Melon seeds with high tea polyphenol fragrance and preparation method thereof

Abstract

The invention belongs to the technical field of food processing, and relates to sunflower seeds with high tea polyphenol fragrance and a preparation method thereof. The invention aims to solve the technical problem that the flavor and aroma of the tea-flavored melon seeds are boring due to low tea polyphenol content and light tea flavor in a key raw material tea leaf extract of the tea-flavored melon seeds in the prior art. The preparation method comprises the following steps: uniformly mixing raw green tea and water according to a mass ratio of (3-5): 1, standing, and inoculating 1.5 * 10 < 6 > CFU / mL of Debaryomyces hansenii AS2.45 leavening agent for enhanced fermentation for 3-5 days after natural fermentation is finished; drying the fermented raw green tea, and adding 2-2.5 times by mass of water for extraction; boiling, adding melon seeds, continuously boiling, and braising, wherein the ratio of the high tea polyphenol soup to the water to the melon seeds is (1-3): (1-3): 1; according to the fragrant melon seeds prepared by combining the processes such as boiling and the like, the fragrance of the melon seed kernels and the tea fragrance are fully fused, the content of functional ingredients such as the tea polyphenol, dietary fibers and unsaturated fatty acid in the melon seeds is increased, and the nutritional value is high.

Description

Technical Field

[0001] The invention belongs to the technical field of food processing, and in particular relates to high-tea polyphenols fragrant melon seeds and a preparation method thereof. Background Art

[0002] Melon seeds are a common nut that is delicious, nutritious and healthy, and are deeply loved by the public. Studies have shown that melon seeds are rich in protein, unsaturated fatty acids, dietary fiber, vitamins, minerals, amino acids and other active substances, and have physiological benefits such as lowering cholesterol, anti-oxidation, enhancing immunity, moisturizing the intestines and laxatives, and strengthening the brain and calming the nerves. Tea is one of the health elements that men, women, young and old love. Tea polyphenols are the main biologically active ingredients in tea, mainly including catechins, flavonoids, anthocyanins, etc., which are one of the main components of the color, aroma and taste of tea. It is worth noting that tea polyphenols have the effects of protecting the nervous system and delaying aging. Tea polyphenols in tea are also the antioxidant and anti-aging factors that people pursue. At present, tea-flavored beverages are very popular on the market, but they are less used in the field of nuts or roasted seeds and nuts.

[0003] The difficulties in preparing tea-flavored melon seeds mainly include the following aspects: (1) Preparation of tea extract: The aroma and taste of tea need to be extracted by soaking or boiling, and tea polyphenols are an important factor affecting the aroma of tea. The content of tea polyphenols extracted by soaking or boiling is limited; (2) Selection and ratio of tea: It is necessary to select suitable tea varieties and determine their ratio with melon seeds to ensure that the tea aroma can be properly integrated into the melon seeds; (3) Control of temperature and time: During the boiling and frying process, the control of temperature and time is very critical and requires precise control to avoid burnt melon seeds or uneven tea flavor; (4) Maintaining the health-promoting ingredients of tea: Tea contains a variety of health-promoting ingredients that are beneficial to the human body. How to maximize the retention of these ingredients during the processing process; (5) Avoid adding pigments and spices: Some tea-flavored melon seeds on the market may have added pigments and spices, but real tea-flavored melon seeds should be flavored with the natural aroma of tea instead of relying on additives. In the process of preparing tea-flavored melon seeds, it is necessary to comprehensively consider the preparation of the extract, the selection of raw materials, the processing technology and other aspects to ensure that the final product has both the fragrance of tea and the original taste and nutritional value of melon seeds. Therefore, how to efficiently extract the content of tea polyphenols in tea and better impart the tea fragrance and flavor to melon seeds is an urgent problem to be solved.

[0004] The Chinese invention patent application publication number is CN105558591A, the application date is November 7, 2014, and the invention name is "Production process of tea melon seeds snacks". The disclosed method includes the following steps: 100 portions of selected sunflower seeds are screened; the selected sunflower seeds are soaked in warm salt water for 20 to 30 minutes; an appropriate amount of water and 5 to 20 portions of tea leaves are added to the soaked sunflower seeds, and steamed for 90 minutes; the cooked sunflower seeds are taken out and dried for 20 to 30 minutes. This method directly boils the soaked melon seeds and tea leaves together, which cannot fully extract the tea polyphenols in the tea leaves, and the resulting melon seed tea has a poor aroma.

[0005] In the prior art, there are public methods for using the special physiological metabolic activities of microorganisms to change the chemical composition and sensory quality of tea leaves, among which the aroma of tea soup can be increased by co-fermentation of Debaryomyces hansenii and Aspergillus niger. For example, the Chinese invention patent application publication number is CN106106910A, the application date is July 15, 2016, and the invention name is "A method for preparing tea concentrate". The disclosed method includes the following steps: primary fermentation of tea leaves to enhance aroma, rotary cone column distillation to extract aroma, secondary fermentation to enhance taste after tea soup concentration, and then compounding aroma and taste substances to obtain tea concentrate. The primary fermentation uses one of Schizosaccharomyces pombe, Kluyveromyces lactis or Kluyveromyces fragilis, and the secondary fermentation is inoculated with Debaryomyces hansenii and Aspergillus niger. If this method is applied to the preparation of fragrant melon seeds, there will be the following shortcomings: (1) Although this method can reduce the proportion of ester-type catechins, it does not transport tea polyphenols in tea leaves, and the effect of flavoring melon seeds may be poor; (2) secondary inoculation and fermentation are required, the preparation process is cumbersome, and it is easy to be contaminated with bacteria. Summary of the invention

[0006] 1. Problems to be solved

[0007] The prior art tea-flavored melon seeds have a low tea polyphenol content in tea extract, a light tea flavor, and a technical problem that the tea-flavored melon seeds have a bland flavor and aroma. The present application provides a method for preparing high-tea polyphenol-flavored melon seeds, wherein the prepared tea soup base contains a high level of tea polyphenols, and the tea aroma is purer and richer. The scented melon seeds prepared by combining the cooking process have a fully integrated melon seed kernel aroma and a tea aroma, and the aroma is maintained without dissipating. The content of functional ingredients such as tea polyphenols, dietary fiber, and unsaturated fatty acids in the melon seeds is increased, and the nutritional value is higher.

[0008] 2. Technical solution

[0009] In order to achieve the above purpose, the technical solution provided is:

[0010] The preparation method of high tea polyphenols flavor melon seeds comprises the following steps:

[0011] The raw green tea and water were mixed at a mass ratio of 3-5:1 and then allowed to stand. After the natural fermentation was completed, the Hansen Debaryomyces AS2.45 starter was inoculated with an inoculum of 1.5×10 6 CFU / mL, and then allowed to stand for intensive fermentation for 3 to 5 days to obtain fermented green tea;

[0012] After drying the fermented green tea, adding 2 to 2.5 times the mass of water for extraction to obtain a high tea polyphenol soup base;

[0013] Add water to the high tea polyphenols soup base and boil it, add melon seeds and continue to boil and then simmer, wherein the ratio of the high tea polyphenols soup base: water: melon seeds is 1-3:1-3:1 by weight, to obtain wet melon seeds;

[0014] The wet melon seeds are gradient dried to obtain the high tea polyphenols flavored melon seeds.

[0015] Preferably, the natural fermentation time is 28 to 29 days. Put the raw green tea and water into a fermentation tank, stir evenly and let it stand, turning the pile every 7 days.

[0016] Preferably, the preparation of the Debaryomyces hansenii AS2.45 starter is as follows: streaking the Debaryomyces hansenii AS2.45 plate on a malt agar medium, and culturing at 28°C for 48 hours; using a sterile inoculation loop to pick 2 loops and place them in a YPD liquid medium, shaking and culturing at 28°C and 170 r / min for 36 hours to obtain an activated bacterial solution; removing part of the activated bacterial solution, inoculating it into a new YPD liquid medium, shaking and culturing at 28°C and 170 r / min for 36 hours, and obtaining 1.5×10 6 CFU / mL of Debaryomyces hansenii AS2.45 starter culture.

[0017] Furthermore, the high tea polyphenols soup base is boiled for 5 minutes after adding water, the melon seeds are added and continued to be boiled for 15 minutes, and the stewing time is 60 minutes.

[0018] Furthermore, the gradient drying is carried out in three temperature zones, and the temperature of each temperature zone is as follows: 80°C ≤ temperature zone 1 ≤ 90°C; 90°C ≤ temperature zone 2 ≤ 105°C; 105°C ≤ temperature zone 3 ≤ 115°C.

[0019] Furthermore, the drying time of each temperature zone is as follows: 50min≤temperature zone 1≤60min; 50min≤temperature zone 2≤60min; 60min≤temperature zone 3≤70min.

[0020] Preferably, the ramp time between each temperature zone is set to 3 to 5 minutes.

[0021] Furthermore, in the extraction step, ultrasonic treatment is used, and the treatment parameters are: frequency 30-50 kHz, power 250-350 W, temperature 35-45° C., and time 20-40 min.

[0022] Furthermore, the high tea polyphenols soup base is sterilized and filtered.

[0023] Preferably, the sterilization temperature is 121° C. and the time is 30 min; a microporous filter membrane is used for filtration.

[0024] Furthermore, the drying process is freeze-drying.

[0025] Furthermore, the melon seeds are one or more of sunflower seeds, watermelon seeds or pumpkin seeds.

[0026] Furthermore, the water content of the melon seeds is 2 to 2.8%.

[0027] The high-tea polyphenols fragrant melon seeds are prepared by the method.

[0028] 3. Beneficial effects

[0029] Compared with the existing known technology, the technical solution provided by the present invention has the following beneficial effects:

[0030] (1) The method for preparing high tea polyphenols flavored melon seeds of the present invention comprises mixing green tea and water in a mass ratio of 3 to 5:1 and then standing for natural fermentation. A series of chemical changes occur under the action of microorganisms. In this process, tea polyphenols and catechins undergo oxidation, polymerization, condensation, decomposition and other reactions to form the unique color, aroma and taste of Pu'er tea. However, in this case, tea polyphenols and the like are not easily extracted if the soup base is prepared directly. Therefore, after natural fermentation, the Hansen Debaryomyces AS2.45 starter is inoculated and allowed to stand for intensive fermentation for 3 to 5 days. The inoculation amount is 1.5×10 6CFU / mL. After the fermented green tea is dried, 2 to 2.5 times the mass of water is added for extraction to obtain a high tea polyphenol soup base. Hansen Debaryomyces AS2.45 can transport tea polyphenols and other flavor substances out of tea cells during natural fermentation. The prepared tea soup base contains higher tea polyphenols, and the tea aroma is purer and richer. The content of key volatile substances such as aldehydes (benzaldehyde, 2,4-decanedialdehyde), ketones (tea ketone, α-ionone, verbenone), alcohols (linalool, geraniol, phenylethyl alcohol, 1-octen-3-ol, verbenone), and esters (γ-butyrolactone, dihydroactinol) in the tea soup base is significantly increased, making the tea soup base more flavorful. And no pigment is added to the tea soup base, which is different from the mainstream "fake" tea flavor modulation and added pigment products on the market. Add water to the high tea polyphenols soup base and boil it, add melon seeds and continue to boil and then simmer, the ratio of high tea polyphenols soup base: water: melon seeds is 1-3:1-3:1 by weight, and gradient drying is performed to obtain high tea polyphenols flavored melon seeds. The cooking and drying of the present application allow the unique flavor of tea and the functional ingredients in the high tea polyphenols soup base to fully enter and be trapped in the melon seeds, while fully blending the aroma of the melon seed kernel with the aroma of tea.

[0031] (2) The high tea polyphenols flavor melon seeds of the present invention have a purer and richer tea flavor. The contents of functional ingredients such as tea polyphenols, dietary fiber, and unsaturated fatty acids in the melon seeds are increased, and the nutritional value is higher. DETAILED DESCRIPTION

[0032] In order to further understand the content of the present invention, the present invention is described in detail in conjunction with embodiments.

[0033] In the embodiments of the present application, the dietary fiber content is determined according to the provisions of GB 5009.88-2014 "National Food Safety Standard for the Determination of Dietary Fiber in Foods", using the enzyme weight method; the unsaturated fat content is determined according to the provisions of GB5009.168-2016 "National Food Safety Standard for the Determination of Fatty Acids in Foods", using the acetyl chloride-methanol method.

[0034] Example 1

[0035] The method for preparing high tea polyphenols flavored melon seeds of the present embodiment comprises the following steps:

[0036] S1. Preparation of starter culture

[0037] Debaryomyces hansenii AS2.45 used in this example was purchased from Shanghai Bioresource Collection Center (SHBCC), numbered SHBCC D11322 = AS2.45 = ACCC20010. Debaryomyces hansenii AS2.45 was streaked on a malt agar medium and cultured at 28°C for 48 hours; two loops were picked up with a sterile inoculation loop and placed in a YPD liquid medium, and cultured at 28°C and 170 r / min for 36 hours; a portion of the activated bacterial solution (2 v / v%) was transferred to a new YPD liquid medium, and the above-mentioned shaking culture operation was repeated. After the activity of the strain was stable, the plate was smeared and counted to prepare 1.5×10 6 CFU / mL of Debaryomyces hansenii AS2.45 starter culture.

[0038] S2. Fermentation

[0039] The green tea used in this example is Pu'er tea. 75 kg of green tea and 25 kg of pure water were placed in a stainless steel fermentation tank, stirred evenly, and left to ferment. The compost was turned every 7 days. On the 28th day, the Hansen Debaryomyces AS2.45 starter was inoculated with an inoculum of 1.5×10 6 CFU / mL, stir evenly and continue to ferment for 3 days to obtain fermented Pu'er tea.

[0040] S3. Preparation of soup base

[0041] The fermented Pu'er tea is dried, packaged, extracted, sterilized, filtered and stored to obtain a high tea polyphenol soup base.

[0042] The specific method is as follows:

[0043] ① Drying and packaging: Place the fermented Pu'er tea in a vacuum freeze dryer for 24 hours. After obtaining the dried Pu'er tea, divide it into several bags with a weight of 10kg per bag.

[0044] ② Extraction: Take out 10kg of dried Pu'er tea and mix it with 20kg of pure water, and subject the mixture to ultrasonic treatment at an ultrasonic frequency of 30kHZ, an ultrasonic power of 250W, an ultrasonic temperature of 35℃, and an ultrasonic time of 20min;

[0045] ③ Sterilization: transfer the soup base after ultrasonic extraction into a high pressure sterilizer for sterilization at a temperature of 121°C and a sterilization time of 30 minutes;

[0046] ④Filtration: The sterilized tea soup is filtered using a microporous filter membrane;

[0047] ⑤Storage: Transfer the filtered tea into a can and store it at 4°C for later use.

[0048] S4. Cooking

[0049] The melon seeds used in this embodiment are sunflower seeds. 1 kg of the above-mentioned high tea polyphenols soup base is mixed with 3 kg of pure water at 100° C. and boiled for 5 minutes. 1 kg of sunflower seeds is poured into the above-mentioned boiling system, and the boiling is continued for 15 minutes. The heat is turned off and the mixture is allowed to stand and simmer for 60 minutes. The wet melon seeds are obtained after being drained.

[0050] S5, gradient drying

[0051] The wet melon seeds are dried in a gradient manner until the moisture content is 2% to obtain fragrant melon seeds. Specifically, a mesh belt drying equipment is used to dry the seeds in three temperature zones. The parameters of each temperature zone are as follows:

[0052] In temperature zone 1, the drying temperature is 80℃ and the drying time is 50min, which removes excess moisture from the outer shell of the melon seeds. In temperature zone 2, the drying temperature is 90℃ and the drying time is 50min, which allows the unique flavor of Pu'er tea and the functional ingredients in the soup base such as tea polyphenols, vitamin C, and minerals to fully enter and be trapped inside the melon seeds. In temperature zone 3, the drying temperature is 105℃ and the drying time is 60min, which fully dries the melon seeds and fully integrates the aroma of the melon seeds with the aroma of Pu'er tea, and maintains the aroma of Pu'er tea without spreading. A temperature ramp process is set between each temperature zone, and the ramp time is 3min. The moisture content of the melon seeds after leaving the drying line is 2%. After the melon seeds are naturally cooled to room temperature, they are packed with nitrogen to obtain the finished fragrant melon seeds.

[0053] In this embodiment, Pu'er tea and Debaryomyces hansenii AS2.45 are co-fermented to prepare a high tea polyphenol soup base, which contains high tea polyphenols and has a purer and richer tea flavor. The prepared fragrant melon seeds have a good overall flavor and high acceptance. Among them, the content of key volatile substances is relatively high: the total amount of alcohol substances reaches 23.99μg / g, the total amount of ketone substances reaches 31.67μg / g, and the total amount of ester substances reaches 34.25μg / g, giving the melon seeds a pure and rich tea flavor. In addition, the content of functional ingredients is significantly improved: the content of tea polyphenols is 33.7mg / g, the content of dietary fiber is 81.2mg / g, and the content of unsaturated fatty acids is 100.9mg / g.

[0054] Example 2

[0055] The preparation method of high tea polyphenols flavored melon seeds in this embodiment is basically the same as that in embodiment 1, except that:

[0056] S2. Fermentation

[0057] The green tea used in this example is Pu'er tea. 125 kg of green tea and 25 kg of pure water were placed in a stainless steel fermentation tank, stirred evenly, and left to ferment. The compost was turned every 7 days. On the 28th day, the Hansen Debaryomyces AS2.45 starter was inoculated with an inoculum of 1.5×10 6 CFU / mL, stir evenly and continue to ferment for 5 days to obtain fermented Pu'er tea.

[0058] S3. Preparation of soup base

[0059] ② Extraction: Take out 10kg of dried Pu'er tea and mix it with 20kg of pure water, and subject the mixture to ultrasonic treatment at an ultrasonic frequency of 50kHZ, an ultrasonic power of 350W, an ultrasonic temperature of 45℃, and an ultrasonic time of 40min;

[0060] S4. Cooking

[0061] The melon seeds used in this embodiment are sunflower seeds. 3 kg of the above-mentioned high tea polyphenols soup base and 1 kg of pure water are mixed and boiled at 100° C. for 5 minutes. 1 kg of sunflower seeds are poured into the above-mentioned boiling system and continue to boil for 15 minutes. Turn off the heat and let it stand and simmer for 60 minutes. After draining, wet melon seeds are obtained.

[0062] S5, gradient drying

[0063] The wet melon seeds are gradient dried to a moisture content of 2.8% to obtain fragrant melon seeds. Specifically, a mesh belt drying equipment is used to dry the seeds in three temperature zones. The parameters of each temperature zone are as follows:

[0064] In temperature zone 1, the drying temperature is 90℃ and the drying time is 60min, which removes excess moisture from the outer shell of the melon seeds. In temperature zone 2, the drying temperature is 105℃ and the drying time is 60min, which allows the unique flavor of Pu'er tea and the functional ingredients in the soup base such as tea polyphenols, vitamin C, and minerals to fully enter and be trapped inside the melon seeds. In temperature zone 3, the drying temperature is 115℃ and the drying time is 70min, which fully dries the melon seeds and fully integrates the aroma of the melon seeds with the aroma of Pu'er tea, and maintains the aroma of Pu'er tea without spreading. A temperature ramp process is set between each temperature zone, and the ramp time is 5min. The moisture content of the melon seeds after leaving the drying line is 2.8%. After the melon seeds are naturally cooled to room temperature, they are packed with nitrogen to obtain the finished fragrant melon seeds.

[0065] The finished product of the fragrant melon seeds prepared in this embodiment has a good effect of combining tea aroma and melon seed kernel aroma. At the same time, the content of functional ingredients is also significantly improved: the content of tea polyphenols is 30.2 mg / g, the content of dietary fiber is 83.9 mg / g, and the content of unsaturated fatty acids is 102.5 mg / g.

[0066] Example 3

[0067] The preparation method of high tea polyphenols flavored melon seeds in this embodiment is basically the same as that in embodiment 1, except that:

[0068] S2. Fermentation

[0069] The green tea used in this example is Pu'er tea. 100 kg of green tea and 25 kg of pure water were placed in a stainless steel fermentation tank, stirred evenly, and left to ferment. The compost was turned every 7 days. On the 28th day, the Hansen yeast AS2.45 starter was inoculated with an inoculum of 1.5×10 6 CFU / mL, stir evenly and continue to ferment for 4 days to obtain fermented Pu'er tea.

[0070] S3. Preparation of soup base

[0071] ② Extraction: Take out 10kg of dried Pu'er tea and mix it with 20kg of pure water, and subject the mixture to ultrasonic treatment at an ultrasonic frequency of 40kHZ, an ultrasonic power of 300W, an ultrasonic temperature of 40℃, and an ultrasonic time of 30min;

[0072] S4. Cooking

[0073] The melon seeds used in this embodiment are sunflower seeds. 2 kg of the above-mentioned high tea polyphenols soup base and 2 kg of pure water are mixed and boiled at 100° C. for 5 minutes. 1 kg of sunflower seeds are poured into the above-mentioned boiling system and continue to boil for 15 minutes. Turn off the heat and let it stand and simmer for 60 minutes. After draining, wet melon seeds are obtained.

[0074] S5, gradient drying

[0075] The wet melon seeds are gradient dried to a moisture content of 2.4% to obtain fragrant melon seeds. Specifically, a mesh belt drying equipment is used to dry the seeds in three temperature zones. The parameters of each temperature zone are as follows:

[0076] In temperature zone 1, the drying temperature is 85℃ and the drying time is 55min, which removes excess moisture from the outer shell of the melon seeds. In temperature zone 2, the drying temperature is 100℃ and the drying time is 55min, which allows the unique flavor of Pu'er tea and the functional ingredients in the soup base such as tea polyphenols, vitamin C, and minerals to fully enter and be trapped inside the melon seeds. In temperature zone 3, the drying temperature is 110℃ and the drying time is 65min, which fully dries the melon seeds and fully integrates the aroma of the melon seeds with the aroma of Pu'er tea, and maintains the aroma of Pu'er tea without spreading. A temperature ramp process is set between each temperature zone, and the ramp time is 4min. The moisture content of the melon seeds after leaving the drying line is 2.4%. After the melon seeds are naturally cooled to room temperature, they are packed with nitrogen to obtain the finished fragrant melon seeds.

[0077] The fragrant melon seeds prepared in this embodiment have a strong tea aroma and flavor. At the same time, the functional component content is the highest: the tea polyphenol content is 38.5 mg / g, the dietary fiber content is 85.4 mg / g, and the unsaturated fatty acid content is 104.6 mg / g.

[0078] It can be seen from Examples 1-3 that microorganisms can change the chemical composition and sensory quality of tea leaves through special physiological metabolic activities. Debaryomyces hansenii has the ability to metabolize proteins, lipids, lactic acid, malic acid and other substances to produce flavor substances, and is a typical food-borne yeast. This yeast has been widely used in a variety of fermented foods and food processing, food safety and food storage such as fruit and vegetable disease antagonism. However, Debaryomyces hansenii AS2.45 is still very rare in the research of tea fermentation. This application selects Pu'er tea and Debaryomyces hansenii AS2.45 for co-fermentation, and uses extraction, sterilization and filtration processes. The obtained tea soup base contains higher tea polyphenols, and the tea aroma is purer and richer. The sunflower seeds are boiled together with the high tea polyphenols soup base of this embodiment and then dried, so that the fragrance of the obtained scented melon seeds tea is purer and richer. At the same time, the contents of key volatile substances such as aldehydes (benzaldehyde, 2,4-sunflower dienal), ketones (tea ketone, α-ionone, verbenone), alcohols (linalool, geraniol, phenylethyl alcohol, 1-octen-3-ol, verbenol), esters (γ-butyrolactone, dihydroactinol) in the scented melon seeds are significantly improved (as shown in Table 1), giving the scented melon seeds a unique aroma. The contents of functional ingredients such as tea polyphenols, dietary fiber, and unsaturated fatty acids in the melon seeds are increased (as shown in Table 3), and the nutritional value is higher.

[0079] The method of the present application is not limited to sunflower seeds, and other types of seeds, such as watermelon seeds or pumpkin seeds, can also achieve the technical effects of the present application.

[0080] Comparative Example 1

[0081] The preparation method of high tea polyphenols flavored melon seeds in this comparative example is basically the same as that in Example 3, except that:

[0082] In this comparative example, the tea soup base is prepared by non-enhanced fermentation, without adding Debaryomyces hansenii AS2.45, the S1 step is cancelled, and the S2 step is changed to non-enhanced fermentation. The specific steps are as follows:

[0083] 100 kg of green tea and 25 kg of pure water were placed in a stainless steel fermentation tank, stirred evenly, and left to ferment. The pile was turned over every 7 days, and samples were taken out on the 35th day to end the natural fermentation process and obtain fermented Pu'er tea.

[0084] The melon seeds prepared in this comparative example have a weak characteristic flavor and a bland taste overall. This is mainly due to the lack of enhanced fermentation of key strains, and special aroma substances cannot be presented in the soup base. For example, key aroma components such as 1-octen-3-ol, linalool, geraniol, 2,4-contenal, α-ionone, and verbenanesone were not detected. At the same time, the contents of tea polyphenols, dietary fiber, and unsaturated fatty acids in melon seeds are 4.7 mg / g, 76.7 mg / g, and 91.1 mg / g, respectively, which are reduced by 87.8%, 10.2%, and 12.9% compared with Example 3, respectively.

[0085] Comparative Example 2

[0086] The preparation method of high tea polyphenols flavored melon seeds in this comparative example is basically the same as that in Example 3, except that:

[0087] S1. Preparation of starter culture

[0088] The brewer's yeast RW used in this comparative example was purchased from Angel Yeast Co., Ltd. (Hubei, China). The brewer's yeast RW was placed in 37°C sugar water (1:20, W / V) for 30 minutes to activate, and the activated brewer's yeast RW was obtained; the activated brewer's yeast RW was centrifuged at a speed of 4000 r / min for 8 minutes, and the supernatant after centrifugation was taken for purification and culture, and the bacterial solution concentration was adjusted to 1.5×10 6 CFU / mL, and obtained the Saccharomyces cerevisiae RW starter.

[0089] S2. Fermentation

[0090] The tea raw material used in this comparative example is Pu'er tea. 100 kg of green tea and 25 kg of pure water are placed in a stainless steel fermentation tank and stirred evenly, and then left to ferment. The pile is turned over every 7 days. On the 28th day, the brewer's yeast RW fermentation agent is added, stirred evenly, and then left to ferment. On the 35th day, the sample is taken out, and the fermentation is terminated to obtain the fermented Pu'er tea.

[0091] In this comparative example, the melon seeds prepared by using Saccharomyces cerevisiae RW instead of Debaryomyces hansenii AS2.45 for enhanced fermentation treatment did not have a prominent characteristic flavor. This is mainly because the physiological activities of Saccharomyces cerevisiae RW and Debaryomyces hansenii AS2.45 are different. The results of volatile substance detection show that the melon seeds in this comparative example tend to have a floral aroma and lack the special woody aroma of Pu'er tea. Therefore, the overall tolerance is low.

[0092] Comparative Example 3

[0093] The preparation method of high tea polyphenols flavored melon seeds in this comparative example is basically the same as that in Example 3, except that:

[0094] In the preparation steps of S3 soup base, ② extraction process: ultrasonic frequency is 25kHZ, ultrasonic power is 200W, ultrasonic temperature is 50℃, and ultrasonic time is 50min.

[0095] This comparative example changed the extraction process, and the results showed that the extraction rate of functional components was reduced. Among them, the contents of tea polyphenols, dietary fiber, and unsaturated fatty acids in melon seeds were 10.8 mg / g, 79.4 mg / g, and 91.3 mg / g, respectively, which were reduced by 71.9%, 7.0%, and 12% compared with Example 3.

[0096] Comparative Example 4

[0097] The preparation method of high tea polyphenols flavored melon seeds in this comparative example is basically the same as that in Example 3, except that:

[0098] S4. Cooking

[0099] Take 2kg of the above-mentioned high tea polyphenols soup base and 2kg of pure water, mix them at 100°C and boil them for 5 minutes, take 1kg of sunflower seeds and pour them into the above-mentioned boiling system, continue to boil for 10 minutes, turn off the heat and let it stand and simmer for 30 minutes, repeat the above steaming and simmering process twice, and drain to obtain wet melon seeds.

[0100] The melon seeds prepared in this comparative example have a single aroma and lack tea aroma and woody aroma. The cooking process is the key process for the melon seeds to be flavored. Excessive cooking temperature and repeated cooling process are not conducive to the retention of aroma substances. Dietary fiber will partially dissolve or degrade in a high temperature and water environment. Under this process condition, the dietary fiber content is 75.6 mg / g, which is 11.5% less than that of Example 3.

[0101] Comparative Example 5

[0102] The preparation method of high tea polyphenols flavored melon seeds in this comparative example is basically the same as that in Example 3, except that:

[0103] S5, gradient drying

[0104] The wet melon seeds are dried in a gradient manner until the moisture content is below 2% to obtain the finished melon seeds. Specifically, a mesh belt drying equipment is used to dry the seeds in three temperature zones. The parameters of each temperature zone are as follows:

[0105] Temperature zone 1, drying temperature is 100℃, time is 70min; temperature zone 2, drying temperature is 110℃, time is 60min; temperature zone 3, drying temperature is 120℃, time is 50min. The ramp time between each temperature zone is 8min; the moisture content of melon seeds after leaving the drying line is less than 2%.

[0106] The melon seeds prepared in this comparative example have a very weak aroma, wherein special aroma substances such as 1-octen-3-ol, phenylethyl alcohol, geraniol, γ-butyrolactone, dihydroactin, tea ketone, verbenone, etc. are not detected.

[0107] Table 1 Key volatile substance content (μg / g)

[0108]

[0109] Note: In this study, gas chromatography was used for detection, with 2-octanol as the internal standard substance, and ND means not detected.

[0110] Table 2 Distribution of key volatile substances and aroma characteristics

[0111]

[0112] Table 3 Content of key functional ingredients (mg / g)

[0113]

[0114] In summary, the preparation method of high tea polyphenols flavored melon seeds of the present application is to connect the Hansen Debaryomyces AS2.45 fermentation agent to strengthen the fermentation after the natural fermentation of Pu'er tea, and match it with the extraction, sterilization and filtration processes. Hansen Debaryomyces AS2.45 can transport tea polyphenols and other flavor substances in the natural fermentation out of the tea cells. The prepared tea soup base contains higher tea polyphenols, the tea flavor is purer and richer, and the content of key volatile substances in the tea soup base is significantly improved, making the tea soup base more flavorful. The high tea polyphenols soup base is added to the melon seeds, boiled and dried, and the obtained flavored melon seeds have a purer and richer tea flavor. After gas chromatography detection, the results are shown in Tables 1-3. The content of key volatile substances and functional ingredients in the melon seeds are significantly improved, and the nutritional value is higher.

[0115] The above-mentioned embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present invention. It should be pointed out that, for a person skilled in the art, several modifications, improvements and substitutions can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the attached claims.

Claims

1. A method for preparing high tea polyphenols flavored melon seeds, characterized in that: The following steps are involved: The raw green tea and water were mixed at a mass ratio of 3-5:1 and then allowed to stand. After the natural fermentation was completed, the Hansen Debaryomyces AS2.45 starter was inoculated with an inoculum of 1.5×10 6 CFU / mL, and then allowed to stand for intensive fermentation for 3 to 5 days to obtain fermented green tea; After drying the fermented green tea, adding 2 to 2.5 times the mass of water for extraction to obtain a high tea polyphenol soup base; Add water to the high tea polyphenols soup base and boil it, add melon seeds and continue to boil and then simmer, wherein the ratio of the high tea polyphenols soup base: water: melon seeds is 1-3:1-3:1 by weight, to obtain wet melon seeds; The wet melon seeds are gradient dried to obtain the high tea polyphenols flavored melon seeds.

2. The method for preparing high tea polyphenols flavored melon seeds according to claim 1, characterized in that: The time for boiling the high tea polyphenols soup base with water is 5 minutes, the time for continuing to boil after adding melon seeds is 15 minutes, and the time for stewing is 60 minutes.

3. The method for preparing high tea polyphenols flavored melon seeds according to claim 2, characterized in that: Gradient drying is carried out in three temperature zones, and the temperatures in each temperature zone are as follows: 80°C ≤ temperature zone 1 ≤ 90°C; 90°C ≤ temperature zone 2 ≤ 105°C; 105°C ≤ temperature zone 3 ≤ 115°C.

4. The method for preparing high tea polyphenols flavored melon seeds according to claim 3, characterized in that: The drying time of each temperature zone is as follows: 50min≤temperature zone 1≤60min; 50min≤temperature zone 2≤60min; 60min≤temperature zone 3≤70min.

5. The method for preparing high tea polyphenols flavored melon seeds according to claim 4, characterized in that: In the extraction step, ultrasonic treatment is used, and the treatment parameters are: frequency 30-50 kHz, power 250-350 W, temperature 35-45° C., and time 20-40 min.

6. The method for preparing high tea polyphenols flavored melon seeds according to claim 5, characterized in that: The high tea polyphenols soup base is sterilized and filtered.

7. The method for preparing high tea polyphenols flavored melon seeds according to claim 6, characterized in that: The drying process is freeze drying.

8. The method for preparing high tea polyphenols flavored melon seeds according to claim 7, characterized in that: The melon seeds are one or more of sunflower seeds, watermelon seeds or pumpkin seeds.

9. The method for preparing high tea polyphenols flavored melon seeds according to claim 8, characterized in that: The water content of the melon seeds is 2-2.8%.

10. High tea polyphenols flavored melon seeds, characterized by: Prepared by the method according to any one of claims 1 to 9.

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