CN1631184A

CN1631184A - Method for inhibiting brown stain of low lactose milk and products thereof

Info

Publication number: CN1631184A
Application number: CN 200310121748
Authority: CN
Inventors: 李文; 张雪梅; 卢阳; 佘国庆; 吕加平; 陈历俊
Original assignee: SANYUAN FOOD CO Ltd BEIJING
Current assignee: SANYUAN FOOD CO Ltd BEIJING
Priority date: 2003-12-22
Filing date: 2003-12-22
Publication date: 2005-06-29
Anticipated expiration: 2023-12-22
Also published as: CN100441099C

Abstract

Disclosed is a method for inhibiting brown stain of low lactose milk and products thereof, wherein the method comprises, under the condition of pH=6.6-6.8, temperature of 8-9 deg. C, charging lactose enzyme into milk, wherein the enzyme consumption is 0.5-0.75%, the enzymolysis time 14-8 hours, charging suppressant an or B during the sterilizing procedure. The processed milk has the performance of low lactose.

Description

Method for inhibiting browning of low-lactose milk and product thereof

[ technical field]A method for producing a semiconductor device

The invention relates to a milk treatment method and a product obtained by the method, in particular to a method for inhibiting browning of low-lactose milk and non-browning milk obtained by the method. Belongs to the field of dairy products and dairy processing.

[ background of the invention]

The milk is the most ideal natural food for feeding young mammals, and is rich in high-quality protein, milk fat, lactose and other nutritional ingredients, calcium, phosphorus, potassium and other minerals and multiple vitamins. In developed countries, milk and dairy products have become important components of the diet of people; the newly revised dietary guidelines of Chinese residents in China clearly emphasize that 'one person cups milk (250ml) a day' and the WHO also lists the consumption of the average human milk products as a main index for measuring the living standard of people in a country. Thus, cow's milk has an important role in the diet of humans.

Although cow milk has excellent nutritional value, in China, the annual average consumption of dairy products in 2000 years is less than 10Kg and far lower than the annual average consumption (100Kg) of dairy products in the world. Besides the relative lag of the development and processing level of dairy industry in China, lactose intolerance also limits the popularization of dairy products in China to a certain extent.

The lactose content in cow milk is about 4.8% (considering rosy clouds, 2000), and it is more than 99% of total sugar in cow milk. Under normal physiological conditions, lactose is hydrolyzed into glucose and galactose by lactase in the small intestine, and then the glucose and the galactose can be absorbed by human bodies. Investigations have shown that about 70% of all people worldwide (especially in sub-non-countries) lack lactase, and these people, after taking cow's milk, have adverse reactions such as diarrhea and flatulence, i.e. lactose intolerance (Fox et al, 1992). Therefore, in the process of dairy processing, the lactose-reduced milk produced by degrading lactose with lactase not only can provide high-quality glycogen for people, but also can greatly increase the milk intake of people suffering from lactose intolerance.

Chinese patent CN1258452A discloses a method for producing low-lactose milk by using solid-phase thermophilic bacteria lactase, wherein temperature parameters and strain using methods of the method for producing the low-lactose milk by using the solid-phase thermophilic bacteria lactase are disclosed, but in the sterilization process, the carbonyl in the reduced sugar obtained by decomposition is combined with epsilon-amino in lysine, Maillard reaction occurs, and non-enzymatic browning is caused to the low-lactose milk. A qualified product cannot be obtained.

Because lactose is decomposed into glucose and galactose in the processing process of the low-lactose milk, on one hand, sweetness is increased, and the low-lactose milk is endowed with good taste and flavor; on the other hand, the carbonyl group in a large amount of reducing sugar combines with the epsilon-amino group in lysine to undergo maillard reaction, resulting in non-enzymatic browning of the low-lactose milk.

The first step of the maillard reaction is the reaction of amino groups with carbonyl groups in an open chain form to produce Schiff's base, followed by Amadori molecular rearrangement to produce N-substituted-1 amino-1-deoxy-2-ketose, which is colorless and does not absorb light near the ultraviolet region, and as the reaction proceeds, the material enolizes to 1, 2-monoalkanol or 2, 3-enediol, which ultimately forms 5-Hydroxymethylfurfural (5-hydroxymethylfurfurfurral, 5-HMF) (indigenous, 2001), the accumulation of 5-HMF has a strong correlation with browning (Ferrer et al, 2000), since 5-HMF can be cleaved to form α -dicarbonyl compounds, which carbonyl compounds react with amines to produce melanoidines (Morale et al, 1992), which is an important factor in the reduction of the degree of browning of dairy and HMF production.

The present invention utilizes lactase hydrolysis to produce low lactose milk, and utilizes HPLC method (Morales et al, 1992) to determine the content of 5-HMF, the main intermediate of Maillard reaction, and is based on the analysis of the influence of different production conditions and different inhibitors on the content of 5-HMF in low lactose milk. In addition, the invention also aims at measuring the color difference of the low-lactose milk obtained under different sterilization conditions and hydrolysis degrees, and analyzes the relationship between the color difference and the content of 5-HMF.

[ summary of the invention]

The invention aims to provide a method for processing milk, which has the characteristic of low lactose, inhibits the browning generated when sugar is decomposed, and has clean and fresh flavor;

it is another object of the present invention to provide a low lactose milk without browning.

The technical scheme adopted by the invention for solving the technical problems is as follows:

taking a certain amount of milk, adding lactase into the milk under the conditions that the pH is 6.6-6.8 and the temperature is 8-9 ℃, wherein the dosage of the lactase is 0.5-0.75 per mill (parts by weight), and the enzymolysis time is 14-8 hours; preferably, the enzymolysis is carried out for 14 hours by using 0.5 per mill (weight part) of enzyme, or for 8 hours by using 0.75 per mill (weight part) of enzyme.

High-temperature enzymolysis can also be carried out, namely, the enzyme dosage is 0.5 per mill to 0.75 per mill (weight part) at 37 to 40 ℃, the time is 3 to 2 hours, preferably, the enzymolysis is carried out for 3 hours at 37 ℃ by using 0.5 per mill (weight part) of enzyme dosage, orthe enzymolysis is carried out for 2 hours at 40 ℃ by using 0.75 per mill (weight part) of enzyme dosage; the hydrolysis rate can reach more than 70 percent, and the hydrolysis speed is high;

during the sterilization process, the operating parameters were selected as follows: sterilizing at 138-140 deg.C for 4.5-3.5 s;

the inhibitor sodium sulfite or cysteine is added during the sterilization process.

Considering the cost and the hydrolysis rate, the lactose-reduced milk is produced in the actual production, the lactose does not need to be completely decomposed, and when the hydrolysis rate of the lactose in the lactose-reduced milk reaches 70 percent, the problem of lactose intolerance can be solved. When the hydrolysis rate is about 70%, the content of 5-HMF is low. Thus, the hydrolysis rate of the lactose-reduced milk can be controlled to reduce the production of 5-HMF while meeting production requirements.

[ description of the drawings]

FIG. 1 is a process flow diagram for producing a browning free low lactose milk by degrading lactose in milk with lactase;

FIG. 2 shows the change of hydrolysis rate in low temperature enzymolysis (8-10 ℃);

FIG. 3 shows the change of hydrolysis rate in high temperature enzymolysis (37-40 ℃);

FIG. 4 shows the peak appearance of the spectrum of 5-HMF by HPLC;

FIG. 5 is a linear relationship between 5-HMF content (C5-HMF) and peak area (Aera);

FIG. 6 is a graph of the effect of hydrolysis rate on 5-HMF content in lactose-reduced milk;

FIG. 7 is the effect of sterilization temperature on 5-HMF content;

FIG. 8 effect of inhibitors on 5-HMF content in lactose-reduced milk at different sterilization temperatures;

FIG. 9 effect of inhibitors on 5-HMF content in lactose-reduced milk at different hydrolysis rates;

FIG. 10 shows 5-HMF content and color difference (Δ L) including specular reflection^*、Δa^*And Δ b^*) The relationship of (1);

FIG. 11 shows 5-HMF content and color difference (. DELTA.L) when specular reflection is excluded^*、Δa^*And Δ b^*) The relationship (2) of (c).

[ detailed description]embodiments

The following examples are given to illustrate the present invention in conjunction with the accompanying drawings, but are not intended to limit the scope of the present invention.

In the low lactose milk production process shown in fig. 1, 5-HMF is mainly generated in the sterilization stage, where the high temperature conditions are the main factors causing maillard reaction;

in fig. 2, the lactose-reduced milk is produced at low temperature, and when the enzyme dosage is 0.1 per mill and 0.25 per mill, the hydrolysis rate is lower in 4-16 hours; the enzyme dosage is 0.5 per mill and 0.75 per mill, the hydrolysis rate rises faster and reaches more than 70 percent in 14 hours and 8 hours respectively;

in fig. 3, the lactose-reduced milk is produced under the high-temperature condition, when the enzyme dosage is 0.1 per mill and 0.25 per mill, the hydrolysis rate is lower in 1-5 hours; the enzyme dosage is 0.5 per mill and 0.75 per mill, the hydrolysis rate rises faster and reaches more than 70 percent after 3 hours and 2 hours respectively;

as can be seen from FIG. 4, when the retention time is about 3.1min, the peak areas of the a peak, the b peak and the c peak increase sequentially with the increase of the injection concentration, i.e., the peaks of the a, b and c are 5-HMF after HPLC analysis.

The concentration of the sample is taken as the abscissa and the peak area is taken as the ordinate, a standard curve of 5-HMF is made, and a linear relation between the concentration and the peak area is obtained, and the result is shown in FIG. 5. The content of 5-HMF is expressed as C5-HMF, the linear equation is Aera ═ 14363C5-HMF +2.1617, and the correlation between the two is 99.89%.

After the pretreated sample to be detected is detected by an HPLC method, a peak area is obtained, and then the content of the 5-HMF in the sample can be obtained by calculation according to a standard curve shown in figure 5.

In the production process of the low-lactose milk, the content of reducing sugar is increased along with the increase of the hydrolysis rate. The effect of hydrolysis rate on 5-HMF content in post-sterilized lactose-reduced milk with sterilization at 139 ℃ for 4s is shown in figure 6.

As can be seen in FIG. 6, as the hydrolysis rate increased, the 5-HMF content increased in the lactose-reduced milk. The inventors have found that lactose intolerance can be resolved when the hydrolysis rate of lactose in low-lactose milk reaches 70%. As is clear from FIG. 6, the content of 5-HMF was low when the hydrolysis rate was about 70%. Thus, the hydrolysis rate of the lactose-reduced milk can be controlled to reduce the production of 5-HMF while meeting production requirements.

In the process of producing the low-lactose milk, the enzymolysis liquid needs to be treated at high temperature after the enzymolysis is finished, so as to achieve the purposes of enzyme deactivation and sterilization, thereby prolonging the shelf life. And the most prone to maillard reactions is the sterilization stage. Under high temperature sterilization conditions, the reducing sugars contained in the lactose-reduced milk react with the amino acid residues of the proteins to produce the intermediate 5-HMF of the maillard reaction. The effect of different sterilization temperatures and incubation times on the 5-HMF content of the lactose-reduced milk is shown in fig. 7.

As shown in fig. 7, both the sterilization temperature and time have an effect on the content of 5-HMF. The higher the sterilization temperature is, the more 5-HMF content is produced by the low-lactose milk; the longer the sterilization time, the higher the 5-HMF content. When producing the long-shelf-life sterilized milk, the actual production is performed by ultra-high temperature sterilization at 139 ℃, 4s or 135 ℃ and 15s, and as can be seen from fig. 7, when the sterilization conditions are 139 ℃ and 4s, the content of the generated 5-HMF is less.

It can be seen from figure 8 that at all sterilization temperatures, the 5-HMF content of the lactose-reduced milk after addition of the inhibitor was lower than the 5-HMF content of the lactose-reduced milk without any inhibitor added, even though the sterilization time was longer (15 s). After adding the inhibitor sodium sulfite or cysteine, the content of 5-HMF is less influenced by the sterilization temperature, but the effect of inhibiting the generation of 5-HMF by the cysteine is better.

The inventor analyzes the influence of the addition of the inhibitor on the content of 5-HMF in the lactose-reduced milk with different hydrolysis rates under the sterilization condition of 139 ℃ and 4s, and the result is shown in FIG. 9. As shown in FIG. 9, the 5-HMF content of the lactose reduced milk with differenthydrolysis rates was lower than that of the lactose reduced milk without any inhibitor added. As the hydrolysis rate increases, the increase of 5-HMF in the lactose-reduced milk after adding the inhibitor is lower than that of the product without the inhibitor, and cysteine has better effect of inhibiting the generation of 5-HMF under all conditions of the hydrolysis rate.

As shown in fig. 10, when specular reflection is included, the luminance value Δ L^*The color of the lactose-reduced milk gradually deepens with the increase of the content of 5-HMF, and the color change can be observed by naked eyes. 5-HMF content and Δ L^*There is a binomial relationship between them, and the 5-HMF content is expressed as C5-HMF, Δ L^*And C5-HMF is: Δ L^*The correlation reaches 99.44 percent when the molecular weight is-0.004 (C5-HMF)2-0.3154C5-HMF + 0.1381. And the redness value Deltaa^*And yellowness index Δ b^*Increasing with increasing 5-HMF content. Δ a^*And C5-HMF as Δ a^*The relativity of-0.0027 (C5-HMF)2+0.2697C5-HMF-0.1581 reaches 99.07%. Δ b^*And C5-HMF as Δ b^*0.0036(C5-HMF)2+0.2369C5-HMF-0.5693 with a correlation of 94.91%.

As shown in FIG. 11, the 5-HMF content and the color difference (. DELTA.L) were obtained while eliminating the specular reflection^*、Δa^*And Δ b^*) The same trend exists as when specular reflection is involved. Brightness value DeltaL^*Decreases with increasing 5-HMF content, the mathematical relationship between the two being Δ L^*The correlation reaches 99.58 percent when the molecular weight is-0.0058 (C5-HMF) 2-0.3129C 5-HMF + 0.1389. Red value delta a^*And yellowness index Δ b^*Increasing with increasing 5-HMF content. Δ a^*And C5-HMF as Δ a^*-0.0024(C5-HMF)2+0.2854C5-HMF-0.1671 with a correlation of 99.15%. Δ b^*And C5-HMF as Δ b^*0.0063(C5-HMF)2+0.2371C5-HMF-0.6319 with a correlation of 95.56%.

From the above analysis, it can be seen that the 5-HMF content in the low-lactose milk is different from its color difference (. DELTA.L)^*、Δa^*And Δ b^*) A binomial relationship exists. No matter the detection process is carried out, whether the specular reflection of the cuvette exists or not, the brightness value delta L of the lactose-reduced milk^*The redness value Delta a decreases with increasing 5-HMF content^*And yellowness index Δ b^*Both increase with increasing 5-HMF content.

In order to clarify the relationship between the 5-HMF content and the color difference in the low-lactose milk, the inventor detected the color difference (Delta L) in the case of different 5-HMF contents^*、Δa^*And Δ b^*) While the mathematical relationship between 5-HMF content and color difference was analyzed. FIG. 10 shows 5-HMF content and color difference (Δ L) including specular reflection^*、Δa^*And Δ b^*) FIG. 11 shows the 5-HMF content and color difference (. DELTA.L) when specular reflection is excluded^*、Δa^*And Δ b^*) The relationship (2) of (c).

Example 1

HPLC method for detecting 5-HMF

In the invention, the content of 5-HMF in milk is measured by an HPLC method. Three 5-HMF standards of different concentrations (1.1088. mu. mol/ml, 3.3264. mu. mol/ml, 6.6528. mu. mol/ml) were taken and analyzed by HPLC to determine the absorption at 280nm, in a sample volume of 20. mu.l.

Example 2

Relationship between 5-HMF content and color difference in low-lactose milk

The inventors analyzed the 5-HMF content of the lactose-reduced milk as a function of color difference to verify the feasibility of using the assay for 5-HMF content to monitor browning of the lactose-reduced milk.

Milk was hydrolyzed using lactase, samples were taken at 52.1%, 68.7%, 69.6% and 76.1% degrees of hydrolysis, respectively, and the resulting samples at different hydrolysis rates were subjected to two treatments: sterilizing at 85 deg.C for 15min and 121 deg.C for 10min, and determining 5-HMF content and color difference (Δ L) of each sample_*、Δa_*And Δ b_*). The detection of color difference under two sterilization conditions respectively takes raw milk corresponding to the sterilization conditions as a standard sample. Sterilizing raw milk at 85 deg.CAfter 15min, L^*＝76.81，a^*＝-2.11，b^*4.36; sterilizing raw milk at 121 deg.C for 10min, and collecting the milk^*＝73.02，a^*＝1.0，b^*10.10. The content of 5-HMF in the low lactose sample obtained after enzymatic hydrolysis and the colour difference results are given in table 1:

TABLE 1 5-HMF and color difference values in lactose-reduced milk of different degrees of hydrolysis under two sterilization conditions

Rate of hydrolysis (％)		52.1	68.7	69.6	76.1
Rate of hydrolysis (％)		52.1	68.7	69.6	76.1	Sterilizing at 85 deg.C 15min	5-HMF containing Amount (μ g/ml)	0.573 9	1.0125	1.1691	1.8654
ΔL^* Δa^* Δb^*	-0.11 -0.04 -0.16	-0.15 -0.02 -0.15	-0.17 -0.08 -0.31	-0.25 -0.06 -0.28			5-HMF containing Amount (μ g/ml)	0.573 9	1.0125	1.1691	1.8654
ΔL^* Δa^* Δb^*	-0.11 -0.04 -0.16	-0.15 -0.02 -0.15	-0.17 -0.08 -0.31	-0.25 -0.06 -0.28	121 ℃ C Bacteria for 10min		5-HMF containing Amount (μ g/ml)	15.6547	18.3782	20.5214	22.0789
ΔL^* Δa^* Δb^*	-7.39 3.88 5.44	-8.11 4.28 6.0	-8.84 4.51 6.8	-8.91 4.52 6.12			5-HMF containing Amount (μ g/ml)	15.6547	18.3782	20.5214	22.0789

As shown in Table 1, the 5-HMF content of the lactose-reduced milk was much higher than that of the milk sterilized at low temperature (85 ℃ for 15min) under the high temperature sterilization (121 ℃ for 10min), and the brightness value Δ L was also higher^*Much lower than the value at low temperature sterilization. It can be seen that the lactose-reduced milk products have a darker color when sterilized at high temperatures, with the same hydrolysis rate.

Using the same method, the 5-HMF content and color difference were analyzed for lactose-reduced milk with a hydrolysis rate of 68.1% under different sterilization conditions, as shown in Table 2.

TABLE 2 5-HMF content and color difference in lactose-reduced milk under different sterilization conditions

Sterilization temperature (. degree.C.) Time (min)		85～90℃ 15 min	95～ 100℃ 15min	110℃ 10min	121℃ 10min
Sterilization temperature (. degree.C.) Time (min)		85～90℃ 15 min	95～ 100℃ 15min	110℃ 10min	121℃ 10min	Low lactose milk (DH＝ 68.1％)	5-HMF content (μg/ml)	1.8654	2.0315	13.6835	22.078 9
ΔL^* Δa^* Δb^*	-0.11 -0.04 -0.16	-0.15 -0.02 -0.15	-0.17 -0.08 -0.31	-0.25 -0.06 -0.28			5-HMF content (μg/ml)	1.8654	2.0315	13.6835	22.078 9

As can be seen from Table 2, the increased sterilization temperature increased the 5-HMF content of the lactose reduced milk and the lactose reduced milk product darkened in color.

As can be seen from tables 1 and 2, the 5-HMF content of the lactose-reduced milk varies greatly under different processing conditions, and the color difference varies with the 5-HMF content.

Example 3

The main apparatus is as follows: Shimadzu-HPLC, SPD-10AVP/10AVVP UV-visible detector, DGU-12A automatic degasser, and Rite SP62 spectrophotometer

Reagent: lactase (EC 3.2.1.23), 5-hydroxymethylfurfural (5-HMF, Sigma), methanol (Romil Chemicals, chromatographically pure), crystalline sodium acetate, acetic acid, trichloroacetic acid, oxalic acid, the inhibitor sodium sulfite and cysteine were all analytically pure, double distilled water.

Determination of lactose hydrolysis Rate

The lactose hydrolysis rate is determined by enzyme catalysis and by using a kit.

The principle is as follows: after one molecule of lactose in milk is hydrolyzed by lactase, one molecule of glucose and one molecule of galactose are generated, so that the glucose content in milk can be specifically detected by using a glucose oxidase-peroxidase method, and the hydrolysis rate of lactose can be known. Glucose is oxidized by glucose oxidase to generate gluconic acid and hydrogen peroxide, the hydrogen peroxide is further oxidized by oxidase to release nascent oxygen, the oxygen can oxidize colorless 4-aminoantipyrine (reduced type) into red quinoid compound (oxidized type) in the presence of phenol, the substance has maximum light absorption value at 505nm, and the shade of the color is in direct proportion to the glucose content in the sample. The reaction conditions are 37 ℃ and 15min, and the reaction process can be represented by the following formula:

the glucose content and lactose hydrolysis rate in the sample were calculated as follows:

glucose content (g/L) × (measurement tube absorbance/standard tube absorbance) × standard concentration in the sample

Lactose hydrolysis ratio (%) - (2 × glucose content in sample)/lactose content × 100%

Example 4

Determination of the conditions of the enzymatic hydrolysis

Lactose is hydrolyzed using lactase (EC 3.2.1.23) to produce a lactose-reduced milk. Simulating production conditions, performing low-temperature enzymolysis (8-10 ℃) and high-temperature enzymolysis (37-40 ℃), wherein the pH value is 6.6-6.8, and the enzyme dosage is 4 concentrations: 0.1%, 0.25%, 0.5%, 0.75%. Monitoring the change of the hydrolysis rate in 4-16 hours in the low-temperature enzymolysis process and the change of the hydrolysis rate in 1-5 hours in the high-temperature enzymolysis process, and then determining the enzyme dosage and the enzymolysis time.

Determination of 5-HMF content

The 5-HMF content was determined by HPLC (Morales et al, 1992).

The chromatographic conditions were as follows:

a chromatographic column: resolve C18 chromatography column (150 mm. times.4.0 mm, Daliyitet scientific instruments, Inc.)

Mobile phase: 0.1M pH3.8 sodium acetate buffer: methanol 92: 10

Detection wavelength: ultraviolet detector with wavelength of 280nm

Sample introduction amount: 20 μ l

Preparation of a standard solution: firstly, 0.056g of 5-HMF standard substance is dissolved, the volume is determined to 200ml to prepare stock solution, then 0.1ml, 0.3ml and 0.6ml of stock solution are respectively taken, 5ml of 0.15M oxalic acid, 3ml of 40 percent TCA and 10ml of 4 percent TCA are added, and then the volume is determined to 25 ml.

The sample pretreatment method refers to Ferrer (2000), and the specific flow is as follows: 5ml of 0.15M oxalic acid solution was added to 15ml of milk, mixed well, and heated in boiling water for 25 min. After the mixture was cooled to room temperature, 3ml of 40% TCA was added, shaken well, centrifuged (2000 Xg, 15min) and the supernatant collected. 10ml of 4% TCA was added to the centrifugation precipitate, mixed well and centrifuged (2000 Xg, 15min) to collect the supernatant. The supernatants from both centrifugations were combined, the volume was determined and then passed through a microfiltration membrane (0.45 μm), and the filtrate was assayed by HPLC.

Example 5

Color difference detection

The lactase is used for preparing the low-lactose milk, and the dosage of the lactase is 0.5 per mill.

The color difference of the resulting lactose-reduced milk samples was determined using a Rite SP62 spectrophotometer, USA. The method comprises the following steps: placing the spectrophotometer in a differential display mode, and then calibrating with a white standard; and (3) injecting the sample standard into a colorimetric pool, placing the colorimetric pool on a special colorimetric frame, firstly measuring the color difference of the standard sample, and then measuring the color difference of the sample by using the same method. By CIE L^*a^*b^*Is the tolerance mode for chromatic aberration of the sample (Bertelli et al, 1996), L^*Is a brightness value, a^*Red value, b^*Is a yellowness index, L^*、a^*And b^*The change in (c) is calculated as follows:

ΔL^*＝L^*-L^*0(L^*is the sample brightness value, L ^*0 is the brightness value of the standard sample

Δa^*＝a^*-a^*0(a^*Is the sample redness value, a^*0 is red value of standard sample)

Δb^*＝b^*-b^*0(b^*Is the yellowness index of the sample, b ^*0 is a yellowness index of a standard sample

In the results obtained, if Δ L^*If the sample brightness value is positive, the sample brightness value is higher than that of the standard sample, and the color is light; if Δ L^*Negative indicates that the sample is lower in brightness value and darker in color than the standard sample.

Example 6

Taking a certain amount of milk, adding lactase into the milk under the conditions that the pH is 6.6 and the temperature is 9 ℃, wherein the enzyme dosage is 0.5 per mill (part by weight), and the enzymolysis time is 14 hours; during the sterilization process, the operating parameters were selected as follows: sterilized at 139 ℃ for 4 s.

Example 7

Taking a certain amount of milk, adding lactase into the milk under the conditions that the pH is 6.8 and the temperature is 9 ℃, wherein the enzyme dosage is 0.75 per mill (parts by weight), and the enzymolysistime is 8 hours; during the sterilization process, the operating parameters were selected as follows: sterilized at 138 ℃ for 4.5 s.

Example 8

A method for inhibiting browning of low lactose milk, comprising: taking a certain amount of milk, adding lactase into the milk under the conditions that the pH is 6.8 and the temperature is 8 ℃, wherein the enzyme dosage is 0.75 per mill (parts by weight), and the enzymolysis time is 8 hours; during the sterilization process, the operating parameters were selected as follows: sterilizing at 140 deg.C for 4.5 s.

Example 9

A method for inhibiting browning of low lactose milk, comprising: taking a certain amount of milk, adding lactase into the milk under the conditions that the pH is 6.6 and the temperature is 37 ℃, wherein the enzyme dosage is 0.75 per mill (parts by weight), and the enzymolysis time is 2 hours; during the sterilization process, the operating parameters were selected as follows: sterilized at 139 ℃ for 4 s.

Example 10

A method for inhibiting browning of low lactose milk, comprising: taking a certain amount of milk, adding lactase into the milk under the conditions that the pH is 6.6 and the temperature is 40 ℃, wherein the enzyme dosage is 0.5 per mill (part by weight), and the enzymolysis time is 14 hours; during the sterilization process, the operating parameters were selected as follows: sterilized at 139 ℃ for 4 s.

Example 11

A method for inhibiting browning of low lactose milk, comprising: taking a certain amount of milk, adding lactase into the milk under the conditions that the pH is 6.8 and the temperature is 40 ℃, wherein the enzyme dosage is 0.5 per mill (part by weight), and the enzymolysis time is 14 hours; during the sterilization process, the operating parameters were selected as follows: sterilized at 139 ℃ for 4 s. The invention has the following effects:

after a large number of experiments, the inventor obtains the optimal parameters through the selection of parameters, enzymolysis time and parameters, sterilization temperature and hydrolysis rate and the selection of an inhibitor, so that browning is well inhibited in the process of preparing the low-lactose milk, and the expected effect can be achieved.

Claims

1. A method for inhibiting browning of low lactose milk, comprising: taking a certain amount of milk, adding lactase into the milk under the conditions that the pH is 6.6-6.8 and the temperature is 8-9 ℃, wherein the dosage of the lactase is 0.5-0.75 per mill (parts by weight), and the enzymolysis time is 14-8 hours; during the sterilization process, the operating parameters were selected as follows: sterilizing at 138-140 deg.C for 4.5-3.5 s.

2. The method of inhibiting browning of lactose-reduced milk according to claim 1 wherein the inhibitor sodium sulfite or cysteine is added during sterilization.

3. The method for inhibiting browning of low-lactose milk according to claim 1 or 2, wherein the amount of lactase is 0.5-0.75 per mill (parts by weight) under the enzymolysis condition of 37-40 ℃, and the enzymolysis time is 3-2 hours.

4. The method of inhibiting browning of a lactose-reduced milk according to claim 3, wherein said enzymatic hydrolysis conditions are 40 ℃, the lactase is used in an amount of 0.75% o by weight, and the enzymatic hydrolysis time is 2 hours.

5. The method of inhibiting browning of a lactose-reduced milk according to claim 3, wherein said enzymatic hydrolysis conditions are 37 ℃, the lactase is used in an amount of 0.5% by weight, and the enzymatic hydrolysis time is 3 hours.

6. A method of inhibiting browning of lactose-reduced milk according to claim 1 or 3 wherein the sterilization is carried out at 139 ℃ for 4 s.

7. A non-browning, low-lactose milk, characterised in that it is produced by a method according to any one of claims 1 to 6.