A kind of high anthocyanin purple yam slices and preparation method thereof

Abstract

The invention discloses a high-anthocyanin purple yam slice and a preparation method thereof. The high-anthocyanin purple yam slice is obtained by peeling the purple yam, washing it with clean water, and then slicing it, and then boiling, protecting the color, vacuum packaging and sterilizing it. The boiling process is to put the purple yam slices into a normal pressure boiling container, add the prepared acidic electrolyzed water to cover the purple yam slices, and boil them for 10 to 30 minutes at a temperature of 60 to 80°C. The acidic electrolyzed water is prepared by electrolysis of dilute hydrochloric acid solution and sodium chloride solution, and the effective chlorine concentration ACC is 60 to 90ppm, the pH is 2.5 to 4.0, and the oxidation-reduction potential ORP is 950 to 1200mV. The invention solves the problem of high anthocyanin loss of purple yam slices in traditional heating treatment, and the obtained anthocyanin retention amount is high. In addition, the invention inhibits the growth of microorganisms in the purple yam slices during storage, and effectively prolongs the shelf life of the purple yam product. The preparation method of the invention is simple, low-cost, and suitable for large-scale production.

Description

Technical Field

[0001] The present invention discloses a purple yam, specifically relates to a high-anthocyanin purple yam slice and a preparation method thereof; belongs to the technical field of food processing, Background Art

[0002] Purple yam is a plant of the Dioscoreaceae family and the Dioscorea genus. It is rich in yield and is planted on a large scale in most provinces and regions of my country, such as Guangdong, Yunnan, Zhejiang, Fujian, etc. Purple yam is rich in nutrients such as starch, protein, polysaccharides, as well as trace substances such as anthocyanins, diosgenin, glycoprotein, and allantoin. Therefore, purple yam has the effects of lowering blood sugar, lowering blood lipids, anti-aging, anti-tumor, and anti-oxidation.

[0003] Purple yam has a strong seasonality and is prone to rot and disease during storage. Cleaning and peeling are time-consuming and laborious, and its mucus will cause itching when it comes into contact with the skin during peeling, which seriously affects the sales of purple yam. At present, purple yam is mainly made into crisps and whole powder, but the high temperature in traditional processing will cause the active substances such as anthocyanins and polysaccharides in purple yam to lose their activity and reduce their antioxidant activity. For example, Zhang Ziqi et al. (Zhang Ziqi, Wang Feng, Li Qingming, et al. Effect of drying method on the physical properties and antioxidant capacity of purple yam whole powder [J]. Food Research and Development, 2018, 39(19): 26-31.) prepared by hot air drying, the anthocyanin content of purple yam whole powder was 5.49±0.36mg / 100g, and its color browning was the most serious. Zhang Hong et al. (Zhang Hong. Study on the drying characteristics and quality of purple sweet potato slices by microwave and infrared treatment [D]. Hefei University of Technology, 2020.001543.) The anthocyanin content of purple sweet potato crisps obtained by high-temperature frying was only 0.015 mg / mL, and the antioxidant activity was significantly reduced. This shows that hot air drying and high-temperature frying will damage the structure of anthocyanins and reduce their content. The existing technology mainly protects the anthocyanins of purple yam by controlling the pH value and lowering the processing temperature, such as adding 2% chitosan or tea polyphenols and other high-concentration colorants to maintain the color of the product, but high concentrations of colorants will affect the taste and other nutrients of the product, and lowering the processing temperature will bring about problems such as product instability, easy browning and excessive total bacterial count. Therefore, it is of great significance to study how to reduce the loss of anthocyanins during processing and extend the storage period of the product for the high added value utilization of purple yam.

[0004] Acidic electrolyzed water is a colorless and odorless solution with bactericidal effect produced by electrolyzing dilute hydrochloric acid and sodium chloride solution to change the pH value and oxidation-reduction potential (ORP) of the solution. Acidic electrolyzed water can be used for non-thermal sterilization, and has the advantages of good bactericidal effect, wide sterilization range, low cost, simple and convenient preparation, safety and environmental protection, etc. It is widely used in the sterilization of meat, fruits and vegetables. Chinese invention patent application CN107889881A discloses a method for inhibiting browning of fresh-cut yam; the method specifically comprises the following steps: (1) material selection: selecting fresh yam with uniform thickness, no mechanical damage and no disease; (2) cleaning: washing with running water to remove impurities and some microorganisms; (3) soaking in acidic electrolyzed water and peeling at the same time: the yam washed with running water is soaked in acidic electrolyzed water and peeled at the same time, wherein the pH value of the acidic electrolyzed water is 2.0-3.5, the effective chlorine content is 50-70 mg / L, and the soaking time is 15-25 min; (4) cutting: cutting the peeled yam into slices, blocks or sections with a slicer; (5) composite coating liquid treatment: soaking the cut yam in the composite coating liquid for 1 min; (6) surface drying; (7) packaging: the fresh-cut yam is dried on the surface and packaged in a 0.015 mm thick polyethylene film bag with spontaneous atmosphere control; (8) refrigeration: storing in a cold storage at 0-4°C. This technology uses acidic electrolyzed water combined with nano-chitosan coating, which can effectively inhibit the browning of fresh yam. However, this technology only uses acidic electrolyzed water in the soaking stage of the early treatment. The technical problem to be solved by using acidic electrolyzed water is to inhibit the browning of fresh yam. There has been no report on cooking purple yam in acidic electrolyzed water and using it to solve the protection and sterilization of anthocyanins. Summary of the invention

[0005] In view of the above problems, the present invention provides a high-anthocyanin purple yam slice with a simple process, an anthocyanin retention rate of more than 77.76% and a total colony count of 2.47±0.016lgCFU / g after a storage period of 21 days, and can effectively extend the shelf life, and a preparation method thereof.

[0006] To achieve the purpose of the present invention, the technical solution adopted by the present invention is:

[0007] A high-anthocyanin purple yam slice is obtained by peeling the purple yam, washing it with clean water, and then slicing it, boiling, protecting its color, vacuum packaging and sterilizing it; the boiling process is to put the purple yam slices into a normal pressure boiling container, add prepared acidic electrolyzed water to cover the purple yam slices, and boil them for 10 to 30 minutes at a temperature of 60 to 80 DEG C; the acidic electrolyzed water is prepared by electrolysis of dilute hydrochloric acid solution and sodium chloride solution, and has an effective chlorine concentration ACC of 60 to 90 ppm, a pH of 2.5 to 4.0, and an oxidation-reduction potential ORP of 950 to 1200 mV.

[0008] To further achieve the purpose of the present invention, preferably, the purple yam has no insect eyes and no damage.

[0009] Preferably, the cooking temperature is 60-70° C. and the cooking time is 10-20 minutes.

[0010] Preferably, the slicing is to cut the purple yam into slices with a thickness of 1 to 2 cm.

[0011] Preferably, the color protection is performed by soaking the cooked purple yam slices in a prepared citric acid color protection agent.

[0012] Preferably, the mass concentration of the citric acid color preservative is 0.4-0.6%, and the soaking time is 20-40 minutes.

[0013] Preferably, the vacuum packaging adopts a vacuum packaging machine to vacuum pack the color-protected purple yam slices in a cooking bag according to GB9683-1988 "Hygiene Standard for Composite Food Packaging Bags".

[0014] Preferably, the sterilization is to pasteurize the packaged purple yam slices and then store them.

[0015] Preferably, the pasteurization temperature is 80-85° C. and the time is 10-15 minutes.

[0016] The preparation method of the high-anthocyanin purple yam tablets comprises the following steps:

[0017] (1) Pretreatment: Select purple yam without wormholes and damage, peel it, and wash it with clean water;

[0018] (2) Slicing;

[0019] (3) Cooking: Put the sliced ​​purple yam into a normal pressure cooking container, add the prepared acidic electrolyzed water to cover the purple yam slices, and cook at a temperature of 60-80° C. for 10-30 minutes; the acidic electrolyzed water is prepared by electrolysis of dilute hydrochloric acid solution and sodium chloride solution, with an effective chlorine concentration ACC of 60-90 ppm, a pH of 2.5-4.0, and an oxidation-reduction potential ORP of 950-1200 mV;

[0020] (4) Color protection: Soak the cooked purple yam slices in the prepared citric acid color protection agent;

[0021] (5) Vacuum packaging;

[0022] (6) Sterilization.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1) The present invention is the first to cook purple yam with acidic electrolyzed water, strictly controlling the effective chlorine concentration ACC of the acidic electrolyzed water to 60-90ppm, the pH to 2.5-4.0, and the oxidation-reduction potential ORP to 950-1200mV, so that the cooking temperature can be controlled at 60-80°C. The prepared purple yam slices have an anthocyanin retention rate of more than 77.76% after a storage period of 21 days, and a total colony count of 2.47±0.016lgCFU / g, which is much better than the treatment effect of the prior art.

[0025] 2) The present invention provides a suitable acidic environment (pH 2.5-4.0) to maintain anthocyanidins in a stable yellow yl cation form, while reducing the loss of anthocyanidins due to high temperature. Acidic electrolyzed water can effectively kill bacteria on the surface of purple yam slices. The addition of acidic electrolyzed water can reduce the processing and sterilization temperature of purple yam slices, effectively protecting the anthocyanidins therein. At the same time, acidic electrolyzed water combined with pasteurization can effectively inhibit the growth of microorganisms during the storage period of the product, extending the shelf life of purple yam slices.

[0026] 3) Compared with the traditional high-temperature processing technology, the preparation method of the present invention can effectively reduce the loss of anthocyanins caused by high temperature, and uses food-grade raw material citric acid for color protection, effectively avoiding the residual SO2 component in the traditional method. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Graph showing changes in anthocyanin retention in purple yam slices during storage in each case.

[0028] Figure 2 The graph shows the changes in the total colony count of purple yam slices during the storage period in each case. DETAILED DESCRIPTION

[0029] In order to more clearly illustrate the technical solutions in the embodiments and comparative examples of the present invention, various embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. The embodiments should not be regarded as limiting the scope of protection of the present invention, but should be understood as an elaboration of certain aspects, characteristics and implementation plans of the present invention.

[0030] Example 1

[0031] (1) Pretreatment: Select purple yam without wormholes, damage and tubers of similar size, peel them and wash them with clean water;

[0032] (2) Slicing: Slice the pre-treated purple yam into slices with a thickness of about 1 to 2 cm;

[0033] (3) Cooking: Put the purple yam slices into a normal pressure cooking container, add acidic electrolyzed water (pH = 2.5, effective chlorine concentration ACC is 90ppm, oxidation-reduction potential ORP is 1200mV) to cover the purple yam slices; the cooking temperature is 70°C, and the cooking time is 15min;

[0034] (4) Color protection: Soak the cooked purple yam slices in the prepared 0.5% citric acid color protection agent for 30 minutes;

[0035] (5) Vacuum packaging: vacuum pack the purple yam slices after color protection using a vacuum packaging machine and a retort bag that complies with GB9683-1988 “Sanitary Standards for Composite Food Packaging Bags”;

[0036] (6) Sterilization: The packaged purple yam slices were pasteurized at 80°C for 15 min, and stored at 4°C for 21 days. Samples were taken every 3 days to determine the total colony count and anthocyanin retention.

[0037] Example 2

[0038] (1) Pretreatment: Select purple yam without wormholes, damage and tubers of similar size, peel them and wash them with clean water;

[0039] (2) Slicing: Slice the pre-treated purple yam into slices with a thickness of about 1 to 2 cm;

[0040] (3) Cooking: Put the purple yam slices into a normal pressure cooking container, add acidic electrolyzed water (pH = 4.0, effective chlorine concentration ACC is 60ppm, oxidation-reduction potential ORP is 950mV) to cover the purple yam slices, cook at 80°C, and cook for 10 minutes;

[0041] (4) Color protection: Soak the cooked purple yam slices in the prepared 0.6% citric acid color protection agent for 30 minutes;

[0042] (5) Vacuum packaging: vacuum pack the purple yam slices after color protection using a vacuum packaging machine and a retort bag that complies with GB9683-1988 “Sanitary Standards for Composite Food Packaging Bags”;

[0043] (6) Sterilization: The packaged purple yam slices were pasteurized at 85°C for 10 min, and stored at 4°C for 21 days. Samples were taken every 3 days to determine the total colony count and anthocyanin retention.

[0044] Example 3

[0045] (1) Pretreatment: Select purple yam without wormholes, damage and tubers of similar size, peel them and wash them with clean water;

[0046] (2) Slicing: Slice the pre-treated purple yam into slices with a thickness of about 1 to 2 cm;

[0047] (3) Cooking: Put the purple yam slices into a normal pressure cooking container, add acidic electrolyzed water (pH = 3.0, effective chlorine concentration ACC is 75ppm, oxidation-reduction potential ORP is 1100mV) to cover the purple yam slices, cook at 60°C, and cook for 15 minutes;

[0048] (4) Color protection: Soak the cooked purple yam slices in the prepared 0.4% citric acid color protection agent for 30 minutes;

[0049] (5) Vacuum packaging: vacuum pack the purple yam slices after color protection using a vacuum packaging machine and a retort bag that complies with GB9683-1988 “Sanitary Standards for Composite Food Packaging Bags”;

[0050] (6) Sterilization: The packaged purple yam slices were pasteurized at 85°C for 15 min, and stored at 4°C for 21 days. Samples were taken every 3 days to determine the total colony count and anthocyanin retention.

[0051] Comparative Example 1

[0052] (1) Pretreatment: Select purple yam without wormholes, damage and tubers of similar size, peel them and wash them with clean water;

[0053] (2) Slicing: Slice the pre-treated purple yam into slices with a thickness of about 1 to 2 cm;

[0054] (3) Cooking: Put the purple yam slices into a normal pressure cooking container, add water to cover the purple yam slices, cook at 70°C, and cook for 15 minutes;

[0055] (4) Color protection: Soak the cooked purple yam slices in the prepared 0.5% citric acid color protection agent for 30 minutes;

[0056] (5) Vacuum packaging: vacuum pack the purple yam slices after color protection using a vacuum packaging machine and a retort bag that complies with GB9683-1988 “Sanitary Standards for Composite Food Packaging Bags”;

[0057] (6) Sterilization: The packaged purple yam slices were pasteurized at 80°C for 15 min, and stored at 4°C for 21 days. Samples were taken every 3 days to determine the total colony count and anthocyanin retention.

[0058] Measurement indicators

[0059] (1) Determination of anthocyanin retention: pH differential method was used for determination.

[0060] (2) Determination of total colony count: According to the national food safety standard GB4789.2-2022 "Determination of total colony count in food microbiological examination", the total colony count of the purple yam samples in Examples 1, 2, 3 and Comparative Example 1 during storage was determined.

[0061] Anthocyanin retention analysis

[0062] Anthocyanin is an active substance with antioxidant activity in purple yam. A high anthocyanin retention indicates good antioxidant activity of the product. However, the high temperature in traditional processing causes a huge loss of anthocyanin in purple yam. The present invention reduces the loss of anthocyanin in the processing process by using acidic electrolyzed water instead of water for boiling and using citric acid color preservative to adjust the pH value. Figure 1 It can be seen that in Examples 1, 2, and 3, the anthocyanin retention rate of the purple yam slices during storage is very slow, using the preparation process of the present invention in combination with acidic electrolyzed water of different parameters. The initial anthocyanin retention rate of the purple yam slices in Comparative Example 1, which is basically similar to the technical measures of the present invention, except that acidic electrolyzed water is not used in the cooking step (3), is much lower than that of Examples 1-3 after the acidic electrolyzed water treatment, and the anthocyanin reduction rate during storage is faster. For example, in Example 1, the sample was cooked with acidic electrolyzed water of pH=2.5, and its anthocyanin retention rate after the storage period was 18.91±0.021 mg / 100g, with a retention rate of up to 80.36%, which is even better than that of Examples 2 and 3, which were treated with acidic electrolyzed water of pH=3.0 and 4.0. The anthocyanin retention amount of the sample in Example 3 after the storage period is 17.90±0.016 mg / 100 g, and the retention rate is 77.76%. The anthocyanin retention amount of the sample in Example 2 after the storage period is 17.55±0.023 mg / 100 g, and the retention rate is 77.41%. It may be that the present invention uses acidic electrolyzed water instead of clear water to cook the purple yam slices, and improves the stability of anthocyanins by adjusting the pH, and shows pH dependence. The lower the pH of the acidic electrolyzed water, the better the retention effect of anthocyanins. This provides a certain theoretical basis for solving the problem of anthocyanin loss in the processing of purple yam products. Moreover, it can be seen from the examples that the use of acidic electrolyzed water in the technical measures of the present invention during cooking can also reduce the cooking temperature, which is also very useful for avoiding the loss of anthocyanins.

[0063] Total colony count analysis

[0064] The total number of colonies reflects the microbial contamination and is one of the indicators for determining food quality. Figure 2It can be seen that the total colony count of Comparative Example 1 (without acidic electrolyzed water treatment) showed a rapid growth trend during storage, reaching 4.61±0.014logCFU / g on the 21st day. The total colony counts of Examples 1, 2, and 3 increased slightly with the increase in storage time, but the total colony counts of the three groups of examples were significantly lower than that of Comparative Example 1 (p<0.05) throughout the storage period. After the storage, the total colony count of Example 3 only increased by 2.2±0.017logCFU / g. It is proved that the bactericidal effect of acidic electrolyzed water combined with pasteurization on purple yam slices is better than that of pasteurization alone, and effectively inhibits the growth of microorganisms during storage. Studies have shown that the active ingredients of acidic electrolyzed water can penetrate the microbial cell membrane and destroy proteins involved in important metabolic pathways, thereby killing bacteria. According to the provisions of GB19295-2021 "National Food Safety Standard for Quick-frozen Noodles, Rice and Prepared Foods", the limit of the total colony count is ≤5logCFU / g. The contents of Examples 1, 2 and 3 did not exceed the limit during the storage period, which proves that the preparation method of the present invention can effectively extend the shelf life of purple yam slices.

[0065] In summary, compared with traditional processing, the present invention uses acidic electrolyzed water instead of clear water to cook purple yam slices for the first time, which can provide an acidic environment to stabilize anthocyanins while reducing the processing temperature of purple yam slices, effectively retaining anthocyanins during processing. In addition, the acidic electrolyzed water cooking method can effectively inhibit the growth of the total bacterial count of purple yam slices during storage, effectively extend their shelf life, and is of great significance to the high added value of purple yam products.

[0066] The above descriptions are only some embodiments of the present invention. Without violating the principles of the present invention and without departing from the concept of the present invention, several modifications and improvements can be made, which all belong to the protection scope of the present invention. The storage temperature used in the present invention is 4°C, and the storage period can reach more than 21 days, and it can be circulated in the market as a pre-prepared dish. If long-term storage is desired, a storage temperature of -18°C can be used, which can more effectively inhibit the growth of microorganisms, so that it can be used for filling preparation, etc.

Claims

1. A high-anthocyanin purple yam slice, which is obtained by peeling the purple yam, washing it with clean water, and then slicing it, cooking it, protecting its color, vacuum packaging it, and sterilizing it; characterized in that: The cooking process is to put the purple yam slices into a normal pressure cooking container, add the prepared acidic electrolyzed water to cover the purple yam slices, and cook for 10 to 30 minutes at a temperature of 60 to 80°C; the acidic electrolyzed water is prepared by electrolysis of dilute hydrochloric acid solution and sodium chloride solution, and the effective chlorine concentration ACC is 60 to 90 ppm, the pH is 2.5 to 4.0, and the oxidation-reduction potential ORP is 950 to 1200 mV; the sterilization process is to pasteurize the packaged purple yam slices and then store them.

2. The high anthocyanin purple yam slice according to claim 1, characterized in that The purple yam has no worm eyes and no damage.

3. The high anthocyanin purple yam slices according to claim 1, characterized in that The cooking temperature is 60-70° C., and the cooking time is 10-20 minutes.

4. The high anthocyanin purple yam slices according to claim 1, characterized in that The slicing process is to cut the purple yam into slices with a thickness of 1 to 2 cm.

5. The high anthocyanin purple yam slices according to claim 1, characterized in that: The color protection method comprises the following steps: the cooked purple yam slices are put into a prepared citric acid color protection agent and soaked.

6. The high anthocyanin purple yam slices according to claim 5, characterized in that: The mass concentration of the citric acid color preservative is 0.4-0.6%, and the soaking time is 20-40 minutes.

7. The high anthocyanin purple yam slices according to claim 1, characterized in that: The vacuum packaging adopts a vacuum packaging machine to vacuum pack the color-protected purple yam slices in a cooking bag according to GB 9683-1988 "Hygiene Standard for Composite Food Packaging Bags".

8. The high anthocyanin purple yam slices according to claim 1, characterized in that: The pasteurization temperature is 80-85°C and the time is 10-15 minutes.

9. The method for preparing the high anthocyanin purple yam tablets according to any one of claims 1 to 8, characterized in that The steps include: (1) Pretreatment: Select purple yam without wormholes and damage, peel it, and wash it with clean water; (2) Slicing; (3) Cooking: Put the sliced ​​purple yam into a normal pressure cooking container, add the prepared acidic electrolyzed water to cover the purple yam slices, and cook at a temperature of 60-80° C. for 10-30 minutes; the acidic electrolyzed water is prepared by electrolysis of dilute hydrochloric acid solution and sodium chloride solution, with an effective chlorine concentration ACC of 60-90 ppm, a pH of 2.5-4.0, and an oxidation-reduction potential ORP of 950-1200 mV; (4) Color protection: Soak the cooked purple yam slices in the prepared citric acid color protection agent; (5) Vacuum packaging; (6) Sterilization.

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