequency ultrasound 25 kHz, 800 W, 60 ℃, 180 s; the treated paste was filled into a 10 L pressure-resistant polyethylene bag, with 8 L (80%) of the bag filled, and the bag was sealed after air was exhausted; water was used as the pressure transmission medium and the bag was submerged, and the ultra-high pressure treatment was performed at 600 MPa for 180 s.

[0030] Results: the residual lipase activity of sample S3 was about 6.5% (see Figure 1 ), the retention rate of α-tocopherol was ≥ 87%, and the retention rate of oryzanol was ≥ 89% (see Figures 2-3 ). After 12 weeks of storage at room temperature, the total number of colonies was < 100 CFU / g, and the coliform bacteria / mold / yeast were not detected (see Table 1); under the accelerated storage condition, the acid value was maintained at 20-30 mg KOH / 100 g (see Figure 4 ).

[0031] Table 1 Microbial detection results of the sample of Example 1 after 12 weeks of storage Comparative Example 1 (only high-frequency ultrasound) Conditions: except that the ultra-high pressure treatment was omitted, the other conditions were the same as in Example 1.

[0032] Results: the residual lipase activity was about 78.2%, and the bag swelled at the 4th week of storage at room temperature (see Figure 1 , Figure 4 ).

[0033] Comparative Example 2 (only ultra-high pressure) Conditions: except that the high-frequency ultrasound treatment was omitted, the other conditions were the same as in Example 1.

[0034] Results: the residual lipase activity was about 31.4%, and the bag swelled at the 7th week of storage at room temperature (see Figure 1 , Figure 4 ).

[0035] Example 2 (influence of water addition amount) Under the condition that the water addition amount was set to 25%, 30%, 35%, 40%, and 45% (based on the mass of the rice paste components), the other conditions were the same as in Example 1.

[0036] Results: when the water addition amount was 25%, the material viscosity was high, and it was difficult to form a slurry; when the water addition amount was 30%, the residual enzyme was about 14.1%; when the water addition amount was 35%, the residual enzyme was about 7.3%; and when the water addition amount was in the range of 40%-45%, there was no significant change (see Figure 5 ). In combination with the stabilization effect, water consumption, and energy consumption, the water addition amount of 35% was preferred, and the range of 30%-40% was set as a reasonable range.

[0037] Example 3 (pressure-time window) Under the same conditions as in Example 1, 9 groups of 500 / 550 / 600 MPa and 150 / 180 / 210 s were used for treatment, and the results are shown in Table 2.

[0038] Table 2 Effect of pressure and time on residual rate of lipase activity Results: The residual enzyme was about 22.1% at 500 MPa x 210 s, about 15.4% at 550 MPa x 210 s, and about 6.5% at 600 MPa x 180 s, and no significant change was observed when extended to 210 s (see Table 2).

[0039] Example 4 (high-frequency ultrasound orthogonal test) Factors and levels: frequency 25 / 30 / 35 kHz, power 800 / 850 / 900 W, temperature 50 / 55 / 60 ℃, time 120 / 150 / 180 s; the results are shown in Table 3.

[0040] Table 3 High-frequency ultrasound orthogonal experiment and results (temperature > time > frequency > power) Analysis results: According to the range R (R = max(k) - min(k), k is the average value of the index at the same level of each factor) in Table 3, the factors are in the order of temperature > time > frequency > power; the preferred combination is 25 kHz, 800 W, 60 ℃, and 180 s.

[0041] Example 5 (bagging capacity and exhaust) The bagging capacity was set to 70 / 75 / 80 / 85 / 90 / 95%, and the "exhaust" (yes / no) factor was set, and the results are shown in Table 4.

[0042] Table 4 Effect of bagging capacity and exhaust on residual rate of lipase activity Results: When the bagging capacity was ≤80% and the air was exhausted, the residual enzyme was 6.5%-6.9%; when the bagging capacity was ≥85%, the residual enzyme increased; and under the condition of bagging capacity 80% and no exhaust, bag breaking occurred (data invalid). Therefore, the preferred control is that the bagging capacity is not more than 80% and the air is exhausted after filling.

[0043] Storage stability test (12 weeks) The sample of Example 1 was subjected to accelerated storage (40°C, 75% relative humidity) for 12 weeks: total number of colonies <100 CFU / g, no detection of coliform bacteria / mold / yeast (see Table 1); the acid value remained between 20 and 30 mg KOH / 100 g (see Table 2). Figure 4 ].

[0044] Industrial applicability The method consists of two units of high-frequency ultrasound and ultra-high pressure, the parameter window is 500-650 MPa, 100-300 s (preferably 600 MPa, 180 s), the bagging capacity is not more than 80%, and the air is exhausted after filling. This process is suitable for batch or continuous amplification, and the obtained rice flour slurry can be used as a plant-based beverage base or functional ingredient in related foods.

Claims

1. A processing method for stabilizing rice paste slurry, characterized in that, Includes the following steps: (1) Pulping: Mix the rice paste powder components with water to make the water content 30% to 40% based on the rice paste powder components, and process it with a colloid mill to obtain a solid particle size of 70 to 100 mesh to obtain rice paste powder slurry. (2) High-frequency ultrasonic treatment: The rice paste slurry is treated at a frequency of 20-40 kHz, a power of 500-1000 W, and a temperature of 50-100 °C for 60-300 s; (3) Filling and venting: Fill the pressure-resistant polyethylene bag with rice paste powder treated by high frequency ultrasound, so that the bag volume is 50% to 80% of the bag volume, and seal the bag after venting all the air inside. (4) Ultra-high pressure treatment: The sealed bag is placed in the ultra-high pressure treatment chamber, with water as the pressure transmission medium and the water level submerged above the bag body, and maintained at 500-650MPa for 100-300s; The above steps are performed in the order described above, that is, high-frequency ultrasonic treatment is followed by ultra-high pressure treatment.

2. The method according to claim 1, wherein, The amount of water added in step (1) is 35%.

3. The method according to claim 1, wherein, The preferred particle size for the colloid milling process in step (1) is 80 mesh.

4. The method according to claim 1, wherein, In step (2), the preferred parameters for high-frequency ultrasound are 25kHz, 800W, 60℃, and 180s.

5. The method according to claim 1, wherein, The volume of the polyethylene bag mentioned in step (3) is 5 to 15 L, and the bag capacity does not exceed 80%.

6. The method according to claim 1, wherein, In step (3), it is necessary to purge the air from the bag.

7. The method according to claim 1, wherein, The preferred parameters for ultra-high pressure treatment in step (4) are 600 MPa for 180 s.

8. The method according to claim 1, wherein, In step (4), the pressure transmission medium is water, and the water level is above the bag.

9. The method according to claim 1, wherein, The ultra-high pressure treatment described in step (4) is carried out in batches or continuously.

10. The method according to claim 1, characterized in that, The stabilized rice paste obtained by this method meets all of the following indicators when stored at room temperature for 12 weeks: lipase activity residue ≤7%; α-tocopherol retention rate ≥87%; oryzanol retention rate ≥89%; total bacterial count <100 CFU / g; no coliform bacteria, molds and yeasts detected; acid value 20-30 mg KOH / 100g.

11. A stabilized rice paste slurry, characterized in that: Lipase activity residue ≤7%; α-tocopherol retention rate ≥87%; oryzanol retention rate ≥89%; total bacterial count <100 CFU / g after 12 weeks of storage at room temperature; no coliform bacteria, molds and yeasts detected; acid value 20-30 mg KOH / 100g.

12. The stabilized rice paste slurry according to claim 11, characterized in that... It is prepared by the method described in any one of claims 1 to 9.

13. The use of the stabilized rice paste slurry according to claim 11 or 12 in the preparation of food, wherein the food includes instant cereal products, solid beverages, beverages (including plant-based beverages), baked goods, snack foods, meal replacement powders, plant dietary fiber products and rice and flour products.

14. The use according to claim 13, wherein, The stabilized rice paste can be used as a base for plant-based beverages or added to the food as a nutritional functional ingredient.

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