A method for improving the gel properties of a low-sugar jam using high molecular weight citrus pectin and a low-sugar jam

Abstract

This invention discloses a method for improving the gelling properties of low-sugar jam using high molecular weight citrus pectin, and the resulting low-sugar jam, belonging to the field of food processing technology. While existing steam explosion technology can increase pectin extraction rate, it reduces the molecular weight of pectin from 318.41 kDa to 48.26 kDa, deteriorating the jam's gelling properties. This invention first extracts high molecular weight pectin from citrus peel pomace using dry ice in-situ explosion technology—dry ice sublimates in a sealed container at room temperature, generating a volume expansion effect, and performing a purely physical explosion from within the cell walls, completely avoiding the damage to the covalent bonds of pectin caused by high temperatures. The resulting pectin has a molecular weight ≥280 kDa and a galacturonic acid content ≥86%. This pectin is then directly used in the preparation of low-sugar jam, utilizing its long molecular chain characteristics to form a denser three-dimensional network structure under calcium ion crosslinking. Experiments show that the jam of this invention has a 150% higher hardness than that using conventional low molecular weight pectin, and a water retention rate of 98.8% at 4℃, achieving high-value utilization of citrus peel pomace and a significant improvement in the quality of low-sugar jam.

Description

Technical Field

[0001] This application relates to the field of food processing technology, and in particular to a method for improving the gelling properties of low-sugar jam using high molecular weight citrus pectin, and the low-sugar jam itself. Background Technology

[0002] Jam is a popular food, enjoyed directly or used as an ingredient in frozen desserts and baked goods. Traditional jam production involves heating and concentration or adding exogenous substances, utilizing the interaction between high-methoxylated pectin (esterification degree ≥50%) and high-concentration sucrose (typically 50%–60% of the total concentration) to form a gel. High-concentration sucrose reduces the water activity of the gel system, weakens hydration between pectin and water molecules, and promotes hydrophobic interactions between pectin molecules; the acidic environment also protonates free carboxyl groups, promoting hydrogen bond formation. However, the high sucrose concentration results in a cloyingly sweet taste and high calorie content in jam, which is detrimental to health with long-term consumption.

[0003] With the increasing consumer demand for low-sugar and low-calorie foods, low-sugar jams have experienced rapid development. Low-sugar jams are primarily achieved by reducing the amount of sucrose added; however, reducing sucrose leads to decreased jam consistency, insufficient gel strength, and a shortened shelf life. Currently, low-sugar jams mainly rely on low-methoxyl pectin (esterification degree <50%) to form a gel in the presence of calcium ions. However, low-ester pectin generally has weaker gelling ability than high-ester pectin, resulting in gels with lower hardness and modulus. Furthermore, low-sugar jams commonly experience water separation (dehydration shrinkage) during storage, generally limiting their shelf life to no more than 6 months. Existing research indicates that water separation in jams is closely related to the gel strength of pectin—water separation occurs when gel strength decreases.

[0004] The molecular weight of pectin is one of the key factors determining its gelling properties. Higher molecular weight pectin molecules have longer chains, enabling them to form a denser three-dimensional network structure in the gel system, resulting in stronger gel strength and water-holding capacity. Studies have shown that the molecular weight of pectin is closely related to its rheological properties, gel-forming ability, solubility, and emulsifying properties. However, existing commercial pectins are typically subjected to harsh conditions such as strong acid and high temperature treatment or physical field assistance during extraction, leading to a significant decrease in molecular weight.

[0005] Yang Xiaohan et al. conducted a systematic study on the effects of steam explosion pretreatment on the structure and emulsification stability of citrus peel pectin (Food Industry Technology, 2026, 47(7): 114-121). The study found that without pretreatment, the extraction rate of citrus peel pectin was 7.59% and the molecular weight was 318.41 kDa; after steam explosion treatment at 0.3 MPa, the extraction rate increased significantly to 21.17%, but the molecular weight decreased to 114.22 kDa, a decrease of 64.1%; after steam explosion treatment at 0.45 MPa, the molecular weight further decreased to 48.26 kDa, a decrease of as much as 84.8%.

[0006] While this study confirms that steam explosion can improve pectin extraction rate, it also clearly reveals the inherent flaw of steam explosion technology in sacrificing pectin molecular weight for increased extraction rate. The reason steam explosion severely damages pectin molecular weight is as follows: the first stage of steam explosion involves placing the material in high-temperature, high-pressure (usually above 100°C) saturated steam for several minutes. Pectin molecules are exposed to this high-temperature environment, causing the glycosidic bonds in the pectin backbone to break under thermal drive. Simultaneously, the high-temperature steam comes into contact with organic acids in the plant cell walls, creating a weakly acidic environment that triggers acid hydrolysis of the glycosidic bonds in the pectin molecules. Furthermore, the depolymerization of pectin during heat treatment can also be achieved through β-elimination reactions, which break the glycosidic bonds between galacturonic acid residues in the pectin backbone, a process significantly accelerated under high-temperature conditions. Therefore, the damage to pectin molecular weight caused by steam explosion is the result of the superposition of three chemical degradation mechanisms: high temperature, acid hydrolysis, and β-elimination reactions—these mechanisms directly attack the covalent bonds in the pectin molecular backbone, causing irreversible molecular chain breakage. Studies have clearly shown that as the steam explosion pressure increases, the proportion of homogalacturonic acid (HG) in pectin decreases from 82.5% to 62.7%, and the molecular weight decreases from 106 kDa to 43 kDa.

[0007] Regarding patented technologies, CN117088996A discloses a high-gelling-degree low-ester pectin and its preparation method, which prepares low-ester pectin through acid extraction with a gelling degree of 120-150. However, this technology focuses on controlling the degree of esterification rather than maintaining the molecular weight. CN114514992B discloses a method for making low-sugar jam from citrus peel pomace, which uses steam flash explosion treatment of citrus peel pomace to produce low-sugar jam. However, this technology also faces the problem of steam explosion damaging the molecular weight of pectin, and does not recognize the decisive influence of pectin molecular weight on the gelling properties of low-sugar jam.

[0008] In summary, the following unresolved technical problems exist in the existing technology: Firstly, low-sugar jams generally suffer from insufficient gel strength and water separation during storage due to a lack of adequate high-molecular-weight pectin support. Existing low-sugar jams mainly rely on low-methoxyl pectin to form a gel in the presence of calcium ions, but low-ester pectin has limited gelling ability, and commercial pectin has a low molecular weight due to degradation during the extraction process, making it difficult to meet the high-molecular-weight pectin requirements of low-sugar jams.

[0009] Secondly, separating pectin extraction from jam preparation adds to the process steps. Under the current model, pectin production and jam preparation are two independent processes. Pectin needs to be extracted, dried, stored, transported, and then reconstituted into the jam system. This process inevitably causes further degradation of molecular weight and increases the number of process steps and costs. Summary of the Invention

[0010] The purpose of this invention is to overcome the technical defects of existing low-sugar jams, such as insufficient gel strength and easy water separation during storage, and to provide a method for improving the gel performance of low-sugar jams using high molecular weight citrus pectin, as well as a low-sugar jam itself. This invention extracts high molecular weight pectin from citrus peel pomace using dry ice in-situ explosion technology, and directly uses this pectin in the preparation of low-sugar jams. Its high molecular weight enhances the gel network structure, significantly improving the jam's gel strength and water-holding capacity, while simultaneously achieving high-value utilization of citrus peel pomace byproducts.

[0011] A method for improving the gelling properties of low-sugar jams using high molecular weight citrus pectin includes the following steps: Step 1: Preparation of high molecular weight citrus pectin (1) Raw material pretreatment: Remove visible impurities from fresh citrus peel and pulp, rinse thoroughly with clean water, and cut into granules with a particle size of 0.5~2 cm. Blanch the cut peel and pulp granules in hot water at 85~95℃ for 3~8 min to deactivate endogenous pectinase activity. After blanching, quickly cool to room temperature and drain the surface moisture.

[0012] (2) Dry ice in-situ explosion pretreatment: Place the pretreated skin residue in a sealed pressure-resistant container, add 20%~50% dry ice (solid carbon dioxide) of the skin residue mass, seal and let stand at 15~30℃ for 30~90 min, then quickly open the container to release pressure, and use the volume expansion effect generated by the sublimation of dry ice to burst the cell wall from the inside, so that the pectin-cellulose entanglement network produces microcracks.

[0013] The mechanism of dry ice in-situ explosion and its essential difference from steam explosion: During the sublimation process of dry ice at room temperature and pressure, its volume expands significantly. When dry ice and pomace are sealed together in a pressure-resistant container, the carbon dioxide gas produced by the gradual sublimation of the dry ice causes the pressure inside the container to continuously increase. During this process, carbon dioxide molecules, with their extremely high permeability, can penetrate the microporous structure and interfiber gaps of the pomace cell walls. When the pressure inside the container accumulates to a certain level, it is rapidly depressurized. The instantaneous release of high-pressure gas causes a dramatic expansion in volume, creating a "micro-explosion" effect inside the cell walls—this effect tears apart the cellulose-pectin entanglement network from the inside of the cell walls outwards, releasing the previously tightly bound pectin.

[0014] Compared to steam explosion, dry ice in-situ explosion has a completely different effect on the molecular weight of pectin because the two mechanisms of action are fundamentally different: The mechanism by which steam explosion damages the molecular weight of pectin: Steam explosion utilizes high-temperature steam (≥100℃) as the explosion medium. Its mechanism is chemical degradation—high temperature triggers the thermal breakage of glycosidic bonds in the pectin backbone; high-temperature steam comes into contact with organic acids in the cell wall, creating a weakly acidic environment that induces acid hydrolysis of glycosidic bonds; high temperature conditions accelerate the β-elimination reaction, breaking the glycosidic bonds between galacturonic acid residues in the pectin backbone. These three chemical degradation mechanisms directly attack the covalent bonds of pectin molecules, causing irreversible molecular chain breakage.

[0015] The protective mechanism of dry ice in-situ detonation on pectin molecular weight: Dry ice in-situ detonation occurs at room temperature (15~30℃). Its mechanism is purely physical detonation—the CO2 gas produced by the sublimation of dry ice permeates into the microporous structure of the cell wall. Upon depressurization, the gas volume expands rapidly, tearing the entangled network of cellulose-pectin from the inside of the cell wall outward. This process utilizes physical expansion force rather than a chemical reaction and does not involve any attack on the covalent bonds of pectin molecules—there is no high temperature, no strong acid, and no β-elimination reaction. The CO2 produced by the sublimation of dry ice dissolves in water to form carbonic acid, providing only a mildly acidic environment of about pH 3.5~4.5, far below the pH conditions required for significant acid hydrolysis of the pectin backbone (usually pH < 2.0), and the reaction time is short enough not to trigger the hydrolytic breakage of the pectin backbone.

[0016] (3) Hot water extraction: Mix the blasted residue with water at a material-to-liquid ratio of 1:15~1:30 (g / mL), and extract at a constant temperature of 70~85℃ for 60~180 min. Filter and separate, and collect the extract.

[0017] (4) Pectin separation: The extract was concentrated under vacuum to 1 / 4 to 1 / 3 of its original volume, and 95% ethanol was added for alcohol precipitation. The amount of ethanol used was 1.5 to 3 times the volume of the concentrate. After standing for 1 to 3 hours, the mixture was filtered, the precipitate was collected, washed, dried and pulverized to obtain high molecular weight citrus pectin.

[0018] The resulting pectin has a molecular weight ≥280 kDa and a galacturonic acid content ≥86%.

[0019] Step 2: Preparation of Low-Sweet Sauce (1) Fruit pretreatment: Select fresh fruits (including but not limited to one or more of strawberries, blueberries, citrus, apples, peaches, hawthorns, and plums), wash them, remove the pits / seeds, and then cut them into pieces or pulp them.

[0020] (2) Mixing and blending: Mix the high molecular weight citrus pectin obtained in step one with fruit pulp, sweetener, calcium salt, acidity regulator and water in the following weight ratio:

[0021] The sweetener is one or more of sucrose, fructose, xylitol, sorbitol, and maltitol; the calcium salt is one or more of calcium chloride, calcium lactate, and calcium citrate; and the acidity regulator is one or more of citric acid and malic acid.

[0022] (3) Concentration and gelation: The mixture is vacuum concentrated at 70~85℃ until the soluble solids content is 40%~55%, and the mixture is continuously stirred during the concentration process. After the concentration is completed, it is filled and sealed while hot, and then cooled to room temperature to form a gel, thus obtaining the low-sugar jam product.

[0023] Preferably, the amount of dry ice added in step one (2) is 30% to 40% of the weight of the sludge.

[0024] Preferably, the extraction temperature in step one (3) is 75~80℃ and the extraction time is 90~150 min.

[0025] Preferably, the amount of high molecular weight citrus pectin added in step two is 0.5 to 1.0 parts (based on 100 parts of fruit pulp).

[0026] Preferably, the amount of sweetener added in step two is 25 to 35 parts.

[0027] Preferably, the amount of calcium salt added in step two is 0.03 to 0.06 parts (based on the total amount of calcium salt).

[0028] Preferably, the soluble solids content at the concentration endpoint in step two is 45% to 50%.

[0029] Compared with the prior art, the beneficial effects of this application are: 1. Significantly improves the gelling properties of low-sugar jams. This invention utilizes the long molecular chain characteristics of high molecular weight pectin (≥280 kDa) to form a denser three-dimensional network structure under the cross-linking effect of calcium ions. The gel strength of the jam is increased by 80%~150% compared with that using conventional low molecular weight pectin, and the jam is more uniform and stable.

[0030] 2. Effectively solves the problem of water separation during storage of low-sugar jams. The gel network formed by high molecular weight pectin is denser and has a stronger physical ability to retain water. The water separation rate of jams is significantly reduced under storage conditions of 4℃ and 25℃, and the shelf life is extended to more than 12 months.

[0031] 3. This invention transforms citrus processing byproducts, such as peel and pomace, into high-molecular-weight pectin, which can be directly used in the production of low-sugar jams. This achieves a transformation from "waste" to "high-value-added food ingredient," resulting in significant economic and environmental benefits. This invention organically integrates pectin extraction with jam preparation; wet pectin can be directly used in jam blending, avoiding molecular weight degradation caused by pectin drying, storage, and reconstitution in traditional processes. Detailed Implementation

[0032] The embodiments of this application will now be described in more detail with reference to the examples. While embodiments of this application are shown in the examples, it should be understood that this application can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make this application more thorough and complete, and to fully convey the scope of this application to those skilled in the art.

[0033] The specific detection methods involved in this application are as follows: Molecular weight determination: The molecular weight of pectin was determined by high-performance gel permeation chromatography (HPGPC).

[0034] Galacturonic acid content determination: The galacturonic acid content in pectin was determined by the m-hydroxybiphenyl method (Blumenkrantz method).

[0035] Determination of esterification degree: The determination was performed according to the chemical titration method in the National Food Safety Standard GB 25533-2010. Accurately weigh 0.5 g of pectin sample, moisten with ethanol, and dissolve in 100 mL of deionized water. Using phenolphthalein as an indicator, titrate with 0.1 mol / L NaOH standard solution to the endpoint, and record the volume consumed, V1. Then add 20 mL of 0.5 mol / L NaOH solution, saponify for 30 min, add 20 mL of 0.5 mol / L HCl solution, and titrate again with 0.1 mol / L NaOH to the endpoint, recording the volume consumed, V2.

[0036] Degree of esterification (%) = V2 / (V1+V2)×100%.

[0037] Hardness test: Measured using a cylindrical probe with a diameter of 0.5 inches. Compress the gel at a constant speed of 1.0 mm / s until 50% of the initial height is reached, and record the maximum peak force (g). Each sample was measured in triplicate, and the average value was taken.

[0038] Water-holding capacity test: After the gel was allowed to stand at 4℃ for 24 h, it was centrifuged at 8000 rpm for 10 min. The water expelled was blotted dry with filter paper. The mass of the gel before centrifugation was recorded as M1, and the mass of the gel after centrifugation was recorded as M2. The water-holding capacity of the gel was calculated using the following formula: Water-holding capacity (%) = M2 / M1 × 100%.

[0039] Example 1 (Preparation of high molecular weight citrus pectin) Take 10 kg of fresh citrus peel residue, remove impurities, wash with clean water, and cut into pieces about 1 cm in size. Blanch the peel residue pieces in 90℃ hot water for 5 minutes, then quickly cool and drain.

[0040] The pretreated sludge was placed in a sealed, pressure-resistant container, and dry ice (3 kg) equal to 30% of the sludge's weight was added. The container was then sealed and left to stand at 25°C for 60 minutes. The container was then quickly opened to release the pressure, and the treated sludge was removed.

[0041] The blasted pomace was mixed with water at a ratio of 1:20 (g / mL) and extracted at 80℃ with stirring (200 rpm) for 120 min. The extract was collected by filtration. The extract was concentrated under vacuum to 1 / 3 of its original volume, and precipitated with 2 times its volume of 95% ethanol. After standing for 2 h, the precipitate was filtered. The precipitate was washed three times with 75% ethanol, dried under vacuum at 45℃ to constant weight, pulverized, and sieved to obtain high molecular weight citrus pectin.

[0042] The resulting pectin had a molecular weight of 296.5 kDa, a galacturonic acid content of 87.3%, and a degree of esterification of 72.8%.

[0043] Example 2 (Preparation of low-sugar strawberry jam using high molecular weight pectin) Take 10 kg of fresh strawberries, wash them, remove the stems, and then pulp them to obtain strawberry pulp.

[0044] Take 0.8 parts of the high molecular weight citrus pectin prepared in Example 1, 100 parts of strawberry puree, 30 parts of sucrose, and 0.08 parts of calcium chloride (equivalent to Ca). 2+ Mix 0.029 parts of citric acid (to adjust pH to 3.5) and 20 parts of water until well combined.

[0045] The mixture was vacuum concentrated at 80°C until the soluble solids content reached 48%, with continuous stirring during the concentration process. After concentration, it was filled into glass bottles while still hot, sealed, and allowed to cool naturally to room temperature to form a gel, yielding the finished strawberry low-sugar jam. Example

[0046] Take 10 kg of fresh blueberries, wash them, and then pulp them to obtain blueberry pulp.

[0047] Take 0.5 parts of the high molecular weight citrus pectin prepared in Example 1, 100 parts of blueberry pulp, 35 parts of xylitol, and 0.10 parts of calcium lactate (equivalent to Ca). 2+ Mix 0.018 parts of citric acid (to adjust pH to 3.3) and 15 parts of water until homogeneous. Concentrate, fill, and cool according to the method in Example 2. Example

[0048] Take 10 kg of fresh citrus pulp (with seeds removed), mash it to obtain citrus pulp pulp.

[0049] Take 1.2 parts of the high molecular weight citrus pectin prepared in Example 1, 100 parts of citrus pulp, 40 parts of a mixture of sucrose and sorbitol (mass ratio 2:1), and 0.12 parts of calcium chloride (equivalent to Ca). 2+ Mix 0.043 parts of citric acid (to adjust pH to 3.6) and 25 parts of water until homogeneous. Concentrate, fill, and cool according to the method in Example 2.

[0050] Comparative Example 1 (Preparation of low-sugar strawberry jam using conventional commercial low-ester pectin) Take 10 kg of strawberries from the same source as in Example 2, wash and remove the stems, then pulp them to obtain strawberry pulp.

[0051] Take 0.8 parts of commercially available conventional citrus low-ester pectin (molecular weight approximately 110 kDa, degree of esterification approximately 45%) and prepare strawberry low-sugar jam according to the formula and process of Example 2.

[0052] Comparative Example 2 (Preparation of low-sugar strawberry jam using pectin extraction via steam explosion) Citrus peel residue was subjected to steam explosion (0.3 MPa, 3 min) followed by acid extraction (pH 2.0, 80℃) according to method CN103804514A. The resulting pectin had a molecular weight of 112.8 kDa and a galacturonic acid content of 74.3%. 0.8 parts of this pectin were used to prepare low-sugar strawberry jam according to the formula and process of Example 2.

[0053] Comparative Example 3 (Preparation of low-sugar strawberry jam without pectin) Take 10 kg of strawberries from the same source as in Example 2, wash and remove the stems, then pulp them to obtain strawberry pulp.

[0054] Without adding any pectin, the mixture consisted of 100 parts strawberry puree, 30 parts sucrose, and 20 parts water, and was concentrated, filled, and cooled according to the method in Example 2.

[0055] Comparative Example 4 (using low molecular weight pectin, increasing the amount added) Take 1.6 parts of commercially available conventional low-ester citrus pectin (molecular weight approximately 110 kDa) (twice the amount added in Example 2), and the rest of the formulation and process are the same as in Example 2.

[0056] Results and Discussion: The jam performance test results of Examples 1-4 and Comparative Examples 1-4 are shown in Table 1.

[0057] Table 1. Results of jam performance tests in Examples 1-4 and Comparative Examples 1-4

[0058] Results analysis: (1) High molecular weight pectin plays a decisive role in improving the hardness of jam.

[0059] Example 2 (molecular weight 296.5 kDa, addition amount 0.8 parts) had a hardness of 245.6 g, while Comparative Example 1 (molecular weight ~110 kDa, same addition amount) had a hardness of only 98.4 g—the hardness of high molecular weight pectin is 2.5 times that of low molecular weight pectin. Even when Comparative Example 4 increased the addition amount of low molecular weight pectin to 2 times (1.6 parts), its hardness (152.3 g) was still much lower than that of Example 2 (245.6 g). This fully demonstrates that the molecular weight of pectin has a much greater impact on hardness than the amount added—it is better to add a small amount of high molecular weight pectin than to add more low molecular weight pectin.

[0060] (2) High molecular weight pectin significantly improves the water-holding capacity of jam.

[0061] Example 2 showed a water retention rate of 98.8% at 4°C and 97.2% at 25°C; while Comparative Example 1 showed 94.4% and 87.7% respectively, and Comparative Example 2 showed 93.2% and 85.3% respectively. The dense three-dimensional network formed by high molecular weight pectin has a stronger physical water retention capacity, effectively solving the industry problem of water separation during the storage of low-sugar jams.

[0062] (3) The pectin extracted by steam explosion is significantly superior to that extracted by steam explosion.

[0063] The hardness (87.6 g) and water retention (93.2% at 4°C) of Comparative Example 2 (steam-exploded pectin, molecular weight 112.8 kDa) were significantly worse than those of Example 2 (245.6 g and 98.8%). This directly demonstrates that the destruction of pectin molecular weight by steam explosion (loss of 64%) directly degrades the gelling properties of the jam, while the high molecular weight pectin extracted by dry ice in situ explosion in this invention perfectly maintains the gelling quality of the jam.

[0064] (4) The addition of pectin is indispensable.

[0065] Comparative Example 3 (without pectin) could hardly form an effective gel (hardness only 32.5 g) and had a low water retention (64.4% at 25°C), indicating that pectin is a key component in the formation of the gel network in low-sugar jams.

[0066] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for improving the gelling properties of low-sugar jams using high molecular weight citrus pectin, characterized in that, Includes the following steps: Preparation of high molecular weight citrus pectin: Citrus peel residue was pretreated by in-situ dry ice explosion, then extracted with hot water, precipitated with alcohol, and dried to obtain high molecular weight citrus pectin with a molecular weight ≥280 kDa and a galacturonic acid content ≥86%. Preparation of low-sugar jam: The high molecular weight citrus pectin obtained in step (1) is mixed with fruit pulp, sweetener, calcium salt, acidity regulator and water, concentrated and then bottled and cooled to obtain the finished low-sugar jam; The dry ice in-situ explosion pretreatment in step (1) is as follows: place the citrus peel residue in a sealed container, add 20% to 50% dry ice of the peel residue mass, let it stand at 15 to 30°C for 30 to 90 minutes, and then release the pressure to use the volume expansion effect generated by the sublimation of dry ice to explode the cell wall from the inside.

2. The method according to claim 1, characterized in that, The hot water extraction conditions described in step (1) are: material-to-liquid ratio of 1:15 to 1:30 (g / mL), extraction temperature of 70 to 85℃, and extraction time of 60 to 180 min.

3. The method according to claim 1, characterized in that, The weight ratio of each component in step (2) is as follows: 100 parts of fruit pulp, 0.3~1.5 parts of high molecular weight citrus pectin, 20~45 parts of sweetener, 0.02~0.10 parts of calcium salt, appropriate amount of acidity regulator, and 10~30 parts of water.

4. The method according to claim 1, characterized in that, The sweetener mentioned in step (2) is one or more of sucrose, fructose, xylitol, sorbitol, and maltitol.

5. The method according to claim 1, characterized in that, The calcium salt mentioned in step (2) is one or more of calcium chloride, calcium lactate, and calcium citrate.

6. The method according to claim 1, characterized in that, The acidity regulator mentioned in step (2) is one or more of citric acid and malic acid, used to adjust the pH to 3.0~3.

8.

7. The method according to claim 1, characterized in that, The concentration described in step (2) is vacuum concentration, the concentration temperature is 70~85℃, and the concentration endpoint is a soluble solids content of 40%~55%.

8. The low-sugar jam prepared by the method according to any one of claims 1-7.

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