Dioscorea opposita thunb. powder with low glycemic index and preparation method and application thereof

Abstract

The application discloses a low-glycemic-index yam powder and a preparation method and application thereof, and belongs to the technical field of food processing. The preparation method comprises the following steps: (1) washing fresh yam, peeling, boiling, and crushing into a paste; (2) adding 1-2% of pulanase in mass percentage into the yam paste for enzymolysis; (3) adding 1-4% of bamboo-leaf flavones in mass percentage into the yam paste after the enzymolysis for modification; and (4) drying and crushing to obtain the yam powder. The bamboo-leaf flavones and the pulanase are used in combination for the first time to improve starch-based full powder food, the estimated glycemic index of the yam powder is reduced to a low glycemic index level (≤55), the solubility of the yam powder is greatly improved, and the viscosity after the yam powder is brewed is reduced. The yam powder prepared by the preparation method has a very low browning degree, the method is simple and easy to operate, has high feasibility, is non-toxic and harmless, safe and pollution-free.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of food processing, in particular to a low glycemic index yam powder and a preparation method and application thereof. BACKGROUND

[0002] Yam is a food resource with medicinal and edible properties. It is recorded in Bencao Qushen that "it is a food, with warm and flat qi, and can nourish the lung and spleen yin, so it can moisten the skin and hair, and strengthen the muscle, with sweet and salty taste, and can also benefit the kidney and strengthen the yin". Fresh yam has a high water content and is not suitable for storage and is prone to rot, so it is processed into powder by drying technology to effectively maintain the original flavor and nutritional ingredients of yam, and is convenient for storage and transportation. Since yam powder contains a high content of starch, the blood sugar level rises rapidly after eating yam powder, which is not friendly to people who have health requirements for diet. Therefore, it is necessary to modify the yam starch to improve its anti-digestibility and broaden its application in the field of food and other fields.

[0003] At present, the anti-digestibility of starch is mainly improved by physical, chemical and biological treatment methods. The physical method includes: extrusion treatment (J. Ouyang, et al. Food Chem. 431 (2024) 137056.), hydrothermal treatment, electron beam irradiation, mixing with other low glycemic index raw materials, etc. However, the method of mixing yam with low glycemic index raw materials such as vegetables and cereals is not conducive to the development of yam efficacy due to the low content of yam; the chemical method mainly includes acid hydrolysis, cross-linking, esterification, oxidation, etherification and complex modification, etc., but the safety problem of chemical modification is not conducive to wide application in the field of food. The biological method includes starch debranching enzyme (P.J. Butterworth, et al. Trends Food Sci. Technol. 120 (2022) 254-264.) and lipase for structural modification of the main components of yam powder, but the yam powder modified by amylase has improved anti-digestibility but still has a high glycemic index.

[0004] In the existing process, yam is usually treated by a single method, and the prepared yam powder has problems such as easy browning (unripened yam is prone to browning due to oxidation reaction), poor brewing property (poor solubility, high swelling power and weak fluidity, etc.), which is not conducive to its application in liquid food, complex preparation process and high equipment requirements, etc.

[0005] Therefore, it is a problem to be solved by those skilled in the art to develop a simple and efficient treatment method to improve the brewing property and anti-digestibility of yam powder and ensure safety. SUMMARY

[0006] The present application aims to provide a yam powder with a low glycemic index, and the modification of yam starch is realized through process optimization to improve the infusion property and digestion resistance of the yam powder and ensure food safety.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] The present application provides a preparation method of a yam powder with a low glycemic index, comprising the following steps:

[0009] (1) washing fresh yam, peeling, cooking, and crushing into a paste to obtain yam paste;

[0010] (2) adding 1-2% of pullulanase by mass percentage to the yam paste for enzymatic hydrolysis;

[0011] (3) adding 1-4% of bamboo leaf flavonoids by mass percentage to the yam paste after enzymatic hydrolysis for modification;

[0012] (4) drying and crushing the modified yam paste to obtain the yam powder with a low glycemic index.

[0013] In step (1), the fresh yam is washed clean without dirt, and the problematic yam is screened out before peeling. After peeling, the yam is submerged in water to avoid browning. Then the yam is cooked, and the browning degree of the cooked yam is significantly reduced.

[0014] Preferably, the peeled yam is mixed with water at a solid-liquid ratio of 1:2-1:4, and pre-cooked in a boiling water bath for 20-40 min until the yam is fully cooked.

[0015] Preferably, the cooked yam is crushed in a cell disrupter at 30000 r / min for 2-4 min until there is no obvious particle.

[0016] In step (2), pullulanase is used as a starch debranching agent to modify yam starch. By breaking the α-1,6-glycosidic bond of the branched chain in starch, pullulanase forms more long / short chain amylose, thereby reducing the branching degree of starch molecules. Short-time treatment can improve the infusion property of yam powder and change its rheological properties, which is beneficial to the application in liquid food, and the protein content of yam powder is increased after enzymatic hydrolysis without removal.

[0017] Studies have shown that the use of 1-2% of pullulanase by mass percentage on cooked yam can reduce the glycemic index of yam powder, reduce the water absorption and swelling potential of yam powder, and improve the water solubility of yam powder.

[0018] Preferably, the pullulanase is added to the yam paste after cooling, and stirred at 50-70℃ in a water bath at 30-90 r / min for 20-40 min.

[0019] More preferably, placed in a 60℃ water bath stirring 30min, stirring speed is 60r / min.

[0020] In step (3), bamboo leaf flavone is used as a modifier, bamboo leaf flavone is added to the enzyme-degraded yam paste for modification, and the anti-digestive component of yam powder can be improved in a short time. The amylose and bamboo leaf flavone interact with each other through hydrophobic interaction, hydrogen bond and van der Waals force, etc. to form more starch-bamboo leaf flavone complexes, for example, the hydroxyl group in the bamboo leaf flavone and the hydrophobic group of the side chain of the starch molecule interact with each other to improve the crystallinity of the starch molecule. The modified yam powder can gradually release the combined bamboo leaf flavone after being ingested, the bamboo leaf flavone can be used as a competitive inhibitor of amylase, and is beneficial to the application in the food for maintaining stable blood sugar.

[0021] Research shows that the use of bamboo leaf flavone and pullulanase combined to improve yam starch can further reduce the glycemic index of yam powder and further improve the brewing property of yam powder.

[0022] Preferably, after adding bamboo leaf flavone, it is placed in a 80-100℃ water bath and stirred at 30-90r / min for 20-40min.

[0023] The addition amount of bamboo leaf flavone and the anti-digestive property of yam powder treated by pullulanase show a dose-dependent relationship, with the gradual increase of bamboo leaf flavone, the glycemic index of yam powder gradually decreases, and the yam powder has strong anti-digestive property. Preferably, 2% (w / w) of bamboo leaf flavone is added to the enzyme-degraded yam paste, when the addition amount of bamboo leaf flavone is ≥2% (w / w), the glycemic index of yam powder is <55, reaching the low glycemic index level.

[0024] More preferably, after adding bamboo leaf flavone, it is placed in a 90℃ water bath and stirred for 30min at a stirring speed of 60r / min.

[0025] In step (4), after modification, the modified product is placed in a drying machine and dried until no obvious water sample is observed, and the drying method can be, but is not limited to, natural air drying, hot air drying and freeze drying. After drying, the product is crushed in a crusher and sieved.

[0026] Preferably, the crushed yam powder has a particle size of 60-100 meshes.

[0027] The application also provides a yam powder prepared by the above preparation method. The yam powder of the application has good brewing property and anti-enzymatic property, strong fluidity after brewing, and a predicted glycemic index as low as a low glycemic index level (≤55). The application meets the demand for low digestibility on the basis of nutrition, is beneficial to maintaining stable blood sugar of the human body, and improves the application range and consumer acceptance of yam powder.

[0028] The application also provides application of the yam powder in food preparation.

[0029] The application has the following beneficial effects:

[0030] (1) The application first uses bamboo leaf flavones and pullulanase in combination to improve starch-based full powder food, and the bamboo leaf flavones can increase the resistant starch content of yam powder and act as a starch amylase inhibitor to inhibit the characteristics of starch amylase, and the pullulanase can reduce the branching degree of yam starch, so that the digestion resistance of yam powder is improved, and the estimated blood glucose generation index of yam powder is reduced to a low blood glucose generation index level (≤55). Moreover, after the bamboo leaf flavones and pullulanase are used in combination, the solubility of yam powder is greatly improved, and the viscosity after reconstitution is reduced, which is beneficial to high-content application in liquid food.

[0031] (2) Compared with another common polyphenol, i.e., tea polyphenol, the yam powder prepared by using bamboo leaf flavones has better digestion resistance.

[0032] (3) The yam powder prepared by the preparation method has very low browning degree, and the method is simple to operate, highly feasible, non-toxic and harmless, safe and pollution-free.

[0033] (4) Compared with traditional yam powder, the modified yam powder has a higher water solubility index and a lower swelling potential, and has strong fluidity after reconstitution; the estimated blood glucose generation index of the yam powder is reduced to ≤55, reaching the level of low blood glucose generation index food, meeting the needs of low digestion on the basis of nutrition, and improving the application range and consumer acceptance of the yam powder. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The bamboo leaf flavones and pullulanase are used in combination to improve the in vitro digestion curve of yam powder.

[0035] Figure 2 The bamboo leaf flavones and pullulanase are used in combination to improve the reconstitution of yam powder.

[0036] Figure 3 The bamboo leaf flavones and pullulanase are used in combination to improve the rheological properties of yam powder.

[0037] Figure 4 The in vitro digestion curves of yam powder with different bamboo leaf flavone contents.

[0038] Figure 5 The reconstitution of yam powder with different bamboo leaf flavone contents.

[0039] Figure 6 The rheological properties of yam powder with different bamboo leaf flavone contents.

[0040] Figure 7 To improve the in vitro digestion curve of yam powder by bamboo leaf flavonoids / tea polyphenols. DETAILED DESCRIPTION

[0041] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. The embodiments are only used to explain the present application and are not used to limit the scope of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0042] The test methods used in the following examples are conventional methods unless otherwise specified; the materials, reagents, etc. used are commercially available reagents and materials unless otherwise specified.

[0043] Bamboo leaf flavonoids (CAS: 91771-33-4), tea polyphenols (CAS: 84650-60-2), pullulanase (CAS: 9075-68-7), acetate buffer (CAS: BIO-000009), alpha-amylase (CAS: 9000-90-2), starch glucosidase (CAS: 9032-08-0).

[0044] Example 1: Effect of bamboo leaf flavonoids and pullulanase on the in vitro digestibility of yam powder

[0045] Yam powder preparation: After washing and peeling fresh yam, pre-cook in boiling water bath for 30 min, then transfer to a cell disruptor and break for 2 min at 30000 r / min, then add 1% (w / w) pullulanase and stir in a 60°C water bath for 30 min, then add 1% (w / w) bamboo leaf flavonoids and stir in a 90°C water bath for 30 min, freeze-dry, crush through a 60-mesh sieve, and name it YPE1B.

[0046] The other three control samples do not add (1) bamboo leaf flavonoids, (2) pullulanase, (3) bamboo leaf flavonoids and pullulanase, respectively, and are named YPE, YP1B and YP.

[0047] In vitro digestibility: 50 mg of sample was weighed, 2.5 mL of acetate buffer at pH 5 was added, and it was incubated in a water bath at 95°C for 30 min. After cooling to 37°C, 500 μL of mixed enzyme solution (80 mg of α-amylase and 60 mg of amyloglucosidase dissolved in 10 mL of acetate buffer) was added, and it was incubated in a water bath at 37°C with magnetic stirring at 120 r / min. 20 μL of the suspension was added to 1 mL of ethanol at 0, 5, 10, 15, 20, 40, 60, 90, 120 and 180 min, respectively, and it was centrifuged at 1000 x g for 5 min. The glucose concentration of the supernatant was determined using a glucose kit (GOD-POD microplate). The hydrolysis rate of the sample at each time was fitted to a kinetic equation, and the hydrolysis index (HI) and the estimated glycemic index (eGI) were calculated. The relevant formulas are as follows:

[0048] C = C ∞ × (1 - e -kt )

[0049]

[0050] eGI (%) = 8.198 + 0.862 x HI

[0051] In the formulas, C is the percentage of starch hydrolysis; K is the kinetic constant; T is the time; C∞ is the equilibrium percentage of hydrolyzed starch; AUC S is the area under the curve of the sample; and AUC C is the area under the curve of the control (the same amount of white bread or glucose as the sample).

[0052] The results are shown in Table 1. Figure 1 As shown in Table 1, the intervention of bamboo leaf flavonoids and pullulanase alone can reduce the hydrolysis rate of yam powder, and the combined intervention of the two can further reduce the hydrolysis rate of yam powder in a dose-dependent manner, and the eGI of yam powder is reduced to 61.09, 60.13 and 55.57, respectively.

[0053] Obviously, on the one hand, bamboo leaf flavonoids can interact with the hydrophobic helical structure in starch, such as amylose, to form a complex and form a coating on the surface of yam powder particles, which can prevent the contact of hydrolytic enzymes by inhibiting the swelling of yam powder particles, maintaining the crystal structure and forming a physical barrier, and delaying digestion. On the other hand, the multi-hydroxyl structure of bamboo leaf flavonoids can competitively bind to digestive enzymes, thereby reducing the binding of digestive enzymes to starch and changing the conformation and activity of digestive enzymes. Numerous studies have shown that the flexibility of the skeleton, the spatial site resistance and the number of hydroxyl groups of flavonoids have a major regulatory effect on the interaction with starch. The carbon-carbon double bond at C2 and C3 of the flavonoid ring and the hydroxyl group at R3 position of the carbon ring have an impact on the inhibition ability of α-amylase and α-glucosidase, respectively.

[0054] In addition, as a starch debranching enzyme, pullulanase can modify the structure of starch in yam powder, on the one hand, the generated amylose rearrangement and recombination with amorphous regions, reducing the number of enzyme attack sites, on the other hand, to promote the formation of amylose and bamboo leaf flavonoids, proteins, lipids and other compounds.

[0055] Example 2: Effect of bamboo leaf flavonoids and pullulanase on the reconstitution of yam powder

[0056] Yam powder preparation: same as example 1.

[0057] Reconstitution test: 2g of sample was weighed in a 50mL centrifuge tube to make a 10%(m / v) suspension, placed in a 60℃ water bath for 30min, centrifuged at 4000r / min for 20min, the supernatant was dried to constant weight, and the precipitate was weighed. The specific calculation formula of water absorption index (WAI), water solubility index (WSI) and swelling power (SP) is as follows:

[0058]

[0059]

[0060]

[0061] In the formula, m is the mass of the sample, g; m1 is the dry weight of the supernatant, g; m2 is the wet weight of the precipitate, g.

[0062] The results showed that bamboo leaf flavonoids alone can reduce the water absorption of yam powder and improve the water solubility of yam powder, but has no significant effect on the swelling power of yam powder. Pullulanase alone can reduce the water absorption and swelling power of yam powder and improve the water solubility of yam powder. It is worth noting that the combined use of the two at this dosage did not further enhance the effect on the reconstitution of yam powder.

[0063] As Figure 2 shown, the separate intervention of bamboo leaf flavonoids / pullulanase can significantly reduce the WAI of yam powder (504.35%→448.49% / 100.59%), and the combined intervention of the two can further reduce the WAI of yam powder (81.48%~104.89%). This may be because pullulanase reduces the degree of starch branching, generating more soluble components such as amylose, and these amylose interacts with bamboo leaf flavonoids, reducing the exposure of hydroxyl groups that can form hydrogen bonds with water.

[0064] The single intervention of bamboo leaf flavonoids and pullulanase significantly improved the WSI of yam powder (9.02%→17.76% / 72.10%). Interestingly, the combined intervention of the two did not further improve the WSI of yam powder (64.30%~69.38%) as expected, but instead inhibited the effect of pullulanase single intervention and showed a dose-dependent manner. This may be because the more amylose and unreacted bamboo leaf flavonoids caused by pullulanase single intervention increased the WSI. When combined intervention, the newly generated amylose and unreacted bamboo leaf flavonoids interacted to inhibit the increase of WSI.

[0065] The single intervention of bamboo leaf flavonoids had no significant effect on the SP of yam powder, the single intervention of pullulanase could significantly reduce the SP of yam powder (5.54 g / g→3.60 g / g), and the combined intervention of the two could further reduce the SP of yam powder and showed a dose-dependent manner (2.28 g / g~3.38 g / g). This may be due to the increase in starch crystallinity. Zou et al. also showed that the increase of WSI and the decrease of SP were related to the formation of amylose-lipid complex, which could form a "shell" on the surface of the particles, preventing its interaction with water (Molecules, 2022, 27(7), 2254.).

[0066] Example 3: Effect of bamboo leaf flavonoids and pullulanase on the rheological properties of yam powder

[0067] Preparation of yam powder: same as Example 1.

[0068] Rheological property test: the sample was mixed with deionized water at a concentration of 10% (w / v), then continuously stirred in a boiling water bath for 30 min to make it completely gelatinized. The gelatinized sample was cooled to 25°C at room temperature. The apparent viscosity was recorded under the condition of shear rate 0.1~100 s -1 The sample was scanned at 0.1% strain (within the linear viscoelastic region), at 0.1~100 rad / s frequency range, and the elastic modulus (G') and viscous modulus (G'') were recorded.

[0069] The results showed that the apparent viscosity of all samples decreased with the increase of shear rate, showing a typical shear thinning behavior, that is, the molecular chain was stretched under the action of shear or the particles were arranged in a straight line along the flow direction, thereby increasing the interlayer shear stress and viscosity.

[0070] As Figure 3As shown, the single intervention of baicalein had no obvious effect on the apparent viscosity of yam powder, but the single intervention of pullulanase could significantly reduce the apparent viscosity of yam powder, which might be related to the soluble ingredients. The combined intervention of the two could increase the apparent viscosity of yam powder (compared with YP+E+0B), because the hydroxyl group of baicalein could compete with water molecules with starch, weaken the interaction between starch and water molecules, and promote the entanglement and aggregation between starch chains.

[0071] The G' and G" of all samples showed strong frequency dependence in the range of 0 rad / s-100 rad / s, and G' > G" indicated that the elastic characteristics dominated in the rheological characteristics of yam powder. The intervention of baicalein and pullulanase both reduced G' and G", which meant that the hydrogen bonds between starch molecular chains were disturbed, thereby affecting the shear stability of the gel network.

[0072] The tan δ value of all samples in the range of 0 rad / s-100 rad / s was less than 1, indicating that a weak gel structure was formed, and the elastic structure was dominant. The tan δ value showed an opposite trend to G' and G", and the tan δ value of YP was the smallest, indicating that the combined treatment of baicalein and pullulanase had a greater impact on the elasticity of the gel system than on the viscosity.

[0073] Example 4: Effect of baicalein content on the in vitro digestibility of enzyme-treated yam powder

[0074] Preparation of yam powder: After washing and peeling fresh yam, it was pre-cooked in a boiling water bath for 30 min and then transferred to a homogenizer for 2 min at 30000 r / min. After adding 1% (w / w) pullulanase, it was stirred in a 60°C water bath for 30 min, and then 0%, 0.5%, 1%, 2%, and 4% (w / w) baicalein was added and stirred in a 90°C water bath for 30 min. After freeze-drying, it was ground through a 60-mesh sieve and named YPE0B, YPE0.5B, YPE1B, YPE2B, and YPE4B, respectively.

[0075] In vitro digestibility: same as Example 1.

[0076] Results Figure 4 As shown, the addition amount of baicalein showed a dose-dependent relationship with the anti-digestibility of yam powder treated with pullulanase, and the eGI of yam powder gradually decreased (60.13→48.29) with the gradual increase of baicalein, indicating strong anti-digestibility. When the addition amount of baicalein was higher than 2% (w / w), the eGI of yam powder was <55, reaching the low GI level, i.e., the blood glucose level of the human body would not rise rapidly after ingesting this food, thereby causing a series of adverse effects.

[0077] Example 5: Effect of baicalein content on the reconstitution of enzyme-treated yam powder

[0078] Preparation of yam powder: Same as in Example 4.

[0079] Impregnation test: Same as in Example 2.

[0080] The results are as follows Figure 5 As shown, when the addition amount is low, i.e., 0.5% (w / w), the effect of bamboo leaf flavonoids on the reconstitution properties of pullulanase-treated yam powder is not significant. When the addition amount is ≥1% (w / w), bamboo leaf flavonoids can further significantly affect the reconstitution properties of pullulanase-treated yam powder, i.e., reduce the water absorption, water solubility, and swelling potential of yam powder, but the degree of influence is still relatively small compared to the degree of influence of pullulanase on yam powder.

[0081] Example 6: Effect of bamboo leaf flavonoid content on the rheological properties of enzyme-treated yam powder

[0082] Preparation of yam powder: Same as in Example 4.

[0083] Rheological property testing: Same as in Example 3.

[0084] The results are as follows Figure 6 As shown, with the increase of bamboo leaf flavonoids, more starch molecules can be bound, inhibiting the interaction between molecular chains and reducing the apparent viscosity of yam powder. Furthermore, with the increase of bamboo leaf flavonoids, the tanδ value gradually approaches 1, indicating that the rheological properties of yam powder gradually approach viscous or liquid-like behavior.

[0085] Example 7: Effects of bamboo leaf yellow / tea polyphenols on the in vitro digestibility of yam powder

[0086] Preparation of yam powder: Same as in Example 1. Only tea polyphenols were used to replace bamboo leaf flavonoids. The group with pullulanase added was named YPE1T, and the group without pullulanase added was named YP1T.

[0087] In vitro digestibility: Same as in Example 1.

[0088] The results are as follows Figure 7 As shown, with or without pullulanase, bamboo leaf flavonoids, at the same level of addition, have a better effect on improving the digestibility of yam powder than tea polyphenols.

[0089] Example 8: Effect of ripening on the color of yam powder.

[0090] Preparation of yam powder: Fresh yams were washed, peeled, and pre-cooked in a boiling water bath for 30 minutes. They were then transferred to a high-speed blender and crushed at 30,000 rpm for 2 minutes. The yams were then freeze-dried and pulverized through a 60-mesh sieve. The pre-cooking step was omitted in the control group.

[0091] The results showed that the browning degree of the ripening group (L=43.02, a=-0.72, b=8.00) was far lower than that of the control group (L=32.14, a=2.71, b=7.42), wherein L represented light and dark, + represented light bias, - represented dark bias; a represented red and green, + represented red bias, - represented green bias; b represented yellow and blue, + represented yellow bias, - represented blue bias.

Claims

1. A low glycemic index yam flour, characterized by, The preparation method of the yam powder comprises the following steps: (1) washing fresh yam, peeling, cooking, crushing into paste to obtain yam paste; (2) adding 1-2% of pullulanase by mass percentage to the yam paste, placing in a 50-70°C water bath and stirring at 30-90 r / min for 20-40 min for enzymolysis; (3) adding 2-4% of bamboo leaf flavonoids by mass percentage to the yam paste after enzymolysis, placing in an 80-100°C water bath and stirring at 30-90 r / min for 20-40 min for modification; (4) drying and crushing the modified yam paste to obtain the yam powder with low glycemic index.

2. The low glycemic index yam flour according to claim 1, wherein, In step (1), the peeled yam is pre-cooked with water at a material-to-liquid ratio of 1:2-1:4 in a boiling water bath for 20-40 min until the yam is fully cooked.

3. The low glycemic index yam flour according to claim 1, wherein, In step (1), the cooked yam is placed in a cell disruptor and crushed at 30000 r / min for 2-4 min until there are no obvious particles.

4. The low glycemic index yam flour according to claim 1, wherein, In step (2), the yam paste is cooled and then pullulanase is added, and the mixture is placed in a 60°C water bath and stirred for 30 min.

5. The low glycemic index yam flour according to claim 1, wherein, In step (3), 2% of bamboo leaf flavonoids by mass percentage is added to the yam paste after enzymolysis, and the mixture is placed in a 90°C water bath and stirred for 30 min.

6. The low glycemic index yam flour according to claim 1, wherein, In step (4), the yam powder is crushed to a particle size of 60-100 mesh.

7. Use of the yam powder according to any one of claims 1-6 in the preparation of food.

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