Methods of measuring pH in milk and dairy products

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Department of General Technical Disciplines and Technology

Ganja State University

Methods of measuring pH in milk and dairy products

Hajiyeva Bahar Sabir gizi Doctor of Philosophy on Technology

Abstract

In order to increase the safety and quality of food products, both raw materials and products are subjected to various analyzes. The amount of acid in the products is important in terms of their quality. One of the most common and practical methods used to measure acid levels is pH measurement.

The purpose of the study is to analyze the importance of protein-hydrogen (pH) value in dairy technology, to study the methods of measuring pH in milk and dairy products. Because the pH, known as the negative logarithm of the concentration of hydrogen ions, is important in dairy technology, as well as in a number of sciences. The main scientific novelty of the research is that it analyzes the new methods used to measure pH in dairy technology, the rules of using "pH-meter", how the measurement is performed and the importance of pH measurement in the production of dairy products.

Research methodology and methods. PH is very important in milk technology. Today, pH measurement is considered to be a more efficient method for determining the acidity of milk and dairy products. Measurement of pH in chemical and biological systems is carried out in two ways. The first is colorimetry and the second is potentiometry. The results of the study. PH is very important in milk technology. To determine the acidity of dairy products, pH measurement is now considered a more effective method than titration acidity. Because the concentration of pH or H ions accurately indicates the real level of acidity of milk. This is due to the fact that the pH is less variable.

Although there are different pH meters for various applications in the market today, in the food sector, which is developing with each passing day, it is necessary to develop new devices that are suitable for use in modern and complex food production techniques and have high measurement sensitivity.

Keywords: Milk, dairy technology, pH meter, food safety.

Анотація

Гаджієва Бахар Сабір гизи доктор філософії з техніки кафедри загальнотехнічних дисциплін та технології, Гянджинський Державний Університет

МЕТОДИ ВИМІРЮВАННЯ РН МОЛОКУ ТА МОЛОЧНИХ ПРОДУКТІВ

З метою підвищення безпеки та якості харчових продуктів як сировина, так і продукти піддаються різним аналізам. Кількість кислоти в продуктах важлива з погляду їхньої якості. Одним із найбільш поширених та практичних методів вимірювання рівня кислотності є вимірювання pH.

Мета дослідження вивчити значення білково-водневого (pH) показника у технології виробництва молока, вивчити методи вимірювання pH у молоці та молочних продуктах. Тому що значення рН, відоме як негативний логарифм концентрації іонів водню, має важливе значення у технології виробництва молочних продуктів, а також у ряді наук.

Основна наукова новизна дослідження полягає в тому, що в ньому аналізуються нові методи виміру рН у молочній технології, правила використання «рН-метра», спосіб проведення виміру та значення виміру рН у виробництві молочних продуктів.

Методологія та методи дослідження. PH дуже важливий у технології виробництва молока. На сьогоднішній день вимір рН вважається ефективнішим методом визначення кислотності молока та молочних продуктів. Вимірювання рН у хімічних та біологічних системах здійснюється двома способами. Перший - колориметричний, другий - потенціометричний.

Результати дослідження. PH дуже важливий у технології виробництва молока. Для визначення кислотності молочних продуктів вимір рН нині вважається ефективнішим методом, ніж титрування кислотності. Тому що концентрація pH або іонів H точно вказує на реальний рівень кислотності молока. Це з тим, що рН менш мінливий.

Хоча сьогодні на ринку існують різні рН-метри для різних застосувань, у харчовому секторі, який розвивається з кожним днем, необхідно розробити нові пристрої, що підходять для використання в сучасних та складних технологіях виробництва харчових продуктів та мають високі вимірювальні характеристики. чутливість.

Ключові слова: Молоко, молочна технологія, рН-метр, безпека харчових продуктів.

Problem statement. 83% of the total milk produced worldwide is obtained from cow's milk. 54% of the cow and buffalo milks are obtained from the Asian and European continents. Buffalo milk production is concentrated in certain countries. More than 90% of buffalo milk, which reaches 101 million tons, is produced in India and Pakistan. After India and Pakistan in production, Egypt, China, Iran and Italy come respectively. Approximately 2.4% of the world's total milk production is goat milk, 1.3% sheep milk and 0.4% camel milk. According to the 2012 data of the Food and Agriculture Organization, although goat milk is mainly produced in Asia (60%), Africa (22%) and Europe (15%); Sheep milk is produced in Asia (46%) and Europe (32%), while camel milk is mostly produced in Africa (91%) [12, p.7]. Various methods and means are used to protect the taste of the milk and milk products that are produced.

In milk technology, pH measurement should be determined in every situation where acidity may develop. Because the pH value gives very valuable clues about the quality and yield of the product. The pH value of newly milked healthy cow's milk is between 6.6- 6.8 [5, p.13].

As it is known, pH is the negative logarithm of the hydrogen ions (H+) concentration in a solution or substance. The "P" here is the first letter of the German word "protenz", which means base. "H" stands for hydrogen ions. Thus, pH means the negative exponent of the concentration of H+ ions [6, p.148].

In recent years, publications on the subject have conducted some research on the method of measuring the pH of milk and dairy products. Let's examine some of the research. Today, pH is used in many fields of knowledge as a criterion for different purposes. For example, in the medical field, the pH change in the blood is important in detecting some diseases or metabolic disorders. The value of blood with a normal pH of 7.4 in diabetes shifts towards the acid side and this is called "acidosis" in medical language. Likewise, a shift of blood pH to the alkaline side is called "alkalosis" [9, pp.29-30].

The equipment and methods to be used in measuring the pH of foods are very important for the accuracy, precision and precision of the result [17]. Traditionally, pH measurement is carried out with the help of pH meters, which include a glass electrode sensitive to the hydrogen ion (H+) in the environment, a reference electrode (hydrogen, kinhydron, antimony and bismuth) and a high impedance input. The reference electrode enables measurement by providing electric current according to the hydrogen ion concentration in the environment [8, p.78]. There are also various alternative methods and devices (such as color indicator pH sticks, photometers, etc.) for pH measurement. The pH values of raw milk are also determined by a digital pH-meter with glass electrodes [10, p.10]. However, the practical use of existing methods and devices is mostly limited to atmospheric pressure pH measurement. For example, the use of glass electrode assemblies for pH measurement in high pressure systems is not suitable due to the brittleness of the glass [4, p.24]. For such reasons, there are ISFET (ion sensitive fieldeffect transistor, "ion-sensitive field-effect transistor") pH sensors, which use semiconductor technology consisting of silicon microchip instead of fragile glass, according to the needs of the industry. However, the signals from these sensors cannot be analyzed with standard pH meters [11, pp. 404-405.]. Therefore, pH measurement should be performed based on the structure of the food and the measurement environment.

pH measurement in chemical and biological systems is done in two ways. These can be colorimetric or potentiometric. In colorimetric measurement, they make use of the change of indicator colors depending on the pH of the solution. While the sensitivity in colorimetric pH measurement is ± 1 pH, this sensitivity can be ± 0.001 pH in potentiometric measurement. Instruments that measure pH in a potentiometric way are called pH meters. Working principle of pH meter; They work according to the principle of measuring the potential difference between the solution whose pH value will be measured and the electrode. The measured electromotive force depends on the electrode potential of the electrode. The electrode potential of this electrode is only related to the concentration of H+ ions in the solution or the pH value. Accordingly, the pH value of the solution is calculated by measuring the electromotive force. This calculation is made automatically in pH meters and the pH value is given directly [6, pp.128-129].

Analysis of recent research and publication. According to the results of the researchers, although there are different pH-meters for various applications in the market today, it has been concluded that there is a need to develop practical new devices with high measurement precision, suitable for use in modern and complex food production techniques in the developing food sector. In addition, it is predicted that the increase in the number of studies on the relationship between pH value and the shelf life of foods and the development of modern pH sensors for many products will attract the attention of today's manufacturers and meet their expectations, and will be considered as a critical indicator in terms of food safety during storage and transportation stages [1, pp.210-211].

The purpose of the study is to analyze the importance of protein-hydrogen (pH) value in dairy technology, to study the methods of measuring pH in milk and dairy products. Because the pH, known as the negative logarithm of the concentration of hydrogen ions, is important in dairy technology, as well as in a number of sciences.

Main of the work. The importance of pH in milk and dairy products technology; pH is of great importance in milk technology. Today, pH measurement is seen as a better way to determine the acidity of milk and its products, compared to titration acidity. Because the pH or the concentration of H ions shows the true acidity of the milk. This is because the pH is less variable.

The pH of raw milk varies between 6.4-6.8 [14, p.198]. The newly milked milk shows an acidic reaction (initial acidity). However, this feature decreases over time. Depending on the waiting period and milking conditions, it can be contaminated with microorganisms and can increase the acidity (developing acidity) by breaking down lactose into lactic acid as a result of the activity of microorganisms (such as lactic acid bacteria). When the pH of raw milk is measured higher than 6.8, it can be thought that the animal has mastitis disease or adulteration is done by adding sodium hydroxide, known as caustic, in order to mask the acidity of the milk. It is predicted that milk with a pH of less than 6.5 is colostrums or may be curdled due to increased acidity in the milk. Therefore, milk with pH problems should not be accepted into the enterprise [7, p.259]. Electronic language (e-language) has been developed as a modern analytical tool in a study on the use of pH as an indicator of milk freshness. E-dil is a sensor system that measures and compares the taste of liquid or solid samples. The human taste system is mimicked by chemical sensors that act as taste receptors and generate electrical signals as a function of the potentiometric response [15, pp.168-169].

Measurement of pH in milk and dairy products; In terms of measurement, it is important to pay attention to the maintenance and use of electrodes. These are [2, p.8]: protein hydrogen acidity dairy

Electrodes should be handled with care. Because the electrode is the most important and sensitive part in pH measurement and it directly affects the correct measurement.

Wear and scratches on the electrode change the sensitivity. Before using a new glass electrode, it should be soaked for at least 2 hours in a “potassium chloride” solution (35 g in 100 ml of distilled water) to ensure accurate measurement.

The electrode must be kept clean.

Between samples and buffer solutions, the electrode should be rinsed with distilled water, and then the remaining water should be absorbed onto the blotter paper, never wiped.

When working with oily samples that reduce the sensitivity of the electrodes, the layer on the electrode should be removed using either hexane (ACS Grade) or a sponge with a mild soap solution. Then it should be rinsed with distilled water and dried with blotting paper.

When the electrode is to be used for measurement or standardization, it should be immersed in the sample to cover the pH-sensitive bulb of the electrode and the reference electrode wick.

The protective cover in the filling part of the glass electrodes should be removed.

Before the electrodes are used, the reference side rubber cap is opened to allow a slow flow of solution through the electrode bridge. This process prevents contamination of the reference electrode and a good electrical contact is ensured from the liquid junction. Since the potassium chloride solution will diffuse outward at this time, it is necessary to periodically replace the potassium chloride solution with saturated potassium chloride (50 g of KCL is placed in a container containing 100 ml of water and heated to dissolve the crystals, then transferred to a stock bottle and used after cooling) from the filling point.

When storing the electrodes, it is necessary to put the pH sensitive end in potassium chloride solution. This provides a moist environment for the glass electrode, preventing leaks.

Storing the electrode in pure water is inconvenient as it will cause errors in the measurements. If the electrodes will not be used for a few months, they should be stored dry. In this case, it should be soaked in water for a few days before use [3, p.190].

Before use, the pH-meter is stabilized by running it at least half an hour before. It is best to leave the pH meter on at all times. Before measuring on samples, the pH meter should be standardized with fresh and uncontaminated buffer solutions. Buffer solutions should be kept closed when not in use to protect them from water loss and contamination. Used buffer solutions should never be poured onto the stock solution. At the end of the same day, used solutions should be discarded. After pouring approximately 25 ml of buffer solution into a 50 ml beaker, standardize the pH meter with a buffer solution of pH 7.0 and close to the pH of the sample to be analyzed. Then, for adjustment, act as in the user's manual of the pH meter device. If there is no contrary statement in the user manual, the pH meter should be re-standardized every day. When the sample type is changed or at least if the pH meter has not been used for half an hour the standardization process should be repeated [16, p.244].

The electrode is immersed in the sample so that the pH sensitive part of the electrode (the bulb-like part) and the reference junction are in good contact with the sample. If cheese is measured, as mentioned before, the cheese must be well crushed or ground in a small bowl. This is essential for the electrode to come into good contact with the solid part. The temperature of the sample is then measured and the temperature balance is adjusted so that the temperature of the pH meter corresponds to the temperature of the sample. For best results, the temperature of the sample should be 25 ± 3 °C. Then the device is brought to the pH measurement and the reading is taken in at least 45 seconds when the electrodes are in good contact with the sample. Of course, the reading on the pH meter indicator should be stable during this time. The fixed value is recorded as pH [2, p. 9].

Preparation of samples for measurement. Let's take a closer look at the preparation of such samples in milk and dairy products.

Liquid Samples - Liquid samples such as milk, cream, buttermilk, and yoghurt can be tested after standardization by simply immersing the electrode in the sample without further processing [3, p.192].

Reduced water samples - Reduced water samples - This type of sample is diluted as follows. For example, 7.5 g of buttermilk solids, 6.5 g of whey solids and 12 g of whey concentrate are put into a 100 ml beaker. Add 25 ml of distilled water and mix slowly until the mixture dissolves. The volume is then made up to 100 ml and mixed well again. A sufficient amount is taken from here and its pH is measured.

Cheese samples - Since the pH of cheese samples will vary from piece to piece, these samples are made homogeneous by grinding or breaking them. A small amount of this homogenized sample is taken and placed in a small container that the electrode can easily contact. Electrodes are spaced in the cheese sample with a thermometer so that the electrodes can be placed gently. Cheese should not be diluted with water. Since this process will upset the salt balance, it raises the pH by 0.3 units. Before testing the cheese, the pH meter is turned on and left in operation for 5 minutes. It is then checked for accuracy against standard buffer solutions. The pH range of standard buffer solutions for fermented dairy products and cheese should be `between' 4-6. The electrode is then placed on the cheese sample. The visible pH value is read from the pH meter. The electrode is then placed on the cheese sample. The visible pH value is read from the pH meter. After each determination, the sample cup is moved and measurements are made in three different places for the same cheese sample. Thus, it is understood whether the correct measurement is made or not. Then, after the electrodes are thoroughly washed and dried with blotting paper, another measurement can be started. If not, the electrodes are placed in place [13, p.559].

- Butter and margarine samples - in these samples the pH measurement is done in the serum phase. For this, the serum phase must be separated from the oil phase. To prepare the serum, 114 g of margarine or butter is weighed and put into a 400 ml beaker. Then the beaker is placed in a water bath at 46-52 °C. Thus, the fat melts and collects in the upper part, while the serum is collected in the lower part. This process takes about 45 minutes. The sample should not be shaken during heating. When the separation is completed, the serum portion under the fat layer is taken with the help of a pipette and placed in a 30 ml beaker or centrifuge tube and centrifuged for 3 minutes in a balanced centrifuge. The beaker is then placed in the refrigerator or ice bath for 2 hours to freeze or separate any possible oil particles. After the oil layer is formed, the serum under the oil layer is drawn with the help of a pipette. The serum is then transferred to a clean 25 ml beaker. The pH of the serum is measured by heating the temperature up to 25 °C. As an alternative to the above process; After the butter or margarine melts, the serum under the fat layer is taken with the help of a pipette and placed in a separating funnel. In this way, it is kept for the oil to rise. Centrifuging the separator funnel can speed up the separation process if a suitable centrifuge is available. Then the portion of serum under the fat layer is removed, heated at 25 °C and the pH of the pack is measured [3, p.216].

Conclusions

PH is very important in milk technology. To determine the acidity of dairy products, pH measurement is now considered a more effective method than titration acidity. Because the concentration of pH or H ions accurately indicates the real level of acidity of milk. This is due to the fact that the pH is less variable.

The pH is also important in yogurt production technology, especially at the end of the incubation period.

Measuring pH is more important in cheese production technology than titration acidity. This is because measuring pH is a more efficient way to determine the titration acidity of cheese.

Although there are different pH meters for various applications in the market today, in the food sector, which is developing with each passing day, it is necessary to develop new devices that are suitable for use in modern and complex food production techniques and have high measurement sensitivity.

References

1. Aksoy, A. (2021), Aksoy, A. [The importance of pH measurement in foods. Halich University Science Journal, № 4/2], Gidalarda pH olgumunun onemi. Halic Universiteti Deqiq Elmler Jurnali, № 4/2, ss.193-216.

2. Anonymous, (1994). Instruction manual for laboratory micro-processor pH mater. Hanna instruments Inc. Woosocket RI, FSA, 11 p.

3. Case, R.A., Bradley, R.L. and Williams, R.R., 1985. Chemical and physical methods. “In Standart methods for the examinations of dairy products, G.H.Richardson”. APHA. Washington DC, 412 p.

4. Chaminda, P., Samaranayake, C.P., Sastry, S.K., In-situ pH measurement of selected liquid foods under high pressure. Innovative Food Science and Emerging Technologies, 17, (2012), pp.22-26.

5. Qetiner, §. (2018), Chetiner, S. [Analysis of milk and its products], Sut ve urunleri analizleri.

6. Erdik, E.V., Sarikaya, Y., (1993), Erdik, E.V., Sarikaya, Y. [Basic University Chemistry. Ankara: Ozkan Mat. Ltd. Sti.], Temel Universite Kimyasi. Ankara: Ozkan Matbaasi, 545s.

7. Ertem, H.veQakmak(0,9., (2019), Ertem, H. and Chakmakchi, S., [Investigation of raw milk sold openly in Erzurum in terms of some tricks and quality characteristics - comparison with the relevant paper. Journal of Ataturk University Faculty of Agriculture, № 50/3], Erzurum'da acik olarak sati§a sunulan gig sutlerin bazi hileler ve kalite ozellikleri yonunden ara§tirilmasi - ilgili teblig ile kar§ila§tirilmasi. Ataturk Universitesi Ziraat Fakultesi Dergisi, 50(3), ss.255-262.

8. G^ili, O.G. (2015), Gamli, O.G., [Laboratory Techniques and Basic Food Analysis. Bursa: Dora Publishing], Laboratuar Teknikleri ve Temel Gida Analizleri. Bursa: Dora Yayincilik.

9. Horton, H.R., Moran, L.A., Ochs, B.S., Rawn, D.J., and Scrimegeour, K.G. (1993), Principles of biochemistry. Neil Patterson Pub. Prentice Hall, Englewood Cliffs, New Jersey, pp.25-35.

10. ipin,G.F. (2011), Ipin, G.F. [The effects of milk powder addition and storage time on the properties of cream yoghurt. Chukurova University Social Sciences Institute, Adana/Turkey], Krema yogurdunun ozellikleri uzerine sut tozu ilavesi ve depolama suresinin etkileri. Qukurova Universiteti Sosial Elmlar institutu, Adana/Turkiye.

11. Jiang, Y., Liu, X., Huang, X., Feng, H., Zhang, Q., Yu, H. (2018), High-sensitivity potentiometric 65-nm cmos ISFET sensor for rapid E. coli screening. IEEE Transactions On Biomedical Circuits And Systems, №12/2, pp.402-415.

12. Karabulut, U., Yazici M.E. (2018), Karabulut, U. and Yazici M.E. [Perception of milk and dairy products. Ankara: iksad Publications], Sut ve sut urunleri algisi. Ankara: iksad Publications.

13. Kosikowski, F. 1982. Cheese and fermented milk foods. Second Edition. By F.V. Kosikowski and Ass. P.O. Box, New York: Brooktondale, 711 p.

14. Kuguk, SiC. veYibar,A., (2019), KuchaF, S.C.andYibar, A..|T1ic fl^ect,s of raw milk and pasteurized milk consumption on public health. Food and Health, № 5/3], Cig sut ve pastorize sut tuketiminin halk sagligi uzerine etkileri. Food and Health, № 5/3, ss.197-204.

15. Tanz.T.B.. Zulkafli,M.S.(2013),El ectronictongueforfreshmilkass essment a revisit of using ph as indicator. IEEE International Conference on Circuits and Systems (ICCAS), Book of Proceedings, pp.167-171.

16. Tuzine0,A.(199O) . Tuzmee, A. [Soii and waie rancSys)s iabosstories hangUoog. Director of Rural Services. Ankara], Toprak ve su analiz laboratuvarlari el kitabi. Koy Hizmetleri Genel Mudurlugu, Ankara, 373s.

17. Ssvakumar, P. and Adedeji, A., Measuring the pH of food products. (2017).

Література

1. Aksoy, A. (2021), Aksoy, A. [The importance of pH measurement in foods. Halich University Science Journal, № 4/2], Gidalarda pH olciiiiiiiniin onemi. Halig Universiteti Deqiq Elmler Jurnali, № 4/2, ss.193-216.

2. Anonymous, (1994). Instruction manual for laboratory micro-processor pH mater. Hanna instruments Inc. Woosocket RI, FSA, 11 p.

3. Case, R.A., Bradley, R.L. and Williams, R.R., 1985. Chemical and physical methods. “In Standart methods for the examinations of dairy products, G.H.Richardson”. APHA. Washington DC, 412 p.

4. Chaminda, P., Samaranayake, C.P., Sastry, S.K., In-situ pH measurement of selected liquid foods under high pressure. Innovative Food Science and Emerging Technologies, 17, (2012), pp.22-26.

5. Qetiner, §. (2018), Chetiner, S. [Analysis of milk and its products], Sut ve urunleri analizleri.

6. Erdik, E.V., Sarikaya, Y., (1993), Erdik, E.V., Sarikaya, Y. [Basic University Chemistry. Ankara: Ozkan Mat. Ltd. Sti.], Temel Universite Kimyasi. Ankara: Ozkan Matbaasi, 545s.

7. Ertem, H. ve Qakmakgi, S., (2019), Ertem, H. and Chakmakchi, S., [Investigation of raw milk sold openly in Erzurum in terms of some tricks and quality characteristics - comparison with the relevant paper. Journal of Ataturk University Faculty of Agriculture, № 50/3], Erzurum'da acik olarak sati§a sunulan gig sutlerin bazi hileler ve kalite ozellikleri yonunden ara§tirilmasi - ilgili teblig ile kar§ila§tirilmasi. Ataturk Universitesi Ziraat Fakultesi Dergisi, 50(3), ss.255-262.

8. Gamli, O.G. (2015), Gamli, O.G., [Laboratory Techniques and Basic Food Analysis. Bursa: Dora Publishing], Laboratuar Teknikleri ve Temel Gida Analizleri. Bursa: Dora Yayincilik.

9. Horton, H.R., Moran, L.A., Ochs, B.S., Rawn, D.J., and Scrimegeour, K.G. (1993), Principles of biochemistry. Neil Patterson Pub. Prentice Hall, Englewood Cliffs, New Jersey, pp.25-35.

10. ipin, G.F. (2011), Ipin, G.F. [The effects of milk powder addition and storage time on the properties of cream yoghurt. Chukurova University Social Sciences Institute, Adana/Turkey], Krema yogurdunun ozellikleri uzerine sut tozu ilavesi ve depolama suresinin etkileri. Qukurova Universiteti Sosial Elmlar institutu, Adana/Turkiye.

11. Jiang, Y., Liu, X., Huang, X., Feng, H., Zhang, Q., Yu, H. (2018), High-sensitivity potentiometric 65-nm cmos ISFET sensor for rapid E. coli screening. IEEE Transactions On Biomedical Circuits And Systems, №12/2, pp.402-415.

12. Karabulut, U., Yazici M.E. (2018), Karabulut, U. and Yazici M.E. [Perception of milk and dairy products. Ankara: iksad Publications], Sut ve sut urunleri algisi. Ankara: iksad Publications.

13. Kosikowski, F. 1982. Cheese and fermented milk foods. Second Edition. By F.V. Kosikowski and Ass. P.O. Box, New York: Brooktondale, 711 p.

14. Kucuk, S.C. ve Yibar, A., (2019), Kuchuk, S.C. and Yibar, A., [The effects of raw milk and pasteurized milk consumption on public health. Food and Health, № 5/3], Cig sut ve pastorize sut tuketiminin halk sagligi uzerine etkileri. Food and Health, № 5/3, ss.197-204.

15. Tang, T.B., Zulkafli, M.S. (2013), Electronic tongue for fresh milk assessment a revisit of using ph as indicator. IEEE International Conference on Circuits and Systems (ICCAS), Book of Proceedings, pp.167-171.

16. Tuziner, A. (1990), Tuziner, A. [Soil and water analysis laboratories handbook. Director of Rural Services. Ankara], Toprak ve su analiz laboratuvarlari el kitabi. Koy Hizmetleri Genel Mudurlugu, Ankara, 373s.

17. Vijayakumar, P. and Adedeji, A., Measuring the pH of food products. (2017).

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