JPH0984520A - Production of fermented milk reduced in lactose content - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fermented milk reduced in the content of lactose, prevented in the contamination of various microbes, and reducing the amount of a sweet raw material by degrading the lactose contained in a lactose- containing milk with a specific lactase and subsequently deactivating the lactase by the lowering of pH accompanied by the advance of the fermentation. SOLUTION: Lactose contained in a milk containing the lactose is degraded with a lactase which has the optimal pH of the activity in a neutral region and is deactivated in an acidic region, such as a lactase originated from Kluyveromyces-Lactis or Kluyveromyces-Fragilis, before and/or during the fermentation, and the lactase is subsequntly deactivated by the lowering of pH accompanied by the advance of the fermentation, thus affording the fermented milk reduced in the lactose and having a pH of <=4.0.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing fermented milk having a low lactose content. More specifically, the present invention uses lactase, which has an optimum pH of activity in a neutral region and inactivates in an acidic region, to decompose lactose before and / or during the fermentation, and to promote the fermentation. The present invention relates to a method for producing fermented milk having a low lactose content, which comprises deactivating lactase by lowering the pH. Lactose is inherently contained in dairy products, for example, milk usually contains 4.5% lactose.
Therefore, when a lactose intolerant person takes a dairy product having a high lactose content, symptoms such as abdominal pain, diarrhea, and abdominal swelling may occur due to lactose. Therefore, ingesting fermented milk obtained by fermenting milk with lactic acid or yeast to decompose lactose to some extent is considered to be effective for those with lactose intolerance to reduce the above symptoms. However, when milk is fermented with lactic acid bacteria or yeast as it is, the amount of lactose that is decomposed is as low as about 20%, so that it may not be possible to alleviate the above-mentioned symptoms depending on individuals with lactose intolerance. Therefore, in order to increase the lactose decomposition rate, lactose is separately decomposed by lactase treatment to produce fermented milk that can be easily ingested by persons with lactose intolerance.

[0002]

2. Description of the Related Art A conventional method for producing fermented milk decomposed with lactose is to add lactase to milk before sterilization to decompose lactose, and then to deactivate lactase simultaneously with heat sterilization of milk. Fermentation method (JP-A-5-501197)
Gazette), lactase is added to sterilized milk to decompose lactose, and then a method of fermenting milk by deactivating lactase by heat treatment, after decomposing lactose in milk with immobilized lactase, Method for fermenting milk (JP-A-46-105593, JP-A-59-162833)
Gazette), a method of fermenting raw materials, which have been lactose-decomposed or lactose-removed, in sterile milk.

[0003]

The conventional method described above, in which lactase is added to milk before sterilization, requires a time required for decomposing lactose in addition to the conventional fermentation time, resulting in poor work efficiency. Since milk before sterilization is kept for a certain period of time, there is a possibility that various bacteria may be contaminated. The method of deactivating lactose by adding lactase to sterilized milk and decomposing lactose by heat treatment also requires the time required for decomposing lactose and the time required for two heat treatments in addition to the fermentation time. Inefficient and economically undesirable. In addition, when the inactivation of lactase is not sufficient, lactase further decomposes lactose during distribution of the product, and the resulting glucose, galactose or the like may change the flavor of the product. The method using immobilized lactase is economically problematic because maintenance of the activity of immobilized lactase and maintenance such as sterilization are troublesome.
The method of using a raw material which has been lactose-decomposed or lactose-removed in advance for sterilized milk is more expensive than the conventional raw material and economically undesirable. The present invention, etc., as a result of intensive research to solve the above problems, without undergoing a special heating step for lactase inactivation, by inactivating lactase by lowering the pH by fermentation, Not only does it prevent contamination of bacteria, but it is also excellent in work efficiency and economy.
The inventors of the present invention have found a method that makes it easy to control the rate of glycolysis and have reached the present invention.

[0004]

Means for Solving the Problems That is, the present invention is a method for producing fermented milk in which milk containing lactose is fermented with lactic acid bacteria or yeast, and the optimum pH of activity is in the neutral range and deactivated in the acidic range. Lactose is decomposed before and / or during the fermentation using lactase
The problem is solved by providing a method for producing fermented milk having a low lactose content, which is characterized in that lactase is inactivated by a pH drop accompanying the progress of fermentation.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is a method for decomposing lactose in fermented milk raw material by using lactase. Lactase, which has an optimum pH for activity in the neutral region and inactivation in the acidic region, is added to pasteurized milk. By doing so, lactose is decomposed, and the lactase inactivation treatment is performed by utilizing lactic acid of milk or pH drop due to yeast fermentation. And since this method only adds lactase addition to the conventional fermentation process, work efficiency in terms of not adding a heat treatment step to deactivate lactose or to add time to bother for decomposing lactose, It is fermented milk that is economically excellent, that the setting of the lactose decomposition rate can be easily controlled by the addition timing and the addition amount of lactase, and that the flavor is excellent. In addition, since the sweetness of fermented milk is enhanced by decomposing lactose and the amount of sweetener used can be reduced, an economic effect is also expected.

(Lactase to be used) The lactase used in the present invention is derived from bacteria or yeast and has an optimum activity pH of 6.3 to 7.5 and an optimum temperature of 30 to 50.
A material having a deactivation pH of 6.0 to 4.0 at a temperature of ℃ is used. Suitable lactases for these include Kl
uyveromyces Lactis, Kluyveromyces Fragilis, Asperg
Lactase derived from illus niger and Aspergillus oryzae, but most preferably Kluyveromyces Lacti
s, Lactase from Kluyveromyces Fragilis.

(Time of addition of lactase) The time of adding lactase in the fermentation of milk can be roughly classified into the following modes. A method in which lactase is added to pasteurized milk at the same time as the starter used for fermentation to perform lactose decomposition and milk fermentation in parallel,
Lactase is added to pasteurized milk in advance, a method of fermenting milk by adding a starter after decomposing lactose to some extent,
There are three methods of adding a starter and fermenting milk to some extent and then adding lactase. Both methods are characterized by deactivating lactase by lowering the pH by fermentation of milk. As described above, by performing lactose decomposition by lactase and lactic acid fermentation in parallel, the heating and inactivating step of lactase is not required, and the working efficiency can be improved.

[0008]

When a starter and lactase, which has an optimum pH for activity in the neutral region and inactive in the acidic region, are added to sterilized milk,
Lactose decomposition and milk fermentation proceed over time. As lactic acid or yeast fermentation progresses, the pH gradually drops, so that lactase is deactivated and lactose-degraded lactose is stopped. If lactose is decomposed by utilizing this phenomenon, the target lactose decomposition rate can be easily set by adjusting the order of addition of lactase and seed or the amount of lactase added.
Although the lactose decomposition rate in fermented milk by only ordinary fermentation is about 30%, any decomposition rate can be achieved by the method of the present invention. That is, when seeds with a fast pH drop are used, it may be possible to add lactase in advance to lactose-decompose it to some extent and then ferment the milk, or increase the amount of lactase added. In that case, it is conceivable to add seeds in advance and ferment to some extent before adding lactase, or to reduce the amount of lactase added, and any method will facilitate the setting of the target lactose decomposition rate. .
Also, fermented milk that decomposes lactose has enhanced sweetness,
The amount of sweeteners used in products can be reduced.

[0009]

[Test example]

Test Example The present invention will be described in detail below with reference to a test example. (1) Test Example-1 This test was conducted to examine the titer of lactase to be added. [Refer to Enzyme Utilization Handbook (Jijijinkan Co., Ltd.)] Principle Lactase is ONPG (o-Nitrophenyl-D-galactopyann
oside) to decompose ONP (o-Nitrophenol) and galactose, and measure the generated ONP. Unit titer When lactase acts on ONPG at pH 6.5 and 30 ° C., the amount of lactase that produces 1 μml of ONP in the reaction solution per minute is defined as 1 unit.

Reagent 1) 0.1 M pH 6.5 phosphate buffer (10 ^-4 M Mn
Cl ₂ included): Disodium phosphate solution is added to monosodium phosphate solution to adjust pH to 6.5. Manganese chloride solution: Manganese chloride tetrahydrate 1.9
Dissolve 79 g in water to 100 ml Monosodium phosphate solution: Dissolve 15.601 g of monosodium phosphate dihydrate in water and add 1 ml of manganese chloride solution to make 1 liter. Disodium phosphate solution: Dissolve 35.814 g of disodium phosphate dodecahydrate in water, and 1 ml of manganese chloride solution
To 1 liter. 2) 0.02M pH 6.5 phosphate buffer (10 ^-4 M M
nCl ₂ included): 1 sodium phosphate solution in 2 phosphate
Adjust the pH to 6.5 by adding sodium solution. Monosodium phosphate solution: Dissolve 15.601 g of monosodium phosphate dihydrate in water and add 1 ml of manganese chloride solution to make 1 liter. Disodium phosphate solution: Dissolve 35.814 g of disodium phosphate dodecahydrate in water, and 1 ml of manganese chloride solution
Is added to make 1 liter. 3) 1M sodium carbonate solution: sodium carbonate (anhydrous)
Dissolve 10.599 g in water to make 100 ml. 4) ONPG solution: To 0.172 g of ONPG, 70 ml of 0.1 M phosphate buffer is added and dissolved by heating in a boiling water bath. Cool it to room temperature and add 1M with 0.1M phosphate buffer.
Make up to 00 ml.

Preparation of Sample Lactase (extracted from Kluyveromyces Lactis: Nagase Seikagaku Co., Ltd., 0.02M phosphate buffer (pH 6.
5) Dilute to a concentration of 0.1-0.2 / ml. Preparation of ONP standard curve 0.1M phosphate buffer: 3.5 ml, 0.02M phosphate buffer: 0.5 ml, ONP was dissolved in a mixed solution of 1.0 ml of sodium carbonate solution to give 0.1,0. 0.2, 0.3, 0.4 μml
The solution is diluted so that the concentration becomes, and the absorbance of each solution is measured at a wavelength (420 nm) to prepare a calibration curve. ONP concentration for absorbance of 1,000 (fμmol / m
l) is required.

Measurement method 1) Sample solution: Collect 3.5 ml of ONPG solution in a test tube, keep it in a constant temperature water bath at 30 ° C. for 3 minutes, add 0.5 ml of lactase solution previously kept at 30 ° C., and immediately shake. 3 this liquid
After reacting at 0 ° C. for exactly 10 minutes, 1 ml of 1M sodium carbonate solution was added, and the mixture was shaken and immediately cooled in ice water to stop the reaction. 2) Collect 3.5 ml of ONPG solution in a blank test tube, add 1 ml of 1M sodium carbonate solution and shake, add 0.5 ml of lactase solution and shake, and immediately cool in ice water.

3) Calculation method Calculation is performed using the following calculation formula. Titer (U / ml) = (A _S −A _B ) × f × 5 × 1/10 × D
× 2 A _S: sample solution absorbance A _B: Blank Absorbance f: ONP to the absorbance 1.000 Concentration ([mu] mol / m
l) D: Lactase dilution ratio

(2) Test Example-2 This test was carried out in order to investigate the characteristics of lactase to be added. 1) pH and lactose decomposition rate (inactivation of pH and lactase) Sterilized milk held at 34 ° C after UHT heat treatment (120 ° C, 3 seconds) (dissolved skim milk powder, milk solid content 23%, lactose content 12. 2%) and adjust the pH with 50% citric acid solution,
Yeast diluted with 0.45μ filter (Kluyv
eromyces Lactis derived lactase (titer 10000
U / ml (result by the measuring method of Test Example 1) 1.5
U / 1 ml of pasteurized milk was added. Then, the sugar composition after 0 and 24 hours was measured by HPLC to calculate the lactose decomposition rate. As shown in Table 1, the optimum pH of activity is 6.5,
It was found to be deactivated at pH 5.5 or lower. It was found that this lactase property is highly active in pasteurized milk in the neutral region and is inactivated by the pH drop due to fermentation.

[0015]

[Table 1] Table 1 pH and lactose decomposition rate pH 5.5 6.0 6.0 6.5 7.0 8.0 Decomposition rate (%) 0 82 100 75 32

2) Reaction Temperature and Lactose Decomposition Rate UHT heat-treated (120 ° C., 3 seconds) pH 6.4 sterilized milk (dissolved skim milk powder, milk solid content 23%) is diluted 2-fold and 0.45μ filter Through yeast (Kluyveromyces L
Lactase from actis) (titer 10000 U / ml)
5U / 1ml of pasteurized milk was added. Then, the sugar composition after 0 and 24 hours was measured by HPLC to calculate the lactose decomposition rate. As shown in the results in Table 2, it was found that the optimum temperature of activity was 40 ° C., and the lactose decomposition rate decreased at the upper and lower limits with the optimum temperature as the boundary. This lactase property was found to be highly active in the fermentation temperature range of 30 to 40 ° C.

[0017]

[Table 2] Table 2 Reaction temperature and lactose decomposition rate Temperature (° C) 20 30 35 40 45 50 Degradation rate (%) 45 65 83 83 100 78 20

3) Lactase Addition Amount and Lactose Decomposition Rate in Fermented Milk A 0.45μ filter was obtained by diluting the sterilized milk (fat dry milk dissolved, milk solid content 23%) heat-treated at UHT (120 ° C., 3 seconds) 2-fold. Yeast (Kluyveromyces Lactis) -derived lactase (titer 10000 U / ml) was passed through 0.5 to 2.0.
U / 1 ml of pasteurized milk and 2 types of mixed starter (Str.ther
mophlus, L. casei) 0.25% (v / v) was added.
Then, the sugar composition after the fermented milk reaches pH 4.4 is changed to H.
It measured by PLC and calculated the lactose decomposition rate. As shown in the results in Table 3, the lactose decomposition rate increases as the amount of lactase added increases. This lactase property has important implications for controlling the setting of the lactose degradation rate.

[0019]

[Table 3] Table 3 Lactase addition amount and lactose decomposition rate Addition amount (U) 0.5 0.7 0.9 1.1 1.3 1.5 1.9 Decomposition rate (%) 44 52 61 66 69 72 77

[0020]

The present invention will be described in detail below with reference to examples.
The present invention is not limited to the following examples. (1) Example-1 UHT heat-treated (120 ° C., 3 seconds) sterilized milk (fat dry milk dissolved, milk solid content 25%, 400 l) was kept at 34 ° C., and yeast filtered through 0.45 μ ( Kluyveromyc
Lactase derived from es Lactis (optimal pH 6.5, optimal temperature 40 ° C, inactivation pH 5.5, titer 10000 U / ml) 1.
5U / ml of pasteurized milk and 2 kinds of lactic acid bacteria (Str. Thermophile
us, L. casei) 0.25% (v / v) were added at the same time to perform lactose decomposition treatment and fermentation. Then, from this experiment, changes in pH and lactose decomposition rate with time shown in Table 4 below were obtained. From this result, about 70% of the lactose contained in the fermented milk was decomposed. On the other hand, for comparison, when the same fermentation was carried out without the addition of lactase, the decomposition rate of lactose was only 29% as shown in the control test of Table 4.

[0021]

[Table 4]

(2) Example-2 Heat-treated (100 ° C., 5 minutes) sterilized milk (dissolved skim milk powder, milk solid content 25%, 400 l) was kept at 34 ° C., and 0.45 μ was added to this sterilized milk. Filtered yeast (Kluyv
Lactase derived from eromyces Lactis (optimum pH 6.5,
Optimum temperature 40 ℃, deactivation pH 5.4, titer 10000U / m
l) of 1.5 U / 1 ml of sterilized milk and reacted for 2 hours to decompose lactose to some extent, and then two types of lactic acid bacteria (Str.thermo
philus, L. casei) 0.25% (v / v) was added for lactose decomposition treatment and fermentation. From this experiment, the time-dependent changes in pH and lactose decomposition rate shown in Table 5 below were obtained. From this result, the lactose contained in the fermented milk was decomposed by about 80%.

[0023]

[Table 5]

(3) Example-3 (Example in which yeast was used in combination) Heat-treated (100 ° C., 5 minutes) sterilized milk (dissolved skim milk powder, milk solid content 15%, 400 l) was kept at 30 ° C. Yeast (Kluyv
Lactase derived from eromyces Lactis (optimum pH 6.5,
Optimum temperature 40 ℃, deactivation pH 5.5, titer 10000U / m
l) was added in an amount of 1.5 U / sterilized milk (1 ml) and lactic acid bacterium (Str. lactis) was added in an amount of 0.5% (w / w) to perform lactose decomposition treatment and fermentation. After the pH of the pasteurized milk reached 4.35, add 100% sugar solution (40%) that had been pasteurized (100 ° C, 5 minutes) in advance.
Liter and 250 liters of syrup solution (fruit juice 30%, pectin 0.6%) were added to make a total of 1000 liters. Then, 0.2% (w / w) of yeast (Saccharomyces unisporus) was added to this raw material kept at 30 ° C. to perform yeast culture. As a result, about 70% of the lactose contained in the fermented milk raw material was decomposed.

(4) Example-4 A product is prepared by diluting the lactase-treated fermented milk produced in Experimental Example-1 above and fermented milk produced without adding lactase to a non-fat milk solid content of 8%. Then, sugar was added to fermented milk produced without the addition of lactase to examine the amount of sugar that had a flavor equivalent to that of lactase-treated fermented milk, and the sweetness increased by lactase treatment was confirmed. As a result, it was found that the lactase-treated product had a sweetness comparable to that obtained by adding 4 g of sugar to 1 l of the lactase-free product.

(5) Example-5 Using the lactase-treated fermented milk produced in Experimental Example-1 and the fermented milk produced without the addition of lactase, the products were prepared according to the formulations shown in Tables 6 and 7. Then, the flavor and physicochemical properties (acidity, number of bacteria) were compared.

[0027]

[Table 6]

[0028]

[Table 7]

[0029]

[Table 8]

As a result, there was no difference in the flavor and physicochemical properties between the lactose-degraded product and the product not treated.

[0031]

EFFECTS OF THE INVENTION Since the present invention is constituted as described above, fermented milk obtained by adding lactase and starter to sterilized milk at the same time, or adding lactase before and after the addition of starter to decompose lactose, can deactivate lactase. P due to milk fermentation
Since it can be done by H drop, it is excellent not only in terms of manufacturing to prevent contamination of various bacteria, but also in terms of work efficiency and economy, and the lactase decomposition rate can be easily set by adjusting the lactase addition timing and amount. You can control. Further, fermented milk that has been treated with lactase has an enhanced sweetness, so that it is possible to reduce the amount of the sweetening material that is added as a flavor adjustment, thus providing an economically excellent method for producing fermented milk.

Front page continuation (72) Inventor Mika Oeda 1-1-19 Higashishimbashi, Minato-ku, Tokyo Yakult Honsha Co., Ltd. (72) Inventor Yoshiharu Kuma 1-1-19 Higashishimbashi, Minato-ku, Tokyo Shares Company Yakult Head Office

Claims (5)

[Claims] 1. A method for producing fermented milk in which milk containing lactose is fermented with lactic acid bacteria or yeast, wherein lactase, which has an optimum pH for activity in the neutral region and deactivates in the acidic region, is used. A method for producing fermented milk having a low lactose content, which comprises decomposing lactose before and / or during the fermentation to inactivate lactase due to pH decrease accompanying the progress of fermentation. 2. The production method according to claim 1, wherein lactase which is inactivated in the range of pH 6.0 to 4.0 is used. 3. Kluyveromyces Lact as lactase
The method according to claim 1 or 2, wherein the lactase derived from is or Kluyveromyces Fragilis is used. 4. The production method according to claim 1, wherein the fermented milk has a pH of 4.0 or less. 5. Fermented milk produced by the method according to any one of claims 1 to 4.