Frozen instant fruit and preparation method thereof

Abstract

The invention provides a preparation method of frozen instant fruits, which comprises the following steps: A) blanching fresh fruits, and pre-freezing to obtain pre-frozen fruits; b) performing graded freeze drying on the pre-frozen fruits, and removing 10-50% of moisture in the fresh fruits to obtain freeze-dried fresh-locked fruits; and C) freezing and storing the freeze-dried and fresh-locked fruits to obtain the frozen instant fruits. According to the invention, the pain points of traditional freeze-dried fruits and direct frozen fruits are solved, and the internal structure of the fruits is optimized through an ultralow-temperature pre-freezing and vacuum freeze-drying technology. Tiny ice crystals are generated in the fruits through ultralow-temperature quick freezing, the ice crystals sublimate in the drying process, and the interiors of the fruits are loosened. By adjusting the drying process, partial moisture of the fruits is removed, and the taste of the fruits is optimized.

Description

Technical Field

[0001] This invention belongs to the field of food technology, specifically relating to a frozen ready-to-eat fruit and its preparation method. Background Technology

[0002] In recent years, with the continuous advancement of freeze-drying technology, freeze-dried foods have increasingly appeared in our daily lives. Freeze-dried food is short for vacuum freeze-dried food, also known as FD food. Due to this special processing method, the color, aroma, flavor, nutritional components, and appearance of fresh food can be preserved to the greatest extent. In addition to traditional freeze-dried vegetables, freeze-dried fruits have also gained increasing attention in recent years. Freeze-dried fruits are produced by pre-freezing the water inside the fruit using a vacuum freeze dryer, and then sublimating the frozen water in a vacuum environment to obtain freeze-dried fruit. In short, the water inside the fruit is extracted at low temperatures, preserving its original nutrients.

[0003] Existing freeze-dried fruits have an internal moisture content of less than 10%, resulting in a firmer texture and a crispier taste, but lacking the flavor and texture of fresh fruit. However, fresh fruits have a short shelf life, and if they are frozen directly, they cannot be eaten immediately.

[0004] Therefore, providing a ready-to-eat frozen fruit with the texture and flavor of a real fruit has become a problem that needs to be solved. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a frozen ready-to-eat fruit and a preparation method thereof. The frozen ready-to-eat fruit provided by the present invention can be eaten immediately and has the taste and flavor of fruit.

[0006] This invention provides a method for preparing frozen ready-to-eat fruit, comprising the following steps:

[0007] A) Fresh fruit is sterilized and then pre-frozen to obtain pre-frozen fruit;

[0008] B) The pre-frozen fruit is graded and freeze-dried to remove 10% to 50% of the water from the fresh fruit, resulting in freeze-dried fruit with preserved freshness.

[0009] C) Freeze and store the freeze-dried fruit to obtain frozen ready-to-eat fruit.

[0010] Preferably, the fresh fruit is selected from hawthorn, crabapple, and fresh jujube.

[0011] Preferably, the sterilization is selected from blanching or immersion in hypochlorous acid solution;

[0012] The temperature of the hot water treatment is 80-100℃, and the time is 10-60 seconds;

[0013] The concentration of the hypochlorous acid solution is 150–200 ppm.

[0014] Preferably, the pre-freezing involves laying the sterilized fresh fruit flat and then pre-freezing it.

[0015] Preferably, the pre-freezing is ultra-low temperature pre-freezing.

[0016] Preferably, the pre-freezing temperature is -50 to -30°C.

[0017] Preferably, the temperature range for the graded freeze-drying is -50 to 30°C, the total freeze-drying time is 3 to 8 hours, and the vacuum degree is ≤30Pa.

[0018] Preferably, under vacuum conditions, the graded freeze-drying involves freezing at -10 to -30°C for 1 to 2 hours and drying at 10 to 20°C for 3 to 5 hours.

[0019] Preferably, in step C), the freezing temperature is below -18°C.

[0020] The present invention also provides a frozen ready-to-eat fruit prepared by the above preparation method.

[0021] Compared with existing technologies, this invention provides a method for preparing frozen ready-to-eat fruit, comprising the following steps: A) pre-freezing fresh fruit after sterilization to obtain pre-frozen fruit; B) grading and freeze-drying the pre-frozen fruit to remove 10% to 50% of the moisture from the fresh fruit, obtaining freeze-dried fruit with freshness-locking properties; C) freezing and storing the freeze-dried fruit with freshness-locking properties to obtain frozen ready-to-eat fruit. This invention solves the pain points of traditional freeze-dried and directly frozen fruit by optimizing the internal structure of the fruit through ultra-low temperature pre-freezing combined with vacuum freeze-drying technology. Ultra-low temperature rapid freezing causes tiny ice crystals to form inside the fruit, which sublimate during the drying process, making the fruit's interior porous. By adjusting the drying process, some moisture is removed from the fruit, optimizing its taste. Detailed Implementation

[0022] This invention provides a method for preparing frozen ready-to-eat fruit, comprising the following steps:

[0023] A) Fresh fruit is sterilized and then pre-frozen to obtain pre-frozen fruit;

[0024] B) The pre-frozen fruit is graded and freeze-dried to remove 10% to 50% of the water from the fresh fruit, resulting in freeze-dried fruit with preserved freshness.

[0025] C) Freeze and store the freeze-dried fruit to obtain frozen ready-to-eat fruit.

[0026] This invention first selects fresh, high-quality fruits. While there are no specific restrictions on the type of fruit, fruits with high fiber and pectin content are preferred. In this invention, the preferred fresh fruits are hawthorn, crabapple, and fresh jujube.

[0027] Then, after washing the fresh fruit, it is sterilized. The sterilization process is selected from blanching or soaking in hypochlorous acid solution.

[0028] The blanching temperature is 80–100℃, which can be any value between 80, 85, 90, 95, 100℃, or 80–100℃, and the time is 10–60 seconds, which can be any value between 10, 20, 30, 40, 50, 60 seconds, or 10–60 seconds. After blanching, microorganisms on the surface of the fruit can be killed.

[0029] In the process of immersion sterilization with hypochlorous acid solution, the concentration of the hypochlorous acid solution is 150-200 ppm.

[0030] Then, the sterilized fruit is pre-frozen. Specifically, the pre-freezing involves laying the sterilized fresh fruit flat and then pre-freezing it.

[0031] In this invention, fresh fruit can be pre-frozen with or without pits. This invention can preserve the original shape of fresh fruit to the greatest extent possible.

[0032] Next, the laid-out fruit is pre-frozen. The pre-freezing is ultra-low temperature pre-freezing. Preferably, the pre-freezing temperature is -50 to -30°C, which can be any value between -50, -45, -40, -35, -30, or -50 to -30°C.

[0033] This invention uses ultra-low temperature quick-freezing, which can cause tiny ice crystals to form inside the fruit. During the drying process, the ice crystals sublimate, making the inside of the fruit loose.

[0034] Then, the pre-frozen fruit is graded and freeze-dried to remove 10% to 50% of the water content from the fresh fruit, resulting in freeze-dried fruit with preserved freshness.

[0035] In the staged freeze-drying process, the temperature gradient increases gradually, the temperature change range is -50 to 30℃, the total freeze-drying time is 3 to 8 hours, and the vacuum degree is ≤30Pa.

[0036] Specifically, the graded freeze-drying process is as follows: under vacuum conditions, the graded freeze-drying is performed by freezing at -10 to -30°C for 1 to 2 hours and drying at 10 to 20°C for 3 to 5 hours.

[0037] In this invention, the pre-frozen fruit is first frozen at -10 to -30°C for 1 to 2 hours. Under these conditions, the ambient temperature of the freeze dryer is lowered to ensure the product remains frozen. The freezing temperature is -10 to -30°C, and can be any value between -10°C, -15°C, -20°C, -25°C, and -30°C. The freezing time is 1 to 2 hours, and can be any value between 1, 1.5, 2, or 1 to 2 hours.

[0038] Next, the product is dried at 10–20°C for 3–5 hours. This stage is the product dehydration stage. Choosing this drying temperature range significantly shortens the freeze-drying time and ensures product structural stability. The drying temperature is 10–20°C, which can be 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20°C, or any value between 10 and 20°C. The drying time is 3–5 hours, which can be 3, 3.5, 4, 4.5, 5 hours, or any value between 3 and 5 hours.

[0039] Temperature gradients combined with freeze-drying time selectively remove 10% to 50% of the moisture from the pulp, which can be 10%, 12%, 15%, 17%, 20%, 22%, 24%, 25%, 28%, 30%, 32%, 34%, 35%, 37%, 40%, 42%, 45%, 47%, 50%, or any value between 10% and 50%.

[0040] Freeze-drying fruits can retain the beneficial components in the pulp to the greatest extent, extend the shelf life, maintain the color of the pulp, increase the permeability of the pores inside the pulp, and give the pulp a special taste.

[0041] Finally, the freeze-dried fruit is frozen and stored to obtain frozen ready-to-eat fruit. The resulting frozen ready-to-eat fruit has no wrinkles or only slight wrinkles on the skin, which can preserve the shape and taste of the fruit to the greatest extent.

[0042] In this invention, there are no special limitations on the method of cryogenic storage; any cryogenic storage conditions known to those skilled in the art are acceptable. Preferably, the cryogenic storage temperature is below -18°C, and more preferably -18°C to -25°C.

[0043] The method for preparing frozen ready-to-eat fruit provided by this invention solves the problem that fruit cannot be eaten immediately after direct freezing, improves the sensory quality of frozen fruit, and extends the shelf life of fruit.

[0044] This invention addresses the shortcomings of traditional freeze-dried and directly frozen fruits by optimizing the internal structure of the fruit through a combination of ultra-low temperature pre-freezing and vacuum freeze-drying technology. Ultra-low temperature rapid freezing causes tiny ice crystals to form inside the fruit; these crystals sublimate during the drying process, resulting in a more porous fruit interior. By adjusting the drying process, some of the moisture is removed, thus improving the fruit's texture and flavor.

[0045] To further understand the present invention, the following description, in conjunction with embodiments, illustrates a frozen ready-to-eat fruit and its preparation method provided by the present invention. The scope of protection of the present invention is not limited by the following embodiments.

[0046] Example 1

[0047] 1. Fruit selection and sterilization: Select fresh hawthorns that are intact and uniform in size, and blanch them at 80℃ for 60 seconds to kill microorganisms on the surface of the fruit.

[0048] 2. Pre-freezing steps: Lay the fruit flat and pre-freeze it at a temperature of -30℃.

[0049] 3. Freeze-drying step: Graded freeze-drying, under a vacuum degree ≤30Pa, the graded freeze-drying is -20℃ for 1 hour and 20℃ for 3 hours. The temperature gradient is combined with the freeze-drying time to selectively remove 50% of the moisture in the pulp to obtain freeze-dried freshness-locking fruit.

[0050] 4. Freezing storage: Freeze-dried fruits at -18℃ for 24 hours.

[0051] Example 2

[0052] 1. Fruit selection and sterilization: Select fresh hawthorns that are intact and uniform in size, remove the pits and clean them thoroughly. Then soak and wash them in a 150ppm hypochlorous acid solution to kill microorganisms on the surface of the fruit.

[0053] 2. Pre-freezing steps: Lay the fruit flat and pre-freeze it at a temperature of -40℃.

[0054] 3. Freeze-drying step: Graded freeze-drying, under a vacuum degree ≤30Pa, the graded freeze-drying is -20℃ for 1 hour and 10℃ for 5 hours. The temperature gradient is combined with the freeze-drying time to selectively remove 45% of the moisture in the pulp to obtain freeze-dried freshness-locking fruit.

[0055] 4. Freezing storage: Freeze-dried fruits at -18℃ for 24 hours.

[0056] Example 3

[0057] 1. Fruit selection and sterilization: Select fresh hawthorns that are intact and uniform in size, remove the pits and clean them thoroughly. Then soak and wash them in a 150ppm hypochlorous acid solution to kill microorganisms on the surface of the fruit.

[0058] 2. Pre-freezing steps: Lay the fruit flat and pre-freeze it at a temperature of -40℃.

[0059] 3. Freeze-drying step: Graded freeze-drying, under a vacuum degree ≤30Pa, the graded freeze-drying is -20℃ for 1 hour and 15℃ for 4 hours. The temperature gradient is combined with the freeze-drying time to selectively remove 45% of the moisture in the pulp to obtain freeze-dried freshness-locking fruit.

[0060] 4. Freezing storage: Freeze-dried fruits at -18℃ for 24 hours.

[0061] Example 4

[0062] 1. Fruit selection and sterilization: Select fresh crabapples that are intact and uniform in size, remove the pits and clean them thoroughly. Then soak and wash them in a 150ppm hypochlorous acid solution to kill microorganisms on the surface of the fruit.

[0063] 2. Pre-freezing steps: Lay the fruit flat and pre-freeze it at a temperature of -50℃.

[0064] 3. Freeze-drying step: Graded freeze-drying, under a vacuum degree ≤30Pa, the graded freeze-drying is -20℃ for 1 hour and 20℃ for 3 hours. The temperature gradient is combined with the freeze-drying time to selectively remove 50% of the moisture in the pulp to obtain freeze-dried freshness-locking fruit.

[0065] 4. Freezing storage: Freeze-dried fruits at -18℃ for 24 hours.

[0066] Example 5

[0067] 1. Fruit selection and sterilization: Select fresh dates that are intact and uniform in size, remove the pits and clean them thoroughly. Then soak and wash them in a hypochlorous acid solution with a concentration of 150ppm to kill microorganisms on the surface of the fruit.

[0068] 2. Pre-freezing steps: Lay the fruit flat and pre-freeze it at a temperature of -50℃.

[0069] 3. Freeze-drying step: Graded freeze-drying, under a vacuum degree ≤30Pa, the graded freeze-drying is -20℃ for 1 hour and 20℃ for 4 hours. The temperature gradient is combined with the freeze-drying time to selectively remove 40% of the moisture in the pulp to obtain freeze-dried freshness-locking fruit.

[0070] 4. Freezing storage: Freeze-dried fruits at -18℃ for 24 hours.

[0071] Comparative Example 1

[0072] Fresh hawthorns are frozen and stored at -18℃ for 24 hours.

[0073] Comparative Example 2 - Conventional Drying

[0074] 1. Fruit selection and sterilization: Select fresh hawthorns that are intact and uniform in size, remove the pits and clean them thoroughly. Then soak and wash them in a 150ppm hypochlorous acid solution to kill microorganisms on the surface of the fruit.

[0075] 2. Drying: After laying the fruit flat, dry it at 100℃ until 45% of the moisture in the pulp is removed.

[0076] 3. Freezing storage: Freeze the partially dried hawthorns at -18℃ for 24 hours.

[0077] Comparative Example 3 - Freeze-dried Hawthorn

[0078] 1. Fruit selection and sterilization: Select fresh hawthorns that are intact and uniform in size, remove the pits and clean them thoroughly. Then soak and wash them in a 150ppm hypochlorous acid solution to kill microorganisms on the surface of the fruit.

[0079] 2. Pre-freezing steps: Lay the fruit flat and pre-freeze it at a temperature of -40℃.

[0080] 3. Freeze-drying step: Graded freeze-drying, under a vacuum degree ≤30Pa, the graded freeze-drying is -20℃ for 1 hour and -10℃ for 12 hours. The temperature gradient is combined with the freeze-drying time to selectively remove 80% of the water in the pulp to obtain freeze-dried hawthorn.

[0081] Test case

[0082] 1. Nutritional composition determination

[0083] Nutritional components of fresh hawthorn, frozen fruit prepared in Example 1 above, and fresh hawthorn were tested. The specific testing methods are as follows:

[0084] The results are shown in Table 1.

[0085] Table 1. Results of Nutritional Composition Tests

[0086]

[0087] As shown in Table 1, the freeze-drying process is a water evaporation process. After the water evaporates, the nutrients are enriched, the proportion of nutrients per unit weight increases, and the nutrient content increases.

[0088] 2. Stability Test

[0089] The frozen fruits prepared in Examples 1-3 and Comparative Example 1 were subjected to shelf-life testing. The samples were placed in a 30°C constant temperature incubator and incubated at the same temperature. The time of spoilage was recorded as follows:

[0090] The results are shown in Table 2:

[0091] Table 2 Stability Test Results

[0092]

[0093]

[0094] As shown in Table 2, the loss of water in hawthorn reduces the risk of microbial growth, while freezing conditions inhibit microbial growth and extend the shelf life of the product.

[0095] 3. Sensory evaluation test

[0096] Sensory tests, including taste and appearance, were performed on the frozen fruits prepared in Examples 1-3 and Comparative Examples 1-3. Specific scoring criteria are shown in Table 3.

[0097] Table 3 Scoring Criteria

[0098]

[0099] Ten testers were selected to conduct sensory tests on the frozen fruits prepared in Examples 1-3 and Comparative Examples 1-3 according to the scoring criteria in Table 3. The scores of the ten testers were summed, and the results are shown in Table 4.

[0100] Table 4 Sensory Test Results

[0101]

[0102] As shown in Table 4, this product has the advantages of moderate taste under freezing conditions, appearance color close to fresh fruit, moderate sweet and sour taste, and good product shape retention.

[0103] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing frozen ready-to-eat fruit, characterized in that, Includes the following steps: A) Fresh fruit is sterilized and then pre-frozen to obtain pre-frozen fruit; B) The pre-frozen fruit is graded and freeze-dried to remove 10% to 50% of the water from the fresh fruit, resulting in freeze-dried fruit with preserved freshness. C) Freeze and store the freeze-dried fruit to obtain frozen ready-to-eat fruit.

2. The preparation method according to claim 1, characterized in that, The fresh fruits are selected from hawthorn, crabapple, and fresh jujube.

3. The preparation method according to claim 1, characterized in that, The sterilization method is selected from scalding or immersion in hypochlorous acid solution; The temperature of the hot water treatment is 80-100℃, and the time is 10-60 seconds; The concentration of the hypochlorous acid solution is 150–200 ppm.

4. The preparation method according to claim 1, characterized in that, The pre-freezing process involves laying the sterilized fresh fruit flat and then pre-freezing it.

5. The preparation method according to claim 4, characterized in that, The pre-freezing is ultra-low temperature pre-freezing.

6. The preparation method according to claim 1, characterized in that, The pre-freezing temperature is -50 to -30°C.

7. The preparation method according to claim 1, characterized in that, The temperature range for the graded freeze-drying is -50 to 30°C, the total freeze-drying time is 3 to 8 hours, and the vacuum degree is ≤30Pa.

8. The preparation method according to claim 1, characterized in that, Under vacuum conditions, the graded freeze-drying involves freezing at -10 to -30°C for 1 to 2 hours and drying at 10 to 20°C for 3 to 5 hours.

9. The preparation method according to claim 1, characterized in that, In step C), the freezing temperature is below -18°C.

10. A frozen ready-to-eat fruit prepared by the preparation method according to any one of claims 1 to 9.

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