Method for improving drying efficiency and quality of freeze-dried Dangshan pear slices through combination of composite recombination and pulse-ultrasonic treatment

Abstract

The invention relates to a method for improving the drying efficiency and quality of freeze-dried Dangshan pear slices by combining composite recombination with pulse-ultrasonic treatment, and belongs to the technical field of fruit and vegetable drying processing. According to the method, Dangshan pears with pulp containing a large number of stone cells are selected as raw materials, the stone cells of the Dangshan pears are broken into fine particles through pulping and homogenizing in a recombination technology, then the hardness and brittleness, the total phenol content and the total flavone content of a freeze-dried pear slice product are improved through a composite recombination technology, and the oxidation resistance is improved; and on the basis, a pulsed electric field combined ultrasonic pretreatment technology is adopted, so that the freeze-drying efficiency of the composite recombinant pear slices is further improved, and the nutrient content of the product is further improved. The composite recombination technology is combined with pulse-ultrasonic pretreatment, so that the drying efficiency of the freeze-dried composite recombinant pear slices can be improved, the nutritional value of the product is remarkably increased, and the additional value of Dangshan pears is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of fruit and vegetable drying processing, and particularly relates to a method for improving the drying efficiency and quality of freeze-dried Dangshan pear slices by composite recombinant combined pulse-ultrasonic treatment. Background Art

[0002] In the context of balanced diets, the comprehensive nutritional intake of fruits and vegetables from multiple sources has become a core demand of modern food consumption. Recombinant fruit and vegetable products are a new type of convenient snack with multi-dimensional nutritional benefits, created by combining and recombining fruits and vegetables containing multiple nutrients through crushing, pulping, homogenizing, compounding, and reshaping. Through structural recombinant processing technology, these products transcend the limitations of single raw materials, achieving targeted compounding of nutritional components and synergistic enhancement of functional factors, providing consumers with precise nutritional solutions.

[0003] Dangshan pears are renowned for their large, bright yellow fruit, thin skin, juicy texture, and rich, sweet flavor. However, fresh Dangshan pears contain a high concentration of stone cells, which compromises their taste and economic value. Eliminating stone cell processing technology and developing high-nutrition, high-quality processed products will be key to overcoming the bottlenecks in the Dangshan pear industry's development. The crushing and homogenization process within the composite recombinant technology breaks down the Dangshan pear's stone cells into fine particles, increasing the fineness of the recombinant Dangshan pear pulp and significantly boosting the product's nutritional value. Furthermore, recombinant technology offers low raw material requirements for Dangshan pears, effectively utilizing non-commercialized Dangshan pears, enhancing resource efficiency and increasing the added value of Dangshan pears.

[0004] Since reconstructed fruit and vegetable raw materials have no cell wall support after being crushed, their internal fluidity is relatively strong, and the use of traditional processing technology will cause the product to collapse or deform. Freeze-drying technology can well maintain the appearance of reconstructed fruits and vegetables in any shape, and can also better preserve the nutritional content, color, flavor and other qualities of the product. However, previous studies have shown that the freeze-drying cycle of the reconstructed system is longer than that of the monomeric fruit and vegetable raw materials due to the decrease in material porosity and the change in the water migration path, which significantly restricts the efficiency of industrial production. In recent years, new physical field processing technologies such as ultrasound and pulsed electric fields have been used as pre-treatment technologies for freeze-dried fruits and vegetables due to their efficient mass transfer and heat transfer properties. Chinese patent CN 114403206 A discloses a method for improving the drying efficiency, color, and flavor of ginger. This patent uses ultrasonic treatment to destroy the cell walls and membranes of ginger slices, forming micropores, increasing water flow, and shortening drying time. Chinese patent CN 119908449 A discloses a method for preparing cabbage by ultrasonic alkali pretreatment and freeze-drying. This patent destroys the cabbage cell walls through ultrasonic pretreatment, which helps improve the subsequent freeze-drying efficiency. Chinese patent CN 11934450 A discloses an ultrafine powder of tea-branch orange with anti-inflammatory effects and its preparation method. This patent uses a high-voltage pulsed electric field to change the cell structure of the tea-branch orange fruit raw material, thereby improving freeze-drying efficiency. Other patents disclose the use of ultrasound combined with pulsed electric fields to improve the drying efficiency of fruits and vegetables. For example, Chinese patent CN 112586556 A discloses a drying method for shiitake mushrooms using ultrasonic and pulsed electric field pretreatment. This patent uses ultrasonic and pulsed electric field pretreatment to increase the permeability of the mushroom cell membrane, change the cell structure, affect tissue mass transfer, increase water loss during the drying process, and improve drying efficiency. Chinese patent CN 118044536 A discloses a method for drying rapeseed stalks and the dried rapeseed stalks. The patent adopts ultrasonically coupled pulsed electric field to protect the color while shortening the drying time.

[0005] All of the above patents use ultrasound, pulsed electric fields, or combined treatments to change the cell membranes, cell walls, and other cell structures of the original fruit and vegetable tissues, thereby increasing the permeability of the material tissue and promoting water migration, thereby improving drying efficiency. The composite recombinant pear slices invented in this patent are composed of pears, yam, lily, and white fungus, with pears accounting for more than 90%. The addition of yam, lily, and white fungus increases the protein, starch, pectin, and polysaccharide content in the composite, forming a multi-component mixed aggregate. Previous studies have found that the freeze-drying time of composite recombinant pear slices is 40% longer than that of single recombinant pear slices, greatly increasing the energy consumption and cost of drying. What effects do ultrasound and pulsed electric fields have on this composite recombinant mixed aggregate? Does the freeze-drying process change the migration path of bound water? Does it affect the nutritional components of the composite recombinant pear slices? These issues directly determine the processing cost and nutritional value of the composite recombinant pear slice products. Therefore, in response to the above problems, this patent adopts composite recombinant technology to improve the sensory quality and storage quality of freeze-dried pear slices. At the same time, pulsed electric field combined with ultrasonic treatment is used to increase the migration rate of bound water in the composite recombinant pear slices during the freeze-drying process, greatly improving the drying efficiency. At the same time, it is beneficial to the release of bound polysaccharides and polyphenols and other compounds, and the nutritional value is further improved on the basis of composite recombinant technology. Summary of the Invention

[0006] Technical issues

[0007] The purpose of the present invention is to improve the drying efficiency of freeze-dried recombinant Dangshan pear slices, so that the product has high nutritional value and quality. A method for improving the drying efficiency and quality of freeze-dried Dangshan pear slices by composite recombinant combined pulse-ultrasound treatment is proposed. The problem of rough taste caused by the stone cells of Dangshan pear is eliminated by pulping and homogenization, and a fine and uniform pear pulp is obtained. The formula of composite recombinant pear slices is optimized to improve the hardness, crispness, nutritional content and storage quality of the product. The problem of long freeze-drying time of composite recombinant pear slices is further solved by using pulse electric field combined with ultrasound, while further improving the content of nutrients in the product, which is more conducive to the digestion and absorption of nutrients in the body of freeze-dried composite recombinant pear slices. This patent comprehensively utilizes the low-priced Dangshan pear raw material, improves its added value, significantly improves the medicinal and edible function of the product, greatly improves the freeze-drying efficiency, saves production costs, improves technical and economic efficiency, and promotes the development and extension of the Dangshan pear and composite recombinant fruit and vegetable industries.

[0008] Technical Solution

[0009] A method for improving the drying efficiency and quality of freeze-dried Dangshan pear slices by composite recombination combined with pulse-ultrasonic treatment, characterized in that:

[0010] (1) Raw material selection: Use fresh and appropriately mature Dangshan pears:

[0011] (2) Cleaning and cutting: Clean the Dangshan pears, peel and core them, and cut them into small pieces of 2 to 3 cm;

[0012] (3) Beating: Place the pear pieces in a beater and beat for 200-400 seconds to obtain coarse pear pulp;

[0013] (4) Homogenization: Pour the crude pear pulp into a colloid mill and repeatedly shear and homogenize for 3 to 5 times to obtain pear pulp;

[0014] (5) Preparation of auxiliary materials: Wash and peel fresh Chinese yam, cut into 3-5 cm small segments, clean dried lily bulbs and dried white fungus, put the Chinese yam segments, dried lily bulbs and dried white fungus into a steamer and steam for 30-60 min;

[0015] (6) Composite reconstitution: Pear pulp is mixed with steamed yam segments, lily bulbs, and white fungus, and then put into a pulper for 200-400 seconds. The pulp is then poured into a colloid mill and repeatedly sheared and homogenized for 3-5 times to obtain composite reconstituted pear pulp;

[0016] (7) Pulsed electric field treatment: the composite reconstituted pear pulp is placed in a pulsed electric field treatment device with a pulsed electric field strength of 2 to 4 kV / cm and a pulse number of 100 to 200 times;

[0017] (8) Ultrasonic treatment: the composite reconstituted pear pulp after pulse electric field treatment is placed in an ultrasonic device with an ultrasonic power of 100 to 200 W, an ultrasonic time of 30 to 60 min, and a temperature of 40 to 60°C;

[0018] (9) Molding: Pour the composite reconstituted pear pulp after pulse-ultrasonic treatment into a mold plate with a height of 1 cm and a diameter of 3 cm;

[0019] (10) Freezing: Place the mold plate with the composite recombinant pear pulp into a vacuum freeze dryer that has been pre-cooled to -35°C and freeze for 2 to 4 hours;

[0020] (11) Freeze-drying: Turn on the vacuum system until the vacuum degree of the freeze-drying chamber reaches below 30 Pa, turn on the heating plate switch, and freeze-dry for 10 to 12 hours;

[0021] The method for improving the drying efficiency and quality of freeze-dried Dangshan pear slices by composite recombinant combined with pulse-ultrasonic treatment is characterized in that the mass ratio of the composite recombinant pear pulp is 90-92% Dangshan pear, 3-4% yam, 2.5-3.5% lily, and 2-3% tremella;

[0022] The freeze-dried composite recombinant pear slice product is obtained by the method of improving the drying efficiency and quality of freeze-dried Dangshan pear slices by composite recombinant combined with pulse-ultrasonic treatment.

[0023] Beneficial effects

[0024] 1. The present invention introduces recombination technology to break the stone cells in Dangshan pears, improve product added value, and promote the effective use of resources. Since Dangshan pears contain a large number of stone cells in their flesh, resulting in coarse flesh, strong graininess, poor taste, low consumer popularity, and low market price, breaking the stone cell processing technology and introducing high-value and high-quality processing technology will become the key to breaking the bottleneck of Dangshan pear industry development. The present invention uses pulping and homogenization processing in the recombination process to break the stone cells in Dangshan pears into fine particles, increase the fineness of the recombinant pear pulp, lay the foundation for the research and development of high-quality Dangshan pear products, and improve product added value. At the same time, recombination technology does not have high requirements for raw materials, can effectively utilize non-commercialized Dangshan pear raw materials, and improve the effective use of resources.

[0025] 2. The present invention introduces composite recombinant technology and incorporates the concept of medicine and food being of the same origin, thereby improving product quality and functional efficacy. Since the single recombinant pear slices have low hardness, soft taste, high vibration breakage rate and hygroscopicity, the product acceptance is low. The present invention innovatively adds yam, lily and tremella, which are ingredients of the same origin as medicine. Yam has the health-care effects of nourishing the spleen and stomach, promoting fluid production and benefiting the lungs. Lily has the effects of nourishing yin and moistening the lungs, clearing the heart and calming the mind, and replenishing the middle and replenishing qi. Tremella has the effects of moistening the lungs and nourishing yin. The synergistic effect of the four materials can achieve the effects of clearing and nourishing the lungs, nourishing yin and promoting fluid production, and has both food protection and medicinal auxiliary conditioning value. At the same time, the addition of yam, lily and tremella can significantly improve the hardness and brittleness of the composite recombinant pear slices, reduce shrinkage, vibration breakage and hygroscopicity, increase the content of total phenols and total flavonoids, and increase antioxidant capacity.

[0026] 3. The present invention adopts pulse electric field combined with ultrasonic pretreatment technology to further improve the freeze-drying efficiency of composite recombinant pear slices and further improve the nutritional value of the product. By comparing single recombinant pear slices and composite recombinant pear slices, it was found that the freeze-drying time of composite recombinant pear slices was significantly longer than that of single recombinant pear slices, extended by 40%. Composite recombinant pear slices formed a sheet-like stacked rigid structure, which hindered the formation of moisture migration channels. We compared ultrasound and pulse electric field alone, and ultrasound combined with pulse electric field and pulse electric field combined with ultrasonic treatment, and found that the pulse electric field combined with ultrasonic treatment significantly shortened the freeze-drying time of composite recombinant pear slices, and was even shorter than the freeze-drying time of single recombinant pear slices, while the hardness and brittleness were significantly higher than single recombinant pear slices. At the same time, we found that the total phenols, total flavonoids, polysaccharides and other nutrients of composite recombinant pear slices treated with pulse electric field combined with ultrasonic treatment increased by 50%-110% compared with composite recombinant pear slices, and increased by 90%-140% compared with single recombinant pear slices. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The drying curves of freeze-dried composite recombinant pear slices with different pretreatments;

[0028] Figure 2FTIR spectra and X-ray diffraction patterns of freeze-dried composite recombinant pear slices with different pretreatments;

[0029] Figure 3 The total phenolic and flavonoid contents of freeze-dried composite reconstituted pear slices with different pretreatments; DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to the embodiments, but the present invention is not limited thereto.

[0031] Example 1

[0032] Select fresh and appropriately mature Dangshan pears as raw materials, wash the Dangshan pears with running water, drain the water, peel and core them, and cut them into small pieces of 2 to 3 cm, put the pear pieces into a beater and beat them for 350 seconds to obtain coarse pear pulp, pour the coarse pear pulp into a colloid mill and repeatedly shear and homogenize it 3 times to obtain reconstituted pear pulp; wash the fresh iron stick yam, peel it and cut it into small pieces of 5 cm, wash the dried lily and dried white fungus, put the yam segments, dried lily and dried white fungus into a steamer and steam them for 60 minutes; mix the pear pulp with the steamed yam segments, lily and white fungus according to the mass ratio of 92:3:2.5:2.5, put them into a beater and beat them for 3 minutes 50s, then pour it into the colloid mill and repeatedly shear and homogenize 3 times to obtain composite recombinant pear pulp; place the composite recombinant pear pulp in a pulse electric field treatment equipment, the pulse electric field intensity is 4kV / cm, the number of pulses is 150 times, and then place the composite recombinant pear pulp after pulse electric field treatment in an ultrasonic equipment, the ultrasonic power is 150W, the ultrasonic time is 50min, and the temperature is 55℃; pour the treated composite recombinant pear pulp into a mold plate with a height of 1cm and a diameter of 3cm, place the mold plate into a vacuum freeze dryer that has been pre-cooled to -35℃, freeze for 3h, turn on the vacuum system until the vacuum degree of the freeze drying chamber reaches below 30Pa, turn on the heating plate switch, and freeze dry for 10h.

[0033] Example 2

[0034] Select fresh and appropriately mature Dangshan pears as raw materials, wash the Dangshan pears with running water, drain the water, peel and core them, cut them into small pieces of 2 to 3 cm, put the pear pieces into a beater and beat them for 240 seconds to obtain coarse pear pulp, pour the coarse pear pulp into a colloid mill and repeatedly shear and homogenize it 4 times to obtain reconstituted pear pulp; wash the fresh iron stick yam, peel it and cut it into small pieces of 5 cm, wash the dried lily and dried white fungus, put the yam segments, dried lily and dried white fungus into a steamer and steam them for 40 minutes; mix the pear pulp with the steamed yam segments, lily and white fungus in a mass ratio of 91:3.5:3:2.5, put them into a beater and beat them for 2 minutes 40s, then pour it into the colloid mill and repeatedly shear and homogenize it 4 times to obtain composite recombinant pear pulp; place the composite recombinant pear pulp in a pulse electric field treatment device, the pulse electric field intensity is 2kV / cm, the number of pulses is 100 times, and then place the composite recombinant pear pulp after pulse electric field treatment in an ultrasonic device, the ultrasonic power is 100W, the ultrasonic time is 30min, and the temperature is 45℃; pour the treated composite recombinant pear pulp into a mold plate with a height of 1cm and a diameter of 3cm, place the mold plate into a vacuum freeze dryer that has been pre-cooled to -35℃, freeze for 4h, turn on the vacuum system until the vacuum degree of the freeze-drying chamber reaches below 30Pa, turn on the heating plate switch, and freeze-dry for 12h.

[0035] As shown in Table 1, the formula of the freeze-dried composite recombinant pear slices used in this embodiment was obtained by D-optimal mixture design optimization, setting the range of pears to 85% to 95%, the range of lilies to 0% to 3%, yam to 2.5% to 6%, and white fungus to 2.5% to 6%. The hardness, crispness and sensory scores of the freeze-dried composite recombinant pear slices were used as inspection indicators, and the Design Expert software was used to perform optimal mixture design and regression model analysis. The results of variance analysis are shown in Table 2. The best formula finally optimized was 91% pear pulp, 3.5% yam, 3% lily, and 2.5% white fungus.

[0036] Table 1 D-optimal mixture design table and results

[0037]

[0038] Table 2 Analysis of variance of hardness, crispness and sensory scores

[0039]

[0040] As shown in Tables 3 and 4, by comparing the quality, storage quality, nutritional components and antioxidant capacity of the freeze-dried composite recombinant pear slices used in this example with the freeze-dried single recombinant pear slices, it was found that the freeze-dried composite recombinant pear slices had higher hardness and crispness, lower shrinkage rate, smaller vibration breakage rate and hygroscopicity, and had higher nutritional value and antioxidant capacity.

[0041] Table 3 Quality differences between freeze-dried single and composite reconstituted pear slices

[0042]

[0043] Table 4 Differences in nutritional components and antioxidant capacity between freeze-dried single and composite reconstituted pear slices

[0044]

[0045] like Figure 1 As shown in the figure, the effects of combined recombinant treatment with pulsed-ultrasound on the drying rate of freeze-dried pear slices using this example were analyzed. CK represents recombinant pear slices; US represents recombinant pear slices treated with ultrasound; PEF represents recombinant pear slices treated with pulsed electric fields; US-PEF represents recombinant pear slices treated with ultrasound combined with pulsed electric fields; and PEF-US represents recombinant pear slices treated with pulsed electric fields combined with ultrasound. Both US-PEF and PEF-US treatments significantly shortened drying time and improved drying efficiency, achieving a 40% reduction in drying time compared to the CK group.

[0046] like Figure 2 As shown in the figure, analysis of the effects of the combined recombinant pulsed-ultrasonic treatment used in this example on the chemical structure and crystallinity of freeze-dried pear slices revealed that pretreatment reduced the intensity of the absorption peak generated by the stretching vibration of the OH bond, indicating that the absorption peaks of the stretching vibration of the polypeptide and free carboxyl group C=O shifted to lower wavenumbers, indicating that pretreatment rearranged the internal hydrogen bonds of the protein and changed its spatial conformation. Pretreatment also reduced the intensity of the characteristic absorption peak of starch, indicating that pretreatment shifted the starch's crystallinity toward an amorphous state. Comparison of different pretreatments revealed that this change was most significant with PEF-US.

[0047] like Figure 3 As shown in the figure, by analyzing the effect of the composite recombinant combined pulse-ultrasound treatment adopted in this example on the nutritional content of freeze-dried pear slices, it can be found that the pretreatment increases the total phenol and total flavonoid contents in the freeze-dried pear slices to varying degrees, among which the total phenol and total flavonoid contents in the PEF-US treatment are the highest, which are increased by 54.90% and 50.69% respectively compared with the CK group.

Claims

1. A method for improving the drying efficiency and quality of freeze-dried Dangshan pear slices by composite recombination combined with pulse-ultrasound treatment, characterized in that: (1) Raw material selection: Use fresh and appropriately mature Dangshan pears; (2) Cleaning and cutting: Clean the Dangshan pears, peel and core them, and cut them into small pieces of 2 to 3 cm; (3) Beating: Place the pear pieces in a beater and beat for 200-400 seconds to obtain coarse pear pulp; (4) Homogenization: Pour the crude pear pulp into the colloid mill and repeatedly shear and homogenize 3 to 5 times to obtain pear pulp: (5) Preparation of auxiliary materials: Wash and peel fresh Chinese yam, cut into 3-5 cm small segments, clean dried lily bulbs and dried white fungus, put the Chinese yam segments, dried lily bulbs and dried white fungus into a steamer and steam for 30-60 min; (6) Composite reconstitution: Pear pulp is mixed with steamed yam segments, lily bulbs, and white fungus, and then put into a pulper for 200-400 seconds. The pulp is then poured into a colloid mill and repeatedly sheared and homogenized for 3-5 times to obtain composite reconstituted pear pulp; (7) Pulsed electric field treatment: the composite reconstituted pear pulp is placed in a pulsed electric field treatment device with a pulsed electric field intensity of 2 to 4 kV / cm and a pulse number of 100 to 200 times; (8) Ultrasonic treatment: the composite reconstituted pear pulp after pulse electric field treatment is placed in an ultrasonic device with an ultrasonic power of 100 to 200 W, an ultrasonic time of 30 to 60 min, and a temperature of 40 to 60°C; (9) Molding: Pour the composite reconstituted pear pulp after pulse-ultrasonic treatment into a mold plate with a height of 1 cm and a diameter of 3 cm; (10) Freezing: Place the mold plate with the composite recombinant pear pulp into a vacuum freeze dryer that has been pre-cooled to -35°C and freeze for 2 to 4 hours; (11) Freeze-drying: Turn on the vacuum system until the vacuum degree of the freeze-drying chamber reaches below 30 Pa, turn on the heating plate switch, and freeze-dry for 10 to 12 hours.

2. The method for improving the drying efficiency and quality of freeze-dried Dangshan pear slices by composite recombination combined with pulse-ultrasound treatment according to claim 1, characterized in that: The mass ratio of the composite recombinant pear pulp is 90-92% of Dangshan pear, 3-4% of yam, 2.5-3.5% of lily, and 2-3% of white fungus.

3. A freeze-dried composite recombinant pear slice product obtained by the method of improving the drying efficiency and quality of freeze-dried Dangshan pear slices by composite recombinant combined pulse-ultrasonic treatment according to claim 1 or 2.

Images