Method of inhibiting texture and flavor deterioration of jam by blocking metabolic reprogramming of pectin-degrading bacteria

Abstract

The application discloses a method for blocking pectin-degrading bacteria metabolic reprogramming to inhibit jam texture and flavor deterioration, and belongs to the field of fruit and vegetable fine processing. In view of the technical problem that the existing jam is subjected to double deterioration of texture softening and water separation and flavor change due to pectin-degrading bacteria metabolic reprogramming during storage, the application solves the problem through the following scheme: fruit raw materials with a methyl esterification degree of 52% to 58%, an acetylation degree of 3% to 10% and rhamnogalacturonan polysaccharide less than 30% are crushed, then sodium citrate, calcium dihydrogen phosphate and low-acyl gellan gum are added in sequence, and lemon acid is added dropwise to adjust pH; then, ORP is adjusted through oxygen micro-nano bubble aeration; finally, a plant source bacteriostatic compound is added, and homogenization, sterilization and filling are performed. The application synergistically acts from the double aspects of pectin structure protection and microbial metabolism blocking, can effectively inhibit jam texture softening and flavor deterioration during storage, significantly prolongs the shelf life of the product, and is suitable for quality precise regulation in jam industrial production.

Description

Technical Field

[0001] This invention relates to the field of fruit and vegetable processing. More specifically, this invention relates to a method for inhibiting the deterioration of the texture and flavor of jams by blocking the metabolic reprogramming of pectin-degrading bacteria. Background Technology

[0002] Commercially available jams generally employ pasteurization combined with sealed packaging, achieving only commercial sterility. This process fails to completely eliminate acid- and heat-resistant microbial spores and dormant cells, leaving behind low-activity endogenous pectinase, which poses a risk of quality deterioration during storage. The texture of fruit raw materials is primarily determined by the structure of their cell walls and middle lamellae. The fibrous network structure, mainly composed of pectin, determines the mechanical properties of the cell walls, and the pectin depolymerization process directly affects the jam's water-holding capacity. During long-term storage in suboptimal environments, the continuous degradation of pectin, the collapse of the colloidal network, and the reactivation of spores lead to a dual deterioration of texture—softening, water separation, and off-flavor formation—a key bottleneck restricting the industry's development.

[0003] Recent studies have found that the quality deterioration of jam during storage stems not only from the structural degradation of pectin itself, but also from the complex interaction mechanisms between pectin and microorganisms. Under high-sugar and high-acid environmental stress, Bacillus (such as Bacillus licheniformis) undergoes metabolic reprogramming, producing off-flavor substances such as isobutyric acid, isobutyraldehyde, and furfural, accelerating flavor rancidity. Simultaneously, they synthesize and secrete large amounts of thermostable polygalacturonase (PG) and pectin lyase (PL), which continuously break down pectin molecular chains and disrupt the tightly bound network structure of pectin and water, leading to the release of water molecules and causing water separation. This water separation increases water activity, providing more favorable conditions for the proliferation of Bacillus vegetative cells. Furthermore, thermostable molds such as *Cryptomyces* and *Penicillium* are another major producer of pectinase. While osmophilic yeasts and lactic acid bacteria do not produce pectinase, they can utilize hydrolysis products to proliferate and produce acids and alcohols. These multiple factors combined exacerbate shelf-life quality deterioration. Ultimately, the increased water activity resulting from pectin depolymerization further activates microbial metabolism, forming a vicious cycle of "pectin depolymerization → increased water activity → accelerated microbial proliferation → increased pectinase secretion → further pectin depolymerization".

[0004] However, existing jam preservation technologies mostly rely on chemical preservatives, high-temperature sterilization, or single stabilizers. Current processes only rely on short-term high-temperature sterilization and passively inhibit microbial proliferation in a high-sugar and high-acid environment. They have not yet achieved a fundamental breakthrough at the level of the interaction mechanism between pectin and microorganisms, and have ignored the metabolic reprogramming process of pectin-degrading bacteria and off-flavor-producing bacteria. They have not fully considered that the thermodynamic microenvironment of tomato sauce is composed of factors such as moisture state, viscosity, redox potential, and pH. Therefore, they lack a dual blocking strategy of thermodynamic microenvironment regulation and pectin network protection, making it difficult to maintain the stability of jam texture and flavor in the long term. This invention is based on the cascading chain of jam quality deterioration, targeting the metabolic reprogramming pathway of pectin-degrading bacteria. It constructs a dual barrier from the pectin molecular level and the microbial interaction level, protecting the pectin structure and blocking microbial metabolism. Through precise selection of pectin raw materials, rigidification of pectin molecular chains and enhancement of physical cross-linking, in-situ buffering and pH steady-state regulation, oxygen microbubble oxidation regulation, and plant-derived ternary antibacterial compound, combined with segmented step-temperature static maintenance after filling, it not only cuts off the pectin-pectinase-producing microbial deterioration interaction pathway, but also broadly inhibits pectin-degrading microorganisms. It simultaneously inhibits texture and flavor deterioration from multiple dimensions, significantly extending product shelf life and reducing water separation rate and off-odor generation rate under normal temperature storage conditions. It provides a standardized and replicable precision quality control technology solution for the jam processing industry. Summary of the Invention

[0005] Another objective of this invention is to provide a method for inhibiting the deterioration of the texture and flavor of jam by blocking the metabolic reprogramming of pectin-degrading bacteria. This invention addresses the common technical deficiencies in existing jam processing technologies, such as the easy degradation of the fine structure of pectin, large fluctuations in the processing environment, the easy metabolic reprogramming of pectin-degrading Bacillus, the continuous production of degradation enzymes by bacteria during conventional constant-temperature storage of finished products, and the significant deterioration of texture and flavor during shelf life. This invention achieves long-term inhibition of pectin decomposition and extends the shelf life of jam quality stability by precisely selecting raw materials, rigidifying and enhancing the physical cross-linking of pectin molecular chains, in-situ buffering and pH steady-state regulation, modifying the oxidation-reduction potential of oxygen micro-nano bubbles, using plant-derived ternary compound antibacterial agents, mild homogenization and short-time sterilization, and a segmented step-temperature static curing process after canning.

[0006] To achieve these objectives and other advantages according to the present invention, a method for inhibiting the deterioration of the texture and flavor of jam by blocking the metabolic reprogramming of pectin-degrading bacteria is provided, comprising the following steps: Step 1: Take fruits with a pectin structure of 52%–58% methyl esterification (DM), 3%–10% acetylation (DAC), and <30% rhamnogalacturonic acid polysaccharide (RG-I) as raw materials, crush them, and obtain jam; Step 2: Add 0.15-0.30 w / w% sodium citrate, 0.08-0.15 w / w% calcium dihydrogen phosphate, and 0.2-0.4 w / w% low-acyl gellan gum to the jam and mix. Then, add citric acid dropwise to the jam system to stabilize the pH of the jam system to 4.0-4.2 to obtain the jam treatment solution. Step 3: The jam treatment liquid is aerated with oxygen through micropores using a micro-nano bubble generator until the oxidation-reduction potential of the jam treatment liquid is +150 to +250 mV, thus obtaining pretreated jam. Step 4: Add 0.1-0.5 g / kg of plant-derived antibacterial complex to the pretreated jam, and then homogenize, sterilize, and fill the jam in sequence. After filling, the jam is cured in a gradient temperature environment in the dark to obtain the filled jam. The gradient temperature curing method is as follows: first, let it stand at 12-16℃ for 12-14 h, and then raise the temperature to 22-24℃ and let it stand for 10-14 h.

[0007] Preferably, in step one, the crushing method is as follows: the jam raw material is crushed at a speed of 1500~2000 r / min and a temperature of 85 ℃ for 30~60 s to obtain jam, so as to achieve instantaneous thermal inactivation of pectin esterase and reduce the degradation of pectin by endogenous pectinase during processing. Preferably, in step two, the mixing method is as follows: sodium citrate, calcium dihydrogen phosphate, and low-acyl gellan gum are added to the jam, and then reacted at 55 ℃ and 65 r / min for 15 min.

[0008] Preferably, in step four, the plant-derived antibacterial complex includes rosmarinic acid, chlorogenic acid, and nisin in a mass ratio of 1:1.3~10:0.5~4 (i.e., the mass ratio of rosmarinic acid, chlorogenic acid, and nisin is 1:(1.3~10):(0.5~4)).

[0009] Preferably, in step four, the homogenization conditions are: temperature 25~30℃ and pressure 10-15MPa.

[0010] Preferably, in step four, the sterilization method is to treat at 80–90°C for 20–30 seconds.

[0011] The present invention has at least the following beneficial effects: First, this invention preferentially uses highly methylated (DM 52%~58%) and moderately acetylated (DAC 3%~10%) pectin raw materials. The highly methylated pectin enhances interchain entanglement and steric hindrance by utilizing its more extended molecular conformation in a weakly acidic system. At the same time, the methyl ester group has a steric protection effect on the C6 carboxyl group of the galacturonic acid residues in the main chain, which can effectively shield the affinity and cleavage of the α-1,4 glycosidic bonds of the main chain by polygalacturonase (PG) and pectin lyase (PL). Combined with short-term high-shear fragmentation at 85℃, 1500~2000 r / min, and 30~60s, the endogenous pectinase activity is deactivated, and excessive mechanical force is avoided to prevent main chain breakage and oligosaccharide release. This delays the metabolic activation of putrefactive bacteria from two levels: maintaining molecular conformation and controlling carbon source substrate.

[0012] Secondly, in this invention, sodium citrate combined with calcium dihydrogen phosphate provides calcium ions that coordinate with the free carboxyl groups of the pectin molecular chains, increasing the rigidity and reducing the flexibility of the molecular chains. Simultaneously, low-acyl gellan gum is introduced as a skeletal filler, interspersed within the gaps in the pectin molecular network. These three elements synergistically create a multi-affinity pectin network synergistic system of "small molecule buffering - ion patch reinforcement - colloidal structure support," reducing pectinase binding sites, maintaining the colloidal structural stability of the jam at the molecular level, inhibiting water molecule flow, and achieving water-locking and thickening effects, thereby maintaining the long-term textural stability of the jam.

[0013] Third, based on a weakly acidic steady-state buffer system, this invention, combined with precise fine-tuning using citric acid, can stably maintain the system pH at 4.0–4.2 throughout the entire process of crushing, homogenization, concentration, and sterilization. This steady-state weakly acidic environment, on the one hand, stabilizes the electrostatic repulsion / hydrogen bond equilibrium conformation of the high-methyl ester pectin molecular chains, inhibiting the pectin backbone breakage caused by non-enzymatic β-elimination reactions during high-temperature processing; on the other hand, it significantly reduces the intracellular ATP synthase activity of acid-resistant spoilage bacteria (such as Bacillus vegetative cells and Hymenopterus xylostella), forcing the bacterial community into a state of slowed growth, simultaneously achieving the dual effects of pectin structural stability and microbial metabolic inhibition, thus perfecting the dual-barrier regulatory system.

[0014] Fourth, this invention uses oxygen micro-nano bubble aeration as a purely physical means to regulate the oxidation-reduction potential of the system, stably forming a micro oxidation-reduction environment of +150 to +250mV, interfering with the oxidation-reduction sensing signal pathway of pectinase-producing strains, further blocking the activation of their pectin degradation metabolic pathway, and effectively inhibiting the metabolic reprogramming of putrefactive bacteria at the microenvironment level.

[0015] Fifth, based on stable pH, ORP, and microenvironment, this invention combines a ternary plant-derived antibacterial complex of rosmarinic acid, chlorogenic acid, and nisin to synergistically inhibit the proliferation of vegetative cells of spoilage microorganisms in jam, especially pectinase-producing strains, thereby reducing their pectinase secretion. Furthermore, short-term mild sterilization at 80–90 °C significantly reduces excessive thermal degradation of pectin and thermal deterioration of aroma components, simultaneously inactivating bacterial vegetative cells and blocking the multi-level chain reaction of "pectin depolymerization – microbial activation – textural collapse – flavor deterioration."

[0016] Sixth, the gradient temperature curing after filling promotes the full stabilization of the intermolecular cross-linking network, and reduces the metabolic activity of residual microorganisms through staged temperature changes before storage. Combined with the multiple hurdle effects of high sugar, high acid and antibacterial agents, this invention delays the synchronous deterioration of the jam's texture and flavor during storage and shortens the product's shelf life and quality degradation rate.

[0017] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0018] Figure 1 This is a schematic flowchart of the jam preparation method according to an embodiment of the present invention; Figure 2 Apparent viscosity curves of the jams prepared in the embodiments and comparative examples of the present invention; Figure 3 The low-field nuclear magnetic resonance (LF-NMR) inversion spectra of the jams prepared in the embodiments and comparative examples of the present invention; Figure 4 This is a particle size distribution diagram of the jam prepared according to an embodiment of the present invention; Figure 5 This is a molecular weight distribution diagram of pectin in the jams prepared in the embodiments and comparative examples of the present invention; Figure 6 The TG-DTG curves of the jams prepared in the embodiments and comparative examples of the present invention are shown. Figure 7 This is a schematic diagram of the dynamics simulation between pectin molecules in the jam system prepared according to an embodiment of the present invention. Figure 8 The number of hydrogen bonds between pectin molecules in the jam system prepared in the embodiments of the present invention changes over time. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0020] The process for preparing and filling the jam according to this invention is as follows: Figure 1 As shown; <Example 1> A method for inhibiting the deterioration of jam texture and flavor by blocking the metabolic reprogramming of pectin-degrading bacteria includes the following steps: Step 1: Take fruits with a pectin structure of 52% methyl esterification, 3% acetylation, and 20% rhamnogalacturonic acid polysaccharide as raw materials, and crush them to obtain jam. Step 2: Add 0.15 w / w% sodium citrate, 0.08 w / w% calcium dihydrogen phosphate, and 0.2 w / w% low acyl gellan gum to the jam and mix. Then add citric acid dropwise to the jam system to stabilize the pH of the jam system to 4.0, and obtain the jam treatment solution. Step 3: The jam treatment liquid is aerated with oxygen through micropores using a micro-nano bubble generator until the oxidation-reduction potential (ORP) of the jam treatment liquid is +150 mV, thus obtaining pretreated jam. Step 4: Add 0.1g / kg (i.e., 0.1g plant-derived antibacterial complex per kilogram of pre-treated jam) of plant-derived antibacterial complex to the pre-treated jam, and then perform homogenization, sterilization, and filling in sequence. After filling, the jam is cured in a gradient temperature environment in the dark to obtain the filled jam. The gradient temperature curing method is as follows: first, let it stand at 12℃ for 12h, and then raise the temperature to 22℃ and let it stand for 10h.

[0021] In step one, the crushing method is as follows: the jam raw materials are crushed for 30 seconds at a speed of 1500 r / min and a temperature of 85 ℃ to obtain jam; In step two, the mixing method is as follows: sodium citrate, calcium dihydrogen phosphate, and low-acyl gellan gum are added to the jam, and then reacted at 55 ℃ and 65 r / min for 15 min.

[0022] In step four, the plant-derived antibacterial complex includes rosmarinic acid, chlorogenic acid, and nisin in a mass ratio of 1:1.3:0.5.

[0023] In step four, the homogenization conditions are: temperature 25℃ and pressure 10MPa.

[0024] In step four, the sterilization method is to treat at 80℃ for 20 seconds.

[0025] <Example 2> A method for inhibiting the deterioration of jam texture and flavor by blocking the metabolic reprogramming of pectin-degrading bacteria includes the following steps: Step 1: Take fruits with a pectin structure of 55% methyl esterification, 6% acetylation, and 25% rhamnogalacturonic acid polysaccharide as raw materials, crush them, and obtain jam. Step 2: Add 0.22 w / w% sodium citrate, 0.11 w / w% calcium dihydrogen phosphate, and 0.3 w / w% low acyl gellan gum to the jam and mix. Then add citric acid dropwise to the jam system to stabilize the pH of the jam system to 4.1, and obtain the jam treatment solution. Step 3: The jam treatment liquid is aerated with oxygen through micropores using a micro-nano bubble generator until the oxidation-reduction potential (ORP) of the jam treatment liquid is +200 mV, thus obtaining pretreated jam. Step 4: Add 0.3g / kg (i.e., 0.3g plant-derived antibacterial complex per kilogram of pre-treated jam) of plant-derived antibacterial complex to the pre-treated jam, and then homogenize, sterilize, and fill the jam in sequence. After filling, the jam is cured in a gradient temperature environment in the dark to obtain the filled jam. The gradient temperature curing method is as follows: first, let it stand at 14℃ for 13 hours, and then raise the temperature to 23℃ and let it stand for 12 hours.

[0026] In step one, the crushing method is as follows: the jam raw materials are crushed at a speed of 1700 r / min and a temperature of 85 ℃ for 45 s to obtain jam; In step two, the mixing method is as follows: sodium citrate, calcium dihydrogen phosphate, and low-acyl gellan gum are added to the jam, and then reacted at 55 ℃ and 65 r / min for 15 min.

[0027] In step four, the plant-derived antibacterial complex comprises rosmarinic acid, chlorogenic acid, and nisin in a mass ratio of 1:5:2.

[0028] In step four, the homogenization conditions are: temperature 27℃ and pressure 12MPa.

[0029] In step four, the sterilization method is to treat at 85℃ for 25 seconds.

[0030] <Example 3> A method for inhibiting the deterioration of jam texture and flavor by blocking the metabolic reprogramming of pectin-degrading bacteria includes the following steps: Step 1: Take fruits with a pectin structure of 58% methyl esterification, 10% acetylation, and 28% rhamnogalacturonic acid polysaccharide as raw materials, crush them, and obtain jam. Step 2: Add 0.30 w / w% sodium citrate, 0.15 w / w% calcium dihydrogen phosphate, and 0.4 w / w% low acyl gellan gum to the jam and mix. Then add citric acid dropwise to the jam system to stabilize the pH of the jam system to 4.2 to obtain the jam treatment solution. Step 3: The jam treatment liquid is aerated with oxygen through micropores using a micro-nano bubble generator until the oxidation-reduction potential (ORP) of the jam treatment liquid is +250 mV, thus obtaining pretreated jam. Step 4: Add 0.5g / kg (i.e., 0.5g plant-derived antibacterial complex per kilogram of pre-treated jam) of plant-derived antibacterial complex to the pre-treated jam, and then perform homogenization, sterilization, and filling in sequence. After filling, perform gradient temperature curing in a dark environment to obtain the filled jam. The gradient temperature curing method is as follows: first, let it stand at 16℃ for 14 hours, and then raise the temperature to 24℃ and let it stand for 14 hours.

[0031] In step one, the crushing method is as follows: the jam raw materials are crushed at a speed of 2000 r / min and a temperature of 85 ℃ for 60 s to obtain jam; In step two, the mixing method is as follows: sodium citrate, calcium dihydrogen phosphate, and low-acyl gellan gum are added to the jam, and then reacted at 55 ℃ and 65 r / min for 15 min.

[0032] In step four, the plant-derived antibacterial complex includes rosmarinic acid, chlorogenic acid, and nisin in a mass ratio of 1:10:4.

[0033] In step four, the homogenization conditions are: temperature 30℃ and pressure 15MPa.

[0034] In step four, the sterilization method is to treat at 90℃ for 30 seconds.

[0035] <Example 4> The method of Example 2 was used to prepare the canned jam, except that step three was not performed in this example: Step 2: Add 0.22 w / w% sodium citrate, 0.11 w / w% calcium dihydrogen phosphate, and 0.3 w / w% low acyl gellan gum to the jam and mix. Then add citric acid dropwise to the jam system to stabilize the pH of the jam system to 4.1, and obtain the jam treatment solution. Next, a plant-derived antibacterial complex was added to the jam processing liquid, and step four (same as in Example 2) was performed to obtain the canned jam.

[0036] The remaining steps are the same as in Example 2.

[0037] <Example 5> The method of Example 2 was used to prepare the canned jam, except that no plant-derived antibacterial complex was added. That is, the operation in step four of this example is as follows: Step 4: Homogenize, sterilize, and fill the pre-treated jam in sequence. After filling, cure the jam in a light-proof environment with gradient temperature to obtain the filled jam. The gradient temperature curing method is as follows: first, let it stand at 14℃ for 13 hours, then raise the temperature to 23℃ and let it stand for 12 hours.

[0038] The remaining steps are the same as in Example 2.

[0039] In this invention, the jam processing liquid is treated with oxygen micropore aeration using a micro-nano bubble generator until the redox potential of the jam processing liquid reaches +150 to +250 mV. The specific operation is as follows: The jam processing liquid is placed in a sealed reaction tank equipped with a stirring device. The circulation pump is turned on, allowing the jam to enter the micro-nano bubble generator through a bypass pipe. Simultaneously, a high-purity oxygen cylinder (oxygen purity ≥99.9%) is used as the gas source, and the oxygen inlet pressure is controlled at 0.3–0.4 MPa. Inside the micro-nano bubble generator, the oxygen is cut into micro-nano-scale bubbles, which mix with the jam to form a gas-liquid two-phase flow. This mixture is then transported back to the reaction tank via pipeline and uniformly dispersed into the jam system through a microporous aerator with a bottom aperture of 0.2–5 μm. The system is circulated at room temperature (25±2℃) for 3–5 min, and the redox potential is continuously monitored using an online ORP electrode. The redox potential is maintained until the ORP value rises to and stabilizes at +150 to +250 mV. When the volume is within the range of mV, stop aeration, close the oxygen valve, and obtain pretreated jam.

[0040] <Comparative Example 1> The jam was prepared using the method described in Example 2, except for step one: In step one, the pectin structural gum was selected with a degree of methyl esterification of 48%, a degree of acetylation of 1%, and a degree of rhamnogalacturonic acid polysaccharide RG-I of 33%.

[0041] The remaining steps are the same as in Example 2.

[0042] <Comparative Example 2> The jam was prepared using the method of Example 2, except that step two was not performed: After obtaining the jam in step one, proceed directly to steps three and four.

[0043] The remaining steps are the same as in Example 2.

[0044] <Comparative Example 3> The jam was prepared using the method described in Example 2, except for step four: In step four, the filling process was not followed by gradient temperature curing, meaning that the filling process resulted in the finished jam.

[0045] The remaining steps are the same as in Example 2.

[0046] <Comparative Example 4> A method for preparing jam includes the following steps: Fruits with a pectin structural gum methyl esterification degree of 48%, an acetylation degree of 1%, and a rhamnogalacturonic acid polysaccharide RG-I content of 33% were used as raw materials and crushed (the crushing method was to crush the jam raw materials at a speed of 1700 r / min and a temperature of 85℃ for 45 s to obtain jam). The jam is then subjected to homogenization (homogenization conditions: temperature 25℃, pressure 12MPa), sterilization (sterilization method: treatment at 85℃ for 25s), and filling to obtain the filled jam.

[0047] Examples 1-5 and Comparative Examples 1-4 of this invention all use blueberries as raw materials, but this invention is not limited to using blueberries, and may also use strawberries or tomatoes.

[0048] <Experimental Characterization> The canned jams were prepared using the methods of Examples 1-5 and Comparative Examples 1-4. After being stored at 37°C for 3 months (to assess the storage stability of the jam at 25°C in a shorter time, this experiment selected 37°C as the accelerated storage temperature based on the principle of accelerated aging. According to the Arrhenius equation, storage under these conditions for 3 months can roughly simulate a shelf life of 6-9 months at room temperature), the following tests were conducted.

[0049] 1. Signs of Jam Deterioration (1) Rheological properties The rheological behavior of the jam was analyzed using a rotational rheometer (e.g., TA Discovery HR-20). Static rheological testing: At 25 °C, a 40 mm flat plate clamp with a 1 mm gap was used to perform shear rate scans (0.1–100 s⁻¹). -1 Record the trend of apparent viscosity with shear rate.

[0050] The results are as follows Figure 2 As shown, by Figure 2It can be seen that the canned jams obtained in Examples 1-3 and Comparative Example 4 all exhibit typical shear-thinning characteristics of polysaccharides, and the pectin entanglement network gradually breaks down and the apparent viscosity continues to decrease with increasing shear rate. Among them, the apparent viscosity peak values ​​of Examples 2, 3, and 1 decrease sequentially, and the peak values ​​of the three are much higher than those of Comparative Example 4. This is because the canned jam obtained in Example 2 has the highest retention of pectin long chains and the strongest degree of molecular entanglement, resulting in the highest viscosity peak value. The preparation methods of Examples 3 and 1 show a slight decrease in the pectin protection effect, but still maintain a stable intermolecular cross-linked structure, proving that the preparation methods of Examples 1-3 of this invention can effectively protect pectin molecules for a long time. Conversely, Comparative Example 4 lacked the four major processes of pectin conditioning, ORP microenvironment regulation, plant antibacterial addition, and segmented temperature-controlled curing. The pectin in the raw materials was easily degraded, and the preparation process was unprotected. The pectin was continuously degraded by enzymes produced by degrading bacteria into small oligosaccharides, and the molecular entanglement effect was greatly weakened. The apparent viscosity peak was the lowest in the entire group, and water separation and collapse were prone to occur. This proves that the multi-process synergy of the present invention can completely preserve long-chain pectin and improve the rheological stability of jam. The absence of any core process will cause pectin degradation and a significant decrease in system viscosity.

[0051] (2) Moisture content and moisture distribution The moisture content of the jam was determined using the direct drying method. The distribution of moisture in the jam was determined using a low-field nuclear magnetic resonance (Niumag MicroMR20-025V) analyzer. Approximately 2 g of sample was accurately weighed and placed in an NMR tube. Transverse relaxation time (T2) data were acquired using a Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence. Inversion fitting was performed using MultiExpInvInversion software, and the T2 spectrum was divided into three components: T... 21 (Bound water, 0.1~10 ms), T 22 (For slow-moving water, 10~100 ms), T 23 (Free water, 100–1000 ms), calculate the peak area ratio of each component to characterize the relative content of water in different states. Results are presented by... Figure 3 As shown; Depend on Figure 3It can be seen that the position of the signal peak corresponds to the moisture state, and the peak area corresponds to the moisture content. The small peak on the left represents bound water that is not easily flowable, and the main peak on the right represents water that is not easily separated. Free water has almost no obvious peak. The main peak signal strength of the canned jams obtained in Examples 2, 3, and 1 is much higher than that in Comparative Example 4. Among them, the main peak value of Example 3 is the highest, followed by Example 2, and Example 1 is slightly lower. The three complete processes form a dense network structure, which can bind a large number of water molecules through hydrogen bonds and ionic bonds, and stably fix water in the pores of the polysaccharide network. This significantly increases the proportion of bound water and water that is not easily flowable, reduces the generation of free water that is prone to separation and deterioration, and the parameters of this invention can achieve excellent moisture locking effect in both the upper and lower limits. Conversely, in the jam obtained in Comparative Example 4, a large number of pectin long chains were degraded and broken, the intermolecular cross-linking network was loose and damaged, and the ability to bind water molecules was significantly weakened. The main peak value was the lowest among the four groups, and more water was converted into easily flowing free water. During storage, it was more prone to problems such as water separation, stratification, and deterioration of texture. This proves that the entire process of the present invention can enhance the water binding ability of the system by maintaining the complete pectin structure, optimize the water distribution of jam, and synergistically improve storage stability.

[0052] (3) Particle size distribution The particle size distribution of the canned jam was determined using a laser particle size analyzer (such as a Malvern Mastersizer 3000). Deionized water was used as the dispersion medium, with the sample refractive index set to 1.52, the dispersant refractive index to 1.33, and the shading ratio controlled within the range of 10%–15%. The volume average particle size (D[4,3]), surface area average particle size (D[3,2]), and characteristic particle sizes (d(0.1), d(0.5), d(0.9)) were measured to analyze the uniformity and variation of the particle size distribution.

[0053] The test results of the canned jam prepared in Example 2 are as follows: Figure 4 As shown, the results indicate the particle size distribution Figure 3 The curves of the parallel samples almost completely overlapped, and the particle size characteristic parameters such as span and uniformity were stable, indicating good repeatability. The sample particle size showed a bimodal distribution, with the main peak concentrated around 100 μm, representing intact pulp particles, and the secondary peaks corresponding to a small number of broken fragments. The average particle size of sample D[4,3] was 153.461 μm, the median particle size of d(0.5) was 114.321 μm, the particle size span was only 2.481, and the uniformity was 0.752. The particle size distribution was concentrated and uniform, indicating that the complete process of this invention, through low-speed conditioning and fusion at 55 ℃ and precise homogenization, fully crosslinks and integrates sodium citrate, calcium dihydrogen phosphate, low-acyl gellan gum, and pectin to form composite particles with stable size and complete structure, and a low proportion of fine and degradable microparticles. The above results further corroborate that the synergistic process of this invention can maintain the relatively complete and uniform intermolecular crosslinking structure of pectin, and improve the storage stability of jam from the micro-particle level.

[0054] (4) Volatile flavor compounds (GC-MS) Volatile flavor components in jam were determined using gas chromatography-mass spectrometry (GAS FlavourSpec®). Headspace injection conditions: 2 g of canned jam sample was weighed and placed in a 20 mL headspace vial, incubated at 50 °C for 15 min, and injected at a volume of 500 μL. Chromatographic conditions: An FS-SE-54-CB column (15 m × 0.53 mm) was used at 60 °C, with high-purity oxygen as the carrier gas. The flow program was 0–2 min: 2 mL / min, 2–20 min: 2–150 mL / min. MS conditions: Temperature was 45 °C, and high-purity oxygen was used as the drift gas. Qualitative and quantitative analysis of volatile flavor compounds was performed by comparison with a GC-MS database. The results are shown in Table 1.

[0055] Table 1. GC-MS determination of volatile compounds (μg / kg) of off-odors in jam after 90 days of storage. Example 1 21.5 18.2 23.7 16.4 26.9 21.7 128.4 Example 2 15.3 12.1 17.5 11.8 19.2 20.8 96.7 Example 3 24.1 20.5 25.3 19.2 28.4 24.6 142.1 Example 4 52.7 41.3 54.9 37.5 49.1 38.8 274.3 Example 5 47.2 36.9 48.6 33.1 43.5 32.6 241.9 Comparative Example 1 76.4 62.8 79.1 54.2 68.3 65.4 406.2 Comparative Example 2 85.7 71.3 87.5 60.9 75.2 82.9 463.5 Comparative Example 3 65.2 53.7 67.8 46.3 59.6 60.2 352.8 Comparative Example 4 132.6 107.9 141.3 98.7 115.4 93.5 689.4 Table 1 shows that isoamyl alcohol and ethyl acetate are fermentation metabolites, 2-heptanone has a pear-like fruity aroma, butyric acid and hexanoic acid are typical rancid odors, and furfural has a special odor similar to benzaldehyde. The total content of rancidity-related characteristic substances (butyric acid, hexanoic acid, 2-heptanone, furfural) in the canned jams obtained in Examples 1-3 was generally at its lowest level, while the fermentation byproducts (isoamyl alcohol and ethyl acetate) also remained at a low level, indicating that the overall microbial metabolic activity of the system was inhibited. Furthermore, the total amount of off-odors in the jams obtained after omitting any single step in Examples 4 and 5 increased significantly. The lack of any of the pectin conditioning, ORP regulation, or plant antibacterial modules resulted in a large accumulation of off-odor substances. Conversely, the total amount of off-odor in the jams obtained from Comparative Examples 1 to 4 was generally higher than that in all examples lacking certain processes. Among them, Comparative Example 2 had a higher off-odor than Comparative Examples 1 and 3 due to pH imbalance and lack of pectin structure protection process. Comparative Example 3 only lacked gradient curing, resulting in a lower total off-odor than Comparative Example 1, which had raw material defects. Comparative Example 4 had multiple protection processes missing, including raw material screening, pH control, ORP adjustment, antibacterial agent addition, and gradient curing. As a result, the system had the highest proliferation and metabolic activity of spoilage microorganisms. The continuous secretion of pectinase led to a large amount of depolymerization of pectin long chains, and various deterioration metabolites accumulated to the highest level in the entire group in the final product.

[0056] (5) Microbial diversity analysis and screening of dominant bacterial genera DNA was extracted from samples using the QIAamp DNA Stool Mini kit. PCR amplification of the V3-V4 hypervariable region was performed using primers 338F and 806R. 16S rRNA sequencing was conducted on the Illumina MiSeq platform to analyze the relative abundance of pectin degradation-related and synergistic spoilage microorganisms. The results are shown in Table 2. Table 2. Relative abundance (%) of synergistic spoilage microorganisms after 90 days of storage Example 1 1.85 0.64 1.03 0.60 4.12 Example 2 1.02 0.31 0.68 0.36 2.37 Example 3 2.14 0.76 1.17 0.78 4.85 Example 4 5.28 1.84 2.71 1.46 11.29 Example 5 4.51 1.53 2.36 1.33 9.73 Comparative Example 1 8.63 2.97 4.82 2.09 18.51 Comparative Example 2 10.47 3.62 5.91 2.76 22.76 Comparative Example 3 7.15 2.41 3.96 1.81 15.33 Comparative Example 4 14.82 5.13 8.47 3.06 31.48 The total abundance of spoilage bacteria in Examples 1-3 was significantly lower than that in other examples and comparative examples, proving that the jam obtained by the process of this invention can stably inhibit the proliferation of various pectin-degrading spoilage bacteria. In Examples 4 and 5, the abundance of bacteria increased simultaneously after the removal of a single core process. The lack of carbon source buffering effect from the pectin system, micro-redox stress, and targeted antibacterial components all led to a large accumulation of spoilage bacteria. Furthermore, the overall bacterial abundance in each comparative example was higher than that in Examples 4 and 5. Comparative Example 2, due to pH fluctuations stimulating bacterial metabolism recovery, had a higher total abundance than Comparative Example 1, which had raw material defects. Comparative Example 3, lacking only gradient temperature curing, had a lower total bacterial abundance than Comparative Examples 1 and 2. Comparative Example 4, without any inhibitory measures, had the highest total abundance of the four types of spoilage bacteria in the entire group.

[0057] 2. Storage stability based on pH and redox potential (1) pH

[0058] Take 1g of jam sample (after 3 months of storage in a bottle) and insert a calibrated high-precision laboratory pH meter directly into the jam matrix. Record the pH value of the system after the reading stabilizes. Each sample is measured in triplicate, and the average value is calculated.

[0059] (2) ORP (oxidation-reduction potential) Before testing, the ORP electrode was calibrated using a standard redox buffer solution. Under constant temperature of 25 ℃, the clean and passivated ORP composite electrode was completely immersed in the homogenized jam sample. After the value stabilized, the redox potential value (mV) of the system was read. Each parallel measurement was performed 3 times.

[0060] The pH and ORP results are shown in Table 3. Table 3. Jam pH, ORP Example 1 4.12 186 Example 2 4.07 214 Example 3 4.18 162 Example 4 4.1 87 Example 5 4.09 192 Comparative Example 1 4.14 179 Comparative Example 2 3.58 126 Comparative Example 3 4.11 203 Comparative Example 4 3.62 94 The pH and ORP of the jams obtained in Examples 1-3 all fell within the standard control range, and the microenvironments of all three groups met the conditions for inhibiting the metabolic reprogramming of pectin-degrading bacteria. Example 4 involved anaerobic aeration, indicating that changes in the redox environment of the system were closely related to the abundance of spoilage bacteria. Example 5 had qualified microenvironmental indicators but lacked antibacterial components. Comparative Example 1 only lacked specific pectin structural parameters in its raw materials, and its microenvironmental parameters met the standards. Comparative Example 2 lacked an endogenous buffer system and did not control pH and ORP. Comparative Example 3 had a qualified processing microenvironment but lacked gradient temperature curing. Comparative Example 4 lost its pH buffering and ORP control capabilities, with the most severe deviations in both indicators. The ORP control of this invention manifests as a physical regulation of dissolved oxygen and redox balance in the system, forming a multiple effect together with pH buffering and antibacterial agents.

[0061] 3. Test the pectin in the canned jam. Take 5 g of canned jam (also stored for 3 months), add 250 mL of deionized water, allow it to swell fully, adjust the pH to 2.5 with citric acid, stir well, and heat in a water bath at 80℃ for 2 h. Repeat the extraction once more with the residue, filter, combine the supernatants, and rotary evaporate at 55℃ to a volume of approximately 150 mL. After cooling to room temperature, add 600 mL of anhydrous ethanol at a ratio of 1:4 (v / v) while stirring, and precipitate for 12 h to obtain a flocculent precipitate. Centrifuge the pectin polysaccharide extract at 5000 r / min for 40 min, retain the flocculent precipitate, place it in a dialysis bag (molecular weight cutoff of 3500 Da), and immerse it in deionized water for complete dialysis for 72 h. Finally, concentrate by rotary evaporation at 55℃, freeze-dry to obtain the pectin sample, and store for later use. The pectin will then be analyzed as follows: (1) Molecular weight The molecular weight of pectin in packaged jams was determined using high-resolution size exclusion chromatography combined with an 18-angle laser scattering system (HPSEC-MALLS-RI) with NaCl solution as the eluent. The experimental method was as follows: 5.0 mg of pectin sample was accurately weighed and dissolved in 5 mL of 0.1 mM NaCl solution. The solution was filtered through a 0.22 μm MF-Millipore® filter membrane and manually injected 200 μL through a quantitative loop at a flow rate of 0.5 mL / min. The mobile phase was 0.1 mM NaCl solution, and the refractive index increment (dn / dc) was 0.135 mL / g. The weight-average molecular weight (Mw), number-average molecular weight (Mn), and polydispersity index (Mw / Mn) of pectin were calculated and analyzed using ASTRA 5.3.4 software (Wyatt Technology, Santa Barbara, CA, USA).

[0062] The results are as follows Figure 5As shown in the HPSEC size exclusion chromatography curve, the molecular weight distribution curve of pectin is plotted with the vertical axis representing logarithmic molecular mass and the horizontal axis representing elution time. A higher molecular weight of the elution peak indicates more complete retention of the pectin long chains and a lower degree of degradation. HPSEC results show that the molecular weight of the pectin main peak in Examples 1-3 is significantly higher than that in the comparative examples, with Example 2 having the highest molecular weight, indicating that its process parameter combination is most effective in protecting the integrity of the pectin long chains. In contrast, Example 5 lacks the plant-derived antibacterial complex targeting antibacterial activity. During storage, pectin-degrading bacteria continuously secrete degrading enzymes, resulting in a significant reduction in high-molecular-weight pectin components and an increase in the proportion of low-molecular-weight oligosaccharides, leading to a substantial decrease in the molecular weight of the main peak. Comparative Example 4 lacks all protection processes, resulting in the extensive decomposition of the pectin long chains, almost complete disappearance of high-molecular-weight components, and a significant enhancement of the low-molecular-weight fragment signal. The molecular weight of the main peak is the lowest among the five groups, and the intensity of the small-molecule elution peak in the latter half of the spectrum is significantly higher than that of the other samples, indicating the accumulation of a large amount of pectin-degrading oligosaccharides in the system. This confirms that without multiple protection measures, pectin undergoes severe enzymatic degradation, exacerbating the deterioration of the jam's texture and flavor. The above results demonstrate that the synergistic process of this invention can stably maintain the complete structure of pectin polymers. The absence of one or more core processes will cause pectin to depolymerize to varying degrees, thereby damaging the substrate barrier that inhibits the reprogramming of microbial metabolism.

[0063] (2) Thermal stability The thermodynamic properties of the jam were determined using a differential scanning calorimeter (TA Q2000). 10–15 mg of pectin sample was accurately weighed and sealed in an aluminum crucible, with an empty crucible used as a reference. The heating program was set to increase the temperature from -40 °C to 80 °C at a rate of 10 °C / min under oxygen atmosphere protection (flow rate of 50 mL / min). The heat flow change at the melting peak was recorded, and the onset temperature, peak temperature, termination temperature, and enthalpy change (ΔH) were analyzed to evaluate the thermal stability and moisture state of the system.

[0064] The results are as follows Figure 6As shown in Figure (a), the TG-DTG curve of the pectin sample in Example 2 is shown, and Figure (b) is the TG-DTG curve of the pectin sample in Comparative Example 4. Both curves show three typical stages of thermal weight loss. In the first stage, from 50 to 120 °C, the system's free and bound water evaporates and loses weight, with the weight loss being similar. In the second stage, from 200 to 350 °C, the main weight loss range is the thermal decomposition of the pectin polysaccharide backbone and small molecule sugars in the pulp. The maximum thermal decomposition peak temperature of Example 2, 257.22 °C, is close to that of Comparative Example 4, 269.62 °C. However, the remaining mass of Example 2 in this range (53.32%) is significantly higher than that of Comparative Example 4 (37.51%), and the char residue at 800 °C (24.19%) is much higher than that of Comparative Example 4 (15.81%). In summary, Example 2 has a higher cross-linking density of pectin molecules, a more gradual thermal decomposition, and a larger amount of char residue at high temperatures, resulting in better overall thermal stability than Comparative Example 4. The complete process demonstrates that the dense pectin cross-linked network increases the activation energy required for molecular chain breakage, thus delaying pectin thermal degradation. In the third stage (350-800℃), pectin fragments undergo deep carbonization and continuous weight loss. At the final temperature of 800℃, the char residue rate of Example 2 (24.19%) is significantly higher than that of Comparative Example 4 (15.81%), and the DTG peak intensity is also lower, proving that its pectin molecules have a higher degree of cross-linking and a more gradual thermal decomposition rate. Comparative Example 4 shows significant degradation of long pectin chains and damage to the cross-linked structure, making the polysaccharide molecular chains more susceptible to thermal breakage. It exhibits a lower thermal decomposition initiation temperature, a faster weight loss rate, and a lower amount of high-temperature char residue, resulting in significantly inferior thermal stability compared to the complete process sample. This confirms that the pectin network formed by this invention has a higher molecular cross-linking density, a more gradual thermal decomposition, and a larger amount of high-temperature char residue, resulting in superior overall thermal stability. It effectively reduces pectin thermal degradation during the high-temperature sterilization process and lowers the risk of textural deterioration during storage.

[0065] (3) Monosaccharide composition and content, degree of methyl esterification, degree of acetylation Monosaccharide Composition and Content: The neutral sugar composition and content of pectin in packaged jams were determined using high-performance anion chromatography (HPLC). The experimental method was as follows: 10.0 mg of pectin sample was accurately weighed and added to 4.0 mL of 2.0 mM TFA (trifluoroacetic acid). The sample was hydrolyzed at 110 °C for 1.5 h, dried under nitrogen, and brought to a final volume of 10 mL with distilled water. The sample was then filtered through a 0.45 μm MF-Millipore® membrane under the following chromatographic conditions: the system was equilibrated with 100 mM NaOH for 5 min, followed by equilibration with 4.0 mM NaOH for 5 min. Separation and elution were performed using a CarboPac PA20 column (Dionex) with 4.0 mM NaOH as the eluent. The temperature was set at 30 °C, the flow rate at 0.5 mL, and the injection volume at 10.0 μL. A standard curve was constructed using a neutral sugar standard mixture (D-galacturonic acid GalA, rhamnose Rha, arabinose Ara, galactose Gal, glucose Glu, xylose Xyl, and fuc) with a concentration gradient of 0.01–5.0 mg / L. Actual samples were hydrolyzed and injected, and quantification was performed by substituting the peak areas into the corresponding monosaccharide standard curves (concentration-peak area linear regression equation). The content (mol%) of each monosaccharide in the pectin sample was calculated. After obtaining the content of each monosaccharide, the pectin structural parameters were calculated using the following formulas: HG domain % = (GalA content - Rha content) / (Rha content + Ara content + Gal content + Xyl content + Fuc content); RG-I domain % = Rha content / GalA content.

[0066] Degree of methyl esterification: Weigh 20 mg of pectin sample and add 8 mL of distilled water. Sonicate for 10 min, add 3.2 mL of 2M NaOH, and place in a constant temperature shaking incubator at 20℃ for 1 h, shaking every 10 min. Then add 3.2 mL of 2M HCl and neutralize at 25℃ for 15 min. Finally, bring the volume to 25 mL with phosphate buffer. Add 1 mL of sample or standard and 1 mL of ethanol oxidase to each test tube, vortex thoroughly, and incubate at 25℃ for 15 min. Then add 2 mL of pentanedione solution to each sample, vortex, and incubate at 58℃ for 15 min. After cooling, vortex and measure the absorbance at 412 nm. Degree of methyl esterification (DM) is expressed as the molar ratio of methanol to anhydrous galacturonic acid.

[0067] Degree of acetylation: Dissolve 10 mg of pectin sample in 2 mL of deionized water and heat at 90 °C for 20 min to inactivate endogenous enzymes. To saponify ester bonds, add 500 μL of 2 M NaOH to each sample and incubate in a water bath at 25 °C for 1 h. Then add 500 μL of 2 M HCl to pause the saponification reaction and incubate in a water bath at 25 °C for 15 min. Finally, use the K-ACETRM acetic acid assay kit to determine the acetylation degree of pectin.

[0068] The results of the determination of monosaccharide composition and content, degree of methyl esterification, and degree of acetylation are shown in Table 4. Table 4. Pectin molecular structure indices before jam storage Example 1 54.2 6.3 24.7 Example 2 55.8 7.1 22.3 Example 3 53.1 5.8 26.1 Example 4 51.3 5.1 28.4 Example 5 53.7 6.5 25.2 Comparative Example 1 47.3 2.1 36.8 Comparative Example 2 45.1 3.2 33.9 Comparative Example 3 54.6 6.8 23.8 Comparative Example 4 42.8 2.7 39.5 The core indicators for pectin structure protection should be the retention rates of methyl esterification and acetylation. The results are shown in Table 5. Example 2 showed a higher degree of methyl esterification, a moderate degree of acetylation, and the lowest RG-I%. Example 1 had moderate structural indicators, while Example 3 had a slightly higher RG-I% than the previous two groups. In step two, the pectin microstructure conditioning and fusion system used sodium citrate as a pH buffer and for chelating metal ions. Calcium dihydrogen phosphate provided calcium ions to crosslink the pectin carboxyl groups. Low-acyl gellan gum interspersed the pectin network, physically shielding the enzyme cleavage sites on the pectin molecular chain, especially the galacturonic acid bonds in the HG backbone region, reducing the accessibility of pectinase to the pectin backbone. Therefore, the initial pectin structure in the jams obtained in Examples 1-3 was stable. Example 4 only lacked oxygen aeration, resulting in only slight degradation of the pectin structure during processing. However, the unbalanced redox environment during storage continuously induced microbial enzyme production to decompose the pectin. Example 5 only lacked antibacterial components, resulting in an intact initial pectin structure. However, during storage, spoilage bacteria continuously secreted pectinase, slowly destroying the pectin backbone. Conversely, in Comparative Example 1, the raw material itself had low pectin methyl esterification and acetylation, and excessively high RG-I%, indicating a large number of microorganisms that preferred carbon sources. Comparative Example 2 had no pH buffer, no calcium salts, and no gellan gum, resulting in a higher degree of structural deterioration than Comparative Example 1. Comparative Example 3 omitted only the step-temperature curing after filling, and the initial pectin structure was intact, but the microbial community did not undergo metabolic reprogramming, and the pectin continued to decompose during long-term storage. In Comparative Example 4, the raw material pectin structure was not screened and there was no structural protection throughout the processing. After the HG main chain was degraded, the proportion of RG-I side chains increased relatively.

[0069] The above results confirm that the molecular structure of pectin is the fundamental basis for determining the storage quality of jam. High DM, moderate acetylation, and low RG-I% pectin can reduce the carbon source supply for pectin-degrading bacteria from the substrate source. Combined with the whole-chain synergy of conditioning and gum protection, microenvironment ORP regulation, targeted antibacterial action, and post-filling microbial community domestication, a dual barrier of "pectin molecular structure protection and microbial metabolic pathway blocking" is constructed. If any regulatory process is missing, either pectin molecules will degrade prematurely, producing a large amount of oligosaccharide substrates that can induce metabolic reprogramming, or the continuous secretion of pectin lyase and polygalacturonase by Bacillus, mold, yeast, and other microorganisms will be unable to be inhibited. These two enzymes work together to continuously depolymerize pectin, simultaneously accumulating galacturonic acid, alcohols, and acidic off-flavor metabolites, ultimately resulting in textural collapse and flavor deterioration during jam storage. The above results show that there is a significant synergistic effect among the various processes of this invention. The synergistic application of multiple barriers, such as raw material screening, pH / ORP regulation, antibacterial agent compounding, and gradient maintenance, can more effectively maintain the integrity of pectin structure and inhibit the metabolism of putrefactive microorganisms.

[0070] (4) Molecular force dynamics simulation Molecular dynamics simulations were performed using Gromacs 2021 software. A water-filled chamber was used, with the water model being tip3p. Na and Cl ions were used to balance the system charge, ensuring the system was uncharged. Before the simulation, energy minimization was performed to eliminate unreasonable contacts in the initial conformation. Next, a 100ps NVT pre-equilibrium simulation was executed. The NVT ensemble maintains constant particle number (N), volume (V), and temperature (T) during the simulation to raise the temperature to the target simulation temperature. Following this, a 100ps NPT pre-equilibrium simulation was performed. The NPT ensemble maintains constant particle number (N), pressure (P), and temperature (T) during the simulation to adjust the system density to the equilibrium value at the target pressure. After the system relaxed, the final simulation was performed. The final simulation used the leapfrog algorithm to integrate Newton's equations of motion, with an integration time step of 0.002ps, 50,000,000 integration steps, and a total simulation time of 100.0ns. The final simulation used the V-rescale temperature coupling method at a temperature of 298.15 K. The final simulation also used the Parrinello-Rahman pressure coupling method at a pressure of 1.0 bar. Due to the use of the cutoff distance method, long-range electrostatic interactions were corrected using the PME method. Dispersion correction was also used for long-range van der Waals interactions due to the use of the cutoff distance method. Periodic boundary conditions were applied in all three directions. Gromacs was used for data analysis after the simulation. PyMOL (http: / / www.pymol.org / ) was used for molecular conformation visualization. The resulting graphs were plotted using the Python plotting software Matplotlib.

[0071] A schematic diagram of the intermolecular interactions of pectin molecules in the jam system prepared in Example 2 of this invention is shown below. Figure 7 As shown, blue-green represents unbroken pectin molecules; pink represents broken pectin molecule fragments; green dashed lines represent hydrogen bonding; and yellow dashed lines represent hydrophobic interactions. Figure 7 This indicates that the main interactions between pectin molecules are hydrogen bonding and hydrophobic interactions.

[0072] The change in the number of intermolecular hydrogen bonds in pectin in Example 2 over time was further calculated, such as... Figure 8 As shown, the number of hydrogen bonds was approximately 91 at the start of the simulation and approximately 230 at the end of the simulation. The number of hydrogen bonds increased with the increase of simulation time, indicating that the interaction may be enhanced.

[0073] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A method for inhibiting the deterioration of the texture and flavor of jam by blocking the metabolic reprogramming of pectin-degrading bacteria, characterized in that, Includes the following steps: Step 1: Take fruits with a pectin structure of 52%–58% methyl esterification, 3%–10% acetylation, and <30% rhamnogalacturonic acid polysaccharide as raw materials, crush them, and obtain jam. Step 2: Add 0.15-0.30 w / w% sodium citrate, 0.08-0.15 w / w% calcium dihydrogen phosphate, and 0.2-0.4 w / w% low-acyl gellan gum to the jam and mix. Then, add citric acid dropwise to the jam system to stabilize the pH of the jam system to 4.0-4.2 to obtain the jam treatment solution. Step 3: The jam treatment liquid is aerated with oxygen through micropores using a micro-nano bubble generator until the oxidation-reduction potential of the jam treatment liquid is +150 to +250 mV, thus obtaining pretreated jam. Step 4: Add 0.1-0.5 g / kg of plant-derived antibacterial complex to the pretreated jam, and then homogenize, sterilize, and fill the jam in sequence. After filling, the jam is cured in a gradient temperature environment in the dark to obtain the filled jam. The gradient temperature curing method is as follows: first, let it stand at 12-16℃ for 12-14 h, and then raise the temperature to 22-24℃ and let it stand for 10-14 h.

2. The method for inhibiting the deterioration of jam texture and flavor by blocking the metabolic reprogramming of pectin-degrading bacteria as described in claim 1, characterized in that, In step one, the crushing method is as follows: crush the jam raw materials at a speed of 1500~2000 r / min and a temperature of 85 ℃ for 30~60 s to obtain jam.

3. The method for inhibiting the deterioration of jam texture and flavor by blocking the metabolic reprogramming of pectin-degrading bacteria as described in claim 2, characterized in that, In step two, the mixing method is as follows: sodium citrate, calcium dihydrogen phosphate, and low-acyl gellan gum are added to the jam, and then reacted at 55 ℃ and 65 r / min for 15 min.

4. The method for inhibiting the deterioration of jam texture and flavor by blocking the metabolic reprogramming of pectin-degrading bacteria as described in claim 3, characterized in that, In step four, the plant-derived antibacterial complex includes rosmarinic acid, chlorogenic acid, and nisin in a mass ratio of 1:1.3~10:0.5~4.

5. The method for inhibiting the deterioration of jam texture and flavor by blocking the metabolic reprogramming of pectin-degrading bacteria as described in claim 4, characterized in that, In step four, the homogenization conditions are: temperature 25~30℃ and pressure 10~15MPa.

6. The method for inhibiting the deterioration of jam texture and flavor by blocking the metabolic reprogramming of pectin-degrading bacteria as described in claim 4, characterized in that, In step four, the sterilization method is to treat at 80-90℃ for 20-30 seconds.

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