Prebiotic dried sweet potatoes and making technology thereof

Abstract

The invention belongs to the technical field of functional food, and relates to prebiotic dried sweet potatoes and a preparation method thereof. Comprising the following steps: thermally drying the surfaces of cut sweet potato strips / slices, atomizing and spraying alpha-amylase, and then steaming and liquefying; the steaming and liquefying process comprises the following steps: steaming at 55-65 DEG C, and heating to 85-100 DEG C for steaming; performing primary drying, atomizing and spraying an enzyme preparation solution on the surfaces of the primarily dried sweet potato strips / slices, and performing saccharification and glucoside conversion; enzyme preparations in the enzyme preparation solution are beta-amylase and alpha-glucosidase; and carrying out two-stage drying dehydration on the saccharified and glucoside-converted dried sweet potatoes, cooling, and carrying out high-temperature sterilization. The preparation method provided by the invention is simple and convenient in process; rich starch and soluble sugar of the sweet potatoes are converted into bifidus factor isomaltooligosacharide, so that the product has a probiotic function, and the functionality and additional value of the product are increased; and the prepared dried sweet potatoes also have a preservative effect.

Description

Technical Field

[0001] The invention belongs to the technical field of functional foods and relates to dried sweet potatoes containing prebiotics and a preparation process thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Sweet potato (Ipomoea batatas Lam.), also known as sweet potato, red taro, sweet potato, sweet potato, white potato, red potato, sweet potato, etc., is one of the most widely grown crops in my country. Sweet potato is rich in balanced nutrition. It is rich in protein, dietary fiber, polysaccharides, phosphorus, calcium, potassium, carotene, vitamins, anthocyanins, polyphenols and 8 kinds of amino acids required by the human body. It has many functions such as weight loss, prevention of diabetes, prevention of cardiovascular and cerebrovascular diseases, lowering cholesterol and anti-cancer, and has the reputation of "longevity food".

[0004] Sweet potato chips originated during the Jiaqing period of the Ming Dynasty. Most of them are golden yellow, crystal clear, or with white frost on the surface. Sweet potato chips are sweet, soft, tough, fragrant, and nutritious. They retain the original flavor of sweet potatoes to the greatest extent. They are a kind of snack food with unique flavor that is deeply loved by people from all over the country. The traditional processing method of sweet potato chips is generally handmade by families. The production process conditions are simple and backward. They are often dried in fire pits or in the sun. The efficiency is low and the sanitary conditions are poor. Black and green mold spores often infect and the taste becomes hard. The shelf life is short and the risk of consumption is high. With the expansion of industrial production scale, the processing technology has been adjusted. Usually, after washing, the skin is peeled, sliced ​​(strips), and then steamed and baked three times, and aseptically packaged as a finished product for sale. For example, patent CN 109527472 A discloses a method for preparing sweet potato chips: raw material selection, raw material pretreatment, sugaring, drying, and packaging. Patent CN110024990A discloses a production process of raw sweet potato without additives: fresh red-skinned and red-hearted sweet potatoes are stored in a cellar, removed from impurities, cleaned, peeled, cut into strips, vacuum pressed into starch enzyme hydrolysis at room temperature, steamed and baked three times, cooled, and then steamed at 95-100°C after bagging, cooled, irradiated and sterilized before packing. Patent CN118436060A discloses a production method of reverse steamed sweet potato: raw material acceptance, peeling and cutting, cleaning and soaking, vacuum impregnation with white sugar, steaming, baking, cooling and sterilization, vacuum inner packaging, metal detection, high-pressure sterilization, and product outer packaging to obtain sweet potato. At present, some sweet potato chips on the market use too much sugar, some are too hard, and some are added with pigments and preservatives, and have a single function, which is contrary to people's pursuit of health. There is a technical problem in the industrial production of dried sweet potatoes. After peeling and slicing the raw sweet potatoes, the starch slurry attached to the surface will cause the surface of the processed dried sweet potatoes to turn brown and become sticky. The current treatment method is to add a water washing and color protection process after slicing. A large amount of raw starch remains in the washing water, and general dried sweet potato processing companies do not have the ability to recycle starch slurry. The washing water directly enters the sewage treatment system, which not only wastes a large amount of high-quality sweet potato starch, but also increases the sewage treatment load.

[0005] Isomaltooligosaccharide is an important prebiotic with a refreshing taste, high safety and pure sweetness. It is heat-resistant and acid-resistant, with low viscosity and low water activity, thus having a certain antiseptic effect. It also has moisturizing properties and can inhibit the formation of sucrose and glucose crystals and prevent starch aging. Isomaltooligosaccharide is a non-fermentable oligosaccharide that not only has good anti-caries properties but also can inhibit the formation of dental plaque. As a prebiotic, it also has many physiological functions, including: (1) promoting the digestion and absorption of food by the human body and maintaining the normal function of the human intestine. (2) inhibiting the growth of putrefactive bacteria and pathogens, promoting the growth of probiotics, regulating intestinal flora, and improving constipation and diarrhea. (3) maintaining intestinal microecological balance during chemotherapy, radiotherapy and antibiotic treatment. (4) reducing toxic and harmful intestinal carcinogens, improving blood lipids and lowering cholesterol. (5) promoting the absorption of minerals such as iron and calcium. (6) promoting nutrient absorption and assisting the synthesis of nutrients such as B vitamins. (7) improving the body's immunity. (8) protecting the liver. Isomaltooligosaccharides are not easily utilized by human digestive enzymes and have a low glycemic index, so they can be used as a healthy sugar substitute for diabetic patients.

[0006] At present, there are no reports on sweet potato products that contain prebiotic components and retain sweet potato health functional components and their preparation methods. Summary of the invention

[0007] The purpose of the present invention is to provide a sweet potato dry product containing prebiotics and a production process thereof. The production process provided by the present invention is not only simple in process, but also converts the rich starch and soluble sugar of the sweet potato itself into prebiotics, thereby increasing the functionality and added value of the product; and also enables the prepared sweet potato dry product to have an antiseptic effect and prolong the shelf life.

[0008] In order to achieve the above object, the technical solution of the present invention is:

[0009] In a first aspect, a process for preparing prebiotic dried sweet potatoes comprises the following steps:

[0010] Spraying α-amylase on the surface of the cut sweet potato strips / slices, and then steaming and liquefying; the steaming and liquefying process is: first steaming at 55°C to 65°C, and then heating to 85°C to 100°C for steaming;

[0011] Preliminarily drying the steamed liquefied sweet potato strips / slices until the moisture content of the sweet potato strips / slices is 65% to 70%;

[0012] Spraying an enzyme solution onto the surface of the preliminarily dried sweet potato strips / slices to perform saccharification and transglycosides; the enzymes in the enzyme solution are β-amylase and α-glucosidase;

[0013] The sweet potato strips / slices after saccharification and transglycosides are dehydrated, cooled and sterilized.

[0014] Preferably, the α-amylase solution is sprayed on all surfaces of the sweet potato strips by atomization, the concentration of the enzyme in the α-amylase solution is 10U / mL to 20U / mL, preferably 12U / mL to 16U / mL, and the volume of the α-amylase solution sprayed per ton of fresh sweet potato strips / slices is 5L to 15L, preferably 7L to 10L. The amount of enzyme added and the two-stage heating conditions have a great influence on the product quality of the dried sweet potatoes. A large number of experiments have verified that the taste, sweetness and appearance of the dried sweet potatoes within the above range are the best.

[0015] Preferably, the preliminary drying method is: hot air drying at 50° C. to 70° C. until the moisture content of the sweet potato strips / slices is 65% to 70%.

[0016] Preferably, the steaming liquefaction process is: first steaming at 55°C to 65°C for 1 to 5 minutes, then heating to 85°C to 100°C and steaming for 10 to 15 minutes.

[0017] Preferably, in the enzyme solution, β-amylase is 170U / mL to 200U / mL, α-glucosidase is 180U / mL to 260U / mL, and the amount of enzyme preparation uniformly sprayed by atomization per ton of sweet potato is 5L to 7L. The amount of enzyme added has a great influence on the product quality of dried sweet potato. A large number of experiments have verified that the taste, sweetness and appearance of dried sweet potato in the above range are the best.

[0018] Preferably, the temperature of the saccharification transglycoside is 50° C. to 60° C., and the humidity of the saccharification transglycoside is 85RH% to 90RH%.

[0019] Preferably, the time for glycosylation transglycoside is 2h to 6h, preferably 2h to 4h.

[0020] Preferably, after steaming and liquefaction, the mixture is cooled to 60°C±2°C, and then the enzyme preparation solution is sprayed by atomization and then saccharification and transglycosides are performed.

[0021] Preferably, dehydration is carried out by a segmented drying method. Specifically, the segmented drying method is as follows: the first drying process is to maintain the oven temperature at 75°C to 85°C, preferably 80°C to 85°C, for 6h to 8h; the second drying process is to maintain the oven temperature at 50°C to 60°C, preferably 50°C to 55°C, for 24h to 36h. Dehydration is performed until the moisture content is 23% to 28%.

[0022] Preferably, the specific steps are as follows:

[0023] (1) Raw material selection and pretreatment;

[0024] (2) Thermal drying of the cut sweet potato strips / slices: The thermal drying process is as follows: hot air at 50° C. to 70° C. is blown on the surface of the sweet potato strips for 1 min to 10 min;

[0025] (3) spraying high-temperature α-amylase on the surface of the cut sweet potato strips / slices by atomization, and then steaming and liquefying; the steaming and liquefying process is: first steaming at 55° C. to 65° C., and then heating to 85° C. to 100° C. for steaming;

[0026] (4) Blow the steamed sweet potato strips / slices with dry, clean cool air to 60°C ± 2°C;

[0027] (5) spraying an enzyme preparation solution onto the surface of the sweet potato strips / slices in step (4) to perform saccharification and transglycoside conversion under constant temperature and humidity conditions; the enzyme preparation in the enzyme preparation solution is β-amylase and α-glucosidase;

[0028] (6) Segmented drying and dehydration of dried sweet potatoes;

[0029] (7) Cooling, trimming, vacuum inner packaging, and high-temperature sterilization.

[0030] Preferably, in step (1), the sweet potato varieties and block shapes used for preparing dried sweet potatoes are selected, fresh and intact sweet potatoes that have been stored and saccharified are removed, washed, peeled, and cut into strips or slices preferably with a thickness of 1 cm to 2 cm.

[0031] Preferably, in step (2), the hot air is blown at 55°C to 65°C for 2min to 3min.

[0032] Furthermore, in step (3), the α-amylase solution is sprayed on all surfaces of the sweet potato strips, the enzyme concentration is 12U / mL to 16U / mL, and the amount added is 7L to 10L per ton of fresh sweet potato strips / slices. The amount of enzyme added and the two-stage heating conditions have a great influence on the product quality of the dried sweet potatoes. A large number of experiments have verified that the taste, sweetness and appearance of the dried sweet potatoes within the above range are the best.

[0033] Furthermore, in step (5), the β-amylase and α-glucosidase solutions are sprayed on all surfaces of the sweet potato strips, preferably 170U / mL to 200U / mL of β-amylase and 180U / mL to 260U / mL of α-glucosidase, and the amount of enzyme preparation uniformly sprayed by atomization per ton of sweet potato is 5L to 7L. The preliminarily dried sweet potato strips are moved into a constant temperature and humidity room or box with a temperature of 50°C to 60°C and a humidity of 85RH% to 90RH%, and the saccharification and transglycoside time is 2h to 4h. The amount of enzyme added has a great influence on the product quality of the dried sweet potato. A large number of experiments have verified that the taste, sweetness and appearance of the dried sweet potato in the above range are the best.

[0034] Furthermore, step (6) adopts segmented drying, the first drying process is to maintain the oven temperature at 80°C to 85°C for 6h to 8h; the second drying process is to maintain the oven temperature at 50°C to 55°C for 24h to 36h. Dehydration is performed until the moisture content is 23% to 28%.

[0035] As a preferred embodiment, in step (7), the dried sweet potatoes are cooled to 40°C to 45°C with clean cold air, manually trimmed, vacuum packed into a sterile inner bag that has been ultraviolet sterilized for 30min to 45min, sterilized at high temperature at 118°C to 121°C for 10min to 20min, rinsed with cold water, air showered, weighed, and packed into an outer package.

[0036] In a second aspect, a prebiotic dried sweet potato is obtained by the above preparation method.

[0037] Preferably, its components include nutritional and health functional ingredients such as dietary fiber, starch, glucose, maltose, isomaltooligosaccharide, protein, free amino acids, vitamins, carotene, polyphenols, mineral elements, etc.

[0038] Further preferably, the prebiotics include isomaltose, isomaltotriose and panose.

[0039] Furthermore, the content of glucose is 5-8.5wt% (dry basis); the content of maltose is 8.5-12.5wt%; the content of isomaltose is 0.2-2wt%; the content of isomaltotriose is 0.1-0.5wt%; and the content of panose is 0.1-1.5wt%.

[0040] The beneficial effects of the present invention are:

[0041] In the process of preparing the dried sweet potatoes, the present invention performs enzymatic reaction by spraying α-amylase, β-amylase and transaminase by atomization, and converts part of the starch of the dried sweet potatoes (especially the starch on the surface thereof) into prebiotics while ensuring that the dried sweet potatoes can be prepared. The prebiotics have the characteristics of moisture retention, low water activity, ability to inhibit the formation of sucrose and glucose crystals and prevent starch aging, which can not only increase the sweetness and taste of the dried sweet potatoes, but also increase the prebiotic physiological function of the dried sweet potatoes and extend the shelf life.

[0042] The dried sweet potatoes prepared by the preparation method provided by the present invention are bright in color, moderate in hardness and softness, have good flexibility, are easy to chew, and do not stick to teeth. In particular, after being placed for a long time, the situation that the texture becomes hard and the quality decreases due to starch aging is controlled. The variety of starch invert sugar is increased, which greatly increases the sweetness range of the product. The product is sweet but not greasy, adds prebiotic function, and has a wider audience consumer group. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0044] Figure 1The liquid chromatogram of the dried sweet potato water-immersion solution prepared by process (A1) without adding any enzyme in the embodiment of the present invention;

[0045] Figure 2 This is a liquid chromatogram of the water-immersion solution of dried sweet potatoes prepared by the process (A6) of adding α-amylase, β-amylase and transaminase in the embodiment of the present invention. DETAILED DESCRIPTION

[0046] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0047] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0048] The α-glucosidase described in the present invention is α-glucosidase or α-glucosidase.

[0049] In view of the fact that the existing methods for solving the problems of discoloration and stickiness caused by starch slurry attached to the surface of dried sweet potatoes during the preparation process have the problems of difficult post-processing, complicated process, quality degradation after long-term storage and monotonous functionality of dried sweet potatoes, the present invention proposes a prebiotic dried sweet potato and a preparation method thereof.

[0050] Example 1

[0051] A process for preparing prebiotic dried sweet potatoes, comprising the following steps:

[0052] (1) Select fresh sweet potatoes that have been stored and saccharified, remove impurities, wash, peel, and cut into strips / slices with a thickness of 1.5 cm.

[0053] (2) Spread 1 kg of sweet potato strips / slices evenly on a stainless steel mesh mat and blow dry with hot air at 55°C until there is no water stain on the surface.

[0054] (3) Evenly spray 7 mL of the diluted medium-temperature α-amylase solution onto the surface of the sweet potato strips, heat to 60°C and hold for 3 min, then continue to heat to 88°C and hold for 12 min, and control the sweet potato strips to be steamed thoroughly without breaking.

[0055] (4) Clean cool air blows to 60℃±2℃.

[0056] (5) Prepare a mixed enzyme solution containing 6 mL of β-amylase 180 U / mL and α-glucosidase 200 U / mL, and evenly spray it onto the aforementioned sweet potato strips. Move the strips into a constant temperature and humidity room at 55°C and 85 RH% for saccharification and transglycosides for 4 hours.

[0057] (6) The sweet potato strips are transferred to a drying room and baked at 80° C. for 7 h in the first stage; the second stage is baked at 50° C. for 30 h, with a moisture content of 25%±2%.

[0058] (7) Cool the dried sweet potatoes to 40°C with clean cold air, trim them manually, vacuum pack them into a sterile inner bag that has been sterilized by ultraviolet light for 40 minutes, sterilize them at 121°C for 15 minutes, rinse them with cold water, air-shower them, weigh them, and pack them into outer packaging to obtain the finished prebiotic dried sweet potatoes.

[0059] Example 2 Process Optimization

[0060] 1 Experimental materials:

[0061] Fresh sweet potatoes: The variety, storage saccharification time and potato shape are not specifically limited in the present invention. The enzyme activity and product form of medium-temperature α-amylase, β-amylase, and α-glucosidase (hereinafter referred to as transaminase) are not limited.

[0062] 2Main instruments and equipment

[0063] Liquid chromatograph LPG3400SD, Dionex China Co., Ltd.; handheld refractometer, Medtronic Biotechnology Co., Ltd.

[0064] 2 Experimental methods

[0065] 2.1 Determination of solid content

[0066] Take samples from different processes and blank samples of dried sweet potatoes to determine the moisture content. Weigh 2.0g (equivalent to dry weight, accurate to ±0.001g) in a 50mL centrifuge tube, add water to 40.0g, shake well, and centrifuge at 12000r / min for 10min. Zero the handheld refractometer with water, take the centrifuged supernatant to determine the solid content of the sample, take the average of the two determination results, and multiply the average by the dilution factor to obtain the solid content of the dried sweet potatoes.

[0067] 2.2 Determination of prebiotics

[0068] The supernatant of Experimental Method 3.1 was filtered through a 0.22 μm filter membrane and set aside.

[0069] Liquid chromatograph: U3000, Thermo; differential detector: shodex. Reference chromatographic conditions: Chromatographic column: amino column (4.6mm×250mm, particle size 5pm, aminosilane bonded silica gel as filler), Thermo; mobile phase: acetonitrile + water = 75 + 25 (volume ratio); flow rate 1.0mL / min; column temperature 40℃; injection volume 10μL; differential detector temperature 40℃. Determine the peak area of ​​soluble sugars such as isomaltose, panose, and isomaltotriose. 1% glucose, fructose, sucrose, maltose, isomaltose, panose, and isomaltotriose standard solutions were loaded for analysis, and the liquid phase retention time was used for qualitative analysis and the peak area was used for quantitative analysis.

[0070] 2.3 Sensory evaluation of prebiotic dried sweet potatoes

[0071] Eleven sensory assessors with relevant professional level were selected to score the prepared dried sweet potatoes according to color (20%), shape (30%), texture (20%), aroma and taste (30%). The scoring criteria are shown in Table 1.

[0072] Table 1 Sensory evaluation standards for prebiotic sweet potato chips

[0073]

[0074] 3 Condition Experiment

[0075] 3.1 Addition of medium temperature amylase

[0076] Randomly select 1 kg of sweet potato strips with a thickness of 1.5 cm that have been cut and mixed, and operate according to the process in Example 1: blow dry hot air at 55°C until there is no water stain on the surface, which actually takes 1 minute. Evenly spray 7 mL of diluted medium-temperature α-amylase solution on the surface of the sweet potato strips (step (3)), heat to 60°C and hold for 3 minutes, continue to heat to 88°C and hold for 12 minutes, and control the sweet potato strips to be steamed through and not broken. Blow clean cool air to 60°C±2°C. Prepare a mixed enzyme solution containing 6 mL of 180 U / mL β-amylase and 200 U / mL α-glucosidase, and evenly spray it on the aforementioned sweet potato strips (step (5)). Move to a constant temperature and humidity room with a temperature of 55°C and a humidity of 85RH%, and saccharify and transglycoside for 4 hours. A 0 ~A 5 The samples only changed the amount of enzyme added in step (3) and step (5). 0 No enzyme was added to the sample in both steps, which was a blank sample; A 1 α-amylase is added to the sample, and no mixed enzyme solution is added in step (5); A 2 The sample is added with α-amylase and β-amylase, and no transaminase is added in step (5); A 3In step (3), medium-temperature α-amylase was not added; in step (3) and (5) of sample A4, enzyme solution was sprayed. The results are shown in Table 2 and Figures 1-2 shown.

[0077] Table 2 Determination of enzyme addition process

[0078]

[0079] Comparison A 1 and A 0 It can be seen that adding a small amount of medium-temperature α-amylase can increase the maltose content in the sample. Studies have found that maltose is a key precursor substance for the production of prebiotics. On the one hand, during the conversion process, the transaminase first breaks the α-1,4 glycosidic bond of maltose and decomposes it into two glucose units, which are then rebonded through α-1,6 glycosidic bonds to complete the isomerization process from maltose to isomaltose within the molecule. At the same time, some of the glucose units decomposed from maltose react with maltose or isomaltose through intermolecular interactions to produce panose or isomaltotriose. Compare A 3 and A 4 From the prebiotic content of the two samples, it can be found that adding α-amylase can increase the total amount of prebiotics in the product. The reason for this is that β-amylase will stop working when it encounters the α-1,6 glycosidic bond in starch. α-amylase can provide more degradable dextrin, which is beneficial to the accumulation of maltose, the substrate of transaminase.

[0080] 3.2 Selection of transglycosylation time

[0081] 1 kg of cut and mixed sweet potato strips were randomly selected and operated according to the process in Example 1, except that the enzyme action time in step (5) was changed. 5 The sample was kept at 60℃ and constant humidity for 2h. 4 Transamination 4h, A 6 The results are shown in Table 3.

[0082] Table 3 Determination of transglycoside time

[0083]

[0084] From the data in Table 3, we can see that panose is an intermediate product of transglycosylation. When maltose is in sufficient supply, its content increases. When the maltose content in the system is low, panose can be consumed as a substrate and its content decreases. From the fact that the panose content at a transglycosylation time of 2h is higher than that at 4h, it can be determined that panose can reach its peak at 2-3h. At 8h of transglycosylation, the panose content in the dried sweet potato has dropped sharply. From the perspective of energy cost reduction and efficiency improvement, it is appropriate to use transglycosylation for 2-3h.

[0085] The present invention can reduce the starch content of dried sweet potatoes, and can generate prebiotic factors without adding any external factors, which greatly improves the prebiotic function and health care function of dried sweet potatoes. Combined with the dietary fiber advantages of sweet potatoes, the product is very friendly to people who need to improve intestinal health and people with diabetes and obesity. The sensory evaluation results of prebiotic dried sweet potatoes are shown in Table 4.

[0086] Table 4 Sensory evaluation results

[0087]

[0088]

[0089] Comparative Example 1

[0090] The sample preparation of this comparative example is the same as that of the sample preparation of the above-mentioned Example 1, with the difference that in step (3) of the process steps, the sweet potato strips / slices are immersed in a medium-temperature α-amylase enzyme solution. Through experiments, it was found that 300g of fresh sweet potato strips / slices were immersed in water, requiring 300mL of water for 30s, and the amount of water stained on the outer surface was 11.03g. In order to ensure that the amount of enzyme added was consistent with that in Example 1, the enzyme solution for spraying needs to be diluted 3 times. Take 1kg of fresh sweet potato strips / slices and immerse them in 1L of α-amylase solution diluted twice for 30s at the same time, then immediately remove them, drain them, and blow them with 55°C dry hot air until there is no water stain on the surface. The actual time is about 3min. The other conditions are the same as in Example 1, and the transglycoside time is 4h.

[0091] Comparative Example 2

[0092] The sample preparation of this comparative example is the same as that of the sample preparation of the above-mentioned Example 1, except that: in step (5) of the process steps, 1 kg of sweet potato strips / slices are sprayed with α-amylase, dried, cooled, etc. in Example 1, immersed in 1L of secondary diluted mixed enzyme solution prepared from β-amylase and α-glucosidase finished enzyme preparation, and then immediately removed and drained. The remaining operations are the same as in Example 1, and the transglycosidation time is 4 hours.

[0093] Table 5 Determination of enzyme addition method

[0094]

[0095] Comparing the sugar content in Table 3 and Table 5, the data show that the disadvantages of the two comparative examples are not obvious, but the solid content of the soaked enzyme solution is determined to be 2.3%, which contains soluble sugar and starch, indicating that the starch on the surface of the sweet potato enters the secondary diluted enzyme solution, which not only violates the original intention of the present invention, but also increases the risk of contamination and deterioration of the enzyme solution, making it difficult to handle, and the amount of hot air used in the drying and fixing stage is increased.

[0096] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A process for producing prebiotic dried sweet potatoes, characterized in that: The steps include: Spraying α-amylase on the surface of the cut sweet potato strips / slices, and then steaming and liquefying; the steaming and liquefying process is: first steaming at 55° C. to 65° C., and then heating to 85° C. to 100° C. for steaming; Preliminarily drying the steamed liquefied sweet potato strips / slices until the moisture content of the sweet potato strips / slices is 65% to 70%; Spraying an enzyme preparation solution onto the surface of the preliminarily dried sweet potato strips / slices to perform saccharification and transglycosides; The enzyme preparations in the enzyme preparation solution are β-amylase and α-glucosidase; The sweet potato strips / slices after saccharification and transglycosides are dehydrated, cooled and sterilized.

2. The manufacturing process according to claim 1, characterized in that: The α-amylase solution is sprayed on all surfaces of the sweet potato strips by atomization. The concentration of the enzyme in the α-amylase solution is 10U / mL to 20U / mL, preferably 12U / mL to 16U / mL. The volume of the α-amylase solution sprayed per ton of fresh sweet potato strips / slices is 5L to 15L, preferably 7L to 10L.

3. The manufacturing process according to claim 1, characterized in that the initial The drying method is: using hot air drying at 50°C to 70°C until the moisture content of the sweet potato strips / slices is 65% to 70%.

4. The manufacturing process according to claim 1, characterized in that: The process of steaming and liquefaction is: first steam at 55℃~65℃ for 1~5min, then heat to 85℃~100℃ and steam for 10~15min.

5. The manufacturing process according to claim 1, characterized in that: In the enzyme preparation solution, the content of β-amylase is 170U / mL to 200U / mL, and the content of α-glucosidase is 180U / mL to 260U / mL. The amount of enzyme preparation uniformly atomized and sprayed on each ton of sweet potato is 5L to 7L.

6. The manufacturing process according to claim 1, characterized in that: The temperature of the glycosylation transglycoside is 50°C to 60°C, and the humidity of the glycosylation transglycoside is 85RH% to 90RH%; Alternatively, the time for glycosylation and transglycosylation is 2 h to 6 h, preferably 2 h to 4 h.

7. The manufacturing process according to claim 1, characterized in that: After steaming and liquefaction, cool to 60℃±2℃, spray the enzyme preparation solution, and carry out saccharification and transglycosides.

8. The manufacturing process according to claim 1, characterized in that: Dehydration adopts a segmented drying method. Specifically, the segmented drying method is: the first drying process is to maintain the oven temperature at 75°C to 85°C, preferably 80°C to 85°C, for 6h to 8h; the second drying process is to maintain the oven temperature at 50°C to 60°C, preferably 50°C to 55°C, for 24h to 36h. Dehydration is performed until the moisture content is 23% to 28%.

9. The manufacturing process according to claim 1, characterized in that: The specific steps are as follows: (1) Raw material selection and pretreatment; (2) Thermal drying of the cut sweet potato strips / slices: The thermal drying process is as follows: hot air at 50° C. to 70° C. is blown on the surface of the sweet potato strips for 1 min to 10 min; (3) spraying high-temperature α-amylase on the surface of the cut sweet potato strips / slices by atomization, and then steaming and liquefying; the steaming and liquefying process is: first steaming at 55° C. to 65° C., and then heating to 85° C. to 100° C. for steaming; (4) Blow the steamed sweet potato strips / slices with dry, clean cool air to 60°C ± 2°C; (5) spraying an enzyme preparation solution onto the surface of the sweet potato strips / slices in step (4) to perform saccharification and transglycoside conversion under constant temperature and humidity conditions; the enzyme preparation in the enzyme preparation solution is β-amylase and α-glucosidase; (6) Segmented drying and dehydration of dried sweet potatoes; (7) Cooling, trimming, vacuum inner packaging, and high-temperature sterilization.

10. A prebiotic sweet potato dry, characterized in that: Obtained by the preparation method according to any one of claims 1 to 9.

Images