Preparation process for improving flavor quality of low-sugar cranberry fruit leather

Abstract

This invention relates to the field of food processing technology. The invention provides a compound sugar-permeating solution and a process for preparing low-sugar cranberry preserves using it, comprising the following steps: (1) thawing and blanching cranberry raw materials to obtain intermediate product 1; (2) placing intermediate product 1 in the compound sugar-permeating solution for vacuum sugar permeation treatment, and then drying to obtain the final product. By employing the compound sugar-permeating solution and vacuum sugar permeation treatment described in this invention, the textural properties of low-sugar cranberry preserves can be effectively improved, enhancing the storage stability of the preserves; it can also inhibit the loss of anthocyanins, vitamin C, and polyphenols, thereby preparing a higher quality low-sugar cranberry preserve with a balanced sweet and sour taste and rich fruit flavor.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, and in particular to a preparation process for improving the flavor quality of low-sugar cranberry preserves. Background Technology

[0002] cranberry( Vaccinium macrocarpon Cranberries, also known as cranberries, belong to the genus Vaccinium in the family Ericaceae. They are now being cultivated on a large scale in regions such as Fuyuan, Heilongjiang Province. Cranberries are rich in anthocyanins, polyphenols, flavonoids, and other bioactive substances, possessing excellent antioxidant and health-promoting functions. Due to their unique health benefits, cranberries have long received widespread attention, leading to a gradual increase in demand and related products. However, fresh cranberries are quite acidic, resulting in a less palatable taste and making them unsuitable for direct consumption. Deep processing is the main way to increase their added value.

[0003] The production of dried fruit has a long history in my country. Low-sugar dried fruit (40%–55% sugar content) aligns with nutritional and health principles and has become an industry trend. However, the processing of this type of product mostly follows the traditional atmospheric pressure sugar infusion process, which generally suffers from low processing efficiency, severe browning, and loss of heat-sensitive nutrients. It often faces problems such as slow sugar infusion, low product fullness, and easy browning. In particular, cranberries have a rich waxy layer on their skin and four unique internal cavities, leading to poor results from traditional sugar infusion methods and a tendency for wrinkling and collapse after processing. Currently, there are no reports on sugar infusion processes specifically tailored to the characteristics of cranberries or on the changes in the quality of dried fruit. Therefore, it is crucial to explore a processing method for cranberry dried fruit that can solve existing processing problems and achieve higher flavor and quality. Summary of the Invention

[0004] The purpose of this invention is to provide a preparation process for improving the flavor and quality of low-sugar cranberry preserves. The technical solution of this invention can effectively solve problems such as slow sugar penetration, low product fullness, severe browning, and loss of heat-sensitive nutrients, and obtain low-sugar cranberry preserves with better flavor and quality.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: The present invention provides a composite sugar solution comprising a composite sugar solution with a mass concentration ratio of (50-60):(0.2-1.0):(0.2-1.0):(0.35-0.75), L-cysteine, calcium chloride, and xanthan gum.

[0006] Preferably, the compound sugar solution is composed of sucrose, fructose syrup and erythritol in a mass ratio of (1~4):(1~3):1.

[0007] This invention also provides a preparation process for improving the flavor quality of low-sugar cranberries, comprising the following steps: (1) Thaw the cranberry raw material and blanch it to obtain intermediate product 1; (2) The intermediate product 1 is placed in the composite sugar solution for vacuum sugar infiltration treatment, and then dried to obtain the product.

[0008] Preferably, the temperature of blanching in step (1) is 80~88℃ and the blanching time is 80~100s.

[0009] Preferably, the mass-to-volume ratio of the cranberry fruit raw material to the compound sugar solution is 1g:(1~5)mL.

[0010] Preferably, the vacuum sugar infiltration treatment in step (2) is performed as follows: sugar infiltration treatment at 52~58℃ under vacuum for 4~7h, and then sugar infiltration treatment at 25±1℃ for 10~14h.

[0011] Preferably, the vacuum degree of the vacuum condition is -(0.08~0.09)MPa.

[0012] Preferably, the drying temperature in step (2) is 55~65°C, and the cranberry low-sugar candy is dried to a moisture content of 20~25%.

[0013] The present invention also provides a low-sugar cranberry preserve prepared by the aforementioned process.

[0014] Preferably, the total sugar content of the cranberry low-sugar preserve is <55% based on glucose.

[0015] By adopting the above technical solution, the present invention has the following beneficial effects: This invention effectively solves problems such as slow sugar infusion, low product fullness, severe browning, and loss of heat-sensitive nutrients through the composite sugar infusion solution and vacuum sugar infusion process, along with corresponding scientific parameters. Experiments also show that the preparation process described in this invention can effectively improve the textural properties of low-sugar cranberry preserves, ensuring optimal hardness, chewiness, and elasticity, and enhancing the storage stability of the preserves. In terms of color, it effectively maintains the bright red color of cranberries; it can also significantly inhibit the loss of anthocyanins, vitamin C, polyphenols, and flavonoids, maximizing the retention of functional components. The vacuum sugar infusion also better maintains the integrity of the cytoskeleton, reducing cell wall collapse and damage, which provides a microstructural basis for excellent quality characteristics. The low-sugar cranberry preserves prepared by this invention have a balanced sweet and sour flavor and a rich fruity aroma. Attached Figure Description

[0016] Figure 1The effect of vacuum sugar infiltration time on the total sugar content of cranberry preserves (different letters indicate significant differences). P <0.05); Figure 2 The effect of vacuum sugar infiltration temperature on the total sugar content of cranberry preserves (different uppercase and lowercase letters indicate significant differences). P <0.05); Figure 3 The effect of compound sugar solution concentration on the total sugar content of vacuum-sugared cranberry preserves (different uppercase and lowercase letters indicate significant differences). P <0.05); Figure 4 The effect of different sugar infusion methods on the total sugar and reducing sugar content of cranberry preserves (different uppercase and lowercase letters indicate significant differences between different groups). P <0.05); Figure 5 The effect of different sugar infusion methods on the rehydration rate of cranberry preserves (letters between different groups at the same time indicate significant differences between different groups). P <0.05)); Figure 6 The effects of different sugar infusion methods on the types and relative contents of aroma components in cranberry preserves; Figure 7 Figure showing the effect of different sugar infiltration methods on the cell structure of cranberry preserves ( Figure 7 In the diagram, A represents a vacuum-soaked sample, B represents an ultrasonic-soaked sample, C represents a sample soaked under normal pressure, D represents a sample soaked under microwave pressure, and E represents a freeze-dried cranberry sample; 300×). Detailed Implementation

[0017] This invention provides a composite sugar infusion solution, comprising a composite sugar solution, L-cysteine, calcium chloride, and xanthan gum. The preferred mass concentration ratio of the composite sugar solution, L-cysteine, calcium chloride, and xanthan gum is (50-60):(0.2-1.0):(0.2-1.0):(0.35-0.75), further preferably (52-57):(0.5-0.9):(0.5-0.9):(0.4-0.7), and even more preferably 55:0.8:0.8:0.6.

[0018] In this invention, the compound sugar solution is composed of sucrose, fructose syrup and erythritol, and the mass ratio of sucrose, fructose syrup and erythritol is preferably (1~4):(1~3):1, further preferably (2~3.5):(1.5~2.5):1, and even more preferably 3:2:1.

[0019] In this invention, sucrose maintains the plump shape of the fruit, high-fructose corn syrup improves texture and color due to its high osmotic pressure, and erythritol, as a sweetener, reduces the calorie value of the product and improves the overly sweet taste of the dried fruit. This invention uses a compound sugar infusion of sucrose, high-fructose corn syrup, and erythritol, utilizing the differences in the physicochemical properties of different sugars to produce a synergistic effect, thereby obtaining high-quality, low-sugar cranberry dried fruit.

[0020] This invention also provides a preparation process for improving the flavor quality of low-sugar cranberries, comprising the following steps: (1) Thaw the cranberry raw material and blanch it to obtain intermediate product 1; (2) The intermediate product 1 is placed in the composite sugar solution for vacuum sugar infiltration treatment, and then dried to obtain the product.

[0021] In this invention, the cranberry raw material is preferably frozen cranberries of uniform size and full ripeness. Preferably, the frozen cranberries are thawed to a semi-frozen state at room temperature (25±1℃).

[0022] In this invention, the thawed cranberries are blanched. The blanching temperature is preferably 80-88℃, more preferably 82-86℃, and even more preferably 85℃. The blanching time is preferably 80-100s, more preferably 85-95s, and even more preferably 90s.

[0023] In this invention, it is preferable to immediately cool the blanched cranberries and make longitudinal slits on the surface of the fruit to obtain intermediate product 1. The slit treatment described in this invention is to ensure the sugar infiltration effect.

[0024] In this invention, intermediate product 1 is placed in the composite sugar-permeating solution for vacuum sugar permeation treatment. The mass-to-volume ratio of the cranberry raw material to the composite sugar-permeating solution is preferably 1g:(1~5)mL, more preferably 1g:(1.5~3)mL, and even more preferably 1g:2mL. The vacuum sugar permeation treatment of this invention is as follows: intermediate product 1 placed in the composite sugar-permeating solution is first subjected to sugar permeation treatment under vacuum conditions, and then subjected to sugar permeation treatment at room temperature conditions. The temperature of the sugar permeation treatment under vacuum conditions in this invention is preferably 52~58℃, more preferably 53~56℃, and even more preferably 55℃; the vacuum degree is preferably -(0.08~0.09)MPa, more preferably -(0.082~0.088)MPa, and even more preferably -0.085MPa; the sugar permeation treatment time is preferably 4~7h, more preferably 5~6.5h, and even more preferably 6h. In this invention, the sugar infiltration treatment time at room temperature (25±1℃) is preferably 10~14h, more preferably 11~13h, and even more preferably 12h.

[0025] In this invention, after the cranberries have been treated with sugar, they are drained and spread out evenly, and then dried. Preferably, the cranberry preserves are dried to a moisture content of 20-25%, more preferably 21-23%, and even more preferably 22%. The drying temperature is preferably 55-65°C, more preferably 58-62°C, and even more preferably 60°C.

[0026] The present invention also provides a low-sugar cranberry preserve prepared by the aforementioned process.

[0027] In this invention, the total sugar content of the cranberry low-sugar preserve is <55% based on glucose.

[0028] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0029] Example 1

[0030] A preparation process for improving the flavor quality of low-sugar cranberry preserves includes the following steps: (1) Select frozen cranberries of uniform size and fullness, thaw them at room temperature (25±1℃) until they are semi-frozen, blanch them in hot water at 85℃ for 90 seconds and cool them immediately. Make longitudinal cuts on the surface of the fruit to obtain intermediate product 1. (2) According to the mass-volume ratio of frozen cranberries to compound sugar solution of 1g:2mL, intermediate product 1 was placed in the compound sugar solution and treated with sugar solution at 55℃ and vacuum degree -0.085MPa for 6h, and then treated with sugar solution at room temperature for 12h. The compound sugar solution is composed of 55% (mass concentration) compound sugar solution, 0.8% (mass concentration) L-cysteine, 0.8% (mass concentration) calcium chloride and 0.6% (mass concentration) xanthan gum. The compound sugar solution is composed of sucrose, fructose syrup and erythritol in a mass-volume ratio of 3:2:1. (3) After draining the intermediate product 1 after sugar infiltration, spread it evenly and then place it in a 60℃ hot air drying oven to dry until the dry basis moisture content of the dried fruit is controlled at 20%.

[0031] Example 2

[0032] A preparation process for improving the flavor quality of low-sugar cranberry preserves includes the following steps: (1) Select frozen cranberries of uniform size and fullness, thaw them at room temperature (25±1℃) until they are semi-frozen, blanch them in hot water at 88℃ for 80 seconds and cool them immediately. Make longitudinal cuts on the surface of the fruit to obtain intermediate product 1. (2) According to the mass-volume ratio of frozen cranberries to compound sugar solution of 1g:3mL, intermediate product 1 was placed in the compound sugar solution and treated with sugar solution at 52℃ and vacuum degree -0.08MPa for 7h, and then treated with sugar solution at room temperature (25±1℃) for 10h. The compound sugar solution is composed of 60% (mass concentration) compound sugar solution, 0.9% (mass concentration) L-cysteine, 1.0% (mass concentration) calcium chloride and 0.35% (mass concentration) xanthan gum. The compound sugar solution is composed of sucrose, fructose syrup and erythritol in a mass-volume ratio of 3.5:1.5:1. (3) After draining the intermediate product 1 after sugar infiltration, spread it evenly and then place it in a 55℃ hot air drying oven to dry until the dry basis moisture content of the dried fruit is controlled at 25%.

[0033] Example 3

[0034] A preparation process for improving the flavor quality of low-sugar cranberry preserves includes the following steps: (1) Select frozen cranberries of uniform size and fullness, thaw them at room temperature (25±1℃) until they are semi-frozen, blanch them in hot water at 80℃ for 100s and cool them immediately. Make longitudinal cuts on the surface of the fruit to obtain intermediate product 1. (2) According to the mass-volume ratio of frozen cranberries to compound sugar solution of 1g:1mL, intermediate product 1 was placed in the compound sugar solution and treated with sugar solution at 58℃ and vacuum degree -0.09MPa for 4h, and then treated with sugar solution at room temperature (25±1℃) for 14h. The compound sugar solution is composed of 50% (mass concentration) compound sugar solution, 0.5% (mass concentration) L-cysteine, 0.2% (mass concentration) calcium chloride and 0.75% (mass concentration) xanthan gum. The compound sugar solution is composed of sucrose, fructose syrup and erythritol in a mass ratio of 2:2.5:1. (3) After draining the intermediate product 1 after sugar infiltration, spread it evenly and then place it in a 65℃ hot air drying oven to dry until the dry basis moisture content of the dried fruit is controlled at 22%.

[0035] Experimental Example 1

[0036] (a) Single-factor test of hardener

[0037] Blanched cranberries were placed in a 55% compound sugar solution (sucrose:fructose syrup:erythritol = 3:2:1) at a material-to-liquid ratio of 1:2 (g:mL). The compound sugar solution contained 0.6% L-cysteine ​​and 0.5% xanthan gum. Calcium chloride, a hardening agent, was added to the compound sugar solution at concentrations of 0.2%, 0.4%, 0.6%, 0.8%, and 1.0%, respectively. The sugar infusion process was carried out at 55℃ and a vacuum of -0.08 MPa for 7 hours, followed by 12 hours at room temperature. Sensory evaluation of each group of cranberry preserves was performed according to Table 1.

[0038] Table 1 Sensory Quality Evaluation Criteria for Cranberry Dried Fruit

[0039] Table 2. Effects of calcium chloride concentration on sensory scores of cranberry preserves

[0040] Note: Different letters in the same column of data indicate significant differences. P <0.05), the same applies below.

[0041] The results are shown in Table 2. With increasing CaCl2 concentration, the total sensory score of the cranberry preserves showed a trend of first significantly increasing and then decreasing, with the 0.8% CaCl2 treatment group achieving the highest total sensory score of 82.21. When the CaCl2 concentration increased from 0.2% to 0.8%, the tissue morphology score increased from 21.76 to 26.53, and the taste score also reached its highest value of 25.05. When the concentration was 1.0%, both the tissue morphology and taste scores decreased. This may be because excessive calcium ions lead to over-hardening of the cell walls, and high concentrations of residue can mask the cranberry flavor. There was no significant difference in color score among the different CaCl2 treatment groups. P >0.05). The 0.8% group of dried fruit samples were plump, firm, and elastic, with a pleasant sweet and sour taste and no off-flavors. 0.8% was determined to be the optimal dosage of calcium chloride.

[0042] Texture analysis was performed on each group of cranberry preserves. A texture analyzer (TA-XP type) with a P / 5 probe was used. The test speed was 1 mm / s, the pause time was 1s, the deformation was 40%, and the trigger value was 0.5N. Each sample was measured 10 times.

[0043] Table 3. Effects of calcium chloride concentration on the texture of cranberry preserves

[0044] The results showed that as the CaCl2 concentration increased from 0.2% to 0.8%, the firmness of the dried fruit significantly increased from 7.35 N to 10.70 N. P<0.05), when the CaCl2 concentration continued to increase to 1.0%, the firmness, chewiness, and elasticity decreased. This may be because excessively high concentrations of salt solution caused excessive efflux of intracellular water, disrupting the semi-permeability of the cell membrane. With increasing hardener concentration, the elasticity of the dried fruit showed a decreasing trend. Chewiness reached its maximum at a concentration of 0.8% (12.17 mJ), and the overall trend was highly consistent with the firmness. Combined with sensory evaluation, the 0.8% treatment group provided the dried fruit with the best chewiness, effectively preventing the dried fruit from becoming soft and collapsing during processing.

[0045] (II) Single-factor test of color-protecting agent

[0046] Blanched cranberries were placed in a 55% compound sugar solution (sucrose:fructose syrup:erythritol = 3:2:1) at a material-to-liquid ratio of 1:2 (g:mL). The compound sugar solution contained 0.6% calcium chloride and 0.5% xanthan gum. L-cysteine ​​was added to the compound sugar solution at concentrations of 0.2%, 0.4%, 0.6%, 0.8%, and 1.0%, respectively. The sugar infiltration process was carried out at 55℃ and a vacuum of -0.08 MPa for 7 hours, followed by 12 hours at room temperature. Color difference was measured for each group of cranberry preserves. The lightness value (L) of the cranberry sample surface was measured using a colorimeter. ), redness value (a ) and yellowness value (b Each group of samples was measured 10 times in parallel, and the total color difference ΔE was calculated according to formula (1).

[0047] (1)

[0048] Where: ΔE, total color difference value; L, a, b, color values ​​of unsweetened cranberry samples; , , The color values ​​are those of cranberry preserves after sugar infiltration treatment.

[0049] Table 4. Effect of L-cysteine ​​concentration on color difference of cranberry preserves

[0050] As shown in Table 4, the L in the 0.6%~1.0% treatment group The value was significantly higher than that of the 0.4% group ( P <0.05), indicating that a higher concentration of L-cysteine ​​can effectively prevent the formation of dark substances on the fruit surface due to oxidative browning. The value increased significantly with increasing concentration, while ΔE decreased significantly. In conclusion, L-cysteine ​​can significantly improve the color quality of cranberry preserves. Considering production costs and reducing additive usage, 0.8% by mass was determined to be the optimal dosage of L-cysteine.

[0051] (III) Single-factor experiment on the composition of complex sugars

[0052] Cranberry fruits were accurately weighed, and three sugar sources—sucrose, high-fructose corn syrup, and erythritol—were selected for compounding. The total mass fraction of the compound sugar solution was fixed at 55%, with sucrose:fructose corn syrup:erythritol ratios of 1:1:1, 2:1:1, 2:2:1, 3:2:1, and 3:1:1, respectively. The material-to-liquid ratio was 1:2 (g:mL). The sugar solution contained 0.6% calcium chloride, 0.8% L-cysteine, and 0.45% xanthan gum. The cranberry preserves were treated with sugar at 55℃ and a vacuum of -0.08 MPa for 7 h, followed by 12 h at room temperature. Sensory evaluation and color difference measurement were then performed on each group of cranberry preserves.

[0053] Table 5. Effects of the ratio of sucrose:fructose syrup:erythritol on the sensory scores of cranberry preserves.

[0054] The results showed that the morphological scores of the dried fruit varied significantly among different sugar solution groups. The total scores were lower and wrinkling was visible on the fruit surface when the sucrose:fructose syrup:erythritol ratios were 1:1:1, 2:1:1, and 2:2:1. This may be because the total solids content of the sugar solution was insufficient when the sucrose ratio was low. When the ratio was adjusted to 3:2:1, the morphological score reached a high level (26.96), demonstrating the best flavor harmony. The 3:2:1 group also had a higher color score (15.34). In conclusion, the sucrose:fructose syrup:erythritol ratio of 3:2:1 is the most suitable, resulting in a final product with a full shape, bright color, and good texture.

[0055] Table 6. Effect of the ratio of sucrose:fructose syrup:erythritol on the color difference of dried cranberries

[0056] Sucrose helps maintain the plump shape of the fruit, high-fructose corn syrup improves texture and color, and erythritol, as a sweetener, reduces the product's calorie value and improves the overly sweet taste of the dried fruit. A compound of sucrose, high-fructose corn syrup, and erythritol was selected, utilizing the differences in their physicochemical properties to produce a synergistic effect, resulting in high-quality, low-sugar cranberry dried fruit. Table 6 shows that the dried fruit prepared with a 3:2:1 compound sugar ratio has a lower L... value, a Both the sucrose:fructose syrup:erythritol ratio of 3:2:1 are ideal.

[0057] (iv) Single-factor test of filling material

[0058] Xanthan gum was selected as a filler. Xanthan gum was added at concentrations of 0.35%, 0.45%, 0.55%, 0.65%, and 0.75% (by mass) to a 55% compound sugar solution (sucrose:fructose syrup: erythritol = 3:2:1), with a material-to-liquid ratio of 1:2 (g:mL). The sugar solution contained 0.6% calcium chloride and 0.6% L-cysteine. The cranberry preserves were treated with sugar infiltration at 55℃ and a vacuum of -0.08 MPa for 7 h, followed by infiltration at room temperature for 12 h. Texture analysis was then performed on each group of cranberry preserves.

[0059] Table 7 Effect of xanthan gum concentration on the texture of cranberry preserves

[0060] Table 7 shows that as the xanthan gum concentration increases, the overall textural properties of cranberry preserves exhibit a trend of first increasing and then decreasing in hardness, chewiness, and elasticity. At a concentration of 0.55%, the highest hardness and chewiness are achieved, while elasticity remains at a high level. Considering all textural properties, 0.55% is determined to be the optimal amount of xanthan gum to be added.

[0061] (v) Response surface methodology for compound sugar infiltration solution formulation

[0062] Based on the results of the single-factor experiments, the total mass fraction of the compound sugar solution was fixed at 50%, the ratio of sucrose:fructose syrup:erythritol was 2:2:1, and the material-to-liquid ratio was 1:2 (g:mL). A Box-Behnken experimental design with three factors and three levels was conducted. The concentrations of L-cysteine ​​(A), calcium chloride (B), and xanthan gum (C) were selected as the three factors, with color difference and hardness as the response values. The sugar infiltration was carried out at a temperature of 55℃ and a vacuum of -0.08 MPa for 7 h, followed by sugar infiltration at room temperature for 12 h. The response surface methodology factor level table is shown in Table 8.

[0063] Table 8 Factor Level Table for Compound Sugar Infiltration Solution Formulation

[0064] Based on the experimental results in Table 9, the quadratic polynomial regression model equation for color difference is obtained: Y1 = 2.16 - 0.19A + 0.05B ​​- ​​0.15C + 0.0075AB - 0.15AC + 0.0025BC + 0.17A 2 -0.02B 2 +0.37C2 As shown in Table 10, the analysis of variance for the regression model yielded an F-value of 9.64. P A value of 0.0034 < 0.01 indicates that the model is highly significant and statistically significant. The F-value for the lack-of-fit term is 2.93. P =0.1633, not significant. This model can be used to analyze and predict the formulation of cranberry preserve compound syrup. The significance test of the regression equation coefficients of the model shows that A, C, AC, and A... 2 C 2 Significantly, the order of importance of factors affecting sugar penetration in cranberry preserves after experimental process optimization was: L-cysteine ​​concentration (A) > xanthan gum concentration (C) > calcium chloride concentration (B).

[0065] Table 9 Response Surface Experimental Design and Results

[0066] Based on the experimental results in Table 9, the quadratic polynomial regression model equation for hardness is obtained as follows: Y2 = 10.42 - 0.03A + 0.26B - 0.10C - 0.11AB + 0.23AC + 0.27BC - 0.66A 2 -0.14B 2 -0.35C 2 As shown in Table 11, the regression model variance analysis yielded an F-value of 32.03. P A value < 0.0001 indicates that the model is highly significant and statistically significant. The F-value for the lack-of-fit term is 1.10. P =0.4478, not significant. This model can be used to analyze and predict the formulation of cranberry preserve compound sugar infusion. The significance test of the regression equation coefficients for the hardness model shows that B, AC, BC, and A... 2 C 2 Highly significant, C, B 2 Significantly, the order of importance of factors affecting sugar penetration in cranberry preserves after experimental process optimization was: calcium chloride concentration (B) > xanthan gum concentration (C) > L-cysteine ​​(A).

[0067] Table 10. Regression ANOVA Table for Color Difference Model

[0068] Note: This indicates that the difference is highly significant ( P <0.01), Indicates a significant difference ( P <0.05); the same applies below.

[0069] Table 11. Analysis of Variance of Hardness Model Regression

[0070] Optimization analysis using the Design-Expert central composite method predicted the optimal formula for the compound sugar solution: L-cysteine ​​concentration of 0.829%, calcium chloride concentration of 0.800%, and xanthan gum concentration of 0.575%. The predicted color difference for cranberry preserves was 2.147, and the predicted firmness was 10.522 N. To verify the feasibility of these conditions, the optimal conditions were modified to: L-cysteine ​​concentration of 0.8%, calcium chloride concentration of 0.8%, and xanthan gum concentration of 0.6%. Three verification experiments were conducted under the above conditions, resulting in a cranberry preserve with a color difference of 2.02, a total sugar content of 46.29%, a firmness of 10.37 N, a sensory score of 83.75, a plump and translucent appearance, a suitable sweet and sour taste, and a moderate softness and firmness.

[0071] (vi) Single-factor experiments on vacuum sugar infiltration process

[0072] Using the above-treated cranberries as raw materials, under a fixed material-to-liquid ratio (1g:2mL), with L-cysteine ​​concentration of 0.8%, CaCl2 concentration of 0.6%, and xanthan gum concentration of 0.55%, the effects of sugar infiltration time, vacuum temperature, and compound sugar solution concentration on sugar infiltration of cranberry preserves were investigated, with the total sugar content, textural properties, and sensory scores of the cranberry preserves as evaluation indicators.

[0073] 1. Single-factor experiment on sugar infiltration time

[0074] With a fixed vacuum of -0.085 MPa, temperature of 55℃, and compound sugar solution concentration of 55%, the sugar infiltration time gradient was set at 3h, 4h, 5h, 6h, 7h, and 8h. Sugar infiltration was then carried out at room temperature for 12h, and the changes in fruit preserve quality at different time points were investigated. The texture and total sugar content of each group of cranberry preserves were determined.

[0075] Total sugar content determination: Referring to NY / T 2742-2015 "Determination of soluble sugars in fruits and fruit products - 3,5-Dinitrosalicylic acid colorimetric method", accurately weigh 5g of crushed cranberry preserve sample, place it in a beaker, add 80℃ hot distilled water, and extract in a water bath for 20min. Filter and collect the supernatant for later use. Hydrolyze the extract with 6mol / L HCl, then add 6mol / L NaOH solution until neutral, and measure the absorbance at 540nm wavelength. The standard curve, calculated as glucose, is y=0.057x+0.0035 (…). R 2 =0.9970).

[0076] Table 12 Effect of vacuum sugar infiltration time on the texture of cranberry preserves

[0077] Table 12 shows that the 6-hour sugar infusion treatment group exhibited the best texture characteristics. At 6 hours of infusion, the chewiness also reached its maximum (9.76 mJ), with high elasticity and cohesion. When the infusion time exceeded 6 hours, firmness and chewiness began to decrease, indicating that prolonged vacuum sugar infusion may lead to cell wall skeletal collapse and softening of the texture. In conclusion, the 6-hour sugar infusion time achieved the best balance between plumpness and chewy texture. Therefore, 6 hours was determined to be the optimal vacuum sugar infusion time.

[0078] Depend on Figure 1 It can be seen that with the extension of vacuum sugar infusion time, the total sugar content of cranberry preserves showed a trend of first increasing and then leveling off. When the vacuum sugar infusion time was 6 hours, the total sugar content of the preserves was 49.46%, which was not significantly different from the sugar infusion time treatment groups of 7 hours and 8 hours. P >0.05). In conclusion, 6 hours was determined to be the optimal vacuum sugar infiltration time.

[0079] 2. Single-factor experiment on sugar infiltration temperature

[0080] With a fixed vacuum degree of -0.085 MPa, a vacuum sugar infiltration time of 6 h followed by room temperature sugar infiltration for 12 h, and a compound sugar solution concentration of 55%, the sugar infiltration temperature gradient was set at 40℃, 45℃, 50℃, 55℃, and 60℃ to investigate the changes in the quality of the cranberry preserves under different temperatures. The texture and total sugar content of each group of cranberry preserves were determined.

[0081] Table 13 Effect of vacuum sugar infusion temperature on the texture of cranberry preserves

[0082] Table 13 shows that as the vacuum sugar infusion temperature increases, the firmness and chewiness of cranberry preserves initially increase and then decrease, while elasticity is less affected by temperature. When the sugar infusion temperature is between 40 and 50°C, the preserves have relatively low firmness. The firmness reaches its maximum of 9.42 N at 55°C. However, at a sugar infusion temperature of 60°C, the firmness begins to decrease, indicating that the fruit pulp tissue has begun to soften due to heat. Therefore, 55°C is determined to be the optimal vacuum sugar infusion temperature.

[0083] like Figure 2 As shown, when the sugar infusion temperature was 40℃, the total sugar content of the candied fruit was 46.38%; when the sugar infusion temperature was 55℃, the total sugar content significantly increased to 49.46%, which was significantly better than the 40, 45, and 50℃ groups. P <0.05), but the difference was not significant compared to 60℃. P >0.05). In conclusion, a sugar infiltration temperature of 55℃ is the optimal vacuum sugar infiltration temperature.

[0084] 3. Single-factor experiment on the concentration of compound sugar solution

[0085] With a fixed vacuum degree of -0.085 MPa, a vacuum sugar infiltration time of 6 h, a room temperature sugar infiltration time of 12 h, and a temperature of 55℃, the mass fraction gradient of the compound sugar solution was set at 40%, 45%, 50%, 55%, and 60%, and the changes in the quality of the cranberry preserves under different compound sugar solution concentrations were investigated. The texture and total sugar content of each group of cranberry preserves were determined.

[0086] Table 14 Effect of compound sugar concentration on the texture of vacuum-sugar-impregnated cranberry preserves

[0087] When the concentration of the compound sugar solution was 55%, the firmness of the dried fruit reached its maximum value of 9.42 N, which was significantly higher than that of the other groups. P At a concentration <0.05%, the chewiness also reached its peak (9.76 mJ), significantly improving the firmness and chewiness of the fruit. When the concentration was further increased to 60%, the firmness, chewiness, and elasticity decreased. In conclusion, a sugar solution concentration of 55% had the most significant effect on the firmness and chewiness of the dried fruit, and was considered the optimal sugar solution concentration.

[0088] like Figure 3 As shown, when the concentration of the compound sugar solution was 55%, the total sugar content of the candied fruit reached 49.46%; when the sugar solution concentration was increased to 60%, the total sugar content was not significantly different from that of the 55% experimental group. P >0.05), overall, a 55% compound sugar solution concentration can achieve a good sugar penetration effect.

[0089] (vii) Response surface optimization experimental design

[0090] Based on the results of the single-factor experiments, the optimal range of values ​​for each parameter was determined. Following the Box-Behnken Design, three factors were selected as independent variables: compound sugar solution concentration (A), vacuum sugar infiltration time (B), and vacuum temperature (C), with sensory scores as the response values. The experimental factors and level coding design are shown in Table 15.

[0091] Table 15 Factor Level Table for Vacuum Sugar Infiltration Test

[0092] Table 16 Response Surface Experimental Design and Results

[0093] Based on the results of the fitting experiment using multiple regression analysis, a quadratic regression equation with sensory score (Y) as the objective function was obtained: Y = 83.20 + 0.34 A+0.91 B+0.85 C+1.40 AB-1.18 AC+0.43 BC+0.80 A 2 -4.770 B 2 -4.57 C 2 Analysis of variance and significance test of the regression model show that the F-value is 26.17. P A value < 0.0001 indicates that the model is highly significant and statistically significant. The F-value for lack of fit is 1.18. P =0.4231, not significant. This model can be used to analyze and predict parameters of vacuum-infused cranberry preserves. Experiments on the significance of the regression equation coefficients of the model show that B, C, and B... 2 C 2 The results of experiments AB and AC were significant. After optimizing the experimental process, the order of importance of the factors affecting the quality of vacuum-infused cranberry preserves was: vacuum time (B) > infusion temperature (C) > sugar concentration (A).

[0094] Table 17. Regression ANOVA Table for Sensory Rating Model

[0095] Based on the regression model equation and using sensory evaluation as an indicator, response surface methodology predicted the optimal vacuum sugar infusion process parameters as follows: compound sugar solution concentration 56.622%, vacuum sugar infusion time 6.731 h, and sugar infusion temperature 55.588℃. Under these conditions, the predicted sensory score of the prepared cranberry preserves was 83.49 points. For ease of operation, the optimal conditions were modified to: compound sugar solution concentration 55%, vacuum sugar infusion time 6 h, and sugar infusion temperature 55℃. Three verification experiments were conducted under the above experimental conditions, and the resulting cranberry preserves had a sensory score of 84.11 points, a total sugar content of 49.46%, and exhibited a plump appearance and a balanced sweet and sour taste.

[0096] (viii) The effect of vacuum degree on the optimal conditions for vacuum sugar infiltration

[0097] Based on response surface methodology optimization, a vacuum temperature of 55℃, a compound sugar solution concentration of 55%, and a vacuum time of 6 hours were selected. Vacuum gradients of -0.055, -0.065, -0.075, -0.085, and -0.095 MPa were set to investigate the effects of different vacuum degrees on the sensory scores and total sugar content of cranberry preserves.

[0098] When the vacuum level was -0.085 MPa, the total sensory score of the dried fruit was 84.11 points, significantly higher than that of other vacuum level experimental groups. P<0.05), when the vacuum degree was -0.095 MPa, the total score dropped to 80.20 points, indicating that excessively high vacuum degrees may have a negative impact on fruit structure. The total sugar content reached 49.46% at -0.085 MPa, which was not significantly different from the -0.095 MPa group. P >0.05), but significantly higher than other groups ( P <0.05). The sensory score of the dried cranberries was lowest at a vacuum level of -0.055 MPa, mainly due to insufficient sugar penetration, resulting in a low total sugar content, severe collapse of the shape after drying, and a sour taste. In conclusion, a vacuum level of -0.085 MPa can maximize the improvement of the sensory quality and total sugar content of cranberry dried cranberries.

[0099] Table 18 Effects of vacuum degree on sensory scores and total sugar content of vacuum-infused cranberry preserves

[0100] Experimental Example 2

[0101] Based on the preparation process described in Example 1, different sugar infiltration methods were set up to explore the effects of different sugar infiltration methods on the sensory quality and index components of cranberry preserves.

[0102] Atmospheric pressure sugar infiltration group: Same as in Example 1, except that "sugar infiltration treatment at 55℃ and vacuum degree -0.085MPa for 6 hours, followed by sugar infiltration at room temperature for 12 hours" was replaced with "sugar infiltration treatment at 55℃ constant temperature water bath for 6 hours, followed by sugar infiltration at room temperature for 12 hours".

[0103] Ultrasonic sugar infiltration group: Same as in Example 1, except that "sugar infiltration treatment at 55℃ and vacuum degree -0.085MPa for 6 hours, followed by sugar infiltration at room temperature for 12 hours" was replaced with "sugar infiltration treatment at 55℃ and ultrasonic power of 300W for 6 hours, followed by sugar infiltration at room temperature for 12 hours".

[0104] Microwave sugar infiltration group: Same as in Example 1, except that "sugar infiltration treatment at 55°C and vacuum degree -0.085MPa for 6 hours, followed by sugar infiltration at room temperature for 12 hours" was replaced with "sugar infiltration treatment at microwave power of 140W for 1 hour at intervals, followed by sugar infiltration at room temperature for 17 hours".

[0105] (a) Sensory quality evaluation of cranberry preserves

[0106] A sensory evaluation team of 20 people (10 men and 10 women) who had received sensory evaluation training was selected to evaluate the cranberry preserves prepared in Example 1 and the preparation processes of the above groups based on the sensory evaluation criteria (as shown in Table 1). The final result was the average value.

[0107] Table 19 Effect of Sugar Infusion Method on Sensory Scores of Cranberry Preserves

[0108] Note: Different letters in the same column of data indicate significant differences. P <0.05).

[0109] Table 19 shows that the total sensory scores for the four sugar infusion methods, from highest to lowest, are: vacuum sugar infusion (84.90 points) > atmospheric pressure sugar infusion (79.40 points) > ultrasonic sugar infusion (75.60 points) > microwave sugar infusion (74.50 points). In terms of texture and aroma, vacuum sugar infusion is significantly superior to the fruit preserves produced by other sugar infusion methods. P <0.05%, the other three types of sugar-infused candied fruit had poor texture fullness, insufficient fruity aroma and firmness; in terms of taste, vacuum sugar infusion treatment scored the highest, with a balanced sweet and sour taste and a moderately soft and firm texture, and there was no significant difference between normal pressure treatment and ultrasonic treatment. P >0.05), microwave sugar infiltration scored the lowest; in terms of color, there was no significant difference between vacuum sugar infiltration and atmospheric pressure sugar infiltration. P Vacuum sugar infusion (>0.05) effectively preserves the original color of the fruit, while dried cranberries produced by microwave and ultrasonic sugar infusion have a dull color. Therefore, from a sensory perspective, vacuum sugar infusion is the best method for improving the sensory quality of dried cranberries.

[0110] (II) Effects of different sugar infusion methods on total sugar and reducing sugar in cranberry preserves

[0111] The total sugar and reducing sugar of cranberry preserves prepared by Example 1 and the above-mentioned preparation processes were determined. For the determination method, please refer to the single-factor experiment section of Experiment 1 (VI) Vacuum Sugar Infiltration Process.

[0112] from Figure 4 It was found that there were significant differences in the total sugar content of cranberry preserves among the four treatments: vacuum sugar infiltration (49.46%) > microwave sugar infiltration (43.57%) > ultrasonic sugar infiltration (41.27%) > atmospheric pressure sugar infiltration (39.47%). The total sugar content of atmospheric pressure sugar infiltration was significantly lower than that of the other treatments. P <0.05%, vacuum, microwave, and ultrasound methods disrupted tissue, creating microscopic channels and thus enhancing mass transfer. The reducing sugar content of the vacuum and microwave sugar infiltration methods was significantly higher than that of the ultrasound and atmospheric pressure groups ( P The concentration of total sugar content was <0.05%, which is consistent with the trend of total sugar content. In summary, vacuum sugar infiltration not only improves mass transfer efficiency but also helps maintain the storage quality of cranberry preserves.

[0113] (III) Effects of different sugar infiltration methods on the rehydration rate of low-sugar cranberry preserves

[0114] Accurately weigh 5g of cranberry preserves prepared by Example 1 and the above preparation processes, place them in a beaker, add 100mL of distilled water, and rehydrate them at room temperature. Take a sample every 30min, absorb the surface moisture of the sample with filter paper, weigh it, and calculate according to formula (2).

[0115] (2)

[0116] Where: W, rehydration rate, %; m f , the mass after rehydration, g; m, the mass before rehydration, g.

[0117] Rehydration rate indicates the ability of dried fruits and vegetables to reabsorb water and regain their original freshness, reflecting the storage stability of preserved fruits. Figure 5 It can be seen that, starting from 30 minutes, the rehydration rate of the microwave permeation treatment was significantly higher than that of the other three groups. P With a concentration <0.05%, the rehydration rate of the dried fruit treated with vacuum sugar infusion remained at the lowest level (109.82%) until the rehydration time reached 210 min, which was 38.95% lower than that of the microwave sugar infusion treatment. Vacuum sugar infusion effectively removes air from the interstitial spaces and accelerates the penetration of the complex sugar solution, forming a compact structure and effectively reducing the space for water penetration. A high rehydration rate will affect product stability, making it prone to moisture absorption and re-moistening, thus accelerating product deterioration. Therefore, the vacuum sugar infusion method is more conducive to improving the storage resistance of dried fruit.

[0118] (iv) Effects of different sugar infusion methods on the texture of low-sugar cranberry preserves

[0119] The texture of the cranberry preserves prepared by Example 1 and the above-mentioned preparation processes was determined.

[0120] Table 20 Effects of sugar infusion method on the texture of cranberry preserves

[0121] Different sugar infusion methods affect the final textural quality of cranberry preserves. Table 20 shows that the firmness (9.98 N), elasticity (2.69 mJ), and chewiness (10.14 mJ) of the vacuum-infused cranberry preserves are significantly higher than those treated with the other three sugar infusion methods. P <0.05%, which directly improves the texture of the dried fruit. In comparison, the ultrasonic treatment group and the normal pressure treatment group had the lowest hardness and chewiness, and the dried fruit tissue structure was loose. In terms of adhesiveness, there was no significant difference between the vacuum sugar infiltration group and the microwave sugar infiltration group. P >0.05), but all were significantly higher than those in the normal pressure group ( P <0.05). In conclusion, vacuum sugar infiltration can preserve the texture and quality of cranberry preserves to the greatest extent, making it more suitable for cranberry preserve processing.

[0122] (V) Effects of different sugar infusion methods on the main functional components of low-sugar cranberry preserves

[0123] The main functional components of the cranberry preserves prepared by Example 1 and the above-mentioned preparation processes were determined. Among them, the vitamin C content was determined by the 2,6-dichlorophenolindophenol back titration method. 5.0 g of sample was weighed, soaked and ground in 2% oxalic acid solution, and then filtered after being diluted to 50 mL. The content was calculated according to formula (3).

[0124] (3)

[0125] In the formula: V1, volume of sample solution consumed, mL; T, titer of 2,6-dichlorophenolindophenol, mg / mL; V2, total volume of sample solution, mL; W, sample weight, g.

[0126] Determination of total phenols, flavonoids and anthocyanins. Take 5.00 g of cranberry preserve sample, crush it, add 20 mL of 70% ethanol solution, extract by ultrasonication at 300 W for 30 min, centrifuge at 4000 r / min for 20 min, repeat twice, combine the supernatants and make up to 50 mL to obtain cranberry preserve extract solution, store at 4℃ in the dark for later use.

[0127] The total phenol content was determined using the Folin-Ciocalteu colorimetric method. 1 mL of diluted cranberry preserve extract was added to 1 mL of Folin-Ciocalteu and 3 mL of 20% Na₂CO₃ solution. The mixture was incubated in a 50℃ water bath for 30 min. After shaking, the absorbance was measured at 765 nm. Gallic acid was used as the standard, and the standard curve was calculated as y = 1.7394x + 0.0025 (R²). 2 =0.9985).

[0128] For the determination of flavonoid content, take 1 mL of fruit extract, add 1 mL of 5% NaNO2 solution, mix well, let stand for 5 min, add 1 mL of 10% Al(NO3)3 solution, let stand for 5 min, add 3 mL of 4% NaOH solution, dilute to volume with 70% ethanol solution, let stand for another 15 min, and measure the absorbance at 510 nm. Using rutin as the standard, the standard curve is y = 0.4224x + 0.0016 (…). R 2 =0.9993).

[0129] The anthocyanin content was determined by pH difference method. The absorbance of the sample solution was measured at 510 nm and 700 nm using a UV-Vis spectrophotometer and calculated according to formula (4).

[0130] (4)

[0131] In the formula: M, anthocyanin content, mg / g; A, absorbance. V, total volume of extract, mL; n, dilution factor; Mt, relative molecular mass of cyanidin-3-glucoside, 449.2; ε, extinction coefficient of cyanidin-3-glucoside, 29600; b, colorimetric path length, cm; m, sample mass, g.

[0132] Table 21 Effects of sugar infusion method on the main functional components of cranberry preserves

[0133] Note: Different letters in the same row indicate significant differences. P <0.05).

[0134] Table 21 shows that the cranberry preserves prepared by atmospheric pressure saccharification had the highest vitamin C content (3.72 mg / 100g), followed by vacuum saccharification and ultrasonic saccharification, while microwave saccharification had the lowest vitamin C content (1.67 mg / 100g). The total phenolic, flavonoid, and anthocyanin contents of vacuum saccharification were significantly higher than those of the other three saccharification methods. P Microwave sizing results in the greatest loss of key functional components, with a concentration <0.05%. Therefore, vacuum sizing is more effective in preserving the functional components of cranberry preserves.

[0135] (vi) Effects of different sugar infiltration methods on color difference of low-sugar cranberry preserves

[0136] The color difference of the cranberry preserves prepared by Example 1 and the above-mentioned preparation processes was measured.

[0137] Table 22 Effect of Sugar Infusion Method on Color Difference of Cranberry Dried Fruit

[0138] L The value reflects the brightness of the cranberry skin. The higher the value, the closer it is to the original fruit color. The value has little impact. As shown in Table 22, the L value of cranberry preserves produced using vacuum and atmospheric pressure sugar infiltration is... The value was significantly higher than that of ultrasound and microwave glycolysis ( P <0.05), and the total color difference ΔE value is significantly at the lowest level ( P <0.05). Microwave sugar infiltration method a The lower temperature and higher ΔE value indicate the most severe browning. This is because microwave sugar infusion, with its higher temperature, causes greater loss of fruit skin color; ultrasonic treatment excessively damages the cellular structure of the dried fruit; while the low-oxygen environment of vacuum sugar infusion effectively inhibits browning and better preserves the color of the cranberry skin. In conclusion, vacuum and atmospheric pressure sugar infusion processes have significant advantages in preserving the color of dried fruit.

[0139] (vii) Effects of different sugar infusion methods on the aroma of low-sugar cranberry preserves

[0140] The aroma of the cranberry preserves prepared by Example 1 and the above-described preparation processes was measured.

[0141] Cranberry preserve samples from each group were chopped, placed in sample vials, sealed, and subjected to headspace extraction. Desorption was performed at 250℃ for 5 min using a gas chromatography-mass spectrometry (GC-MS) instrument. The chromatographic column was an Agilent DB-225 (30m × 0.25mm × 0.25μm); the carrier flow rate was 1.0 mL / min; the column temperature was 40℃ for 1 min, increased to 160℃ at 3℃ / min, and then increased to 270℃ at 3℃ / min. The scan range was full scan. Compounds with a matching degree greater than 80% in the samples were qualitatively analyzed by searching the NIST mass spectrometry library, and the relative content of each aroma component was calculated using the peak area normalization method.

[0142] The results are as follows Figure 6 As shown, under the same testing conditions, the aroma components detected in cranberry preserves samples prepared using four different sugar infiltration methods differed. A total of 84 aroma components were detected in the vacuum sugar infiltration samples, mainly including 16 alcohols, 17 aldehydes, 13 esters, 12 acids, and 9 ketones. The proportions of aldehydes (21.67%), esters (17.35%), ketones (13.75%), alcohols (16.46%), and acids (17.69%) were well-balanced, exhibiting a good overall layered aroma. Nonanal (4.11%), decanal (3.66%), and (E)-2-heptenal (3.19%) were relatively high and had low odor thresholds. Nonanal and decanal mainly presented fresh fruit and citrus aromas, while (E)-2-heptenal was predominantly green leafy and is considered an important contributor to the fruit aroma formation in fruit and vegetable products. In addition, ethyl benzoate (4.11%) contributes to the sweet fruit and floral aromas characteristic of the cranberry preserve, while α-terpineol (6.37%) exhibits distinct pine and lilac aromas, both enhancing the fruity aroma profile of the product. Furthermore, these results indicate that a vacuum environment effectively inhibits the oxidative rancidity of fatty acids and the thermal hydrolysis of esters, resulting in better preservation of esters. The proportions of key aroma components in the vacuum-infused sugar samples are relatively harmonious, giving the cranberry preserve a fresh, natural, and distinct overall aroma profile.

[0143] A total of 72 aroma components were detected in the samples obtained by atmospheric pressure sugar infiltration, mainly including 19 aldehydes, 14 esters, 10 acids, 12 alcohols, and 9 ketones. Aldehydes (23.96%), acids (21.50%), and esters (20.46%) accounted for a relatively high proportion. The most prominent component was saturated fatty acid palmitic acid (11.82%), which has a slight waxy and oily aroma; its relatively high content can enhance the oily and heavy feel of the sample. Methyl (E)-9-octadecenoate (7.02%) imparts a slight oily aroma to the candied fruit; a higher content usually indicates enhancement from heat treatment. 1-(2-furanyl)-2-hydroxyethyl ketone (5.92%) has a relatively low odor threshold and exhibits obvious caramel and roasted aroma characteristics, making it an important contributor to the heat-processed flavor. Therefore, the fresh fruit aroma of candied fruit obtained by atmospheric pressure sugar infiltration is weakened, and the overall aroma tends to be more like that of heat-processed roasted flavors.

[0144] A total of 77 aroma components were detected in the ultrasonically infiltrated sugar samples, mainly including 19 aldehydes, 13 alcohols, 13 acids, and 11 esters. The dominant aroma component in the ultrasonically infiltrated samples was alcohol (39.61%), while esters and aldehydes were relatively low. The relative content of α-terpineol (30.01%) was significantly increased, becoming the most representative key aroma component in the ultrasonically infiltrated sugar samples. Its strong floral and pine aroma masked the contribution of fruity substances to some extent, making the overall aroma floral with a slightly lactic acid-like sourness and a slightly weaker fresh fruity aroma.

[0145] The microwave-treated sugar sample contained the most diverse range of components (93 types), mainly including 13 alcohols, 18 acids, 18 esters, 10 alkanes, 17 aldehydes, and 7 ketones. Significant accumulation of acids (43.09%) was observed in the sample, particularly benzoic acid (17.79%) and various fatty acids, which became the dominant aroma components. These were key aroma components contributing to the prominent sour taste and flavor deterioration of microwave-treated candied fruit, damaging heat-sensitive aromas such as esters and alcohols, and significantly reducing fruity aroma compounds such as terpenes.

[0146] (viii) Effects of different sugar infiltration methods on the cell structure of low-sugar cranberry tissue

[0147] After sugar infiltration, the samples were pre-frozen at -80 °C for 16 h and then freeze-dried under vacuum for 72 h. The samples were then subjected to brittle fracture treatment in liquid nitrogen, and the flat cut surfaces were fixed and sprayed with gold. The microstructure of the candied fruit was observed and photographed at 300x magnification using a scanning electron microscope.

[0148] Depend on Figure 7 It can be seen that the cranberry fruit blank ( Figure 7 In the sample E), intact thin-walled cells were observed. The cells were oval-shaped, tightly arranged, with clear cell wall outlines and smooth surfaces, and small intercellular spaces. However, after sugar infiltration treatment, the propolis cells underwent varying degrees of change. Vacuum sugar infiltration sample ( Figure 7 Sample A) exhibits intact cell microstructure, orderly arrangement, significantly increased intercellular spaces, and good connectivity, indicating that vacuum effectively promotes the infiltration of glucose solution into the tissue and maintains cell shape. Normal pressure glucose infiltration samples ( Figure 7 Sample C retained a basic cell arrangement similar to that of fresh fruit, but showed significant water loss and shrinkage, with some collapse. The uniformity of the pulp cells was slightly lower than that of the vacuum-infused sample. This is because atmospheric pressure infusion relies solely on mass transfer due to concentration gradient, causing the cell walls to curl due to the loss of internal turgor pressure support. Ultrasonic infusion sample ( Figure 7 In sample B), localized mechanical damage occurred, resulting in microchannels caused by ultrasonic cavitation. Cell wall rupture and unevenly distributed pores are visible in the image. Microwave-infiltrated sugar sample ( Figure 7 In tissue D), the heat damage is the most severe, the cells are loosely arranged, the cell walls are severely contracted and adhered, and the reticular structure disappears. Although this porous and loose structure gives it high rehydration properties, it also leads to a decrease in its sensory quality.

[0149] In summary, the technical solution described in this invention can effectively solve problems such as slow sugar penetration, low product fullness, severe browning, and loss of heat-sensitive nutrients, resulting in cranberry low-sugar preserves with better flavor and quality.

[0150] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A composite sugar-infiltrating solution, characterized in that, It includes a complex sugar solution with a mass concentration ratio of (50-60):(0.2-1.0):(0.2-1.0):(0.35-0.75), L-cysteine, calcium chloride, and xanthan gum; The compound sugar solution is composed of sucrose, fructose syrup and erythritol in a mass ratio of (1~4):(1~3):

1.

2. A preparation process for improving the flavor quality of low-sugar cranberry preserves, characterized in that, Includes the following steps: (1) Thaw the cranberry raw material and blanch it to obtain intermediate product 1; (2) The intermediate product 1 is placed in the composite sugar-permeating solution of claim 1 for vacuum sugar permeation treatment, and then dried to obtain the product.

3. The preparation process according to claim 2, characterized in that, The temperature of the blanching in step (1) is 80~88℃, and the blanching time is 80~100s.

4. The preparation process according to claim 3, characterized in that, The mass-to-volume ratio of the cranberry fruit raw material to the compound sugar solution is 1g:(1~5)mL.

5. The preparation process according to claim 2, characterized in that, The vacuum sugar infiltration treatment in step (2) is as follows: sugar infiltration treatment at 52~58℃ under vacuum for 4~7h, and then sugar infiltration treatment at 25±1℃ for 10~14h.

6. The preparation process according to claim 5, characterized in that, The vacuum level of the vacuum condition is -(0.08~0.09) MPa.

7. The preparation process according to claim 2, characterized in that, The drying temperature in step (2) is 55~65℃, and the cranberries are dried until the moisture content of the low-sugar cranberries is 20~25%.

8. Cranberry low-sugar preserves prepared by the process described in any one of claims 2-7.

9. The cranberry low-sugar dried fruit according to claim 8, characterized in that, The total sugar content of the cranberry low-sugar preserves is <55% based on glucose content.

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