Preparation method of crisp and fragrant crisp ginkgo

Abstract

The invention discloses a preparation method of crispy crisp gingko, and aims to provide crispy crisp gingko with various flavors selected by people according to different tastes, the invention develops a treatment process for debitterizing and detoxifying gingko, and combines a processing process combining freeze drying and hot air drying, so that the quality of the gingko is maintained, and the taste of the gingko is improved. Compared with the common traditional frying process, the obtained product has better quality, the original flavor and nutritional ingredients of the raw materials can be well reserved, and the problem that the effects cannot be achieved by the production of other methods at present is solved.

Description

Technical Field

[0001] The invention belongs to the field of food processing, and particularly relates to a method for preparing crispy and fragrant ginkgo crisps. Background Art

[0002] Crisp grain foods are favored by consumers for their crispy taste, delicious nutrition, and easy to carry. Crisp grain foods are mainly made based on the puffing process, which is divided into two types: fried and non-fried. Room temperature fried products have a high oil content and have certain health problems. Although the vacuum frying technology developed later can reduce the oil content, it is still above 10%. The non-fried process uses pressure difference puffing drying, freeze drying, pulse jet vacuum microwave drying, extrusion puffing and other technologies to make the product crispy. This method changes the shape of the raw materials, and the equipment of these processes has high energy consumption and complex operation.

[0003] Ginkgo nuts are the dried mature seeds of the Ginkgo biloba plant, which is a medicinal and edible resource. Ginkgo nuts are rich in nutrients and active substances, and are very suitable for development into leisure, health and functional foods. However, ginkgo nuts taste bitter and have certain toxicity, which seriously restricts the development of the ginkgo food industry.

[0004] 4'-O-methylpyridoxine (MPN) can cause symptoms such as spasms, convulsions, and even death, which are the same symptoms of poisoning after excessive consumption of ginkgo nuts. Therefore, MPN is considered to be the main cause of ginkgo nut poisoning. Zou Minmin (2021) used the laccase-syringaldehyde system to completely degrade MPN in the ginkgo nut powder suspension. The endogenous enzymatic hydrolysis-resin adsorption method studied by Zhang et al. (2021) and the membrane filtration method of Zou et al. (2021a) can also achieve a 100% removal rate of MPN in ginkgo nut powder. Biological fermentation also has a degradation effect on MPN. Zou et al. (2021b) studied the deep fermentation of ginkgo nut powder with Aspergillus niger, which can degrade MPN by 40.15%. However, these methods have certain limitations in the development of ginkgo nut products, and more practical ginkgo detoxification methods still need to be developed.

[0005] At present, there are few studies on bitter substances in ginkgo and their removal, and the research on ginkgo detoxification methods is mainly focused on the removal of toxic substances in ginkgo powder. However, powdered raw materials not only limit the development direction of products, but also increase energy consumption during processing. Effective methods for debittering and detoxifying whole ginkgo are urgently needed.

[0006] Based on the above problems, it is urgent to develop a set of processing methods for ginkgo crisps. Summary of the invention

[0007] The technical problem to be solved by the invention is to provide a method for preparing crispy and fragrant ginkgo crisps.

[0008] The present invention adopts the following technical scheme: comprising the following steps:

[0009] S1: Select ripe and fresh ginkgo nuts, peel off the shells, and pick out the ginkgo kernels that are full and tough;

[0010] S2: Use alkali method to peel the kernels. The peeled kernels are heated to 80℃ with 1.5% (w / v) hydrogen peroxide.

[0011] Soak in sodium chloride solution for 30 seconds, then rinse and peel with cold water;

[0012] S3: Debittering and detoxifying: Soak the peeled ginkgo kernels in distilled water at room temperature for 1 day, then soak them in 0.45% (w / v) sodium carbonate solution in a 75°C water bath for 7 hours, cool to room temperature, and boil in boiling water for 2 hours.

[0013] times, 30 minutes each time;

[0014] S4: The cooked ginkgo kernels were ultrasonicated at 40°C, 480W, 40KHZ for 5 min, then infiltrated with 20% (w / v) white sugar solution in a 40°C water bath for 1 h. The infiltrated ginkgo kernels were placed in a -20°C ice bath.

[0015] Pre-freeze in the box;

[0016] S5: freeze-dry the pre-frozen ginkgo nuts in a freeze dryer for 0.5 h, then take them out and place them in a refrigerator at 4°C

[0017] Evenly wet;

[0018] S6: Use hot air circulation oven for drying, set the temperature to 45℃, and adjust the temperature to 60℃ after 17h.

[0019] After 100 minutes, the drying is completed and the ginkgo crisps are produced. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 It is the result of the influence of different methods on the bitterness intensity of ginkgo nuts;

[0022] Figure 2 This is the result of the effects of different methods on the MPN content of ginkgo;

[0023] Figure 3This is the analysis result of the interaction effect on the bitterness intensity of ginkgo nuts;

[0024] Figure 4 The effect of pretreatment methods on the crisp texture of ginkgo nuts;

[0025] Figure 5 The effect of different freeze-drying time on the hardness and crispness of Ginkgo Crisp;

[0026] Figure 6 The effect of different hot air drying temperatures on the hardness and crispness of Ginkgo Crisp;

[0027] Figure 7 The effect of different osmotic concentrations of white sugar on the hardness, crispness and sensory perception of Ginkgo Crisp. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the examples. The equipment and reagents used in each embodiment and test example can be obtained from commercial sources unless otherwise specified. The specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0029] Based on the information contained in this application, it is easy for those skilled in the art to make various changes to the precise description of the present invention without departing from the spirit and scope of the appended claims. It should be understood that the scope of the present invention is not limited to the defined process, property or component, because these embodiments and other descriptions are only for illustrating specific aspects of the present invention. In fact, various changes that the technicians in this field or related fields can obviously make to the embodiments of the present invention are all covered within the scope of the appended claims.

[0030] In order to better understand the present invention but not to limit the scope of the present invention, all the numbers used in this application to express the amount, percentage, and other numerical values ​​should be understood as modified by the word "approximately" in all cases. Therefore, unless otherwise specified, the numerical parameters listed in the specification and the appended claims are approximate values, which may be changed according to the different ideal properties attempted to be obtained. Each numerical parameter should at least be regarded as obtained based on the reported significant figures and by conventional rounding methods. In the present invention, "about" means within 10% of a given value or range, preferably within 5%.

[0031] In the following embodiments of the present invention, when the temperature is not particularly limited, it is room temperature. Room temperature refers to the natural room temperature in four seasons without additional cooling or heating treatment, and is generally controlled at 10-30°C, preferably 15-25°C.

[0032] Unless otherwise specified, the reagents and materials used in the embodiments of the present invention can be purchased from the market.

[0033] The variety of ginkgo was Ma Ling, purchased from Pizhou, Jiangsu, and stored in a 4°C refrigerator. White sugar and food-grade sodium carbonate (soda ash) were purchased from Zhongbai Supermarket, Huazhong Agricultural University; pure coffee powder was purchased from Yunnan Huaka Food Co., Ltd.; food-grade citric acid was purchased from Henan Wanbang Chemical Technology Co., Ltd. Sodium hydroxide and phosphoric acid were both analytical grade and purchased from Sinopharm Chemical Reagent Co., Ltd.; chromatographic grade acetonitrile was purchased from Thermo Fisher Scientific, USA; and MPN standard products were purchased from Shanghai Yuanye Biotechnology Co., Ltd.

[0034] Effects of different treatment methods on bitterness and MPN content of ginkgo:

[0035] Fresh ginkgo nuts were shelled and peeled, and different treatment methods were used to remove bitterness and toxins. After cooling, they were ultrasonicated for 5 minutes at 40°C, 480W, and 40KHZ, and then infiltrated with 20% (w / v) sugar solution in a 40°C water bath for 60 minutes. They were frozen in a -20°C refrigerator, freeze-dried for 1.5 hours, and hot-air dried for 21 hours. Finally, the bitterness intensity and MPN content of ginkgo nuts were measured.

[0036] The methods for removing bitterness and poison are as follows:

[0037] (A) Control: Boil in boiling water for 30 min.

[0038] (B) Multiple boiling: Boil in boiling water for 30 minutes, cool and then boil twice more.

[0039] (C) Soaking at room temperature: Soak in distilled water for 1 day, then boil in boiling water for 30 minutes.

[0040] (D) Acid treatment: soak in 0.5% (w / v) citric acid solution for 1 day and boil in boiling water for 30 minutes.

[0041] (E) Alkali treatment: soak in 0.5% (w / v) sodium carbonate solution for 1 day and boil in boiling water for 30 minutes.

[0042] (F) Soaking at room temperature and boiling multiple times: Soak in distilled water for 1 day, boil in boiling water for 30 minutes, cool and then boil twice more.

[0043] (G) High temperature acid treatment: soak in 70°C, 0.5% (w / v) citric acid solution for 7 h, and boil in boiling water for 30 min.

[0044] (H) High temperature alkali treatment: soak in 70°C, 0.5% (w / v) sodium carbonate solution for 7 hours, and boil in boiling water for 30 minutes.

[0045] (I) Soaking at room temperature and high temperature alkali treatment: soak in distilled water for 1 day, soak in 70°C, 0.5% (w / v) sodium carbonate solution for 7 hours, and boil in boiling water for 30 minutes.

[0046] (J) Soaking at room temperature, high temperature acid treatment, and multiple boilings: soak in distilled water for 1 day, soak in 70°C, 0.5% (w / v) citric acid solution for 7 hours, boil in boiling water for 30 minutes, cool and repeat boiling twice.

[0047] (K) Soaking at room temperature, high temperature alkali treatment, multiple boilings: soak in distilled water for 1 day, soak in 70°C, 0.5% (w / v) sodium carbonate solution for 7 hours, boil in boiling water for 30 minutes, cool and repeat boiling twice.

[0048] Bitterness sensory evaluation method:

[0049] 10 sensory evaluators were selected to form a sensory panel, and all members had no taste disorder or related medical history. The sensory evaluation panel was trained twice a week for 21 days using the bitterness scale method, so that the sensory panel members could reach a consensus on the intensity of each bitterness. Pure coffee powder with a purity of ≥99% was used as a reference, and the bitterness intensity was divided according to the bitterness level of 1-9. Coffee solutions of 0g / ml, 0.01g / ml, 0.03g / ml, 0.05g / ml, and 0.10g / ml were prepared, corresponding to the bitterness levels of 1, 3, 5, 7, and 9. The bitterness sensory evaluation table is shown in Table 1.

[0050] After the training, the sensory evaluation team members conducted a sensory evaluation of the ginkgo samples. Before each evaluation, they rinsed their mouths with water, randomly selected a ginkgo nut and tasted it. After the ginkgo flavor fully diffused to the root of the tongue, they stayed there for 10 seconds, then spit it out, rinsed their mouths, and determined the bitterness level. Each sample was repeated twice, with an interval of 10 minutes each time.

[0051] Table 1 Bitterness sensory evaluation table

[0052]

[0053] MPN Extraction Method:

[0054] Accurately weigh 2.00g of ginkgo powder in a 50mL centrifuge tube, add 25mL of ultrapure water and adjust the pH to 2.5 with phosphoric acid, ultrasonicate for 1h at 45℃, 480W, 40KHZ, and then centrifuge for 30min at 4℃, 11000r / min. The collected supernatant was rotary evaporated to dryness at 45℃, then dissolved with 10mL of distilled water and freeze-dried for HPLC analysis.

[0055] The MPN content was determined by high performance liquid chromatography (Gong et al 2020). The chromatographic column was InsertSustainAQ-C18 5um; the mobile phase A was 0.1% phosphoric acid aqueous solution, and the mobile phase B was acetonitrile; the gradient elution was: 0min was 4% A, 96% B, 15min was 8.5% A, 91.5B, 30min was 15% A, 85% B, 40min was 4% A, 96% B; the flow rate was 1.0ml / min; the injection volume was 10μL; the UV detection wavelength was 291nm.

[0056] Accurately weigh 1.3 mg of MPN standard, dissolve it in 5 mL of ultrapure water (adjust pH to 2.5 with phosphoric acid), shake well, and prepare 0.26 mg / mL MPN standard solution. Accurately aspirate 0.025 mL, 0.250 mL, 0.500 mL, 0.750 mL, 1.000 mL, and 1.250 mL of the mother liquor, respectively, and then dilute to 5 mL with ultrapure water at pH 2.5 to prepare a series of standard solutions of 1.3 μg / mL, 13.0 μg / mL, 26.0 μg / mL, 39.0 μg / mL, 52.0 μg / mL, and 65.0 μg / mL. Inject the sample according to the above liquid phase detection method and record the corresponding peak area. With the injection concentration (μg / mL) as the horizontal coordinate (x) and the peak area as the vertical coordinate (y), perform linear regression: the linear regression equation of MPN is Y=28033X-23181, R 2 =0.9992.

[0057] The extracted MPN sample was dissolved in 2 mL of ultrapure water and adjusted to pH 2.5 with phosphoric acid, vortexed for 1 min, filtered with a 0.45 μm filter, and then the MPN content in ginkgo was determined using the above method.

[0058] Ten treatment methods were used to remove bitterness and toxins from ginkgo nuts. After drying, the bitterness intensity and MPN content were measured. The results are as follows: Figure 1 and 2As shown. The bitterness intensity of ginkgo after 10 treatments was significantly reduced compared with the control group (p < 0.05). In the single treatment, multiple boiling and alkali treatment had the best effect of removing bitterness, while the acid treatment had a poor effect, only slightly better than the room temperature soaking treatment. However, after these treatments, ginkgo still had a relatively obvious bitterness, and the bitterness intensity was above 3.00. In the combined treatment, except for the high-temperature acid treatment, the bitterness of ginkgo was not much different from that of the acid treatment (p > 0.05), and the bitterness intensity of ginkgo after other combined treatments was significantly different from that after the single treatment (p < 0.05). Among them, high-temperature acid treatment and multiple boiling can reduce the bitterness intensity to 1.67, greatly reducing the bitterness of ginkgo; high-temperature alkali treatment can remove the bitterness of ginkgo to a very weak level, with a bitterness intensity of 1.25. Combined multiple boiling can further reduce the bitterness of ginkgo to 1.15, but the difference between the two is not significant (p > 0.05). In summary, high-temperature acid and alkali treatment combined with multiple boiling can effectively remove the bitterness of ginkgo nuts to a level acceptable to consumers, but the effect of removing bitterness with alkali treatment is better than that with acid treatment.

[0059] The MPN content of ginkgo after boiling was 6.11 μg / g, and the MPN content decreased significantly after 10 treatments (p < 0.05). In the single treatment, multiple boiling removal effects were better, and the MPN content decreased by 35.35% compared with the control group, which was significantly lower than the acid treatment and alkali treatment (p < 0.05). The MPN content after alkali treatment was significantly reduced compared with acid treatment and water soaking (p < 0.05), because MPN was unstable in an alkaline environment, which was consistent with the research results of Yu Yuanyuan (2017). Compared with the single treatment, the MPN content of combined treatment decreased significantly (p < 0.05). After high-temperature acid treatment and alkali treatment, the MPN content decreased by 69.27% ​​and 57.06% respectively compared with normal temperature acid and alkali treatment. This is because MPN is more unstable at high temperature, and the MPN content after high-temperature acid treatment is significantly lower than that of high-temperature alkali treatment (p < 0.05). After multiple combined boiling, the MPN content of high-temperature acid treatment dropped to 1.24 μg / g, which was lower than the 1.63 μg / g after high-temperature alkali treatment. The results showed that the detoxification effect of alkali treatment was better than that of acid treatment at room temperature, while that of acid treatment was better than that of alkali treatment under high temperature conditions. However, the MPN content in ginkgo nuts was extremely low after the combined treatment, which was reduced by more than 97% compared with the MPN content in fresh ginkgo nuts. Therefore, combined with the effects of different methods on the bitterness intensity of ginkgo nuts, room temperature soaking, high temperature alkali treatment, and multiple boiling were used to debitter and detoxify ginkgo nuts.

[0060] Three single factors, namely sodium carbonate concentration, soaking temperature and soaking time, which have a greater impact on the bitterness intensity of ginkgo, were selected for response surface experiment, and the results are shown in Table 2.

[0061] Table 2 Response surface experimental design and results

[0062] Serial number A: Sodium carbonate concentration B: Soaking temperature C: Soaking time Bitterness intensity 1 0.3 65 6 3.19 2 0.7 65 6 2.00 3 0.3 75 6 2.36 4 0.7 75 6 1.00 5 0.3 70 4 3.90 6 0.7 70 4 2.57 7 0.3 70 8 2.60 8 0.7 70 8 1.15 9 0.5 65 4 3.00 10 0.5 75 4 2.38 11 0.5 65 8 2.36 12 0.5 75 8 1.00 13 0.5 70 6 1.00 14 0.5 70 6 1.21 15 0.5 70 6 1.36 16 0.5 70 6 1.50 17 0.5 70 6 1.07

[0063] The quadratic polynomial regression equation was fitted for the bitterness intensity of ginkgo, and the result was 1.23-0.67A-0.48B-0.59C-0.04AB-0.03AC-0.19BC+0.64A 2 +0.27B 2 +0.69C 2 The results of variance analysis of the regression model are shown in Table 3.

[0064] Table 3 Analysis of variance of regression model

[0065] Sources of variance sum of squares Degrees of Freedom Mean Square F-number P-value Model 12.74 9 1.42 41.63 <0.0001 A-Sodium carbonate concentration 3.55 1 3.55 104.5 <0.0001 B- Soaking temperature 1.81 1 1.81 53.17 0.0002 C- Soaking time 2.81 1 2.81 82.64 <0.0001 AB 0.0078 1 0.0078 0.2281 0.6475 AC 0.0036 1 0.0036 0.1059 0.7544 BC 0.14 1 0.14 4.12 0.082 <![CDATA[A 2 ]]> 1.72 1 1.72 50.5 0.0002 <![CDATA[B 2 ]]> 0.3084 1 0.3084 9.07 0.0196 <![CDATA[C 2 ]]> 1.99 1 1.99 58.6 0.0001 Residue 0.238 7 0.034 Lack of Fit 0.0706 3 0.0235 0.5628 0.6677 Pure Error 0.1673 4 0.0418 Total variation 12.98 16

[0066] As shown in Table 3, the model has p < 0.0001, the lack-of-fit term p = 0.6677, and R 2 The value is 0.9817. This shows that the model has an acceptable degree of fit and the actual and predicted values ​​have a high correlation. Therefore, the model can accurately reflect the main factors affecting the bitterness of ginkgo crunch. From the F value, it can be seen that the order of the three factors affecting the bitterness intensity of ginkgo crunch is A>C>B, that is, sodium carbonate concentration>soaking time>soaking temperature.

[0067] The analysis results of the interaction of various factors on the bitterness intensity of ginkgo are as follows: Figure 3 shown.

[0068] Depend on Figure 3 The interaction between sodium carbonate concentration, soaking temperature and soaking time on the bitterness intensity of ginkgo nuts was analyzed. The experimental data were optimized and predicted, and the best process for removing the bitterness of ginkgo crisps was obtained: sodium carbonate concentration of 0.455%, soaking temperature of 75℃, soaking time of 7h. Under this process condition, the predicted bitterness intensity of ginkgo crisps was 1.00.

[0069] Three verification experiments were carried out according to the optimized process. The actual operation was a sodium carbonate concentration of 0.45%, a soaking temperature of 75°C, and a soaking time of 7 h. The final bitterness intensity of the ginkgo crisp was 1.05, which was close to the model prediction result, indicating that the model fitting scheme for the bitterness intensity of ginkgo crisp is feasible.

[0070] Based on single factor, response surface analysis was carried out with bitterness intensity as the index, and the optimal ginkgo debittering and detoxification process was obtained as follows: sodium carbonate concentration 0.45%, soaking temperature 75℃, soaking time 7h, and boiling twice.

[0071] Making of Ginkgo Crisp:

[0072] The debittered and detoxified ginkgo nuts were treated with US and US+OD respectively. The US treatment conditions were 40℃, 480W, 40KHZ, 5min; the US+OD treatment was the above conditions. After US treatment, 20% (w / v) white sugar solution was OD treated for 1h at 40℃. After freezing in a -20℃ refrigerator, it was dried in a vacuum freeze dryer for 1.5h, kept wet in a 4℃ refrigerator for 12h, and then dried with hot air at 40℃ for 17h and 60℃ for 100min. The control group was the ginkgo nuts directly dried after debittering and detoxification. The effects of US treatment and US+OD treatment on the crisp quality of ginkgo nuts were studied by texture.

[0073] The hardness and crispness of the ginkgo crisp were determined using a TA.XT plus texture analyzer. The hardness and crispness of the ginkgo crisp were determined by shearing using a tool probe hot air drying P / BS. The samples were measured 10 times in parallel. The basic measurement parameters are shown in Table 4.

[0074] Table 4 Texture parameter settings

[0075]

[0076] By measuring the hardness and brittleness, the effects of the two pretreatment methods, US and US+OD, on the quality of ginkgo brittle were studied. The hardness was expressed by the maximum crushing peak value. The larger the peak value, the greater the hardness. The brittleness was expressed by the crushing distance. The shorter the distance, the better the brittleness. Figure 4 shown.

[0077] like Figure 4 As shown in the figure, compared with the control group, the hardness of the ginkgo crisp after US treatment decreased significantly (p < 0.05), and the crushing distance decreased significantly (p < 0.05), indicating that the brittleness of the ginkgo crisp increased. This is because the ginkgo cells ruptured and formed microscopic channels after ultrasound treatment, and the pores in the tissue became larger. Therefore, the shrinkage degree of the ginkgo was reduced during the hot air drying process, resulting in a decrease in the hardness and increase in the brittleness of the ginkgo. After US+OD treatment, the hardness increased significantly compared with US (p < 0.05), the crushing time increased but the difference was not significant, and the crushing distance was significantly reduced compared with the control group (p < 0.05), and the hardness increased but was not significant. The reason is that the infiltration of sugar supports the tissue structure of the ginkgo, and reduces the range of cell wall expansion, making the final structure of the ginkgo crisp more compact. Therefore, the ginkgo crisp after US+OD treatment has better hardness and brittleness.

[0078] Effects of freeze drying and hot air drying on ginkgo crispness:

[0079] The debittered and detoxified ginkgo nuts were dried in a vacuum freeze dryer for 0 h, 0.5 h, 1 h, 1.5 h, and 2 h, kept wet in a 4 °C refrigerator for 12 h, and then dried with hot air at 40 °C for 17 h and at 60 °C for 100 min. The freeze-drying time was determined by studying the effect of FD time on the drying characteristics and quality of ginkgo nuts.

[0080] The debittered and detoxified ginkgo nuts were dried in a vacuum freeze dryer for 0.5 h, kept in a 4°C refrigerator for 12 h, and then dried with hot air at 40°C, 45°C, 50°C, 55°C, and 60°C until the weight of the ginkgo nuts no longer changed. The hot air drying temperature was determined by studying the effect of hot air drying temperature on the drying characteristics and quality of ginkgo nuts.

[0081] The effects of freeze-drying time on the quality of ginkgo crisps were studied by measuring the hardness and crispness of ginkgo crisps after different freeze-drying times. Figure 5 As shown. After freeze-drying, the hardness of the ginkgo crisp was significantly reduced, and the brittleness was significantly increased (p < 0.05). Freeze-drying can form a porous structure inside the product. These structures can promote the internal diffusion of water in the ginkgo during the drying process, making the drying more uniform. At the same time, it can also reduce the collapse of the ginkgo structure and increase a certain degree of crispness. After 0.5h, the hardness and breaking distance of the ginkgo crisp reached 3433g and 0.574mm, respectively. Compared with the untreated group, the hardness decreased by 20.23% and the breaking distance decreased by 24.13%. After that, as the processing time continued to increase, the hardness and brittleness of the ginkgo crisp changed less. Therefore, better hardness and brittleness can be obtained after freeze-drying for 0.5h.

[0082] The effects of hot air drying temperatures on the quality of Ginkgo Crisp were studied by measuring the hardness and crispness of Ginkgo Crisp at different hot air drying temperatures. Figure 6 As shown. Hot air drying temperature can significantly affect the hardness and crispness of ginkgo crisp (p < 0.05). As the temperature rises, the hardness of ginkgo crisp gradually increases. The hardness of ginkgo crisp dried at 60℃ is 28.27% higher than that at 40℃; the crispness of ginkgo crisp is best at 45℃, and the breaking distance is reduced by 28.41% and 33.96% compared with 40℃ and 60℃, respectively. The reason for such a result may be that the increase in temperature will affect the structure of starch, protein, etc. in ginkgo, thereby affecting the texture properties of ginkgo crisp. From the results, ginkgo crisp dried at 45℃ and 50℃ may have better crispness.

[0083] Effect of sugar concentration on the quality of Ginkgo Crisp:

[0084] The effect of osmotic concentration of white sugar on the quality of Ginkgo Crisp was studied by measuring the hardness, crispness and sensory score of Ginkgo Crisp. Figure 7As shown in the results, the osmotic concentration of white sugar has a significant effect on the texture of ginkgo crisps. When the osmotic concentration of white sugar increases, the hardness of the ginkgo crisps shows a significant upward change (p < 0.05), while the brittleness first increases and then decreases. When the concentration is 30%, the breaking distance increases significantly (p < 0.05). This is because the osmotic dehydration of ginkgo nuts gradually increases with the increase in the concentration of the osmotic solution, and the infiltration of sugar will also make the tissue structure of the ginkgo nuts tighter, resulting in an increase in the hardness of the ginkgo crisps. The reason for the increase in brittleness may be the loss of elasticity of the ginkgo nuts tissue after osmosis. However, when the sugar osmotic concentration is high, the ginkgo nuts contain more white sugar, which will hinder the dehumidification rate in the later stage of drying, resulting in a higher moisture content in the ginkgo nuts, thereby reducing the brittleness of the ginkgo crisps. In terms of sensory scores, as the osmotic concentration of white sugar increases, in addition to affecting the texture of the white granulated sugar crisp, it also affects the color and sweetness of the white granulated sugar crisp, making the sensory score increase first and then decrease with the increase of white granulated sugar concentration, reaching the highest value at a concentration of 20%, and significantly higher than the sensory scores at concentrations of 15% and 25% (p < 0.05). At this time, the white granulated sugar crisp has an appropriate sweetness and a good overall crispness. Therefore, based on the effect of the osmotic concentration of white granulated sugar on the texture indicators and sensory scores of the white granulated sugar crisp, a white granulated sugar concentration of 20% was finally selected as the osmotic solution.

[0085] Through single factor experiments, the drying and seasoning process of ginkgo crisps was determined as follows: white sugar osmotic concentration 20%, freeze drying time 0.5h, hot air drying temperature 45℃. Under these process conditions, the ginkgo crisps obtained were bright in color, crisp and delicious, with appropriate sweetness and good unique ginkgo flavor.

[0086] In summary, the present application has developed a method for processing non-toxic and non-bitter crispy ginkgo nuts, the specific process of which is:

[0087] S1: Select ripe and fresh ginkgo nuts, peel off the shells, and pick out the ginkgo kernels that are full and tough;

[0088] S2: Use alkaline method to peel the kernels. Soak the peeled kernels in 1.5% (w / v) sodium hydroxide solution at 80°C for 30 seconds, then rinse and peel them with cold water;

[0089] S3: Debittering and detoxifying: The peeled ginkgo kernels were soaked in distilled water at room temperature for 1 day, then soaked in 0.45% (w / v) sodium carbonate solution in a 75°C water bath for 7 hours, cooled to room temperature, and boiled in boiling water twice, each time for 30 minutes;

[0090] S4: The cooked ginkgo nuts are ultrasonically treated at 40°C, 480W, and 40KHZ for 5 minutes, then infiltrated with 20% (w / v) white sugar solution in a 40°C water bath for 1 hour, and the infiltrated ginkgo nuts are pre-frozen in a -20°C refrigerator; S5: The pre-frozen ginkgo nuts are freeze-dried for 0.5 hours using a freeze dryer, and then taken out and refrigerated in a 4°C refrigerator to even out moisture; S6: Drying is performed in a hot air circulation oven with the temperature set to 45°C. After 17 hours, the temperature is adjusted to 60°C, and drying is terminated after 100 minutes to produce ginkgo crisps.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing crispy and fragrant ginkgo crisps, characterized in that: The method comprises the following steps: S1: Select ripe and fresh ginkgo nuts, peel off the shells, and pick out the ginkgo kernels that are full and tough; S2: Use alkaline method to peel the kernels. Soak the peeled kernels in 1.5% (w / v) sodium hydroxide solution at 80°C for 30 seconds, then rinse and peel them with cold water; S3: Debittering and detoxifying: The peeled ginkgo kernels were soaked in distilled water at room temperature for 1 day, then soaked in 0.45% (w / v) sodium carbonate solution in a 75°C water bath for 7 hours, cooled to room temperature, and boiled in boiling water twice, each time for 30 minutes; S4: The cooked ginkgo kernels were ultrasonicated at 40°C, 480W, and 40KHZ for 5 minutes, and then infiltrated with 20% (w / v) white sugar solution in a 40°C water bath for 1 hour. The infiltrated ginkgo kernels were pre-frozen in a -20°C refrigerator; S5: freeze-dry the pre-frozen ginkgo kernels in a freeze dryer for 0.5 h, take them out and place them in a 4°C refrigerator to keep them moist; S6: Use a hot air circulation oven for drying, set the temperature to 45°C, adjust the temperature to 60°C after 17 hours, and end the drying after 100 minutes to produce ginkgo crisps.

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