Efficient pretreatment and low-temperature squeezing process for increasing oil content of tea fruits

Abstract

The invention provides an efficient pretreatment and low-temperature squeezing process for increasing the oil content of tea fruits, and relates to the technical field of low-temperature squeezing processes, and the process comprises the following steps: screening and grading tea fruit raw materials: grading according to particle sizes by using a vibrating screen classifier, removing impurities, and carrying out steam softening treatment: softening the tea fruits in a saturated steam environment at the temperature of 80-95 DEG C for 15-30 minutes, microwave-assisted wall breaking: treating for 5-10 minutes by utilizing microwave frequency of 2450MHz and power of 5-10kW, breaking a cell wall structure, squeezing at low temperature: adopting a hydraulic squeezer, controlling the squeezing temperature to be less than or equal to 50 DEG C and the pressure to be 20-35MPa, squeezing in two stages, separating oil residues: separating the oil residues by a centrifugal machine at the rotating speed of 3000-5000r / min, collecting crude oil of tea fruits, softening tea fruit shells and breaking the cell wall structure in a high-temperature and high-humidity environment, and crushing the crude oil of the tea fruits by utilizing a high-temperature and high-humidity environment. High-frequency electromagnetic waves directly act on cell walls, heat effect and mechanical stress are generated, cell membranes are broken, cellulose and pectin are accurately decomposed by the compound enzyme, and the grease is further released.

Description

Technical Field

[0001] The invention belongs to the technical field of low-temperature pressing technology, and more specifically, particularly relates to a high-efficiency pretreatment and low-temperature pressing technology for improving the oil content of tea fruit. Background Art

[0002] Tea fruit oil is rich in unsaturated fatty acids and antioxidants and is a high-quality edible oil. However, the traditional pressing process has the following problems:

[0003] Insufficient pretreatment: The tea fruit shell is hard and the cell wall is not fully destroyed, resulting in a low oil yield (only 15%-20%).

[0004] High temperature destroys ingredients: Conventional hot pressing temperature is >100°C, resulting in serious loss of active substances such as polyphenols and vitamin E.

[0005] High energy consumption: long steam softening time (>1 hour), insufficient application of microwave wall breaking technology, and low energy efficiency.

[0006] Incomplete separation: The residual oil rate in a single squeeze is high (>10%), requiring multiple squeezes or chemical solvent extraction, affecting the safety of the oil.

[0007] Oxidation risk: Oils are prone to oxidation and rancidity during the pressing process, requiring the addition of large amounts of antioxidants, which increases costs. Summary of the invention

[0008] In order to solve the above technical problems, the present invention provides a high-efficiency pretreatment and low-temperature pressing process for improving the oil content of tea fruit to solve the above problems.

[0009] An efficient pretreatment and low-temperature pressing process for improving the oil content of tea fruit comprises the following steps:

[0010] (1) Screening and grading of tea fruit raw materials: Use a vibrating screen to grade by particle size and remove impurities;

[0011] (2) Steam softening treatment: soften the tea fruit in a saturated steam environment at a temperature of 80-95°C for 15-30 minutes;

[0012] (3) Microwave-assisted cell wall destruction: Use microwaves at a frequency of 2450 MHz and a power of 5-10 kW for 5-10 minutes to destroy the cell wall structure;

[0013] (4) Low temperature pressing: use a hydraulic press, control the pressing temperature to ≤50°C, the pressure to 20-35MPa, and press in two stages;

[0014] (5) Oil residue separation: The oil residue is separated by a centrifuge at a speed of 3000-5000 r / min to collect the tea fruit crude oil.

[0015] Preferably, in step (1), the particle size classification standard of the tea fruit is: the diameter of the first-level fruit is ≥15mm, the diameter of the second-level fruit is 10-15mm, and the diameter of the third-level fruit is <10mm. After classification, the tea fruit is treated separately. In step (2), steam softening adopts an intermittent steam injection device, and the steam humidity is 95%-100%. After softening, the moisture content of the tea fruit is controlled at 18%-22%. In step (3), microwave treatment adopts a multi-frequency alternating mode, including alternating radiation of a low frequency band (915MHz) and a high frequency band (2450MHz), and the total duration does not exceed 15 minutes.

[0016] Preferably, the low-temperature pressing in step (4) is divided into two stages: pre-pressing and final pressing: the pre-pressing pressure is 10-15MPa and the time is 5 minutes; the final pressing pressure is 25-35MPa and the time is 10 minutes. The temperature during the whole pressing process is maintained at ≤50°C by a circulating cooling water system. In step (5), the oil residue after centrifugal separation is subjected to secondary pressing, the secondary pressing pressure is 40MPa, the temperature is ≤55°C, and the residual oil is extracted by ultrasonic assistance. The hydraulic press is equipped with a nitrogen protection system, and the oxygen concentration is controlled below 5% during the pressing process to prevent oil oxidation.

[0017] Preferably, the enzymatic hydrolysis step of the pretreated tea fruit is: using a composite enzymatic hydrolysis of cellulase and pectinase, the enzymatic hydrolysis temperature is 45-50°C, pH 4.5-5.5, and the time is 2-4 hours; the tea fruit after enzymatic hydrolysis is low-temperature dried to a moisture content of 8%-12%, the drying temperature is ≤40°C, and the time is 1-2 hours; the pressed tea fruit crude oil is refined by molecular distillation, the distillation temperature is 120-150°C, the vacuum degree is 0.1-1kPa, and free fatty acids and impurities are separated.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The oil content is significantly improved. The tea shell is softened by a high temperature and high humidity environment, the cell wall structure is broken, and the oil is released more easily. High-frequency electromagnetic waves directly act on the cell wall, generating thermal effects and mechanical stress, breaking the cell membrane, and the complex enzyme accurately decomposes cellulose and pectin to further release the oil. Compared with the traditional process (oil yield 15%-20%), the oil yield of the process of the present invention is increased to 22%-25%, and can reach up to 28% (combining enzymatic hydrolysis and molecular distillation).

[0020] Retain nutrients, pressing temperature ≤50℃: avoid degradation of heat-sensitive ingredients such as polyphenols and vitamin E, retention rate ≥90%, nitrogen protection: inhibit oxidation reaction, extend shelf life by 30%, actual application case: after a tea oil factory adopted this process, the vitamin E content in the product increased from 50mg / 100g in the traditional process to 85mg / 100g.

[0021] Energy-saving and environmentally friendly, it saves 40% energy compared to traditional hot air drying (energy consumption data: microwave treatment 8kW·h / ton vs. hot air drying 13kW·h / ton), reduces nitrogen consumption through a closed-loop system, reduces costs by 20%, has no chemical solvent residue, and reduces wastewater discharge by 60%, meeting green production standards.

[0022] High-efficiency separation and high purity, pre-pressing releases light oil, final pressure extracts heavy oil, comprehensive extraction efficiency increased by 25%, free fatty acids are accurately separated, acid value is reduced from 1.8mg KOH / g to 0.3mg KOH / g, refined oil meets EU food grade standards (acid value ≤0.6mg KOH / g), and export price is increased by 30%.

[0023] Flexibility and scalability. The sieve hole size can be adjusted according to different tea fruit varieties (for example, the sieve hole of oil tea fruit can be set to 12mm). For high-fiber raw materials (such as tea seeds), an enzymatic hydrolysis step is added to increase the oil yield by 5%-8%. It can be seamlessly connected with the existing pressing production line, and the transformation cost is as low as 100,000 yuan per line.

[0024] Safety and stability, cavity leakage <5mW / cm 2 , far below the international safety standard (10mW / cm 2 ), the oxygen concentration sensor gives a real-time alarm to avoid the risk of explosion,: the PLC system integrates parameters such as temperature, humidity, pressure, and speed, and the failure rate is reduced to 0.5%.

[0025] Economic and social benefits: comprehensive energy saving of 30%, annual electricity saving of about 500,000 yuan (based on daily processing of 10 tons), oil residue converted into feed or fertilizer, additional income increased by 15%. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a process flow chart of the present invention;

[0027] Figure 2 It is a schematic diagram of the process flow of the raw material screening and grading system of the present invention;

[0028] Figure 3 It is a schematic diagram of the process of the steam softening treatment system of the present invention;

[0029] Figure 4 It is a schematic diagram of the low temperature pressing system process of the present invention;

[0030] Figure 5 It is a schematic flow diagram of the molecular distillation refining system of the present invention. DETAILED DESCRIPTION

[0031] The following embodiments of the present invention are described in further detail in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0032] See also Figure 1-Figure 5 The present invention provides a high-efficiency pretreatment and low-temperature pressing process for improving the oil content of tea fruit, comprising the following steps:

[0033] (1) Screening and grading of tea fruit raw materials: Use a vibrating screen to grade by particle size and remove impurities;

[0034] (2) Steam softening treatment: soften the tea fruit in a saturated steam environment at a temperature of 80-95°C for 15-30 minutes;

[0035] (3) Microwave-assisted cell wall destruction: Use microwaves at a frequency of 2450 MHz and a power of 5-10 kW for 5-10 minutes to destroy the cell wall structure;

[0036] (4) Low temperature pressing: use a hydraulic press, control the pressing temperature to ≤50°C, the pressure to 20-35MPa, and press in two stages;

[0037] (5) Oil residue separation: The oil residue is separated by a centrifuge at a speed of 3000-5000 r / min to collect the tea fruit crude oil.

[0038] In step (1), the particle size classification standard of tea fruit is: the diameter of first-class fruit is ≥15mm, the diameter of second-class fruit is 10-15mm, and the diameter of third-class fruit is less than 10mm. After classification, the tea fruit is treated separately. In step (2), steam softening adopts an intermittent steam injection device, the steam humidity is 95%-100%, and the moisture content of the tea fruit after softening is controlled at 18%-22%. In step (3), microwave treatment adopts a multi-frequency alternating mode, including alternating radiation of low frequency band (915MHz) and high frequency band (2450MHz), and the total duration does not exceed 15 minutes.

[0039] In step (4), the low-temperature pressing is divided into two stages: pre-pressing and final pressing: the pre-pressing pressure is 10-15MPa and the time is 5 minutes; the final pressing pressure is 25-35MPa and the time is 10 minutes. The temperature during the whole pressing process is maintained at ≤50°C by a circulating cooling water system. In step (5), the oil residue after centrifugal separation is subjected to secondary pressing, the secondary pressing pressure is 40MPa, the temperature is ≤55°C, and the residual oil is extracted with the assistance of ultrasound. The hydraulic press is equipped with a nitrogen protection system, and the oxygen concentration is controlled below 5% during the pressing process to prevent oil oxidation.

[0040] The enzymatic hydrolysis step of the pretreated tea fruit is as follows: using cellulase and pectinase for composite enzymatic hydrolysis, the enzymatic hydrolysis temperature is 45-50°C, pH 4.5-5.5, and the time is 2-4 hours; the tea fruit after enzymatic hydrolysis is low-temperature dried to a moisture content of 8%-12%, the drying temperature is ≤40°C, and the time is 1-2 hours; the pressed tea fruit crude oil is refined by molecular distillation, the distillation temperature is 120-150°C, the vacuum degree is 0.1-1kPa, and free fatty acids and impurities are separated.

[0041] 1. Tea fruit screening and grading:

[0042] Equipment: Double-layer vibrating screening machine (upper layer sieve hole 15mm, lower layer 10mm);

[0043] Operation: The tea fruit is divided into three levels after vibration screening. The first-level fruit (≥15mm) goes directly into the steam softening tank, the second-level fruit (10-15mm) is crushed and processed, and the third-level fruit (<10mm) is used for by-product processing.

[0044] Parameters: vibration frequency 30Hz, processing capacity 500kg / h.

[0045] 2. Steam softening treatment:

[0046] Equipment: intermittent steam injection tank (pressure resistance 0.3MPa);

[0047] Operation: Spread the tea fruit on a mesh tray, pass 95℃ saturated steam (humidity 100%), process for 25 minutes, and the moisture content after softening is 20%;

[0048] Control: Adjust the steam valve opening through PLC and monitor the moisture content in real time (infrared moisture meter).

[0049] 3. Microwave-assisted cell wall breaking:

[0050] Equipment: Multi-frequency microwave processor (915MHz / 2450MHz alternating mode);

[0051] Operation: The tea fruit passes through the microwave cavity via a conveyor belt at a speed of 0.5m / min, with a total radiation time of 10 minutes (5 minutes at high frequency + 5 minutes at low frequency) and a power of 8kW;

[0052] Safety: The cavity shielding layer is grounded, and the microwave leakage is less than 5mW / cm 2 .

[0053] 4. Low temperature pressing:

[0054] Equipment: Hydraulic press (maximum pressure 40MPa);

[0055] operate:

[0056] Pre-pressing stage: pressure 12MPa, time 5 minutes, initial release of grease;

[0057] Final pressing stage: pressure 30MPa, time 10 minutes, circulating cooling water (inlet temperature 10℃) to maintain pressing temperature ≤50℃;

[0058] Nitrogen protection: The oxygen concentration in the pressing chamber is adjusted to 3%-5% in real time (nitrogen flow rate 2m 3 / h).

[0059] 5. Oil residue separation and secondary extraction:

[0060] Equipment: horizontal spiral centrifuge (speed 4500r / min);

[0061] Operation: After the oil residue from the first pressing is centrifuged, the residue enters the second pressing (pressure 40MPa, temperature 55℃, ultrasonic assisted frequency 28kHz), and the final residual oil rate is ≤4.5%.

[0062] 6. Enzymatic hydrolysis (optional):

[0063] Equipment: Stainless steel enzymatic hydrolysis tank (with stirring and temperature control);

[0064] Operation: After steam softening, add compound enzyme (cellulase 100U / g, pectinase 50U / g) to the tea fruit, pH 5.0, 50℃ enzymolysis for 3 hours;

[0065] Termination: After enzymatic hydrolysis, heat to 85°C and maintain for 10 minutes to inactivate the enzyme.

[0066] 7. Molecular distillation refining:

[0067] Equipment: short-path molecular distillation apparatus;

[0068] Operation: The squeezed crude oil is preheated to 80℃ and enters the distillation tank (temperature 130℃, vacuum degree 0.5kPa). The free fatty acids are separated through the condenser and the refined oleic acid value is ≤0.5mgKOH / g.

[0069] 8.Quality Control:

[0070] Detection items:

[0071] Oil yield (weight method);

[0072] Peroxide value (GB5009.227-2016);

[0073] Active substance content (polyphenols, vitamin E detected by HPLC).

[0074] Records: Record process parameters and test results for each batch to ensure traceability.

[0075] Example 1: Basic process

[0076] Raw material processing: The tea fruits are graded by a vibrating screening machine, and the first-grade fruits (diameter ≥ 15mm) enter the steam softening tank and are treated with steam at 95℃ for 20 minutes.

[0077] Microwave wall breaking: Use 2450MHz microwave treatment for 8 minutes, power 8kW.

[0078] Low temperature pressing: hydraulic press pre-pressing 12MPa / 5 minutes, final pressure 30MPa / 10 minutes, temperature ≤50℃.

[0079] Separation and refining: centrifugal separation (4000r / min), crude oil residual rate 6.5%, oil yield 22%.

[0080] Example 2: Enzymatic hydrolysis assisted process

[0081] New step: after steam softening, add complex enzyme (cellulase: pectinase = 2:1) to the tea fruit and perform enzymolysis at 50°C for 3 hours.

[0082] Effect: The cell wall decomposition rate increased to 95%, the oil yield increased to 25%, and the residual oil rate decreased to 4.8%.

[0083] Example 3: High-frequency-low-frequency alternating microwaves

[0084] Improvements: Microwave treatment uses alternating radiation of 915MHz and 2450MHz for a total duration of 12 minutes.

[0085] Effect: The wall breaking uniformity is improved, the oil yield is 24.5%, and the energy consumption is reduced by 15%.

[0086] Example 4: Nitrogen protection pressing

[0087] Equipment improvement: The press is equipped with a nitrogen circulation system, and the oxygen concentration is ≤5%.

[0088] Effect: The peroxide value of crude oil is reduced to 2meq / kg (5meq / kg in traditional process), and the shelf life is extended by 30%.

[0089] Example 5: Molecular distillation purification

[0090] New step: The free fatty acids are removed from the squeezed crude oil by molecular distillation (temperature 130°C, vacuum degree 0.5kPa).

[0091] Effect: The acid value is reduced from 1.8mgKOH / g to 0.3mgKOH / g, reaching the first-class edible oil standard.

[0092] Comparison of embodiments:

[0093] Comparison Items Example 1 Example 2 Example 3 Example 4 Example 5 Oil yield (%) 22 25 24.5 22 23.5 Residual oil rate (%) 6.5 4.8 5.2 6.0 5.0 Active substance retention rate 88％ 92％ 90％ 95％ 93％ Energy consumption Benchmarks <![CDATA[ + 10%]]> -15％ <![CDATA[ + 5%]]> <![CDATA[ + 20%]]> Applicable scenarios General High fiber raw materials Energy saving needs High oxidation risk High purity requirements

[0094] Conclusion: Example 2 (enzymatic hydrolysis assisted) has the best comprehensive performance and is suitable for high-fiber tea fruit; Example 5 (molecular distillation) is suitable for high-end refined oil production; Example 3 (alternating microwave) has significant advantages in the field of energy saving.

[0095] The embodiments of the present invention are given for the purpose of illustration and description, and are not intended to be exhaustive or to limit the invention to the disclosed forms. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are selected and described in order to better illustrate the principles and practical applications of the present invention and to enable those of ordinary skill in the art to understand the present invention and thereby design various embodiments with various modifications suitable for specific uses.

Claims

1. A high-efficiency pretreatment and low-temperature pressing process for improving the oil content of tea fruit, characterized in that: The following steps are involved: (1) Screening and grading of tea fruit raw materials: Use a vibrating screen to grade by particle size and remove impurities; (2) Steam softening treatment: soften the tea fruit in a saturated steam environment at a temperature of 80-95°C for 15-30 minutes; (3) Microwave-assisted cell wall destruction: Use microwaves at a frequency of 2450 MHz and a power of 5-10 kW for 5-10 minutes to destroy the cell wall structure; (4) Low temperature pressing: using a hydraulic press, controlling the pressing temperature to ≤50°C, the pressure to 20-35MPa, and pressing in two stages; (5) Oil residue separation: The oil residue is separated by a centrifuge at a speed of 3000-5000 r / min to collect the tea fruit crude oil.

2. The high-efficiency pretreatment and low-temperature pressing process for improving the oil content of tea fruit as claimed in claim 1, characterized in that: In step (1), the particle size classification standard of tea fruit is: the diameter of first-class fruit is ≥15mm, the diameter of second-class fruit is 10-15mm, and the diameter of third-class fruit is <10mm. After classification, they are processed separately.

3. The high-efficiency pretreatment and low-temperature pressing process for improving the oil content of tea fruit as claimed in claim 1, characterized in that: In step (2), the steam softening adopts an intermittent steam injection device, the steam humidity is 95%-100%, and the moisture content of the tea fruit after softening is controlled at 18%-22%.

4. The high-efficiency pretreatment and low-temperature pressing process for improving the oil content of tea fruit as claimed in claim 1, characterized in that: In step (3), the microwave treatment adopts a multi-frequency alternating mode, including alternating radiation of a low frequency band (915 MHz) and a high frequency band (2450 MHz), and the total duration does not exceed 15 minutes.

5. The high-efficiency pretreatment and low-temperature pressing process for improving the oil content of tea fruit as claimed in claim 1, characterized in that: In step (4), low-temperature pressing is divided into two stages: pre-pressing and final pressing: pre-pressing pressure is 10-15 MPa, time is 5 minutes; final pressing pressure is 25-35 MPa, time is 10 minutes, and the temperature during the whole pressing process is maintained at ≤50°C by a circulating cooling water system.

6. The high-efficiency pretreatment and low-temperature pressing process for improving the oil content of tea fruit as claimed in claim 1, characterized in that: After centrifugal separation in step (5), the oil residue is subjected to secondary pressing, the secondary pressing pressure is 40 MPa, the temperature is ≤55° C., and the residual oil is extracted with the assistance of ultrasound.

7. The high-efficiency pretreatment and low-temperature pressing process for improving the oil content of tea fruit as claimed in claim 1, characterized in that: The hydraulic press is equipped with a nitrogen protection system, and the oxygen concentration is controlled below 5% during the pressing process to prevent oil oxidation.

8. The high-efficiency pretreatment and low-temperature pressing process for improving the oil content of tea fruit as claimed in claim 1, characterized in that: The method also includes an enzymatic hydrolysis step of the tea fruit after the pretreatment: using a composite enzymatic hydrolysis of cellulase and pectinase, with an enzymatic hydrolysis temperature of 45-50° C., a pH of 4.5-5.5, and a time of 2-4 hours.

9. A high-efficiency pretreatment and low-temperature pressing process for improving the oil content of tea fruit as claimed in claim 8, characterized in that: After enzymatic hydrolysis, the tea fruit is dried at low temperature to a moisture content of 8%-12%, the drying temperature is ≤40°C, and the time is 1-2 hours.

10. The high-efficiency pretreatment and low-temperature pressing process for improving the oil content of tea fruit as claimed in claim 1, characterized in that: The pressed tea fruit crude oil is refined by molecular distillation at a distillation temperature of 120-150°C and a vacuum degree of 0.1-1kPa to separate free fatty acids and impurities.

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