A method for the production of citrus essence by cold pressing

Abstract

This invention discloses a low-temperature pressing method for preparing citrus flavorings, relating to the field of fragrance and flavor technology. The method includes: crushing citrus peel to obtain peel particles; enzymatically hydrolyzing the peel particles under an inert gas atmosphere using cellulase and pectinase to obtain hydrolysate; mechanically pressing the hydrolysate under inert gas protection and temperature-controlled cooling to obtain an oil-water mixture; centrifuging the oil-water mixture and dehydrating the resulting upper phase to obtain crude citrus essential oil; performing short-path molecular distillation on the crude citrus essential oil to obtain distillate; collecting the fore-and-after fractions and main fractions of the distillate in the order of distillation to obtain light and heavy flavorings; and employing a synergistic process of combined enzymatic hydrolysis under inert gas protection, low-temperature controlled pressing, vacuum dehydration, and short-path molecular distillation for fractional collection to effectively suppress oxidation and loss of heat-sensitive aroma components.

Description

Technical Field

[0001] This invention relates to the field of fragrance and flavor technology, and in particular to a low-temperature pressing method for preparing citrus flavoring. Background Technology

[0002] Fragrance and flavor technology is an interdisciplinary field that studies the extraction, synthesis, blending, stabilization, and application of natural or synthetic fragrance raw materials in the food, daily chemical, tobacco, and pharmaceutical industries. It covers the analysis and identification of aroma components, fragrance design, sustained-release technology, microencapsulation, sensory evaluation, and production process optimization. The aim is to accurately construct and deliver specific olfactory experiences through scientific means to meet consumers' needs for product aroma quality, safety, and functionality.

[0003] Traditional steam distillation requires operation at a high temperature of around 100℃, which causes a large number of low-boiling-point, highly volatile terpenes in citrus essential oils to oxidize, polymerize, or isomerize, resulting in distorted aromas and loss of the characteristic fragrance of fresh fruit peels. Although the ordinary cold-pressing method retains some natural aromas, the resulting crude essential oil contains waxes, pigments, water, and high-boiling-point impurities, and the light and heavy components are not separated, resulting in an initial burst of aroma that lacks staying power, making it difficult to meet the requirements of high-end applications such as daily chemicals and food for aroma complexity and purity. Summary of the Invention

[0004] In view of the aforementioned existing problems, the present invention is proposed.

[0005] Therefore, this invention provides a low-temperature pressing method for preparing citrus flavorings, which solves the problem that traditional steam distillation requires operation at a high temperature of around 100°C, causing a large number of low-boiling-point, highly volatile terpenes in citrus essential oils to oxidize, polymerize, or isomerize, resulting in distorted aromas and loss of the characteristic fragrance of fresh fruit peels. Furthermore, although ordinary cold pressing methods retain some natural aromas, the resulting crude essential oils contain waxes, pigments, water, and high-boiling-point impurities, and the light and heavy components are not separated, resulting in an initial strong aroma that lacks staying power, making it difficult to meet the requirements of high-end applications such as daily chemicals and food for aroma layering and purity.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: This invention provides a low-temperature pressing method for preparing citrus flavoring, comprising: The citrus peel is crushed to obtain peel particles; The fruit peel particles were enzymatically hydrolyzed using cellulase and pectinase under an inert gas atmosphere to obtain the hydrolyzed material. The enzymatically hydrolyzed material is mechanically pressed under inert gas protection and cooling temperature control to obtain an oil-water mixture; The oil-water mixture was centrifuged and the resulting upper phase was dehydrated to obtain crude citrus essential oil. The crude citrus essential oil was subjected to short-path molecular distillation to obtain the distillate; The fore-and-after fractions and the main fractions of the distillation products are collected in the order of distillation to obtain light component flavorings and heavy component flavorings.

[0007] In a preferred embodiment of the low-temperature pressing method for preparing citrus flavoring according to the present invention, the particle size of the peel particles is 3 mm to 5 mm.

[0008] In a preferred embodiment of the low-temperature pressing method for preparing citrus flavoring according to the present invention, the enzymatic hydrolysis process involves a cellulase to pectinase mass ratio of 1:1 to 1:3, and a total enzyme addition amount of 0.2% to 0.8% of the peel particle mass.

[0009] As a preferred embodiment of the low-temperature pressing method for preparing citrus flavoring according to the present invention, the enzymatic hydrolysis is carried out under conditions of pH 4.5 to 5.5 and temperature 30°C to 35°C, and the reaction time is 40 min to 80 min.

[0010] In a preferred embodiment of the low-temperature pressing method for preparing citrus flavoring according to the present invention, the inert gas is nitrogen, and the oxygen concentration in the reaction system during enzymatic hydrolysis and pressing is ≤0.5% (v / v).

[0011] As a preferred embodiment of the low-temperature pressing preparation method of the citrus flavoring of the present invention, the mechanical pressing is carried out in a fully enclosed pressing device, the pressing pressure is 0.8 MPa to 1.2 MPa, and the material temperature is ≤25℃ during the pressing process.

[0012] As a preferred embodiment of the low-temperature pressing preparation method of the citrus flavoring of the present invention, the centrifugation is carried out at 4℃±1℃ and a rotation speed of 3500 rpm to 4500 rpm for a centrifugation time of 8 min to 12 min.

[0013] As a preferred embodiment of the low-temperature pressing preparation method of the citrus flavoring of the present invention, the dehydration treatment is carried out under the conditions of absolute vacuum degree ≤5 kPa and temperature of 18℃ to 22℃, and the dehydration time is 1.5 h to 2.5 h.

[0014] As a preferred embodiment of the low-temperature pressing preparation method of the citrus flavoring described in this invention, the short-path molecular distillation is carried out under the conditions of system absolute pressure ≤ 0.5 Pa, evaporation surface temperature of 58°C to 62°C, and condensation surface temperature of 4°C to 6°C.

[0015] In a preferred embodiment of the low-temperature pressing method for preparing citrus flavoring according to the present invention, the first fraction is collected during the first 30% ± 5% of the distillation time after the start of distillation, and the main fraction is collected during the subsequent 60% ± 5% of the distillation time.

[0016] The beneficial effects of this invention are as follows: by employing a synergistic process of compound enzymatic hydrolysis under inert gas protection, low-temperature temperature-controlled pressing, vacuum dehydration, and short-path molecular distillation fractionation, the yield, aroma purity, and flavor fidelity of citrus flavorings are effectively improved while effectively inhibiting the loss of oxidation and heat-sensitive aroma components. The resulting light component flavorings are rich in refreshing volatile terpenes, while the heavy component flavorings retain abundant oxygen-containing derivatives. Both can be used alone or in combination to meet different aroma requirements. The overall process conditions are mild, highly controllable, and have good repeatability. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of the low-temperature pressing preparation method of citrus flavoring in Example 1. Detailed Implementation

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0020] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0021] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0022] Example 1, referring to Figure 1 This is the first embodiment of the present invention, which provides a method for preparing citrus flavoring by low-temperature pressing, comprising: Take 500 g of ripe Newhall navel orange peel from southern Jiangxi (use within 24 hours of picking, remove the white pith, and wash with clean water), crush it with a universal grinder, and sieve it to obtain peel particles with a particle size of 4.0±0.2 mm.

[0023] The particles were added to a 5 L glass reactor and high-purity nitrogen (99.999%) was introduced for 30 min to reduce the oxygen concentration of the system to 0.3% (v / v).

[0024] Add cellulase and pectinase at a mass ratio of 1:2, with a total addition amount of 0.5% of the peel mass. Adjust the pH to 5.0 with citrate-disodium hydrogen phosphate buffer and stir in a 32℃ water bath for 60 min for enzymatic hydrolysis.

[0025] The enzymatic hydrolysate was transferred to a fully enclosed hydraulic screw press and pressed for 15 minutes at 1.0 MPa under nitrogen positive pressure (0.05 MPa). Cooling water at 10℃ was circulated through the jacket, and the material temperature was maintained at 23±1℃. The oil-water mixture was collected.

[0026] The mixture was centrifuged in a high-speed refrigerated centrifuge at 4°C and 4000 rpm for 10 min, and the upper oil phase was collected.

[0027] The oil phase was placed in a rotary evaporator and dehydrated for 2.0 h under an absolute vacuum of 4 kPa and a water bath at 20°C to obtain 4.85 g of crude citrus essential oil.

[0028] Crude essential oils are processed using a short-path molecular distillation apparatus: The system absolute pressure is 0.4 Pa, the evaporation surface temperature is 60℃, the condensation surface temperature is 5℃, and the feed rate is 2 mL / min.

[0029] Automatic collection based on distillation time ratio: the first 30% of the time is for the light component (1.48 g), the next 60% of the time is for the heavy component (2.92 g), and the residue of 0.45 g is discarded.

[0030] Test results: Total yield: 0.97% (based on fresh fruit peel); GC-MS conditions: HP-5MS capillary column (30 m × 0.25 mm × 0.25 μm), temperature program 50℃ (2 min) → 8℃ / min → 250℃ (10 min); Light components: limonene 82.3%, α-pinene 4.1%, β-myrcene 3.8%; Heavy components: linalool 18.6%, linalyl acetate 15.2%, geraniol 4.9%; Peroxide value (POV): 0.8 meq / kg; Sensory evaluation: Top note freshness 4.6, body scent smoothness 4.4, no off-odor (score ≥ 4.0 is acceptable).

[0031] Example 2 (Verification of particle size range 3 mm vs 5 mm) Except for the pericarp particle sizes of 3.0 mm and 5.0 mm, the other conditions were the same as in Example 1.

[0032] result: Particle size 3 mm: yield 0.89%, high viscosity of enzymatic hydrolysate, and high pressing resistance; Particle size 5 mm: yield 0.91%, but enzymatic hydrolysis was incomplete (cell wall integrity rate of residue >30% under microscopic observation). The aroma components of both were not significantly different from those of Example 1 (GC-MS relative deviation <5%), proving that they can be effectively implemented in the range of 3–5 mm.

[0033] Example 3 (Verification of enzyme ratio and dosage boundaries) Keeping other conditions constant, test separately: (a) Enzyme ratio 1:1, total enzyme content 0.2%; (b) Enzyme ratio 1:3, total enzyme amount 0.8%.

[0034] result: (a) Yield 0.85%, oxygen content of the heavy component 36.1%; (b) Yield 0.98%, but cost increased, and aroma was not further improved; This demonstrates that the enzyme ratio of 1:1–1:3 and the dosage of 0.2%–0.8% as defined in the claims are reasonable and feasible.

[0035] Example 4 (Verification of critical oxygen concentration) The oxygen concentrations were set to 0.5%, 1.0%, and 2.0%, respectively, with the rest being the same as in Example 1.

[0036] result: Oxygen concentration ≤0.5%: POV ≤1.0 meq / kg, no oxidizing odor; Oxygen concentration 1.0%: POV = 2.8 meq / kg, slight stale smell appears; Oxygen concentration 2.0%: POV = 6.5 meq / kg, with a distinct rancid smell; This demonstrates that an oxygen concentration of ≤0.5% is the critical threshold for ensuring aroma stability.

[0037] Comparative Example 1 (without inert gas protection) Enzymatic hydrolysis and pressing were carried out in air (oxygen concentration ≈ 21%), and the rest was the same as in Example 1.

[0038] Results: Yield 0.78%, POV=7.2 meq / kg, limonene oxidation products in the light components reached 8.5%, and the sensory score of top aroma was only 2.8 points.

[0039] Comparative Example 2 (molecular distillation fractionation omitted) The crude essential oil is used directly as a product without distillation.

[0040] Results: Although the yield was 1.02%, the aroma was strong at the beginning and weak at the end. After 7 days of accelerated storage at 40°C, the POV increased to 12.3 meq / kg, while the graded product of this invention only increased to 2.1 meq / kg, proving that grading significantly improves stability and aroma controllability.

[0041] In summary, this invention employs a synergistic process involving enzymatic hydrolysis under inert gas protection, low-temperature controlled pressing, vacuum dehydration, and short-path molecular distillation for fractional collection. This effectively inhibits oxidation and the loss of heat-sensitive aroma components while significantly improving the yield, aroma purity, and flavor fidelity of citrus flavorings. The resulting light component flavorings are rich in refreshing volatile terpenes, while the heavy component flavorings retain abundant oxygen-containing derivatives. Both can be used alone or in combination to meet different aroma requirements. The overall process conditions are mild, highly controllable, and reproducible.

[0042] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing citrus flavoring by low-temperature pressing, characterized in that: include: The citrus peel is crushed to obtain peel particles; The fruit peel particles were enzymatically hydrolyzed using cellulase and pectinase under an inert gas atmosphere to obtain the hydrolyzed material. The enzymatically hydrolyzed material is mechanically pressed under inert gas protection and cooling temperature control to obtain an oil-water mixture; The oil-water mixture was centrifuged and the resulting upper phase was dehydrated to obtain crude citrus essential oil. The crude citrus essential oil was subjected to short-path molecular distillation to obtain the distillate; The fore-and-after fractions and the main fractions of the distillation products are collected in the order of distillation to obtain light component flavorings and heavy component flavorings.

2. The low-temperature pressing method for preparing citrus flavoring as described in claim 1, characterized in that: The particle size of the fruit peel particles is 3 mm to 5 mm.

3. The low-temperature pressing method for preparing citrus flavoring as described in claim 2, characterized in that: In the enzymatic hydrolysis treatment, the mass ratio of cellulase to pectinase is 1:1 to 1:3, and the total amount of enzyme added is 0.2% to 0.8% of the mass of the peel particles.

4. The low-temperature pressing method for preparing citrus flavoring as described in claim 3, characterized in that: The enzymatic hydrolysis was carried out at a pH of 4.5 to 5.5 and a temperature of 30°C to 35°C for a reaction time of 40 min to 80 min.

5. The low-temperature pressing method for preparing citrus flavoring as described in claim 4, characterized in that: The inert gas is nitrogen, and the oxygen concentration in the reaction system during enzymatic hydrolysis and pressing is ≤0.5% (v / v).

6. The low-temperature pressing method for preparing citrus flavoring as described in claim 5, characterized in that: The mechanical pressing is carried out in a fully enclosed pressing device with a pressing pressure of 0.8 MPa to 1.2 MPa and a material temperature of ≤25℃ during the pressing process.

7. The low-temperature pressing method for preparing citrus flavoring as described in claim 6, characterized in that: The centrifugation was carried out at 4℃±1℃, with a rotation speed of 3500 rpm to 4500 rpm, and a centrifugation time of 8 min to 12 min.

8. The low-temperature pressing method for preparing citrus flavoring as described in claim 7, characterized in that: The dehydration process is carried out under conditions of absolute vacuum ≤5 kPa and temperature of 18℃ to 22℃, with a dehydration time of 1.5 h to 2.5 h.

9. The low-temperature pressing method for preparing citrus flavoring as described in claim 8, characterized in that: The short-range molecular distillation is carried out under the conditions of system absolute pressure ≤0.5 Pa, evaporation surface temperature of 58℃ to 62℃, and condensation surface temperature of 4℃ to 6℃.

10. The method for preparing citrus flavoring by low-temperature pressing as described in claim 9, characterized in that: The fore-section fraction is collected during the first 30% ± 5% of the distillation time after the start of distillation, and the main-section fraction is collected during the subsequent 60% ± 5% of the distillation time.

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