Preparation method of banana resistant starch

Abstract

The invention provides a preparation method of banana resistant starch, and belongs to the technical field of food processing. The method comprises the following steps: (1) pretreatment, (2) soaking with a composite color fixative, (3) pulping, (4) enzymatic modification, (5) ultrasonic annealing treatment and (6) spray drying. According to the method, amylosucrase branched chain extension modification is combined with ultrasonic-microwave synergistic treatment and a metal chelating color protection technology, so that the preparation method with high resistant starch yield and high-activity component retention is realized, and the application of the method in low-glycemic-index food is realized.

Description

Technical field

[0001] The invention relates to the technical field of food processing, and in particular to a method for preparing banana resistant starch. [Background Technology]

[0002] Resistant starch (RS) refers to starch and its degradation products that cannot be digested in the small intestine but can be fermented and utilized by the coliform flora in the colon. RS in food can be divided into four categories: RS1, physically embedded starch; RS2, resistant starch granules; RS3, retrograded starch; RS4, chemically modified starch. RS is similar to dietary fiber. It cannot be digested and absorbed in the small intestine and provide glucose. It can directly enter the large intestine and be fermented by physiological bacteria to produce a variety of short-chain fatty acids and gases. It has many physiological functions such as promoting the metabolism of cholesterol and blood lipids, controlling post-meal blood sugar levels, promoting mineral absorption, and controlling weight. In addition, resistant starch has good processing performance and is an important raw material for functional foods.

[0003] my country has abundant banana resources, but most of them are consumed fresh, resulting in a monotonous, processed product. Furthermore, due to limited transportation and preservation technologies, large quantities of bananas rot in production areas during harvest season, causing significant economic losses. my country's processing and utilization of this food resource is largely undeveloped. Among all fruit processing methods, banana processing is particularly underdeveloped, and current research methods for banana processing largely replicate those used for traditional fruits and vegetables. Bananas are rich in resistant starch granules (RS2), accounting for over 15% of their wet weight. Along with raw beans, raw potatoes, and aged amylose, they are ranked among the foods with the highest resistant starch content among common foods. Developing bananas as a starch resource is crucial for promoting the development of my country's banana processing industry.

[0004] Currently, there is little research on banana starch. Most studies focus on directly grinding and powdering green bananas after peeling and drying them. However, banana peels are rich in dietary fiber, polyphenols, and pectin, which can synergistically enhance the physiological functions of resistant starch (such as regulating intestinal flora and inhibiting sudden increases in blood sugar). In addition, the peel and flesh of green bananas are tightly bound together, and mechanical peeling results in a pulp loss rate of more than 15%. From these two perspectives, peeling will cause a certain degree of waste. If the peel is not peeled, the polyphenol oxidase (PPO) activity in the peel is high, and the browning rate during the pulping process is three times faster than that of the peeled flesh, resulting in a dark product color and deteriorated flavor. More importantly, the peel-on process hinders water evaporation due to the fiber, resulting in a low powder yield in spray drying.

[0005] Based on this, the present invention proposes a method for preparing banana resistant starch, which systematically solves the above bottlenecks and provides a new path for the deep processing of bananas. [Summary of the invention]

[0006] The present invention aims to provide a method for preparing banana resistant starch, which achieves a high yield of resistant starch and high retention of active ingredients through amylosucrase branch-chain extension modification combined with ultrasound-microwave synergistic treatment and metal chelation color protection technology, and its application in low glycemic index foods.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A method for preparing banana resistant starch, the method comprising the following steps:

[0009] (1) Pretreatment: After ultrasonic cleaning, the bananas were microwaved at 750-850W for 25-35s;

[0010] (2) Soaking in a composite color-protecting agent: Slice the pretreated bananas and then soak them in a metal chelate color-protecting solution for 15-25 minutes;

[0011] (3) beating: beating the soaked banana slices and passing them through a 0.4-0.5 mm sieve to obtain banana pulp;

[0012] (4) Enzymatic modification: Add amylosucrase to the banana pulp obtained in step (3) and react at 32-38°C for 20-25h;

[0013] (5) Ultrasonic annealing treatment: The product obtained in step (4) is subjected to ultrasonic annealing treatment, comprising: a. Ultrasonic stage: ultrasonic frequency is 38-42 kHz, power is 250-350 W, temperature is 54-56 ° C, and treatment time is 20-25 min; b. Annealing stage: maintaining temperature at 52-56 ° C, moisture content is 65-70%, and static treatment is performed for 20-25 h;

[0014] (6) Spray drying: The material obtained after ultrasonic annealing is spray dried to obtain the banana resistant starch.

[0015] In the present invention, further, the bananas are selected from green bananas with a maturity level of 2-3. The maturity grading standard is specifically based on "NY / T 3974-2021 Banana" (Ministry of Agriculture and Rural Affairs Industry Standard), which is divided into 7 levels according to the color of the peel (Level 1: dark green; Level 7: completely yellow with brown spots).

[0016] In the present invention, further, the ultrasonic cleaning further comprises adding an acidic detergent, and the acidic detergent comprises 0.2% citric acid and 0.05% sodium dodecyl sulfate.

[0017] In the present invention, further, the metal chelate color protection liquid contains the following components: L-ascorbic acid 0.4-0.6% (w / v), sodium phytate 0.08-0.12% (w / v), calcium chloride 0.03-0.07% (w / v), citric acid 0.15-0.25% (w / v) and zinc sulfate 0.02-0.04% (w / v).

[0018] In the present invention, further, the preparation method of the metal chelate color protection liquid is as follows: ascorbic acid is dissolved in 35-45°C water, stirred until completely transparent, the pH is adjusted to 3.3-3.7, and then sodium phytate, calcium chloride, citric acid and zinc sulfate are added in sequence, mixed thoroughly, filtered and sterilized to obtain the metal chelate color protection liquid (solid-liquid ratio is 1:1).

[0019] In the present invention, further, in step (4), the enzyme activity of amylosucrase is 0.15-0.25 U / g starch. Calculated based on an enzyme activity of 0.2 U / g starch, if banana pulp contains 70% starch, the amount of enzyme required to be added per 100 g pulp = 100 g × 70% × 0.2 U / g = 14 U.

[0020] In the present invention, further, the step (6) is specifically carried out by spray drying under the conditions of an air inlet temperature of 175-185°C and an air outlet temperature of 75-85°C.

[0021] In summary, due to the adoption of the above technical solution, the present invention has at least the following beneficial effects:

[0022] The present invention provides a method for preparing banana resistant starch. Through the "color protection-enzymatic method-ultrasonic annealing" technical chain, it realizes the high-yield and high-functional industrial production of green bananas with skin for the first time, filling the gap in the existing technology that cannot take into account "powder yield, nutrient retention, and cost control".

[0023] First, based on the risk of excessive pesticide residues in the processing of bananas with peels, the present invention uses an acidic environment + ultrasonic cavitation synergy, citric acid chelates heavy metals, and surfactants remove fat-soluble pesticide residues. Combined with the ultrasonic environment, a balance is achieved between removing pesticide residues and maintaining functions, thereby enhancing the food safety of the peel process.

[0024] Secondly, this invention utilizes ultrasound-microwave synergistic enzyme inactivation and metal chelation color protection technology to effectively address the browning and fiber clogging issues encountered during the processing of unpeeled green bananas, significantly increasing the yield of resistant starch and the retention of functional ingredients. Compared to traditional processes, this method not only achieves a higher flour yield but also significantly increases the content of resistant starch and dietary fiber, while retaining active substances such as polyphenols, giving the product enhanced health benefits.

[0025] Third, to address the two major industry challenges of fiber-impeded drying and polyphenol oxidation in the processing of unpeeled green bananas, this invention innovatively utilizes enzymatic branch extension and ultrasonic annealing to optimize process parameters, achieving effective fiber fragmentation and targeted restructuring of starch molecules. This technological approach not only overcomes the low yield of traditional unpeeled processes but also avoids reliance on costly equipment such as DBD, providing a viable solution for industrial production.

[0026] Fourthly, the present invention significantly reduces production energy consumption and equipment investment costs through the coordinated optimization of the color protection, enzymatic method, and ultrasonic annealing technology chain. Compared with traditional processes, the present invention achieves efficient production using conventional equipment, while shortening processing cycles, improving raw material utilization, and reducing waste generation, offering significant industrial advantages and economic benefits.

[0027] Fifth, the banana resistant starch prepared by the present invention has the characteristics of low glycemic index (GI) and high dietary fiber content, and can be widely used in low-GI foods (such as biscuits and bread) and functional packaging materials (such as edible films). Its excellent solubility and stability provide a new raw material option for the development of healthy foods, meeting consumers' dual needs for nutrition and functionality.

[0028] Overall, the present invention utilizes the entire banana fruit, reduces processing waste, and is in line with the concept of sustainable development. Furthermore, its low GI property provides a safer food option for people with metabolic diseases such as diabetes, offering both health benefits and environmental benefits. [Specific implementation method]

[0029] The following examples may help those skilled in the art to more fully understand the present invention, but shall not limit the present invention in any way.

[0030] Example 1:

[0031] This embodiment provides a method for preparing banana resistant starch, which comprises the following steps:

[0032] Step (1) Preprocessing:

[0033] Raw material selection and processing: Guijiao No. 6 (green fruit) with maturity level 3, washed with skin.

[0034] Ultrasonic cleaning: 38kHz ultrasound (equipment: KQ-500DE model) treatment for 8 minutes to remove surface wax (the epidermal contact angle decreased from 112° to 35° after cleaning); ultrasonic cleaning also included the addition of an acidic detergent containing 0.2% citric acid and 0.05% sodium lauryl sulfate;

[0035] Microwave inactivation: 750W treatment for 25s (measured pulp center temperature is 45℃), PPO enzyme activity residual rate ≤2%.

[0036] Step (2) Soaking in a composite color preservative:

[0037] Slice the pretreated bananas and immerse them in the metal chelate color protection solution for 15 minutes;

[0038] The color protection solution has the following formula: 0.4% (w / v) L-ascorbic acid, 0.08% (w / v) sodium phytate, 0.03% (w / v) calcium chloride, 0.15% (w / v) citric acid, and 0.02% (w / v) zinc sulfate. The metal chelate color protection solution is prepared by dissolving ascorbic acid in 35°C water, stirring until completely transparent, adjusting the pH to 3.3, then adding sodium phytate, calcium chloride, citric acid, and zinc sulfate in sequence, mixing thoroughly, and filtering to sterilize. The metal chelate color protection solution is obtained.

[0039] Step (3) beating:

[0040] The soaked banana slices were pulped using an IKAT25 high shear disperser at 2800 rpm for 3 min and passed through a 0.4 mm sieve. Fiber particle size: D50 = 8.0 μm as measured by a laser particle size analyzer.

[0041] Step (4) Enzymatic modification:

[0042] Add amylosucrase to the banana pulp obtained in step (3) with an enzyme activity of 0.15 U / g starch and react at 32° C. for 20-25 h;

[0043] Step (5) ultrasonic annealing:

[0044] a. Ultrasonic stage: ultrasonic frequency 38kHz, power 250W, temperature 54°C, treatment time 20min;

[0045] b. Annealing stage: maintain the temperature at 52°C, the moisture content at 65%, and allow to stand for 20 hours.

[0046] Step (6) spray drying:

[0047] Parameters: Inlet temperature: 175°C, outlet temperature: 75°C, atomizing disk speed: 18,000 rpm. After spray drying, the resulting banana resistant starch had a moisture content of 4.5%.

[0048] Example 2:

[0049] This embodiment provides a method for preparing banana resistant starch, which comprises the following steps:

[0050] Step (1) Preprocessing:

[0051] Raw material selection and processing: Guijiao No. 6 (green fruit) with maturity level 3, washed with skin.

[0052] Ultrasonic cleaning: 40 kHz ultrasound (equipment: KQ-500DE model) for 10 minutes to remove surface wax (the epidermal contact angle decreased from 112° to 35° after cleaning); ultrasonic cleaning also included the addition of an acidic detergent comprising 0.2% citric acid and 0.05% sodium lauryl sulfate;

[0053] Microwave inactivation: 800W treatment for 30s (measured pulp center temperature is 48°C), PPO enzyme activity residual rate ≤ 2%.

[0054] Step (2) Soaking in a composite color preservative:

[0055] Slice the pretreated bananas and immerse them in the metal chelate color protection solution for 20 minutes;

[0056] The color protection solution has the following formula: 0.5% (w / v) L-ascorbic acid, 0.1% (w / v) sodium phytate, 0.05% (w / v) calcium chloride, 0.2% (w / v) citric acid, and 0.03% (w / v) zinc sulfate. The metal chelate color protection solution is prepared by dissolving ascorbic acid in 40°C water, stirring until completely transparent, adjusting the pH to 3.5, then adding sodium phytate, calcium chloride, citric acid, and zinc sulfate in sequence, mixing thoroughly, and filtering to sterilize.

[0057] Step (3) beating:

[0058] The soaked banana slices were pulped using an IKAT25 high shear disperser at 2800 rpm for 3 min and passed through a 0.4 mm sieve. Fiber particle size: D50 = 8.5 μm as measured by a laser particle size analyzer.

[0059] Step (4) Enzymatic modification:

[0060] Add amylosucrase to the banana pulp obtained in step (3) with an enzyme activity of 0.2 U / g starch and react at 35° C. for 24 h;

[0061] Step (5) ultrasonic annealing:

[0062] a. Ultrasonic stage: ultrasonic frequency 40kHz, power 300W, temperature 55°C, treatment time 22min;

[0063] b. Annealing stage: maintain the temperature at 55°C, the moisture content at 68%, and allow to stand for 24 hours.

[0064] Step (6) spray drying:

[0065] Parameters: Inlet temperature: 180°C, outlet temperature: 80°C, atomizing disk speed: 18,000 rpm. After spray drying, the resulting banana resistant starch had a moisture content of 4.6%.

[0066] Example 3:

[0067] This embodiment provides a method for preparing banana resistant starch, which comprises the following steps:

[0068] Step (1) Preprocessing:

[0069] Raw material selection and processing: Guijiao No. 6 (green fruit) with maturity level 2, washed with skin.

[0070] Ultrasonic cleaning: 42 kHz ultrasound (equipment: KQ-500DE model) for 12 minutes to remove surface wax (the epidermal contact angle decreased from 112° to 35° after cleaning); ultrasonic cleaning also included the addition of an acidic detergent containing 0.2% citric acid and 0.05% sodium lauryl sulfate;

[0071] Microwave inactivation: 850W treatment for 35s (measured pulp center temperature is 45-50℃), PPO enzyme activity residual rate ≤2%.

[0072] Step (2) Soaking in a composite color preservative:

[0073] Slice the pretreated bananas and immerse them in the metal chelate color protection solution for 15-25 minutes;

[0074] The color protection solution has the following formula: 0.6% (w / v) L-ascorbic acid, 0.12% (w / v) sodium phytate, 0.07% (w / v) calcium chloride, 0.25% (w / v) citric acid, and 0.04% (w / v) zinc sulfate. The metal chelate color protection solution is prepared by dissolving ascorbic acid in 45°C water, stirring until completely transparent, adjusting the pH to 3.7, then adding sodium phytate, calcium chloride, citric acid, and zinc sulfate in sequence, mixing thoroughly, and filtering to sterilize.

[0075] Step (3) beating:

[0076] The soaked banana slices were pulped using an IKAT25 high shear disperser at 2800 rpm for 3 min and passed through a 0.5 mm sieve. Fiber particle size: D50 = 9.0 μm as measured by a laser particle size analyzer.

[0077] Step (4) Enzymatic modification:

[0078] Add amylosucrase to the banana pulp obtained in step (3) with an enzyme activity of 0.25 U / g starch and react at 38° C. for 25 h;

[0079] Step (5) ultrasonic annealing:

[0080] a. Ultrasonic stage: ultrasonic frequency 42kHz, power 350W, temperature 56°C, treatment time 25min;

[0081] b. Annealing stage: maintain the temperature at 56°C, the moisture content at 70%, and allow to stand for 25 hours.

[0082] Step (6) spray drying:

[0083] Parameters: Inlet temperature: 185°C, outlet temperature: 85°C, atomizing disk speed: 18,000 rpm. After spray drying, the resulting banana resistant starch had a moisture content of 4.9%.

[0084] Effect verification:

[0085] In order to illustrate the effect of this application, the applicant conducted the following experiments:

[0086] Experiment 1: Effect of microwave power on PPO inactivation

[0087] This experiment tested the effect of microwave power on PPO inactivation during the microwave enzyme inactivation stage. The results are shown in Table 1:

[0088] Table 1 Effect of microwave power on PPO inactivation

[0089] Power (W) Processing time (s) PPO residual activity (%) 700 30 12.5 800 30 1.8 900 30 0.5 (but starch gelatinization)

[0090] The test results show that 800W is the best balance point, taking into account both enzyme inactivation and starch structure preservation. Therefore, 800W was selected as the microwave power.

[0091] Experiment 2: Optimization of the amount of amylosucrase added

[0092] This experiment tested the effect of amylosucrase addition on RS content and flour yield. The results are shown in Table 2:

[0093] Table 2 Effect of the amount of amylosucrase added

[0094] Enzyme amount (U / g starch) RS content (%) Powder yield (%) 0.15 76.8 19.5 0.20 84.6 22.1 0.25 83.2 21.8

[0095] According to the test results, the RS yield was the highest (optimal economic efficiency) at 0.2 U / g starch.

[0096] Test 3: Product performance testing

[0097] Comparing the scoring rate and other indicators under different processes, the groups are as follows:

[0098] Traditional leather-on process: 0.5% VC is used for color protection instead of metal chelation system, amylosucrase treatment is skipped, and annealing is done by traditional heat conduction instead of ultrasound.

[0099] Peeling process: peeling the raw materials, adding maltodextrin, and spray drying;

[0100] The present invention group: banana resistant starch was prepared in the manner of Example 2;

[0101] The various indicators of banana resistant starch obtained from the above groups were compared, as shown in Table 3:

[0102] Table 3

[0103] index Traditional leather-skinning process (comparative example) Peeling process (traditional method) The present invention (skin optimization) Powder yield (%) 16.8 21.5 22.1 Dietary fiber content (%) 19.7 8.2 28.4 Polyphenol retention rate (%) 65 78 93

[0104] According to the results in Table 3, the skin-on process of the present invention solves the problem of low scoring rate in skin-on preparation and achieves a disruptive breakthrough. In addition, the process has high dietary fiber content and high polyphenol retention rate.

[0105] Experiment 4: Application Example

[0106] The prepared banana resistant starch was used in the preparation of low GI biscuits. The experimental group design is shown in Table 4 below:

[0107] Table 4

[0108]

[0109] Unified preparation process of low GI biscuits: mixing → molding → baking (170℃, 12min) → cooling.

[0110] After the biscuits were prepared, the glycemic characteristics of the biscuits in each group were compared. The results are shown in Table 5:

[0111] Table 5 Comparison of blood glucose production characteristics

[0112]

[0113] *Note: Blood glucose peak decrease rate = (control group peak value - experimental group peak value) / control group peak value × 100%.

[0114] The eGI value of the group of the present invention (determined by in vitro simulated digestion method) was 52.4, which was 23.5% lower than that of the peeling process group (68.5), reaching the clinical low GI standard (≤55); this is considered to be because the dietary fiber (28.4%) retained by the peeling process works synergistically with polyphenols to delay starch hydrolysis and achieve comprehensive health functions.

[0115] The above tests verified the synergistic effect of various technical features through multiple sets of comparative data, proving that:

[0116] (1) Feasibility of the process with skin: The flour yield of 22.1% is close to that of the process without skin (24.3%), but the dietary fiber content is significantly increased; (2) Necessity of critical parameter values: If the parameters such as microwave 800W and enzyme amount 0.2U / g starch are exceeded, the performance will be reduced; (3) Application advantages: The eGI value of the prepared low GI biscuits is 52.4, which meets the international standard (GI ≤ 55 is low glycemic).

[0117] Although the present invention has been described in detail above using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made based on the present invention. Therefore, such modifications and improvements, which do not depart from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. A method for preparing banana resistant starch, characterized in that: The method comprises the following steps: (1) Pretreatment: After ultrasonic cleaning, the bananas were microwaved at 750-850W for 25-35s; (2) Soaking in a composite color-protecting agent: Slice the pretreated bananas and then soak them in a metal chelate color-protecting solution for 15-25 minutes; (3) beating: beating the soaked banana slices and passing them through a 0.4-0.5 mm sieve to obtain banana pulp; (4) Enzymatic modification: Add amylosucrase to the banana pulp obtained in step (3) and react at 32-38°C for 20-25h; (5) Ultrasonic annealing treatment: The product obtained in step (4) is subjected to ultrasonic annealing treatment, comprising: a. Ultrasonic stage: ultrasonic frequency is 38-42 kHz, power is 250-350 W, temperature is 54-56 ° C, and treatment time is 20-25 min; b. Annealing stage: maintaining temperature at 52-56 ° C, moisture content is 65-70%, and static treatment is performed for 20-25 h; (6) Spray drying: The material obtained after ultrasonic annealing is spray dried to obtain the banana resistant starch.

2. The method according to claim 1, characterized in that The bananas are green bananas with a maturity level of 2-3.

3. The method according to claim 1, characterized in that The ultrasonic cleaning further comprises adding an acidic detergent, wherein the acidic detergent comprises 0.2% citric acid and 0.05% sodium lauryl sulfate.

4. The method according to claim 1, wherein The metal chelate color-protecting solution comprises the following components: 0.4-0.6% (w / v) L-ascorbic acid, 0.08-0.12% (w / v) sodium phytate, 0.03-0.07% (w / v) calcium chloride, 0.15-0.25% (w / v) citric acid and 0.02-0.04% (w / v) zinc sulfate.

5. The method according to claim 3, characterized in that The preparation method of the metal chelate color protection liquid is as follows: ascorbic acid is dissolved in 35-45°C water, stirred until completely transparent, the pH is adjusted to 3.3-3.7, and then sodium phytate, calcium chloride, citric acid and zinc sulfate are added in sequence, mixed thoroughly, filtered and sterilized to obtain the metal chelate color protection liquid.

6. The method according to claim 1, characterized in that In the step (4), the activity of amylosucrase is 0.15-0.25 U / g starch.

7. The method according to claim 1, characterized in that The step (6) is specifically carried out by spray drying under the conditions of an air inlet temperature of 175-185°C and an air outlet temperature of 75-85°C.

8. A low glycemic index food, characterized in that: The food contains banana resistant starch prepared by the method according to any one of claims 1 to 6.

9. A method for preparing a low glycemic index food using the banana resistant starch according to any one of claims 1 to 6, characterized in that: The method comprises adding banana resistant starch as a constituent raw material to the food, with the added amount being 20-30 wt %.

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