A low glycemic index blueberry extract and its preparation method

Abstract

This invention provides a low glycemic index blueberry extract and its preparation method, belonging to the field of beverage processing technology. The preparation method includes the following steps: blueberries are pulped, then fermented using a compound strain of Lactobacillus acidophilus, Lactobacillus plantarum, and Bifidobacterium, filtered through a membrane filtration device to obtain a blueberry fermentation broth; blueberries are crushed, the pH of an ethanol solution is adjusted to 2-3 with citric acid, followed by ultrasonic extraction, centrifugation to collect the supernatant, and then vacuum distillation of the supernatant to obtain anthocyanin extract concentrate; the anthocyanin extract concentrate is freeze-dried to obtain anthocyanin extract dried product; the anthocyanin extract dried product and blueberry fermentation broth are mixed evenly at a mass-volume ratio of (0.2-0.3) g:1L, then maltitol is added to adjust acidity and sweetness, homogenized, filtered, and sterilized to obtain the blueberry extract. By using compound probiotic fermentation to reduce sugar content and combining it with alcohol extraction to enhance anthocyanins and improve efficacy, the resulting product has anthocyanin content ≥400 mg / L and a low GI.

Description

Technical Field

[0001] This invention relates to the field of beverage processing technology, and in particular to a low glycemic index blueberry extract and its preparation method. Background Technology

[0002] Blueberries are rich in anthocyanins, polyphenols, and other natural active ingredients, possessing excellent antioxidant, anti-inflammatory, and vision-protective physiological functions, making them an important raw material in the development of functional foods. Currently, most commercially available beverages using blueberries as the main ingredient employ traditional processes, adding large amounts of sugar to improve taste. This results in high sugar content and a high glycemic index, making them unsuitable for long-term consumption by people with blood sugar control.

[0003] To reduce the sugar content of blueberry drinks, existing technologies have employed methods that utilize probiotic fermentation to process blueberry raw materials. Microbial fermentation effectively utilizes and transforms the sugars in the raw materials, reducing the total sugar content of the product. However, relying solely on fermentation processes can easily lead to a decrease in the content of active ingredients in the product, thus diminishing its nutritional value.

[0004] On the other hand, anthocyanins can be extracted directly from blueberries to obtain high-purity active ingredients. However, such extracts often have a monotonous taste and are difficult to use directly as a flavorful beverage. Summary of the Invention

[0005] Based on the above, the purpose of this invention is to provide a low glycemic index blueberry extract and its preparation method. This invention combines probiotic fermentation with anthocyanin extraction technology, effectively enriching and stabilizing active substances such as anthocyanins in blueberries while preserving the fermented flavor and blood sugar-lowering effect, resulting in a low glycemic index, high anthocyanin content, and good-tasting blueberry extract.

[0006] To achieve the above objectives, the present invention provides the following technical solution: One of the technical solutions of this invention is a method for preparing a low glycemic index blueberry extract, comprising the following steps: Step 1. Preparation of blueberry fermentation liquid: Blueberries are pulped, and then fermented with a compound strain of Lactobacillus acidophilus, Lactobacillus plantarum and Bifidobacterium. The mixture is filtered through a membrane filtration device to obtain blueberry fermentation liquid. Step 2. Preparation of anthocyanin extract: Crush blueberries, adjust the pH of the ethanol solution to 2-3 with citric acid, then extract using ultrasound, collect the supernatant by centrifugation, and then distill the supernatant under reduced pressure to obtain anthocyanin extract concentrate; the ethanol content in the centrifuged supernatant reaches 65%-70%, and cannot be used directly. Remove the ethanol by rotary vacuum distillation to make the ethanol content in the anthocyanin extract less than 1%; Step 3. The anthocyanin extract concentrate is dried using freeze-drying technology to obtain dried anthocyanin extract; Step 4. Preparation: Mix the dried anthocyanin extract and blueberry fermentation broth at a mass-to-volume ratio of (0.2~0.3) g:1L until homogeneous. Then add maltitol to adjust the acidity and sweetness, homogenize, filter, and sterilize to obtain a low glycemic index blueberry extract. In this invention, mixing the fermentation broth and high-concentration extract in this ratio can achieve an anthocyanin content of over 400 mg / L. The amount of maltitol added in this invention is 8-12 g / L, aiming for a moderately sweet and sour taste.

[0007] In a preferred embodiment of the present invention, the mass ratio of Lactobacillus acidophilus, Lactobacillus plantarum, and Bifidobacterium is 2:1:2, and the total number of viable bacteria is 10. 8 ~10 11 CFU / mL; the inoculation amount of the compound strain is 1%~3% (v / v).

[0008] The present invention also tested the results when the mass ratio of Lactobacillus acidophilus, Lactobacillus plantarum and Bifidobacterium was 1:1:3 and 3:1:1. The results showed that only when the mass ratio of Lactobacillus acidophilus, Lactobacillus plantarum and Bifidobacterium was 2:1:2 could the fermentation of the compound strains at this ratio significantly improve the total phenol content and SOD activity, and achieve a harmonious flavor.

[0009] In a preferred embodiment of the present invention, the fermentation parameters are set as follows: anaerobic, temperature 27±1 ℃, and time 36±1 h.

[0010] The present invention also tested the fermentation effect at fermentation temperatures of 23 ℃, 25 ℃, and 29 ℃ and fermentation times of 27 h, 36 h, 48 h, and 54 h using a single variable method. The results showed that the fermentation effect was best when the fermentation temperature was 27±1 ℃ and the fermentation time was 36±1 h.

[0011] In a preferred embodiment of the present invention, the volume concentration of the ethanol solution is 65%~70%; the ratio of blueberries to the ethanol solution is 1:30-35 g / mL. Adjusting the ethanol solution to an acidic environment can stabilize the anthocyanin structure.

[0012] In a preferred embodiment of the present invention, the parameters for ultrasonic extraction are set as follows: ultrasonic power 200W, temperature 30℃~40℃, and extraction time 40~60 minutes.

[0013] In a preferred embodiment of the present invention, the centrifugation is performed at 4°C and 5000 r / min for 15 minutes.

[0014] The second technical solution of the present invention is a low glycemic index blueberry extract prepared by the above preparation method.

[0015] The present invention discloses the following technical effects: This invention provides a low glycemic index blueberry extract, which reduces sugar content through fermentation with compound probiotics, enhances the efficacy of active ingredients by combining anthocyanins extracted with alcohol, and is flavored with maltitol. The final product has anthocyanin ≥400 mg / L, is low GI, has a pleasant sweet and sour taste, and is suitable for people who control their blood sugar and are health-conscious consumers. Detailed Implementation

[0016] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0017] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0018] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0019] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0020] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0021] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0022] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0023] Example 1 1) Wash and pulp fresh blueberries, then inoculate with a mixture of Lactobacillus acidophilus, Lactobacillus plantarum, and Bifidobacterium for fermentation to obtain blueberry fermentation broth; wherein the mass ratio of Lactobacillus acidophilus, Lactobacillus plantarum, and Bifidobacterium is 2:1:2, and the total number of viable bacteria is above 10. 8 ~10 11 CFU / mL, inoculum size 2% (v / v); fermentation parameters: anaerobic, temperature 27±1 ℃, time 36±1h; 2) Crush the blueberries, adjust the pH of the ethanol solution to 2 with citric acid (food grade), then add the blueberries to the ethanol solution (volume concentration of 45%) at a material-to-liquid ratio of 1:40 and g / mL. Extract by ultrasonication at 200W and 30℃ for 40 min, then centrifuge at 4℃ and 5000r / min for 15 min, collect the supernatant, and then distill the supernatant under reduced pressure to obtain the anthocyanin extract concentrate. When the material-to-liquid ratio is 1:40 and the volume concentration of the ethanol solution is 45%, the anthocyanin content of blueberries in the anthocyanin extract concentrate is measured to be 1653.1 mg / L.

[0024] 3) The anthocyanin extract concentrate was dried using freeze-drying technology at a cold trap temperature of -70℃ until the anthocyanin extract concentrate was dried to obtain the dried anthocyanin extract.

[0025] 4) Mix the dried anthocyanin extract and blueberry fermentation liquid at a mass-volume ratio of 0.2g:1L. Then add maltitol to adjust the acidity and sweetness (8 g / L), homogenize, filter, and sterilize to obtain a low glycemic index blueberry extract.

[0026] Example 2 Similar to Example 1, except that the volume concentration of the ethanol solution was 55%. The anthocyanin content in the concentrated blueberry extract was measured to be 1729.4 mg / L.

[0027] Example 3 Similar to Example 1, except that the volume concentration of the ethanol solution was 65%. The anthocyanin content in the concentrated blueberry extract was measured to be 1929.6 mg / L.

[0028] Example 4 Similar to Example 1, except that the volume concentration of the ethanol solution was 70%. The anthocyanin content in the concentrated blueberry extract was measured to be 1934.2 mg / L.

[0029] In Examples 2-4, considering both extraction efficiency and cost, the volume concentration of the ethanol solution was selected as 65% and 70%, respectively.

[0030] Example 5 Similar to Example 3, the only difference was that the material-to-liquid ratio was 1:25. The anthocyanin content in the concentrated blueberry extract was measured to be 1861.8 mg / L.

[0031] Example 6 Similar to Example 3, the only difference was that the material-to-liquid ratio was 1:30. The anthocyanin content in the concentrated blueberry extract was measured to be 1927.4 mg / L.

[0032] Example 7 Similar to Example 3, the only difference was that the material-to-liquid ratio was 1:35. The anthocyanin content in the concentrated blueberry extract was measured to be 1928.4 mg / L.

[0033] In Examples 3 and 5-7, considering both extraction efficiency and cost, the material-to-liquid ratio of blueberries and ethanol solution was selected as 1:30 and 1:35 g / mL, respectively.

[0034] Example 8 1) Wash and pulp fresh blueberries, then inoculate with a mixture of Lactobacillus acidophilus, Lactobacillus plantarum, and Bifidobacterium for fermentation to obtain blueberry fermentation broth; wherein the mass ratio of Lactobacillus acidophilus, Lactobacillus plantarum, and Bifidobacterium is 2:1:2, and the total number of viable bacteria is above 10. 8 ~10 11 CFU / mL, inoculum size 2% (v / v); fermentation parameters: anaerobic, temperature 27±1 ℃, time 36±1h; 2) Crush the blueberries and adjust the pH of the ethanol solution (70% by volume) to 2 with citric acid (food grade). Then add the blueberries to the ethanol solution at a material-to-liquid ratio of 1:30 g / mL. Extract by ultrasonication at 200W and 30℃ for 40 min. Then centrifuge at 4℃ and 5000r / min for 15 min. Collect the supernatant and then distill the supernatant under reduced pressure to obtain the anthocyanin extract concentrate. 3) The anthocyanin extract concentrate was dried using freeze-drying technology at a cold trap temperature of -70℃ until the anthocyanin extract concentrate was dried to obtain the dried anthocyanin extract.

[0035] 4) Mix the dried anthocyanin extract and blueberry fermentation liquid at a mass-volume ratio of 0.2g:1L. Then add maltitol to adjust the acidity and sweetness (8 g / L), homogenize, filter, and sterilize to obtain a low glycemic index blueberry extract.

[0036] Example 9 1) Wash and pulp fresh blueberries, then inoculate with a mixture of Lactobacillus acidophilus, Lactobacillus plantarum, and Bifidobacterium for fermentation to obtain blueberry fermentation broth; wherein the mass ratio of Lactobacillus acidophilus, Lactobacillus plantarum, and Bifidobacterium is 1:1:1, and the total number of viable bacteria is above 10. 8 ~1011 CFU / mL, inoculum size 2% (v / v); fermentation parameters: anaerobic, temperature 27±1 ℃, time 36±1h; 2) Crush the blueberries, adjust the pH of the ethanol solution (70% by volume) to 2 with citric acid (food grade), then add the blueberries to the ethanol solution at a material-to-liquid ratio of 1:35 g / mL, and extract by ultrasonic extraction at 200W and 30℃ for 40 min. Then centrifuge at 4℃ and 5000r / min for 15 min, collect the supernatant, and then distill the supernatant under reduced pressure to obtain the anthocyanin extract concentrate. 3) The anthocyanin extract concentrate was dried using freeze-drying technology at a cold trap temperature of -70℃ until the anthocyanin extract concentrate was dried to obtain the dried anthocyanin extract.

[0037] 4) Mix the dried anthocyanin extract and blueberry fermentation liquid at a mass-volume ratio of 0.3g:1L. Then add maltitol to adjust the acidity and sweetness (addition amount is 10 g / L), homogenize, filter, and sterilize to obtain low glycemic index blueberry essence.

[0038] The following effects were verified on the blueberry extract obtained in Example 3. 1. Glycemic Index (GI) Measurement The glycemic index was determined according to WS / T 652—2019, "Methods for Determination of Glycemic Index of Foods". Regular blueberry juice (physically pressed from fresh blueberries): GI 56-60 (medium GI); The low glycemic index blueberry extract of this invention has a glycemic index (GI) of 38.4 and a GI ≤ 55. The blueberry extract of this invention is a low-glycemic food, suitable for people with diabetes and those who need to control their blood sugar.

[0039] 2. Anthocyanin content Anthocyanin content was determined according to the internationally accepted AOAC 2005.02 (pH differential method): Regular blueberry juice (physically pressed from fresh blueberries): anthocyanins 80–120 mg / L; The blueberry extract of this invention has an anthocyanin content that is consistently above 400 mg / L.

[0040] 3. Content of other active ingredients SOD enzyme activity (refer to GB / T 5009.171-2003 "Determination of Superoxide Dismutase (SOD) Activity in Health Foods"): Compared with ordinary blueberry juice obtained by physical juicing of fresh blueberries, the SOD enzyme activity is increased by 15-18%; Reducing sugar content (refer to GB 5009.7-2016 "National Food Safety Standard - Determination of Reducing Sugars in Food"): Compared with ordinary blueberry juice made by physical juicing of fresh blueberries, the reducing sugar content is reduced by 60-68%.

[0041] Evidence shows that fermentation with compound bacteria can effectively lower blood sugar and improve biological activity.

[0042] 4. Stability Testing Store at room temperature away from light for 6 months: Anthocyanin retention rate ≥85% (anthocyanin content determined according to the internationally accepted AOAC 2005.02 (pH differential method)). No sedimentation, no stratification, no browning; The product of this invention has excellent stability.

[0043] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a low glycemic index blueberry extract, characterized in that, Includes the following steps: Step 1. Preparation of blueberry fermentation liquid: Blueberries are pulped, and then fermented with a compound strain of Lactobacillus acidophilus, Lactobacillus plantarum and Bifidobacterium. The mixture is filtered through a membrane filtration device to obtain blueberry fermentation liquid. Step 2. Preparation of anthocyanin extract: Crush blueberries, adjust the pH of the ethanol solution to 2-3 with citric acid, then extract by ultrasonication, collect the supernatant by centrifugation, and then distill the supernatant under reduced pressure to obtain anthocyanin extract concentrate. Step 3. The anthocyanin extract concentrate is dried using freeze-drying technology to obtain dried anthocyanin extract; Step 4. Preparation: Mix the dried anthocyanin extract and blueberry fermentation liquid at a mass-volume ratio of (0.2~0.3) g: 1L until homogeneous. Then add maltitol to adjust the acidity and sweetness, homogenize, filter, and sterilize to obtain a low glycemic index blueberry extract.

2. The preparation method according to claim 1, characterized in that, The mass ratio of Lactobacillus acidophilus, Lactobacillus plantarum, and Bifidobacterium is 2:1:2, and the total number of viable bacteria is above 10. 8 ~10 11 CFU / mL; the inoculation amount of the compound bacterial strain is 1%~3%.

3. The preparation method according to claim 1, characterized in that, The fermentation parameters were set as follows: anaerobic, temperature 27±1 ℃, and time 36±1 h.

4. The preparation method according to claim 1, characterized in that, The volume concentration of the ethanol solution is 65%~70%, and the ratio of blueberries to ethanol solution is 1:30-35 g / mL.

5. The preparation method according to claim 1, characterized in that, The parameters for ultrasonic extraction were set as follows: ultrasonic power 200W, temperature 30℃~40℃, and extraction time 40~60 minutes.

6. The preparation method according to claim 1, characterized in that, The centrifugation was performed at 4°C and 5000 r / min for 15 minutes.

7. A low glycemic index blueberry extract prepared by the preparation method according to any one of claims 1-6.