Method for producing fermented dates

Abstract

To provide a production method of fermented date which enables effective fermentation of date and production of highly palatable fermented date with fresh sourness and comfortable sweetness by way of forming gluconic acid as well as having glucose consumed.SOLUTION: The method includes a water-addition step for adding water to date fruit or date juice to obtain date hydrate and a fermentation step for inoculating acetic acid bacteria to the date hydrate for fermentation.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing fermented dates. [Background technology]

[0002] Dates, the fruit of the date palm, are eaten as dried fruits, and their puree is also used as an ingredient in sauces.Dates are rich in dietary fiber and contain many nutrients, including minerals such as potassium and magnesium, so they have been attracting attention in recent years as a health food, but they are less well known than other dried fruits such as prunes and raisins.

[0003] Dates are characterized by their rich sweetness, similar to that of dried persimmons or brown sugar. However, some people find this unique sweetness to be too sweet, and efforts are being made to reduce the sweetness to improve palatability.

[0004] For example, Patent Document 1 discloses a method of masking the harsh taste and reducing the sweetness by adding lactic acid bacteria to concentrated date juice and fermenting it. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-004756 Summary of the Invention [Problem to be solved by the invention]

[0006] However, simply reducing the sweetness in this way does not significantly change the unique taste of dates, and it can be said that it has little effect in increasing the palatability of fermented dates.

[0007] An object of the present invention is to provide a method for efficiently producing a highly palatable fermented date product having a fresh sour taste and moderate sweetness. [Means for solving the problem]

[0008] As a result of intensive research aimed at solving the above problems, the present inventors have found that fermenting dates with acetic acid bacteria can achieve more efficient fermentation than with lactic acid bacteria.Furthermore, they have found that fermenting dates with acetic acid bacteria imparts a fresh sour taste to the dates due to the production of gluconic acid, while reducing sweetness due to the consumption of glucose, thereby producing a fermented date product with excellent palatability, and have completed the present invention.

[0009] That is, the method for producing the fermented date product of the present invention comprises a hydration step of adding water to date fruits or date juice to obtain a date hydrate, and a fermentation step of inoculating the date hydrate with acetic acid bacteria to ferment it.

[0010] The date hydrate preferably has a Brix value of 15% to 30%.

[0011] The acetic acid bacteria are preferably at least one species selected from the genus Acetobacter, Gluconobacter, and Komagataebacter.

[0012] The fermentation step is preferably carried out until the gluconic acid concentration of the date fermented product reaches 2% (w / v) or more. [Effects of the Invention]

[0013] According to the method for producing fermented dates of the present invention, dates can be fermented efficiently, and by consuming glucose and producing gluconic acid, a highly palatable fermented date product with a fresh sour taste and moderate sweetness can be obtained. [Brief explanation of the drawings]

[0014] [Figure 1]1 is a flowchart showing an outline of the process for producing fermented dates. [Figure 2] 1 is a graph showing the results of a test comparing the glucose consumption amounts of Lactic acid bacteria α and Acetobacterium 1. [Figure 3] 1 is a graph showing the results of a test comparing the glucose consumption amounts of Lactic acid bacteria α and Acetobacterium 1. [Figure 4] 1 is a graph showing the test results of inoculating acetic acid bacteria I to V into date hydrate with Brix 20%. [Figure 5] 1 is a graph showing the test results of inoculating acetic acid bacteria I to V into hydrated dates with a Brix of 35%. [Figure 6] 1 is a graph showing the test results of inoculating acetic acid bacteria V into date hydrate with Brix 25%. [Figure 7] 1 is a graph showing the test results of inoculating acetic acid bacteria V into date hydrate with Brix 30%. [Figure 8] 1 is a graph showing the test results of inoculating acetic acid bacteria VI into date hydrate with Brix 24%. [Figure 9] 1 is a graph showing the test results of inoculating acetic acid bacteria VI into date hydrates with Brix of 15% to 35%. [Figure 10] 1 is a graph showing the average values ​​of the sensory evaluation results of fermented dates. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following description will be given in detail with reference to the accompanying drawings, but the following description is merely illustrative in nature and is not intended to limit the present invention, its applications, or its uses.

[0016] <Dates> Dates are the fruit of the date palm, which is cultivated mainly in the Middle East. They are about 2-3 cm in size, contain a seed, and are covered on the outside with a peel. Dates are highly nutritious, containing a lot of carbohydrates, minerals, and dietary fiber.

[0017] For this reason, dates have been widely eaten as dried fruits in the Middle East since ancient times. In Japan, dates are eaten as dried fruits and are also used as ingredients in processed foods such as sauces.

[0018] When dates are used as an ingredient in processed foods such as sauces, the fruit itself is used. It is usually processed into a puree (date puree). Date puree is made by adding a certain amount of water to date fruit and grinding it until it is finely ground.

[0019] The raw material used in the present invention is date fruit or date juice, but date fruit also includes date puree. The date hydrate obtained by adding water to date fruit or date juice is date puree or date juice.

[0020] The Brix value of the date hydrate is preferably less than 35%, more preferably 30% or less, and even more preferably 15% to 30%. The Brix value is the reading of a sugar refractometer at 20°C, and in this embodiment, the Brix value is measured using a digital refractometer (X-5000α, manufactured by ATAGO).

[0021] <Acetic acid bacteria> Acetic acid bacteria can ferment date hydrate more efficiently than lactic acid bacteria, consuming more glucose. Furthermore, gluconic acid produced from glucose by acetic acid fermentation imparts a fresh sourness that harmonizes with the characteristic sweetness of dates, thereby enhancing the palatability of fermented date products. The acetic acid bacteria used in the present invention are bacteria belonging to the Acetobacteraceae family, and are preferably at least one species selected from the genera Acetobacter, Gluconobacter, and Komagataeibacter, although they are not particularly limited thereto.

[0022] Examples of acetic acid bacteria of the genus Acetobacter include Acetobacter pasteurianus, Acetobacter orientalis, Acetobacter aceti, and Acetobacter indonesiensis. Acetobacter pasteurianus NBRC 3284 is more preferred.

[0023] Examples of acetic acid bacteria of the genus Gluconobacter include Gluconobacter oxydans and Gluconobacter frateurii. More preferred are Gluconobacter oxydans NBRC 3287, Gluconobacter oxydans NBRC 12528, and Gluconobacter oxydans 621H.

[0024] Examples of acetic acid bacteria of the genus Komagataeibacter include Komagataeibacter medellinensis, Komagataeibacter hansenii, and Komagataeibacter europaeus. Komagataeibacter medellinensis NBRC 3288 or Komagataeibacter sp. isolated from brewery barrels at Otafuku Brewery Co., Ltd. are more preferred. While Komagataeibacter sp. has not yet been deposited with a public institution, it is stored in the Otafuku Sauce Co., Ltd. laboratory and can be distributed as needed.

[0025] -Method of producing fermented dates- Figure 1 shows the main steps of the method for producing fermented dates. This production process consists of a hydration step, a heat sterilization step, and a fermentation step. Acetic acid bacteria are inoculated into the hydrated dates and fermented. The fermentation step using acetic acid bacteria is an essential step in this production method.

[0026] This method efficiently converts glucose in the date hydrate into gluconic acid, resulting in a gluconic acid-rich fermented date product. The resulting fermented date product has a fresh sour taste due to gluconic acid and a moderate sweetness due to the consumption of glucose. It has a smooth texture and good color, making it suitable as an ingredient for processed foods.

[0027] (hydration process) In this step, a predetermined amount of water is added to date fruits or date juice and mixed, thereby obtaining date hydrate. The Brix value of the date hydrate is preferably adjusted to 15% to 30% in this hydration step. If the Brix value is less than 15%, the moisture content increases, impairing the unique flavor of the dates and making it unsuitable as a processed food ingredient. Furthermore, if the Brix value is 35% or more, the progress of acetic acid fermentation rapidly decreases. From the viewpoints of suitability as a raw material for processed foods and fermentation efficiency, the Brix value of the date hydrate is preferably adjusted to 15% to 30%, more preferably 20% to 30%.

[0028] (sterilization process) To ensure smooth fermentation, it is preferable to sterilize the date hydrate prior to the fermentation process. For example, the date hydrate can be heated to 70°C or higher and kept at this temperature for 20 minutes or more. This prevents the proliferation of bacteria and yeast.

[0029] (cooling process) After the sterilization process, the mixture is cooled to approximately 30°C, which is the optimum temperature for acetic acid bacteria activity.

[0030] (Inoculation process) The date hydrate was inoculated with acetic acid bacteria. The acetic acid bacteria used were pre-cultured in a saccharified solution with a concentration of 30%, but the method for inoculation is not limited as long as it is possible to inoculate.

[0031] (Fermentation process) In the fermentation process, in order to impart a fresh sour taste to the fermented date product, it is preferable to ferment the date fermented product until the gluconic acid concentration reaches 2% (w / v) or more. In this fermentation process, glucose in the date hydrate is converted to gluconic acid by acetic acid bacteria, which reduces the sweetness of the resulting fermented date product and imparts a fresh sour taste to it.

[0032] The fermentation process can be carried out using the same method as in conventional acetic acid fermentation, and can be performed using any of agitation fermentation, shaking fermentation, and static fermentation. However, when date juice is used as the raw material, agitation fermentation can reduce the fermentation efficiency due to foaming of the date hydrate, so shaking fermentation or static fermentation is more preferred. Furthermore, if the date hydrate is a date puree, bubbles are less likely to form even when stirred. Furthermore, the temperature and fermentation period are not limited, but a temperature of approximately 30°C and a fermentation period of 4 to 7 days are preferred.

[0033] -Comparative study of acetic acid bacteria and lactic acid bacteria- Acetic acid bacteria or lactic acid bacteria were inoculated into date hydrate and fermented to compare the glucose consumption. Lactobacillus brevis 1059T strain (hereafter referred to as Lactic Acid Bacterium α) was used as the lactic acid bacterium, and Gluconobacter oxydans NBRC 3287 (hereafter referred to as Acetic Acid Bacterium I) was used as the acetic acid bacterium. The fermentation temperature was 30°C. The glucose content in the date fermentation product was quantified using HPLC (Prominence, Shimadzu Corporation).

[0034] Figure 2 is a graph showing the results of a test comparing the glucose consumption of Lactic Acid Bacteria α and Acetobacter I. Figure 2 shows the glucose amounts on the 0th and 6th days of fermentation when Lactic Acid Bacteria α and Acetobacter I were inoculated into date hydrate with a Brix value of 20%. The glucose consumption of Acetobacter I was greater than that of Lactic Acid Bacterium α, and the difference was significant.

[0035] Figure 3 is a graph showing the results of a test comparing the glucose consumption amounts of Lactic Acid Bacteria α and Acetobacter I. Figure 3 shows the glucose amounts on days 0 and 6 of fermentation when Lactic Acid Bacteria α was inoculated into a date hydrate (date puree) with a Brix value of 37.7%, and the glucose amounts on days 0 and 6 of fermentation when Acetobacter I was inoculated into a date hydrate with a Brix value of 35%. These results show that when Acetobacter I and Lactic Acid Bacteria α were inoculated into date hydrate with a Brix value of 35% or more, the fermentation efficiency was lower than that of date hydrate with a Brix value of 20%, but Acetobacter I consumed more glucose than Lactic Acid Bacterium α.

[0036] These results suggest that acetic acid fermentation is more suitable than lactic acid fermentation for consuming glucose in date hydrates.

[0037] -Study using acetic acid bacteria I to V- Next, various types of acetic acid bacteria were inoculated into date hydrate (date puree) and subjected to static fermentation at 30°C. In addition to the above-mentioned acetic acid bacteria I, Acetobacter pasteurianus NBRC 3284 (hereinafter also referred to as acetic acid bacteria II), Gluconobacter oxydans NBRC 12528 (hereinafter also referred to as acetic acid bacteria III), Gluconobacter oxydans 621H (hereinafter also referred to as acetic acid bacteria IV), and Komagataeibacter medellinensis NBRC 3288 (hereinafter also referred to as acetic acid bacteria V) were used as acetic acid bacteria.

[0038] Figure 4 is a graph showing the amount of gluconic acid in the fermented date product after 7 days of fermentation in which acetic acid bacteria I to V were inoculated into date puree with a Brix of 20%. Specifically, 7 g of date hydrate was fermented in a 50 ml tube. In Figure 4, the control was a date hydrate that was not inoculated with acetic acid bacteria and left to stand under the same conditions as the others. The gluconic acid in the fermented date product was quantified using HPLC (Prominence, Shimadzu Corporation).

[0039] As shown in Figure 4, in all samples using 20% ​​Brix date puree and Acetobacter I to V, the gluconic acid content more than doubled from the initial value, reaching a concentration of 2% (w / v) or more, indicating that acetic acid fermentation was progressing well. In particular, Acetobacter I and Acetobacter IV produced significant amounts of gluconic acid.

[0040] Figure 5 is a graph showing the amount of gluconic acid in the fermented date puree after 7 days of fermentation inoculated with Acetobacter species I to V into 35% Brix date puree. Specifically, 7 g of date hydrate was fermented in a 50 ml tube. In Figure 5, the control was a date hydrate that was left standing under the same conditions as the others but without inoculation with Acetobacter species.

[0041] As shown in Figure 5, in all samples using date puree with Brix 35% and acetic acid bacteria I to V, the production of gluconic acid was slight, and fermentation was suppressed compared to when date puree with Brix 20% was used.

[0042] Next, date juice containing almost no fiber was inoculated with Acetobacter cerevisiae I and fermented.

[0043] Figure 6 shows the amounts of glucose and gluconic acid in the fermented date juice (Brix 25%) before and after 6 days of fermentation, in which acetic acid bacteria I were inoculated. Specifically, 10 g of date juice was statically fermented in a 50 ml tube.

[0044] As shown in Figure 6, a decrease in the amount of glucose and an increase in the amount of gluconic acid were observed, confirming the acetic acid fermentation of the date juice. However, the fermentation was weaker than that of the date puree, which contains a lot of fiber.

[0045] Figure 7 shows the amounts of glucose and gluconic acid in the fermented date juice (Brix 30%) before and after 6 days of fermentation, in which acetic acid bacteria I were inoculated. Specifically, 10 g of date juice was statically fermented in a 50 ml tube.

[0046] As shown in Figure 7, a decrease in the amount of glucose and an increase in the amount of gluconic acid were observed, confirming that the acetic acid fermentation of date juice was more advanced than that of Brix 25%, but the fermentation was weaker than that of date puree, which contains a lot of fiber.

[0047] These results indicate that date puree, which contains a lot of fiber, promotes acetic acid fermentation more efficiently than date juice, which contains less fiber.

[0048] -Study using Acetobacter VI- Next, Komagataeibacter sp. (hereinafter also referred to as acetic acid bacteria VI) isolated from the brewing barrels of Otafuku Brewery Co., Ltd. was inoculated into the date hydrate (date puree) and subjected to static fermentation at 30°C.

[0049] Fig. 8 is a graph showing the amounts of glucose and gluconic acid in the fermented date products obtained by inoculating Acetobacter VI into date puree (Brix 24%) before fermentation, after 4 days of fermentation, and after 7 days of fermentation. Specifically, 100 g of date puree was fermented in a 500 ml beaker.

[0050] As shown in Figure 8, after 4 days of fermentation, 3.3 (w / v)% of gluconic acid was produced, imparting a sufficient sourness to the fermented dates. After 7 days of fermentation, 5.1 (w / v)% of gluconic acid was produced. Acetobacter VI had a fermentation efficiency equivalent to that of Acetobacter I and Acetobacter IV, which showed remarkable fermentation in the above study.

[0051] These results indicate that acetic acid bacteria belonging to the genera Acetobacter, Gluconobacter, and Komagataeibacter are suitable for fermenting date hydrate, with Gluconobacter oxydans NBRC 3287 (acetic acid bacteria I), Gluconobacter oxydans 621H (acetic acid bacteria IV), and Komagataeibacter sp. (acetic acid bacteria VI) isolated from the brewing barrels of Otafuku Brewery Co., Ltd. being particularly suitable.

[0052] From the results of Figures 4 and 5, it was found that the fermentation efficiency of date hydrates tended to decrease significantly when the Brix value of the hydrated date fruit was 35% or higher. Therefore, the Brix value of the hydrated date fruit was further examined using Acetobacter VI.

[0053] Figure 9 shows the gluconic acid content in the fermented date products after 6 days of fermentation with Acetobacter VI in date purees with Brix values ​​of 15%, 20%, 30%, and 35%. Specifically, 10 g of date puree was statically fermented at 30°C in a 50 ml tube.

[0054] As shown in Figure 9, up to a Brix of 30%, gluconic acid was produced well, indicating that acetic acid fermentation was progressing. However, at a Brix of 35%, the amount of gluconic acid produced was significantly low, indicating that acetic acid fermentation was also suppressed.

[0055] From the results of Figures 4, 5 and 9, it was found that a Brix of 30% or less is suitable for acetic acid fermentation of date hydrate. When the Brix of date hydrate is less than 15%, the acetic acid fermentation proceeds well, but the resulting fermented date product has a high water content, which impairs the unique flavor of dates and is therefore unsuitable for further processing. Therefore, a Brix of 15% to 30% is more preferable for date hydrate.

[0056] -Sensory evaluation- Using the above-mentioned Acetobacter VI, date puree with a Brix of 25 was subjected to acetic acid fermentation for 5 days to obtain a date fermented product with a Brix of 26%. Specifically, 100 g of date puree was statically fermented in a 500 ml beaker at 30°C. The increase in Brix value after fermentation is thought to be due to concentration caused by drying. This date fermented product was compared with unfermented date puree that had only been watered to a Brix of 26%, and a sensory evaluation was performed.

[0057] Analysis of unfermented and fermented date puree revealed that the pH, which was 5.4 before fermentation, increased to 3.0 after fermentation, and the acidity, which was 0.111 before fermentation, increased to 1.444 after fermentation, as shown in Table 1. The glucose, gluconic acid, acetic acid and ethanol contents in the fermented date puree were as shown in Table 2.

[0058] [Table 1]

[0059] [Table 2]

[0060] A sensory evaluation was conducted by nine men and women in their 20s to 50s comparing unfermented and fermented date purees, and the results are shown in Table 3. For each of the categories of sourness, sweetness, freshness, smoothness, and color brightness, the unfermented date puree was given a score of 3, and if the fermented date puree was stronger than that, the maximum score was 5, and if it was weaker, the minimum score was 1.

[0061] [Table 3]

[0062] All participants answered that the fermented product had a stronger sour taste and a weaker sweet taste. In addition, seven out of nine participants answered that the fermented product had a stronger freshness. In terms of smoothness, all participants answered that it was equal to or better than the unfermented product. In terms of color, all participants answered that the fermented product was lighter. Table 4 shows the average scores of the nine participants, and Figure 10 shows the balance of taste and color of fermented dates based on the evaluation.

[0063] [Table 4]

[0064] Due to the production of gluconic acid, the date fermented product obtained by acetic acid fermentation exhibits a fresh, sour taste, even after fermentation. The sourness of gluconic acid is not sharp, but rather fruity, and the consumption of glucose results in a moderate sweetness, giving the product a sweet-and-sour freshness with a good balance of sweetness and sourness. Therefore, date fermented products containing gluconic acid have excellent palatability. Furthermore, the fermented date products tend to have a smoother mouthfeel, with the graininess characteristic of dates reduced. Furthermore, the fermented date products exhibited a brighter color than before fermentation.

Claims

1. a hydration step of hydrating date fruits or date juice to obtain a date hydrate having a Brix value of 20% to 30%; a fermentation step inoculating the date hydrate with acetic acid bacteria to ferment it; A method for producing fermented dates as a raw material for processed foods, comprising:

2. 2. The method for producing fermented dates according to claim 1, wherein the acetic acid bacteria is at least one species selected from the group consisting of Acetobacter, Gluconobacter, and Komagataebacter.

3. 3. The method for producing date fermented product according to claim 2, wherein the fermentation step is carried out until the gluconic acid concentration of the date fermented product reaches 2% (w / v) or more.

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