Food preparation method

Abstract

The present invention mainly provides a food preparation method, in particular a novel puffed food processing strategy, and also a novel freeze-drying-puffing treatment process, which can advantageously treat substantially liquid, high moisture content objects to obtain freeze-dried, puffed products, and which can be used in the field of food processing, such as food processing, food processing, food processing, food processing, food processing, food processing, food processing, food processing, food processing, food processing, food processing, food processing, food processing, food processing, food processing, food processing, food processing and food processing. The nutrition and taste of the raw materials can be fully reserved, and the good effects of flash dissolution in liquid (such as water), flash release in the oral cavity or crisper taste can be achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of freeze drying, and specifically relates to a freeze drying and puffing technology, and more specifically to a method for freeze drying and puffing a fruit and vegetable juice system. Background Art

[0002] Since the British Wollaston first discovered the freeze-drying technology in 1813, the technology has developed rapidly and been widely used in the fields of medicine, food, etc.

[0003] Freeze drying is a drying method that has the least impact on the properties of a substance. It is a process of drying a substance at low temperature and low pressure. It is a stabilized substance drying process that freezes the water-containing substance into a solid state first, and then sublimates the water from the solid state directly into a gaseous state to remove the water and preserve the substance. It is particularly suitable for heat-sensitive substances, which minimizes the loss of volatile components and heat-denatured nutrients and aromatic components in the substance. The growth of microorganisms and the action of enzymes are almost impossible, which can best maintain the original properties of the substance.

[0004] Cited document 1 discloses a vacuum freeze-drying and airflow puffing integrated equipment, which integrates vacuum freeze-drying and airflow puffing, and shares a freeze-drying and puffing integrated tank, a cold trap vacuum integrated tank, a refrigeration unit, and a vacuum unit. A heating and refrigeration integrated partition is provided in the freeze-drying and puffing integrated tank, a refrigeration coil is provided in the cold trap vacuum integrated tank, and a pneumatic valve is provided on the connecting pipe between the freeze-drying and puffing integrated tank and the cold trap vacuum integrated tank.

[0005] Reference document 2 discloses a method for processing fresh golden thread jujube by vacuum freeze drying and puffing, which belongs to the drying of fresh golden thread jujube, comprising the following steps: (1) pretreatment of raw materials; (2) immersing the treated golden thread jujube in a sugar solution with a sugar content of 40% for 8-12 hours, and then draining; (3) spreading the drained golden thread jujube into a single layer, placing it in a quick freezer, and quick freezing it at -40°C; (4) drying by vacuum freeze puffing.

[0006] Reference 3 discloses a vacuum freeze-drying and puffing processing method for figs, comprising the following steps: (1) pre-treating raw materials; (2) spreading the treated raw materials into a single layer, evenly distributing them on a material tray, placing them in a quick freezer, and quick freezing them at -40°C; and (3) performing vacuum freeze-drying and puffing drying in a vacuum freeze-drying and puffing dryer.

[0007] Reference document 4 discloses a freeze-drying method for Bletilla striata, comprising the following steps: 1) pretreatment; 2) prefreezing; 3) vacuum freezing; 4) puffing and drying: adjusting the temperature of the puffing tank to 50°C to 60°C, and then placing the Bletilla striata treated in step 3) into the puffing tank for 10 to 20 minutes, then evacuating the puffing tank and adjusting the temperature in the puffing tank to 30°C to 40°C, and leaving the puffing tank to stand for 2 to 3 hours.

[0008] With the continuous increase in demand, in the years of freeze-drying technology application, the industry has put forward higher and newer requirements for some special products. For example, the product needs a larger loose porous structure than the original volume to achieve flash dissolution in liquid, flash release in the mouth, or a crispier taste. Therefore, there is still room for further improvement in the freeze-drying-puffing process.

[0009] Citations

[0010] Reference 1: CN205878768U

[0011] Reference 2: CN103141559A

[0012] Reference 3: CN103141784A

[0013] Reference 4: CN111998617A Summary of the invention

[0014] Problem that the invention aims to solve

[0015] As far as the current existing technology is concerned, the freeze drying-puffing process is usually used to process fruits and vegetables with a relatively complete solid appearance or other solid or semi-solid extract concentrates, etc., so that the puffed products obtained have a strong crisp taste. For objects that are basically liquid and have a high water content, such as fruit juice, etc., freeze drying is usually used to obtain dry products (such as freeze-dried powder, etc.), and such products often have flexible ways of consumption.

[0016] At present, it is difficult to manufacture puffed products from liquid objects with high water content, and thus make these products have flash dissolution and excellent taste, and the above-mentioned traditional freeze-drying operation methods and process routes are difficult to implement, and there is no report in the prior art. Especially for products with high content of fruit juice as the base, mainly due to the high fructose content in fruit and vegetable juice, after freeze-drying by traditional process, the product has a bad taste such as very sticky in the mouth, sticky to teeth, and difficult to swallow, which is difficult to be accepted by consumers. Therefore, it is necessary to explore new treatment methods or processing techniques.

[0017] More specifically, from the existing public technical data (reference document 1 to reference document 4), vacuum freeze drying and airflow puffing are combined, the cold trap and the puffing tank are connected, the pneumatic valve is opened to quickly release the pressure, and the pressure difference between the two tanks is used for puffing. Although this method can achieve freeze-drying puffing, the puffing process is very intense, and the puffing rate cannot be accurately controlled, which can easily cause insufficient or excessive puffing rate. The appearance of the freeze-dried product is difficult to guarantee, and the quality attributes cannot be uniform and stable, especially when the object to be processed becomes a basically liquid object, this problem will be particularly serious. At the same time, the puffing method provided in reference document 2 generally requires 2-3 identical puffing processes, and the production efficiency is low. Therefore, the existing freeze-drying puffing technology is only applicable to a class of fruits, vegetables, traditional Chinese medicine and other products that have a complete structure, a low moisture content before freeze-drying, and a complete fiber structure after freeze-drying.

[0018] Therefore, in view of the above-mentioned problems existing in the technical practice in this field, the present invention mainly provides a novel freeze-drying-puffing process, which can advantageously be used to process objects that are basically liquid and have a high moisture content to obtain freeze-dried and puffed products, and can not only fully retain the nutritional value and taste of the raw materials, but also achieve the excellent effects of flash dissolution in liquid (such as water), flash release in the mouth, or a crisper taste.

[0019] Solutions for solving problems

[0020] [1] The present invention primarily provides a freeze drying-puffing process for a substantially liquid system, wherein the process comprises:

[0021] A freezing step, wherein the basic liquid system is frozen at a temperature below -20°C to obtain a frozen system;

[0022] The step of drying is to dry the frozen system at a temperature below 20°C and under reduced pressure to obtain a dry system with a moisture content of less than 5% by mass, and an apparent density of the dry system of 0.35 to 0.56 g / cm 3 .

[0023] The step of expanding is to expand the above-mentioned drying system under the conditions of temperature T and pressure P to obtain an expanded product.

[0024] The temperature T is higher than the glass transition temperature Tg of the drying system, and the pressure P is at least lower than the pressure at the end of the drying step.

[0025] [2] The method according to [1], wherein the basic liquid system is a system with substantially uniform composition and has a water content of 90% by mass or less.

[0026] [3] The method according to [1] or [2], wherein the basic liquid system is derived from one or more of the following groups: juice or hydrate of fruit or vegetable substances.

[0027] [4] The method according to any one of [1] to [3], wherein the drying step includes a primary drying step and a secondary drying step, the primary drying step is used to remove free moisture, and the secondary drying step is used to remove bound moisture; the temperature of the secondary drying step is higher than the temperature of the primary drying step.

[0028] [5] The method according to any one of [1] to [4], wherein in the puffing step, the dry system is puffed by boiling expansion under the conditions of the temperature T and the pressure P.

[0029] [6] The method according to any one of [1] to [5], wherein before the freezing step, it also includes a step of sterilizing the basic liquid system.

[0030] [7] The method according to any one of [1] to [6], wherein the pressure in the drying step is below 0.7 mbar.

[0031] [8] The method according to any one of [1] to [7], wherein the temperature T in the puffing step is higher than the temperature at the end of the drying step by at least 10°C.

[0032] [9] The method according to any one of [1] to [8], wherein the temperature T is 30 to 50°C and the pressure P is less than 0.2 mbar.

[0033]

[10] . Furthermore, the present invention also provides a method for preparing food, wherein the method comprises the method described in any one of [1] to [9] above.

[0034] Effects of the Invention

[0035] By implementing the above technical solution, the present invention can achieve the following technical effects:

[0036] 1) The present invention proposes for the first time a freeze-drying-puffing processing method for a system that is basically liquid and has a high water content, and can obtain a novel puffed food.

[0037] 2) The obtained puffed product can not only fully retain the nutrition and taste of the raw materials, but also achieve the excellent effects of flash dissolution in liquid (such as water), flash release in the mouth or crispier taste. Especially for freeze-dried and puffed fruit and vegetable juices, huge honeycomb pores are formed in the product after puffing, and the whole product is spherical, with a crisp taste and melts in the mouth, which is very suitable for young children with imperfect swallowing function. If functional small molecule active ingredients are added, they can be quickly absorbed by sublingual cells, which is very suitable for bedridden and mental patients. At the same time, the product melts in water, and can be completely dissolved into a cup of fresh fruit and vegetable juice within 2 seconds under room temperature water conditions.

[0038] 3) The present invention proposes for the first time to perform low-pressure boiling expansion above the glass transition temperature of the drying system, which is completely different from the principle of compressed airflow expansion in the common freeze-drying puffing in the field. Therefore, the present invention does not require additional equipment such as airflow puffing tanks. In the puffing step, the temperature is raised to above the glass transition temperature (Tg) of the material, and the material quickly changes from the glass state to the highly elastic state (rubber state) and the viscous flow state, so that the material boils and expands under relatively mild conditions to achieve the puffing effect. The technical solution of the present invention creatively reverses the glass transition temperature of the freeze-drying process to achieve the effect of material puffing. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 :A typical process flow diagram of the method of the present invention

[0040] Figure 2 : Comparison of the effects of the embodiments of the present invention and the comparative examples

[0041] Figure 3 : Comparison of the effects of the embodiments of the present invention and the comparative examples

[0042] Figure 4 : Hydrogen proton low-field nuclear magnetic resonance NMR scanning diagram of the products of the embodiments of the present invention and the comparative examples DETAILED DESCRIPTION

[0043] The following is a detailed description of the present invention. The following description of the technical features is based on representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples. It should be noted that:

[0044] Unless otherwise stated, the units used in this specification are all international standard units, and the numerical values ​​and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production.

[0045] In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints numerical values ​​A and B.

[0046] In the present specification, a numerical range expressed using "above" or "below" means a numerical range including the number.

[0047] In this specification, the word "may" means both performing a certain process and not performing a certain process.

[0048] In this specification, the use of "optional" or "optional" indicates that certain substances, components, execution steps, application conditions and other factors are used or not used.

[0049] In this specification, the "normal temperature" or "room temperature" used means an indoor ambient temperature of "23±2°C".

[0050] In this specification, the unit names used are all international standard unit names, and unless otherwise stated, the "%" used indicates weight or mass percentage.

[0051] In the present specification, the use of “substantially” or “essentially” means that the standard deviation from a theoretical model, theoretical data or target data is within a numerical range of 3%, preferably 2%, and more preferably 1%.

[0052] In this specification, the terms "expansion" and "puffing" have the same technical meaning unless otherwise specified.

[0053] In this specification, when the terms “include” and / or “comprise” are used, they indicate the existence of features, steps, operations, devices, components and / or their combinations.

[0054] In this specification, the references to "some specific / preferred embodiments", "other specific / preferred embodiments", "embodiments", etc., mean that the specific elements (e.g., features, structures, properties and / or characteristics) described in connection with the embodiments are included in at least one embodiment described herein, and may or may not exist in other embodiments. In addition, it should be understood that the elements may be combined in various embodiments in any suitable manner.

[0055] The present invention proposes for the first time a freeze-drying-puffing method for a basically liquid system with a high water content, which solves the problem that such materials can only be prepared by freeze-drying, resulting in poor taste and difficulty in swallowing when eaten. Therefore, the technical solution of the present invention is a new strategy for food processing technology.

[0056] The present invention is mainly based on the following insights:

[0057] As mentioned above, for a system that is basically liquid and has a high moisture content, the usual processing method is, for example, freeze drying to obtain a block, granular or powdered product, which has long been considered a natural way to dry the above system. In addition, for the expansion processing method, the volume of the material is mainly expanded by, for example, the injection of compressed air, and in this process, for the stability of the process and the uniformity of product quality, it is usually carefully controlled so that the material only changes in volume under the effect of the change in airflow pressure (without introducing other factors).

[0058] However, when the inventors of the present invention used freeze drying to treat a system that is basically liquid and has a high moisture content, they unexpectedly found that under certain conditions, if the temperature unexpectedly rises, the system to be treated exhibits a "boiling" phenomenon. Based on this, through in-depth research, it was further discovered that when the moisture is removed at the end of the freeze drying stage, the temperature is raised to above the glass transition temperature of the material while controlling the material system to have a certain apparent density, and the material can be boiled under the cooperation of pressure, so that the material can be significantly expanded without the need for an additional compressed air flow step, thereby obtaining an expanded product.

[0059] Based on this, a new strategy for freeze drying and puffing of a basic liquid system is formed. The processing method of the present invention mainly includes: a freezing step, a drying step, and a puffing step. The following will specifically describe each element or step:

[0060] (Processing object)

[0061] The processing object of the present invention is mainly aimed at the basic liquid system which is generally considered to be unable to be directly subjected to freeze drying-puffing treatment.

[0062] For the basic liquid system of the present invention, it means that the system basically presents the physical characteristics of a liquid. And preferably, for such a system, the distribution of its internal components is substantially uniform. In addition, for the above-mentioned basic liquid system, it generally has a higher water content. In some specific embodiments, the water content in the system can be 70% by mass or more, preferably 75% by mass or more, and more preferably 80% by mass or more. There is usually no particular restriction on the upper limit of the water content in the system. From the perspective of easy acquisition and subsequent operation, the water content can be 90% by mass or less, preferably 88% by mass or less, and more preferably 85% by mass or less.

[0063] Furthermore, for the basic liquid system described in the present invention, in some specific embodiments, the system can be a substantial solution system, for example, a substantial aqueous solution system; in some other specific embodiments, the system can be a substantial (micro)emulsion system, which uses the aqueous phase as the continuous phase and the oil phase is uniformly and stably dispersed in the continuous phase in the form of tiny droplets, so that visually it can be considered that the oil phase is "dissolved" by the aqueous phase.

[0064] In addition, for the above-mentioned basic liquid system, in some specific embodiments, the presence of a small amount of insoluble solid matter is also allowed. Preferably, the content of such insoluble solid matter in the system can be less than 2% by mass, preferably less than 1% by mass.

[0065] In addition, there is no particular limitation on the source of the basic liquid system of the present invention in principle. It can be the juice or hydrate of fruit or vegetable substances, or the hydrated processed products of various plants (and their water extracts) from instant food sources.

[0066] In some specific embodiments of the present invention, the above-mentioned fruits are not particularly limited in principle, and examples thereof include apples, crab apples, papaya crabapples, aronia berries, loquats, hawthorns, hawthorns, pears (fragrant pears, snow pears, etc.), quince, rose hips, apricots, cherries, peaches (peach, nectarine, flat peach, etc.), plums, plums (green plums), European plums, white jade cherries, blackberries, raspberries, Dahurian raspberries, loganberries, white berries, strawberries, pineapple berries, citrus, October oranges, oranges, lemons, limes, pomelo, kumquats, grapefruits, citrons, bergamots, finger limes, yellow peels, watermelons, cantaloupes, melons, honeydew melons, thorny melons, scabies, bananas, plantains, red bananas, dates, grapes, raisins, blueberries, cranberries, lingonberries, black rice Fruit, mango, Chinese kiwi, yellow kiwi, soft kiwi, red kiwi, pineapple, pineapple, bayberry, persimmon, juniper fruit, black persimmon, papaya, mulberry, fig, jackfruit, paper mulberry fruit, milk fruit, dragon fruit, yellow dragon fruit, Costa Rican cypress, cactus fruit, litchi, longan, rambutan, durian, baobab (fruit of the baobab tree), Oxalidaceae, carambola, trifoliate orange, pomegranate, coconut, date palm, snake skin fruit, acai berry, mangosteen, syrup apple, jaboticaba, guava, Philippine oil fruit, red fruit, passion fruit (passion fruit / passion fruit / egg fruit), avocado, sugar apple, ox heart fruit (ox heart sugar apple), wolfberry, melon eggplant, lantern fruit, cherry tomato, sea buckthorn, milk fruit, etc.

[0067] In principle, there are no special restrictions on the above-mentioned vegetables, including: melons, green leafy vegetables, eggplants, cabbages, tubers, true roots, kale, legumes, perennial lettuces, aquatic lettuces, etc. Furthermore, the vegetables that can be specifically listed include: radish, turnip, cabbage (including Chinese cabbage and cabbage subspecies), cabbage (including cabbage, kohlrabi, cauliflower, broccoli and other varieties), mustard (including root mustard and Chinese mustard varieties), celery, carrot, tomato, cucumber, zucchini, pumpkin, winter squash, winter melon, loofah, gourd, bitter melon, chayote, beans (including dwarf beans and creeping beans varieties), cowpea, pea, broad bean, edamame (i.e. soybean), lentil, sword bean, peanut bean, mung bean, asparagus, lily, spinach, radish, carrot, burdock, yam bean, sweet potato, kudzu, lettuce, wild rice stem, stem mustard, kohlrabi (kohlrabi), Chinese cabbage, etc.

[0068] For the above-mentioned fruits or vegetables, the basic liquid system of the present invention can be formed by obtaining juice. In principle, there is no particular limitation on the method of obtaining the juice, and the juice can be obtained by squeezing or the like. Optionally, the solid insoluble matter can be further removed by solid-liquid separation or the like. In addition, for the juice obtained in this way, the content of water or other components therein can also be controlled by adjusting the components.

[0069] For the above-mentioned fruits or vegetables, the basic liquid system of the present invention can also be obtained by a hydration method. For such a method, it can be typically carried out by water extraction, for example, the fruits or vegetables are crushed, water is added, and stirred with or without heating, and then the solid insoluble matter is filtered to obtain a water extraction system. Similarly, for such a water extraction system, the content of water or other components therein can also be controlled by adjusting the components.

[0070] The basic liquid system obtained by the above method of the present invention may contain carbohydrates, proteins, fats / oils, vitamins, natural pigments or minerals as its main components in addition to water.

[0071] In some specific embodiments, for the basic liquid system of the present invention, from the perspective of excellent taste and morphology of the final product, the carbohydrate content therein is generally 15% by mass or less, preferably 3-15% by mass, and more preferably 5-13% by mass. Further, the total solid content of the basic liquid system may generally be 30% by mass or less, for example, 10-25% by mass, 12-20% by mass.

[0072] In addition, there is no particular limitation on other methods for obtaining the basic liquid system of the present invention. In some specific embodiments, the basic liquid system can be obtained by re-dissolving the extracted water-soluble solid matter of fruits or vegetables and mixing it with water. At the same time, such a re-dissolution method is also suitable for the processed products of various plants derived from the instant food mentioned above, such as coffee.

[0073] Furthermore, for the above-mentioned basic liquid system of the present invention, additional nutritional ingredients or food additives may be added according to the requirements of the final product when necessary. Preferably, these ingredients are soluble ingredients.

[0074] These additional added ingredients may include one or more of carbohydrates, fats, minerals, trace elements and vitamins permitted within the scope of laws and regulations.

[0075] In principle, there is no particular restriction on the types of additional carbohydrates, which can mainly include monosaccharides, oligosaccharides (disaccharides) and polysaccharides. Examples include: monosaccharides represented by glucose, fructose, galactose, etc.; oligosaccharides (disaccharides) represented by maltose, sucrose and lactose, etc.; polysaccharides represented by starch, digestible dextrin, dietary fiber (resistant dextrin, cellulose, oligofructose, oligogalactose, inulin, polyfructose, polydextrose, etc.).

[0076] In principle, there is no particular limitation on the additional fats and oils. Various commercially available conventional vegetable fats and oils, animal fats and oils, or mixtures thereof in any proportions can be used.

[0077] Among them, for the vegetable oils that can be used, in some specific embodiments of the present invention, the following can be listed: rice oil, sunflower seed oil, palm oil, palm kernel oil, peanut oil, rapeseed oil, soybean oil, linseed oil, cottonseed oil, safflower seed oil, perilla seed oil, tea seed oil, hemp seed oil, jojoba oil, olive oil, cocoa bean oil, Chinese tallow seed oil, almond oil, apricot kernel oil, tung seed oil, rubber seed oil, corn germ oil, wheat germ oil, sesame seed oil, evening primrose seed oil, hazelnut oil, pumpkin seed oil, walnut oil, grape seed oil, sesame seed oil, borage seed oil, sea buckthorn seed oil, tomato seed oil, macadamia nut oil and coconut oil.

[0078] Other animal fats that can be used include butter, lard, mutton fat, chicken wine, fish oil, seal oil, whale oil, dolphin oil, oyster oil or lanolin.

[0079] For additional vitamins, they can be determined according to the functional requirements of the actual target product. In some specific embodiments of the present invention, the types of vitamins that can be specifically listed include: one or more of vitamin A, β-carotene, vitamin D (D3), vitamin E, vitamin K (K1), vitamin B1, vitamin B2, vitamin B6, vitamin B12, vitamin C, pantothenic acid, folic acid, niacin, choline, inositol, biotin, and taurine. For these substances, the water-soluble vitamins can be used in the form of aqueous solutions, and the oil-soluble vitamins can be dissolved in the oils and fats mentioned above for use.

[0080] Additional minerals or trace elements include one or more of calcium, phosphorus, potassium, sodium, magnesium, chlorine, copper, selenium, iodine, iron, zinc, manganese, chromium, molybdenum, etc. These minerals or trace elements can be used in the form of solid salts, solutions, suspensions or emulsions.

[0081] As for additional food additives, the following may be cited: sweeteners (xylitol, erythritol, steviol glycosides, acesulfame potassium), food colorings, flavoring agents, stabilizers, antioxidants, etc.

[0082] Furthermore, the basic liquid system of the present invention may be derived from a single fruit or vegetable, or may be a mixed system derived from multiple fruits and vegetables.

[0083] (Pre-processing steps)

[0084] After obtaining the above basic liquid system, it can be optionally treated by conventional pre-treatment means in the art. Typical treatment means may include sterilization / sterilization treatment.

[0085] In principle, there is no particular limitation on such means. For example, it can be carried out by ultraviolet or pasteurization. From the perspective of fully retaining nutrients, pasteurization is preferably used.

[0086] A typical sterilization method may include inputting the liquid material into a preheater and then sterilizing it at a temperature of about 85 to 95° C. for 15 to 25 seconds.

[0087] The material obtained in the pre-treatment step can be cooled to below room temperature for subsequent treatment.

[0088] (Cooling Step)

[0089] The cooling step of the present invention is a step of deep freezing the above-mentioned basic liquid system to obtain a frozen system for subsequent drying.

[0090] As for the cooling temperature in the cooling step, the basic liquid system can usually be frozen to below -20°C, preferably, -25°C to -50°C, and more preferably, -30°C to -45°C.

[0091] In principle, there is no particular restriction on the cooling rate during cooling. For example, the temperature can be reduced at a rate of 1 to 10°C / min. If the temperature is reduced too quickly, the shape of the frozen product may be destroyed, which is not conducive to the control of the shape of the final product. If the temperature is reduced too slowly, it may also lead to too long an operation time or segregation of components.

[0092] In some preferred embodiments of the present invention, the freezing step can be performed by freezing in stages. For example, the material is frozen to below -35°C in the first stage, frozen in the temperature range of -20°C to -30°C in the second stage, and frozen again to below -35°C in the third stage. The freezing in stages can make the frozen system have a better morphology and uniform composition.

[0093] (Drying Step)

[0094] In the drying step of the present invention, the water in the freezing system is mainly removed by reducing the pressure. This process mainly removes the water in the freezing system by low-pressure sublimation.

[0095] The water in the freezing system can be roughly divided into free water and bound water (non-free water) according to its existence mode, wherein the latter is bound to other components in the system by van der Waals forces and hydrogen bonds. Therefore, from the perspective of water removal effect, the drying step of the present invention can be carried out in a staged drying manner.

[0096] In some specific embodiments, the drying step may be performed in two stages: primary drying and secondary drying. The primary drying mainly removes free water by sublimation, while the secondary drying mainly removes bound water that is more difficult to remove by further sublimation.

[0097] For the primary drying step, it can be carried out under a pressure of 0.1 to 0.7 mbar and a temperature below 10°C. Similarly, such a drying step can also be carried out in stages, by adjusting the pressure and temperature to more fully remove free water. In some preferred embodiments, the pressure in different stages can be adjusted in the range of 0.15 to 0.25 mbar, 0.25 to 0.35 mbar, 0.35 to 0.55 mbar and 0.55 to 0.70 mbar. At the same time, in the drying step, the temperature can be gradually increased, for example, from -25°C to below 10°C to fully remove free water.

[0098] Furthermore, as a result of primary drying, the moisture content of the obtained material is usually no more than 8% by mass, for example, 5% to 7% by mass.

[0099] For the secondary drying, from the perspective of advantageous removal of bound water, it can be carried out at a higher temperature than the primary drying. In some preferred embodiments, the temperature during the secondary drying can be 10° C. to 20° C., preferably 12° C. to 16° C. In addition, the pressure during the secondary drying can be the same as or close to the pressure during the primary drying, preferably 0.2 to 0.4 mbar.

[0100] As a result of the secondary drying, the moisture content of the obtained material usually does not exceed 5% by mass, for example, 3% to 5% by mass.

[0101] Furthermore, for the drying step of the present invention, the apparent density of the obtained dried system (dried product) is important, and a suitable apparent density can enable the subsequent expansion treatment to obtain good expandability.

[0102] In some specific embodiments of the present invention, the apparent density of the dry system may be 0.35 to 0.56 g / cm 3 , preferably 0.38 to 0.55 g / cm 3 , more preferably 0.40 to 0.52 g / cm 3 If the apparent density is too small, it means that the drying system is too loose, and it may be difficult to control the conditions in the subsequent expansion process to obtain a product with a good appearance, or the process may fail due to excessive expansion; if the apparent density is too large, it means that the drying system is too tight, and it may be difficult to obtain a well-expanded product in the subsequent expansion process.

[0103] (Puffing steps)

[0104] The puffing step of the present invention is to adjust the temperature T and the pressure P so as to expand the above-mentioned drying system to obtain the final puffed product.

[0105] Different from the previous puffing step that requires the assistance of compressed air flow for puffing, the present invention proposes a new puffing strategy for the first time, which controls the puffing temperature T to be higher than the glass transition temperature Tg of the drying system, and controls the puffing pressure P to be at least lower than the pressure at the end of the drying step, so that the processed material can experience the physical phenomenon of "boiling", and through this mechanism, puffed products can be conveniently obtained under relatively mild conditions.

[0106] The glass transition temperature Tg of a material is a phase transition temperature from a glassy state to a viscoelastic state. The glass transition temperature of a system changes with the change of its components. For example, during the drying process, the glass transition temperature of the material changes with the change of its moisture content. Therefore, before the expansion process, the glass transition temperature Tg of the drying system can be tested and determined.

[0107] The glass transition temperature Tg of the material of the present invention can be determined by conventional methods in the art, such as DSC testing method.

[0108] Furthermore, in some preferred embodiments of the present invention, from the perspective of puffing effect, the temperature T may be higher than the temperature at the end of the drying step by more than 10°C, and more preferably, the temperature T may be 30°C to 50°C; and the pressure P may be below 0.2 mbar, for example, 0 to 0.15 mbar. By using a lower pressure, a suitable "boiling" effect can be ensured.

[0109] In some preferred embodiments, the process of heating the material from the temperature at the end of the drying step to T can be carried out at a faster heating rate, for example, 5 to 20° C. / min, preferably, 8 to 18° C. / min.

[0110] In addition, in some other preferred embodiments, the temperature and pressure can be adjusted in stages during the puffing step, which mainly depends on the characteristics of the material itself and the requirements of the final product.

[0111] (Other steps)

[0112] After the above-mentioned puffing step, the puffed product of the present invention can be obtained. After cooling to room temperature, the puffed product can be packaged through subsequent optional treatments.

[0113] (Morphological characteristics)

[0114] Furthermore, the final product obtained by the puffing step of the present invention may have a honeycomb-like surface porous structure. In some specific embodiments, the puffed product has a surface porous structure of 0.32 g / cm 3 The following apparent density, preferably 0.30 g / cm 3 The apparent density is preferably 0.28 g / cm 3 Below, for example 0.25g / cm 3 Below, 0.25g / cm 3The following apparent density, and there is no particular limit on the lower limit of the apparent density, which is determined by the process equipment and the properties of the product itself; in other specific embodiments, the puffed product has a texture hardness of 200 to 400 g, preferably a texture hardness of 250 to 350 g, through which the product can have a good shape retention ability during the preparation and packaging process. The following texture analysis is used in the present invention to detect the above texture hardness:

[0115] At room temperature (25°C), the texture of the samples was analyzed using a texture analyzer with a probe model of 3PB. A bending fixture was used to evaluate the texture of the samples. The trigger force was 5, the test distance was 20, the pre-speed was 3.0, the test speed was 1, and the post-speed was 5.0 / s.

[0116] In addition, the puffed product obtained by the present invention not only has a crispy mouthfeel, but also has a good flash dissolving effect, and is particularly conducive to swallowing.

[0117] The water solubility (flash dissolution) of the puffed product of the present invention may be a dissolution time of 0.5 to 2 seconds obtained according to the following water solubility test method.

[0118] The water solubility test method is as follows:

[0119] Add 100mL of water at 25℃ into a 200mL beaker, place 10g of sample into the beaker, let it stand and observe. The dissolution time is when the sample is completely dissolved.

[0120] (Typical process flow)

[0121] See also Figure 1 , which gives a typical process flow diagram. Among them:

[0122] 1) Raw material acceptance: After the raw materials arrive at the factory, samples are taken and inspected according to the quality inspection plan. After the indicators are qualified, the laboratory will issue an inspection report;

[0123] 2) Ingredients: Start the seasoning program, and add the fruit and vegetable juices pumped into the storage tank into the ingredient tank according to the proportion, wherein the raw materials include but are not limited to: apple juice, pear juice, orange juice, sea buckthorn juice, blueberry juice, melon juice, potato juice, cauliflower juice, zucchini juice, wax gourd juice, bean juice, sweet corn juice, spinach juice, white onion juice, carrot juice, pumpkin juice, broccoli juice, green bean juice, green cabbage juice, cucumber juice, tomato juice, green eggplant juice, kohlrabi juice, mushroom juice, shiitake juice, hericium erinaceus juice, hazel mushroom juice, white fungus juice, soy milk, fructose syrup, the carbohydrate content of the mixed fruit and vegetable juice is 4.0-13.5%, the solid content is 12-25%, the mixing time is controlled at 5-8 minutes, and the mixing temperature is 35-45° C.;

[0124] 3) Steam jet sterilization: The material is pumped from the mixing temporary storage tank into the preheater, the preheater temperature is 65-70°C, and then pumped from the preheater into the sterilizer and insulation pipe for sterilization, the sterilization temperature is 88-92°C, the time is 15-24s. Steam jet sterilization is to spray clean steam directly into the material and quickly heat it up. This heating method and conditions can reduce the denaturation damage of plant protein and reduce protein agglomeration;

[0125] 4) Cooling: After sterilization, the material is cooled to 2-10°C through a plate heat exchanger for temporary storage;

[0126] 5) Freezing: The material is pumped into the material plate layer (whole plate aluminum foil mold (bottom film)) of the freeze dryer, the first stage freezing temperature is -45 to -35°C, the setting time is 55 to 65 minutes, and the duration is 50 to 70 minutes. The second stage freezing temperature is -30 to -20°C, the setting time is 55 to 65 minutes, and the duration is 50 to 70 minutes. The third stage freezing temperature is -45 to -35°C, the setting time is 55 to 65 minutes, and the duration is 110 to 130 minutes. (In the freezing described in step 5, nuts, chocolate blocks or shaped dried fruits can be pre-placed in the material plate layer (whole plate aluminum foil mold (bottom film)) to give the final product a richer taste)

[0127] 6) Primary drying: the first stage sublimation temperature is -20~-10℃, the setting time is 80~100min, the duration is 20~40min, and the vacuum pressure is controlled at 0.25-0.35mbar; the second stage sublimation temperature is 0~4℃, the setting time is 55~65min, the duration is 80~100min, and the vacuum pressure is controlled at 0.55-0.65mbar; the third stage sublimation temperature is 0~4℃, the setting time is 1~10min, the duration is 160~200min, and the vacuum pressure is controlled at 0.15-0.25mbar; the fourth stage sublimation temperature is 4~8℃, the setting time is 20~40min, the duration is 200~280min, and the vacuum pressure is controlled at 0.15-0.25mbar;

[0128] 7) Secondary drying: drying temperature 10-15°C, setting time 20-60min, duration 120-180min, control vacuum pressure 0.25-0.35mbar;

[0129] 8) Puffing: The first stage puffing temperature is 30-50°C, the setting time is 1-10min, the duration is 120-180min, and the vacuum pressure is controlled at 0.05-0.15mbar. The second stage puffing temperature is 30-50°C, the setting time is 1-10min, the duration is 40-60min, and the vacuum pressure is controlled at 0-0.05mbar. This step raises the temperature to above the glass transition temperature (Tg) of the material, and the material quickly changes from the glass state to the high elastic state (rubber state) and the viscous flow state. Then, by adjusting the temperature and time, the material is boiled and expanded under relatively mild conditions to achieve the puffing effect;

[0130] 9) Cooling: temperature 20-25°C, duration 40-60 minutes;

[0131] 10) Discharging: The board layer is automatically discharged and sent to the packaging machine;

[0132] 11) Nitrogen-filled blister packaging: The whole aluminum foil mold (bottom film) is transferred to the film sealing machine for thermoplastic film sealing (top film), and the freeze-dried puffed fruit and vegetable juice products are blister-sealed in a nitrogen-filled environment;

[0133] 12) X-ray machine foreign body detection: The product passes through the X-ray machine for foreign body detection;

[0134] 13) Coding and packing: After sealing, the products are cut, coded, packed, palletized and finally put into storage.

[0135] (Food Preparation Method)

[0136] Furthermore, the present invention also provides a method for preparing a food, which contains or uses the above-mentioned puffed product. Therefore, the food preparation method includes the above-mentioned freeze-drying-puffing processing method of the present invention, and optionally includes any other food processing steps in the art.

[0137] Example

[0138] The embodiments of the present invention will be described in detail below in conjunction with the examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific conditions are specified in the examples, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0139] Example 1 :

[0140] 1. Raw material acceptance: After the raw materials arrive at the factory, samples are taken and inspected according to the quality inspection plan. After the indicators are qualified, the laboratory will issue an inspection report;

[0141] 2. Ingredients: Start the seasoning program, and add the fruit and vegetable juice pumped into the storage tank into the ingredient tank according to the proportion. The raw materials are: apple juice, pear juice, melon juice, potato juice, sweet corn juice, carrot juice, pumpkin juice, green eggplant juice, soy milk, fructose syrup. The carbohydrate content of the mixed fruit and vegetable juice is 8.5%, the solid content is 22%, the mixing time is controlled at 6 minutes, and the mixing temperature is 40°C;

[0142] 3. Steam jet sterilization: The material is pumped from the mixing temporary storage tank into the preheater, the preheater temperature is 68°C, and then pumped from the preheater into the sterilizer and insulation pipe for sterilization, the sterilization temperature is 90°C, and the time is 15s;

[0143] 4. Cooling: After sterilization, the material is cooled to 2-10℃ through a plate heat exchanger for temporary storage;

[0144] 5. Freezing: The material is pumped into the material plate layer (whole plate aluminum foil mold (bottom film)) of the freeze dryer. The first stage freezing temperature is -40°C, the setting time is 60 minutes, and the duration is 60 minutes. The second stage freezing temperature is -25°C, the setting time is 60 minutes, and the duration is 60 minutes. The third stage freezing temperature is -40°C, the setting time is 60 minutes, and the duration is 120 minutes.

[0145] 6. Primary drying: the first stage sublimation temperature is -15°C, the setting time is 90min, the duration is 30min, and the vacuum pressure is controlled at 0.3mbar; the second stage sublimation temperature is 2°C, the setting time is 60min, the duration is 90min, and the vacuum pressure is controlled at 0.6mbar; the third stage sublimation temperature is 2°C, the setting time is 1min, the duration is 180min, and the vacuum pressure is controlled at 0.2mbar; the fourth stage sublimation temperature is 5°C, the setting time is 30min, the duration is 240min, and the vacuum pressure is controlled at 0.2mbar;

[0146] 7. Secondary drying: The secondary drying temperature is 12°C, the setting time is 40 minutes, the duration is 160 minutes, and the vacuum pressure is controlled at 0.3 mbar to obtain a drying system;

[0147] 8. Puffing: The first stage puffing temperature is 40℃, the setting time is 1min, the duration is 140min, and the vacuum pressure is controlled at 0.1mbar. The second stage puffing temperature is 40℃, the setting time is 1min, the duration is 50min, and the vacuum pressure is controlled at 0mbar.

[0148] 9. Cooling: temperature 23℃, duration 50min;

[0149] 10. Discharging: The board layer is automatically discharged and sent to the packaging machine;

[0150] 11. Nitrogen-filled blister packaging: The whole plate of aluminum foil mold (bottom film) is transferred to the film sealing machine for thermoplastic film sealing (top film), and the freeze-dried puffed fruit and vegetable juice products are blister-sealed in a nitrogen-filled environment;

[0151] 12. X-ray machine foreign body detection: The product passes through the X-ray machine for foreign body detection;

[0152] 13. Coding and packing: After sealing, the products are cut, coded, packed, palletized and finally put into storage.

[0153] Example 2 :

[0154] 1. Raw material acceptance: After the raw materials arrive at the factory, samples are taken and inspected according to the quality inspection plan. After the indicators are qualified, the laboratory will issue an inspection report;

[0155] 2. Ingredients: Start the seasoning program, and pour the fruit and vegetable juice pumped into the storage tank into the ingredient tank according to the proportion. The raw materials include but are not limited to: apple juice, pear juice, zucchini juice, wax gourd juice, bean juice, spinach juice, broccoli juice, green bean juice, green cabbage juice, green eggplant juice, mushroom juice, soy milk, fructose syrup. The carbohydrate content of the mixed fruit and vegetable juice is 6.5%, the solid content is 12%, the mixing time is controlled at 8 minutes, and the mixing temperature is 45°C;

[0156] 3. Steam jet sterilization: The material is pumped from the mixing temporary storage tank into the preheater, the preheater temperature is 70°C, and then pumped from the preheater into the sterilizer and insulation pipe for sterilization, the sterilization temperature is 92°C, and the time is 15s;

[0157] 4. Cooling: After sterilization, the material is cooled to 2-10℃ through a plate heat exchanger for temporary storage;

[0158] 5. Freezing: The material is pumped into the material plate layer (whole plate aluminum foil mold (bottom film)) of the freeze dryer. The first stage freezing temperature is -45°C, the setting time is 55min, and the duration is 50min. The second stage freezing temperature is -30°C, the setting time is 55min, and the duration is 5min. The third stage freezing temperature is -45°C, the setting time is 55min, and the duration is 110min.

[0159] 6. Primary drying: the first stage sublimation temperature is -20℃, the setting time is 80min, the duration is 20min, and the vacuum pressure is controlled at 0.25mbar; the second stage sublimation temperature is 0℃, the setting time is 55min, the duration is 80min, and the vacuum pressure is controlled at 0.55mbar; the third stage sublimation temperature is 0℃, the setting time is 1min, the duration is 160min, and the vacuum pressure is controlled at 0.15mbar; the fourth stage sublimation temperature is 4℃, the setting time is 20min, the duration is 200min, and the vacuum pressure is controlled at 0.15mbar;

[0160] 7. Secondary drying: The secondary drying temperature is 10°C, the setting time is 20 minutes, the duration is 120 minutes, and the vacuum pressure is controlled at 0.25 mbar to obtain a drying system;

[0161] 8. Puffing: The first stage puffing temperature is 30℃, the setting time is 1min, the duration is 120min, and the vacuum pressure is controlled at 0.05mbar. The second stage puffing temperature is 30℃, the setting time is 1min, the duration is 40min, and the vacuum pressure is controlled at 0mbar.

[0162] 9. Cooling: temperature 20℃, duration 40min;

[0163] 10. Discharging: The board layer is automatically discharged and sent to the packaging machine;

[0164] 11. Nitrogen-filled blister packaging: The whole plate of aluminum foil mold (bottom film) is transferred to the film sealing machine for thermoplastic film sealing (top film), and the freeze-dried puffed fruit and vegetable juice products are blister-sealed in a nitrogen-filled environment;

[0165] 12. X-ray machine foreign body detection: The product passes through the X-ray machine for foreign body detection;

[0166] 13. Coding and packing: After sealing, the products are cut, coded, packed, palletized and finally put into storage.

[0167] Example 3 :

[0168] 1. Raw material acceptance: After the raw materials arrive at the factory, samples are taken and inspected according to the quality inspection plan. After the indicators are qualified, the laboratory will issue an inspection report;

[0169] 2. Ingredients: Start the seasoning program, and add the fruit and vegetable juices pumped into the storage tank into the ingredient tank according to the proportion. The raw materials include but are not limited to: orange juice, sea buckthorn juice, blueberry juice, potato juice, cauliflower juice, sweet corn juice, white onion juice, carrot juice, pumpkin juice, tomato juice, kohlrabi juice, button mushroom juice, shiitake mushroom juice, hericium erinaceus juice, hazel mushroom juice, white fungus juice, soy milk, fructose syrup. The carbohydrate content of the mixed fruit and vegetable juice is 13.5%, the solid content is 25%, the mixing time is controlled at 8 minutes, and the mixing temperature is 45°C;

[0170] 3. Steam jet sterilization: the material is pumped from the mixing temporary storage tank into the preheater, the preheater temperature is 65°C, and then pumped from the preheater into the sterilizer and insulation pipe for sterilization, the sterilization temperature is 88°C, and the time is 24s;

[0171] 4. Cooling: After sterilization, the material is cooled to 2-10℃ through a plate heat exchanger for temporary storage;

[0172] 5. Freezing: The material is pumped into the material plate layer (whole plate aluminum foil mold (bottom film)) of the freeze dryer. The first stage freezing temperature is -35°C, the setting time is 65 minutes, and the duration is 70 minutes. The second stage freezing temperature is -20°C, the setting time is 65 minutes, and the duration is 70 minutes. The third stage freezing temperature is -35°C, the setting time is 65 minutes, and the duration is 130 minutes.

[0173] 6. Primary drying: the first stage sublimation temperature is -10°C, the setting time is 100min, the duration is 40min, and the vacuum pressure is controlled at 0.35mbar; the second stage sublimation temperature is 4°C, the setting time is 65min, the duration is 100min, and the vacuum pressure is controlled at 0.65mbar; the third stage sublimation temperature is 4°C, the setting time is 10min, the duration is 200min, and the vacuum pressure is controlled at 0.25mbar; the fourth stage sublimation temperature is 8°C, the setting time is 40min, the duration is 280min, and the vacuum pressure is controlled at 0.25mbar;

[0174] 7. Secondary drying: The secondary drying temperature is 15°C, the setting time is 60 minutes, the duration is 180 minutes, and the vacuum pressure is controlled at 0.35 mbar to obtain a drying system;

[0175] 8. Puffing: The first stage puffing temperature is 50℃, the setting time is 10min, the duration is 180min, and the vacuum pressure is controlled at 0.15mbar. The second stage puffing temperature is 50℃, the setting time is 10min, the duration is 60min, and the vacuum pressure is controlled at 0.05mbar.

[0176] 9. Cooling: temperature 25℃, duration 60min;

[0177] 10. Discharging: The board layer is automatically discharged and sent to the packaging machine;

[0178] 11. Nitrogen-filled blister packaging: The whole plate of aluminum foil mold (bottom film) is transferred to the film sealing machine for thermoplastic film sealing (top film), and the freeze-dried puffed fruit and vegetable juice products are blister-sealed in a nitrogen-filled environment;

[0179] 12. X-ray machine foreign body detection: The product passes through the X-ray machine for foreign body detection;

[0180] 13. Coding and packing: After sealing, the products are cut, coded, packed, palletized and finally put into storage.

[0181] Comparative Example 1 :

[0182] Same as Example 2, except that the temperature of the four-stage sublimation of the primary drying was set to 15°C.

[0183] Comparative Example 2 :

[0184] Same as Example 2, except that the secondary drying duration was 300 min.

[0185] Comparative Example 3 :

[0186] Same as Example 2, except that the puffing treatment temperature was 10°C.

[0187] Comparative Example 4 :

[0188] Same as Example 1, except that the puffing treatment temperature was 10°C.

[0189] Comparative Example 5 :

[0190] Same as Example 3, except that the puffing treatment temperature was 10°C.

[0191] Comparative Example 6 :

[0192] The same as Example 3, except that only one stage of sublimation operation is performed in one drying.

[0193] The test data of each embodiment and comparative example are summarized in Table 1 below:

[0194] Table 1:

[0195]

[0196] It can be seen that the final expansion effect is poor in Comparative Examples 1 and 2 due to the excessively high apparent density of the drying system, and the expansion temperature in Comparative Example 3 is below the Tg of the drying system and cannot be expanded (see Figure 2 ).

[0197] Also, see Figure 3 , Comparative Examples 4 and 5 cannot be expanded because the expansion temperature is below the Tg of the drying system. Figure 3 In Comparative Example 6, since the moisture content of the drying system is too high, part of the structure explodes and splashes during puffing, and a regular puffed product cannot be obtained, resulting in puffing failure.

[0198] From the hydrogen proton low-field nuclear magnetic resonance NMR scan ( Figure 4 ) It can be seen that compared with the comparative example, the expanded product has a looser and more porous structure, a more uniform distribution of hydrogen protons, and a lower moisture content.

[0199] It should be noted that, although the technical solution of the present invention is introduced with specific examples, those skilled in the art will appreciate that the present invention should not be limited thereto.

[0200] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A freeze drying-puffing method for a basic liquid system, characterized in that: The method comprises: A freezing step, wherein the basic liquid system is frozen at a temperature below -20°C to obtain a frozen system; The step of drying is to dry the frozen system at a temperature below 20°C and under reduced pressure to obtain a dry system with a moisture content of less than 5% by mass, and an apparent density of the dry system of 0.35 to 0.56 g / cm 3 . The step of expanding is to expand the above-mentioned drying system under the conditions of temperature T and pressure P to obtain an expanded product. The temperature T is higher than the glass transition temperature Tg of the drying system, and the pressure P is at least lower than the pressure at the end of the drying step.

2. The method according to claim 1, characterized in that The basic liquid system is a system having substantially uniform components and having a water content of 90% by mass or less.

3. The method according to claim 1 or 2, characterized in that: The basic liquid system is derived from one or more of the following groups: juice or hydrate of fruit or vegetable substances.

4. The method according to any one of claims 1 to 3, characterized in that: The drying step includes a primary drying step and a secondary drying step. The primary drying step is used to remove free moisture, and the secondary drying step is used to remove bound moisture. The temperature of the secondary drying step is higher than that of the primary drying step.

5. The method according to any one of claims 1 to 4, characterized in that: In the puffing step, the dry system is puffed by boiling expansion under the conditions of the temperature T and the pressure P.

6. The method according to any one of claims 1 to 5, characterized in that: Before the freezing step, the method further includes a step of sterilizing the basic liquid system.

7. The method according to any one of claims 1 to 6, characterized in that: In the drying step, the pressure is below 0.7 mbar.

8. The method according to any one of claims 1 to 7, characterized in that: The temperature T in the puffing step is higher than the temperature at the end of the drying step by 10° C. or more.

9. The method according to any one of claims 1 to 8, characterized in that: The temperature T is 30-50° C., and the pressure P is below 0.2 mbar.

10. A method for preparing food, characterized in that: The method comprises the method according to any one of claims 1 to 9.

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