High-quality fried mulberry leaf pieces and methods of making the same

Abstract

The present application relates to a kind of fried mulberry leaf pieces and its preparation method.The preparation method of fried mulberry leaf pieces provided by the present application is that fresh mulberry leaf is first treated with acid aqueous solution containing citric acid and magnesium carbonate by pulse ultrasonic treatment, then soaked with aqueous solution containing spirulina extract and zinc gluconate, then the mulberry leaf treated by the specific pretreatment is subjected to cold fermentation by alternating temperature using lactobacillus rhamnosus and lactobacillus plantarum, and then combined with low-temperature plasma-assisted vacuum frying, which has significant effect of deodorization and green protection, and can significantly reduce the generation of harmful substances such as acrylamide during frying, effectively preserve bioactive substances such as polyphenols and flavonoids.The preparation method of fried mulberry leaf pieces provided by the present application can effectively remove grassy odor while the obtained fried mulberry leaf pieces have the advantages of green color, good flavor, less loss of active substances, less accumulation of harmful substances, low oil content, crisp and not greasy taste, etc.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, specifically relating to a fried mulberry leaf and its preparation method. Background Technology

[0002] Fried mulberry leaves, as a new type of ready-to-eat food, are gaining increasing attention and popularity in the market and among consumers due to the rich content of flavonoids, alkaloids, polysaccharides, polyphenols, and other active ingredients in mulberry leaves, which possess physiological functions such as lowering blood sugar, lowering blood lipids, and anti-oxidation. Currently, most fried mulberry leaves on the market are processed using traditional frying techniques, resulting in a crispy texture and unique flavor, thus possessing certain characteristics of a snack food.

[0003] However, in actual production and consumption, this product still faces several problems that urgently need to be addressed: First, mulberry leaves have a distinct grassy smell, which directly affects the product's flavor acceptance and palatability; second, during high-temperature processing, the chlorophyll in the leaves is easily destroyed, resulting in a dull and less vibrant green color in the finished product, affecting its appearance and consumer appeal; third, many heat-sensitive active substances in mulberry leaves (such as some flavonoids and polyphenols) are easily degraded and lost in the high-temperature frying environment, greatly reducing their nutritional and health benefits; in addition, traditional frying processes easily produce harmful substances such as acrylamide, and long-term intake may pose potential health risks.

[0004] Currently, to address these issues, the industry employs methods such as blanching, soaking in color-protecting agents, and adjusting frying temperature and time. However, these methods have limited effectiveness and often fail to simultaneously achieve the multiple objectives of deodorization, green color retention, preservation of active ingredients, and safety. For example, while high-temperature blanching can partially remove the fishy smell, it exacerbates chlorophyll destruction and loss of active substances; conventional color-protecting treatments may introduce chemical additives, which does not align with the consumer trend towards healthy eating. Therefore, exploring a new technology for processing fried mulberry leaves that can synergistically achieve efficient deodorization, significant color protection, maximum preservation of active ingredients, and inhibition of harmful substance formation has become an important development direction in this field. Summary of the Invention

[0005] Based on this, the purpose of this invention is to provide a new method for preparing fried mulberry leaves, so as to obtain fried mulberry leaves with bright green color, good flavor, less loss of active substances and less accumulation of harmful substances.

[0006] The technical solutions for achieving the above objectives include the following.

[0007] In one aspect, the present invention provides a method for preparing fried mulberry leaves, comprising the following steps:

[0008] (1) Pretreatment: Fresh mulberry leaves were ultrasonically treated in an aqueous solution containing citric acid and magnesium carbonate, and then the mulberry leaves were transferred to an aqueous solution containing spirulina extract and zinc gluconate for soaking.

[0009] (2) Variable temperature cold fermentation: Add Lactobacillus rhamnosus and Lactobacillus plantarum to the mulberry leaves treated in step (1), and pre-ferment at a temperature below 10℃ for 8-36 hours. Then transfer to a temperature of 20℃-30℃, add Lactobacillus rhamnosus and Lactobacillus plantarum, and continue fermentation for 1-3 days. After removing the liquid, add Lactobacillus rhamnosus and Lactobacillus plantarum again, and continue fermentation at a temperature of 10℃-25℃ for 1-3 days.

[0010] (3) Coating with powder and soaking in oil: After the mulberry leaves treated in step (2) are coated with powder and soaked in oil;

[0011] (4) Frying and degreasing: The mulberry leaves treated in step (3) are subjected to plasma treatment and vacuum frying in sequence to obtain fried mulberry leaves; the temperature of vacuum frying is 80℃-100℃.

[0012] Secondly, the present invention provides fried mulberry leaves prepared by the preparation method described in the present invention.

[0013] The present invention has the following beneficial effects:

[0014] The method for preparing fried mulberry leaves provided by this invention first involves treating fresh mulberry leaves with a pulsed ultrasonic solution containing citric acid and magnesium carbonate, then soaking them in an aqueous solution containing spirulina extract and zinc gluconate. Following this specific pretreatment, the mulberry leaves undergo variable-temperature cold fermentation with *Lactobacillus rhamnosus* and *Lactobacillus plantarum*, combined with plasma-assisted vacuum low-temperature frying. This method significantly removes the grassy smell and preserves the green color, while also significantly reducing the production of harmful substances such as acrylamide during frying and effectively preserving bioactive substances such as polyphenols and flavonoids. The method for preparing fried mulberry leaves provided by this invention effectively removes the grassy smell while resulting in fried mulberry leaves that are bright green, have a good flavor, minimal loss of active substances, low accumulation of harmful substances, low oil content, and a crispy, non-greasy texture. Attached Figure Description

[0015] Figure 1 Fried mulberry leaves prepared in Example 1. Detailed Implementation

[0016] To facilitate understanding of the present invention, a more complete description will be provided below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0017] Unless otherwise specified, experimental methods in the following examples are generally performed under standard conditions or as recommended by the manufacturer. All commonly used chemical reagents used in the examples are commercially available products.

[0018] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used in this invention includes any and all combinations of one or more of the associated listed items.

[0019] Furthermore, as used herein, the term "or" is an inclusive "or" sign and is equivalent to the term "and / or" unless the context clearly specifies otherwise. The term "based on" is not exclusive and allows for basing on other factors not described unless the context clearly specifies otherwise. Additionally, throughout the specification, the meanings of "an," "a," and "the" include plural indicators. The meaning of "in" includes both "in" and "on."

[0020] Some embodiments of the present invention relate to a method for preparing fried mulberry leaves, comprising the following steps:

[0021] (1) Pretreatment: Fresh mulberry leaves were ultrasonically treated in an aqueous solution containing citric acid and magnesium carbonate, and then the mulberry leaves were transferred to an aqueous solution containing spirulina extract and zinc gluconate for soaking.

[0022] (2) Variable temperature cold fermentation: Add Lactobacillus rhamnosus and Lactobacillus plantarum to the mulberry leaves treated in step (1), and pre-ferment at a temperature below 10℃ for 8-36 hours. Then transfer to a temperature of 20℃-30℃, add Lactobacillus rhamnosus and Lactobacillus plantarum, and continue fermentation for 1-3 days. After removing the liquid, add Lactobacillus rhamnosus and Lactobacillus plantarum again, and continue fermentation at a temperature of 10℃-25℃ for 1-3 days.

[0023] (3) Coating with powder and soaking in oil: After the mulberry leaves treated in step (2) are coated with powder and soaked in oil;

[0024] (4) Frying and degreasing: The mulberry leaves treated in step (3) are subjected to plasma treatment and vacuum frying in sequence to obtain fried mulberry leaves; the temperature of vacuum frying is 80℃-100℃.

[0025] In some embodiments, the concentration of citric acid in the aqueous solution containing citric acid and magnesium carbonate in step (1) is 2 g / L-6 g / L, and the concentration of magnesium carbonate is 0.5 g / L-3 g / L.

[0026] In some embodiments, the concentration of citric acid in the aqueous solution containing citric acid and magnesium carbonate in step (1) is 3 g / L-5 g / L, and the concentration of magnesium carbonate is 1 g / L-2 g / L.

[0027] In some embodiments, the concentration of citric acid in the aqueous solution containing citric acid and magnesium carbonate in step (1) is 3.5 g / L-4.5 g / L, and the concentration of magnesium carbonate is 1.2 g / L-1.8 g / L.

[0028] In some embodiments, the ratio of the aqueous solution containing citric acid and magnesium carbonate to fresh mulberry leaves is 15 mL-20 mL: 1 g.

[0029] In some embodiments, the ultrasonic treatment in step (1) is pulsed ultrasonic treatment.

[0030] In some embodiments, the process parameters of the pulsed ultrasound treatment include: power of 800W-1000W, temperature of 15℃-30℃, working for 3-8 seconds and stopping for 3-8 seconds, and total ultrasound time of 20s-40s.

[0031] In some embodiments, the concentration of spirulina extract in the aqueous solution containing spirulina extract and zinc gluconate in step (1) is 0.1 g / L-2 g / L, and the concentration of zinc gluconate is 2 g / L-30 g / L.

[0032] In some embodiments, the concentration of spirulina extract in the aqueous solution containing spirulina extract and zinc gluconate in step (1) is 0.4 g / L-0.8 g / L, and the concentration of zinc gluconate is 8 g / L-12 g / L.

[0033] In some embodiments, the mass ratio of the spirulina extract to zinc gluconate is 1:18-22.

[0034] In some embodiments, the ratio of the aqueous solution containing spirulina extract and zinc gluconate to fresh mulberry leaves is 9 mL-15 mL: 1 g.

[0035] In some embodiments, the soaking temperature in step (1) is 50°C-60°C and the soaking time is 5 min-10 min.

[0036] In some embodiments, the spirulina extract is a dried powder of spirulina aqueous extract.

[0037] In some embodiments, the preparation method of the spirulina extract includes: extracting spirulina powder with water, concentrating and drying the supernatant to obtain the extract.

[0038] In some embodiments, the ratio of the spirulina powder to water is 1g:20mL-40mL, preferably 1g:25mL-30mL.

[0039] In some embodiments, the water extraction is performed at a temperature of 30°C-50°C for a time of 0.5h-2h.

[0040] In some embodiments, the variable-temperature cold fermentation includes: adding Lactobacillus rhamnosus and Lactobacillus plantarum to the mulberry leaves treated in step (1), pre-fermenting at a temperature of 2℃-4℃ for 20-28 hours, then transferring to a temperature of 23℃-27℃, adding Lactobacillus rhamnosus and Lactobacillus plantarum, fermenting for 45-50 hours, removing the liquid, adding Lactobacillus rhamnosus and Lactobacillus plantarum again, and continuing fermentation at a temperature of 15℃-20℃ for 45-50 hours.

[0041] In some embodiments, the mass ratio of Lactobacillus rhamnosus to Lactobacillus plantarum added for the first time in step (2) is 1:2-4, preferably 1:2.5-3.5, and more preferably 1:3.

[0042] In some embodiments, the mass ratio of Lactobacillus rhamnosus to Lactobacillus plantarum added in step (2) is 1:3-6, preferably 1:4.5-5.5, and more preferably 1:5.

[0043] In some embodiments, the mass ratio of Lactobacillus rhamnosus to Lactobacillus plantarum added for the third time in step (2) is 1:2-4, preferably 1:2.5-3.5, and more preferably 1:3.

[0044] In some embodiments, the total mass of Lactobacillus rhamnosus and Lactobacillus plantarum added for the first time in step (2) is 0.5‰ to 2.0‰ of the mass of fresh mulberry leaves, preferably 0.8‰ to 1.2‰.

[0045] In some embodiments, the total mass of Lactobacillus rhamnosus and Lactobacillus plantarum added for the second time in step (2) is 0.3‰ to 0.5‰ of the mass of fresh mulberry leaves, preferably 0.38‰ to 0.42‰.

[0046] In some embodiments, the total mass of Lactobacillus rhamnosus and Lactobacillus plantarum added for the third time in step (2) is 0.3‰ to 0.5‰ of the mass of fresh mulberry leaves, preferably 0.38‰ to 0.42‰.

[0047] In some embodiments, the coating process in step (3) involves immersing the mulberry leaves treated in step (2) into a slurry made by uniformly mixing premixed powder and water at a mass ratio of 1:1.5-2.5. There are no special restrictions on the premixed powder used; any commonly used premixed powder (also known as composite coating base) for fried foods in the food industry can be used in this invention. For example, it can mainly consist of the following components: wheat flour, starch, gluten, edible salt, white sugar, leavening agents (sodium bicarbonate, calcium dihydrogen phosphate), emulsifiers, and disodium nucleotides, etc.; wherein the weight percentage of wheat flour can be 60%-65%, starch 28-32%, gluten 4-6%, and the remainder being other auxiliary materials.

[0048] In some embodiments, the oil in step (3) is a mixture of lemongrass oil, sesame oil and soybean oil in a mass ratio of 1:0.8-1.2:6-10.

[0049] In some embodiments, the soaking time in step (3) is 0.5 min to 2 min.

[0050] In some embodiments, the vacuum frying temperature in step (4) is 85°C-95°C.

[0051] In some embodiments, the vacuum degree of the vacuum frying in step (4) is –0.085 MPa to –0.098 MPa.

[0052] In some embodiments, the vacuum frying time in step (4) is 1 min to 3 min.

[0053] In some embodiments, the plasma generator for plasma treatment in step (4) operates at a frequency of 25Hz-75Hz, preferably 40Hz-60Hz.

[0054] In some embodiments, the plasma treatment lasts for 5 to 10 seconds.

[0055] Some embodiments of the present invention also involve fried mulberry leaves prepared by the preparation method described in the present invention.

[0056] The present invention will be further described in detail below with reference to specific embodiments.

[0057] The citronella oil, sesame oil, and soybean oil used in the following examples are all commercially available products; the mulberry leaves used are the leaves of Yue Sang No. 11, numbered 1-3; the strain number of Lactobacillus rhamnosus used is BNCC186192, and the strain number of Lactobacillus plantarum used is GDMCC1.191.

[0058] The spirulina extract used in the following examples is a water-soluble spirulina extract, and its preparation method is as follows:

[0059] Spirulina powder was extracted at 40°C for 1 hour with water at a ratio of 1 g powder to 28 mL water. The supernatant was collected by centrifugation, concentrated by rotary evaporation, spray-dried, crushed and sieved (60 mesh) to obtain spirulina extract.

[0060] The premixed powder used in the following examples consists of: 62% wheat flour, 30% starch, 5% wheat gluten, and 3% edible salt, white sugar, leavening agents (sodium bicarbonate, calcium dihydrogen phosphate), emulsifiers, and disodium inosinate, etc.

[0061] In the following examples, "liquid-solid ratio" refers to the volume-to-mass ratio, in mL:g. For example, "liquid-solid ratio 18:1" means that 18 mL of liquid contains 1 g of solid.

[0062] Example 1

[0063] The method for preparing fried mulberry leaves provided in this embodiment is as follows:

[0064] (1) Pretreatment of mulberry leaves: Fresh mulberry leaves after harvesting and sorting were subjected to pulsed ultrasonic treatment in an aqueous solution containing food-grade citric acid (4 g / L) and magnesium carbonate (1.5 g / L) (room temperature 25℃, power 900W, liquid-solid ratio 18:1, working for 5s, stopping for 5s, repeated 3 times, total time 30s). Then, the mulberry leaves were transferred to an aqueous solution containing 0.5 g / L spirulina extract and 10 g / L zinc gluconate at a liquid-solid ratio of 10:1. After stirring evenly, the solution was maintained at 55℃ for 8 min.

[0065] (2) Variable temperature cold fermentation: Add Lactobacillus rhamnosus and Lactobacillus plantarum in a mass ratio of 1:3 (the total mass of bacteria is 1‰ of the mass of mulberry leaves) to the mulberry leaves after treatment in step (1), place them in a cold storage at 2℃–4℃ for pre-fermentation for 24 hours, then transfer them to room temperature (25℃), add Lactobacillus rhamnosus and Lactobacillus plantarum in a mass ratio of 1:5 (the total mass of bacteria is 0.4‰ of the mass of mulberry leaves), ferment for 48 hours, remove the liquid, add Lactobacillus rhamnosus and Lactobacillus plantarum in a mass ratio of 1:3 (the total mass of bacteria is 0.4‰ of the mass of mulberry leaves), and continue fermentation at 15℃–20℃ for 48 hours.

[0066] (3) Coating with powder and soaking in oil: After fermentation, the mulberry leaves are soaked in a slurry made of premixed powder and water in a mass ratio of 1:2 for coating with powder and then soaked in a mixture of lemongrass oil, sesame oil and soybean oil in a mass ratio of 1:1:8 for 1 min.

[0067] (4) Plasma-assisted vacuum frying: Mulberry leaves coated with slurry and soaked in oil are laid flat between parallel plates of the plasma generator electrode (the working frequency of the plasma generator (Cpcs-1) is 50Hz). After 8 seconds, they are placed in a low-temperature vacuum frying system for frying to obtain fried mulberry leaves. The frying conditions are: temperature 90℃, vacuum degree –0.09 MPa, time 2min. This process does not require an additional deoiling step to obtain fried mulberry leaves with low oil content and can effectively inhibit the formation of harmful substances such as acrylamide.

[0068] Example 2

[0069] The difference between the method for preparing fried mulberry leaves provided in this embodiment and that in embodiment 1 is that the concentration of citric acid in the aqueous solution containing citric acid and magnesium carbonate in step (1) is 2 g / L and the concentration of magnesium carbonate is 0.5 g / L, while the other treatments are the same as in embodiment 1.

[0070] Example 3

[0071] The difference between the method for preparing fried mulberry leaves provided in this embodiment and that in embodiment 1 is that the concentration of citric acid in the aqueous solution containing citric acid and magnesium carbonate in step (1) is 6 g / L and the concentration of magnesium carbonate is 3 g / L, while the other treatments are the same as in embodiment 1.

[0072] Example 4

[0073] The difference between the method for preparing fried mulberry leaves provided in this embodiment and that in embodiment 1 is that the concentration of spirulina extract in the aqueous solution containing spirulina extract and zinc gluconate in step (1) is 0.1 g / L and the concentration of zinc gluconate is 2 g / L, while the other treatments are the same as in embodiment 1.

[0074] Example 5

[0075] The difference between the method for preparing fried mulberry leaves provided in this embodiment and that in embodiment 1 is that the concentration of spirulina extract in the aqueous solution containing spirulina extract and zinc gluconate in step (1) is 1.8 g / L and the concentration of zinc gluconate is 30 g / L, while the other treatments are the same as in embodiment 1.

[0076] Example 6

[0077] The difference between the method for preparing fried mulberry leaves provided in this embodiment and that in embodiment 1 is that the mass ratio of Lactobacillus rhamnosus to Lactobacillus plantarum added in step (2) is 1:2 for the first time, 1:3 for the second time, and 1:2 for the third time. Other treatments are the same as in embodiment 1.

[0078] Example 7

[0079] The difference between the method for preparing fried mulberry leaves provided in this embodiment and that in embodiment 1 is that the mass ratio of Lactobacillus rhamnosus to Lactobacillus plantarum added in step (2) is 1:4 for the first time, 1:6 for the second time, and 1:4 for the third time. Other treatments are the same as in embodiment 1.

[0080] Example 8

[0081] The difference between the method for preparing fried mulberry leaves provided in this embodiment and that in embodiment 1 is that the total mass of Lactobacillus rhamnosus and Lactobacillus plantarum added in step (2) is as follows: 0.5‰ for the first time, 0.3‰ for the second time, and 0.3‰ for the third time. Other treatments are the same as in embodiment 1.

[0082] Example 9

[0083] The difference between the method for preparing fried mulberry leaves provided in this embodiment and that in embodiment 1 is that the total mass of Lactobacillus rhamnosus and Lactobacillus plantarum added in step (2) is 2.0‰ for the first time, 0.5‰ for the second time, and 0.5‰ for the third time. Other treatments are the same as in embodiment 1.

[0084] Comparative Example 1

[0085] The method for preparing fried mulberry leaves provided in this comparative example is as follows:

[0086] (1) Take the sorted fresh mulberry leaves and soak them in ordinary water for 30 seconds (without adding citric acid and magnesium carbonate, without pulse ultrasound treatment, and without treatment with an aqueous solution containing spirulina extract and zinc gluconate).

[0087] Steps (2), (3) and (4) are the same as in Example 1.

[0088] Comparative Example 2

[0089] The preparation method of fried mulberry leaves provided in this comparative example is as follows (citric acid and magnesium carbonate were not added during pulsed ultrasonic treatment):

[0090] (1) Take the sorted fresh mulberry leaves and perform pulsed ultrasonic treatment in clean water (power 900W, liquid-solid ratio 18:1, work for 5s, stop for 5s, cycle 3 times, total time 30s). Then transfer the mulberry leaves to an aqueous solution containing 0.5 g / L spirulina extract and 10 g / L zinc gluconate at a liquid-solid ratio of 10:1. Stir evenly and maintain at 55℃ for 8 min.

[0091] Steps (2), (3) and (4) are the same as in Example 1.

[0092] Comparative Example 3

[0093] The preparation method of fried mulberry leaves provided in this comparative example is as follows (citric acid was not added during pulsed ultrasonic treatment):

[0094] (1) Take the sorted fresh mulberry leaves and perform pulsed ultrasonic treatment in an aqueous solution containing magnesium carbonate (1.5 g / L) (power 900W, liquid-solid ratio 18:1, working for 5s, stopping for 5s, cycled 3 times, total time 30s). Then transfer the mulberry leaves to an aqueous solution containing 0.5 g / L spirulina extract and 10 g / L zinc gluconate at a liquid-solid ratio of 10:1. After stirring evenly, maintain at 55℃ for 8min.

[0095] Steps (2), (3) and (4) are the same as in Example 1.

[0096] Comparative Example 4

[0097] The preparation method of fried mulberry leaves provided in this comparative example is as follows (magnesium carbonate was not added during pulsed ultrasonic treatment):

[0098] (1) Take the sorted fresh mulberry leaves and perform pulsed ultrasonic treatment in an aqueous solution containing food-grade citric acid (4 g / L) (power 900W, liquid-solid ratio 18:1, working for 5s, stopping for 5s, cycled 3 times, total time 30s). Then, transfer the mulberry leaves to an aqueous solution containing 0.5 g / L spirulina extract and 10 g / L zinc gluconate at a liquid-solid ratio of 10:1. After stirring evenly, maintain at 55℃ for 8min.

[0099] Steps (2), (3) and (4) are the same as in Example 1.

[0100] Comparative Example 5

[0101] The preparation method of fried mulberry leaves provided in this comparative example is as follows (replacing citric acid with acetic acid and magnesium carbonate with sodium carbonate):

[0102] (1) Take the sorted fresh mulberry leaves and perform pulsed ultrasonic treatment in an aqueous solution containing food-grade acetic acid (4 g / L) and sodium carbonate (1.5 g / L) (power 900W, liquid-solid ratio 18:1, working for 5s, stopping for 5s, cycled 3 times, total time 30s). Then, transfer the mulberry leaves to an aqueous solution containing 0.5 g / L spirulina extract and 10 g / L zinc gluconate at a liquid-solid ratio of 10:1. After stirring evenly, maintain at 55℃ for 8 min.

[0103] Steps (2), (3) and (4) are the same as in Example 1.

[0104] Comparative Example 6

[0105] The preparation method of fried mulberry leaves provided in this comparative example is as follows (without treatment with spirulina extract and zinc gluconate):

[0106] (1) Take the sorted fresh mulberry leaves and perform pulsed ultrasonic treatment in an aqueous solution containing food-grade citric acid (4 g / L) and magnesium carbonate (1.5 g / L) (power 900W, liquid-solid ratio 18:1, working for 5s, stopping for 5s, cycled 3 times, total time 30s).

[0107] Steps (2), (3) and (4) are the same as in Example 1.

[0108] Comparative Example 7

[0109] The preparation method of fried mulberry leaves provided in this comparative example is as follows (without treatment with zinc gluconate):

[0110] (1) Take the sorted fresh mulberry leaves and perform pulsed ultrasonic treatment in an aqueous solution containing food-grade citric acid (4 g / L) and magnesium carbonate (1.5 g / L) (power 900W, liquid-solid ratio 18:1, working for 5s, stopping for 5s, cycled 3 times, total time 30s). Then transfer the mulberry leaves to an aqueous solution containing 0.5 g / L spirulina extract at a liquid-solid ratio of 10:1, stir evenly, and maintain at 55℃ for 8min.

[0111] Steps (2), (3) and (4) are the same as in Example 1.

[0112] Comparative Example 8

[0113] The preparation method of fried mulberry leaves provided in this comparative example is as follows (without treatment with spirulina extract):

[0114] (1) Take the sorted fresh mulberry leaves and perform pulsed ultrasonic treatment in an aqueous solution containing food-grade citric acid (4 g / L) and magnesium carbonate (1.5 g / L) (power 900W, liquid-solid ratio 18:1, working for 5s, stopping for 5s, cycled 3 times, total time 30s). Then transfer the mulberry leaves to an aqueous solution containing 10 g / L zinc gluconate at a liquid-solid ratio of 10:1, stir evenly, and maintain at 55℃ for 8 min.

[0115] Steps (2), (3) and (4) are the same as in Example 1.

[0116] Comparative Example 9

[0117] The preparation method of fried mulberry leaves provided in this comparative example is as follows (replacing spirulina extract with an equal amount of dextrin):

[0118] (1) Take the sorted fresh mulberry leaves and perform pulsed ultrasonic treatment in an aqueous solution containing food-grade citric acid (4 g / L) and magnesium carbonate (1.5 g / L) (power 900W, liquid-solid ratio 18:1, working for 5s, stopping for 5s, cycled 3 times, total time 30s). Then transfer the mulberry leaves to an aqueous solution containing 0.5 g / L dextrin and 10 g / L zinc gluconate at a liquid-solid ratio of 10:1. After stirring evenly, maintain at 55℃ for 8 min.

[0119] Steps (2), (3) and (4) are the same as in Example 1.

[0120] Comparative Example 10

[0121] The preparation method of fried mulberry leaves provided in this comparative example is as follows (replacing zinc gluconate with an equal amount of CaCl2):

[0122] (1) Take the sorted fresh mulberry leaves and perform pulsed ultrasonic treatment in an aqueous solution containing food-grade citric acid (4 g / L) and magnesium carbonate (1.5 g / L) (power 900W, liquid-solid ratio 18:1, working for 5s, stopping for 5s, cycled 3 times, total time 30s). Then, transfer the mulberry leaves to an aqueous solution containing 0.5 g / L spirulina extract and 10 g / L CaCl2 at a liquid-solid ratio of 10:1. After stirring evenly, maintain at 55℃ for 8 min.

[0123] Steps (2), (3) and (4) are the same as in Example 1.

[0124] Comparative Example 11

[0125] The preparation method of fried mulberry leaves provided in this comparative example is as follows (constant temperature fermentation):

[0126] Step (1) is the same as in Example 1.

[0127] (2) Place the mulberry leaves treated in step (1) at a constant temperature of 10℃, add Lactobacillus rhamnosus and Lactobacillus plantarum in a mass ratio of 1:3 (the total mass of bacteria is 1‰ of the mass of mulberry leaves) and ferment for 24 hours. Then add Lactobacillus rhamnosus and Lactobacillus plantarum in a mass ratio of 1:5 (the total mass of bacteria is 0.4‰ of the mass of mulberry leaves) and ferment for 48 hours. After removing the liquid, add Lactobacillus rhamnosus and Lactobacillus plantarum in a mass ratio of 1:3 (the total mass of bacteria is 0.4‰ of the mass of mulberry leaves) and continue fermenting for 48 hours.

[0128] Steps (3) and (4) are the same as in Example 1.

[0129] Comparative Example 12

[0130] The difference between the preparation method of fried mulberry leaves provided in this comparative example and that in Example 1 is that only one type of Lactobacillus plantarum is added during the variable temperature cold fermentation process in step (2). The amount of bacteria added is the same as the total amount of the two bacteria in Example 1. Other treatments are the same as in Example 1.

[0131] Comparative Example 13

[0132] The difference between the preparation method of fried mulberry leaves provided in this comparative example and that in Example 1 is that only one type of Lactobacillus rhamnosus is added during the variable temperature cold fermentation process in step (2). The amount of bacteria added is the same as the total amount of the two bacteria in Example 1. Other treatments are the same as in Example 1.

[0133] Comparative Example 14

[0134] The method for preparing fried mulberry leaves provided in this comparative example differs from that in Example 1 in that, during step (2) of variable temperature cold fermentation, Lactobacillus plantarum is replaced with an equal amount of Lactobacillus bulgaricus, while the other treatments are the same as in Example 1.

[0135] Comparative Example 15

[0136] The method for preparing fried mulberry leaves provided in this comparative example differs from that in Example 1 in that, in step (2) during the variable-temperature cold fermentation process, Lactobacillus rhamnosus is replaced with an equal amount of Lactobacillus casei, while the other treatments are the same as in Example 1.

[0137] Comparative Example 16

[0138] The method for preparing fried mulberry leaves provided in this comparative example is as follows:

[0139] Steps (1), (2) and (3) are the same as in Example 1.

[0140] (4) Conventional deep frying: Place the mulberry leaves that have been coated with batter and soaked in oil in an oil pan under normal pressure and deep fry at 160°C for 2 minutes. Use a blower to remove any residual oil from the surface and let them cool. No plasma treatment is required.

[0141] Comparative Example 17

[0142] The method for preparing fried mulberry leaves provided in this comparative example is as follows:

[0143] Steps (1), (2) and (3) are the same as in Example 1.

[0144] (4) Vacuum low-temperature frying: The mulberry leaves, after being coated with batter and soaked in oil, are placed in a low-temperature vacuum frying system for frying to obtain fried mulberry leaves. The frying conditions are: temperature 90℃, vacuum degree -0.09 MPa, time 2min. No plasma treatment is required.

[0145] The fried mulberry leaves prepared in Examples 1-9 and Comparative Examples 1-17 were subjected to the following indicators and quality evaluations.

[0146] Determination of fat content: The fat content was determined according to the Soxhlet extraction method in GB 5009.6—2016, "National Food Safety Standard - Determination of Fat in Food". 2 g of fried mulberry leaf sample was weighed, dried, and then extracted with petroleum ether at a boiling range of 30℃~60℃ for 6 h. The sample was then dried at 105℃ to constant weight. The weights before and after defatting were recorded, and the fat content was calculated.

[0147] Acrylamide content determination: Acrylamide content was determined using HPLC-MS. 2 g of fried mulberry leaf sample was weighed into a 50 mL centrifuge tube, and... 13 C3-AA (250 μg / kg) internal standard was added, vortexed for 1 min, then 3 mL of ultrapure water was added. After standing for 20 min, 10 mL of acetonitrile was added, vortexed for 2 min, and centrifuged at 5000 r / min for 5 min. 5.0 mL of the supernatant was transferred to a 15 mL centrifuge tube containing the adsorbent and ultrapure water, vortexed for 1 min, and centrifuged at 5000 r / min for 5 min. 2 mL of the supernatant was transferred to a 10 mL glass test tube, and the volume was reduced to 0.5 mL by blowing with N2 in a 40 ℃ water bath. Then, 1.5 mL of ultrapure water was added to reconstitute the solution, vortexed for 30 s, filtered through a 0.22 μm aqueous filter membrane, and the filtrate was collected in a 1 mL vial for HPLC-MS analysis.

[0148] Polyphenol content determination: Gallic acid was used as a standard, and the polyphenol content in the sample was determined in accordance with GB / T 8313—2018.

[0149] Flavonoid content determination: Using rutin as a standard, the content of flavonoids in the sample was determined in accordance with NY / T 3903-2021.

[0150] Sensory evaluation: A panel of 16 people (8 men and 8 women, aged 22-35) with food-related backgrounds was selected and trained. Sensory evaluation was conducted on aspects such as appearance, color, flavor, texture and taste (see Table 1 for standards).

[0151] The test results are shown in Tables 2-4.

[0152] In Tables 2 and 3, dried mulberry leaves refer to fresh mulberry leaves that have been harvested and sorted and then directly placed in a heat pump dryer and dried at a temperature of 60-65℃ until the moisture content is less than 10%.

[0153] Tables 2-4 show the preparation methods for conventional fried mulberry leaves as follows: After harvesting and sorting, fresh mulberry leaves are directly coated with premixed powder (premixed powder to water mass ratio 1:2), then fried in conventional soybean oil at 150℃ for 1-2 minutes. The residual oil on the surface is blown off with a blower, and the leaves are cooled to obtain the final product.

[0154] Table 1 Sensory Rating Table

[0155]

[0156]

[0157] Table 2 Results of active substance content determination

[0158]

[0159]

[0160]

[0161]

[0162] Table 2 shows that the content of active substances such as polyphenols and flavonoids in the fried mulberry leaves prepared by the present invention (Examples 1-9) is significantly higher than that in conventional fried mulberry leaves. Under some preferred processes, the content of active substances in the fried mulberry leaves is comparable to, or even higher than, that in dried mulberry leaf samples that have not been fried.

[0163] Compared to Example 1, Examples 2-3 changed the concentrations of citric acid and magnesium carbonate in step (1). The concentrations of citric acid and magnesium carbonate in Example 2 were lower than in Example 1, resulting in a weaker color-protecting effect and a lower content of active substances in the fried mulberry leaves compared to Example 1. While Example 3 had higher concentrations of citric acid and magnesium carbonate, its effect was not superior to Example 1; on the contrary, the content of active substances in the fried mulberry leaves was slightly lower than in Example 1, which may be related to the change in the pH environment provided.

[0164] Spirulina extract and zinc gluconate work synergistically to resist pigment oxidation and also have a certain impact on the content of active substances in fried mulberry leaves. Compared with Example 1, Examples 4 and 5 changed the concentration of spirulina extract and zinc gluconate. The concentration of spirulina extract and zinc gluconate in Example 4 was lower than that in Example 1, resulting in a lower content of active substances in the mulberry leaves. However, the polyphenolic flavonoid content of the mulberry leaves obtained by Example 5, which further increased the concentration of spirulina extract and zinc gluconate, was comparable to that in Example 1.

[0165] Compared with Example 1, Examples 6-9 changed the ratio of the two probiotics and the amount of probiotics added. The results showed that if the mass ratio of Lactobacillus rhamnosus to Lactobacillus plantarum was too high or too low (Examples 6 and 7), or if the amount of bacteria added was too high or too low (Examples 8 and 9), it would have a certain impact on the content of active substances in fried mulberry leaves. Fermentation with Lactobacillus rhamnosus and Lactobacillus plantarum in the ratio and amount in Example 1 can produce fried mulberry leaves with a higher content of polyphenols and flavonoids.

[0166] Compared with Example 1, Comparative Example 1 did not add citric acid, magnesium carbonate, spirulina extract, zinc gluconate, or other substances, nor did it undergo pulsed ultrasonic treatment. As a result, the color-protecting effect during the treatment was very weak, and it could not protect the active substances. Therefore, the content of polyphenolic flavonoids in the fried mulberry leaves obtained was low.

[0167] Compared to Example 1, Comparative Examples 2-5, in which citric acid and magnesium carbonate were not added during the pulsed ultrasound treatment, or only one of them was added, or they were replaced with other components, all resulted in the loss of some polyphenolic flavonoid active substances, making the polyphenolic flavonoid content of the fried mulberry leaves significantly lower than that of Example 1. It is evident that only pulsed ultrasound treatment with the synergistic effect of citric acid and magnesium carbonate can protect the active substances and significantly increase the content of polyphenolic flavonoid active substances in mulberry leaves.

[0168] Compared to Example 1, Comparative Examples 6-10, without treatment with spirulina extract and zinc gluconate, or with only one of them, or by replacing them with other ingredients, all resulted in the loss of some polyphenolic flavonoid active substances, leading to a significantly lower content of polyphenolic flavonoids in the fried mulberry leaves compared to Example 1. This demonstrates that only with the synergistic treatment of spirulina extract and zinc gluconate can the active substances be better protected, significantly increasing the content of polyphenolic flavonoids in mulberry leaves.

[0169] Compared with Example 1, Comparative Example 11 had a different fermentation temperature. Example 1 was a variable temperature fermentation, while Comparative Example 11 was a constant temperature fermentation. The results showed that fermentation at the temperature of Example 1 was more conducive to the function of probiotics, thereby significantly increasing the content of polyphenols and flavonoids in mulberry leaves.

[0170] Compared with Example 1, Comparative Examples 12-15, using only one type of bacteria or replacing it with other bacteria, resulted in significantly lower polyphenol and flavonoid content in the obtained mulberry leaves compared to Example 1. This indicates that the fermentation of mulberry leaves with a specific ratio of Lactobacillus rhamnosus and Lactobacillus plantarum in this invention has a significant synergistic effect, which can significantly increase the content of polyphenol and flavonoid active substances in mulberry leaves.

[0171] Comparative Example 16 involved conventional frying without vacuum low-temperature treatment or plasma treatment. Although the same reagent treatment was performed as in Example 1, frying at high temperature was still not conducive to the retention of active substances, resulting in a significantly lower concentration of active substances in the mulberry leaves compared to Example 1.

[0172] Comparative Example 17, which did not undergo plasma treatment, had a lower content of polyphenols and flavonoids than Example 1, indicating that plasma-assisted frying can, to some extent, protect active substances such as polyphenols and flavonoids.

[0173] Table 3 Acrylamide content test results

[0174]

[0175]

[0176]

[0177] Table 4. Results of oil content test

[0178]

[0179] Tables 3 and 4 show that ordinary dried mulberry leaves, because they are not fried, have a very low oil content and produce very little acrylamide. Conventionally fried mulberry leaves, on the other hand, have higher acrylamide and oil contents; therefore, the acrylamide is mainly produced during the frying process. The fried mulberry leaves prepared according to this invention (Examples 1-9) have significantly lower acrylamide and oil contents than conventionally fried mulberry leaves, indicating that the preparation process of this invention can effectively inhibit the formation of harmful substances such as acrylamide while achieving efficient oil removal.

[0180] Compared with Example 1, Comparative Example 1 did not add citric acid, magnesium carbonate, spirulina extract, zinc gluconate, or other substances, nor did it undergo pulsed ultrasonic treatment. As a result, the color-protecting effect during the treatment was very weak, and it could not effectively protect the mulberry leaves, leading to a higher amount of acrylamide produced during the frying process.

[0181] Compared to Example 1, Comparative Examples 2-5 did not include citric acid and magnesium carbonate during the pulsed ultrasonic treatment, or only one of them was added, or they were replaced with other ingredients. Comparative Examples 6-10, compared to Example 1, did not use spirulina extract and zinc gluconate for treatment, or only one of them was added, or they were replaced with other ingredients. These modifications all resulted in an increase in the acrylamide content in the fried mulberry leaves compared to Example 1. This demonstrates that the preparation process of the present invention, involving pulsed ultrasonic treatment with the synergistic effect of citric acid and magnesium carbonate, combined with synergistic treatment using spirulina extract and zinc gluconate, effectively protects the active substances while significantly reducing the formation of acrylamide in mulberry leaves during frying.

[0182] Compared with Example 1, Comparative Example 11 had a different fermentation temperature. Example 1 was a variable temperature fermentation, while Comparative Example 11 was a constant temperature fermentation. The results showed that fermentation at the temperature of Example 1 was more conducive to the function of probiotics and could also reduce the production of acrylamide in mulberry leaves during frying to a certain extent.

[0183] Compared to Example 1, Comparative Examples 12-15, which used only one type of bacteria or replaced it with other bacteria, resulted in a slightly higher acrylamide content in the mulberry leaves compared to Example 1. This indicates that the fermentation of mulberry leaves with a specific ratio of Lactobacillus rhamnosus and Lactobacillus plantarum in this invention can also reduce the production of acrylamide in mulberry leaves during frying to a certain extent.

[0184] Comparative Example 16 was prepared by conventional frying without vacuum low temperature or plasma treatment. Although the same reagent treatment was performed as in Example 1, frying at normal pressure and high temperature still produced more harmful substances such as acrylamide and was not conducive to the removal of oil. As a result, the acrylamide and oil content of the mulberry leaves obtained were significantly higher than those in Example 1.

[0185] Compared to Example 1, Comparative Example 17 did not undergo plasma treatment, resulting in poorer surface fluidity of the mulberry leaves and a higher oil residue rate. Furthermore, Comparative Example 17 had a higher acrylamide content than Example 1, indicating that plasma-assisted frying can reduce acrylamide production in mulberry leaves during frying to some extent.

[0186] Table 5 Sensory Evaluation Results

[0187]

[0188]

[0189]

[0190] Table 5 shows that the fried mulberry leaves prepared by the present invention (Examples 1-9) have better taste, appearance, aroma and other sensory qualities than conventional fried mulberry leaves, with the fried mulberry leaves prepared in Example 1 having the best quality.

[0191] Compared with Example 1, Examples 2-3 changed the concentrations of citric acid and magnesium carbonate in step (1). The concentrations of citric acid and magnesium carbonate in Example 2 were lower than those in Example 1, resulting in a weaker color-protecting effect and thus a slightly worse color and appearance. In Example 3, the concentrations of citric acid and magnesium carbonate were higher, but the color-protecting effect was not better than that of Example 1; on the contrary, it was slightly worse than that of Example 1. This may be related to the change in the pH environment provided, and therefore the color and appearance were also slightly worse than those of Example 1.

[0192] Spirulina extract and zinc gluconate work synergistically to provide a "fresh and fragrant" base flavor, enriching the flavor profile, and also act as an anti-pigment oxidation agent, making them a green synergist. Compared to Example 1, Examples 4 and 5 changed the concentrations of spirulina extract and zinc gluconate. In Example 4, the concentrations of spirulina extract and zinc gluconate were lower than in Example 1, resulting in a relatively weaker effect. In Example 5, the concentrations of spirulina extract and zinc gluconate were higher, but the ratio of spirulina extract to zinc gluconate differed, and the amount of spirulina extract was slightly higher, resulting in a weaker synergistic effect compared to Example 1. This led to the mulberry leaves from Examples 4 and 5 having slightly inferior color, appearance, and taste compared to Example 1.

[0193] Compared with Example 1, Examples 6-9 changed the ratio of the two probiotics and the amount of probiotics added. The results showed that if the mass ratio of Lactobacillus rhamnosus to Lactobacillus plantarum was too high or too low (Examples 6 and 7), or if the amount of bacteria added was too high or too low (Examples 8 and 9), it would have a certain impact on the sensory properties of fried mulberry leaves. Fermentation with Lactobacillus rhamnosus and Lactobacillus plantarum in the ratio and amount in Example 1 can produce fried mulberry leaves with higher overall evaluation in terms of aroma, flavor, appearance and taste.

[0194] Compared with Example 1, Comparative Example 1 did not contain citric acid, magnesium carbonate, spirulina extract, zinc gluconate, or other substances, nor did it undergo pulsed ultrasonic treatment. Therefore, it did not have a significant color-protecting effect, and the resulting fried mulberry leaves had a lower overall evaluation score in terms of flavor, appearance, and taste.

[0195] Compared with Example 1, Comparative Example 11 had a different fermentation temperature. Example 1 was a variable temperature fermentation, while Comparative Example 11 was a constant temperature fermentation. The results showed that fermentation at the temperature of Example 1 was more conducive to the function of probiotics and improved the flavor, taste and other sensory characteristics of fried mulberry leaves.

[0196] Compared to Example 1, Comparative Examples 12-15, using only one type of bacteria or replacing it with other bacteria, resulted in a certain degree of adverse effects on the aroma, crispness, and firmness of the obtained mulberry leaves. This indicates that the fermentation of mulberry leaves using a specific ratio of Lactobacillus rhamnosus and Lactobacillus plantarum in this invention has a significant synergistic effect, which can significantly improve the flavor and taste of mulberry leaves.

[0197] Comparative Example 16 was conventionally fried without vacuum low-temperature treatment or plasma treatment. Although it underwent the same reagent treatment as Example 1, it was fried at high temperature, resulting in poorer color and appearance, and was too greasy. Its overall sensory score was significantly lower than that of Example 1.

[0198] Compared with Example 1, Comparative Example 17 did not undergo plasma treatment, which resulted in poorer surface fluidity, higher oil residue, and increased greasiness of the sample, affecting the overall appearance and taste of the mulberry leaves and making its overall quality somewhat worse than that of Example 1.

[0199] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing fried mulberry leaves, characterized in that, Includes the following steps: (1) Pretreatment: Fresh mulberry leaves were ultrasonically treated in an aqueous solution containing citric acid and magnesium carbonate, and then the mulberry leaves were transferred to an aqueous solution containing spirulina extract and zinc gluconate for soaking. (2) Variable temperature cold fermentation: Add Lactobacillus rhamnosus and Lactobacillus plantarum to the mulberry leaves treated in step (1), and pre-ferment at a temperature below 10℃ for 8-36 hours. Then transfer to a temperature of 20℃-30℃, add Lactobacillus rhamnosus and Lactobacillus plantarum, and continue fermentation for 1-3 days. After removing the liquid, add Lactobacillus rhamnosus and Lactobacillus plantarum again, and continue fermentation at a temperature of 10℃-25℃ for 1-3 days. (3) Coating with powder and soaking in oil: After the mulberry leaves treated in step (2) are coated with powder and soaked in oil; (4) Frying and degreasing: The mulberry leaves treated in step (3) are subjected to plasma treatment and vacuum frying in sequence to obtain the fried mulberry leaves; The vacuum frying temperature is 80℃-100℃.

2. The method for preparing fried mulberry leaves according to claim 1, characterized in that, In step (1), the concentration of citric acid in the aqueous solution containing citric acid and magnesium carbonate is 2 g / L-6 g / L, preferably 3 g / L-5 g / L, and the concentration of magnesium carbonate is 0.5 g / L-3 g / L, preferably 1 g / L-2 g / L. And / or, the ratio of the aqueous solution containing citric acid and magnesium carbonate to fresh mulberry leaves is 15mL-20mL:1g.

3. The method for preparing fried mulberry leaves according to claim 1, characterized in that, The ultrasonic treatment described in step (1) is pulsed ultrasonic treatment; The process parameters for pulsed ultrasound processing include: power of 800W-1000W, temperature of 15℃-30℃, working for 3-8 seconds and stopping for 3-8 seconds, and total ultrasound time of 20s-40s.

4. The method for preparing fried mulberry leaves according to claim 1, characterized in that, In step (1), the concentration of spirulina extract in the aqueous solution containing spirulina extract and zinc gluconate is 0.1 g / L-2 g / L, preferably 0.4 g / L-0.8 g / L, and the concentration of zinc gluconate is 2 g / L-30 g / L, preferably 8 g / L-12 g / L. And / or, the mass ratio of the spirulina extract to zinc gluconate is 1:18-22; And / or, the ratio of the aqueous solution containing spirulina extract and zinc gluconate to fresh mulberry leaves is 9 mL-15 mL: 1 g; And / or, the soaking temperature in step (1) is 50℃-60℃ and the soaking time is 5min-10min.

5. The method for preparing fried mulberry leaves according to claim 1, characterized in that, The spirulina extract is a dried powder of spirulina water extract; Preferably, the preparation method of the spirulina extract includes: extracting spirulina powder with water, concentrating and drying the supernatant to obtain the extract; Preferably, the ratio of the spirulina powder to water is 1g:20mL-40mL, more preferably 1g:25mL-30mL; Preferably, the water extraction temperature is 30℃-50℃ and the extraction time is 0.5h-2h.

6. The method for preparing fried mulberry leaves according to claim 1, characterized in that, The variable-temperature cold fermentation includes: adding Lactobacillus rhamnosus and Lactobacillus plantarum to the mulberry leaves treated in step (1), pre-fermenting at 2℃-4℃ for 20-28 hours, then transferring to 23℃-27℃, adding Lactobacillus rhamnosus and Lactobacillus plantarum, fermenting for 45-50 hours, removing the liquid, adding Lactobacillus rhamnosus and Lactobacillus plantarum again, and continuing fermentation at 15℃-20℃ for 45-50 hours.

7. The method for preparing fried mulberry leaves according to any one of claims 1-6, characterized in that, In step (2), the mass ratio of Lactobacillus rhamnosus to Lactobacillus plantarum added for the first time is 1:2-4, preferably 1:2.5-3.5, and more preferably 1:3; And / or, the mass ratio of Lactobacillus rhamnosus to Lactobacillus plantarum added for the second time in step (2) is 1:3-6, preferably 1:4.5-5.5, more preferably 1:5; And / or, the mass ratio of Lactobacillus rhamnosus to Lactobacillus plantarum added for the third time in step (2) is 1:2-4, preferably 1:2.5-3.5, and more preferably 1:

3.

8. The method for preparing fried mulberry leaves according to any one of claims 1-6, characterized in that, The total mass of Lactobacillus rhamnosus and Lactobacillus plantarum added for the first time in step (2) is 0.5‰ to 2.0‰ of the mass of fresh mulberry leaves, preferably 0.8‰ to 1.2‰; And / or, the total mass of Lactobacillus rhamnosus and Lactobacillus plantarum added for the second time in step (2) is 0.3‰ to 0.5‰ of the mass of fresh mulberry leaves, preferably 0.38‰ to 0.42‰; And / or, the total mass of Lactobacillus rhamnosus and Lactobacillus plantarum added for the third time in step (2) is 0.3‰ to 0.5‰ of the mass of fresh mulberry leaves, preferably 0.38‰ to 0.42‰.

9. The method for preparing fried mulberry leaves according to any one of claims 1-6, characterized in that, The oil mentioned in step (3) is a mixture of lemongrass oil, sesame oil and soybean oil in a mass ratio of 1:0.8-1.2:6-10; And / or, the soaking time described in step (3) is 0.5 min to 2 min; And / or, the temperature of vacuum frying in step (4) is 85℃-95℃; And / or, the vacuum degree of the vacuum frying in step (4) is –0.085 MPa to –0.098 MPa; And / or, the vacuum frying time in step (4) is 1 min to 3 min; And / or, the plasma generator for plasma treatment operates at a frequency of 25Hz-75Hz; And / or, the plasma treatment time is 5 to 10 seconds.

10. Fried mulberry leaves prepared by the preparation method according to any one of claims 1-9.

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