Structured Raspberry Pulp Beverage

Abstract

This invention discloses an innovative process for a structured raspberry fruit beverage. The core of this process lies in a composite technology that uses enzymatic hydrolysis to moderately degrade raspberry pectin and cross-link it with calcium ions to structure and fix the fruit. This addresses the technical pain points in existing raspberry fruit beverage processing, balances fruit stability and original quality, and enhances the product's market competitiveness.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, specifically relating to a preparation process for a structured raspberry fruit beverage. More specifically, it relates to an innovative composite process that relies on enzymatic hydrolysis to moderately degrade raspberry pectin combined with calcium ion cross-linking for structural shaping. This process can effectively stabilize the integrity of raspberry fruit pieces, avoid softening, stratification, and sedimentation during processing and storage, and efficiently retain the original flavor and full-bodied chewy texture of raspberry pulp. It is applicable to the industrial production of fruit juice beverages and fruit-flavored drinks, with a core focus on quality upgrading and process innovation in fruit-flavored beverages.

[0002] Raspberry pulp is rich in vitamins, anthocyanins, and other nutrients, and has a unique flavor, making it a high-quality raw material for fruit-flavored beverages. However, the soft texture and high pectin content of raspberry pulp make it prone to softening, breaking, and separation or sedimentation of the pulp and juice during beverage processing and storage. This not only affects the sensory quality of the beverage but also leads to the loss of the original flavor of the pulp and a poorer chewing texture, thus limiting the industrial promotion and product upgrading of raspberry pulp beverages.

[0003] Addressing the aforementioned technical challenges, this invention focuses on the structural improvement and quality enhancement of raspberry fruit beverages. It innovatively proposes a composite process combining enzymatic hydrolysis for moderate pectin degradation with calcium ion cross-linking for structural fixation. Unlike traditional single enzymatic hydrolysis or cross-linking processes, this composite process achieves the dual benefits of "degrading pectin without damaging the fruit particle structure and cross-linking for fixation without sacrificing the original flavor." This represents a core innovative technology direction in the fruit beverage processing field regarding fruit particle morphology stabilization, flavor retention, and mouthfeel optimization. It can be widely applied to the production and processing of various fruit beverages, especially suitable for preparing fruit beverages from soft, easily perishable fruits such as raspberries and strawberries, providing core technical support for the research and industrial production of high-quality fruit beverages. Background Technology

[0004] Raspberries are brightly colored, have a unique flavor, and are rich in vitamins, anthocyanins, dietary fiber, and various minerals. Their outstanding nutritional value and high market acceptance make them a popular choice for fruit-based beverages, as they retain the original taste and nutrients of the fruit. However, raspberry cell walls contain a large amount of pectin, which is prone to excessive degradation during beverage processing, sterilization, and storage. This degradation damages the cell wall structure of the raspberry berries, leading to problems such as softening, breakage, and incomplete shape. Furthermore, it easily causes stratification and sedimentation in the beverage system, severely impacting the product's sensory quality and storage stability.

[0005] To address the aforementioned technical challenges, existing technologies often employ a single pectin degradation process or a calcium ion cross-linking process to treat raspberry berries, but both have significant drawbacks. The single pectin degradation process typically involves enzymatic hydrolysis. If the degree of enzymatic hydrolysis is not properly controlled, either insufficient pectin degradation results in hard raspberry berries with a poor chewy texture and poor compatibility with the beverage system, leading to stratification; or excessive enzymatic hydrolysis completely damages the cell walls of the berries, preventing them from maintaining their integrity. This not only causes the berries to become soft and mushy and settle, but also results in a significant loss of the original flavor compounds, substantially reducing the product's flavor and quality.

[0006] The single calcium ion cross-linking process mainly enhances the stability of fruit cell walls by combining calcium ions with carboxyl groups in pectin molecules to form a cross-linked structure. However, this process cannot fundamentally solve the core problem of pectin's easy degradation. Moreover, the degree of cross-linking is difficult to control. Excessive cross-linking will make the fruit particles too hard and dry, while insufficient cross-linking will fail to stabilize the shape of the fruit particles and prevent stratification and sedimentation. It is difficult to balance the integrity of the fruit particle shape, the stability of the beverage system, and the original flavor and full chewy texture of the fruit pulp.

[0007] In summary, existing processing technologies for raspberry fruit beverages generally suffer from problems such as difficulty in controlling the shape of the fruit pieces, poor flavor retention, and insufficient stability during product storage. These issues fail to meet consumers' high-quality demands for raspberry fruit beverages that are "complete in shape, full in taste, pure in flavor, and stable," and to some extent, limit the large-scale and high-quality development of the raspberry fruit beverage industry.

[0008] Therefore, developing a raspberry pulp beverage processing technology that can precisely control the degradation of raspberry pectin, stabilize the shape of the fruit pieces through structural shaping technology, and take into account the stability of the beverage system, the original flavor of the fruit pulp, and the full chewy texture has become a key technical problem that needs to be solved by those in the field. Summary of the Invention

[0009] This invention discloses an innovative process for a structured raspberry fruit beverage. The core of this process lies in a composite technology that uses enzymatic hydrolysis to moderately degrade raspberry pectin and cross-link it with calcium ions to structure and fix the fruit. This addresses the technical pain points in existing raspberry fruit beverage processing, balances fruit stability and original quality, and enhances the product's market competitiveness.

[0010] I. Background Technology Raspberry pulp is rich in vitamins, anthocyanins, and dietary fiber, and has a sweet and refreshing taste, making it a high-quality raw material for fruit-based beverages. However, the soft texture of raspberry pulp and the pectin in its cell walls are prone to natural degradation during processing and storage, leading to softening, breakage, and subsequent beverage stratification and pulp sedimentation. This severely impacts the sensory quality and market acceptance of the product. Current raspberry pulp beverage processing technologies often employ large amounts of stabilizers and thickeners to address pulp stability issues. While this can delay stratification to some extent, it destroys the original flavor of the raspberry pulp, resulting in a sticky texture and loss of the original chewy feel. Some processes use simple physical setting methods, which cannot fundamentally solve the problem of pulp softening caused by pectin degradation, resulting in short-lasting stability that fails to meet the needs of industrial production and long-term storage. Therefore, developing a raspberry beverage processing technology that can both maintain the integrity of raspberry pieces and prevent them from becoming soft, mushy, and settling, while also preserving the original flavor and full-bodied chewy texture of the fruit, has become a pressing technical challenge in this field.

[0011] II. Purpose of the Invention The purpose of this invention is to overcome the shortcomings of existing technologies in the processing of raspberry fruit beverages, such as the fruit pieces easily becoming soft and mushy, separating and settling, and the loss of original flavor and chewy texture. This invention provides an innovative process for a structured raspberry fruit beverage, which stabilizes the shape of raspberry fruit pieces by optimizing the process combination, while preserving their original flavor and chewy texture to the maximum extent, thereby improving product quality and market competitiveness.

[0012] III. Technical Solution To achieve the above-mentioned objectives, the core technical solution adopted by this invention is as follows: A composite process involving enzymatic hydrolysis to moderately degrade raspberry pectin, combined with calcium ion cross-linking and structural shaping, is used to prepare a structured raspberry fruit beverage. The specific process steps are as follows: 1. Raw material pretreatment: Select fresh raspberries that are moderately ripe, free from rot and damage. Remove the stems and impurities, rinse them with clean water, and drain the surface water. Place the treated raspberry berries in a sterile environment for later use.

[0013] 2. Moderate Degradation of Pectin via Enzymatic Hydrolysis: Pretreated raspberry berries are placed in an enzymatic hydrolysis tank, and an appropriate amount of deionized water is added to adjust the material-to-liquid ratio to 1:1.5-1:3 (m / v). The hydrolysis temperature is controlled at 45-55℃, and the pH value is 4.0-5.0. 0.02%-0.08% (by weight of the raspberry berries) of pectinase is added, and after stirring evenly, hydrolysis is carried out for 15-40 minutes to achieve moderate degradation of pectin, loosening the cell wall structure of the raspberry berries without destroying their integrity. The pectinase is a composite enzyme of neutral pectinase and pectin lyase, with a mass ratio of 1:0.8-1:1.2. This composite enzyme can specifically degrade the galacturonic acid bonds in raspberry pectin, avoiding excessive degradation that could lead to berry breakage, while also providing binding sites for subsequent calcium ion cross-linking.

[0014] 3. After the calcium ion cross-linking and structural shaping enzymatic hydrolysis is completed, a calcium ion reagent is added to the hydrolysate to adjust the calcium ion concentration to 0.05%-0.2% (m / v), and the mixture is stirred evenly. The cross-linking temperature is controlled at 35-45℃, the pH value at 5.5-6.5, and the cross-linking reaction is carried out for 20-30 minutes. The calcium ions form coordination bonds with the carboxyl groups exposed after pectin degradation, achieving the structural shaping of the raspberry berries, constructing a stable three-dimensional network structure, and stabilizing the berry morphology. The calcium ion reagent is food-grade calcium chloride or calcium lactate, preferably food-grade calcium chloride, which has good solubility, high cross-linking efficiency, and does not affect the original flavor of the raspberry.

[0015] 4. After subsequent processing and cross-linking, the raspberry granules are separated from the liquid. The granules are aseptically rinsed and then mixed with a pre-prepared beverage base liquid according to a preset ratio. The beverage base liquid is made of white sugar, citric acid, vitamin C, and deionized water to ensure a balanced sugar-acid ratio. After mixing, homogenization is performed at a pressure of 15-25 MPa and a temperature of 30-40°C to ensure even distribution of the granules in the beverage. Finally, pasteurization is performed at a temperature of 85-90°C for 10-15 seconds. After sterilization, the mixture is cooled to room temperature and aseptically filled to obtain the structured raspberry granule beverage.

[0016] IV. Beneficial Effects This invention employs a composite process combining enzymatic hydrolysis for moderate degradation of raspberry pectin with calcium ion cross-linking and structural shaping. Compared to existing technologies, it has the following significant beneficial effects: 1. Effectively stabilizes the integrity of raspberry berries, preventing softening, rotting, stratification, and sedimentation: Through moderate degradation by pectinase, the cell wall structure of raspberry berries is loosened without damaging their integrity. At the same time, calcium ions form stable coordination bonds with the carboxyl groups of the degraded pectin, constructing a three-dimensional network structure and achieving structural fixation of the berries. This fundamentally solves the technical problems of raspberry berries easily softening and breaking during processing and storage, as well as beverage stratification and berry sedimentation, extending the product's shelf life and improving its sensory stability.

[0017] 2. Retaining the original flavor and full-bodied chewy texture of the fruit: This process does not require the addition of large amounts of stabilizers and thickeners. It achieves fruit particle stability through the combined action of enzymatic hydrolysis and cross-linking, maximizing the preservation of the sweet and sour flavor and nutrients of the raspberry pulp. At the same time, the structured and shaped fruit particles maintain a full-bodied chewy texture, avoiding the sticky texture and flavor distortion caused by the addition of additives in existing processes, thus improving the product drinking experience.

[0018] 3. Simple process, strong controllability, suitable for industrial production: The process steps are clear, and key parameters such as enzymatic hydrolysis temperature, time, and calcium ion concentration are easy to control. No complicated production equipment is required. It can be implemented by modifying existing beverage production lines, resulting in low production costs and high production efficiency, which facilitates large-scale industrial application.

[0019] 4. High product safety: The pectinase and calcium ion reagent used in this process are all food-grade raw materials, without harmful additives, and meet food safety production standards. The resulting raspberry fruit beverage is nutritious, healthy, and has an excellent taste, meeting consumers' demand for high-quality, natural, and healthy food. Attached Figure Description

[0020] Figure 1 is a flowchart of the preparation process of the structured raspberry fruit beverage of the present invention. The flowchart clearly shows the complete implementation steps of the "composite process of enzymatic hydrolysis and moderate degradation of raspberry pectin combined with calcium ion cross-linking and structural shaping". Each step is sequentially connected and logically rigorous, corresponding to the preparation process in the specific embodiments, as detailed below: 1. The process begins with the raw material preparation step, which corresponds to the raw material preparation stage in the specific implementation method. The core purpose is to prepare all raw materials according to standard specifications, providing qualified raw materials for subsequent process steps. Specifically, fresh raspberries are selected that are 80-90% ripe, free from rot and damage, and have a uniform color; the pectinase used is endoglucuronidase with an enzyme activity ≥5000U / g, which can specifically hydrolyze the α-1,4-glycosidic bonds in raspberry pectin; food-grade calcium lactate is selected, as it has less impact on the taste of the fruit and a gentler setting effect compared to calcium chloride; the compound color-protecting solution is a mixture of disodium EDTA, VB3, and VC in a mass ratio of 1:1:5; the compound stabilizer is a mixture of xanthan gum and low-methoxyl pectin in a mass ratio of 0.08:0.15; white sugar and citric acid are both food-grade; and the purified water meets the GB 19298-2014 "Packaged Drinking Water" standard. All raw materials strictly adhere to the specifications required in the specific implementation method.

[0021] 2. After the raw materials are prepared, the raspberry granule pretreatment step is carried out. This step lays the foundation for subsequent enzymatic hydrolysis and cross-linking. The specific operation process and parameters strictly follow the requirements of the specific implementation method: First, wash and drain the fresh raspberries, put them into a pitter and pelletizer to remove the pits, and cut them into uniform granules with a diameter of 0.8-1.2cm. Avoid granules that are too large, which will make the shape unstable, or granules that are too small, which will affect the chewing texture. Then, soak the cut raspberry granules in a 0.07-0.1% compound color-protecting solution for 10-15 minutes. During the soaking process, stir gently at a speed of 50r / min to ensure uniform color protection. After soaking, centrifuge at a speed of 1000r / min for 5 minutes to remove excess water from the surface of the granules. Finally, the pretreated raspberry granules are obtained. This step can effectively prevent the raspberry granules from browning during subsequent processing and retain their original color.

[0022] 3. The pretreated raspberry berries undergo a pectin enzymatic hydrolysis and moderate degradation treatment step. This step is one of the core components of the composite process of this invention, and the operating parameters are completely consistent with the specific implementation method: First, the pretreated berries and purified water are mixed at a mass ratio of 1:1.5 and placed in a constant temperature water bath. The water bath temperature is adjusted to 35-40℃. Then, a preset amount of pectinase is added, and after stirring evenly, the temperature is maintained for enzymatic hydrolysis. The hydrolysis time is controlled at 15-30 minutes, and the mixture is stirred every 5 minutes to ensure uniform hydrolysis. Finally, the pectin degradation rate is controlled at 30-40%, achieving moderate pectin degradation—both destroying some of the cross-linking structure of pectin, creating conditions for subsequent calcium ion cross-linking, and avoiding excessive degradation that would cause the berries to soften and break. After the enzymatic hydrolysis reaction is completed, the water bath temperature is raised to 90-95℃ and kept at that temperature for 5 minutes to completely inactivate the pectinase and terminate the enzymatic hydrolysis reaction. Then, the mixture is cooled to room temperature to obtain the enzymatically hydrolyzed raspberry berries.

[0023] 4. After enzymatic hydrolysis, the raspberry berries undergo a calcium ion cross-linking and structural shaping process. This step is another core component of the composite process of this invention, with strictly matched operating procedures and parameters. Specific implementation method: A preset amount of calcium lactate is added to the enzymatically hydrolyzed raspberry berries, and the mixture is stirred at 150 r / min for 10-15 min using a high-speed stirrer to ensure uniform dispersion of calcium lactate in the berry system. Subsequently, the pH of the system is adjusted to 3.4-3.8 with citric acid to provide a suitable environment for calcium ion cross-linking. The system is then placed in an environment of 25-30℃ for static cross-linking for 20-30 min, allowing calcium ions (Ca²⁺) to coordinate with the carboxyl groups in the incompletely degraded pectin molecules of the raspberry berries, forming a stable three-dimensional network cross-linked structure. Finally, structured and shaped raspberry berries are obtained. This step effectively stabilizes the integrity of the berries, preventing softening, stratification, and sedimentation during subsequent processing and storage. It also locks in the moisture and flavor substances inside the berries, preserving the original flavor and full-bodied chewy texture of the fruit.

[0024] 5. The structured raspberry pieces are incorporated into the beverage blending process. This step aims to integrate the various ingredients with the raspberry pieces, creating a homogeneous and flavorful initial beverage product. The process strictly follows the specific implementation instructions: First, take a predetermined amount of purified water, add granulated sugar, citric acid, and a compound stabilizer. Stir at 200 rpm for 20-30 minutes using a high-speed mixer until all ingredients are completely dissolved, obtaining the blended liquid. Place the blended liquid in a homogenizer and homogenize twice at 15-20 MPa for 5 minutes each time to prevent stabilizer clumping and ensure a homogeneous texture. Then, add the structured raspberry pieces to the blended liquid and gently stir for 5-10 minutes to evenly disperse the pieces, resulting in the initial raspberry beverage product. The compound stabilizer works synergistically with calcium ions to form an "egg carton-skeleton" network structure, further enhancing the stability of the beverage system and reducing fruit particle sedimentation.

[0025] 6. The initial beverage sample enters the sterilization, filling, and storage steps. This step is the final stage of finished product preparation, and the operating parameters are completely consistent with the specific implementation method: the initial raspberry fruit beverage sample is placed in a water bath sterilizer and sterilized at 85℃ for 15 minutes, with gentle stirring during sterilization to prevent fruit particle sedimentation; after sterilization, it is rapidly cooled to below 30℃ to prevent the fruit particles from softening due to high temperature; aseptic filling is performed using a filling machine, and the product is immediately sealed with a sealing machine after filling to ensure product sterility; after sealing, the finished product is placed in a refrigerator and stored at 0-4℃, ultimately obtaining a finished raspberry fruit beverage with intact fruit particle shape, rich flavor, and good stability. Detailed Implementation

[0026] Features: Relying on a composite process that combines enzymatic hydrolysis to moderately degrade raspberry pectin with calcium ion cross-linking and structural shaping, it can stabilize the integrity of raspberry berries, prevent them from softening, rotting, and settling, and retain the original flavor and full-bodied chewy texture of the fruit.

[0027] I. Raw Material Preparation: Fresh Raspberries: Select fresh raspberries that are 80-90% ripe, free from rot and damage, and have a uniform color. Wash and drain the surface water. Pectinase: Use endoglucanase (enzyme activity ≥5000U / g), which can specifically hydrolyze the α-1,4-glycosidic bonds in raspberry pectin, achieving moderate pectin degradation. Purchased from a conventional biological enzyme manufacturer. Calcium Ion Source: Use food-grade calcium lactate, which has less impact on the taste of the fruit and a gentler setting effect compared to calcium chloride. Purchased from a food-grade raw material supplier. Color Protectant: Compound color protectant solution (disodium EDTA, VB3, and Vc mixed in a mass ratio of 1:1:5) to prevent browning of raspberry fruit. Stabilizer: Xanthan gum and low-methoxyl pectin are compounded in a mass ratio of 0.08:0.15 to synergistically form an "egg carton-skeleton" network structure with calcium ions, improving system stability. Sweetener: Food-grade white sugar. Acidity Regulator: Food-grade citric acid; purified water: conforms to GB 19298-2014 "Packaged Drinking Water" standard.

[0028] II. Preparation Process of Raspberry Fruit Beverage The core process of this invention is a "composite process of enzymatic hydrolysis to moderately degrade raspberry pectin combined with calcium ion cross-linking and structural shaping". The specific steps are as follows: Prepare the beverage according to the following mass proportions: 30-40 parts fresh raspberries, 0.04-0.08 parts pectinase, 0.1-0.5 parts calcium lactate, 0.07-0.1 parts composite color-protecting liquid, 0.2-0.3 parts compound stabilizer, 5-8 parts white sugar, 0.1-0.2 parts citric acid, and 50-60 parts purified water. Step 1: Raspberry Piece Pretreatment. Place washed and drained fresh raspberries into a pitter and dicer to remove the pits. Divide the raspberries into uniform pieces with a diameter of 0.8-1.2 cm. Avoid pieces that are too large, as this will cause them to lose their shape, or too small, as this will result in poor taste. Soak the diced raspberry pieces in purified water containing a compound color-protecting solution (0.07-0.1%) for 10-15 minutes. During soaking, gently stir at 50 rpm. After soaking, centrifuge at 1000 rpm for 5 minutes to remove excess surface moisture. The resulting pretreated raspberry pieces are ready for use. This step effectively prevents browning of the raspberry pieces during subsequent processing, preserving their original color.

[0029] Step 2: Moderate Degradation of Pectin via Enzymatic Hydrolysis. Place the pretreated raspberry berries in a constant temperature water bath, add purified water (berry to water mass ratio of 1:1.5), adjust the water bath temperature to 35-40℃, then add the pre-set amount of pectinase, stir well, and maintain this temperature for enzymatic hydrolysis. The hydrolysis time is controlled at 15-30 minutes. Stir every 5 minutes during the hydrolysis process to ensure uniform hydrolysis. The key to this step is "moderate degradation." By controlling the hydrolysis time, temperature, and enzyme dosage, the pectin on the surface and inside of the raspberry berries is partially degraded, with a degradation rate controlled at 30-40%. This breaks down some of the pectin's cross-linking structure, creating conditions for subsequent calcium ion cross-linking, while avoiding excessive degradation that would cause the berries to soften and break. After hydrolysis, raise the water bath temperature to 90-95℃ and maintain this temperature for 5 minutes to completely inactivate the pectinase, terminating the hydrolysis reaction. Then cool to room temperature to obtain the hydrolyzed raspberry berries. Note: The method for detecting pectin degradation rate is as follows: the pectin content in raspberry berries before and after enzymatic hydrolysis is determined by carbazole colorimetric method, and the degradation rate is calculated as (pectin content before enzymatic hydrolysis - pectin content after enzymatic hydrolysis) / pectin content before enzymatic hydrolysis × 100%.

[0030] Step 3: Calcium Ion Crosslinking and Structural Shaping Treatment. Add a predetermined amount of calcium lactate to the enzymatically hydrolyzed raspberry berries. Stir at 150 rpm for 10-15 minutes using a high-speed stirrer to ensure uniform dispersion of calcium lactate in the berry system. Then adjust the pH of the system to 3.4-3.8 (using citric acid) and allow it to stand at 25-30℃ for 20-30 minutes for crosslinking. Calcium ions (Ca²⁺) coordinate with the carboxyl groups in the incompletely degraded pectin molecules of the raspberry berries, forming a three-dimensional network crosslinked structure. This achieves structural shaping of the raspberry berries, stabilizing their integrity and preventing softening, stratification, and sedimentation during subsequent processing and storage. Simultaneously, this crosslinked structure locks in moisture and flavor compounds within the berries, preserving the original flavor and full-bodied chewy texture of the fruit. After crosslinking, structured raspberry berries are obtained.

[0031] Step 4: Beverage Preparation. Take the pre-set amount of purified water, add white sugar, citric acid, and compound stabilizers (xanthan gum and low-methoxyl pectin). Stir with a high-speed mixer at 200 rpm for 20-30 minutes until all excipients are completely dissolved to obtain the preparation solution. Place the preparation solution in a homogenizer and homogenize twice at a pressure of 15-20 MPa, 5 minutes each time, to ensure a uniform consistency and prevent stabilizer clumping. Then add the structured raspberry pieces to the preparation solution and gently stir for 5-10 minutes to evenly disperse the pieces, obtaining the initial raspberry beverage product. The compound stabilizers can synergistically enhance the stability of the beverage system with the calcium ion cross-linking network, significantly reducing the sedimentation rate of the fruit pieces.

[0032] Step 5: Sterilization, Filling and Storage. Place the initial raspberry fruit beverage sample into a water bath sterilizer and sterilize it at 85℃ for 15 minutes. Stir gently during sterilization to prevent fruit particles from settling. After sterilization, quickly cool it to below 30℃ and aseptically fill it using a filling machine. Immediately after filling, seal it with a sealing machine and place it in a refrigerator at 0-4℃ to obtain the finished raspberry fruit beverage.

[0033] Specific Embodiment Example 1 This embodiment provides a raspberry fruit beverage, prepared according to the following mass proportions: 35 parts fresh raspberries, 0.06 parts endogalacturonase (enzyme activity 5000U / g), 0.3 parts calcium lactate, 0.08 parts compound color-protecting liquid, 0.23 parts compound stabilizer (0.08 parts xanthan gum, 0.15 parts low methoxy pectin), 6 parts white sugar, 0.15 parts citric acid, and 55 parts purified water. The preparation process is as follows: 1. Pretreatment: Wash and drain fresh raspberries, remove pits and cut into granules (1.0cm in diameter), soak in 0.08% compound color-protecting solution for 12 minutes, centrifuge to remove excess water, and set aside; 2. Enzymatic degradation: Mix pretreated fruit granules with purified water at a ratio of 1:1.5, place in a 38℃ constant temperature water bath, add pectinase, stir evenly, and enzymatically hydrolyze for 22 minutes, with a pectin degradation rate of 35%; then inactivate the enzyme at 92℃ for 5 minutes, and cool to room temperature; 3. Cross-linking and shaping: Add calcium lactate, stir at 150r / min for 12 minutes, adjust the pH to 3.6 with citric acid, and allow to cross-link at 28℃ for 25 minutes; 4. Preparation: Add white sugar, citric acid, and compound stabilizer to purified water, stir to dissolve, homogenize twice at 18MPa, add structured fruit granules, and gently stir for 8 minutes; 5. Sterilization and filling: Sterilize in an 85℃ water bath for 15 minutes, cool to below 30℃, aseptically fill and seal, and store at 0-4℃. Finished product testing: The raspberry fruit pieces in this beverage are intact, without any softness, rot, or breakage, and show no stratification or sedimentation after 90 days of standing; the fruit pieces have a full-bodied chewy texture, retaining the original aroma and sweet and sour flavor of raspberries; all indicators meet the GB / T 31121-2014 standard "Fruit and vegetable juices and their beverages".

[0034] Example 2 This example provides a raspberry fruit beverage, prepared according to the following parts by weight: 30 parts fresh raspberries, 0.04 parts endogalacturonase (enzyme activity 5000U / g), 0.1 parts calcium lactate, 0.07 parts compound color-protecting liquid, 0.23 parts compound stabilizer (0.08 parts xanthan gum, 0.15 parts low methoxy pectin), 5 parts white sugar, 0.1 parts citric acid, and 60 parts purified water. The preparation process is as follows: 1. Pretreatment: Wash and drain fresh raspberries, remove pits and cut into granules (0.8cm in diameter), soak in 0.07% compound color-protecting solution for 10 minutes, centrifuge to remove excess water, and set aside; 2. Enzymatic degradation: Mix pretreated fruit granules with purified water at a ratio of 1:1.5, place in a 35℃ constant temperature water bath, add pectinase, stir evenly, and enzymatically hydrolyze for 15 minutes, with a pectin degradation rate of 30%; then inactivate the enzyme at 90℃ for 5 minutes, and cool to room temperature; 3. Cross-linking and shaping: Add calcium lactate, stir at 150r / min for 10 minutes, adjust the pH to 3.4 with citric acid, and allow to cross-link at 25℃ for 20 minutes; 4. Preparation: Add white sugar, citric acid, and compound stabilizer to purified water, stir to dissolve, homogenize twice at 15MPa, add structured fruit granules, and gently stir for 5 minutes; 5. Sterilization and filling: Sterilize in an 85℃ water bath for 15 minutes, cool to below 30℃, aseptically fill and seal, and store at 0-4℃. Finished product testing: The raspberry fruit pieces in this beverage are intact, with no obvious softening or rotting, and the stratification and sedimentation rate after 90 days of standing is ≤4.3%; the fruit pieces have a full-bodied taste, with a rich original raspberry flavor, and a pleasant sweet and sour taste; all indicators meet the GB / T 31121-2014 standard for "Fruit and Vegetable Juices and Beverages".

[0035] Example 3 This example provides a raspberry fruit beverage, prepared according to the following parts by weight: 40 parts fresh raspberries, 0.08 parts endogalacturonase (enzyme activity 5000U / g), 0.5 parts calcium lactate, 0.1 parts compound color-protecting liquid, 0.23 parts compound stabilizer (0.08 parts xanthan gum, 0.15 parts low methoxy pectin), 8 parts white sugar, 0.2 parts citric acid, and 50 parts purified water. The preparation process is as follows: 1. Pretreatment: Wash and drain fresh raspberries, remove pits and cut into granules (1.2cm in diameter), soak in 0.1% compound color-protecting solution for 15 minutes, centrifuge to remove excess water, and set aside; 2. Enzymatic degradation: Mix pretreated fruit granules with purified water at a ratio of 1:1.5, place in a 40℃ constant temperature water bath, add pectinase, stir evenly, and enzymatically hydrolyze for 30 minutes, with a pectin degradation rate of 40%; then inactivate the enzyme at 95℃ for 5 minutes, and cool to room temperature; 3. Cross-linking and shaping: Add calcium lactate, stir at 150r / min for 15 minutes, adjust the pH to 3.8 with citric acid, and let stand at 30℃ for 30 minutes for cross-linking; 4. Preparation: Add white sugar, citric acid, and compound stabilizer to purified water, stir to dissolve, homogenize twice at 20MPa, add structured fruit granules, and gently stir for 10 minutes; 5. Sterilization and filling: Sterilize in an 85℃ water bath for 15 minutes, cool to below 30℃, aseptically fill and seal, and store at 0-4℃. Finished product testing: The raspberry fruit pieces in this beverage are intact, without softening or rotting, and show good stability after 90 days of standing; the fruit pieces have a full and elastic texture, a rich original raspberry flavor, and no off-flavors; all indicators meet the GB / T 31121-2014 standard "Fruit and vegetable juices and their beverages".

[0036] IV. Effect Verification and Comparative Experiment 4.1 Experimental Grouping Three comparative experiments were set up. Each group followed the raw material ratio of Example 1, only changing the process conditions, and the other operations were the same: Control Group 1: No pectin enzymatic hydrolysis treatment was performed, only calcium ion cross-linking and shaping were performed; Control Group 2: Only pectin enzymatic hydrolysis treatment was performed, without calcium ion cross-linking and shaping; Experimental Group: The composite process of moderate degradation of raspberry pectin by enzymatic hydrolysis combined with calcium ion cross-linking and structural shaping of the present invention was adopted (Process of Example 1). 4.2 Detection Indicators and Results Sensory evaluation, stability test and flavor substance content test were conducted on four groups of samples (3 control groups + 1 experimental group). The results are as follows: (1) Sensory evaluation: Five professional evaluators scored according to a unified standard (total score of 100 points). The evaluation indicators included fruit shape (30 points), taste (30 points), flavor (30 points) and color (10 points). The results were as follows: The experimental group scored 92 points, with intact fruit, full taste and rich flavor; the control group 1 scored 70 points, with relatively intact fruit shape, but the taste was hard and the flavor was insufficient; the control group 2 scored 65 points, with fruit that was easy to soften and rot, obvious layering, and dense taste without chewiness. (2) Stability test: The samples were placed at room temperature of 25℃ for 90 days to detect the stratification and sedimentation and the fruit breakage rate. The results were as follows: No stratification and sedimentation were observed in the experimental group, and the fruit breakage rate was ≤2%; stratification and sedimentation were obvious in control group 1, and the fruit breakage rate was 8%; stratification and sedimentation were severe in control group 2, and the fruit breakage rate was 35%. (3) Detection of flavor substance content: The retention rate of characteristic flavor substances (raspberry ketone and organic acid) in raspberries was detected by gas chromatography. The results were as follows: The retention rate of raspberry ketone in the experimental group was 88%, and the retention rate of organic acid was 90%; the retention rate of raspberry ketone in control group 1 was 72%, and the retention rate of organic acid was 75%; the retention rate of raspberry ketone in control group 2 was 60%, and the retention rate of organic acid was 65%. 4.3 Experimental Conclusions Comparative experimental results show that the composite process of enzymatic hydrolysis and moderate degradation of raspberry pectin combined with calcium ion cross-linking and structural shaping adopted in this invention can significantly improve the stability of raspberry fruit beverages compared to single calcium ion cross-linking or single pectin enzymatic hydrolysis processes. It effectively stabilizes the intact shape of the fruit pieces, prevents softening, stratification, and sedimentation, and significantly improves the retention rate of original raspberry flavor substances, giving the beverage a full-bodied chewy texture. This solves the technical problems of traditional raspberry fruit beverages, such as easy softening, stratification, and severe flavor loss.

[0037] V. Key Process Points 1. "Moderation" of Pectin Enzymatic Hydrolysis: Hydrolysis time, temperature, and enzyme dosage are crucial for controlling the pectin degradation rate. Insufficient hydrolysis (degradation rate < 30%) results in insufficient pectin cross-linking sites, poor calcium ion cross-linking effect, and difficulty in stabilizing the fruit morphology. Excessive hydrolysis (degradation rate > 40%) damages the cell walls of raspberry berries, making them prone to softening and breakage, and losing their chewy texture. This invention controls the pectin degradation rate at 30-40% by controlling the hydrolysis parameters to achieve the best hydrolysis effect. 2. Control of Calcium Ion Cross-linking Conditions: Calcium ion concentration, system pH, and cross-linking time directly affect the cross-linking effect. Controlling the calcium lactate concentration at 0.1-0.5%, the pH at 3.4-3.8, and the cross-linking time at 20-30 min allows calcium ions to fully combine with pectin molecules, forming a stable three-dimensional network structure, while avoiding the astringent taste caused by excessive calcium ions. 3. Synergistic effect of color protection and stabilizers: The compound color-protecting liquid effectively prevents browning of raspberry berries, preserving their original color; the combination of xanthan gum and low-methoxyl pectin synergistically forms an "egg carton-skeleton" network structure with calcium ions, further enhancing the stability of the beverage system, reducing fruit sedimentation, and without affecting the taste and flavor of the beverage. The above descriptions are merely specific embodiments of the present invention and are not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a raspberry fruit beverage, characterized in that, The composite process of enzymatic hydrolysis for moderate degradation of raspberry pectin combined with calcium ion cross-linking and structural shaping includes the following steps: (1) Raspberry granule pretreatment: Select fresh raspberries with a maturity of 80-90%, no rot, no damage, and uniform color. Wash, drain, remove pits, and cut into granules to obtain raspberry granules with a particle size of 0.8-1.2cm. Soak the raspberry granules in the composite color-protecting solution for 10-15min. After soaking, centrifuge to remove excess water from the surface and set aside. The composite color-protecting solution is composed of disodium ethylenediaminetetraacetate, VB3, and Vc mixed in a mass ratio of 1:1:5, and the concentration of the color-protecting solution is 0.07-0.1%. (2) Pectin enzymatic hydrolysis for moderate degradation: Mix the pretreated raspberry granules with purified water in a mass ratio of 1:1.

5. Mix and place in a constant temperature water bath at 35-40℃. Add pectinase for enzymatic hydrolysis for 15-30 minutes, and control the pectin degradation rate to 30-40%. After enzymatic hydrolysis, raise the temperature to 90-95℃ and keep warm for 5 minutes to inactivate the pectinase. Cool to room temperature to obtain enzymatically hydrolyzed raspberry granules. The pectinase is endogalacturonase with an enzyme activity ≥5000U / g, and the amount added is 0.04-0.08% of the mass of the raspberry granules. (3) Calcium ion cross-linking and structural shaping treatment: Add calcium lactate to the enzymatically hydrolyzed raspberry granules, stir for 10-15 minutes to disperse the calcium lactate evenly, adjust the pH value of the system to 3.4-3.8, and place in a 25-30℃ environment for static cross-linking for 20-30 minutes to obtain structurally shaped raspberry granules. The amount of calcium lactate added is 0.1-0.5% of the mass of the raspberry granules. (4) Beverage preparation: Take purified water, add white sugar, citric acid, and compound stabilizer, stir to dissolve and homogenize, then add structured raspberry granules, gently stir to disperse the granules evenly, and obtain the initial beverage product; the compound stabilizer is composed of xanthan gum and low-methoxyl pectin in a mass ratio of 0.08:0.15, and the amount added is 0.2-0.3% of the total beverage mass; the amount of white sugar added is 5-8% of the total beverage mass, and the amount of citric acid added is 0.1-0.2% of the total beverage mass; the homogenization pressure is 15-20 MPa, the number of homogenization times is 2, and each time is 5 minutes; (5) Sterilization, filling and storage: sterilize the initial beverage product in a water bath at 85℃ for 15 minutes, cool to below 30℃ and then aseptically fill and seal, and store in a refrigerator at 0-4℃ to obtain the finished raspberry granule beverage; the raw materials of the raspberry granule beverage are: 30-40 parts by mass of fresh raspberries. 0.04-0.08 parts pectinase, 0.1-0.5 parts calcium lactate, 0.07-0.1 parts compound color-protecting solution, 0.2-0.3 parts compound stabilizer, 5-8 parts white sugar, 0.1-0.2 parts of raw materials and 50-60 parts of purified water; the raspberry fruit beverage prepared by the aforementioned composite process shows no stratification or sedimentation after 90 days of standing, with a fruit breakage rate of ≤2%, a retention rate of ≥88% for raspberry characteristic flavor compounds (raspberry ketones) and ≥90% for organic acids, and the fruit pieces remain intact with a full, chewy texture.

2. The preparation method according to claim 1, characterized in that, The centrifugation speed in step (1) is 1000 r / min and the centrifugation time is 5 min; during the soaking process, the mixture is gently stirred at a speed of 50 r / min.

3. The preparation method according to claim 1, characterized in that, During the enzymatic hydrolysis process described in step (2), the mixture is stirred once every 5 minutes to ensure uniform hydrolysis. The pectin degradation rate is determined by the carbazole colorimetric method, and the calculation formula is: degradation rate = (pectin content before enzymatic hydrolysis - pectin content after enzymatic hydrolysis) / pectin content before enzymatic hydrolysis × 100%.

4. The preparation method according to claim 1, characterized in that, The stirring speed in step (3) is 150 r / min; the pH value of the system is adjusted with citric acid.

5. The preparation method according to claim 1, characterized in that, The stirring speed for dissolving in step (4) is 200 r / min, and the stirring time is 20-30 min; the time for dispersing and stirring the fruit particles is 5-10 min.

6. The preparation method according to claim 1, characterized in that, During the sterilization process described in step (5), stir gently to avoid fruit particle sedimentation; the purified water complies with GB 19298-2014 "Packaged Drinking Water" standard, and the finished raspberry fruit beverage complies with GB / T 31121-2014 "Fruit and Vegetable Juices and Their Beverages" standard.

7. A raspberry fruit beverage prepared by any one of the methods described in claims 1-6, characterized in that, The raspberry fruit beverage contains whole raspberry pieces that are neither soft nor broken, retaining the original flavor of raspberries. After standing for 90 days, there is no stratification or sedimentation, and the fruit pieces have a full-bodied chewing texture.

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