Preparation method of coconut milk with high stability

Abstract

This invention provides a method for preparing highly stable coconut milk. A sugar extraction process is proposed and optimized for the first time, utilizing the hydrophilic and emulsifying properties of sugars to replace the traditional water extraction method, significantly improving the extraction effect. Coconut milk is obtained by mixing coconut meat with an 80wt% crystalline fructose solution, followed by cell wall disruption, cold extraction, and filtration. This process significantly improves the extraction rates of protein and oil in coconut milk, achieving a protein content of up to 27.15 mg / mL and an oil content of up to 194.25 mg / mL, which are 2.5 times and 8 times higher than those obtained by the traditional water extraction method, respectively. The resulting coconut milk has a small particle size (1.84 μm), a high zeta potential (-26.90 mV), and strong water-holding capacity (≥93%), exhibiting excellent stability under centrifugation, storage, freeze-thaw cycles, heat treatment, pH 3–9, and the presence of salt ions. This invention provides a highly efficient and stable new method for the industrial production of high-quality coconut milk.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, and specifically to a method for preparing coconut milk with high stability. Background Technology

[0002] Coconut, belonging to the genus *Cocos nucifera* L. of the palm family, is an important economic crop in tropical regions. Its flesh is rich in protein and oil, possessing health benefits such as lowering blood lipids and cholesterol, and is extremely nutritious. Furthermore, coconut flesh contains various vitamins (such as vitamin E and B vitamins) and minerals (such as potassium, calcium, and magnesium), further enhancing its nutritional value. Coconut milk, a milky white liquid obtained by pressing coconut flesh, is rich in nutrients such as fat, protein, vitamins, and minerals, and is widely used in the food processing and beverage industries.

[0003] Currently, commercially available coconut milk products are mainly prepared using the traditional water extraction process. This involves using water as a medium to soak and press coconut meat to obtain the pulp, often with the addition of stabilizers such as polysaccharides (xanthan gum and carrageenan) to maintain system stability. However, this traditional method has significant limitations: low extraction efficiency, with some protein and oil remaining in the coconut residue, resulting in resource waste; and poor stability of the resulting coconut milk, which is prone to problems such as fat floating, protein precipitation, and stratification during storage, severely affecting product shelf life and sensory quality. Furthermore, the excessive use of chemical stabilizers to maintain stability may not only lead to an unnatural taste but also contradicts the current trend of healthy consumption with clean labels. The limitations of existing processes result in low utilization rates of coconut meat, hindering the development of the coconut processing industry and the efficient utilization of coconut resources. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing coconut milk that does not require the addition of emulsifiers, thereby solving the problems of poor stability and low extraction efficiency in coconut milk preparation and realizing the green and efficient development of coconut meat.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing coconut milk with high stability includes the following steps: (1) Raw material preparation: Cut the coconut meat into small pieces and grind it into fine powder using a grinder.

[0006] (2) Sugar screening and concentration optimization: Through comparative experiments, crystalline fructose was selected as the sugar for extraction, with a solution concentration of 80% (w / w).

[0007] (3) Mixing: Mix the crushed coconut meat with 80wt% crystalline fructose solution at a mass ratio of 1:1 to 1:5.

[0008] (4) Cell wall breaking treatment: The mixture obtained in step (3) is continuously broken down using a crusher until the system is uniform and fine.

[0009] (5) Cold extraction: Seal the mixture after cell wall breaking and place it at 4℃ for 2-7 days for extraction.

[0010] (6) Filtration: After extraction, filter using a 300-mesh sieve to obtain the highly stable coconut milk.

[0011] Preferably, the mass ratio of the coconut meat to the crystalline fructose solution is 1:2.

[0012] Preferably, the extraction time is 5 days.

[0013] Preferably, the coconut milk product prepared by the method described above has a protein content ≥25 mg / mL, an oil content ≥190 mg / mL, an average particle size D(4,3) ≤3.0 μm, a Zeta potential ≤-18 mV, and a water holding capacity ≥93%.

[0014] Compared with the prior art, the advantages of the present invention are as follows: This invention utilizes the hydrophilic and emulsifying properties of sugars to prepare coconut milk via sugar extraction, significantly improving the extraction rates of proteins and fats and enhancing the stability of the extracts. Compared to traditional water extraction, sugar extraction uses sugars such as crystalline fructose as the extraction medium, which not only improves the solubility and stability of the target substances but also effectively reduces precipitation and stratification by enhancing the steric hindrance and electrostatic repulsion of the system, thus comprehensively improving the physicochemical properties and storage stability of coconut milk. Attached Figure Description

[0015] Figure 1 Protein content (A) and fat content (B) of coconut milk with different extraction ratios / extraction methods; Figure 2 Particle size of coconut milk from different extraction ratios / extraction methods; Figure 3 Visual appearance of coconut milk after repeated freeze-thaw cycles using different extraction methods; Figure 4 Proteins, lipids (A), and particle size potential (B) of coconut milk extracted under different media. Figure 5 The emulsification index (A) and oscillation frequency scan curve (B) of coconut milk from different extraction media stored at 4℃ for 14 days. Figure 6 Protein, lipid (A), and particle size potential (B) of coconut milk with different fructose extraction concentrations. Figure 7 Protein and lipid content (A) and particle size distribution (B) of coconut milk extracted at different times; Figure 8Flow curves (A) and oscillation frequencies (B) of coconut milk at different extraction times; Figure 9 The preferred embodiment demonstrates the storage stability of coconut milk; Figure 10 Particle size (A) and visual appearance (B) of coconut milk after three freeze-thaw cycles in the preferred embodiment; Figure 11 Particle size (A) and visual appearance (B) of coconut milk after heating, according to preferred embodiments; Figure 12 Particle size (A) and visual appearance (B) of coconut milk after heating, according to preferred embodiments; Figure 13 Particle size (A) and appearance (B) of coconut milk at different salt ion concentrations in the preferred embodiment. Detailed Implementation

[0016] To make the above-mentioned features and advantages of the present invention more apparent and understandable, specific embodiments are provided below for detailed description. Unless otherwise specified, the methods of the present invention are conventional methods in the art. Example

[0017] The method for preparing coconut milk provided by this invention includes the following steps: (1) Raw material preparation: Cut the coconut meat into small pieces and grind it into fine powder using a grinder.

[0018] (2) Sugar screening and concentration optimization: Through comparative experiments, crystalline fructose was selected as the sugar for extraction, with a solution concentration of 80% (w / w).

[0019] (3) Mixing: Mix the crushed coconut meat with 80wt% crystalline fructose solution at a mass ratio of 1:1 to 1:5.

[0020] (4) Cell wall breaking treatment: The mixture obtained in step (3) is continuously broken down using a crusher until the system is uniform and fine.

[0021] (5) Cold extraction: Seal the mixture after cell wall breaking and place it at 4℃ for 2-7 days for extraction.

[0022] (6) Filtration: After extraction, filter using a 300-mesh sieve to obtain the highly stable coconut milk.

[0023] Screening of the extraction medium to feed ratio

[0024] To investigate the effects of extraction medium and material-to-liquid ratio on the quality of coconut milk, coconut meat was mixed with 80% (w / w) crystalline fructose solution (sugar extraction method) and pure water (water extraction method) in different proportions, extracted at 4℃ for 5 days, and then filtered for analysis.

[0025] Example 1: The extraction medium was an 80% (w / w) crystalline fructose solution, and the mass ratio of coconut meat to the extraction medium was 1:2.

[0026] Example 2: The extraction medium was an 80% (w / w) crystalline fructose solution, and the mass ratio of coconut meat to the extraction medium was 1:3.

[0027] Example 3: The extraction medium was an 80% (w / w) crystalline fructose solution, and the mass ratio of coconut meat to the extraction medium was 1:4.

[0028] Example 4: The extraction medium was an 80% (w / w) crystalline fructose solution, and the mass ratio of coconut meat to the extraction medium was 1:5.

[0029] Comparative Example 1: The extraction medium was pure water, and the mass ratio of coconut meat to water was 1:2.

[0030] The results showed that the protein and oil content extracted by sugar extraction was significantly higher than that extracted by water extraction: taking a solid-liquid ratio of 1:2 as an example, the protein content in Example 1 was 27.15 mg / mL, approximately 2.5 times that of Comparative Example 1; the oil content was 194.25 mg / mL, approximately 8 times that of Comparative Example 1. Furthermore, both protein and oil content decreased with increasing solid-liquid ratio, indicating that a lower solid-liquid ratio is more conducive to extraction.

[0031] Regarding particle size, the average particle size of Example 1 was 1.84 µm, which was much smaller than that of Comparative Example 1 (65.10 µm), and the particle size remained small under different feed-to-liquid ratios. Figure 2 This indicates that the emulsion formed by sugar extraction is finer and more stable. Sugar molecules interact with proteins through hydrogen bonds to form a core-shell structure, reducing interfacial tension and inhibiting droplet aggregation.

[0032] Stability observations show that, as Figure 3 As shown, the coconut milk extracted by sugar in Example 1 remained homogeneous after three freeze-thaw cycles and standing, and its centrifugal water-holding capacity (2 mL sample centrifuged at 861×g for 10 min, the appearance of layering was recorded, and the result was calculated according to the formula) reached 95.89%; while the coconut milk extracted by water showed obvious demulsification and layering. In summary, the sugar extraction method achieves the best extraction efficiency and emulsion stability at a material-to-liquid ratio of 1:2, so this ratio will be used for subsequent optimization.

[0033] Sugar screening and concentration optimization

[0034] Based on the established optimal material-to-liquid ratio of 1:2, the optimal sugars and their concentrations were further screened. With the coconut meat to extraction medium mass ratio fixed at 1:2, extraction was carried out at 4℃ for 5 days, and the following comparative experiment was conducted.

[0035] Example 5: The extraction medium was a 40% (w / w) glucose solution (saturated concentration).

[0036] Example 6: The extraction medium was a 60% (w / w) sucrose solution (saturated concentration).

[0037] Example 7: The extraction medium was an 80% (w / w) crystalline fructose solution (saturated concentration).

[0038] Example 8: The extraction medium was a 60% (w / w) crystalline fructose solution.

[0039] Example 9: The extraction medium was a 40% (w / w) crystalline fructose solution.

[0040] The key physicochemical indicators of the above examples were measured. The results showed that, under the same material-to-liquid ratio (1:2), Example 7 (80% crystalline fructose) exhibited the most outstanding extraction effect, with protein and oil contents reaching 27.15 mg / mL and 194.25 mg / mL, respectively. Furthermore, under the same extraction conditions, the extraction effect of crystalline fructose was superior to that of sucrose (Example 6) and glucose (Example 5). Further concentration comparison showed that the extraction efficiency of the 80% crystalline fructose solution (Example 7) was significantly higher than that of 60% (Example 8) and 40% (Example 9). Regarding emulsion properties, the sugar extraction method resulted in a significantly more stable and refined emulsion system. Example 7 had the smallest particle size (1.84 µm) and the highest Zeta potential (-26.90 mV), indicating excellent emulsion dispersibility and strong electrostatic repulsion. In contrast, Comparative Example 1 had a particle size as high as 65.10 µm and a potential of only about -5.20 mV, indicating significantly insufficient system stability.

[0041] To further verify the influence of different sugars on the structural stability of coconut milk from a macroscopic rheological perspective, oscillation frequency scanning tests were performed on the samples from Examples 5-7. Figure 5 The results showed that all coconut milk prepared by sugar extraction methods (Examples 5-7) exhibited typical weak gel characteristics, meaning that the storage modulus (G′) was higher than the loss modulus (G″) throughout the entire test frequency range (0.1-10 Hz). Among them, the sample of Example 7, using 80% crystalline fructose, had significantly higher G′ and G″ modulus values ​​than the samples using 40% glucose (Example 5) and 60% sucrose (Example 6), especially in the low-frequency region (<1 Hz), indicating that it formed the strongest three-dimensional network structure and had the best long-term stability. These rheological results are completely consistent with the aforementioned trends in extraction rate, particle size, and potential, macroscopically confirming the crucial role of crystalline fructose, especially at high concentrations (80%), in constructing and stabilizing the coconut milk emulsion structure.

[0042] This advantage is further demonstrated in long-term storage and freeze-thaw treatment: In a 14-day storage test, the coconut milk emulsification index (CI: H) was measured using the formula for observing emulsion separation (especially in Example 7) of crystalline fructose (especially in Example 7).S Upper whey layer height / H T The total emulsion height (x100%) remained at 0 throughout, and no visible stratification occurred, demonstrating excellent long-term resistance to stratification. Furthermore, after freezing at -20°C and thawing at room temperature, none of the sugar extraction examples (5-9) exhibited demulsification or oil-water separation, a stark contrast to the water extraction method, which showed significant demulsification and oil separation after three repeated freeze-thaw cycles. This clearly demonstrates that the addition of sugars effectively strengthens the emulsion network structure of coconut milk, giving it both excellent storage stability and freeze-thaw stability.

[0043] Based on a comprehensive analysis of extraction efficiency, emulsion properties, rheological data, and preliminary stability data, crystalline fructose, especially at a concentration of 80% (w / w), is the optimal sugar for extraction.

[0044] The above results confirm that crystalline fructose, especially an 80% concentration solution, is the key extraction medium of this invention. Its hydrophilic groups can interact with the proteins and oils in coconut meat through hydrogen bonds, significantly improving the solubility and emulsification of the target components, thereby greatly enhancing the extraction rate and the initial stability of the system.

[0045] Extraction time optimization

[0046] After determining that the optimal extraction medium was 80% crystalline fructose solution, the effect of extraction time (2-7 days) on the overall quality of coconut milk was investigated at 4℃.

[0047] Example 10: Extraction time was 2 days.

[0048] Example 11: Extraction time was 3 days.

[0049] Example 12: Extraction time was 4 days.

[0050] Example 13 (Preferred Example): Extraction time is 5 days.

[0051] Example 14: Extraction time was 6 days.

[0052] Example 15: Extraction time was 7 days.

[0053] The results showed that extraction time had a significant impact on the extraction efficiency and emulsion stability of coconut milk. As the extraction time increased from 2 days to 7 days, the extraction rates of protein and oil generally increased, with the protein content peaking on day 5 (approximately 27.15 mg / mL) and the oil content also peaking on day 5 (approximately 194.25 mg / mL). Simultaneously, the average particle size gradually decreased and stabilized with increasing extraction time up to day 5 (approximately 1.84 µm in Example 13), while the absolute value of the Zeta potential increased accordingly (approximately -26.90 mV in Example 13), indicating that the emulsion structure tended to improve as the extraction process progressed.

[0054] To investigate the effect of extraction time on the macroscopic structural properties of coconut milk, systematic rheological characterization was performed on samples extracted at different times (1-7 days). Oscillation frequency scanning results ( Figure 8 (Figure B) shows that samples at all extraction times exhibited weak gel behavior with G′>G″, indicating that an emulsion gel network had formed. As the extraction time increased from day 2 to day 5, the moduli of G′ and G″ showed a continuous upward trend, reaching a peak on day 5, indicating that the internal network structure continuously strengthened with prolonged extraction time. However, when the extraction time was further extended to day 6 and day 7, the moduli decreased slightly, indicating that over-extraction may have led to rearrangement or weakening of some protein structures, which in turn had a slight impact on the integrity of the gel network. The flow curves of the steady-state shear test (…) Figure 8 Figure A) further confirms this conclusion: all samples exhibited shear-thinning behavior, and the apparent viscosity at the same shear rate first increased and then slightly decreased with prolonged extraction time. The sample on day 5 showed the highest apparent viscosity in the low-shear region, reflecting the most stable internal structure. These rheological data intuitively demonstrate from a kinetic perspective that 5 days of extraction is the critical point for the optimal strength of the internal network structure of coconut milk. If the extraction time is too short (<5 days), the network has not yet fully developed; if the extraction time is too long (>5 days), although the structure has basically formed, there may be a risk of microstructural weakening due to over-extraction. Therefore, considering the extraction rate, particle size, potential, and rheological properties, 5 days of extraction is the optimal process parameter.

[0055] Comprehensive stability tests were conducted on the sample of the preferred embodiment 13, with an extraction time of 5 days. The results confirmed that the coconut milk maintained excellent stability under a variety of harsh conditions: In terms of storage stability, after 30 days of storage at 4°C, the particle size only increased slightly from 1.84 µm to 1.97 µm; after three complete freeze-thaw cycles, the appearance was uniform without stratification, and the average particle size only increased to 2.13 µm; in terms of thermal stability, after heating in a water bath at 60°C, 80°C, and 100°C for 30 minutes, the particle size only increased slightly and the system remained uniform; after 7 days of storage in a wide pH range of 3-9, only slight stratification occurred at pH 9, and the system remained uniform under other conditions; after 7 days of storage in a solution with a NaCl concentration as high as 0.6 mol / L, there was no obvious oil precipitation, and the particle size remained below 3.0 µm, showing good tolerance to high ionic strength.

[0056] Through systematic examples and comparative studies, it can be clearly seen that: An 80% (w / w) crystalline fructose solution is the optimal alternative to water as the extraction medium, simultaneously achieving a multiple-fold increase in extraction efficiency and a fundamental improvement in the initial stability of the emulsion. Under the optimized conditions, extraction for 5 days is the best time point for comprehensively balancing extraction efficiency, various physicochemical indicators of the product, and results from multiple stability tests. Coconut milk prepared using the above optimized process (80% crystalline fructose, a material-to-liquid ratio of 1:2, extraction at 4°C for 5 days) not only exhibits high protein and oil extraction rates (2.5 times and 8 times, respectively, compared to traditional water extraction), but also demonstrates comprehensive and excellent stability under centrifugation, long-term storage, freeze-thaw cycles, heating, a wide pH range, and high salt ion concentrations, completely eliminating the need for exogenous chemical stabilizers. This invention successfully constructs a highly efficient, stable, and environmentally friendly coconut milk sugar extraction process, providing a reliable technical solution for the development of high-quality coconut milk products.

[0057] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for preparing coconut milk with high stability, characterized in that, Includes the following steps: (1) Raw material preparation: Cut the coconut meat into small pieces and grind it into fine powder using a grinder; (2) Sugar selection: Crystalline fructose was selected as the sugar for extraction, with a solution concentration of 80 wt%; (3) Mixing: Mix the crushed coconut meat with 80wt% crystalline fructose solution at a mass ratio of 1:1 to 1:5; (4) Cell wall breaking treatment: The mixture obtained in step (3) is subjected to continuous cell wall breaking treatment using a crusher until the system is uniform and fine; (5) Cold extraction: Seal the mixture after cell wall disruption and let it stand at 4℃ for 2-7 days for extraction; (6) Filtration: After extraction, filter using a 300-mesh sieve to obtain the highly stable coconut milk.

2. The preparation method according to claim 1, characterized in that, The mass ratio of coconut meat to crystalline fructose solution in step (2) is 1:

2.

3. The preparation method according to claim 1, characterized in that, The static extraction time described in step (5) is 5 days.

4. A coconut milk with high stability, characterized in that, It is prepared by any one of claims 1 to 3.

5. The coconut milk product according to claim 4, characterized in that, Its protein content is ≥25 mg / mL and its fat content is ≥190 mg / mL.

6. The coconut milk product according to claim 4, characterized in that, Its average particle size D(4,3)≤3.0 μm and Zeta potential≤-18 mV.

7. The coconut milk product according to claim 4, characterized in that, Its water holding capacity is ≥93%.

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