A freeze-dried product of a richly flavored flat peach pulp and a method for preparing the same

Abstract

The application provides a kind of flavour rich flat peach pulp freeze-dried product and its preparation method, and belongs to the technical field of food aroma retention.The preparation method of a kind of flavour rich flat peach pulp freeze-dried product provided by the application comprises the following steps: (1) after flat peach is pitted, peeled and cut, carry out browning prevention treatment, then beat pulp, obtain flat peach pulp;(2) the flat peach pulp is subjected to enzymolysis, and the enzymolysis flat peach pulp is obtained;(3) after sugar is added in the enzymolysis flat peach pulp, vacuum freeze-drying treatment is carried out, and flat peach pulp freeze-dried product is obtained.The application uses the method of adding sugar on the basis of enzymolysis, changes the distribution coefficient of volatile components in the system by the action of hydrogen bond or other interaction force, affects the volatile speed and release intensity of aroma, thereby increases the aroma level and complexity of product, so that the product has the aroma of natural fruit, effectively maintains and improves the aroma quality of fruit product, and achieves obvious aroma enhancement effect.

Description

Technical Field

[0001] This invention relates to the field of food aroma preservation technology, and in particular to a freeze-dried product of peach pulp with rich flavor and its preparation method. Background Technology

[0002] Fresh peaches are perishable during storage and transportation, with a short shelf life. Therefore, deep processing is essential to extend the fruit's supply cycle and meet consumer and market demands. Vacuum freeze-drying technology, which better preserves the color, structure, and nutrients of fruits and vegetables, is significantly superior to other drying methods, making it the optimal drying method for high-quality dried fruit and vegetable products. However, during vacuum freeze-drying, some aroma components are lost due to the prolonged vacuum process. Currently, research on techniques for enhancing the aroma and quality of freeze-dried fruit pulp after reconstitution is still insufficient. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing a freeze-dried peach pulp product with rich flavor, which changes the distribution coefficient of volatile components in the system, thereby increasing the aroma level and complexity of the product, making the product have the aroma of natural fruit, effectively maintaining and improving the aroma quality of fruit products, and achieving a significant aroma enhancement effect.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] This invention provides a method for preparing a freeze-dried product of peach pulp with rich flavor, comprising the following steps:

[0006] (1) After removing the pits, peeling, and cutting the peaches into pieces, they are treated to prevent browning, and then pulped to obtain peach pulp;

[0007] (2) The peach pulp is subjected to enzymatic hydrolysis to obtain enzymatically hydrolyzed peach pulp;

[0008] (3) After adding sugar to the enzymatically hydrolyzed peach pulp, vacuum freeze-drying is performed to obtain the freeze-dried peach pulp product.

[0009] Preferably, the anti-browning treatment in step (1) involves soaking the chopped peaches in an aqueous solution containing 0.5-0.7% citric acid and 0.01-0.03% L-ascorbic acid for 25-35 minutes.

[0010] Preferably, during the pulping process in step (1), 0.08–0.12% of D-isoascorbic acid by weight of the peaches is added for color protection.

[0011] Preferably, the enzymes used for enzymatic hydrolysis in step (2) are pectinase and β-glucosidase; the mass ratio of pectinase to β-glucosidase is 1:2 to 3; the total enzyme activity of pectinase and β-glucosidase is 25 to 35 U / g; the enzymatic hydrolysis temperature is 50 to 55°C, and the time is 2.5 to 3 hours.

[0012] Preferably, the sugar in step (3) is one of sucrose, fructose, glucose, aspartame, and steviol glycosides.

[0013] Preferably, in step (3), the amount of sucrose, fructose and glucose added is 8-12 wt%, the amount of aspartame added is 0.05-0.1 wt%, and the amount of steviol glycoside added is 0.025-0.1 wt%.

[0014] Preferably, the vacuum freeze-drying process involves first quick-freezing in liquid nitrogen for 15–20 min, then freezing at -80–-85°C for 1.5–2 h, and finally freezing under vacuum at 0.1–0.3 mbar and -50–-60°C for 40–48 h.

[0015] The present invention also provides a freeze-dried product of peach pulp with rich flavor obtained by the preparation method described above.

[0016] The present invention also provides the use of sugar in enhancing the aroma of the freeze-dried peach syrup product.

[0017] Preferably, the sugar is steviol glycoside, and the amount of steviol glycoside added is 0.025-0.1 wt%.

[0018] This invention investigated the effects of the ratio of compound enzymes, the amount of compound enzymes added, the enzymatic hydrolysis time, and the enzymatic hydrolysis temperature on the aroma quality of peach pulp. Through single-factor experiments and orthogonal experiments, the enzymatic hydrolysis process was optimized. The optimal process was determined to be a 1:3 ratio of pectinase to β-glucosidase compound enzymes, an enzyme addition amount of 30 U / g, a hydrolysis temperature of 50℃, and a hydrolysis time of 2.5 h. Verification showed that this enzymatic hydrolysis process can improve the aroma quality of peach pulp.

[0019] This invention also investigated the effect of adding sugar on improving the aroma quality of vacuum freeze-dried peach pulp based on enzymatic hydrolysis. In this invention, sugar, through hydrogen bonding or other interactions, alters the partition coefficient of volatile components within the system, affecting the evaporation rate and release intensity of aroma, thereby increasing the aroma layers and complexity of the product. This results in a product with the aroma of natural fruit, effectively maintaining and improving the aroma quality of fruit products, achieving a significant aroma-enhancing effect. Experiments revealed that steviol glycosides are the most effective sugar for improving the flavor quality of enzymatically hydrolyzed peach pulp. Furthermore, after vacuum freeze-drying, the sample of enzymatically hydrolyzed peach pulp with added steviol glycosides exhibited better flavor and higher quality compared to both raw peach pulp and enzymatically hydrolyzed peach pulp. Attached Figure Description

[0020] Figure 1 Descriptive sensory evaluation diagrams of raw peach pulp, enzymatically hydrolyzed peach pulp, and enzymatically hydrolyzed peach pulp with added sugars.

[0021] Figure 2 Comparison of electronic noses for raw peach pulp, enzymatically hydrolyzed peach pulp, and enzymatically hydrolyzed peach pulp with different types of added sugars.

[0022] Figure 3 Sensory evaluation diagrams of enzymatically hydrolyzed peach pulp with different concentrations of steviol glycosides.

[0023] Figure 4 Descriptive sensory evaluation diagrams of VFD products of peach pulp, enzymatically hydrolyzed peach pulp, and enzymatically hydrolyzed peach pulp impregnated with steviol glycosides.

[0024] Figure 5 A comparison of electronic noses for VFD products of raw peach pulp, enzymatically hydrolyzed peach pulp, and enzymatically hydrolyzed peach pulp impregnated with steviol glycosides. Detailed Implementation

[0025] 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.

[0026] Example 1

[0027] (1) Preparation of peach syrup:

[0028] Twenty fresh flat peaches, all firm, uniform in size, and at a consistent ripeness, free from mechanical damage and pests, were removed from the cold storage. The peels and pits were quickly removed, and the peaches were cut into small pieces. Immediately after cutting, the pieces were soaked in an aqueous solution containing 0.6% citric acid and 0.02% L-ascorbic acid to prevent browning. After soaking for 30 minutes, the pieces were removed and placed in a pulping machine. 0.1% of the peach's weight of sodium D-isoascorbate was added, and the pulping was performed for 30 seconds to preserve color and obtain the raw peach pulp for later use.

[0029] (2) Preparation of enzymatically hydrolyzed peach pulp and optimization of enzymatic hydrolysis conditions

[0030] Enzymes are added to the original peach pulp for enzymatic hydrolysis, and then enzymatically hydrolyzed peach pulp is obtained;

[0031] The basic conditions for enzymatic hydrolysis were established as follows: enzyme ratio 1:2, enzyme dosage 20 U / g, hydrolysis temperature 45℃, and hydrolysis time 2 hours. Three of these conditions were kept constant, while the third condition was changed. The effects of these four factors were studied to determine the optimal factor levels. Specifically:

[0032] The enzymes are pectinase and β-glucosidase, with enzyme ratios of 1:1, 1:2, 1:3, 2:1, and 3:1; enzyme dosages of 5 U / g, 10 U / g, 20 U / g, 30 U / g, and 40 U / g; enzymatic hydrolysis temperatures of 35℃, 40℃, 45℃, 50℃, and 55℃; and enzymatic hydrolysis times of 1 h, 1.5 h, 2.0 h, 2.5 h, and 3 h.

[0033] Based on the results of the single-factor experiments, the optimal conditions for four factors were selected: the ratio of compound enzymes (pectinase: β-glucosidase), the amount of compound enzyme added, the enzymatic hydrolysis temperature and the enzymatic hydrolysis time. An orthogonal experiment was conducted using an L9(34) orthogonal experimental table, as shown in Tables 1 and 2 below. The optimal enzymatic hydrolysis conditions were determined through sensory evaluation.

[0034] Sensory evaluation used a 10-point scale, with 0-9 points indicating a gradually increasing aroma. Specifically, 0-3 points indicate no aroma intensity, 4-6 points indicate a medium aroma intensity, and 7-9 points indicate an extremely strong aroma intensity. Evaluators described the aroma properties of the enzymatically hydrolyzed peach pulp, and ultimately determined sweetness, peach aroma, floral aroma, fruity aroma, acidity, and grassy aroma as the evaluation indicators for the aroma properties of the peach pulp.

[0035] Each sample was assigned a three-digit random code, and then 12 evaluators were invited to conduct sensory evaluations at room temperature, with 10-minute intervals between evaluations. The average value of each aroma attribute was then used as the evaluation result.

[0036] Table 1. Factors and levels of orthogonal experiment

[0037]

[0038] Table 2 Orthogonal Experiment Analysis

[0039]

[0040]

[0041] As shown in Table 2, the optimal enzymatic hydrolysis process optimized by the orthogonal method is a pectinase to β-glucosidase complex enzyme ratio of 1:3, a complex enzyme addition amount of 30 U / g, an enzymatic hydrolysis temperature of 50℃, and an enzymatic hydrolysis time of 2.5 h.

[0042] Example 2

[0043] Under the optimal enzymatic hydrolysis conditions obtained in Example 1, peach pulp was enzymatically hydrolyzed. Sucrose, fructose, glucose, aspartame, and steviol glycosides were added to the enzymatically hydrolyzed peach pulp, respectively. The aroma quality of the enzymatically hydrolyzed peach pulp with added sugar was comprehensively evaluated to determine the best sugar type to improve the flavor quality of the enzymatically hydrolyzed peach pulp.

[0044] Experiment 1

[0045] 10 wt% sucrose was added to the enzymatically hydrolyzed peach pulp, and its aroma quality was comprehensively evaluated by gas chromatography-mass spectrometry (GC-MS), sensory evaluation, and electronic nose.

[0046] Experiment 2

[0047] Fructose (10 wt%) was added to the enzymatically hydrolyzed peach pulp, and its aroma quality was comprehensively evaluated by GC-MS, sensory evaluation, and electronic nose.

[0048] Experiment 3

[0049] 10 wt% of glucose was added to the enzymatically hydrolyzed peach pulp, and its aroma quality was comprehensively evaluated by GC-MS, sensory evaluation, and electronic nose.

[0050] Experiment 4

[0051] Aspartame (approximately 200 times sweeter than sucrose) was added to enzymatically hydrolyzed peach pulp at a concentration of 0.05 wt%, and its aroma quality was comprehensively evaluated by GC-MS, sensory evaluation, and electronic nose.

[0052] Experiment 5

[0053] (1) 0.05 wt% of steviol glycosides (the sweetness of the sugar substitute is about 200 times that of sucrose) were added to the enzymatically hydrolyzed peach pulp, and its aroma quality was comprehensively evaluated by GC-MS, sensory evaluation and electronic nose.

[0054] (2) 0.025 wt% of stevioside was added to the enzymatically hydrolyzed peach pulp, and its aroma quality was comprehensively evaluated by GC-MS sensory evaluation.

[0055] (3) Add 0.075 wt% of stevioside to the enzymatically hydrolyzed peach pulp and evaluate its aroma quality by GC-MS sensory evaluation.

[0056] (4) Add 0.1 wt% of stevioside to the enzymatically hydrolyzed peach pulp and evaluate its aroma quality by GC-MS sensory evaluation.

[0057] (5) Enzymatically hydrolyzed peach pulp (4) with 0.1% steviol glycosides was subjected to vacuum freeze-drying. The sample was placed in liquid nitrogen for 20 min for quick freezing, then transferred to a -80℃ freezer for 2 h for deep freezing, and finally subjected to vacuum freeze-drying (0.2 mbar, -60℃) for 48 h. The aroma quality of the product after vacuum freeze-drying was comprehensively evaluated by measuring the vacuum freeze-drying index.

[0058] The aroma mainly consists of volatile flavor compounds. SPME extraction was used to adsorb aroma compounds from enzymatically hydrolyzed peach pulp with added sugars. After adsorption saturation, GC-MS was used for resolution and analysis. The results are shown in Table 3 below. Sensory evaluation results are as follows: Figure 1 As shown; the electronic nose analysis results are as follows Figure 2 As shown, during the test, the instrument needs to be preheated, and the sensor should be cleaned for 50 seconds to stabilize the baseline. The sample detection time is 150 seconds, and purified air is used as the carrier gas. Each cleaning is performed at a 50-second interval, and the experiment is repeated 3 times.

[0059] Table 3 Comparison of volatile aroma compound content in treatment groups with different types of added sugars

[0060]

[0061] As shown in Table 3, the total content of aroma compounds in the enzymatically hydrolyzed peach pulp after sugar substitution was significantly improved. In particular, the total concentration of the enzymatically hydrolyzed peach pulp infused with steviol glycosides was 40.05% higher than that in the enzymatically hydrolyzed peach pulp with added sucrose.

[0062] Depend on Figure 1 It can be seen that the enzymatic hydrolyzed peach pulp after being soaked in steviol glycosides has significantly improved in terms of sweetness, peach aroma, floral aroma and fruit aroma, while the sourness and grassy taste have been reduced. Overall, the enzymatic hydrolyzed peach pulp with added steviol glycosides has a better overall flavor and achieves the effect of enhancing aroma.

[0063] Depend on Figure 2 It can be seen that the enzymatically hydrolyzed peach pulp with added sugar substitute is located relatively close to PC1, which is significantly different from other samples. This further illustrates that the overall flavor of the enzymatically hydrolyzed peach pulp after sugar substitute soaking is significantly different from other samples, and they have large differences in overall flavor.

[0064] In conclusion, among these five sweeteners, steviol glycosides are the most effective in improving the flavor quality of enzymatically hydrolyzed peach pulp.

[0065] Experiment 5 investigated the effect of adding different concentrations of steviol glycosides on the aroma enhancement of enzymatically hydrolyzed peach pulp. The aroma quality was comprehensively evaluated using GC-MS and sensory evaluation. The GC-MS results are shown in Table 4, and the sensory evaluation results are as follows: Figure 3 As shown.

[0066] Table 4 Comparison of volatile aroma compound content in treatment groups with different concentrations of steviol glycosides

[0067]

[0068] As shown in Table 4, the total flavor content of the enzymatically hydrolyzed peach pulp after 0.1% stevioside impregnation was the highest, and the contents of aldehydes, alcohols, and esters were significantly improved.

[0069] Sensory evaluation results as follows Figure 3 As shown, the enzymatically hydrolyzed peach pulp after 0.1% steviol glycoside impregnation has a better overall flavor profile, and its flavor is significantly improved compared with enzymatically hydrolyzed peach pulp after impregnation at other concentrations, achieving the effect of enhancing aroma through enzymatic hydrolysis.

[0070] Comparative Example 1

[0071] The aroma quality of the peach puree (prepared in Example 1) was comprehensively evaluated by GC-MS, sensory evaluation, and electronic nose.

[0072] Comparative Example 2

[0073] The peach pulp (prepared in Example 1) was subjected to vacuum freeze-drying (same as in Example 2), and its aroma quality was evaluated by GC-MS and sensory evaluation. Simultaneously, vacuum freeze-drying parameters (drying ratio, rehydration properties, electronic nose, textural characteristics, and color difference) were measured.

[0074] Comparative Example 3

[0075] The aroma quality of the enzymatically hydrolyzed peach pulp (prepared under the optimal conditions of Example 1) was comprehensively evaluated by GC-MS, sensory evaluation, and electronic nose.

[0076] Comparative Example 4

[0077] Enzymatically hydrolyzed peach pulp (prepared under optimal conditions in Example 1) was subjected to vacuum freeze-drying (same as in Example 2), and its aroma quality was evaluated by GC-MS and sensory evaluation. Simultaneously, vacuum freeze-drying parameters (drying ratio, rehydration properties, electronic nose, textural characteristics, and color difference) were measured.

[0078] The GC-MS results for comparative examples 1–4 are shown in Table 5, the vacuum freeze-drying index results are shown in Table 6, and the VFD sensory evaluation results are as follows: Figure 4 As shown.

[0079] Table 5 Comparison of volatile aroma compound content before and after VFD in raw peach pulp and enzymatically hydrolyzed peach pulp.

[0080]

[0081] Table 5 shows that the flavor of the peach pulp was significantly reduced after freeze-drying; Figure 4 It can be seen that the overall flavor profile of the freeze-dried enzymatically hydrolyzed peach pulp is better than that of the original peach pulp.

[0082] The drying ratio formula is as follows:

[0083]

[0084] Where: M1—mass of wet material before drying, g;

[0085] M—Mass of the dried product after drying, in grams.

[0086] The higher the sample drying ratio, the higher the degree of material dehydration.

[0087] Rehydration properties were assessed by observing and recording the time (s) required for the freeze-dried peach pulp sample to completely dissolve.

[0088] Table 6 Comparison of Vacuum Freeze-Drying Indicators of Different Treatment Groups

[0089]

[0090]

[0091] As shown in Table 6, the odor compound content of the enzymatically hydrolyzed peach pulp VFD sample impregnated with steviol glycosides was high after rehydration, with a total concentration of 560.10 μg / L, which is a significant increase compared to the odor content at other concentrations.

[0092] The steviol glycoside-infused enzymatically hydrolyzed peach pulp is harder and more brittle than the original peach pulp. Comparing the three, the steviol glycoside-infused enzymatically hydrolyzed peach pulp has the closest total color difference to the original peach pulp VFD product, and also the largest value.

[0093] And by Figure 4 It can be seen that, compared with the three reconstituted VFD products, the sugar-impregnated VFD product showed a significant improvement in overall flavor after reconstitution. Therefore, it can be concluded that after impregnation with 0.1% steviol glycosides, the enzymatically hydrolyzed peach pulp exhibited a better overall flavor profile, achieving the desired aroma-enhancing effect.

[0094] Depend on Figure 5 The electronic nose data revealed that these flavor compounds have high independence and good discriminability in the feature space, reflecting the high repeatability and stability of electronic nose data analysis.

[0095] In conclusion, the enzymatically hydrolyzed peach pulp after stevioside impregnation exhibits a more significant improvement in aroma and quality compared to the original peach pulp after vacuum freeze-drying, and is also of higher quality.

[0096] 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 method for preparing a freeze-dried product of peach pulp with rich flavor, characterized in that, Includes the following steps: (1) After removing the pits, peeling and cutting the peaches into pieces, they are treated to prevent browning, and then pulped to obtain peach pulp; (2) The peach pulp is enzymatically hydrolyzed to obtain enzymatically hydrolyzed peach pulp; (3) After adding steviosides to the enzymatically hydrolyzed peach pulp, vacuum freeze-drying is performed to obtain the freeze-dried peach pulp product; The enzymes used for enzymatic hydrolysis in step (2) are pectinase and β-glucosidase; The amount of steviol glycoside added is 0.025~0.1 wt%.

2. The preparation method according to claim 1, characterized in that, The anti-browning treatment in step (1) involves soaking the chopped peaches in an aqueous solution containing 0.5-0.7% citric acid and 0.01-0.03% L-ascorbic acid for 25-35 minutes.

3. The preparation method according to claim 2, characterized in that, When pulping in step (1), add 0.08~0.12% of sodium D-isoascorbate by weight of the peaches for color protection.

4. The preparation method according to claim 3, characterized in that, In step (2), the mass ratio of pectinase to β-glucosidase is 1:2~3; the total enzyme activity of pectinase and β-glucosidase is 25~35 U / g; the enzymatic hydrolysis temperature is 50~55 ℃ and the time is 2.5~3 h.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The vacuum freeze-drying process involves first quick-freezing in liquid nitrogen for 15-20 min, then freezing at -80 to -85 ℃ for 1.5-2 h, and finally freezing at a vacuum of 0.1-0.3 mbar and -50 to -60 ℃ for 40-48 h.

6. A freeze-dried product of peach pulp with rich flavor obtained by the preparation method according to any one of claims 1 to 5.

7. The use of steviol glycosides in enhancing the aroma of the flavorful freeze-dried peach pulp product according to claim 6, characterized in that, The amount of steviol glycoside added is 0.025~0.1 wt%.

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