Coconut meat processing method and product thereof

Abstract

The invention relates to the technical field of fruit processing, in particular to a processing method of coconut meat with shells and a product thereof. According to the method, free water of endocarp (coconut shells) is removed through surface drying, the surface cracking rate of the coconut meat with the shells in the freezing process is remarkably reduced through staged slow freezing, and meanwhile the flavor of the coconut meat and the flavor of coconut water are effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fruit processing, in particular to a processing method of coconut meat with shell and a product thereof. BACKGROUND

[0002] Coconut is a tropical specialty fruit, and its flesh and water are rich in nutrients, which are widely favored by consumers. In recent years, with the development of cold chain logistics and frozen food technology, frozen coconut with shell has gradually become a high-end instant product on the market. This kind of product retains the complete coconut shell, contains fresh coconut meat and coconut water inside, and can be directly drunk or eaten after thawing, combining convenience and original ecological flavor. However, in the actual production process, the problem of surface cracks of coconut shell caused by freezing has long plagued the industry, seriously restricting the product yield and commodity value.

[0003] Traditional freezing processes usually use direct quick freezing or simple pre-cooling methods to process coconuts with shells. Because coconuts contain a large amount of free water (especially coconut water), the volume of water expands by about 9% during freezing, generating significant internal pressure; at the same time, the coconut shell itself is a porous and brittle material, if the internal pressure cannot be effectively released, it is easy to form micro-cracks or even burst on the surface of the shell. Once the coconut shell is damaged, not only does it cause coconut water leakage and microbial contamination, but it also accelerates oxidation and deterioration, seriously affecting product safety and shelf life.

[0004] To alleviate the problem of cracking of coconut shell during freezing, some enterprises try to make local through holes on the coconut shell, such as punching the natural eye, to release the expansion pressure generated by the freezing of internal water. However, this method has obvious defects: after the hole is opened, external oxygen is easy to enter the coconut cavity through the hole, accelerating the oxidation of polyphenols in coconut meat and coconut water, causing browning; at the same time, the opening of the hole also destroys the natural closed barrier of the coconut, significantly increasing the risk of microbial contamination. Even if the hole is plugged after freezing is completed, it is difficult to completely restore its original sealing, and the additional process increases the production complexity and cost.

[0005] Another enterprise uses micro-pore puncture to extract part of the coconut water, aiming to reduce the total amount of liquid in the cavity, thereby reducing the volume expansion stress during freezing. However, this not only causes the loss of coconut water nutrition and flavor, affecting product quality consistency, but also the liquid extraction process itself may introduce contamination; more importantly, even if some coconut water is reduced, if there is still a lot of free water on the surface of the coconut shell, a dense ice layer will still form during quick freezing, closing the natural germination hole, which actually hinders the slow release of internal residual gas and water vapor, and does not fundamentally solve the problem of shell cracking.

[0006] The above-mentioned physical intervention methods may alleviate the cracking phenomenon to some extent, but at the cost of sacrificing the integrity, safety or sensory quality of the product, which is difficult to meet the industrialized production needs of high-quality frozen coconut meat with shell.

[0007] In addition, the prior art generally ignores the key influence of coconut fruit age on processing adaptability. Overly tender coconut meat is not fully developed, with loose structure; overripe coconut meat is highly fibrous and has excessive internal pressure, both of which are not suitable for frozen processing. How to accurately select raw materials and synergistically regulate water state and freezing program has an important influence on improving the quality of frozen coconut meat with shell. SUMMARY

[0008] To solve the above problems, the first aspect of the present application provides a processing method of coconut meat, comprising the following steps:

[0009] Step S1, fruit age selection and incubation: after picking the coconut fruit, incubate it in the dark; the fruit age is from March to May;

[0010] Step S2, peeling and surface treatment: remove the exocarp and mesocarp of the coconut fruit, and then perform surface polishing treatment to obtain coconut meat with shell I; the coconut meat with shell I is wrapped by endocarp on the outside, and contains coconut meat on the inside of the endocarp, and the inner cavity of the coconut meat contains coconut water; the top of the coconut meat with shell I retains a protective conical shell cover to protect the natural pores on the endocarp;

[0011] Step S3, antioxidant and antibacterial treatment: immerse the coconut meat with shell I in solution A for antioxidant and antibacterial treatment to obtain coconut meat with shell II; the mass concentration of ascorbic acid in the solution A is 0.5% to 1%, and the mass concentration of citric acid is 0.1% to 0.3%;

[0012] Step S4, surface drying to remove free water of endocarp: place the coconut meat with shell II in a drying machine for surface drying to remove free water of the endocarp, and obtain coconut meat with shell III; the moisture content of the endocarp of the coconut meat with shell III is 8% to 12% by mass fraction, and the appearance color is uniform peach brown;

[0013] Step S5, phased slow freezing: the coconut meat with shell III is subjected to first-stage slow cooling and second-stage slow freezing to obtain coconut meat with shell IV; the temperature of the first-stage slow cooling is 0℃ to 5℃, and the time is 2 days to 3 days; the temperature of the second-stage slow freezing is -5℃ to 0℃, and the time is 2 days to 3 days;

[0014] Step S6, vacuum packaging: use a packaging film to adhere and seal the coconut meat with shell IV to obtain coconut meat with shell V;

[0015] Step S7, immersion quick freezing: immerse the coconut meat with shell V in a refrigerant for quick freezing to obtain a finished product; the refrigerant is a mixture of anhydrous ethanol and dry ice;

[0016] Step S8, frozen storage: transfer the finished product to a frozen storage warehouse at -18℃ for storage.

[0017] The coconut with fruit age of 3 months to 5 months (fruit age is counted from the day of successful pollination) is selected as raw material. The coconut at this stage is in a good state in terms of food quality, physicochemical properties and processing adaptability, which is embodied in the following three aspects.

[0018] Firstly, the unique double-layered coconut meat structure provides good taste and freezing stability. The coconut meat of coconut with fruit age of 3 months to 5 months has formed a typical double-layered structure: the outer layer (close to the inner wall of the coconut shell) is a layer of extremely thin, soft and translucent gelatinous tissue, which is as tender as a milk jelly; the inner layer (located inside the gelatinous layer, close to the coconut water) is a layer of thick and crisp white solid coconut meat, the cell wall has not yet been fibrous. This structure of "outer gelatinous and inner crisp" not only brings a unique flavor experience of melting in the mouth and sweet and refreshing taste, but more importantly, its tender and low fibrous tissue has excellent resistance to freezing-thawing process. In contrast, the coconut meat of mature coconut is prone to become dry and hard after thawing due to high fibrosis; the tender coconut of 3 months to 5 months can maximize the retention of moisture and delicate texture, ensuring good taste of the final product.

[0019] Secondly, the coconut water composition reaches the ideal peak, with flavor, nutrition and process safety. At this fruit age stage, the sugar and electrolyte (such as potassium and sodium) content in the coconut water reaches a peak, not only with sweet flavor and high nutritional value, but also making it a natural isotonic drink. At the same time, although the coconut cavity is full of coconut water, the internal pressure has not reached the maximum value, providing a safe operating window for subsequent key processes such as "static pressure reduction" and "drying weight reduction". If overripe coconut is used, the overhigh internal pressure is prone to cause coconut shell cracking during freezing, resulting in processing failure.

[0020] Finally, the coconut shell has appropriate physical properties, balancing strength and toughness. The coconut shell of 3 months to 5 months has sufficient hardness to withstand mechanical treatment such as peeling and polishing, effectively protecting the internal coconut meat and coconut water; at the same time, its hardness has not reached the extreme of the aging stage, still retaining a certain toughness, which can buffer the slight volume expansion caused by the freezing of internal water, thereby significantly reducing the risk of shell cracking during rapid freezing.

[0021] The purpose of incubation is to slow down the physiological activity inside the coconut and naturally release part of the internal pressure, thereby reducing the risk of coconut shell cracking caused by increased internal pressure during subsequent freezing process.

[0022] As a preferred technical solution, the incubation temperature in step S1 is 25℃ to 30℃, and the incubation time is 2 days to 3 days.

[0023] As a preferred technical solution, the antioxidant and antibacterial treatment time in step S3 is 1 minute to 2 minutes.

[0024] Preferably, the surface drying environment in step S4 has a humidity of 30-40% and a temperature of 25-30°C for 70-80 hours.

[0025] Preferably, the packaging film in step S6 has a thickness of 100 microns and is made of nylon.

[0026] Preferably, the quick freezing in step S7 is performed for 40-50 minutes at a temperature of -60 to -70°C with a mass ratio of dry ice to ethanol of about (3-4):1.

[0027] In a second aspect, the present application provides a husked coconut meat prepared by the processing method of the first aspect.

[0028] In a third aspect, the present application provides a method for reducing the surface crack rate of coconut shells, which uses the processing method of the first aspect to prepare husked coconut meat.

[0029] The present application significantly reduces the surface crack rate of frozen husked coconut meat by removing free water from the endocarp (coconut shell) through surface drying and slow freezing in stages, while effectively improving the flavor of coconut meat and coconut water. DETAILED DESCRIPTION

[0030] To make the above-mentioned objectives, features and advantages of the present application more obvious and easy to understand, the applicant describes and analyzes specific comparative examples and examples.

[0031] Example 1

[0032] Step S1, fruit age selection and incubation: after picking the coconut fruit, incubate it in the dark; the incubation temperature is 25°C, and the incubation time is 2 days; the coconut fruit is 3 months old and has two layers of coconut meat inside;

[0033] Step S2, peeling and surface treatment: remove the exocarp and mesocarp of the coconut fruit, and then perform surface polishing treatment to obtain husked coconut meat I; the husked coconut meat I is wrapped with an endocarp on the outside, and contains coconut meat on the inside of the endocarp, and coconut water in the inner cavity of the coconut meat; a protective conical cap is retained on the top of the husked coconut meat I to protect the natural pores on the endocarp;

[0034] Step S3, antioxidant and antibacterial treatment: immerse the husked coconut meat I in solution A for antioxidant and antibacterial treatment to obtain husked coconut meat II; the mass concentration of ascorbic acid in the solution A is 0.5%, and the mass concentration of citric acid is 0.1%; the treatment time is 1 minute;

[0035] Step S4, surface drying to remove free water of endocarp: the shelled coconut meat II is put into a drying machine for surface drying to remove free water of endocarp, to obtain shelled coconut meat III; the moisture content of the endocarp of the shelled coconut meat III is 8% by mass fraction, and the appearance color is uniform peach brown; the surface drying is performed at an environmental humidity of 30% and a temperature of 25℃ for 70 hours;

[0036] Step S5, phase freezing: the shelled coconut meat III is subjected to first-stage slow cooling and second-stage slow freezing, to obtain shelled coconut meat IV; the first-stage slow cooling is performed at a temperature of 0℃ for 2 days; the second-stage slow freezing is performed at a temperature of -5℃ for 2 days;

[0037] Step S6, vacuum packaging: the shelled coconut meat IV is sealed by using a packaging film, to obtain shelled coconut meat V; the packaging film has a thickness of 100 microns and is made of nylon;

[0038] Step S7, immersion quick freezing: the shelled coconut meat V is immersed in a refrigerant for quick freezing, to obtain a finished product; the refrigerant is a mixture of anhydrous ethanol and dry ice; the quick freezing is performed for 40 minutes at a temperature of -60℃; the mass ratio of dry ice to ethanol is about 3:1;

[0039] Step S8, frozen storage: the finished product is transferred to a frozen storage at -18℃ for storage.

[0040] Example 2

[0041] Step S1, fruit age selection and incubation: the coconut fruit is picked and incubated in the dark; the incubation is performed at a temperature of 28℃ for 2.5 days; the coconut fruit is 4 months old and has two layers of coconut meat inside;

[0042] Step S2, peeling and surface treatment: the outer and middle pericarps of the coconut fruit are removed, and then the shelled coconut meat I is obtained by surface polishing treatment; the shelled coconut meat I is wrapped by an endocarp on the outside, and contains coconut meat inside the endocarp, and the coconut meat contains coconut water in the inner cavity; a protective conical cap is reserved on the top of the shelled coconut meat I to protect the natural holes on the endocarp;

[0043] Step S3, antioxidant and bacteriostatic treatment: the shelled coconut meat I is immersed in solution A for antioxidant and bacteriostatic treatment, to obtain shelled coconut meat II; the mass concentration of ascorbic acid in the solution A is 0.6%, and the mass concentration of citric acid is 0.2%; the treatment is performed for 2 minutes;

[0044] Step S4, surface drying to remove free water of endocarp: the shelled coconut meat II is put into a drying machine for surface drying to remove free water of endocarp, to obtain shelled coconut meat III; the moisture content of the endocarp of the shelled coconut meat III is 8% by mass fraction, and the appearance color is uniform peach brown; the surface drying is performed at an environmental humidity of 30% and a temperature of 25℃ for 70 hours;

[0045] Step S5, phased slow freezing: the shelled coconut meat III is subjected to first-stage slow cooling and second-stage slow freezing to obtain shelled coconut meat IV; the first-stage slow cooling is performed at a temperature of 2°C for 2.5 days; the second-stage slow freezing is performed at a temperature of -2°C for 2.5 days;

[0046] Step S6, vacuum packaging: the shelled coconut meat IV is sealed with a packaging film to obtain shelled coconut meat V; the packaging film has a thickness of 100 microns and is made of nylon;

[0047] Step S7, immersion quick freezing: the shelled coconut meat V is immersed in a refrigerant for quick freezing to obtain a finished product; the refrigerant is a mixture of anhydrous ethanol and dry ice; the quick freezing time is 45 minutes; the temperature is -65°C; the mass ratio of dry ice to ethanol is about 3.5:1;

[0048] Step S8, frozen storage: the finished product is transferred to a frozen storage room at -18°C for storage.

[0049] Example 3

[0050] Step S1, fruit age selection and incubation: the coconut fruit is picked and incubated in the dark; the incubation temperature is 30°C, and the incubation time is 3 days; the coconut fruit is 5 months old and has two layers of coconut meat inside;

[0051] Step S2, peeling and surface treatment: the outer and middle fruit skins of the coconut fruit are removed, and then the shelled coconut meat I is obtained by surface polishing treatment; the shelled coconut meat I is wrapped by the inner fruit skin on the outside, and the inner side of the inner fruit skin contains coconut meat, and the coconut water is contained in the inner cavity of the coconut meat; a protective conical cap is reserved on the top of the shelled coconut meat I to protect the natural hole on the inner fruit skin;

[0052] Step S3, antioxidant and antibacterial treatment: the shelled coconut meat I is immersed in solution A for antioxidant and antibacterial treatment to obtain shelled coconut meat II; the mass concentration of ascorbic acid in the solution A is 1%, and the mass concentration of citric acid is 0.3%; the treatment time is 2 minutes;

[0053] Step S4, surface drying to remove free water of the inner fruit skin: the shelled coconut meat II is placed in a drying machine for surface drying to remove the free water of the inner fruit skin, and the shelled coconut meat III is obtained; the moisture content of the inner fruit skin of the shelled coconut meat III is 12% by mass fraction, and the appearance color is uniform peach brown; the surface drying is performed at an environmental humidity of 40% and a temperature of 30°C for 80 hours;

[0054] Step S5, phased slow freezing: the shelled coconut meat III is subjected to first-stage slow cooling and second-stage slow freezing to obtain shelled coconut meat IV; the first-stage slow cooling is performed at a temperature of 5°C for 3 days; the second-stage slow freezing is performed at a temperature of 0°C for 3 days;

[0055] Step S6, vacuum packaging: using a packaging film to adhere and seal the shelled coconut meat IV to obtain shelled coconut meat V; the packaging film has a thickness of 100 microns and is made of nylon;

[0056] Step S7, immersion quick freezing: immersing the shelled coconut meat V in a refrigerant for quick freezing to obtain a finished product; the refrigerant is a mixture of anhydrous ethanol and dry ice; the quick freezing time is 50 minutes; the temperature is -70°C; the mass ratio of dry ice to anhydrous ethanol is about 4:1;

[0057] Step S8, frozen storage: transferring the finished product to a frozen storage at -18°C for storage.

[0058] Comparative Example 1

[0059] Step S4, i.e., "surface drying to remove free water of endocarp", is not performed, and the other steps and parameters are consistent with Example 1.

[0060] Comparative Example 2

[0061] Step S5, i.e., "staged slow freezing", is not performed, and the other steps and parameters are consistent with Example 1.

[0062] The surface cracking of the finished products of Example 1 and Comparative Example 1 is counted, and the proportion of the finished products with surface cracks in the total finished products, i.e., the surface cracking rate, is calculated.

[0063] The statistical results are shown in the following table. By surface drying to remove the free water of the endocarp (coconut shell), the surface cracking rate of the shelled coconut meat during freezing can be significantly reduced. When the shelled coconut meat is frozen, the water in the humid coconut shell freezes first to form a hard ice shell, and the coconut water inside the coconut shell freezes slowly. During the freezing process, the volume of the coconut water expands, and the expansion stress is transmitted to the frozen coconut shell. Due to the high water content, the frozen coconut shell has physical rigidity and brittleness, and the tensile strength is low. The rigidity of the frozen coconut shell prevents the elastic deformation of the coconut shell, resulting in cracks on the surface of the coconut shell.

[0064] In addition, during the freezing process, the crystallization of water in the coconut shell produces an outward expansion force. The microporous structure of the dried coconut shell allows part of the water vapor to penetrate, which can buffer the expansion force and reduce the surface cracking rate. The surface ice shell completely blocks the pressure release channel and hinders the escape path of the internal water expansion, forming a pressure cooker effect, which causes cracks on the surface of the coconut shell.

[0065] Surface drying not only moderately reduces the water content of the coconut shell, but also creates a mild and continuous maturation environment for the inside of the coconut. During this process, the reducing sugars, amino acids and phenolic substances in the coconut water undergo slow oxidation under natural micro-oxygen conditions, react with Maillard precursors, and the slight evaporation of water increases the concentration of the reactants, thereby effectively improving the flavor of the coconut water.

[0066] The goal of the staged slow freezing is to partially freeze the coconut water inside the coconut shell into a slushy state (partial solidification) and slowly reduce the core temperature of the coconut to a range of -0.1°C to -3°C. This slow pre-cooling process is the key to achieving complete freezing without cracking, as it gives the water inside the coconut enough time to form fine ice crystals instead of large stresses under rapid freezing.

[0067] The staged slow freezing can reduce the surface crack rate. Water expands by about 9% in volume during the phase transition from liquid to solid ice. If frozen too quickly, it is easy to cause rapid nucleation and growth of ice crystals locally due to instantaneous phase change, resulting in concentrated stress and pressure peaks, exceeding the bearing limit of the coconut shell and causing cracking. By using a multi-stage, extremely slow cooling method, especially by extending the residence time when crossing the critical freezing point interval of 0°C to -5°C, the ice crystal nucleation and growth rate can be significantly reduced, and the phase transition process can be carried out smoothly. At the same time, the water has enough time to migrate outward or distribute uniformly in the tissue, so that the internal expansion pressure can be gradually released, avoiding local stress accumulation, and ultimately effectively preventing the cracking of the coconut shell.

[0068] Table 1: Surface crack rate statistics

[0069]

[0070] Step S7 uses a mixture of anhydrous ethanol and dry ice as a coolant to immerse the shelled coconut at -60°C to -70°C for 40-50 minutes. This temperature is much lower than the eutectic point of water, which can achieve rapid "glassy freezing" and form fine ice crystals, effectively protecting the cell structure and gel texture of the double-layer coconut meat. At the same time, ethanol as a high thermal conductivity liquid medium, compared with liquid nitrogen cooling is more uniform and controllable, not only can efficiently transfer heat to ensure the effect of quick freezing, but also avoid the cracking of coconut shell caused by thermal stress due to large temperature difference, which can meet the technical requirements of high-end food ultra-low temperature quick freezing.

Claims

1. A method for processing coconut meat, characterized in that, Includes the following steps: Step S1, Fruit Age Selection and Incubation: After harvesting the coconuts, incubate them in the dark; the coconuts should be 3 to 5 months old. Step S2, Peeling and Surface Treatment: Remove the outer and middle pericarps of the coconut fruit, and then polish the surface to obtain coconut meat in shell I; the outer part of the coconut meat in shell I is wrapped by the inner pericarp, the inner side of the inner pericarp contains coconut meat, and the inner cavity of the coconut meat contains coconut water; the top of the coconut meat in shell I retains a protective conical shell cap to protect the natural pores on the inner pericarp; Step S3, Antioxidant and Antibacterial Treatment: Immerse coconut meat I in shell in solution A for antioxidant and antibacterial treatment to obtain coconut meat II in shell; the mass concentration of ascorbic acid in solution A is 0.5% to 1%, and the mass concentration of citric acid is 0.1% to 0.3%. Step S4, surface drying to remove free water from the inner pericarp: Place the coconut meat II in a dryer for surface drying to remove free water from the inner pericarp, and obtain coconut meat III in the shell; the wet basis moisture content of the inner pericarp of the coconut meat III in the shell is 8% to 12% by mass, and the appearance color is uniform peach brown. Step S5, staged slow freezing: Coconut meat in shell III undergoes a first stage of slow cooling and a second stage of slow freezing to obtain coconut meat in shell IV; the temperature of the first stage of slow cooling is 0℃~5℃, and the time is 2 to 3 days; the temperature of the second stage of slow freezing is -5℃~0℃, and the time is 2 to 3 days; Step S6, vacuum packaging: use packaging film to seal and seal the coconut meat in shell IV to obtain coconut meat in shell V; Step S7, Immersion quick-freezing: Immerse the coconut meat in its shell V in a refrigerant for quick-freezing to obtain the finished product; the refrigerant is a mixture of anhydrous ethanol and dry ice; Step S8, frozen storage: Transfer the finished product to a frozen storage room at -18°C for storage.

2. The processing method according to claim 1, characterized in that, The incubation temperature in step S1 is 25℃~30℃, and the incubation time is 2 days~3 days.

3. The processing method according to claim 2, characterized in that, The antioxidant and antibacterial treatment time in step S3 is 1 to 2 minutes.

4. The processing method according to claim 3, characterized in that, In step S4, the ambient humidity for surface drying is 30%–40%, the temperature is 25°C–30°C, and the time is 70–80 hours.

5. The processing method according to claim 4, characterized in that, The quick-freezing time in step S7 is 40 to 50 minutes; the temperature is -60°C to -70°C; and the mass ratio of dry ice to ethanol is approximately (3 to 4):

1.

6. A type of coconut meat with shell, characterized in that, The coconut meat in its shell is produced by the processing method described in claim 1.

7. A method for reducing the surface crack rate of coconut shells, characterized in that, The method described herein employs the processing method as described in claim 1.

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