CN114947118B - Fermented dried date cheese and preparation method thereof - Google Patents

Abstract

The invention discloses a new fermented product, dried date cheese, and a preparation method thereof. The new product directly uses fresh dates as raw materials. After pretreatment, it is inoculated with suspension bacteria according to a certain inoculation amount and fermented. After baking and sterilization, a brand new product is finally obtained. Fermented products, the preparation process of dried jujube cheese is simple and easy to operate, convenient for large-scale production, and greatly reduces production costs. The product has a higher moisture content than dry jujubes, unique flavor, and ruddy color. It solves the problem of the quality of dried jujube products caused by the existing processing technology. Technical problems such as color browning and flavor deterioration are not good, and the quality control of the processing process using fresh dates as raw materials has been achieved, and the sugar content of the product has been reduced through fermentation treatment while forming a special flavor of the product. When using yeast - Lactic acid bacteria are fermented according to the mixed bacteria with a mass ratio of 1:1. The total sugar content during the fermentation process is at least 25.73% and the total phenolic content is at the highest 47.83 mg/g. The date cheese dried provided by the invention is a brand-new snack food and more In line with the health concept.

Description

A kind of fermented date cheese and preparation method thereof

Technical field

The invention relates to the field of food processing, and in particular to a new fermented date cheese product and a preparation method thereof.

technical background

Zizyphus jujube Mill. is the fruit of the Zizyphus Mill. plant in the Rhamnaceae family. Red dates are a unique economic fruit in China, with a cultivation area of about 100hm2 and an annual output of about 4 million tons. The current main processing method of fresh red dates in my country is drying, and 70-80% of exported red dates are dried products. At present, traditional red date processed products on the Chinese market include dried products such as date puree, date powder, date preserves, black dates, date slices, dates with nuts, functional products such as date polysaccharides, pigments, dietary fiber and other products, as well as soft drink date wine. , date vinegar, date juice, date cheese and other products. These processed products use dried dates as raw materials for secondary processing. The raw materials of dried dates are mainly natural drying and artificial drying. Studies have shown that the aroma components of dried dates change. The changes in type and content are more obvious, but the contents of pectin, total acid, reducing sugar, and total sugar have all decreased; and the influence of the processing environment during the drying process has led to varying degrees of poor quality, such as browning of color, Loss of nutrients, deterioration of flavor (bitter and spicy taste), etc. It can be seen that the quality of dried dates directly affects the quality of finished products, resulting in less room for quality improvement and innovation of processed products, resulting in the market share of processed red date products, especially as snack foods. Rates are limited.

In order to enrich the types of jujube processed products and innovate products, it is urgent to develop more directly processed fresh jujube products, which not only reduces the existing secondary processing costs, but also further improves the browning and nutritional components existing in the deep processing of existing dried jujubes. Problems with loss, loss of flavor and high sugar content.

Contents of the invention

In view of the technical status quo of existing deep-processed red dates products that require secondary processing, complex processing techniques and high costs, and existing deep-processed dried dates products that suffer from browning, loss of nutrients, deterioration of flavor and high sugar content. The present invention aims to provide a fermented date cheese dried product and a preparation method thereof. The new product is made by directly using fresh dates as raw materials, pre-processing and inoculating suspension fermentation according to a certain inoculation amount, and finally obtaining a brand-new product through baking and sterilization. Fermented product, the preparation process of this dried jujube cheese is simple and easy to operate, convenient for large-scale production, and greatly reduces production costs. The product has a higher moisture content than dry jujubes, unique flavor, and ruddy color. It solves the problem of the quality of dried jujube products caused by the existing processing technology. Technical problems such as color browning and flavor deterioration are not good, and the quality control of the processing process using fresh dates as raw materials has been achieved, and the sugar content of the product has been reduced through fermentation treatment while forming a special flavor of the product. When using yeast - Lactic acid bacteria are fermented according to the mixed bacteria with a mass ratio of 1:1. The total sugar content during the fermentation process is at least 25.73% and the total phenolic content is at the highest 47.83 mg/g. The date cheese provided by the invention is a brand-new snack food and More in line with the health concept.

The invention provides a fermented date cheese, which is obtained by inoculating fresh date fruits with mixed bacteria, fermentation and drying.

In the fermented jujube dried cheese of the present invention, the jujube fruit is any one of wild jujube, jujube, and golden jujube.

In the fermented dried date cheese of the present invention, the dried date cheese is prepared by the following steps: after the fresh date fruit is washed and pre-treated, citric acid with a concentration of 0.5% is added for color protection treatment for 10 minutes; the processed date fruit is packed into 15× 25cm vacuum bag, inoculate 4% of the weight of the jujube fruit with a suspension, seal, and ferment at 37±1℃ for 60-84 hours; bake the fermented jujube fruit at 55-60℃ for 10-12 hours until the moisture content is 20 %, vacuum package and sterilize in a normal pressure water bath at 80°C for 20 minutes to obtain a new product, dried date cheese.

In the preparation of fermented jujube dried cheese provided by the invention, the fresh jujube pretreatment method is any one of peeling and cored without puncturing, non-peeling, cored and punctured, and non-peeling, cored and punctured.

In the preparation of fermented date cheese provided by the present invention, the fermentation method is any one of natural fermentation, yeast fermentation, mixed bacteria fermentation, and lactic acid bacteria fermentation.

In the preparation of fermented jujube dried cheese provided by the invention, fresh jujubes without peeling, pitting or puncturing are used for pretreatment, and mixed bacteria are used for fermentation. The mixed bacteria suspension is obtained according to the following steps: yeast: lactic acid bacteria according to the quality Dissolve in warm water at 30±0.5℃ with a ratio of 1:1 to make a suspension with a concentration of 20%, and activate it for 30 minutes.

After adopting the above technical solution, the beneficial effects obtained by the present invention are as follows:

(1) The preparation process of the new fermented jujube cheese dried product obtained by the method provided by the invention is simple and easy to operate, convenient for large-scale production, and greatly reduces the production cost. The product has a higher moisture content than dry jujubes, unique flavor, and ruddy color, and solves the problem It solves the technical problems of poor quality, browning of color and deterioration of flavor caused by the existing processing technology of dried date fruit products.

(2) The new fermented jujube cheese product provided by the present invention has comprehensive nutrition. The total sugar content is lower than that of fresh fruit, but the reducing sugar content is increased, the total acid content is increased, and the total phenolic content is increased. The preparation of the new product solves the problem of existing dried jujube products. Due to the problem of sweet taste caused by excessive sugar content and insufficient acid content, the total acid content of samples using natural fermentation, yeast fermentation, mixed bacteria fermentation, and lactic acid bacteria fermentation increased by 20%, 18.83%, and 21.67% respectively compared with fresh dates. %, 42.50%; the total sugar content decreased by 29.18%, 34.44%, 35.33%, and 25.17% respectively compared with fresh dates; the reducing sugar content at the end of fermentation was 3.63%, 4.32%, 3.20%, and 3.94% respectively.

(3) The new fermented date cheese product provided by the present invention is fermented by mixed bacteria. When the yeast-lactic acid bacteria are inoculated according to the mass ratio of 1:1, the total sugar content during the fermentation process is the lowest 25.73%, and the total phenol content is the highest 47.83 mg/g,.

Instructions with pictures

Figure 1 shows the changes in the total phenolic content of dried date cheese during the fermentation process with different fresh fruit pretreatment methods.

Figure 2 shows the changes in the total acid content of dried date cheese with different fresh fruit pretreatment methods during the fermentation process.

Figure 3 shows the changes in the total sugar content of dried date cheese during the fermentation process with different fresh fruit pretreatment methods.

Figure 4 is a diagram showing the changes in reducing sugar content of dried date cheese with different fresh fruit pretreatment methods during the fermentation process.

Figure 5 shows the changes in the total phenolic content of dried date cheese during the fermentation process using different fermentation methods.

Figure 6 shows the changes in the total acid content of dried date cheese during the fermentation process using different fermentation methods.

Figure 7 is a graph showing changes in the total sugar content of dried date cheese during the fermentation process using different fermentation methods.

Figure 8 is a diagram showing the changes in reducing sugar content of dried date cheese during the fermentation process using different fermentation methods.

Detailed ways

The present invention will be described below with reference to examples. However, the present invention is not limited to the following examples. All raw and auxiliary materials selected in the present invention, as well as the selected bacterial culture methods are well known in the art. The % mentioned in the present invention are all weight percentages, unless otherwise specified.

Example 1: Preparation of dried date cheese

This embodiment provides a new fermented product, dried date cheese, which is prepared by the following steps: after washing and pre-processing the fresh date fruit, add citric acid with a concentration of 0.5% for color protection treatment for 10 minutes; pack the processed date fruit into Put it into a 15×25cm vacuum bag, inoculate 4% of the weight of the jujube fruit with a suspension, seal it, and ferment it at 37±1℃ for 60-84 hours; bake the fermented jujube fruit at 55-60℃ for 10-12 hours until the moisture content The content is 20%, vacuum-packed and sterilized in a normal pressure water bath at 80°C for 20 minutes to obtain a new product of dried date cheese.

Wherein, the jujube fruit is any one of jujube, gray jujube, and Hami jujube, and the pretreatment method of the fresh jujube is peeling and pitting without puncturing, peeling and pitting without puncturing, and peeling without peeling. The core does not puncture any one; the fermentation method is any one of natural fermentation, yeast fermentation, mixed bacteria fermentation, and lactic acid bacteria fermentation.

Example 2: Preparation of dried date cheese

On the basis of Example 1, this embodiment provides a method for preparing a new fermented jujube cheese product, in which the jujube fruit is jujube, and the fresh jujube pretreatment method is no peeling, core removal, and no punctures; the fermentation method is: Mixed bacterial fermentation; mixed bacterial suspension is obtained according to the following steps: yeast: lactic acid bacteria are dissolved in warm water at 30±0.5°C according to a mass ratio of 1:1 to prepare a suspension with a concentration of 20%, and activated for 30 minutes.

Example 3: Preparation of dried date cheese

On the basis of Example 1, this embodiment provides a method for preparing a new fermented jujube cheese product, in which the jujube fruit is Hami jujube, and the fresh jujube pretreatment method is to peel, remove and core without puncturing; the fermentation method is: Natural fermentation at a temperature of 37±1°C.

Example 4: Preparation of dried date cheese

On the basis of Example 1, this embodiment provides a method for preparing a new fermented jujube cheese product, in which the jujube fruit is gray jujube, the fresh jujube pretreatment method is non-peeling, pitting and punctures; the fermentation method is yeast For yeast fermentation, the yeast suspension is prepared using the following steps: Dissolve 60g of yeast powder in 300mL of 30±0.5°C warm water to make a suspension with a concentration of 20%, and activate it for 30 minutes to obtain it.

Example 5: Preparation of dried date cheese

On the basis of Example 1, this embodiment provides a method for preparing a new fermented jujube cheese product, in which the jujube fruit is jujube, and the fresh jujube pretreatment method is no peeling, core removal, and no punctures; the fermentation method is: For lactic acid bacteria fermentation, the lactic acid bacteria suspension is prepared using the following steps: Dissolve 60g of lactic acid bacteria powder in 300 mL of 30±0.5°C warm water to prepare a suspension with a concentration of 20%, and activate it for 30 minutes.

Example 6: Preparation of dried date cheese

On the basis of Example 1, this embodiment provides a method for preparing a new fermented jujube cheese product, in which the jujube fruit is jujube, the fresh jujube pretreatment method is not peeling, pitting and puncturing; the fermentation method is mixing Bacteria fermentation, the mixed bacterial suspension is prepared using the following steps: Dissolve 30g each of lactic acid bacteria powder and yeast powder in 300mL of 30±0.5°C warm water to prepare a suspension with a concentration of 20%, and activate it for 30 minutes.

Example 7: Optimization of the preparation process of dried date cheese

In this example, on the basis of Examples 1-6, the preparation process of the new fermented date cheese dried product is optimized, and the effect of pretreatment method and fermentation method on the total phenol, total acid, total sugar and reducing sugar content during the fermentation process of the product is investigated. Impact.

1. Effect of fresh jujube pretreatment methods on product performance

(1)Test plan

Raw materials: Fresh jujubes: collected from Aksu in September 2020, all red, crisp and ripe, with uniform color, no pests and diseases, no mechanical damage, transported to cold storage for later use. Bifidobacterium lactobacillus powder: Chuanxiu Co., Ltd.; Yeast powder: Angel Company; Fulinol, Solebao Company; L(+)-ascorbic acid standard (purity ≥99%) Sinopharm Chemical Reagent Co., Ltd., glucose , concentrated sulfuric acid, ethanol, copper sulfate, potassium sodium tartrate, sodium hydroxide, potassium ferrocyanide, zinc acetate, methyl red, phenolphthalein, hydrochloric acid, glacial acetic acid, potassium hydrogen phthalate (all analytical grade).

Fresh jujube pretreatment method: After cleaning the fresh jujube, peel and core without puncture (process one), peel without peel and core without puncture (process two), and peel without peel and core without puncture (process three) Three kinds of preprocessing. Alkali solution peeling: Set the concentrations as: 2%, 3%, 4%, 5% respectively. Select the lye solution concentration of 3% according to the peeling effect. Put the jujube fruits with different pretreatments into a 15×25cm vacuum bag, inject 4% lactic acid bacteria suspension (containing 20% lactic acid bacteria after activation) according to the weight of the jujube fruits, use vacuum extraction and sealing, and ferment at 37±1℃ 84h, got the finished product. During this period, samples were taken every 12 hours, and the reducing sugar, total phenols, total acid, total sugar and other indicators of the product were analyzed to select the most suitable pretreatment.

(2) Analysis of test results

Table 1: Some quality indicators of fresh dates

Table 1 shows the determination of the total acid, total phenols, total sugar and reducing sugar content of fresh dates in this experiment. As a control, the changes in the nutritional content of the product after fermentation with different pretreatment methods are examined. The specific results are shown in Figures 1-4. .

Figure 1 is a graph showing changes in the total phenolic content of dried date cheese during the fermentation process with different fresh fruit pretreatment methods. It can be seen from the data in Figure 1 that when three different pretreatment methods were used for fermentation, the changes in the total phenolic content of the product during the fermentation process showed an overall trend of first increasing and then decreasing. Among them, after pretreatment, the total phenolic content of dried date cheese showed a trend of first increasing and then decreasing during the fermentation process. The total difference reached 35.48mg/g, and the total phenolic content reached the maximum value of 58.97mg/g at 48h. The changes in total phenolic content tended to be stable during 60-84h; when pretreatment was used in the second treatment, the total phenolic content of dried date cheese reached the maximum value of 64.30mg/g at 48h. Compared with treatment one, the total phenolic content increased at a slower rate. Fast, reaching the second peak at 12h; when using the pretreatment method for three hours, the total phenolic content of dried date cheese was significantly higher than the other two pretreatment methods. The total phenol also reached the peak at 48h, which was 112.20 mg/g, and the rising rate was faster than that of the other two pretreatment methods. Processing two is faster. It showed that the total phenolic content of fresh dates increased after lactic acid fermentation within a certain period of time, and the antioxidant capacity was enhanced. Among the three pretreatments, treatment three was significantly higher than the other two groups (p<0.05).

Figure 2 is a graph showing changes in the total acid content of dried date cheese during the fermentation process with different fresh fruit pretreatment methods. Total acid is an important indicator of changes in fruit quality, as well as an important indicator for evaluating fermentation rate and product quality. It can be seen from the data in Figure 2 that the total acid content of products fermented by different pretreatment methods showed an overall trend of first increasing and then decreasing during the entire fermentation process. Among them, the fermentation times for total acid to reach the peak in treatments one, two and three were 36h, 12h and 48h respectively, indicating that among the fresh jujube pretreatment methods, treatment two is more conducive to increasing the lactic acid fermentation speed of jujube fruits. At the end of fermentation , the total acid content in each treatment was lower than that of fresh dates (0.6%). This may be due to the fact that when lactic acid bacteria are introduced for lactic acid fermentation, the heterolactic acid bacteria naturally carried by the jujube fruit also undergo heteroformal lactic acid fermentation. In addition to lactic acid, ethanol is also produced. , acetic acid and carbon dioxide and other products, and then an esterification reaction occurs, consuming part of the acid. The total acid content of the fermentation products of the three pretreatment methods decreased by 27.74%, 42.97%, and 45.84% respectively by the end of 84 hours of fermentation. At this time, the total acid content was 0.41%, 0.30%, and 0.46% respectively; the three treatments were compared with treatment one and Treatment 2 has significant differences (p<0.05).

Figure 3 is a graph showing changes in the total sugar content of dried date cheese during the fermentation process with different fresh fruit pretreatment methods. From the data in Figure 3, it can be seen that at 12 hours of fermentation, the changes in total sugar content in each group were treated with treatment one, treatment two, and treatment three. The total sugar content was significantly different from the initial value (P<0.05). At this time, the sample decreased by 20.19%, 11.05%, and 7.12% respectively compared with fresh dates. Before fermentation for 48 hours, the total sugar content in treatment 1 was at the lowest level. It shows that the fermentation speed is the fastest after peeling; from 48h to 72h of fermentation, the reduction rate of total sugar content in each group was not obvious, which decreased by 17.23%, 24.46%, and 29.05% respectively; at 84h of fermentation, the total sugar content of the treatment increased by 5.45% , this may be due to the combined impact of the decrease in the total sugar concentration in the fermentation broth and the production of sugar-containing metabolites due to the growth, reproduction and metabolism of microorganisms. In summary, the total sugar content of the samples showed an overall downward trend during the fermentation period; at the end of the fermentation, among the three treatments, treatment two was significantly higher than the other two groups (P<0.05).

Figure 4 is a graph showing the changes in the reducing sugar content of dried dates cheese with different fresh fruit pretreatment methods during the fermentation process. From the data in Figure 4, it can be seen that among the three different pretreatments, except for treatment one at 36h, the reducing sugar content of the other products is at The fermentation process was on an upward trend from 12h to 72h, and the rising rates of treatments two and three were 83.19% and 13.75% respectively; at the same time, the differences among the three treatments were significant (p<0.05). When the fermentation time is 12 hours, there is no significant difference in the rising rate of reducing sugar in the samples with three different pretreatment methods. Compared with fresh dates, the rising rates are 32.77%, 33.42%, and 14.93% respectively; when the fermentation time is 84 hours, the rising rates of reducing sugars in the samples of three different pretreatment methods are 32.77%, 33.42%, and 14.93% respectively. The reducing sugars in treatment three showed a downward trend, and the decreasing rates were 8.07%, 19.45%, and 4.20% respectively. At this time, the reducing sugar content in treatment three was the highest, which was 4.13g/100g. Comprehensive consideration, at the end of fermentation in treatment three, the total acid was 0.46%, the total sugar was 25.73%, and the sugar-acid ratio was 55.93. The product had the best flavor and the fruit shape was best maintained. Therefore, treatment three (no peeling, corering, and no punctures) was selected. ) is the better preprocessing.

2. The impact of different fermentation methods on product performance

(1)Test plan

Raw materials: Fresh jujubes: collected from Aksu in September 2020, all red, crisp and ripe, with uniform color, no pests and diseases, no mechanical damage, transported to cold storage for later use. Bifidobacterium lactobacillus powder: Chuanxiu Co., Ltd.; Yeast powder: Angel Company; Fulinol, Solebao Company; L(+)-ascorbic acid standard (purity ≥99%) Sinopharm Chemical Reagent Co., Ltd., glucose , concentrated sulfuric acid, ethanol, copper sulfate, potassium sodium tartrate, sodium hydroxide, potassium ferrocyanide, zinc acetate, methyl red, phenolphthalein, hydrochloric acid, glacial acetic acid, potassium hydrogen phthalate (all analytical grade).

Pre-processing method for fresh dates: no peeling, no pitting, no punching.

Fermentation method:

Natural fermentation: Take 2kg of fresh jujubes, wash them, select the optimal pre-treatment, seal them in a 15×25cm bag under vacuum, and ferment at a temperature of 37±1°C. During the fermentation process, samples are taken regularly for total phenols, total acids, and total For the determination of sugar and reducing sugar content, the total fermentation time was determined to be 84 hours based on the preliminary test. The sampling time points are: 12h, 24h, 36h, 48h, 60h, 72h and 84h.

Lactic acid bacteria fermentation: Dissolve 60g of lactic acid bacteria powder in 300mL of 30±0.5°C warm water to make a 20% suspension, activate it for 30 minutes, and set aside. Take 2kg of fresh jujube, put it into a vacuum bag after pretreatment, inject 4% of the weight of jujube fruit suspension, vacuum and seal; ferment at a temperature of 37±1°C. During the fermentation process, samples are taken regularly for total phenolics. , the determination of total acid, total sugar and reducing sugar content, the total fermentation time was determined to be 84h based on the preliminary test. The sampling time points are: 12h, 24h, 36h, 48h, 60h, 72h and 84h.

Yeast fermentation: Dissolve 60g of yeast powder in 300mL of 30±0.5°C warm water to make a 20% suspension, activate for 30 minutes, and set aside. Take 2kg of fresh jujube, put it into a vacuum bag after pretreatment, inject 4% of the weight of jujube fruit suspension, vacuum and seal; ferment at a temperature of 37±1°C. During the fermentation process, samples are taken regularly for total phenolics. , the content of total acid, total sugar and reducing sugar was determined, and the total fermentation time was determined to be 84h based on the preliminary test. The sampling time points are: 12h, 24h, 36h, 48h, 60h, 72h and 84h.

Mixed bacteria fermentation: Dissolve 30g each of lactic acid bacteria powder and yeast powder in 300mL 30±0.5℃ warm water to make a 20% suspension, activate it for 30 minutes, and set aside. Take 2kg of fresh jujubes, put them into vacuum bags after pretreatment, inject 2% of jujube fruit weight (4% in total) suspension bacteria respectively, vacuum and seal; ferment at 37±1°C, fermentation process Samples were taken regularly to measure the contents of total phenols, total acids, total sugars and reducing sugars. Based on the preliminary test, the total fermentation time was determined to be 84 hours. The sampling time points are: 12h, 24h, 36h, 48h, 60h, 72h and 84h.

(2)Test results and analysis

Phenolics are a general term for a class of polyhydroxy compounds that exist in fruits, vegetables and other plants. They are also one of the main substances that reflect the antioxidant capacity of fruits and vegetables. The total phenolic content of fresh jujubes is 49.24mg/g. Figure 5 shows The change diagram of the total phenolic content of dried date cheese in different fermentation methods during the fermentation process. From the data in Figure 5, it can be seen that the total phenolic content of dried date cheese in four different fermentation methods showed two high peaks at 24h and 48h of fermentation. After fermentation for 48 hours, the total phenolic content of the products showed a downward trend. Among them, the total phenolic content of dried date cheese fermented by mixed bacteria was higher than that of the other three fermentation methods (P<0.05). When fermented for 84 hours, natural fermentation, yeast fermentation, The total phenolic contents of dried date cheese obtained from the four fermentation methods of mixed bacteria fermentation and lactic acid bacteria fermentation were 39.02 mg/g, 38.44 mg/g, 47.83 mg/g, and 35.78 mg/g respectively, which were 29.06%, 29.06% lower than that at 48 h of fermentation, respectively. 49.61%, 35.70%, 44.35%, with significant differences (p<0.05). Mixed bacterial fermentation has a significant slowing down rate of decline in the total phenolic content of dried date cheese.

Figure 6 is a graph showing changes in the total acid content of dried date cheese produced in different fermentation methods during the fermentation process. From the data in Figure 6, it can be seen that, except for the total acid content of the natural fermentation sample, which first increased and then decreased with the fermentation process, the other three types of The total acid content of the fermentation method samples showed a trend of decreasing, increasing, and then decreasing. The total acid content of the four fermentation method samples reached the highest value at 48 hours. At this time, the total acid content of natural fermentation, yeast fermentation, mixed bacteria fermentation, and lactic acid bacteria fermentation method The contents were 0.48%, 0.71%, 0.73%, and 0.85%, which increased by 20%, 18.83%, 21.67%, and 42.50% respectively compared with fresh dates; after 48 hours, the total acid content of the four fermentation methods dropped rapidly, and reached 84 hours of fermentation. At the end, the total acid content of natural fermentation, yeast fermentation, mixed bacteria fermentation, and lactic acid bacteria fermentation samples were 0.29%, 0.38%, 0.45%, and 0.46% respectively. Analyzing different fermentation methods and the changing trend of total acid during the fermentation process, it can be seen that natural fermentation fermentation is mainly fermented by bacteria carried by the raw materials themselves. The lactic acid fermentation speed is slow and the acid production is also low. Inoculation of lactic acid bacteria, yeast and mixed Samples fermented by bacteria carry the lactic acid fermentation of the raw materials and are superimposed with the lactic acid produced by the fermentation of the dominant lactic acid bacteria. Samples inoculated with yeast will also produce carbon dioxide during alcoholic fermentation to increase some acidity, so during the fermentation process and the end of fermentation, The order of the total acid content of samples from the four fermentation methods is natural fermentation < yeast fermentation < mixed bacteria fermentation < lactic acid bacteria fermentation. The reason why the total acid content decreased during the fermentation process after 48 hours may be due to the production and consumption of esters in the later stage. Caused by organic acids.

Figure 7 is a graph showing changes in the total sugar content of dried dates and cheese during the fermentation process of different fermentation methods. From the data in Figure 7, it can be seen that the total sugar content of dried dates and cheese in the four fermentation methods gradually decreased during the fermentation process. The natural fermentation samples except for 12h In addition, the residual sugar content in other time periods was at the highest value, which also showed that the natural fermentation speed was slow and the residual sugar was high. The total sugar content at 48 hours was significantly different from the other three groups (P<0.05), with a decrease of 12.28%. At the end of fermentation, the total sugar content of samples from natural fermentation, yeast fermentation, mixed bacteria fermentation, and lactic acid bacteria fermentation was 24.22%, 20.63%, 19.69%, and 23.21% respectively, which were 29.18%, 34.44%, and 35.33% lower than that of fresh dates, respectively. , 25.17%, and the residual sugar content of the sample fermented by mixed bacteria was the lowest. This is mainly because the fermentation of lactic acid and alcohol produces organic acids and consumes part of the sugar in the raw materials.

Figure 8 is a graph showing changes in the reducing sugar content of dried dates fermented by different fermentation methods during the fermentation process. From the data in Figure 8, it can be seen that the reducing sugar content of dried dates fermented by the four fermentation methods showed an increasing trend during the fermentation process. Among them, , the rising trend is obvious before 48 hours of fermentation. At the end of fermentation, the reducing sugar content of the fermentation samples of the four fermentation methods is higher than that of the samples at 12 hours; after 48 hours of fermentation to the end of fermentation, the reducing sugar content of the yeast fermentation sample is the highest, which is 4.32%. Mixed The reducing sugar content of bacterial fermentation samples was the lowest, 3.20%. The rising rates of natural fermentation, mixed bacterial liquid fermentation, and yeast liquid fermentation to 48 hours were 43.8%, 56.3%, and 54.8% respectively; at the end of fermentation, samples were obtained from the four fermentation methods of natural fermentation, yeast fermentation, mixed bacterial fermentation, and lactic acid bacteria fermentation. The reducing sugar contents are 3.63%, 4.32%, 3.20%, and 3.94% respectively. The samples fermented by mixed bacteria were significantly different from the other three fermentation methods (p<0.05).

In summary, the above experimental data analysis shows that fresh jujube adopts three different pretreatment methods: peeled, cored and not punctured, not peeled, cored and punctured, and not peeled, cored and not punctured. After fermentation by lactic acid bacteria, through comprehensive analysis During the fermentation process, the changes and flavor of total acid, total phenols, total sugar and reducing sugar were screened out, and the pretreatment method of fresh dates without peeling, pitting or puncturing before fermentation was selected as the better treatment method, with lower total sugar content. The total phenolic content is high; after the fresh jujubes are treated with the preferred pretreatment method, they are fermented using four different fermentation methods: natural fermentation, lactic acid bacteria fermentation, yeast fermentation, and lactic acid-yeast mixed fermentation. The changing trends of reducing sugar, total acid, total sugar, and total phenolic contents during the process were used as evaluation indicators. It was concluded that the best fermentation method for fermented date cheese is yeast-lactic acid bacteria mixed fermentation. The inoculation ratio is 1:1, and the total sugar content is 1:1. The lowest content is 25.73%, and the highest total phenolic content is 47.83mg/g.

Example 8: Comparison between dried date cheese and common date products

In order to further examine the performance of the new fermented product of the present invention, this test compared the quality indicators of the new fermented product dried jujube obtained in Example 2 of the present invention with the jujube products puffed jujube slices and puffed half jujubes. The specific results are shown in Table 1.

Table 1: Comparison of some quality indicators between dried date cheese and other processed date products

It can be seen from the data analysis in Table 1 that the total sugar and reducing sugar content per gram of dry matter are greatly reduced, and the sugar-acid ratio is also reduced, compared with the products obtained by puffing and drying the products obtained by mixed fermentation of fresh dates with lactic acid bacteria and yeasts. Taste evaluation: The sweetness of the product is reduced and the sourness is increased, which significantly improves the flavor of the product. It shows that the new fermented product provided by the present invention not only has a significant improvement in taste, but also has excellent quality. It is a brand-new snack food and is more in line with the health concept.

The above-described embodiments are merely examples to clearly illustrate the present invention, and are not intended to limit the implementation. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. An exhaustive list of all implementations is neither necessary nor possible. However, obvious changes or changes derived therefrom are still within the protection scope of the present invention.

Claims (2)

1. A kind of dried jujube cheese, characterized in that the dried jujube cheese is obtained by inoculating fresh jujube fruits with mixed bacteria, fermentation and drying; specifically, the following steps are adopted: after the fresh jujube fruits are washed, they are pre-treated without peeling, pitting and puncturing. , add citric acid with a concentration of 0.5% for color protection treatment for 10 minutes; put the processed jujube fruit into a 15×25cm vacuum bag, inoculate the mixed bacterial suspension according to 4% of the weight of the jujube fruit, vacuum seal, and seal at 37±1℃ Ferment for 60-84 hours; bake the fermented jujube fruit at 55-60°C for 10-12 hours until the moisture content is 20%, then vacuum-pack and sterilize it in a normal pressure water bath at 80°C for 20 minutes to obtain a new product of dried date cheese; The mixed bacterial suspension is obtained according to the following steps: Dissolve yeast: bifidobacteria in warm water at 30±0.5°C according to a mass ratio of 1:1 to prepare a suspension with a concentration of 20%, and activate it for 30 minutes. 2. Dried jujube cheese as claimed in claim 1, characterized in that the jujube fruit is any one of fresh and mature jujube, gray jujube and Hami jujube.