Steady-state regulation and control method for anthocyanin in freshly squeezed fruit juice and freshly squeezed fruit juice

Abstract

The invention belongs to the field of food, and discloses a steady-state regulation and control method for anthocyanin in freshly squeezed fruit juice, which is characterized in that litchi pomace extract is added into the freshly squeezed fruit juice to improve the retention rate of total anthocyanin in the freshly squeezed fruit juice in the storage process. According to the method, the litchi pomace extract is used for inhibiting anthocyanin degradation, and the total degradation rate of anthocyanin is lower than 10% within 3 months. Meanwhile, the invention further discloses the freshly squeezed fruit juice obtained based on the method.

Description

Technical Field

[0001] This invention relates to the food industry, and more particularly to a method for stabilizing and regulating anthocyanins in freshly squeezed juice, and freshly squeezed juice. Background Technology

[0002] Freshly squeezed juice is highly favored by consumers because it retains the natural nutrients and fresh flavor of the fruits and vegetables. Fruits such as blueberries, mulberries, and bayberries are rich in anthocyanins, which, after juicing, not only give the juice its vibrant color but also possess physiological activities such as antioxidant properties, eye protection, and immune system enhancement. However, the degradation of anthocyanins in freshly squeezed juice is a key issue limiting the product's shelf life. This degradation is affected by factors such as light, temperature, pH, vitamin C, and oxidases. Vitamin C, a common nutrient in fruits, often co-occurs with anthocyanins in freshly squeezed juice. Their interaction can accelerate anthocyanin degradation, thus affecting the juice's color and reducing product quality.

[0003] In existing technologies, the protection of anthocyanins in fruit juice often involves adding chemical reagents, organic acids, phenolic acids, and amino acids to mitigate anthocyanin degradation. For example, patent application number 202210675668.0 invented a composite color-protecting agent for honeysuckle berry juice, using a combination of chemical components and extracts for protection: glutathione, D-galacturonic acid, diethylenetriaminepentaacetic acid, spearmint extract, tannic acid, and ascorbic acid. Patent application number 202211418828.X uses the addition of mannoprotein. Patent application number 201811390511.3 uses the addition of malic acid and citric acid, as well as one or more of malonic acid, cysteine, and ferulic acid to increase the stability of strawberry anthocyanins. Publication number US8449927B2, a patent application concerning a stable anthocyanin composition, uses glutathione and blueberry fruit extract to inhibit anthocyanin degradation. The patent application with publication number CN118872781A, which discloses a method and application for stabilizing anthocyanins in grape juice beverages, discloses that mannose protein inhibits the degradation of anthocyanins in grape juice beverages.

[0004] Based on the literature search results, the commonly used methods are to inhibit anthocyanin degradation using organic acids, phenolic acids, or amino acids. Most solutions involving plant extracts require the simultaneous addition of other amino acids.

[0005] The degradation mechanisms of anthocyanins in fruit juice can be broadly classified into: non-enzymatic degradation mechanisms (hydrolysis and ring-opening degradation, oxidative degradation, and thermal degradation) and enzymatic degradation mechanisms (glycoside hydrolases, oxidases, and intestinal flora degradation). The degradation inhibition mechanism involving phenolic acids, organic acids, and amino acids addresses the issue from a comprehensive perspective, considering both of the above-mentioned mechanisms. Phenolic acids and amino acids, acting as co-colorants, form relatively stable complexes with the 2-phenylbenzopyran cation of anthocyanins through non-covalent interactions (such as hydrogen bonding and hydrophobic interactions), thereby preventing hydration degradation; they also scavenge reactive oxygen species, blocking the oxidative degradation chain; simultaneously, some phenolic acids can bind to the active site of polyphenol oxidase (PPO), inhibiting enzymatic oxidation reactions and reducing the indirect degradation of anthocyanins by oxidation products such as ortho-quinones. Overall, the stability of anthocyanins in fruit juice systems remains a challenge. Although phenolic acids, organic acids, and amino acids can inhibit anthocyanin degradation to some extent, their effects are limited.

[0006] In studies on the role of plant extracts in inhibiting anthocyanin degradation, few studies have disclosed that a single plant extract can achieve the aforementioned effects, nor have any studies revealed the possible underlying mechanisms. Summary of the Invention

[0007] The purpose of this invention is to provide a method for regulating the stabilization of anthocyanins in freshly squeezed juice. This method uses litchi pomace extract to inhibit anthocyanin degradation, and the total degradation rate of anthocyanins is less than 10% after 3 months.

[0008] In addition, the present invention also discloses freshly squeezed juice obtained based on this method.

[0009] To achieve the above objectives, this application discloses: A method for stabilizing and regulating anthocyanins in freshly squeezed juice involves adding lychee fermented pomace extract to freshly squeezed juice to improve the retention rate of total anthocyanins in the juice during storage.

[0010] We speculate that the possible mechanism by which lychee fermented pomace extract inhibits anthocyanin degradation is that when yeast ferments lychee pomace, it alters the structure of polyphenols, polysaccharides, and proteins in the pomace. These products work together to encapsulate anthocyanins through non-covalent binding. Furthermore, in a preferred embodiment of the present invention, the freshly squeezed juice is treated with an inert atmosphere protection, which further inhibits anthocyanin degradation in a nitrogen or carbon dioxide environment.

[0011] In the above-mentioned steady-state regulation method, 0.5~1wt% of litchi pomace extract is added to the freshly squeezed juice.

[0012] In the above-mentioned steady-state regulation method, the litchi pomace extract is the extract obtained after yeast fermentation and desugaring of litchi pulp pomace.

[0013] In the above-mentioned steady-state regulation method, the fermentation strain used in the litchi pomace extract is one of Angel Yeast or French wine yeast.

[0014] In the above-mentioned steady-state regulation method, the fermentation strain used in the litchi pomace extract is Saccharomyces cerevisiae. The preparation method of the litchi pomace extract is as follows: litchi pulp pomace is inoculated with activated fermentation bacteria solution; the fermentation bacteria solution is equivalent to 0.1~0.2% of the weight of litchi pulp pomace; fermentation is carried out at 30℃ for 24~36 h, during which the reducing sugar content is monitored periodically, and fermentation is terminated when the reducing sugar content is ≤3%, and the fermentation product is obtained; the fermentation product is mixed with water and filtered to obtain the supernatant; the supernatant is precipitated with ethanol and the precipitate is collected; the precipitate is the litchi pomace extract. In the above-mentioned steady-state regulation method, after adding lychee pomace extract to the freshly squeezed juice, the pH value is adjusted to 3.2~4.2; the pH adjuster used to adjust the pH value is an acidic juice; the acidic juice is lemon juice and / or mandarin orange juice.

[0015] In the above-mentioned steady-state regulation method, the preparation method of the freshly squeezed juice is as follows: the anthocyanin-containing fruit is pre-cooled to 5~10℃ and then juiced using a juicer; the juicing temperature is controlled below 10℃; the atmosphere inside the juicer is a low-oxygen or inert atmosphere; the low-oxygen or inert atmosphere refers to an atmosphere with an oxygen content of less than 2 vol.

[0016] In the above-mentioned steady-state regulation method, the fruit used to prepare the freshly squeezed juice is one or more of mulberry, blueberry, and bayberry.

[0017] Meanwhile, the present invention also discloses a freshly squeezed juice, which is prepared by any of the methods described above.

[0018] Finally, this invention also discloses the use of litchi pomace extract to inhibit anthocyanin degradation in freshly squeezed juice.

[0019] This application has at least the following beneficial effects: This invention addresses the core problem of rapid anthocyanin degradation caused by the coexistence of anthocyanins and vitamin C in freshly squeezed juice. For the first time, it applies the water extract of lychee pomace after yeast fermentation and desugaring to the juice system, which can significantly reduce the degradation rate of anthocyanins.

[0020] In a further preferred embodiment of the present invention, low-temperature, low-oxygen juicing and pH optimization are synergistically applied to the juice system, achieving an anthocyanin retention rate of ≥90% and a color difference ΔE value ≤1.0 after 3 months of refrigeration at 4°C, with no obvious browning or off-flavors. Furthermore, the present invention is applicable to juices processed by both heat sterilization and ultra-high pressure processing, with simple process steps, requiring no large-scale equipment investment, and suitable for industrial-scale promotion. Detailed Implementation

[0021] The present invention will now be clearly and completely described in conjunction with embodiments thereof. It should be noted that, unless otherwise specified in the embodiments, conditions are performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products. Unless otherwise specified, all parts used in the embodiments of the present invention are parts by weight.

[0022] Unless otherwise specified, all raw materials and reagents used in this invention are from the conventional market.

[0023] Part 1: Preparation of the Extract I. Preparation method of litchi pomace extract 1: Preparatory work: Preparation of extracts from fermented and unfermented lychee pomace Yeast inoculation: Take 10 kg of fresh lychee pulp residue (juice by-product), pasteurize it, and then inoculate it with activated Angel brewer's yeast (RV002). The inoculation amount is 0.2% of the raw material mass. Fermentation and sugar removal: Ferment at 30℃ for 24 h, during which the reducing sugar content is monitored regularly. Fermentation is terminated when the reducing sugar content is ≤3%. Extraction: Fermented or unfermented litchi pomace was mixed with water at a ratio of 3:1, pressed and filtered (using a 200-mesh filter) to obtain the supernatant. The supernatant was mixed with 4 times its volume of 95% ethanol, allowed to stand overnight at room temperature, centrifuged, and the precipitate was dried to obtain the litchi pomace extract. The main components of the fermented pomace were dietary fiber and polysaccharides, with a total phenol content of approximately 6 mg / kg and a total protein content of approximately 3%. The unfermented pomace extract was used as a control example.

[0024] II. Preparation method of litchi pomace extract 2: Preparatory work: Preparation of lychee fermentation pomace Yeast inoculation: Take 10 kg of fresh lychee pulp residue (juice by-product), pasteurize it, and then inoculate it with activated Angel brewer's yeast (RV002). The inoculation amount is 0.1% of the raw material mass. Fermentation and sugar removal: Ferment at 30℃ for 36 h, during which the reducing sugar content is monitored regularly. Fermentation is terminated when the reducing sugar content is ≤3%. Extraction: Fermented lychee pomace was mixed with water at a ratio of 3:1, pressed and filtered (using a 200-mesh filter) to obtain the supernatant. The supernatant was mixed with 4 times its volume of 95% ethanol, allowed to stand overnight at room temperature, centrifuged, and the precipitate was dried to obtain the lychee pomace extract. The main components of the fermented pomace were dietary fiber and polysaccharides, with a total phenol content of approximately 6.1 mg / kg and a total protein content of approximately 2.8%.

[0025] III. Lemon pomace extract Preparation: Lemon pulp Yeast inoculation: Take 10 kg of fresh lemon pomace (juice extraction by-product), pasteurize it, and then inoculate it with activated Angel brewing yeast (RV002). The inoculation amount is 0.2% of the raw material mass. Fermentation and sugar removal: Ferment at 30℃ for 24 h, during which the reducing sugar content is monitored regularly. Fermentation is terminated when the reducing sugar content is ≤3%. Extraction: Mix fermented or unfermented lemon pomace with water at a ratio of 3:1, press and filter (using a 200-mesh filter) to obtain the supernatant. Mix the supernatant with 4 times its volume of 95% ethanol, let stand overnight at room temperature, centrifuge, and dry the precipitate to obtain lemon pomace extract. The main components of fermented pomace are dietary fiber and polysaccharides, with a total phenol content of approximately 105 mg / kg and a total protein content of approximately 2.5%.

[0026] IV. Olive pomace extract Preparation: Olive pomace Yeast inoculation: Take 10 kg of fresh olive pomace, pasteurize it, and then inoculate it with activated Angel brewer's yeast (RV002). The inoculation amount is 0.2% of the raw material mass; ferment at 30℃ for 24 h. Extraction: Mix fermented or unfermented olive pomace with water in a 3:1 ratio, press and filter (using a 200-mesh filter) to obtain the supernatant. Mix the supernatant with 4 times its volume of 95% ethanol, let stand overnight at room temperature, centrifuge, and dry the precipitate to obtain the olive pomace extract.

[0027] Part Two: Preparation of Mulberry Juice 1) Raw material pretreatment: Take 5kg of fresh mulberries, remove rotten fruit, wash with clean water and soak in 8℃ purified water for 3-5 minutes; 2) Low-oxygen juicing: The pre-cooled mulberries are put into a closed juicer, and nitrogen is introduced at a flow rate of 1L / min to replace the air in the machine until the oxygen concentration in the chamber is ≤2vol%; the juice is extracted at a temperature below 10℃, and nitrogen is continuously introduced (flow rate 0.8L / min) during the juicing process to maintain a low-oxygen environment, so as to obtain freshly squeezed mulberry juice. 3) Extract adjustment: Add the extract from the first part above to the mulberry juice at a rate of 0.7% of the juice mass and mix well; 4) Microenvironment optimization: Adjust the pH of the juice to 3.0 with lemon juice, sterilize under ultra-high pressure to obtain mulberry juice, and refrigerate the mulberry juice at 4℃.

[0028] Testing items: The above mulberry juice was refrigerated at 4℃ for 3 months, and the total anthocyanin retention rate, color difference before and after storage, and sensory evaluation after storage were tested.

[0029] In addition, a blank group is set up in this section. No extract is added to the blank group, and the remaining steps are the same as those described above.

[0030] Total anthocyanin retention rate = Total anthocyanin content after storage * 100 / Total anthocyanin content before storage Detection methods: Total anthocyanins, color difference and sensory properties in the samples were detected by spectrophotometry, color difference method and sensory profile analysis.

[0031] The test results are shown in Table 1. Table 1. Detection results of mulberry juice sample Total anthocyanin retention rate ΔE value Sensory evaluation Control group (stored at 4℃ for 3 months) 60.2% 2.51 It shows obvious browning but has no odor. Lychee fermented pomace extract 1 (store at 4℃ for 3 months) 91.7% 0.32 It exhibits no browning or off-odors and has the flavor of fresh mulberries. Lychee fermented pomace extract 2 (store at 4℃ for 3 months) 90.4% 0.41 It exhibits no browning or off-odors and has the flavor of fresh mulberries. Lemon fermented pomace extract (store at 4℃ for 3 months) 70.3% 1.93 It shows obvious browning but has no odor. Olive fermented pomace extract (stored at 4℃ for 3 months) 65.6% 2.37 It shows obvious browning but has no odor.

[0032] Results Analysis: As shown in the table above, the total anthocyanin content of the mulberry juice in the control group decreased the most and the retention rate was the lowest after 3 months of storage at 4℃, with significant browning of the product. The addition of lychee fermented pomace extract greatly inhibited the decrease in anthocyanins. After adding lemon fermented pomace extract and olive fermented pomace extract, the anthocyanin retention rate of mulberry juice increased, but it was significantly lower than that of lychee fermented pomace extract.

[0033] Part Three: Preparation of Blueberry Juice 1) Raw material pretreatment: Take 5kg of fresh blueberries, remove rotten fruit, wash with clean water and soak in 5℃ purified water for 3-5 minutes; 2) Low-oxygen juicing: The pre-cooled bayberries are sent into a closed pulper, and carbon dioxide is introduced at a flow rate of 1.5L / min to replace the air in the machine until the oxygen concentration in the chamber is ≤2%; the pulping is carried out at a temperature below 10℃, and carbon dioxide is continuously introduced (flow rate 0.8L / min) during the pulping process to maintain a low-oxygen environment, so as to obtain freshly squeezed blueberry pulp. 3) Extract adjustment: Add the above-mentioned extract to the blueberry pulp at a rate of 1% of the juice mass, and mix well; 4) Microenvironment optimization: Adjust the pH of the juice to 3.5 with small green mandarin orange juice, pasteurize to obtain blueberry juice, and then refrigerate at 4°C.

[0034] Test items: The above blueberry juice was refrigerated at 4℃ for 3 months, and the total anthocyanin retention rate, color difference before and after storage, and sensory evaluation after storage were tested.

[0035] In addition, a blank group is set up in this section. No extract is added to the blank group, and the remaining steps are the same as those described above.

[0036] Total anthocyanin retention rate = Total anthocyanin content after storage * 100 / Total anthocyanin content before storage Detection methods: Total anthocyanins, color difference and sensory properties in the samples were detected by spectrophotometry, color difference method and sensory profile analysis.

[0037] The test results are shown in Table 2. Table 2. Detection results of blueberry juice sample Total anthocyanin retention rate ΔE value Sensory evaluation Blank group 58.5% 2.36 It shows obvious browning but has no odor. Lychee pomace extract 1 91.3% 0.31 Bright color without browning, and odorless. Lychee pomace extract 2 90.2% 0.38 Bright color without browning, and odorless. Lemon pomace extract 75.1% 1.46 Slight browning, no odor. Olive pomace extract 70.7% 1.75 Slight browning, no odor.

[0038] Results Analysis: As shown in the table above, the blueberry juice in the control group experienced the largest decrease in total anthocyanins and the lowest retention rate after storage at 4℃ for 3 months. The product showed significant browning, losing its bright red color and turning a dull, earthy yellow. Adding lychee fermented pomace extract significantly inhibited the decrease in anthocyanins in blueberry juice, resulting in a brighter juice color. While the addition of lemon and olive fermented pomace extracts increased the anthocyanin retention rate, it was significantly lower than that of lychee fermented pomace extract, and the juice color remained darker.

[0039] Part Four: Study on the Influence of Various Processing Parameters on the Performance of Mulberry Juice

[0040] Example 1

[0041] 1) Raw material pretreatment: Take 5kg of fresh mulberries, remove rotten fruit, wash with clean water and soak in 8℃ purified water for 3-5 minutes; 2) Low-oxygen juicing: The pre-cooled mulberries are put into a closed juicer and nitrogen is introduced at a flow rate of 1L / min to replace the air in the machine until the oxygen concentration in the chamber is ≤2%; the juice is extracted at a temperature below 10℃, and nitrogen is continuously introduced (flow rate 0.8L / min) during the juicing process to maintain a low-oxygen environment, so as to obtain freshly squeezed mulberry juice. 3) Extract adjustment: Add the above-mentioned lychee pomace extract 1 to the mulberry juice at an amount of 0.7% of the juice mass and mix well; 4) Microenvironment optimization: Adjust the pH of the juice to 3.0 with lemon juice, sterilize under ultra-high pressure to obtain mulberry juice, and refrigerate the mulberry juice at 4℃.

[0042] Comparison Example 1: No low-temperature precooling was performed. Except for step 1), which is "juicing directly without pre-cooling", all other parameters are exactly the same as in Example 1.

[0043] Compare with Example 2: Aerobic juicing (without gas protection) Except for step 2), "juicing in a natural air environment without nitrogen", the other parameters are the same as in Example 1. Comparative Example 3: No lychee pomace extract added. Except for step 3), which did not include lychee pomace extract, the other parameters were the same as in Example 1.

[0044] Control Example 4: pH not adjusted Except for step 4), where the pH was not adjusted, the other parameters were the same as in Example 1.

[0045] Comparative Example 5: Addition of unfermented lychee pomace extract Except for step 3), when adding unfermented litchi pomace extract (refer to the preparation method of litchi pomace extract 1), the other parameters are the same as in Example 1.

[0046] Compare with Example 6 (blank group) 1) Raw material pretreatment: Take 5kg of fresh mulberries, remove rotten fruit, wash with clean water and soak in room temperature purified water for 3-5 minutes; 2) Juicing: The mulberries are put into a closed juicer to extract juice, resulting in freshly squeezed mulberry juice; 3) Bottle, sterilize under ultra-high pressure, and refrigerate at 4°C.

[0047] Juice samples from the above examples and comparative examples were analyzed using spectrophotometry, colorimetry, and sensory profile analysis. The results are shown in Table 3 below. Table 3 Comparison of Juice Quality sample Total anthocyanin retention rate ΔE value Sensory evaluation Example 1 (stored at 4°C for 3 months) 92.8% 0.3 It exhibits no browning or off-odors and has the flavor of fresh mulberries. Comparative Example 1 (stored at 4℃ for 3 months) 80.6% 1.05 Slight browning, no odor Comparative Example 2 (stored at 4℃ for 3 months) 67.9% 2.33 Obvious browning, no odor Comparative Example 3 (stored at 4℃ for 3 months) 60.4% 2.56 It shows obvious browning but has no odor. Comparative Example 4 (stored at 4℃ for 3 months) 81.2% 1.35 Slight browning, no odor. Comparative Example 5 (stored at 4℃ for 3 months) 70.6% 1.83 Slight browning, no odor. Comparative Example 6 (stored at 4℃ for 3 months) 10.2% 3.01 Severe browning, no odor.

[0048] As shown in the table above, the low-temperature, low-oxygen pulping / juicing method used in this specific implementation case, along with the addition of lychee pomace extract and acidic fruit juice to adjust the pH value, effectively preserves the anthocyanins and color of mulberry juice and blueberry pulp after storage at 4℃ for 3 months. The total anthocyanin retention rate is over 90%, the color difference is minimal, and the aroma is well preserved. In contrast, the anthocyanin retention rate of mulberry juice in Control Examples 1-5 is only 60%-81.2%, and the color shows varying degrees of browning. According to Example 1 and Comparative Example 5, the color-preserving effect of fermented lychee pomace is significantly better than that of unfermented lychee pomace. In Control 4, the anthocyanin retention rate of mulberry juice is only 10.2%, and the browning is severe.

[0049] Therefore, this method has important reference value for the preservation of anthocyanins and sensory quality in fruit juice, and can significantly improve the retention rate of anthocyanins in fruit juice and reduce color changes.

[0050] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description; thus, all changes falling within the meaning and scope of the claims are intended to be included within the present invention.

Claims

1. A method for regulating the stabilization of anthocyanins in freshly squeezed juice, characterized in that, Lychee pomace extract was added to freshly squeezed juice to improve the retention rate of total anthocyanins in the juice during storage.

2. The steady-state control method according to claim 1, characterized in that, The freshly squeezed juice contains 0.5-1 wt% lychee pomace extract.

3. The steady-state control method according to claim 1, characterized in that, The litchi pomace extract is an extract obtained by yeast fermentation and desugaring of litchi pulp pomace.

4. The steady-state control method according to claim 3, characterized in that, The fermentation strain used in the lychee pomace extract is one of Angel Yeast or French wine yeast.

5. The steady-state control method according to claim 4, characterized in that, The preparation method of the litchi pomace extract is as follows: litchi pulp pomace is inoculated with activated fermentation bacteria solution; the fermentation bacteria solution is equivalent to 0.1~0.2% of the weight of litchi pulp pomace; fermentation is carried out at 30℃ for 24~36 h, during which the reducing sugar content is monitored periodically, and fermentation is terminated when the reducing sugar is ≤3%, and the fermentation product is obtained; the fermentation product is mixed with water and filtered to obtain the supernatant; the supernatant is precipitated with ethanol and the precipitate is collected; the precipitate is the litchi pomace extract.

6. The steady-state control method according to claim 1, characterized in that, After adding lychee pomace extract to the freshly squeezed juice, the pH value is adjusted to 3.2-4.2; the pH adjuster used to adjust the pH value is an acidic juice; the acidic juice is lemon juice and / or mandarin orange juice.

7. The steady-state control method according to claim 1, characterized in that, The method for preparing the freshly squeezed juice is as follows: the anthocyanin-containing fruit is pre-cooled to 5-10°C and then juiced using a juicer; the juicing temperature is controlled below 10°C; the atmosphere inside the juicer is a low-oxygen or inert atmosphere; the low-oxygen or inert atmosphere refers to an atmosphere with an oxygen content of less than 2 vol.

8. The steady-state control method according to claim 1, characterized in that, The fruits used to prepare the freshly squeezed juice are one or more combinations of mulberry, blueberry, and bayberry.

9. A freshly squeezed juice, characterized in that, It is prepared by the method described in any one of claims 1 to 8.

10. The use of litchi pomace extract to inhibit anthocyanin degradation in freshly squeezed juice.