WO2009049449A1

WO2009049449A1 - A post-processing method for slowing rehydration rate of freeze dried fruit and vegetable pieces

Info

Publication number: WO2009049449A1
Application number: PCT/CN2007/003326
Authority: WO
Inventors: Min Zhang; Luelue Huang; Dongwei Sun; Dongfeng Sun
Original assignee: Jiangnan University; Shandong Luhua Group Co., Ltd.
Priority date: 2007-10-16
Filing date: 2007-11-23
Publication date: 2009-04-23
Also published as: CN101147505A; CN101147505B

Abstract

A post-processing method for slowing the rehydration rate of freeze dried fruit and vegetable pieces comprises a coating solution prepared by adding 8-12g lactoalbumin, 2-4g glycerol, 8-12g lactose per 100 ml water, connecting the coating solution to a flow pump, preheating dry chamber spout beds, introducing fruit and vegetable pieces, initiating induced air flow, keeping fruit and vegetable pieces in a fluid state inside the spout beds, opening the flow pump, spraying the surface of the fruit and vegetable pieces with the atomized coating solution, stopping the spray coating, removing, packing and storing.

Description

Post-treatment method for slowing down rehydration speed of freeze-dried fruit and vegetable diced

The invention relates to a post-treatment method for slowing the rehydration speed of freeze-dried fruit and vegetable diced, which is a method for coating a surface of a freeze-dried fruit and vegetable diced dough, and belongs to the technical field of fruit and vegetable food processing. Background technique

Fruits and vegetables are rich in vitamins and minerals, especially vitamin C. The rapid development of modern nutrition has improved people's comprehensive nutritional requirements for food, and the fruits and vegetables are mixed with corresponding liquid carriers such as milk and porridge. The appearance is novel, the taste is unique, and the milk is rich in protein and lipids. The porridge contains starch, protein and a small amount of lipids, which reflects the balance of nutrition.

In China, with the improvement of people's living standards, the demand for edible fruits and vegetables is rising rapidly. The market demand promotes the research and development of new products based on fruits and vegetables. It meets the needs of consumers with different tastes, new ways of eating and food consumption. Vacuum freeze-drying technology can reduce the nutrient loss and tissue damage caused by processing fruits and vegetables. To a minimum, but in the freeze-dried fruit and vegetable diced, due to the texture of the material itself, some fruits and vegetables such as strawberries, apples, etc. are mostly loose and dry after lyophilization, have strong hygroscopicity and rehydration, and after lyophilization Rehydration is easy to wilted and loses its original taste. Therefore, freeze-dried fruits and vegetables are generally required to be stored at a relative humidity of 40%. Freeze-dried fruits and vegetables are reconstituted too quickly, and the characteristics of rapid wilting in liquid carriers hinder their application.

To this end, Japan has produced a second freeze-dried fruit and vegetable diced, and after the first lyophilization, the fruit and vegetable diced into a liquid having a water-repellent raw material configuration, and then subjected to secondary lyophilization, secondary lyophilized fruits and vegetables. Ding has a certain water-blocking effect, but the effect is not obvious. It is wilted after being put into water at 50 °C for 1 min, and its shape shrinks, losing the shape of the original fruit and vegetables with many broken ends. In addition, the second lyophilization increases the cost of producing fruit and vegetable diced, thus reducing the consumer population.

In recent years, research on the surface coating process of fruit and vegetable diced has been carried out in foreign countries. After lyophilization, the outer coating film of fruits and vegetables has a good water-tightness, which makes the recovery of fruit and vegetable diced in liquid carrier slower. Maintain a good taste inside.

Han and YZhao et al. (2004) immersed strawberry and raspberry with chitosan solution, chitosan/Ca ²⁺ mixed solution and chitosan/V _E solution. As a result, all three solutions can significantly reduce strawberry or The weight loss of the raspberry, and the water permeability of the latter two solutions is less than the simple chitosan solution. Patricia S. Tanada-Palmu et al. (2005) used gluten protein solution, beeswax, Strawberry and raspberry are immersed in a film of a mixture of stearic acid and palmitic acid and a mixture of the two liquids. As a result, the strawberry and raspberry coatings of the two liquid mixtures are less weight-reducing, and the two solutions are used alone. No significant effect. However, the immersion method is not suitable for the coating film of freeze-dried fruit and vegetable diced. The lyophilized fruit and vegetable diced into the liquid is equivalent to rehydrating the water, and instantly absorbs a large amount of water and bonds to each other, so that it is difficult to dry.

Barbara Bmvin et al. (2006) sprayed a cracker on a cracker with a membrane solution made of corn starch, methylcellulose and soybean oil, cooled it, and placed it in a P ₂ 0 ₅ dryer for drying. The moisture absorption of the crackers. However, the method of drying after the coating film has a certain defect in the freeze-dried fruit and vegetable diced. Although the spray coating film makes the coating film more uniform and does not cause the fruit and vegetable diced to absorb water instantaneously, the strawberry diced surface is still bonded to each other. Since the membrane solution cannot be quickly dried, the fruit and vegetable lads are gradually deformed during the spraying process, and drying at the later stage is very difficult.

At present, in the choice of membrane materials, lipids are the primary choice for the production of water-resistant membranes, but the coating material of fruit and vegetable diced is preferably a transparent or translucent film to show the color of the fruit and vegetables, while the lipids are transparent. Poor sex, secondly, lipids can damage the healthy image of fruit and vegetable. Therefore, for fruit and vegetable diced, lipid film is not an ideal choice. Summary of the invention

The object of the present invention is to provide a post-treatment method for slowing down the rehydration speed of freeze-dried fruits and vegetables, and adopting a film solution suitable for lyophilization of the vegetable coating film and a drying method of the coating film to slow the recovery rate of the fruit and vegetable diced in the liquid carrier. The freeze-dried fruit and vegetable diced is more widely used.

Technical Solution: A post-treatment method for slowing the rehydration speed of freeze-dried fruits and vegetables, and drying the freeze-dried fruit and vegetable diced by spray bed drying method, the process is as follows: preparing a coating solution, and connecting the coating solution to the flow pump Preheating the drying chamber of the spouted bed, putting in the fruit and vegetable diced, opening the induced wind, so that the fruit and vegetable diced in the bed is in a fluidized state, opening the flow pump, spraying the atomized film solution on the surface of the fruit and vegetable diced, stopping the spraying and taking out Dried fruits and vegetables, packaged and stored, the specific steps are as follows:

1) Prepare a coating solution by adding a mixture of whey protein 8-12g, glycerin 2-4g and lactose 8-12g per lOOmL of water. Measure the above whey protein by adding water, add glycerin and lactose, magnetic stirrer Stir for 20 min, water bath at 70 ° C for 20 min, cool to room temperature for use;

2) Preheating the drying chamber of the spouted bed: 80 Ό preheating for 20 min;

3) Feeding: Put the fruit and vegetable diced into the spouted bed from the feeding port; the grain size of the fruit and vegetable diced is 0.5 X 0.5 X 0.5 (cm ³ ) -1.5 1.5 X 1.5 (cm ³ ), one input amount of 120~200g;

4) Turn on the wind to make the fruit and vegetable Ding rise: the air frequency is 30-45HZ;

5) Spraying and drying: Turn on the flow pump, spray the atomized membrane solution, the atomization pressure is l.OMpa, the flow pump flow rate is 0.05-0.1mL/s, the drying temperature is 50-70°C, and the spraying time is 30 -45min, drying is continued for 5 minutes after spraying;

6) Take out the dried fruits and vegetables and store them in a package.

In the present invention, whey protein (content of 90% or more) is selected as a main film material having water barrier properties. Whey protein contains α-lactalbumin and globulin, which have high dispersion and low hydrophilicity. The whey protein edible film prepared by using whey protein as a raw material and adding a plasticizer such as glycerin has low water permeability, oxygen permeability, high strength and good transparency, and has good elasticity.

Lactose is a disaccharide composed of one molecule of a-D-glucose and one molecule of β-D-galactose. Compared with other edible sugars, lactose has a low degree of sweetness and a relatively stable hygroscopicity. Lactose has the property of increasing the solids content and improving the texture of the product without making the product too sweet. These properties make lactose a certain improvement and enhancement of color and taste.

The spouted bed drying process started earlier and was originally designed to dry grain-like grains such as wheat. Scholars in Canada, the United States, and the former Soviet Union have done a lot of work on the development of spouted beds. Since the grain-like material particles are too coarse to be stably fluidized, the spouted bed exhibits more advantages than fluidized bed when drying such materials. In recent years, domestic applications of spouted beds have gradually expanded, but most of them are used in the pharmaceutical industry. The food industry is mostly used in the additive industry and is rarely used in food processing. Spouted bed requirements The material stays in the spout phase for a short period of time, so it can be used to dry heat sensitive materials. The processing temperature of fruits and vegetables is too high and it is easy to turn black, which is a heat sensitive material. Although the shape of the fruit and vegetable buds looks larger than the grain material, its quality is very light, so it can be dried using a spouted bed.

The invention first preheats and drys the material warehouse of the spouted bed, and then puts the fruit and vegetable diced into the bin, adjusts the inlet air temperature and the air introduction frequency, so that the fruit and vegetable diced are in a rising state in the warehouse. An external flow pump is used, and the membrane solution is sent to the bottom of the tank through a flow pump, and the membrane solution is uniformly sprayed on the fruit and vegetable diced by the bottom spray method. The flow pump can adjust the flow rate of the membrane solution. In the present invention, the minimum flow rate feed liquid is used, in order to achieve the speed drying after the surface of the fruit and vegetable diced surface is sprayed, otherwise the fruit and vegetable diced will adhere to each other. The optimum temperature for spraying is the highest temperature that does not discolor the fruits and vegetables. This can shorten the drying time of the surface film solution of the fruit and vegetable stalks. The product sprays evenly and is not easy to bond. The inlet air temperature is 60 °C and the actual material temperature is 55 °C. . Since the spraying rate is constant, the length of the spraying time determines the amount of spraying, that is, the thickness of the water-repellent layer on the surface of the fruit and vegetable, thereby affecting the rehydration value of the vegetable. The spraying time can be determined according to the requirements of the rehydration ratio. After coating for 30~45min, the sample of fruit and vegetable can be taken out by the sampler to determine the drying end point during the drying process of the film. The product remains in shape for a 6 min recovery in milk (10%) at room temperature and maintains a certain mouthfeel.

In addition, before the fruit and vegetable diced into the warehouse, it should be kept as dry as possible. The slight moisture absorption can make the dried fruit and vegetable diced slightly shrink. This shrinkage can strengthen the delay of the recovery of the fruit and vegetable diced in the liquid carrier. However, the water content at the end point after drying must be controlled below 8 % to facilitate preservation.

Compared with the uncoated fruit and vegetable diced, the dried fruit and vegetable diced by the method of the present invention can reduce the recovery ratio of 3 miri by 40-50% in milk at room temperature. In terms of shape, the uncoated fruit and vegetable diced is easy to generate a lot of slag during storage and transportation due to its texture, and waste is generated. However, after the film and vegetable diced in the invention is coated, not only the original slag will be Regranulation in the boiling chamber to form larger round particles, and the regular surface of the fruit and vegetable buds will not form new slag due to the action of the coating film.

Compared with the dried fruits and vegetables dried by hot air drying after spraying, the dried film of the invention has a short drying time, saves cost, and has almost no difference in appearance and shape after lyophilization, and the color is bright and bright; the hot air after coating Dry fruit and vegetable diced drying time is very long, it takes 6-7 hours to reduce the moisture content to below 8%, although the hot air dried fruit and vegetable diced recovery ratio is very small, such as strawberry diced in milk at room temperature for 3min, 6min and 15min The recovery ratios were 0.4186, 0.6041, and 0.8293, respectively. However, its shape shrinks very seriously, and the shape of the vegetable diced has been completely lost. The color part is blackened, and the chewing still has a harder taste after soaking. In addition, the loss of nutritional value is also very serious.

In summary, the present invention adopts a coating solution having good water-blocking property, and uniformly sprays the mist-like membrane solution onto the surface of the fruit and vegetable by a flow pump and an atomizer, and the flow pump controls the membrane solution to flow slowly, so Causes the fruit and vegetables to absorb water instantly and is difficult to dry. In the present invention, the coating film and the drying are simultaneously performed, and the fruit and vegetable diced are in a rising state in the spouted bed. When the film solution is uniformly sprayed on the surface of the fruit and vegetable diced, the hot air rapidly dries the fruits and vegetables, and the fruits and vegetables do not cross each other. Bonding and no deformation, in addition, simultaneous filming and drying also greatly shortens the operation time.

The lyophilized coated fruit and vegetable diced product can be applied as a raw material to different carriers, for example, in yoghurt, milk, and flavored milk beverages, or as a terminal product after seasoning, that is, ready-to-eat, It is easy to store and transport. Therefore, freeze-dried fruit and vegetable diced has a good application prospect in a variety of liquid foods. detailed description The spouted beds used in the following examples are FLP-1.5 spouted beds produced by Changzhou Jiafa Granulating Drying Equipment Co., Ltd. All parameters can be numerically controlled, and the air is fed from the bottom and externally connected to the flow pump.

Example 1: Production of a film drying method for slowing down the reconstitution of lyophilized strawberry diced water. 150 g of lyophilized strawberry diced with a moisture content of 6.66% was selected, and the size of the strawberry diced rice was about 1 XIXI (cm ³ ), but since the strawberry itself was irregular, Therefore, there are some smaller particles. The spout bed has a capacity of 3kg. Firstly close the system, dry the chamber with hot air of 80 °C, the air frequency is 35HZ, then lower the temperature to 60 °C, close the induced air, put the strawberry diced into the bed from the feeding port, and immediately close the feeding port; Then open the induced air, so that the strawberry dices are in the ascending state in the warehouse. After the rise and stability, the flow pump is turned on, the membrane solution flow rate is controlled at 0.05-0.1 niL/s, and the atomization pressure is l.OMpa; in the process of boiling and drying In order to make the liquid sprayed on the surface of strawberry diced quickly dry, and because the weight of strawberry diced has increased, it is necessary to gradually increase the frequency of the induced wind, up to 45HZ, stop spraying after 38min, and remove the strawberry diced after 45min, the color is bright, The moisture content was measured to be 3.76%.

The recovery ratio of the coated strawberry dipped in milk at room temperature for 3 min and 6 min was 1.770 and 2.432, respectively, while the recovery ratios of uncoated strawberry dipped in milk at room temperature for 10s, 30s and 60s were 3.807, 6.162 and 6.419.

Example 2: Production of a coating film drying method for slowing down lyophilization of apple diced diced water 150 g of apple diced with a water content of 5.79% was selected, the size of apple diced rice was about 1 cm ³ , and the capacity of the spouted bed was 3 kg. Closed system, adjust the hot air temperature until 80 Ό to dry in the warehouse, the time is about 20min, the air intake frequency is 35HZ, then the temperature is lowered to 50 °C, the air is closed; the feeding port is opened, and the apple diced is quickly placed. Immediately close the feeding port; open the air, so that the apple dip is in the ascending state, because there is hysteresis when adjusting the temperature, it will not reach the required temperature immediately, it takes a period of time to achieve parameter stability. Open the flow pump, the membrane solution flow rate is 0.05-0.1mL/s, the atomization pressure is l.OMpa, the bow|wind frequency is gradually increased from 30HZ to 40HZ, after 45min, the spraying is stopped, and after 50min, the moisture content is 4.38. %.

The recovery ratios of the dried apple diced apples at room temperature for 3 min and 6 min were 1.64 and 2.278, respectively. The reconstitution ratios of uncoated apple cider at 30s and 60s in milk at room temperature were 5.724 and 5.916, respectively.

Example 3: Production of a drying method for slowing the drying of freeze-dried carrot diced water. Selection of 150 g of lyophilized carrot diced with a water content of 6.27%, the size of the carrot diced is about 0.6 cm X 0.6 cm X 0.6 cm, spouted bed The capacity is 3kg. First close the system, dry the chamber with 80 热 hot air, the induced air frequency is 35HZ, then lower the temperature to 70 °C, Close the air inlet, open the feeding port and put the carrot into the feeding. Immediately close the feeding port, then open the air inlet. The carrot is in the ascending state in the warehouse. After the boiling stability, the flow pump is turned on, and the membrane solution flow rate is controlled at 0.05-O. lmL / s, the atomization pressure is l.OMpa, in the process of boiling and drying, gradually adjust the air frequency, up to 45HZ, stop spraying after 30min, take out the carrot diced after 35min, measured the moisture content is 4.69%.

The recovery ratios of the dried film of the dried carrots at room temperature for 3 min and 6 min were 1.587 and 2.165, respectively, and the recovery ratios of uncoated strawberry dipped in milk at room temperature for 30 s and 60 s were 4.659 and 5.134, respectively.

Claims

Rights request

1. A post-treatment method for slowing the rehydration speed of freeze-dried fruits and vegetables, characterized in that the freeze-dried fruit and vegetable diced is dried by a fluidized bed drying method, according to the following steps:

1) Prepare the coating solution:

Add whey protein 8-12g, glycerin 2-4g and lactose 8-12g per lOOmL of water to prepare a coating solution. According to the above measurement, the whey protein with a purity of more than 90% is swollen with water, added with glycerin and lactose, and magnetically stirred. Stir for 20 min, water bath at 70 ° C for 20 min, cool to room temperature for use;

2) Preheating the spray chamber of the spouted bed: preheating at 80 ° C for 20 min;

3) Feeding: Put the fruit and vegetable diced into the spouted bed from the feeding port; the grain size of the fruit and vegetable diced is 0.5 X 0.5 X 0.5 (cm ³ ) -1.5 X 1.5 X 1.5 (cm ³ ), and the input amount is 120~200g;

5) Spraying and drying: Turn on the flow pump and spray the atomized membrane solution. The atomization pressure is l.OMpa, the flow pump flow is 0.05-0. lmL/s, and the drying temperature is 50-70°. , spraying time is 30-45niin, and drying is continued for 5min after spraying;

6) Take out the dried fruits and vegetables and store them in a package.