Light and healthy roast duck sauce and preparation method thereof

Abstract

The application discloses a light and healthy roast duck sauce and a preparation method thereof, and belongs to the technical field of food condiments. The roast duck sauce is prepared by using sweet soybean paste as a base, replacing jam with pear juice fermented by Lactobacillus plantarum and Saccharomyces boulardii, relying on triple natural fruit acids to remove greasiness, protect color and harmonize flavor; and yam powder and pea starch are used to cooperate with water locking and thickening, so that the problem of water separation of the fermented pear juice is solved; the roast duck sauce prepared by the method is low in fat, refreshing, and has a coordinated flavor, a delicate and stable texture, and does not need high-temperature frying; two-stage low-temperature sterilization is adopted, endogenous antibacterial property is good, preservatives can be added less, the roast duck sauce is suitable for light food and fat control people, and is convenient for industrialized production.

Description

Technical Field

[0001] This invention relates to a light and healthy roast duck sauce and its preparation method, belonging to the field of food condiment technology. Background Technology

[0002] Peking duck is a classic traditional Chinese delicacy, beloved by consumers for its crispy skin, tender meat, and rich, fatty flavor. After a century of development, it has become a standardized and industrialized food product, widely used in restaurants, prepared dishes, and snack foods. Peking duck sauce, as a core condiment to accompany Peking duck, is a key component determining the overall flavor, texture, and consumer experience. It plays a vital role in neutralizing the greasiness of the duck meat, enhancing its aroma and freshness, enriching its flavor profile, and masking any gamey or unpleasant odors.

[0003] Traditional Peking duck sauce is made primarily from sweet bean sauce, white sugar, cooking oil, and spices, through simple simmering and blending. The recipe and process are relatively standardized, and the production threshold is low. However, with the development of the food industry and the upgrading of consumer dietary demands, the market has placed higher requirements on the flavor profile, texture, palatability, and storage stability of Peking duck sauce. The single, traditional recipe can no longer meet the diverse consumption scenarios and high-quality food needs. Therefore, various improved Peking duck sauce recipes and preparation processes have emerged in the industry to optimize product flavor and quality.

[0004] However, existing roast duck sauces generally suffer from a heavy and sticky texture. The consistency of the sauce is poorly controlled, resulting in a greasy and sticky feeling on the tongue. When eaten, it easily masks the crispy and savory flavor of the roast duck itself, leading to an overall heavy and dull taste lacking freshness. Secondly, the flavors of these products are monotonous and fixed. Most roast duck sauces rely solely on a basic sweet and salty base flavor, with thin layers of spice and savory aromas, resulting in low flavor distinctiveness. This makes it difficult to adapt to the different types of roast duck and the taste preferences of different consumers, leading to serious homogenization.

[0005] Based on this, current industry practices for flavor improvement often involve simply mixing various flavor additives, spice extracts, and umami enhancers. However, these flavor components fail to achieve molecular-level fusion and synergistic enhancement, leading to fragmented flavors, chaotic layers, and inconsistent top and bottom notes. This results in an imbalance of sweet, salty, fragrant, and umami flavors, as well as abrupt local flavors and prominent off-flavors, failing to create a rich, harmonious, and progressively complex flavor system. Furthermore, existing roast duck sauces suffer from unreasonable material ratios and emulsification stabilization system designs. The multiphase systems of oils, sugars, colloids, and aqueous solutions in the sauce exhibit poor compatibility, making it highly susceptible to stability issues such as oil-water separation, stratification, sedimentation, sauce clumping, thinning, and discoloration during long-term storage. This leads to significant quality degradation within the shelf life, affecting not only the product's appearance but also flavor loss and taste deterioration, drastically reducing the product's shelf-life quality and market applicability.

[0006] Therefore, developing a high-quality roast duck sauce with a refreshing and non-greasy taste, a harmonious and mellow complex flavor, high integration of components, excellent system stability, long-term storage capability, and suitability for industrial mass production has become an urgent technical problem to be solved in this field. Summary of the Invention

[0007] To address the aforementioned issues, this invention provides a light and healthy roast duck sauce and its preparation method. This invention uses sweet bean sauce as a base, employing *Lactobacillus plantarum* and *Saccharomyces boulardii* to ferment pear juice instead of jam. It leverages triple natural fruit acids to reduce greasiness, protect color, and harmonize flavor. Yam powder and pea starch are combined to synergistically lock in moisture and thicken, solving the problem of water separation during pear juice fermentation. The roast duck sauce prepared by this invention is low-fat, refreshing, and has a harmonious flavor and a delicate, stable texture. It requires no high-temperature frying, uses a two-stage low-temperature sterilization process, exhibits good endogenous antibacterial properties, requires less preservatives, is suitable for people with light diets and those controlling fat intake, and is easy for industrial production.

[0008] The first objective of this invention is to provide a method for preparing roast duck sauce, comprising the following steps: (1) Mix white sugar, salt, yam powder, thyme powder, black pepper powder, and white pepper powder, then add water and white vinegar that accounts for 30-50% of the total mass of white vinegar, and stir to obtain a mixture; (2) Add sweet bean sauce to the mixture in step (1), stir, then add jam and fermented pear juice in sequence, stir, then add concentrated lemon juice, sesame oil and the remaining white vinegar, stir again, then add pea starch and stir to obtain crude roast duck sauce. (3) The crude roast duck sauce prepared in step (2) is ultrasonicated, stirred, filled, degassed and sealed, sterilized and cooled to obtain the finished roast duck sauce; The roast duck sauce, by weight, comprises the following components: 80-120 parts sweet bean sauce, 30-50 parts jam, 30-40 parts white sugar, 4-6 parts salt, 6-9 parts yam powder, 10-16 parts white vinegar, 10-16 parts sesame oil, 4-8 parts concentrated lemon juice, 1-2 parts thyme powder, 0.8-1.2 parts black pepper powder, 0.8-1.2 parts white pepper powder, 16-24 parts pea starch, 4-8 parts fermented pear juice, and 8-12 parts water. The preparation method of fermented pear juice is as follows: Pears are washed, cored, and juiced. After enzyme inactivation treatment, the juice is cooled to obtain pear juice. *Lactobacillus plantarum* and *Saccharomyces boulardii* are inoculated into the pear juice at a live bacteria ratio of 0.8–1.2:1.2–0.8 for fermentation. After fermentation, the juice is filtered to obtain fermented pear juice. The total inoculum size of *Lactobacillus plantarum* and *Saccharomyces boulardii* in the pear juice is 8.0 × 10⁻⁶. 6 ~1.2×10 7 CFU / mL pear juice; Lactobacillus plantarum preservation number DSM 28632; Saccharomyces boulardii preservation number CNCMI-745.

[0009] In one embodiment, the jam is one or more of honey grapefruit jam, apple jam, strawberry jam, and blueberry jam.

[0010] In one embodiment, the fermentation is performed as anaerobically at 10-15°C and 10-20 rpm for 42-54 h.

[0011] In one embodiment, the stirring parameters in steps (1) to (3) are 35 to 45 rpm for 6 to 12 minutes.

[0012] In one embodiment, the ultrasound conditions in step (3) are ultrasound at 250~350 W for 2~4 min.

[0013] In one embodiment, the sterilization in step (3) is a two-stage low-temperature sterilization, specifically, first maintaining at 70~78℃ for 8~12 min, and then maintaining at 78~82℃ for 4~6 min.

[0014] A second objective of this invention is to provide a roast duck sauce prepared by any of the methods described above.

[0015] The third objective of this invention is to provide a method for improving the degreasing effect and textural stability of roast duck sauce, comprising the following steps: (1) Mix white sugar, salt, yam powder, thyme powder, black pepper powder, and white pepper powder, then add water and white vinegar that accounts for 30-50% of the total mass of white vinegar, and stir to obtain a mixture; (2) Add sweet bean sauce to the mixture in step (1), stir, then add jam and fermented pear juice in sequence, stir, then add concentrated lemon juice, sesame oil and the remaining white vinegar, stir again, then add pea starch and stir to obtain crude roast duck sauce. (3) The crude roast duck sauce prepared in step (2) is ultrasonicated, stirred, filled, degassed and sealed, sterilized and cooled to obtain roast duck sauce that is degreasing and has a stable texture. The roast duck sauce, by weight, comprises the following components: 80-120 parts sweet bean sauce, 30-50 parts jam, 30-40 parts white sugar, 4-6 parts salt, 6-9 parts yam powder, 10-16 parts white vinegar, 10-16 parts sesame oil, 4-8 parts concentrated lemon juice, 1-2 parts thyme powder, 0.8-1.2 parts black pepper powder, 0.8-1.2 parts white pepper powder, 16-24 parts pea starch, 4-8 parts fermented pear juice, and 8-12 parts water.

[0016] The preparation method of fermented pear juice is as follows: Pears are washed, cored, and juiced. After enzyme inactivation treatment, the juice is cooled to obtain pear juice. *Lactobacillus plantarum* and *Saccharomyces boulardii* are inoculated into the pear juice at a live bacteria ratio of 0.8–1.2:1.2–0.8 for fermentation. After fermentation, the juice is filtered to obtain fermented pear juice. The total inoculum size of *Lactobacillus plantarum* and *Saccharomyces boulardii* in the pear juice is 8.0 × 10⁻⁶. 6 ~1.2×10 7 CFU / mL pear juice; Lactobacillus plantarum preservation number DSM 28632; Saccharomyces boulardii preservation number CNCMI-745.

[0017] In one embodiment, the fermentation is performed as anaerobically at 10-15°C and 10-20 rpm for 42-54 h.

[0018] A fourth objective of this invention is to provide the application of any of the above-described methods in the processing of poultry dipping sauces, noodle wraps, low-fat light meals, and pre-prepared processed meat products.

[0019] Beneficial effects (1) This invention uses Lactobacillus plantarum and Saccharomyces boulardii to ferment pear juice in combination to replace traditional jam, which solves the problems of flavor fragmentation, excessive sweetness, and easy browning and layering of the jam caused by directly adding various jams in the prior art; at the same time, by adding pea starch at the end, the problem of reduced viscosity of the jam caused by fermentation of pear juice and the resulting water separation and layering is solved.

[0020] (2) The roast duck sauce prepared by this invention is light and low in fat, with outstanding degreasing properties. It is enhanced with a small amount of sesame oil and relies on a triple natural fruit acid system to achieve strong degreasing effect, greatly reducing the greasiness. It is suitable for people who want to lose weight, eat light meals, or control their fat intake, and meets the needs of modern healthy diet.

[0021] (3) The roast duck sauce prepared by the present invention has a rich flavor, a mellow soy sauce aroma, a fresh fruit flavor, and the aroma of thyme and pepper. It is balanced and harmonious in terms of sweet, sour, salty and fresh taste. It is not too sweet or greasy when you eat it, and the aftertaste is refreshing and long-lasting. It is highly acceptable.

[0022] (3) The roast duck sauce prepared by the present invention has a stable texture and does not separate into water. The yam powder and pea starch work together to thicken and stabilize the sauce. The sauce is delicate and smooth with excellent spreadability. It does not separate into water, oil, or sediment during long-term storage and has excellent shelf stability.

[0023] (4) The roast duck sauce prepared by the present invention has a bright and natural color, fruit acid protects the color and inhibits browning, and the sauce is uniformly light reddish-brown with a good appearance.

[0024] (5) The preparation process of the present invention is extremely simple and can be mass-produced. The entire process involves stirring at room temperature and does not require high-temperature frying. It has low energy consumption, is easy to operate, and has high batch consistency, enabling standardized continuous production.

[0025] (6) The roast duck sauce prepared by the present invention has a synergistic antibacterial effect with natural antioxidants in a low pH environment. Combined with two-stage low-temperature sterilization, it can extend the shelf life with little or no preservatives. Attached Figure Description

[0026] Figure 1 This is a bar chart comparing the sensory evaluation of different samples in this invention; Figure 2 This is a line graph comparing the total bacterial count of different samples from this invention over 180 days. Figure 3 This is a line graph comparing the browning increase of different samples of the present invention over 180 days; Figure 4 This is a line graph comparing the average viscosity of different samples in this invention. Figure 5 This is a bar chart comparing the flavor integration of different samples in this invention. Figure 6 This is a line graph comparing the basic physiological indicators of different samples in this invention. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, where specific conditions are not specified, are generally performed under conventional conditions in the art. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar with the art.

[0028] In the examples, solutions without a specific solvent are water; operations without a specific temperature refer to room temperature, which is 15-35°C; and percentages without a specific meaning refer to mass percentages.

[0029] The sources of raw materials involved in the examples are as follows: Sweet bean sauce was purchased from Chongqing Shuxiang Agricultural Technology Co., Ltd.; apple jam from Fujian Zhangzhou Zhenwu Food Co., Ltd.; white sugar from Yunnan Xingguanyuan Food Co., Ltd.; edible salt from Shandong Daiyue Salt Manufacturing Co., Ltd.; yam powder from Beijing Tongrentang (Group) Co., Ltd.; white vinegar from Jiangsu Hengshun Vinegar Industry Co., Ltd.; sesame oil from Yihai Kerry Golden Dragon Food Group Co., Ltd.; concentrated lemon juice from Tianauhe; thyme powder from Shandong Pingju Biotechnology Co., Ltd.; black pepper powder from Foshan Haitian Seasoning Food Co., Ltd.; white pepper powder from Foshan Haitian Seasoning Food Co., Ltd.; and pea starch from Xinliang Grain and Oil Processing Co., Ltd.

[0030] Lactobacillus plantarum SP128 was purchased from Shanghai Lianya Probiotics Technology Co., Ltd., with accession number DSM 28632; Lactobacillus plantarum JYLP-326 was purchased from Minsheng Zhongke Jiayi (Shandong) Biotechnology Co., Ltd., with accession number CGMCC NO.18038; The *Bacillus brasiliensis* strain was purchased from *Gray Algae*, with accession number CNCM I-745. Culture media involved in the examples: MRS liquid seed culture medium (g / L): casein peptone 10.0, beef extract 10.0, yeast extract 5.0, glucose 20.0, sodium acetate 5.0, diammonium citrate 2.0, Tween 80 1.0 mL / L, dipotassium hydrogen phosphate 2.0, magnesium sulfate heptahydrate 0.2, manganese sulfate monohydrate 0.05, pH 6.2~6.4; YM liquid medium (g / L): peptone 5.0, yeast extract 3.0, malt extract 3.0, glucose 10.0, pH 6.0~6.2; The measurement methods involved in the examples are as follows: 1. Flavor and Sensory Evaluation Methods Ten trained professional tasters were selected. Each sample was tasted twice, and after each taste, the taster rinsed their mouths three times with the same mouthwash. During the testing process, the evaluation focused on the color, appearance, flavor, and overall palatability of the roast duck sauce. Each taster evaluated each sample individually and recorded the results. The scoring criteria are shown in Table 1.

[0031] Table 1

[0032] 2. Determination of storage stability 80 g of roast duck sauce was placed in a sterile transparent sealed bag and placed in a constant temperature and humidity incubator at 37℃ and 65% relative humidity for accelerated storage test. Samples were taken and tested at 0, 30, 60, 90 and 180 days of storage. The samples were shaken well before each sampling, and the total number of colonies was determined according to the method of GB 4789.2-2016. The number of molds and yeasts was determined according to the method of GB 4789.15-2016.

[0033] 3. Determination of the browning index 80 g of roast duck sauce was placed in a sterile transparent sealed bag and placed in a constant temperature and humidity incubator at 37℃ and 65% relative humidity for accelerated storage test. Samples were taken and tested at 0, 30, 60, 90 and 180 days of storage. 20 mL of ultrapure water was added to 5 g of sample, vortexed and extracted by ultrasonication at 300 W for 10 min, followed by centrifugation at 8000 rpm for 5 min. The absorbance of the supernatant was measured at 420 nm wavelength using a spectrophotometer to characterize the degree of browning.

[0034] 4. Viscosity Measurement The viscosity of roast duck sauce was determined by referring to the viscosity test method in GB / T 22474-2008 "Jam" and combining it with the rotational viscometer method in GB / T 10247-2008 "Viscosity Measurement Method". The method is as follows: Take three parallel samples of each roast duck sauce and place them in a constant temperature environment of 25℃ for 30 min to eliminate the effect of temperature on viscosity. Pour an appropriate amount of sample into the sample cup of the viscometer to the specified scale line, avoiding the generation of air bubbles. Select the corresponding rotor according to the estimated viscosity of the sample, set the rotation speed to 30 rpm, and slowly immerse the rotor into the sample to the specified depth. After the instrument has been running stably for 1 min, record the viscosity reading and take the average value. 5. Spreadability test Take 5 g of roast duck sauce sample, spread it evenly on a glass slide, then stand the slide upright and observe whether it drips within 30 seconds.

[0035] 6. Determination of flavor integration (References: Xie Tian, ​​Wang Dan, Ma Mingjuan, et al. Analysis of flavor active substances in spiced donkey meat by OAV and GC-O-MS method [J]. Food Science, 2018, 39(8):123-128. / [2] Zhang Yaxin, Hu Jiaxing, Li Xuan, et al. Synergistic regulation of flavor in freeze-dried honeysuckle based on compound formulation [J]. Food Science, 2025, 46(21):190-200.) The volatile flavor compounds in Peking duck sauce were determined using headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The specific method is as follows: 1) Weigh 5.00 g of the roast duck sauce to be tested into a 20 mL headspace vial, and add 10 μL of 50 μg / mL 2-octanol solution as an internal standard for quantification. Specific conditions are as follows: Solid-phase extraction conditions: incubation at 55 ℃ for 20 min; extraction at 55 ℃ for 40 min; desorption at 250 ℃ for 3 min; aging at 270 ℃ for 10 min. Gas chromatography conditions: DB-5MS column; temperature program: 40 °C for 3 min, increase to 120 °C at 5 °C / min, hold for 3 min, increase to 240 °C at 8 °C / min, hold for 3 min; carrier gas: He, flow rate: 1.0 mL / min; injection method: splitless; injection port temperature: 250 °C; Mass spectrometry conditions: Scan mode: full scan; Ionization mode: electron ionization source; Ion source temperature: 280 ℃; Transfer line temperature: 250 ℃; Resolution: 60,000; Scan range m / z 35~400.

[0036] The content of volatile flavor compounds was calculated using the following formula, based on data obtained by mass spectrometry combined with the NIST 5 library and retention index: C i = (C) s ×A i ) / A s , In the formula, C i Content of target compound / (µg / kg); C s Content of internal standard / (µg / kg); A i A represents the chromatographic peak area of ​​the target compound; s The peak area of ​​the internal standard.

[0037] 2) Flavor Classification: The detected volatile substances were classified into three categories: A-soy sauce aroma component, B-fermented pear fruit ester / weak acid component, and C-thyme pepper herbal spice component. The A-soy sauce aroma component mainly contains furfural, 2-methylpyrazine, maltol, and benzaldehyde; the B-fermented pear fruit ester / weak acid component mainly contains ethyl lactate, ethyl acetate, ethyl butyrate, β-damascene, and lactic acid; and the C-thyme pepper herbal spice component mainly contains thymol, γ-terpinene, and limonene.

[0038] 3) Calculation of flavor synergy coefficient: The synergy coefficient F is calculated using the odor activity value (OAV). The odor activity value (OAV) is calculated as follows: O i = C i / OT i In the formula: C i The content of any volatile compound is expressed in µg / kg; OT i The aroma threshold of this volatile compound in water is given in µg / kg. i >1 indicates that the component has a significant sensory contribution to the aroma.

[0039] The synergistic fusion coefficient F is obtained by integrating the odor activity values ​​(OAV), and its calculation formula is as follows: F = O A+B+C / (O A +O B +O C )×100 In the formula: O A+B+C The total aroma activity value of the sample with three flavor categories coexisting; O A O B O C The aroma activity of the single soy sauce aroma, single fermented fruit aroma, and single herbal spice system are respectively: the higher the fusion coefficient F, the better the synergistic fusion effect of soy sauce aroma, fermented fruit aroma, and herbal spice aroma.

[0040] F≥80 is grade A (excellent integration), 60≤F<80 is grade B (basic integration), 40≤F<60 is grade C (poor integration), and F<40 is grade D (severe flavor conflict) (Table 2).

[0041] The measured O A O B O C O A+B+C And a summary of the evaluation of flavor integration degree F.

[0042] Table 2

[0043] 7. Determination of soluble solids content According to GB / T 10786-2022 "Test Methods for Canned Foods", soluble solids were determined by taking 2 g of roast duck sauce sample and placing it below the prism of a handheld saccharimeter. The lid was quickly closed and placed under natural light. After adjusting the field of view to be clear, the soluble solids content (°Brix) was read.

[0044] 8. pH measurement Refer to GB / T 10786 The pH value was determined according to the 2006 standard "pH Determination of Canned Foods". The method is as follows: After stirring the sample thoroughly, take an appropriate amount of the slurry, insert the calibrated pH meter electrode into the sample, and record the pH value after the reading stabilizes.

[0045] 9. Water activity determination The water activity of the sample was determined according to GB / T 43859-2024 "Methods for Determining the Performance of Water Activity Meters". The method is as follows: Place 5 g of well-stirred roast duck sauce into the detection tray, cover the sensor, turn on the detection, and read the value after 10 minutes. Record the water activity (Aw).

[0046] 10. Determination of reducing sugars The total sugar content was determined according to the acid hydrolysis procedure (converting non-reducing sugars to reducing sugars) for sucrose determination in GB 5009.8-2016, as follows: Weigh 2.0 g of uniform sample into an Erlenmeyer flask, dissolve it in water, and then use the direct titration method to standardize the alkaline copper tartrate solution with glucose standard solution, and then titrate the sample solution to the endpoint to calculate the total sugar content.

[0047] All of the above indicators were tested in triplicate, and the average value was taken as the final test result.

[0048] Example 1: A light and healthy roast duck sauce 1. Raw material preparation Preparation of *Lactobacillus plantarum* PS128 (DSM 28632) inoculum: Single colonies were picked and inoculated into MRS medium, and cultured at 37℃ and 170 rpm for 24 h with shaking to obtain seed culture; the cells were collected by centrifugation at 8000 rpm for 10 min, washed three times with sterile water to remove residual culture medium, and resuspended in sterile water to a viable cell concentration of 1.0 × 10⁻⁶. 9 CFU / mL, for later use.

[0049] Preparation of *Saccharomyces boulardii* inoculum (CNCM I-745): Single colonies were picked and inoculated into YM medium, and cultured at 28℃ and 180 rpm for 24 h with shaking to obtain seed culture; the cells were collected by centrifugation at 8000 rpm for 10 min, washed three times with sterile water, and resuspended in sterile water to a viable cell concentration of 1.0 × 10⁻⁶. 9 CFU / mL, for later use.

[0050] The preparation method of fermented pear juice is as follows: Fresh pears are washed, cored, crushed, and juiced. The juice is then subjected to an enzyme inactivation treatment by instantaneous heat treatment at 80℃ for 30 seconds, followed by rapid cooling to 15℃ to obtain pear juice. The pear juice is transferred to a closed anaerobic fermentation tank, and activated *Lactobacillus plantarum* PS128 (DSM 28632) and *Saccharomyces boulardii* (CNCM I-745) inoculum are added at a 1:1 ratio, resulting in a total viable bacteria concentration of 1.0 × 10⁻⁶. 7 CFU / mL pear juice was anaerobically fermented at 12℃ and 15 rpm for 48 h. After fermentation, the mixture was filtered through a 400-mesh filter. The resulting filtrate was the co-fermented pear juice, which was stored at 4℃ for later use.

[0051] 2. The preparation method of Qingjian Roast Duck Sauce is as follows: (1) Mix the white sugar, salt, yam powder, thyme powder, black pepper powder and white pepper powder evenly, then add water and white vinegar accounting for 30% of the total mass of white vinegar, stir at 45 rpm for 8 min to obtain a moistened mixture; (2) Add sweet bean sauce to the mixture in step (1) and stir at 40 rpm for 12 min. Then add honey grapefruit sauce and fermented pear juice and stir at 40 rpm for 8 min. Then add concentrated lemon juice, sesame oil and the remaining white vinegar and stir at 40 rpm for 8 min. Then add pea starch and stir at 35 rpm for 10 min to obtain crude roast duck sauce. (3) The crude roast duck sauce prepared in step (2) is ultrasonically homogenized at room temperature at 300 W for 3 min and then stirred at 40 rpm for 7 min. After vacuum filling, degassing and sealing, it is first kept at 75℃ for 10 min and then kept at 80℃ for 5 min for two-stage low-temperature sterilization. After sterilization, it is quickly cooled to 20℃ and then refrigerated to obtain the finished roast duck sauce.

[0052] The ingredients, by weight, include the following components: 100 g sweet bean sauce, 40 g honey grapefruit jam, 35 g white sugar, 5 g salt, 7.5 g yam powder, 10 g water, 13 g white vinegar, 13 g sesame oil, 6 g concentrated lemon juice, 1.5 g thyme powder, 1 g black pepper powder, 1 g white pepper powder, 20 g pea starch, and 6 g fermented pear juice.

[0053] Example 2: Replace the honey grapefruit jam with apple jam. The specific implementation method is the same as in Example 1, except that the honey grapefruit sauce is replaced with apple sauce, while the other steps remain the same, to prepare the roast duck sauce.

[0054] Example 3: Replace honey grapefruit jam with strawberry jam The specific implementation method is the same as in Example 1, except that the honey grapefruit jam is replaced with strawberry jam, while the other steps remain the same, to prepare the roast duck sauce.

[0055] Example 4: Replace the honey grapefruit jam with blueberry jam The specific implementation method is the same as in Example 1, except that the honey grapefruit jam is replaced with blueberry jam, while the other steps remain the same, to prepare the roast duck sauce.

[0056] Example 5: Changing the sterilization method The specific implementation method is the same as in Example 2, except that the two-stage sterilization in step (3) is replaced with one-stage sterilization. The one-stage sterilization condition is sterilization at 80°C for 8 minutes. The remaining steps are kept the same to prepare roast duck sauce.

[0057] Comparative Example 1: Changing the preparation process of fermented pear juice 1 The specific implementation method is the same as in Example 2, except that the preparation method of fermented pear juice is changed: the co-fermentation of Lactobacillus plantarum SP128 (DSM 28632) and Saccharomyces boulardii (CNCM I-745) is changed to single fermentation of Lactobacillus plantarum SP128 (DSM28632), while the total inoculum amount remains unchanged. Specifically: Fresh pears were washed, cored, crushed, and juiced. The juice was then subjected to an enzyme inactivation treatment by instantaneous heat treatment at 80℃ for 30 seconds, followed by rapid cooling to 15℃ to obtain pear juice. The pear juice was transferred to a sealed anaerobic fermenter and inoculated with activated *Lactobacillus plantarum* (DSM 28632) inoculum, with a total viable bacteria concentration of 1.0 × 10⁻⁶. 7 CFU / mL pear juice was anaerobically fermented at 12℃ and 15 rpm for 48 hours. After fermentation, the mixture was filtered through a 400-mesh filter, and the resulting filtrate was the co-fermented pear juice, which was stored at 4℃ for later use.

[0058] The remaining steps remain the same to prepare the roast duck sauce.

[0059] Comparative Example 2: Changing the preparation process of fermented pear juice 2 The specific implementation method is the same as in Example 2, except that the preparation method of fermented pear juice is changed: the co-fermentation of Lactobacillus plantarum PS128 (DSM 28632) and Saccharomyces boulardii (CNCM I-745) is changed to single fermentation of Saccharomyces boulardii (CNCM I-745), while the total inoculum amount remains unchanged. Specifically: Fresh pears were washed, cored, crushed, and juiced. The juice was then subjected to an enzyme-inactivating treatment at 80℃ for 30 seconds, followed by rapid cooling to 15℃ to obtain pear juice. The pear juice was transferred to a sealed anaerobic fermenter and inoculated with activated *Saccharomyces boulardii* (CNCM I-745) inoculum, with a total viable cell concentration of 1.0 × 10⁻⁶. 7 CFU / mL pear juice was anaerobically fermented at 12℃ and 15 rpm for 48 hours. After fermentation, the mixture was filtered through a 400-mesh filter, and the resulting filtrate was the co-fermented pear juice, which was stored at 4℃ for later use.

[0060] The remaining steps remain the same to prepare the roast duck sauce.

[0061] Comparative Example 3: Replace fermented pear juice with pear jam The specific implementation method is the same as in Example 2, except that the fermented pear juice is replaced with an equal amount of pear sauce, while the other steps remain the same, to prepare roast duck sauce.

[0062] Comparative Example 4: No fermented pear juice added The specific implementation method is the same as in Example 2, except that the fermented pear juice is replaced with an equal amount of water, while the other steps remain the same, to prepare roast duck sauce.

[0063] Comparative Example 5: Replace pea starch with corn starch The specific implementation method is the same as in Example 2, except that the pea starch is replaced with an equal amount of corn starch, while the other steps remain the same, to prepare the roast duck sauce.

[0064] Comparative Example 6: Replace pea starch with tapioca starch The specific implementation method is the same as in Example 2, except that the pea starch is replaced with an equal amount of tapioca starch, while the other steps remain the same, to prepare roast duck sauce.

[0065] Comparative Example 7: No pea starch added The specific implementation method is the same as in Example 2, except that the pea starch is replaced with an equal amount of water, while the other steps remain the same, to prepare the roast duck sauce.

[0066] Comparison ratio 8: Traditional roast duck sauce The traditional method for preparing roast duck sauce is as follows: The roast duck sauce is prepared by mixing 100 g of sweet bean sauce, 50 g of white sugar, 30 g of sesame oil and 30 g of water at 40 rpm for 15 minutes.

[0067] Comparative Example 9: Modifying the preparation process of fermented pear juice 3 The specific implementation method is the same as in Example 1, except that the preparation process of fermented pear juice is changed: Lactobacillus plantarum PS128 (DSM 28632) is replaced with Lactobacillus plantarum JYLP-32 (CGMCC NO.18038), specifically: Fresh pears were washed, cored, crushed, and juiced. The juice was then subjected to an enzyme inactivation treatment by instantaneous heat treatment at 80℃ for 30 seconds, followed by rapid cooling to 15℃ to obtain pear juice. The pear juice was transferred to a sealed anaerobic fermenter and inoculated with activated *Lactobacillus plantarum* (CGMCC NO.18038) and *Saccharomyces boulardii* (CNCM I-745) in a 1:1 ratio, resulting in a total viable bacteria concentration of 1.0 × 10⁻⁶. 7 CFU / mL pear juice was anaerobically fermented at 12℃ and 15 rpm for 48 h. After fermentation, the mixture was filtered through a 400-mesh filter, and the resulting filtrate was the co-fermented pear juice, which was stored at 4℃ for later use. The preparation method of Lactobacillus plantarum JYLP-326 (CGMCCNO.18038) inoculum was the same as that of Lactobacillus plantarum PS128 (DSM 28632).

[0068] The remaining steps remain the same to prepare the roast duck sauce.

[0069] Example 6: Performance Measurement The properties of the roast duck sauce prepared in Examples 1-5 and Comparative Examples 1-9 were measured.

[0070] 1. Flavor and sensory evaluation The sensory evaluation results are shown in Table 3 and Figure 1 As shown, Examples 1-5 received a combined score of 8.4. Scoring 9.4, this sauce boasts a bright color, delicate texture, no water separation or layering, balanced flavor, and a prominent refreshing quality, significantly outperforming all other comparative examples in overall sensory quality. Comparative Example 1 exhibited excessive lactic acid accumulation, resulting in a sharp and abrupt acidity that clashed with the inherent aroma of the roast duck sauce. Simultaneously, its stability decreased, with slight water separation and a significant reduction in flavor harmony. Comparative Example 2 generated a large amount of alcohols during fermentation, producing a pronounced alcoholic aroma that masked the main flavor, exacerbating the layering problem and worsening the eating experience. Comparative Examples 3 and 4 showed increased oiliness, intensified browning tendency, and a loose texture prone to layering. Comparative Example 5 used corn starch instead of pea starch, resulting in decreased acid resistance, making the sauce prone to water separation and a less pronounced layering. The uniformity of the texture deteriorated; Comparative Example 6 used tapioca starch instead of pea starch, resulting in a brittle texture, poor water retention, and easy separation; Comparative Example 7 did not add pea starch, resulting in a significantly reduced viscosity of the sauce, severe water separation and flow, and a loose and uneven texture; Comparative Example 8 had a heavy and sticky taste, a dark color, and a single flavor; Comparative Example 9 replaced Lactobacillus plantarum JYLP-326, resulting in excessive lactic acid production, an abrupt sour taste, insufficient polyphenol release, a darker color, slight water separation in the sauce, and inferior flavor and texture compared to the experimental group.

[0071] The results showed that adding multiple jams directly to Peking duck sauce would increase its greasiness and exacerbate its browning tendency, while the addition of co-fermented pear juice could improve this problem, which is the core of optimizing flavor, balancing sweet and sour, and naturally protecting color. Pea starch could also improve the problems of low viscosity, insufficient water retention, and easy water absorption and separation caused by fermented pear juice. If pea starch was replaced with corn starch and tapioca starch, the problem of easy water absorption of the sauce would still exist, and a stable Peking duck sauce could not be prepared. Other Lactobacillus plantarum strains may not produce synergistic benefits with Saccharomyces boulardii. The metabolic characteristics of Lactobacillus plantarum strain PS128 are the key limiting conditions for balancing sweet and sour and improving sensory quality.

[0072] Table 3

[0073] 2. Storage stability test The results of the storage stability test of roast duck sauce are shown in Table 4 and... Figure 2As shown, in Examples 1-5 of the present invention, after 180 days of accelerated storage, the total bacterial count was <10 CFU / g, and molds and yeasts were not detected, indicating excellent microbial safety. Comparative Examples 1 and 2 had simple metabolite components and narrow antibacterial spectrums, with microorganisms gradually proliferating in the later stages of storage; Comparative Examples 3 and 4 showed increased pH and water activity, losing natural antibacterial components, leading to a large proliferation of miscellaneous bacteria; Comparative Examples 5 and 6 showed poor starch acid resistance and loose local structure, providing a growth environment for microorganisms; Comparative Example 7 showed a sharp decrease in the water-holding capacity of the sauce, increasing free water and accelerating microbial reproduction; Comparative Example 8 had high water activity and a near-neutral pH, lacking natural antibacterial components, resulting in the most severe microbial contamination; Comparative Example 9, after replacing *Lactobacillus plantarum*, showed a decrease in the production of endogenous antioxidants and antibacterial substances, significantly reducing shelf-life microbial stability. The results showed that, relying on the natural antibacterial agents of fermented pear juice and the dense colloid of peas, no bacteria were detected in the roast duck sauce within 180 days. Removing the fermented pear juice, using single bacteria or other lactic acid bacteria, or replacing ordinary starch would all cause a decline in the antibacterial ability of the system and a significant increase in the risk of excessive microorganisms during storage.

[0074] Table 4. Determination of bacterial colonies in roast duck sauce after different storage days.

[0075] 3. Determination of the browning index The measurement results are shown in Table 5 and Figure 3 As stated above, after 180 days of accelerated storage, Examples 1-5 showed a browning increase of only 7.56%-9.09%, demonstrating excellent color retention. Comparative Examples 1 and 2, however, exhibited incomplete polyphenol conversion, low antioxidant content, and browning increases exceeding 32%. Comparative Examples 3 and 4 completely lacked fermentable antioxidants, resulting in rapid darkening of color during long-term storage. Comparative Examples 5 and 6 lacked auxiliary color-protecting capabilities, and even slight water separation accelerated the browning process. Comparative Example 7 showed a damaged sauce structure, increased oxygen penetration, and a higher degree of browning. Comparative Example 8 contained no natural color-protecting components, with a browning increase of up to 71.20%, resulting in severe deterioration of appearance quality. Comparative Example 9 showed a browning increase far exceeding that of the examples, indicating that the *Lactobacillus plantarum* JYLP-326 system lacked sufficient antioxidant capacity, leading to severe color deterioration during long-term storage, and was inferior to the color-protecting technology specific to the PS128 strain. The results show that dual-strain fermentation can significantly reduce the long-term browning increase; unfermented pear juice, single-strain fermentation, and starch replacement all significantly reduced the system's antioxidant capacity, resulting in rapid darkening of color after storage; dual-strain co-fermentation is the core technical means to improve the product's antioxidant and browning-inhibiting capabilities.

[0076] Table 5. Determination of browning index of roast duck sauce after different storage days.

[0077] 4. Viscosity and spreadability test The viscosity and spreadability of different roast duck sauces are shown in Table 6. Figure 4 As shown, the viscosity of the light and healthy roast duck sauce in Examples 1-5 is approximately 16500 mPa. The relative standard deviation was small, with no dripping within 30 seconds, uniform coating, and good spreadability. Comparative Examples 1 and 2 showed acidity imbalance in the fermentation products, slightly damaging the gel structure, resulting in decreased viscosity and dripping. Comparative Examples 3 and 4 exhibited altered physicochemical environments, further deteriorating textural stability. Comparative Examples 5 and 6, two types of conventional starches, showed weak acid resistance, gradually hydrolyzing under the acidity of this formula, leading to viscosity reduction and water separation. Comparative Example 7 lost its core thickening component, resulting in excessively fluid paste that could not be properly spread. Comparative Example 8 relied solely on oil and simple gelatinization for thickening, exhibiting the lowest viscosity and the most prominent flow problem. Comparative Example 9, due to the high acidity of fermented pear juice, slightly damaged the starch gel, resulting in decreased viscosity, flow, and reduced spreadability, verifying that the selection of the bacterial strain directly affects the textural stability of the finished product. The results show that pea starch is the key ingredient for acid-resistant thickening. The combination of yam and pea starch with fermented pear juice can maintain a stable paste that does not drip when applied. Replacing or removing this starch will directly cause the product to lose its basic performance. The absence of fermented pear, changes in bacterial strain, or replacement or removal of pea starch will destroy the acid-resistant gel, reduce viscosity, cause severe flow, and render the product unusable.

[0078] Table 6

[0079] 5. Flavor integration degree determination The results of flavor integration tests for different roast duck sauces are shown in Tables 7 and 8. Figure 5The F-values ​​of the comparative examples decreased significantly. The single-strain, unfermented pear juice samples scored only 39-60 points, belonging to Grade C (flavor fragmentation), while the samples with different strains / ordinary starch scored 61-69 points, indicating an unbalanced aroma. The roast duck sauces in Examples 1-5 used dual-strain co-fermentation. The resulting esters, weak organic acids, and other flavor compounds perfectly complemented the sweet bean sauce and spices, achieving a fusion score ≥93, all classified as Grade A (high fusion). The three aroma types synergistically interacted without masking or antagonizing each other, achieving a multi-flavor integration. The roast duck sauces in Comparative Examples 1 and 2, fermented with a single strain, produced a pungent odor, directly damaging the flavor system. Comparative Examples 3 and 4, by removing fermented pear juice, lost their core fruit aroma. The roast duck sauces in Comparative Examples 5-7, using other starch systems, altered the aroma release rate, reduced aroma persistence, and decreased overall fusion. Comparative Example 8 relied solely on sweetness, saltiness, and soy sauce aroma to form a single flavor system. Comparative Example 9 exhibited an overly prominent lactic acid aroma, masking the fruit aroma and resulting in poor flavor balance. The results show that specific dual-strain fermentation produces a suitable fruit aroma, with a high degree of integration of soy sauce aroma, fruit flavor, and spiciness; however, the absence of fermented pear will result in no fruit aroma, and the fermented pear juice produced by single-strain fermentation will produce an irritating off-flavor. Replacing or removing starch will accelerate the loss of aroma, resulting in a fragmented flavor and a significant reduction in the sense of layering. Furthermore, replacing Lactobacillus plantarum PS128 with other Lactobacillus plantarum strains JYLP-326 will disrupt the balance of flavor ratios and make it impossible to achieve multi-layered integrated integration.

[0080] Table 7

[0081] Table 8

[0082] 6. Determination of basic physicochemical properties The results of the determination of soluble solids content, pH value, water activity, and total sugar content of roast duck sauce are shown in Table 9. Figure 6As shown, the light and healthy roast duck sauces in Examples 1-5 have a pH of 2.96-3.01, a water activity of 0.796-0.823, and a total sugar content of 21.3-22.4 g / 100g, which falls within the safe range of low pH, low water activity, and low sugar content. Comparative Examples 1 and 2 have uncontrollable acid production, with pH deviating from the optimal range and water activity increasing simultaneously. Comparative Examples 3 and 4 lose their fruit acid regulating effect, resulting in a significant increase in pH and Aw, weakened antibacterial ability, and a higher total sugar content due to formula imbalance. Comparative Examples 5 and 6 show that starch hydrolysis indirectly alters the system's microenvironment, causing a slight increase in pH. Comparative Example 7 shows a decrease in water-holding capacity and an increase in water activity. Comparative Example 8 has extremely high water activity, a pH close to neutral, and severely excessive total sugar content, which neither meets the light food positioning nor poses the greatest storage risk. Comparative Example 9 deviates from the optimal safe range of this invention, with a higher total sugar content, weakening its light food health attributes. The results show that the overall formula design of specific dual-strain fermented pear juice, three kinds of fruit acids and exclusive starch can precisely control the roast duck sauce to a safe range of low sugar and low pH; while the lack of fermented pears, changing the fermentation strains, and replacing the starch will cause pH and water activity to become out of control, which will reduce the preservative ability and is not in line with the positioning of light food products.

[0083] Table 9

[0084] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for preparing roast duck sauce, characterized in that, Includes the following steps: (1) Mix white sugar, salt, yam powder, thyme powder, black pepper powder, and white pepper powder, then add water and white vinegar that accounts for 30-50% of the total mass of white vinegar, and stir to obtain a mixture; (2) Add sweet bean sauce to the mixture in step (1), stir, then add jam and fermented pear juice in sequence, stir, then add concentrated lemon juice, sesame oil and the remaining white vinegar, stir again, then add pea starch and stir to obtain crude roast duck sauce. (3) The crude roast duck sauce prepared in step (2) is ultrasonicated, stirred, filled, degassed and sealed, sterilized and cooled to obtain the finished roast duck sauce; The roast duck sauce, by weight, comprises the following components: 80-120 parts sweet bean sauce, 30-50 parts jam, 30-40 parts white sugar, 4-6 parts salt, 6-9 parts yam powder, 10-16 parts white vinegar, 10-16 parts sesame oil, 4-8 parts concentrated lemon juice, 1-2 parts thyme powder, 0.8-1.2 parts black pepper powder, 0.8-1.2 parts white pepper powder, 16-24 parts pea starch, 4-8 parts fermented pear juice, and 8-12 parts water. The preparation method of fermented pear juice is as follows: Pears are washed, cored, and juiced. After enzyme inactivation treatment, the juice is cooled to obtain pear juice. *Lactobacillus plantarum* and *Saccharomyces boulardii* are inoculated into the pear juice at a live bacteria ratio of 0.8–1.2:1.2–0.8 for fermentation. After fermentation, the juice is filtered to obtain fermented pear juice. The total inoculum size of *Lactobacillus plantarum* and *Saccharomyces boulardii* in the pear juice is 8.0 × 10⁻⁶. 6 ~1.2×10 7 CFU / mL pear juice; Lactobacillus plantarum preservation number DSM 28632; Saccharomyces boulardii preservation number CNCM I-745.

2. The method according to claim 1, characterized in that, The jam is one or more of the following: honey grapefruit jam, apple jam, strawberry jam, and blueberry jam.

3. The method according to claim 1, characterized in that, The fermentation was carried out at 10-15℃ and 10-20 rpm for 42-54 h in anaerobic conditions.

4. The method according to claim 1, characterized in that, The stirring parameters in steps (1) to (3) are 35-45 rpm for 6-12 min.

5. The method according to claim 1, characterized in that, The ultrasound conditions in step (3) are 250~350 W for 2~4 min.

6. The method according to claim 1, characterized in that, The sterilization in step (3) is a two-stage low-temperature sterilization, specifically, first maintaining at 70~78℃ for 8~12 min, and then maintaining at 78~82℃ for 4~6 min.

7. The roast duck sauce prepared by any one of claims 1 to 6.

8. A method for improving the degreasing effect and textural stability of roast duck sauce, characterized in that, Includes the following steps: (1) Mix white sugar, salt, yam powder, thyme powder, black pepper powder, and white pepper powder, then add water and white vinegar that accounts for 30-50% of the total mass of white vinegar, and stir to obtain a mixture; (2) Add sweet bean sauce to the mixture in step (1), stir, then add jam, fermented pear juice, stir, then add concentrated lemon juice, sesame oil, and the remaining white vinegar, stir again, then add pea starch, and stir to obtain crude roast duck sauce. (3) The crude roast duck sauce prepared in step (2) is ultrasonicated, stirred, filled, degassed and sealed, sterilized and cooled to obtain roast duck sauce that is degreasing and has a stable texture. The roast duck sauce, by weight, comprises the following components: 80-120 parts sweet bean sauce, 30-50 parts jam, 30-40 parts white sugar, 4-6 parts salt, 6-9 parts yam powder, 10-16 parts white vinegar, 10-16 parts sesame oil, 4-8 parts concentrated lemon juice, 1-2 parts thyme powder, 0.8-1.2 parts black pepper powder, 0.8-1.2 parts white pepper powder, 16-24 parts pea starch, 4-8 parts fermented pear juice, and 8-12 parts water. The preparation method of fermented pear juice is as follows: Pears are washed, cored, and juiced. After enzyme inactivation treatment, the juice is cooled to obtain pear juice. *Lactobacillus plantarum* and *Saccharomyces boulardii* are inoculated into the pear juice at a live bacteria ratio of 0.8–1.2:1.2–0.8 for fermentation. After fermentation, the juice is filtered to obtain fermented pear juice. The total inoculum size of *Lactobacillus plantarum* and *Saccharomyces boulardii* in the pear juice is 8.0 × 10⁻⁶. 6 ~1.2×10 7 CFU / mL pear juice; Lactobacillus plantarum preservation number DSM 28632; Saccharomyces boulardii preservation number CNCM I-745.

9. The method according to claim 8, characterized in that, The fermentation was carried out at 10-15℃ and 10-20 rpm for 42-54 h in anaerobic conditions.

10. The application of the method according to any one of claims 1 to 6 or claims 8 to 9 in the processing of roasted poultry dipping sauce, mixed noodles and wraps, low-fat light meals, and pre-prepared processed meat products.

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