A precise heat sterilization method for instant horse hoof cake directly bagged by partially gelatinized pulp

Abstract

This invention discloses a method for precise heat sterilization of ready-to-eat water chestnut cake that is directly packaged with partially gelatinized slurry. The invention relates to the field of food processing technology; the method includes: (1) mixing raw slurry with sugar water at 80-90℃ at a volume ratio of 1:2.5-3.5 using the slurry mixing method, controlling the starch gelatinization degree at 35-45%, to obtain a partially gelatinized slurry with appropriate consistency; (2) directly injecting it into a PA / RCPP retort bag, controlling the sample thickness at 1.5-2.5cm and the weight at 400g, and vacuum sealing; (3) based on the F0 value threshold of 6min, using one of the process parameters of 115℃×35min, 121℃×20min or 127℃×11.5min for precise heat sterilization, with a heating rate of 1.5-2.0℃ / min, and using the heating stage to complete the remaining gelatinization. This invention solves the technical problems of secondary heating and deterioration in "steaming before packaging", retrogradation and hardening in fully cooked pulp bagging, and uncontrollable gelatinization in fully raw pulp bagging. It achieves integrated gelatinization and sterilization, resulting in a product with uniform texture and good transparency. It achieves commercial sterility after 10 days of storage at 37°C, with a coefficient of variation of texture indicators of <5%.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, specifically relating to a precise heat sterilization method for ready-to-eat water chestnut cake based on a partially gelatinized pulp direct bagging process. Background Technology

[0002] Water chestnut cake, a traditional starch-based food from the Lingnan region, is made primarily from water chestnut starch through processes such as mixing, distillation, and steaming. Due to its rich nutritional content and high water activity, water chestnut cake typically has a shelf life of no more than 14 days at room temperature; heat sterilization is a key method to extend its shelf life.

[0003] In existing technologies, the packaging methods for water chestnut cake are mainly divided into three categories: The first type is the "steam first, then pack" process, which means that the water chestnut cake is steamed until fully cooked (gelatinization degree > 90%), cooled, and then cut and packaged for sterilization. This process has the following defects: (1) The thickness of the steamed cake is difficult to control when it is cut and packed into bags (usually fluctuating by 2-5cm), which leads to inconsistent heat penetration paths during subsequent sterilization, large temperature deviation at the center cold point, and difficulty in accurately controlling the sterilization intensity (F0 value); (2) After undergoing two high-temperature treatments of "steaming + sterilization", the starch is excessively gelatinized or even retrograded, resulting in a soft and mushy texture and loss of elasticity after sterilization (usually elasticity < 0.5), and a serious deterioration in taste; (3) The cutting and packaging process is exposed to the air, which increases the risk of secondary microbial contamination.

[0004] The second type is the "direct bagging of fully cooked pulp" process, which involves first cooking the pulp to a fully cooked state with a gelatinization degree of >90%, then cooling it and directly bagging it (without cutting) before sterilization. Although this process avoids the uneven thickness caused by cutting, it has the following problems: (1) The fully cooked pulp has extremely poor fluidity and is in the form of paste or solid. It is difficult to control the uniformity of thickness when bagging, and it is easy to form air pockets in the bag; (2) The fully cooked pulp is prone to starch retrogradation (aging) during the cooling process, which leads to hardening of texture and decreased transparency after subsequent sterilization; (3) It still needs to undergo two heat treatments of "pre-cooking + sterilization", which wastes energy and the deterioration of texture is inevitable.

[0005] The third type is the "full raw pulp bagging" process, which involves directly filling ungelatinized raw pulp (gelatinization degree ≈ 0%) into bags and then sterilizing them. Although this process avoids secondary heating, it has the drawback of uncontrollable gelatinization: during the heating process in the sterilizer, the gelatinization rate of the raw pulp is greatly affected by the heating rate, the position of the bag, and the initial temperature fluctuations, which can easily lead to insufficient gelatinization (cooked in the center) or excessive gelatinization (soft and mushy edges). In addition, due to the excessive fluidity of the raw pulp, it is difficult to stably control the bag thickness at the standard of 2cm, resulting in poor consistency in industrial production.

[0006] In addition, existing technologies lack precise heat sterilization control standards for the high starch matrix characteristics of water chestnut cake. They mostly rely on empirical temperature-time parameters (such as 121℃×20min) for sterilization, without considering the lag effect of cold point temperature, resulting in the dilemma of "under-sterilization" (storage bag swelling) or "over-sterilization" (texture deterioration).

[0007] Therefore, developing a precise heat sterilization method based on direct bagging of partially gelatinized slurry (gelatinization degree 35-45%), which controls a specific gelatinization degree range to achieve both appropriate consistency (facilitating thickness control and avoiding excessive or insufficient fluidity) and adequate gelatinization space (completing the remaining gelatinization by using sterilization heating), is of great significance for realizing the industrialized and standardized production of ready-to-eat water chestnut cake. Summary of the Invention

[0008] The purpose of this invention is to overcome the technical defects in the prior art, such as the secondary heating deterioration caused by "steaming before packaging", the retrogradation, hardening and poor fluidity caused by "packaging fully cooked pulp", and the uncontrollable gelatinization caused by "packaging fully raw pulp", and to provide a precise heat sterilization method for ready-to-eat water chestnut cake based on direct packaging of partially gelatinized pulp.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A method for precise heat sterilization of ready-to-eat water chestnut cake made by directly packaging partially gelatinized paste, characterized by the following steps: (1) Partial gelatinization pulp preparation stage: The raw pulp liquid and sugar water at 80-90℃ are rapidly mixed at a volume ratio of 1:2.5-3.5 using the slurry-pouring method and then mixed back to control the starch gelatinization degree at 35-45% to obtain a partially gelatinized pulp with appropriate consistency. (2) Direct quantitative bagging stage: inject part of the gelatinized slurry directly into PA / RCPP retort bags, control the sample thickness to be 1.5-2.5cm and the weight to be 380-420g, seal with vacuum degree ≤-0.08MPa and place horizontally in the center of the sterilizer, and control the initial temperature to be 60℃±2℃; (3) Precision heat sterilization stage: Based on the F0 value threshold of 6 min, sterilization is carried out using one of the three sets of process parameters: 115℃×35 min, 121℃×20 min or 127℃×11.5 min. The heating rate is 1.5-2.0℃ / min. The remaining 55-65% of gelatinization is completed during the heating stage. At the same time, the real-time F0 value is calculated by integrating the cold point temperature to ensure that the 6 min threshold is reached. (4) Quality verification stage: Store at 37℃ for 10 days to verify commercial sterility, and conduct texture and sensory evaluation.

[0010] Preferably, in step (1), the specific operation of the slurry-pouring method is as follows: weigh a quantitative amount of sugar water accounting for 25-35% of the total sugar water and heat it to 80-90°C. Quickly pour the remaining raw slurry into this portion of sugar water and stir at 250-350 rpm for 2-3 minutes to obtain a paste. Then pour the paste into the remaining raw slurry and stir at 150-250 rpm for 4-6 minutes to mix thoroughly. Verify the gelatinization degree to be 35-45% using an RVA rapid viscometer.

[0011] Preferably, in step (2), the sample thickness of 2.0 cm is achieved by controlling the sample amount of 400 g per bag and the size of the retort bag to 15 cm × 20 cm (length-to-diameter ratio 7.5:1) to ensure the consistency of the heat penetration path; the initial temperature of 60℃ ± 2℃ is achieved by preheating in a water bath for 10-20 min to ensure the uniformity of the temperature field.

[0012] Preferably, in step (3), the three sets of process parameters are matched based on the same F0 value threshold of 6 min: holding at 115℃ for 35 min, holding at 121℃ for 20 min, and holding at 127℃ for 11.5 min; the cold point temperature integral is calculated using the formula:

[0013] Where T is the real-time temperature of the cold point (°C), Z is the slope constant of the thermal lethality time curve (taken as 10°C), and t is the total sterilization time (min), ensuring that the final F0 value is ≥6min.

[0014] Preferably, in step (3), the heating rate is controlled at 1.5-2.0℃ / min, reverse pressure cooling is adopted, the back pressure is 0.15-0.20MPa, and the cooling rate is 1.0-1.5℃ / min to below 35℃.

[0015] Compared with the prior art, the beneficial effects of the present invention include: 1. A new process for direct bagging of partially gelatinized pulp (35-45% gelatinization degree) has been established. Unlike whole raw pulp (0%) which has excessive fluidity and fully cooked pulp (>90%) which has extremely poor fluidity and is prone to retrogradation, partially gelatinized pulp has moderate viscosity. The thickness after bagging can be stably controlled at 2cm±0.2cm. Furthermore, the remaining gelatinization is completed during the sterilization heating stage, achieving "gelatinization-sterilization integration" and avoiding secondary heating damage caused by pre-steaming or bagging of fully cooked pulp.

[0016] 2. Solves the problem of retrogradation in fully cooked pulp during bagging. Fully cooked pulp (>90%) is prone to starch retrogradation (aging) during cooling and bagging, resulting in decreased transparency and hardening of texture; partially gelatinized pulp (35-45%) completes the remaining gelatinization during sterilization, without the cooling retrogradation process, and the final product has good transparency and soft texture.

[0017] 3. Precise control of bag thickness was achieved. Partially gelatinized pulp is in a paste-like state with fluidity between fully raw and fully cooked pulp. After bagging, the thickness can be stably controlled at 2cm with an aspect ratio of 7.5:1, ensuring a consistent heat penetration path and a cold point temperature lag time of <3min, providing a geometric basis for accurate F-value calculation.

[0018] 4. Achieved synergistic optimization of commercial sterility and texture preservation. Based on the critical threshold of F0=6min, when using a high-temperature short-time process at 127℃ (11.5min), the product elasticity reached 0.72 and cohesion reached 0.78, which was not significantly different from the unsterilized control group (P>0.05), and was significantly better than the process of steaming before filling or fully cooked pulp (elasticity is usually <0.5). Attached Figure Description

[0019] Figure 1 This is a process flow diagram of the precise heat sterilization method for ready-to-eat water chestnut cake of the present invention.

[0020] Figures 2(a), 2(b), and 2(c) show the temperature-time curves at different cold spots and the integral diagram of the F0 value during the sterilization process.

[0021] Figure 3A Radar charts for sensory evaluation of water chestnut cake under different sterilization intensities. Figure 3B Radar chart for sensory evaluation of water chestnut cake under different sterilization conditions. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments.

[0023] Example 1: Mild sterilization mode at 115℃ (1) Preparation of partially gelatinized pulp: Add 1000g of water to 500g of water chestnut flour (passed through a 100-mesh sieve), stir at 200rpm for 10min, and filter through four layers of gauze to obtain raw slurry; mix 300g of trehalose with 1500g of water and heat to 85℃, take 600g (40%) of 85℃ sugar water, quickly pour in the raw slurry, stir at 300rpm for 2min to obtain a paste, then add the remaining raw slurry back in, stir at 200rpm for 5min, and the gelatinization degree is determined to be 40% by RVA.

[0024] (2) Direct quantitative bagging: The above-mentioned gelatinized slurry was directly packed into 15cm×20cm PA / RCPP retort bags, 400g per bag, with a thickness controlled at 2cm. The bags were sealed under vacuum at -0.085MPa and placed horizontally in the center of the sterilizer. The bags were preheated in a 60℃ water bath for 15 minutes, with an initial temperature of 60℃±2℃.

[0025] (3) Precise heat sterilization: The sterilization temperature is set at 115℃, with a heating rate of 1.8℃ / min; after reaching the temperature, it is held for 35 minutes, and the cold point F0 value is calculated simultaneously to reach 6.0 minutes; back pressure cooling (back pressure 0.18MPa) is used, with a cooling rate of 1.2℃ / min to 35℃.

[0026] (4) Quality verification: No bag swelling after 10 days of storage at 37℃; sensory score 8.0 / 9; texture: hardness 815g, elasticity 0.71, cohesion 0.77, good transparency.

[0027] Example 2: 121℃ Standard Equilibrium Mode The difference from Example 1 is that the sterilization temperature is 121℃, the holding time is 20min, the F0 value is 6.0min, and the heating rate is 1.6℃ / min.

[0028] Results: No abnormalities were observed after 10 days of storage at 37℃; sensory score: 7.9 / 9; texture: hardness 805g, elasticity 0.70, cohesion 0.76.

[0029] Example 3: Optimal Short-Term Mode at 127℃ The difference from Example 1 is that the sterilization temperature is 127℃, the holding time is 11.5 min, the heating rate is 2.0℃ / min, and the back pressure is 0.20MPa.

[0030] Results: No abnormalities were observed after 10 days of storage at 37℃; sensory score was 8.5 / 9, which was not significantly different from the unsterilized group (8.6 / 9) (P=0.42); texture: hardness 820g, elasticity 0.72, cohesion 0.78, and transparency was the best, making it the optimal solution.

[0031] Table 1. Effects of different sterilization temperatures on the textural properties of water chestnut cake under F0=6 min conditions.

[0032] Note: Different lowercase letters on the right shoulder of the same column indicate significant differences (P<0.05); texture determination was performed using TPA mode, probe P / 36R, compression ratio 40%, trigger force 5g, and measurement speed 1mm / s; sensory evaluation was conducted by 10 trained evaluators using a 9-point scale.

[0033] Comparative analysis Comparison Example Compare with Example 1 (whole raw pulp bagging group): Prepared according to the method of Example 1, but omitting the heating step of the slurry pouring method, directly using room temperature raw slurry (gelatinization degree ≈ 0%) to bag (400g, 2cm), and sterilized at 127℃ for 11.5min.

[0034] Results: After sterilization, the center was not gelatinized enough (appearing as a white, undercooked substance), while the edges were excessively gelatinized (soft and mushy), resulting in uneven texture. Of the four bags in the same batch, two had a center hardness >1000g (too hard), and two had an edge hardness <500g (too soft). This proves that the gelatinization of whole raw pulp in bags is uncontrollable. Although the thickness can be controlled, the degree of gelatinization is uncontrollable.

[0035] Compare with Example 2 (direct bagging of fully cooked pulp): The raw pulp is fully cooked until the gelatinization degree is >90% (in paste form), cooled to 60℃ and directly packaged (400g, the actual thickness varies by 2-3cm due to poor fluidity), and sterilized at 127℃ for 11.5min.

[0036] Results: (1) It was difficult to fill the bags because the fully cooked pulp was paste-like and difficult to inject into the bags, and it was easy to form air pockets; (2) Retrogradation occurred during the cooling process, the transparency decreased (foggy), the texture hardened after sterilization (hardness > 900g), and the elasticity was only 0.55; (3) Uneven thickness caused the F0 value deviation to be > 20%, and the F0 value of the center of the two bags was only 4.5min (risk of under-sterilization).

[0037] Compare with Example 3 (steam first, then assemble): According to the traditional method: the raw paste is poured into a mold and steamed for 20 minutes until it is completely transparent (gelatinization degree >90%). After cooling to room temperature, it is cut into 2cm thick blocks and then put into a retort bag for sterilization at 121℃ for 30 minutes (estimated F0≈14.5min).

[0038] Results: Although commercial sterility was achieved, after two heating cycles, the elasticity decreased to 0.48 (loss of 36%), the hardness was 580g, the texture was soft and sticky, and the sensory score was 6.2 / 9, which was significantly different from the unsterilized group (P<0.01).

[0039] Control Example 4 (under-sterilization group): The method of Example 1 was followed, but the temperature was maintained at 115°C for only 20 minutes (F0≈3.4min<6min).

[0040] Results: The initial quality was good, but the bag swelled after 7 days of storage at 37℃, and the total number of colonies was >1000 CFU / g, proving that F0=6min is the necessary threshold.

[0041] Table 2. Effects of different sterilization intensities (F0 value) on the textural properties of water chestnut cake.

[0042] Note: Control Example 4 (F0≈3.4min) did not achieve commercial sterility and spoiled after 7 days of storage, so its texture was not measured; the over-sterilization group simulated the over-treatment effect of "steaming first and then packing" with secondary heating.

[0043] Therefore, F0=6min is the critical threshold for ensuring commercial sterility. Below this value, the microbial safety of storage at 37°C for 10 days cannot be guaranteed; while significantly higher than this value (such as F0=12min) will lead to serious deterioration of texture.

[0044] Table 3. Comprehensive comparison of the effects of different packaging processes on the quality of water chestnut cake.

[0045] Conclusion: Only by directly bagging partially gelatinized pulp (35-45%) can we simultaneously achieve convenient bagging operation, precise and controllable thickness, uniform gelatinization, avoidance of retrogradation, and commercial sterility and texture preservation.

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for precise heat sterilization of ready-to-eat water chestnut cake made by directly packaging partially gelatinized paste, comprising the following steps: (1) Preparation of partially gelatinized slurry: The raw slurry is mixed with sugar water at 80-90℃ at a volume ratio of 1:2.5-3.5 by the slurry mixing method and stirred rapidly to control the starch gelatinization degree at 35-45% to obtain a partially gelatinized slurry with appropriate consistency; (2) Direct quantitative bagging: Part of the gelatinized pulp is directly packed into PA / RCPP retort bags, with the sample thickness controlled at 1.5-2.5cm and the weight at 380-420g. After sealing with a vacuum degree ≤-0.08MPa, the bag is placed horizontally in the center of the sterilizer, and the initial temperature is controlled at 60℃±2℃. (3) Precise heat sterilization: Based on the F0 value threshold of 6 min, sterilization is carried out using one of three sets of process parameters: 115℃×35 min, 121℃×20 min or 127℃×11.5 min. The heating rate is 1.5-2.0℃ / min. The remaining 55-65% of gelatinization is completed during the sterilization heating stage. Simultaneously, the real-time F0 value is calculated by integrating the cold point temperature to ensure that the 6 min threshold is reached. (4) Quality verification: Commercial sterility was verified by storing at 37°C for 10 days, and textural and sensory evaluations were conducted.

2. The method for precise heat sterilization of ready-to-eat water chestnut cake directly packaged from partially gelatinized pulp according to claim 1, characterized in that: In step (1), the specific operation of the slurry-pouring method is as follows: Weigh a quantitative amount of sugar water accounting for 25-35% of the total sugar water and heat it to 80-90℃. Quickly pour the remaining raw slurry into this portion of sugar water and stir at 250-350 rpm for 2-3 minutes to obtain a paste. Then pour the paste into the remaining raw slurry and stir at 150-250 rpm for 4-6 minutes to mix thoroughly. Verify the gelatinization degree as 35-45% using an RVA rapid viscometer.

3. The method for precise heat sterilization of ready-to-eat water chestnut cake directly packaged from partially gelatinized pulp according to claim 1, characterized in that: In step (1), the partially gelatinized slurry is different from the raw slurry and the fully cooked slurry. It has a moderate consistency to facilitate the control of the bag thickness and avoids starch retrogradation during the cooling process of the fully cooked slurry.

4. The method for precise heat sterilization of ready-to-eat water chestnut cake directly packaged from partially gelatinized pulp according to claim 1, characterized in that: In step (2), the sample thickness of 2.0cm is achieved by controlling the sample amount of 400g per bag and the size of the retort bag to 15cm×20cm, with an aspect ratio of 7.5:1, to ensure the consistency of the heat penetration path.

5. The method for precise heat sterilization of ready-to-eat water chestnut cake directly packaged from partially gelatinized pulp according to claim 1, characterized in that: In step (2), the initial temperature of 60℃±2℃ is achieved by preheating in a water bath for 10-20 minutes to ensure a uniform temperature field.

6. The method for precise heat sterilization of ready-to-eat water chestnut cake directly packaged from partially gelatinized pulp according to claim 1, characterized in that: In step (3), the three sets of process parameters are matched based on the same F0 value threshold of 6 min: heat preservation at 115℃ for 35 min, heat preservation at 121℃ for 20 min, and heat preservation at 127℃ for 11.5 min, of which 127℃×11.5 min is the optimal process parameter.

7. The method for precise heat sterilization of ready-to-eat water chestnut cake directly packaged from partially gelatinized pulp according to claim 1, characterized in that: In step (3), the integral calculation of the cold point temperature uses the following formula: In the formula, This refers to the sterilization time. This refers to the real-time temperature of the water chestnut cake's cooling point during the sterilization process. For reference temperature, The microbial lethal temperature coefficient is used to ensure that the final F0 value is ≥6 min; In step (3), the heating rate is controlled at 1.5-2.0℃ / min, and reverse pressure cooling is adopted with a back pressure of 0.15-0.20MPa. The cooling rate is 1.0-1.5℃ / min to below 35℃.

8. The method according to any one of claims 1-7, characterized in that, The method is applicable to the industrial production of ready-to-eat water chestnut cake. The coefficient of variation of inter-batch texture index is <5%. The product does not swell or spoil after being stored at 37℃ for 10 days. The sensory score is not significantly different from the unsterilized control group (P>0.05).

9. The method for precise heat sterilization of ready-to-eat water chestnut cake directly packaged from partially gelatinized pulp according to claim 6, characterized in that: When using process parameters of 127℃×11.5min, the product elasticity reaches 0.70-0.75, cohesion reaches 0.75-0.80, and transparency is better than that of fully cooked pulp bagging process. There is no significant difference in texture compared with the unsterilized control group.

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