CN113848290A - Method for detecting DHA or ARA in milk powder - Google Patents

Method for detecting DHA or ARA in milk powder Download PDF

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CN113848290A
CN113848290A CN202110691836.0A CN202110691836A CN113848290A CN 113848290 A CN113848290 A CN 113848290A CN 202110691836 A CN202110691836 A CN 202110691836A CN 113848290 A CN113848290 A CN 113848290A
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sample
dha
ara
unit
milk powder
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赵红霞
刘彪
李威
孔小宇
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Inner Mongolia Yili Industrial Group Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/02—Food
    • G01N33/04—Dairy products
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G01N1/44—Sample treatment involving radiation, e.g. heat
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
    • G01N30/02—Column chromatography
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
    • G01N30/02—Column chromatography
    • G01N30/04—Preparation or injection of sample to be analysed
    • G01N30/06—Preparation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
    • G01N31/16—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using titration
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/02—Food
    • G01N33/04—Dairy products
    • G01N33/06—Determining fat content, e.g. by butyrometer
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N5/00—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
    • G01N30/02—Column chromatography
    • G01N2030/022—Column chromatography characterised by the kind of separation mechanism
    • G01N2030/025—Gas chromatography

Abstract

The invention provides a method for detecting DHA or ARA in milk powder, which comprises an acceleration processing step and a detection step; wherein the accelerating treatment step comprises the step of accelerating treatment of the milk powder at 37-45 ℃; the time of the accelerated treatment is 1/n of the shelf life of the milk powder, and n is more than or equal to 3 and less than or equal to 5. By the method, the feasibility of the DHA and ARA produced by a new manufacturer or a new method in the use of the milk powder can be verified in a short time.

Description

Method for detecting DHA or ARA in milk powder
Technical Field
The invention belongs to the technical field of milk powder production and processing, and particularly relates to a detection method of DHA or ARA in milk powder.
Background
DHA (docosahexaenoic acid) and ARA (eicosapentanoic acid) are two unsaturated fatty acids which are naturally present in breast milk and are important for infant development, and have a wide range of physiological activities in the human body. Is an important component of the brain and retina of infants, is considered as an essential nutrient for the early development of human beings, and is very important for the development of infants. Feeding infant formula supplemented with DHA and ARA is started in the first week after birth, which is beneficial for the visual, motor and cognitive development of the infant. Numerous research reports have shown that DHA and ARA are beneficial for the growth of infants, such as the development of the central nervous system, the development of the retina, the development of intelligence, cognitive and problem solving abilities, the development of the vasculature and the development of the immune system. Infants fed with milk supplemented with DHA and ARA all showed better visual accuracy, better performance in problem solving tests and higher scores in neurodevelopmental tests than infants fed with ordinary milk. Adults can generally synthesize DHA and ARA by chain elongation and desaturation using other fatty acids in the diet (e.g., linoleic and linolenic acids), but the desaturase activity required for the self-synthesis of these two fatty acids in infants is so low that it does not meet the nutritional requirements for growth and development. In order to obtain sufficient DHA and ARA, the fetus is obtained from the mother through the placenta, the milk contains DHA and ARA for the infant after birth, and the infant can be obtained through breast feeding, but for the infant which is not breast-fed, the infant milk powder containing DHA and ARA needs to be fed for the growth and development of the infant.
Usually, the two long-chain polyunsaturated fatty acids are strengthened in infant formula milk powder of each brand, DHA and ARA are embedded by microcapsules, and embedding materials are different from manufacturers to manufacturers, so that the DHA and ARA provided by different manufacturers have different use conditions in the milk powder. The unqualified DHA and ARA are easy to oxidize and deteriorate in the shelf life of the milk powder, volatilize fishy smell, seriously affect the taste and smell of the milk powder, not only seriously affect the sensory quality of the milk powder, but also can not meet the daily requirements of infants due to the reduction of the DHA and ARA contents. Therefore, when a new manufacturer or a new method is used to produce DHA and ARA materials for the first time, it is necessary to verify the change of the DHA and ARA materials in the milk powder during the shelf life of the milk powder to determine whether the quality standards of the products are met.
At present, the application condition of DHA and ARA produced by a new manufacturer or a new method in milk powder is mainly considered by a tracking analysis method, namely, a milk powder sample added with new DHA or ARA is placed at room temperature, sensory evaluation, DHA or ARA content, surface oil and peroxide value are carried out at regular intervals, the change condition of each index in the shelf life of the milk powder is tracked and analyzed, and whether the milk powder meets the quality standard is judged. As the shelf life of the infant milk powder is generally 18-24 months, the method is used for verifying the feasibility of new raw materials, the period is too long, the consumed manpower and material resources are large, the subjectivity is strong, the DHA and AA raw materials produced by a new manufacturer or a new method are not favorably applied, and a systematic research method of the DHA and ARA produced by the new manufacturer or the new method on the application condition of the milk powder is not reported. Therefore, it is necessary to establish a method for rapidly verifying the application of DHA and ARA in milk powder.
Disclosure of Invention
The invention aims to provide a detection method of DHA or ARA in milk powder, which can verify the feasibility of DHA and ARA produced by a new manufacturer or a new method in the use of the milk powder in a short time.
In order to achieve the aim, the invention provides a method for detecting DHA or ARA in milk powder, which comprises an acceleration processing step and a detection step; wherein the accelerating treatment step comprises the step of accelerating treatment of the milk powder at 37-45 ℃; the time of the accelerated treatment is 1/n of the shelf life of the milk powder, and n is more than or equal to 3 and less than or equal to 5.
According to some embodiments of the invention, the DHA or ARA is in the form of a microencapsulated powder.
According to some embodiments of the present invention, the detection method specifically comprises a monomer experiment and a powder mixing experiment; wherein the monomer experiment is carried out by accelerating the treatment of a monomer DHA or ARA sample to detect the DHA or ARA content, the surface oil and the peroxide value in the monomer DHA or ARA sample; the powder mixing experiment is to detect the taste and smell in the mixed product by mixing the monomer DHA or ARA sample with the milk powder into the mixed product and then carrying out accelerated treatment.
According to some embodiments of the invention, the monomer experiment comprises the steps of: evenly subpackaging the monomer DHA or ARA samples into unit samples according to the mass, taking one unit sample as an initial unit sample, and storing the rest unit samples at the constant temperature of 37-45 ℃; every 20 days, a unit sample preserved at constant temperature is taken, and the DHA or ARA content, the surface oil and the peroxide value are detected.
According to some embodiments of the present invention, the mixing experiment comprises the following steps: respectively dry-mixing a monomer DHA or ARA sample with milk powder according to a formula of the milk powder to obtain a mixed sample, and meanwhile, dry-mixing a corresponding standard DHA or standard ARA sample with the milk powder to obtain a standard mixed product; respectively subpackaging the mixed sample and the standard mixed sample into a unit mixed sample and a unit standard mixed sample according to the average mass, taking one unit mixed sample and one unit standard mixed sample as an initial unit mixed sample and an initial unit standard mixed sample, and storing the rest unit mixed sample and the unit standard mixed sample in a 37-45 ℃ thermostat; and respectively taking one pack of the unit mixed sample and one pack of the unit standard mixed sample from the constant temperature box every one month, storing at-18 ℃, and comparing the flavors of the mixed sample and the standard mixed sample after the accelerated treatment is finished.
According to some embodiments of the invention, the initial unit sample, the initial unit mixed sample and the initial unit standard mixed sample are corresponding samples stored at-18 ℃.
According to some embodiments of the invention, the method for detecting the DHA or ARA content comprises the following steps: (1) dissolving a monomer DHA or ARA sample by using an organic solvent, extracting and collecting the obtained extracting solution, continuously concentrating, and fixing the volume to obtain a pretreated sample; (2) esterification: adding an alkali alcoholic solution into the pretreated sample for esterification treatment; (3) DHA and ARA content was determined by external calibration.
According to some embodiments of the invention, the surface oil is calculated by the formula:
Figure BDA0003127082640000031
according to some embodiments of the invention, the method for detecting a DHA or ARA peroxidation value comprises the steps of: (1) dissolving a monomer DHA or ARA sample by using an organic solvent, extracting and collecting the obtained extracting solution, and continuously evaporating the extracting solution to dryness to obtain a pretreated sample; (2) and (3) obtaining the DHA or ARA peroxidation value of the pretreatment sample through a titration method and a calculation formula.
According to some embodiments of the present invention, the titration method comprises dissolving the pretreated sample, adding saturated potassium iodide solution, shaking, adding indicator and titrating.
According to some embodiments of the invention, the DHA or ARA peroxidation value is calculated by the formula: x ═ V1-V2 × C × 0.1269/M × 100 × 78.8
Wherein, in the above formula, X: peroxide value of the sample in milliequivalents per kilogram of fat (meq/kg); v1: sample consumption sodium thiosulfate standard titration solution volume in milliliters (mL); v2: reagent blank the volume of sodium thiosulfate standard titration solution in milliliters (mL) was consumed; c: the concentration of a standard titration solution of sodium thiosulfate in moles per liter (mol/L); m: fat mass in grams (g).
The invention adopts a method of accelerated treatment with the quality guarantee period of 1/4 to verify the use condition of DHA/ARA of a new manufacturer or a new production method. The verification time of the method of the invention can be completed within 5-6 months generally, while the prior method requires 20-25 months generally, therefore, when verifying DHA/ARA of a new manufacturer or a new production method, the feasibility of the method can be predicted within a short time.
Drawings
FIG. 1 shows a bar chart comparing the flavor of infant milk samples with the addition of new DHA and standard DHA according to example 1 of the present invention;
FIG. 2 shows a bar graph comparing the flavor of the infant milk powder samples with the addition of new DHA and standard DHA according to example 2 of the present invention;
FIG. 3 shows a bar chart comparing the flavor of the infant milk samples with the addition of new ARA and standard ARA according to example 3 of the present invention.
Detailed Description
Technical features, objects and advantages of the present invention will be more clearly understood and appreciated by those skilled in the art. It should be understood that the following detailed description is merely exemplary, and the technical solution of the present invention is not limited to the specific embodiments listed below.
The invention aims to provide a method for detecting DHA or ARA in milk powder, which can verify the feasibility of DHA and ARA produced by a new manufacturer or a new method in the use of the milk powder in a short time.
Therefore, the invention provides a method for detecting DHA or ARA in milk powder, which comprises an acceleration processing step and a detection step; wherein the accelerating treatment step comprises accelerating treatment of milk powder at 37-45 deg.C, preferably 42 deg.C; the time of the accelerated treatment is 1/4 of the shelf life of the milk powder.
The method for accelerating the treatment is based on a Schhal oven test method, according to an Arrhenius empirical formula, for a normal chemical reaction, the reaction temperature rises by 1 time every 10 ℃, and the reaction speed rises by 1 time (K [ T +10 ℃)/K [ T ] ═ 2, K is a reaction speed constant, and the speed constant is inversely proportional to the shelf life of the food, namely the longer the reaction speed constant K is, the shorter the shelf life is (N [ T ]/N [ T +10 ℃) ] ═ 2, N is the shelf life), therefore, the relationship between the temperature and the shelf life coefficient can be further obtained, and the oxidation stability test is carried out by the SchARAl oven method, so that the fact that the storage at 42 ℃ for 1 day is equivalent to the storage at the room temperature of 22 ℃ for 4 days, therefore, the method for accelerating the quality guarantee period 1/4 is adopted to verify the feasibility of using DHA/ARA in the milk powder.
According to a particular embodiment, the DHA or ARA are both in the form of a microcapsule powder.
According to a specific embodiment, the detection method specifically comprises a monomer experiment and a powder mixing experiment; wherein the monomer experiment is carried out by accelerating the treatment of a monomer DHA or ARA sample to detect the DHA or ARA content, the surface oil and the peroxide value in the monomer DHA or ARA sample; the powder mixing experiment is to detect the taste and smell in the mixed product by mixing the monomer DHA or ARA sample with the milk powder into the mixed product and then carrying out accelerated treatment.
According to a specific embodiment, the monomer experiment specifically comprises the following steps: 1) the monomer DHA or ARA sample is divided into 10 portions of 200 g small packages (unit samples). 2) 9 parts of the subpackaged monomer DHA or ARA sample are placed in a constant temperature and humidity box (the humidity is 65 +/-2%) with the temperature of 37-45 ℃ (preferably 42 ℃), the shelf life is 1/4, the accelerated treatment of the shelf life is 1/4, namely the number of days for sealing and storing the sample in the constant temperature and humidity box with the temperature of 42 ℃, the number of days is the number of days per 4 of the shelf life of milk powder, and 1 part of the sample is taken as an initial unit and is placed in a refrigerator with the temperature of 18 ℃ below zero. 3) Taking a pack of samples (unit samples) from the constant-temperature and constant-humidity box every 20 days, detecting DHA or ARA content, surface oil and peroxide value, and judging and analyzing the detection results of the initial samples and the samples subjected to accelerated treatment after the accelerated treatment of the quality guarantee period 1/4 is finished.
According to a specific embodiment, the powder mixing experiment specifically comprises the following steps: 1) according to the formula, respectively dry-mixing a monomer DHA or ARA sample with milk powder to obtain a mixed sample, meanwhile, dry-mixing a corresponding standard DHA or standard ARA sample with milk powder to obtain a standard mixed product, and then respectively subpackaging into 400 g packages. 2) Marking the subpackaged samples (unit mixed sample and unit standard mixed sample), putting the marked samples into a constant temperature and humidity box with the temperature of 37-45 ℃ (preferably 42 ℃) for accelerated treatment of the quality guarantee period 1/4, taking one unit mixed sample and one unit standard mixed sample as an initial unit mixed sample and placing the initial unit standard mixed sample in a refrigerator with the temperature of 18 ℃ below zero. 3) And respectively taking a unit mixed sample and a unit standard mixed sample from a constant-temperature constant-humidity box every one month, putting the unit mixed sample and the unit standard mixed sample into a refrigerator at the temperature of 18 ℃ below zero, and comparing the flavors of the mixed sample and the standard mixed sample by an organizer after the accelerated treatment of the quality guarantee period 1/4 is finished.
In conclusion, the method adopts the method of accelerated treatment with the quality guarantee period 1/4 to verify the use condition of DHA/ARA of a new manufacturer or a new production method. The verification time of the method of the invention can be completed within 5-6 months generally, while the prior method requires 20-25 months generally, therefore, when verifying DHA/ARA of a new manufacturer or a new production method, the feasibility of the method can be predicted within a short time.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments.
The methods used in the following examples are conventional methods unless otherwise specified, and the reagents used are commercially available reagents unless otherwise specified.
The specific method for detecting the DHA or ARA content, the surface oil and the peroxide value in the monomer DHA or ARA sample according to the embodiment of the invention is as follows:
1/4 accelerated processing method verification test
The researchers of the invention use SchARA1 oven method to obtain the concrete steps of adopting quality guarantee period 1/4 accelerated treatment method as follows:
set up DHA, the accelerated experiment of ARA under the different temperatures, the temperature of accelerated experiment sets up to 7 temperatures, and humidity sets up to 65 +/-2%, and different temperatures and specific humidity are realized with constant temperature and humidity oven, see specifically table 1, and the sample that stores under each temperature is once got every 10 days, and when the experimental sample had one or more index detection nonconformities, made the early warning, if the sample is also unqualified next time, just ended the experiment under this temperature condition. Meanwhile, the experiment of DHA and ARA under normal temperature conditions is set, samples are taken once every 20 days, and the experiment is finished in two years (24 months).
TABLE 1
Figure BDA0003127082640000061
After the normal temperature and the accelerated experiment are finished, summarizing all detection data, analyzing and comparing the characteristic index detection result of the DHA under different accelerated temperature conditions with the data under the normal temperature condition, and finding out a certain accelerated storage temperature and storage time which are closest to the sensory quality change and the DHA content, surface oil and peroxide value change under the normal temperature condition, wherein the accelerated temperature and the storage time can replace the temperature and time conditions of the normal temperature experiment.
From the sensory evaluation results, the DHA sample is seriously damaged after the acceleration at the temperature of 57 ℃ and the acceleration at the temperature of 62 ℃, the original characteristics of the sample are avoided, and the experimental results at the temperature of 57 ℃ and the temperature of 62 ℃ can only be used as the reference for quickly judging the taste and smell in the quality guarantee period of the raw materials, so that the sensory evaluation can not be used as the judgment index for ending the experiment.
Whether the DHA raw material meets the quality standard requirements during the experiment period or not needs to be judged by combining with other three detection results.
The sensory evaluation method for detecting DHA and ARA comprises the following steps:
the initial sample and the sample taken during the experiment were bagged and their odor was analyzed by comparison to the change in odor of the sample during the experiment, and the sensory evaluation was performed by the same person to avoid errors.
The color of the DHA sample at different temperatures and time points is gradually deepened along with the rise of the temperature, the sample is early warned when the sample is faint yellow, and the sample is judged to be unqualified after the sample is deepened to yellow. The odor change has a similar rule, the initial sample has the peculiar fishy smell of DHA and has no peculiar smell, the change of the fishy smell of the sample is not large in the acceleration process, but the peculiar smell of the sample is increased along with the time extension, and the peculiar smell comprises oxidized smell, rancid smell, burnt smell and the like.
Detection of DHA or ARA content
The detection method of the DHA or ARA content comprises the following steps: (1) sample treatment: 1.00g of the sample was accurately weighed into a 250mL flat-bottomed flask, dissolved in 10mL of 65 ℃ distilled water, and shaken up. Adding 2.5mL ammonia water with volume fraction of 25%, shaking, placing in 65 deg.C water bath, refluxing for 15-20min, reacting completely, taking out, and cooling to room temperature. The solution was transferred to a 125mL separatory funnel, the flask was rinsed twice with 10mL of ethanol, similarly transferred to a 125mL separatory funnel, and the flask was rinsed twice with 25mL of diethyl ether, and the rinses were combined with the solution. And (4) covering a plug, oscillating for 1min, adding 25mL of petroleum ether, plugging the plug, shaking for 1min, and standing for layering. The aqueous phase was transferred to a 250mL beaker and the organic phase was transferred to a 250mL separatory funnel. The aqueous phase was transferred to a 125mL separatory funnel and the 2 nd extraction was performed according to the above procedure using 5mL ethanol, 15mL diethyl ether, and 15mL petroleum ether, respectively. No ethanol was added for the 3 rd extraction, but 15mL of diethyl ether and 15mL of petroleum ether were used, as above. The organic phases were combined, washed to neutrality with distilled water, dried over anhydrous sodium sulfate, evaporated to dryness on a rotary evaporator at 40 ℃ under a stream of nitrogen, transferred to a 10mL volumetric flask with n-hexane and brought to volume for further use. (2) Methyl esterification: accurately sucking 2mL of the processed sample solution into a 10mL finger-shaped bottle with a cover, adding 0.5mL of 4mol/L potassium hydroxide methanol solution, oscillating for 2min, standing for 10min, and testing. (3) The DHA and ARA contents are determined by adopting an external standard quantitative method. The external standard method comprises the steps of quantitatively injecting a certain amount of standard working solution into a gas chromatograph to obtain a DHA peak area; injecting the sample solution to be detected with the same volume into a chromatograph to obtain the peak area of DHA in the sample.
Surface oil detection
The detection method of the surface oil comprises the following steps: 5g of sample was accurately weighed and placed in a 50mL graduated centrifuge tube. Diluted to 40mL with cyclohexane. The sample was mixed with cyclohexane and shaken for 3 minutes. The mixture was filtered through a Whatman No. 40 filter paper to remove all solids. A50 mL round-bottom flask was dried in an oven at 105 ℃ for 1 hour, placed in a dry box to room temperature, and accurately weighed to three decimal places. 25mL of the filtrate was pipetted with a 25mL pipette and transferred to a 50mL clean tared round bottom flask. The round-bottomed flask with the sample was placed in a rotary evaporator and evaporated to dryness. After removal of the cyclohexylamine, the round bottom flask containing the remaining oil was placed in an oven at 105 ℃ for 1 hour to dry. The round bottom flask was taken out and placed in a desiccator to dry, and the round bottom flask was allowed to cool to room temperature before weighing. The round bottom flask was weighed and the content of extracted oil was determined.
Calculating the formula:
Figure BDA0003127082640000081
peroxide value detection
The detection method of the peroxide value of DHA or ARA comprises the following steps: a) a sample of 15g DHA and ARA was weighed into a 250mL ground flask, and 40mL hot water (60 ℃ C.) and 10mL 25% ammonia water were added, and the mixture was placed in a water bath at 65 ℃ for 15min while shaking several times, and then taken out and cooled. Adding 40mL of ethanol, shaking for 30s, adding 80mL of diethyl ether, shaking for 30s, performing ultrasonic treatment for 5min, transferring into a separating funnel, adding 80mL of petroleum ether, shaking for 2min, standing for 30min, discharging the water phase from the lower layer after the layering is clear, pouring the supernatant into a 250mL eggplant-shaped flask from the upper layer, and repeatedly extracting with 20mL of ethanol, 50mL of diethyl ether and 50mL of petroleum ether once. And finally, collecting the obtained ether solution, and evaporating the ether solution by using a rotary evaporator to obtain the grease. b) Weighing 2-5g of the uniformly mixed fat extracted in the step into a 250mL iodine measuring flask, adding 30mL of a chloroform-glacial acetic acid mixed solution, uniformly mixing to completely dissolve the sample, adding 1mL of saturated potassium iodide solution, plugging a bottle stopper, slightly shaking for half a minute, and then placing in the dark for 3 min. Taking out, adding 100mL of water and 1mL of starch indicator, and mixing uniformly. Titration with sodium thiosulfate standard titration solution was performed until the blue color disappeared as an end point and the volume consumed was recorded. Meanwhile, the same amount of chloroform-glacial acetic acid solution, potassium iodide solution and water are taken to carry out reagent blank experiments according to the same method.
The result is calculated according to the following formula:
X＝(V1-V2)×C×0.1269/M×100×78.8
x-peroxide value of the sample in milliequivalents per kilogram of fat (meq/kg);
v1 — sample consumption sodium thiosulfate standard titration solution volume in milliliters (mL);
v2 — reagent blank volume of sodium thiosulfate standard titration solution consumed in milliliters (mL);
c-concentration of sodium thiosulfate standard titration solution, in moles per liter (mol/L);
m-fat mass in grams (g);
0.1269-and 1.00mL sodium thiosulfate Standard titration solution [ C (Na)2S2O3)＝1.000mol/L]Equivalent mass of iodine in grams;
78.8-scaling factor;
the result is accurate to two decimal places.
Substituting into the above formula to obtain the peroxide content of the stored DHA and ARA.
The detection method of the milk powder taste and smell related to the embodiment of the invention is shown in the table 2:
TABLE 2
Figure BDA0003127082640000091
Examples
Example 1
The embodiment provides a method for verifying application of DHA in milk powder, which specifically comprises the following steps:
a new monomer DHA (fish oil type) sample of a certain manufacturer is packaged into 18 parts of 200 g small packages, the small packages are divided into two groups, 10 parts of 1 group are used for an accelerated experiment, 9 parts of the sample are placed in a constant temperature and humidity box at 42 ℃ for accelerated treatment of the shelf life 1/4, 1 part of the sample is used as an initial sample and is placed in a refrigerator at 18 ℃ below zero, and the shelf life of the DHA raw material is 24 months. Taking a bag of DHA sample from the incubator every 20 days, detecting DHA content, surface oil and peroxide value, and judging and analyzing the detection results of the initial sample and the sample subjected to accelerated treatment after 180 days, as shown in Table 3. And the other group of 8 samples is used for a normal-temperature experiment, the 8 samples are placed in a room at normal temperature and naturally stored for two years, one packet of DHA sample is taken every 4 months in the first year, one packet of DHA sample is taken every 3 months in the second year, in order to avoid detection errors, the samples are temporarily stored in a refrigerator at 18 ℃ below zero in the experiment period, and after the experiment is finished, the detection is uniformly carried out. The results are shown in Table 4.
TABLE 3
Figure BDA0003127082640000092
Figure BDA0003127082640000101
TABLE 4
Figure BDA0003127082640000102
Figure BDA0003127082640000111
As can be seen from the test results in Table 3, the DHA monomer samples stored at 42 ℃ were acceptable throughout the duration of the accelerated test.
As can be seen from the test results in Table 4, the DHA monomer sample is qualified within a storage period of two years under normal temperature conditions, and has no difference from the results in Table 3.
According to the formula, 9 kg of DHA is added to each ton of infant milk powder, and a new monomer DHA sample and a standard DHA sample are dry-mixed with the infant milk powder and then packaged into 400 g packages. After marking the samples, respectively putting 6 bags of the samples into a constant temperature and humidity box at 42 ℃ for storage, and putting one bag of the samples as an initial sample into a refrigerator at 18 ℃ below zero. Every other month, respectively taking one bag of new monomer DHA sample and one bag of standard DHA sample from the constant temperature box, putting the bags into a refrigerator at 18 ℃ below zero, and comparing the flavors and the odors of the new monomer DHA sample and the standard DHA sample by an organizer after 6 months, as shown in figure 1. As can be seen from the figure 1, the flavor of the new DHA and the flavor of the standard DHA infant milk powder sample are not different, the taste of the milk powder sample gradually deteriorates along with the time, the flavor is mainly represented as rancid flavor of oil, the sample has no obvious fishy smell in the whole shelf life, and the new 7% DHA sample has no obvious influence on the flavor of the product. The results of the above tests taken together indicate that DHA is less oxidized during shelf life.
Example 2
The embodiment provides a method for verifying application of DHA in milk powder, which specifically comprises the following steps:
a new monomer DHA (fish oil type) sample of a certain manufacturer is packaged into 18 parts of 200 g small packages, the small packages are divided into two groups, 8 parts of 1 group are used for an accelerated experiment, 7 parts of the sample are placed in a constant temperature and humidity box at 42 ℃ for accelerated treatment of the shelf life 1/5, 1 part of the sample is used as an initial sample and is placed in a refrigerator at 18 ℃ below zero, and the shelf life of the DHA raw material is 24 months. And taking a bag of DHA sample from the constant temperature box every 20 days, detecting the DHA content, the surface oil and the peroxide value, and judging and analyzing the detection results of the initial sample and the sample subjected to accelerated treatment after 144 days, as shown in Table 5. And the other group of 8 samples is used for a normal-temperature experiment, the 8 samples are placed in a room at normal temperature and naturally stored for two years, one packet of DHA sample is taken every 4 months in the first year, one packet of DHA sample is taken every 3 months in the second year, in order to avoid detection errors, the samples are temporarily stored in a refrigerator at 18 ℃ below zero in the experiment period, and after the experiment is finished, the detection is uniformly carried out. The results are shown in Table 6.
TABLE 5
Figure BDA0003127082640000121
TABLE 6
Figure BDA0003127082640000122
Figure BDA0003127082640000131
As can be seen from the results of the tests in Table 5, the DHA monomer samples stored at 42 ℃ were acceptable throughout the duration of the accelerated test.
As can be seen from the test results in Table 6, the DHA monomer samples are qualified within a storage period of two years under normal temperature conditions, and have no difference from the results in Table 5.
According to the formula, 9 kg of DHA is added to each ton of infant milk powder, and a new monomer DHA sample and a standard DHA sample are dry-mixed with the infant milk powder and then packaged into 400 g packages. After marking the samples, respectively putting 6 bags of the samples into a constant temperature and humidity box at 42 ℃ for storage, and putting one bag of the samples as an initial sample into a refrigerator at 18 ℃ below zero. Every other month, respectively taking one bag of new monomer DHA sample and one bag of standard DHA sample from the constant temperature box, putting the bags into a refrigerator at 18 ℃ below zero, and comparing the flavors and the odors of the new monomer DHA sample and the standard DHA sample by an organizer after 6 months, as shown in figure 2. As can be seen from the figure 2, the flavor of the new DHA and the flavor of the standard DHA infant milk powder sample are not different, the taste of the milk powder sample gradually deteriorates along with the time, the flavor is mainly represented as rancid flavor of oil, the sample has no obvious fishy smell in the whole shelf life, and the new 7% DHA sample has no obvious influence on the flavor of the product. The results of the above tests taken together indicate that DHA is less oxidized during shelf life.
Example 3
The embodiment provides a method for verifying the application of ARA in milk powder, which comprises the following specific steps:
packaging a new monomer ARA sample of a certain manufacturer into 10 portions of 200 g small packages, wherein 9 portions are placed in a constant temperature and humidity box at 42 ℃ for accelerated treatment of the shelf life 1/4, 1 portion is used as an initial sample and is placed in a refrigerator at 18 ℃ below zero, and the shelf life of the milk powder is 24 months. A pack of ARA samples was taken from the incubator every 20 days, the ARA content, the surface oil and the peroxide level were measured, and the results of the measurement of the initial sample and the accelerated sample were judged and analyzed 180 days later, as shown in Table 7.
TABLE 7
Figure BDA0003127082640000141
As can be seen from the results of the tests in Table 7, the ARA monomer samples were acceptable throughout the shelf life.
The new monomeric ARA sample and the standard ARA sample were dry blended with infant milk powder according to formula at 10 kg ARA per ton of infant milk powder and packaged as 400 g packages. After marking the samples, respectively putting 6 bags of the samples into a constant temperature and humidity box at 42 ℃ for storage, and putting one bag of the samples as an initial sample into a refrigerator at 18 ℃ below zero. Every month, a new monomer ARA sample and a standard ARA sample are respectively taken from the constant temperature box, and put into a refrigerator at 18 ℃ below zero, and after 6 months, the fresh monomer ARA sample and the standard ARA sample are compared by an organizer, as shown in figure 3.
From fig. 3, it can be seen that the flavor of the new ARA and standard ARA infant milk powder samples is not different, and the taste gradually deteriorates with time, mainly manifested as rancid flavor of oil, and the samples have no obvious fishy smell during the whole shelf life, which indicates that the new 10% ARA sample has no obvious influence on the flavor of the product. The results of the above tests in combination indicate that ARA is less oxidized during shelf life.
The foregoing is only a preferred embodiment of the present invention. It will be appreciated that various modifications, combinations, alterations, and substitutions of the details and features of the invention may be made by those skilled in the art without departing from the spirit and nature of the invention. Such modifications, combinations, alterations and substitutions are also to be understood as being included within the scope of the invention as claimed.

Claims (10)

1. A method for detecting DHA or ARA in milk powder is characterized by comprising an acceleration processing step and a detection step;
wherein the accelerating treatment step comprises the step of accelerating treatment of the milk powder at 37-45 ℃;
the time of the accelerated treatment is 1/n of the shelf life of the milk powder, and n is more than or equal to 3 and less than or equal to 5.
2. The detection method according to claim 1, wherein the detection method comprises a monomer experiment and a powder mixing experiment;
wherein the monomer experiment is carried out by accelerating the treatment of a monomer DHA or ARA sample to detect the DHA or ARA content, the surface oil and the peroxide value in the monomer DHA or ARA sample;
the powder mixing experiment is to detect the taste and smell in the mixed product by mixing the monomer DHA or ARA sample with the milk powder into the mixed product and then carrying out accelerated treatment.
3. The assay of claim 2, wherein the monomer assay comprises the steps of:
evenly subpackaging the monomer DHA or ARA samples into unit samples according to the mass, taking one unit sample as an initial unit sample, and storing the rest unit samples at the constant temperature of 37-45 ℃;
every 20 days, a unit sample preserved at constant temperature is taken, and the DHA or ARA content, the surface oil and the peroxide value are detected.
4. The detection method according to claim 2, wherein the powder mixing experiment comprises the following steps:
respectively dry-mixing a monomer DHA or ARA sample with milk powder according to a formula of the milk powder to obtain a mixed sample, and meanwhile, dry-mixing a corresponding standard DHA or standard ARA sample with the milk powder to obtain a standard mixed product;
respectively subpackaging the mixed sample and the standard mixed sample into a unit mixed sample and a unit standard mixed sample according to the average mass, taking one unit mixed sample and one unit standard mixed sample as an initial unit mixed sample and an initial unit standard mixed sample, and storing the rest unit mixed sample and the unit standard mixed sample in a 37-45 ℃ thermostat;
and respectively taking one pack of the unit mixed sample and one pack of the unit standard mixed sample from the constant temperature box every one month, storing at-18 ℃, and comparing the flavors of the mixed sample and the standard mixed sample after the accelerated treatment is finished.
5. The detection method according to claim 1 or 2, wherein the DHA or ARA are both in the form of a microcapsule powder.
6. The assay of claim 3 or 4, wherein the initial unit sample, the initial unit mixed sample and the initial unit standard mixed sample are samples stored at-18 ℃.
7. The method for detecting the content of DHA or ARA according to claim 3, wherein the method for detecting the content of DHA or ARA comprises the following steps:
(1) dissolving a monomer DHA or ARA sample by using an organic solvent, extracting and collecting the obtained extracting solution, continuously concentrating, and fixing the volume to obtain a pretreated sample;
(2) esterification: adding an alkali alcoholic solution into the pretreated sample for esterification treatment;
(3) DHA and ARA content was determined by external calibration.
8. The method for detecting the peroxidation value of DHA or ARA according to claim 3, wherein the method for detecting the peroxidation value of DHA or ARA comprises the following steps:
(1) dissolving a monomer DHA or ARA sample by using an organic solvent, extracting and collecting the obtained extracting solution, and continuously evaporating the extracting solution to dryness to obtain a pretreated sample;
(2) and (3) obtaining the DHA or ARA peroxidation value of the pretreatment sample through a titration method and a calculation formula.
9. The detection method according to claim 8, wherein the titration method comprises dissolving the pretreated sample, adding saturated potassium iodide solution, shaking, adding indicator, and titrating with a titration solution.
10. The detection method according to claim 8, wherein the DHA or ARA peroxidation value is calculated by the formula:
X＝(V1-V2)×C×0.1269/M×100×78.8
wherein, in the formula, the first and the second groups,
x: peroxide value of the sample in milliequivalents per kilogram of fat;
v1: the sample consumes the volume of the standard titration solution of sodium thiosulfate, and the unit is milliliter;
v2: reagent blank consumes the volume of sodium thiosulfate standard titration solution, in milliliters;
c: the concentration of the standard titration solution of sodium thiosulfate is expressed in mol per liter;
m: fat mass in grams.
CN202110691836.0A 2021-06-22 2021-06-22 Method for detecting DHA or ARA in milk powder Pending CN113848290A (en)

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