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MINISTRY OF EDUCATION AND SCIENCE OF THE REPUBLIC OFСтр 1 из 15Следующая ⇒
Ф.7.03-03 MINISTRY OF EDUCATION AND SCIENCE OF THE REPUBLIC OF KAZAKHSTAN
M. AUEZOV SOUTH KAZAKHSTAN STATE UNIVERSITY
Kanseitova E.T, Berdembetova A. T., Kobeyeva Zh.K., Balabekova A.S
METHODICAL INSTRUCTIONS on performance of laboratory works on discipline " Technology of milk and dairy products"
Shymkent- 2016
MINISTRY OF EDUCATION AND SCIENCE OF THE REPUBLIC OF KAZAKHSTAN M. AUEZOV SOUTH KAZAKHSTAN STATE UNIVERSITY Department «Technology and food safety» Kanseitova E.T., Berdembetova A. T., Kobeyeva Zh.K., Balabekova A.S. METHODICAL INSTRUCTIONS Laboratory works On discipline " Technology of milk and dairy products" For students in the specialty 5B072700 - " Technology of food products"
Shymkent- 2016
UDK 355.65 BBK 36
Originators: Kanseitova E., Berdimbetova A. T., Kobeyeva Zh.K., Balabekova A.S. Methodical instructions to laboratory works on discipline " Technology of milk and dairy products" - Shymkent: SKSU after M. Auezov, 2016. - 66 pages. Methodical instructions are made according to requirements of the curriculum and the program of discipline " Technology of milk and dairy products" and include all necessary data on performance of laboratory works of a course.
Laboratory works contain theoretical bases of standard technological processes, work performance techniques, safety measures of performance of work and control questions for each work. Methodical instructions are intended for students of the specialty 5V072700 Technology of Food Products Reviewer: Shambulova G.D. - Cand.Sci.Tech., docent
It is considered and is recommended for printing a faculty meeting of PI and PPB (the protocol No. ___ from " ___" _________ 20 ____ and the methodical commission of faculty the Higher school " Textiles and food engineering" (the protocol No. ___ from " __" _____ 20 ___)
It is recommended to the edition Educational and methodical council of SKSU after M. Auezov, the protocol No. ___ " ___" _________ 2016 y.
© M. Auezov South Kazakhstan state university, 2016
Responsible for Berdimbetova A. T release.
CONTENTS
Introduction In training of bachelors of specialty 5B072700 – " Technology of food products" of one of basic disciplines of the curriculum " The technology of milk and dairy products" are. This discipline consists of a lecture rate, a laboratory practical work and practical works. The laboratory practical work is an important, integral part of studying of this discipline. On laboratory researches skills of the practical experimental and settlement analysis of engineering procedures take root, the main regularities of their course, influence of process parameters on the main indicators – extent of transformation, speed of process and a product yield are studied and acquired. Based on it optimum conditions of conducting process are chosen, the major factors characterizing cost, technological and ecological efficiency of the studied technology are calculated. The educational and methodical benefit covers content of all rate and contains 15 laboratory works, each of which includes: work purpose; the theoretical data explaining essence of the studied process; description of installation; the used equipment, technical and tools; technique of performance of work and analyses; procedure of payments of technological indicators of process; control questions for self-checking of knowledge and abilities; safe engineering in case of performance of work. During a semester students perform works according to the scope of laboratory works on modules given in a syllabus. On the first occupation students get acquainted with safe engineering during the work in laboratories which shall be observed strictly in case of accomplishment of each work. Laboratory works are performed by crews on 3-4 persons after receipt of the admission of the teacher which provides knowledge of a technique of carrying out work and the scheme of installation. After performance of work each student carries out calculations according to a task, draws conclusions about efficiency of process and arranges the report. The report constitute according to requirements of the SMQ SKSU named by M. Auezov 7.04.2012 – " Studies. General requirements to the organization, content and training" also arrange in a hand-written or printing type. Protection of the report consists in the answer to control questions on theoretical bases of processes. Laboratory works are constituted according to contents of programs of discipline " Technology of milk and dairy products" for students of specialty 5V072700 – Technology of food products and according to requirements of the SMQ SKSU named by M. Auezov F.7-03-2012 – " Management of educational and methodical processes". Laboratory work №1 Short theoretical data The main indicator of freshness of milk is titrable acidity. In fermentable milk it constitutes 16-18 0T. After a while after milking acidity of milk increases as in it the microorganisms fermenting lactose to lactic acid begin to develop. Acidity of milk is expressed in 0T degrees. Tipsy 0T the quantity of milliliters of 0, 1 N of solution of alkali (a caustic natr or caustic potassium) which went for neutralization of 100 ml of milk in case of the indicator of a fenolftalein is understood. Determination of freshness of milk on titrable and extreme acidity gives the chance to judge milk reaction change, but doesn't allow to catch changes of the major components of milk, in particular proteins. So, if to fresh milk to add milk with the increased acidity (27-300T) and it is good to mix, then titrable acidity of mix can not exceed 200T. However such milk doesn't maintain heat treatment, proteins of milk coagulate and can spoil all lot of products. For the purpose of milk impurity identification with the increased acidity the heating and spirit tests characterizing stability of a proteinaceous phase are carried out. Action of these tests is based on equal sensitivity of proteins of milk to action of high temperatures and alcohols depending on рН. Knowing titrable acidity and having result of heating and spirit tests, it is possible to establish general freshness of milk (tab. 1)
Work performance order In a conic flask with a capacity of 150-200 ml measure 10 ml of milk by means of a pipette, add 20 ml distilled water and three drops of 1% - го spirit solution of a fenolftalein. Mix is carefully mixed and titrut 0, 1 N solution of a caustic natr before emergence of the weak-pink coloring which isn't disappearing within one minute. Acidity of milk is equal in Turner's degrees to the quantity of milliliters of 0, 1 N of solution of the caustic natr (heat) spent for neutralization of 10 ml of milk, increased on 10. Divergences between parallel definitions there have to be no more than 1 °Т. In mass analyses when a large amount of milk is subject to acceptance, define extreme acidity, i.e. acidity, is higher than which milk is considered sub-standard. In this case in a row the test tubes placed in a support are poured on 10 ml 0, 1 N of the solution of alkali containing phenolphthalein and add 5 ml of the studied milk. Contents are mixed and watched coloring change. If solution has become colourless, so acidity of milk above norm. When conducting heat test in a test tube pour 5 ml of milk and heat to boiling. Milk which titrable acidity higher than 24°T, at boiling is curtailed. Heating test allows to find also in fresh milk milk impurity with the increased acidity as the mixed milk at boiling also turns. During spirit test in a test tube or Petri's cup pour 1 ml of the studied milk, add 1 ml of 68% ethyl alcohol, mix and monitor emergence of flakes of protein. As alcohol with a strength of 68% causes casein coagulation only at the acidity of milk exceeding 20°T spirit test gives the chance to reveal the extreme acidity of milk allowed by the standard and also to find sour milk in fresh. If acidity of milk is lower 20°T, then protein keeps the colloidal properties and milk doesn't turn. Lack of flakes curled up a squirrel testifies to freshness of milk. Formation of flakes, even hardly noticeable, indicates the lowered stability of proteins of milk. Laboratory work №2 Short theoretical data Analyzer " laktan 1-4" provide measurement in milk and cream mass fraction of fat, SNF and density. The principle of operation of devices based on the dependence of the propagation velocity of ultrasonic vibrations in milk, from its composition. Vosstaknovlenny milk, tinned test of milk, low fat milk and cream of different fat content can be an object of a research besides integral. Range of measurements of a massokvy share of fat makes from 0 to 20% (for cream fat content higher than 15% before the analysis prepare cultivation), SOMO — from 6 to 12%, density — from 1000 to 1040 kg/m3. As preservative for tests of milk it is possible to use a potassium bichromate. The Laktan 1-4 analyzer which appearance is shown in fig. 2 is placed in the plastic case consisting of two demountable parts: top and lower.
Fig. 2 Ultrasonic analyzer of Laktan 1-4 milk In the top part of a raspolokzhena all main details of the analyzer, in the lower part there is a power supply. The lower part also serves as a support, obeskpechivayushchy stability of the analyzer in working situation. The upper and lower parts are connected in this position the guides, which also serve as contacts for electrical connection of the analyzer with the power supply. On the forward panel are located: the digital indicator, a holder for fixing of a the sample taker, the button for the choice of an operating mode of the analyzer, I will corrode for connection of the accumulator. 4 models of the Laktan-Super analyzer are created. Analyzers of models 150 and 200 with a productivity up to 30 tests in an hour of a calculated for application at the dairy plants of a small and average power, in farms. Devices of models 500 and 550 a performance to 200 tests an hour can be used at the large dairy enterprises, in the selection centers, regional laboratories Equipment, devices and technical means: drinking milk, flask, thermometer, water bath, OUSE device " Laktan 1-4". Work performance order The principle of measurement of a speed of distribution of ultrasound which is function of a mass fraction of fat, SOMO, density and temperature of milk (cream) is the basis for operation of the analyzer. The analyzer consists of system of reception of milk (cream), the block of heating and a termostatirovaniye, the device of measurement and calculation on the basis of the microcomputer. In the measurement mode test is consistently warmed up to two set temperatures. Before work the device is given into position. In the Laktan 1-4 analyzer after installation of a glass about breakdown of milk turn on the Start-up button in situation " Measurement", and on knot of control of the piston micropump the signal arrives. There is a fence of test of milk in a measuring cell in which within 1, 5 min. she heats up and termostatirutsya at a temperature of 41 ° C. Then during 5 with at this temperature measure the geknerator frequency which is proportional to the speed of distribution of an ultrasound. After that test heats up to temperature of 65 °C, generator frequency is measured again. On values of the found frequencies of the microcomputer calculates mass fractions of fat and SOMO, values, which are displayed on indicators (everyone 5 c). After define of mass fractions milk merges in a glass about breakdown. Preparation of the analyzer for use 1.1 Requirements to the measured samples: 1) The fresh, tinned, pasteurized, normalized, restored, skim milk and milk of long storage is allowed to the analysis. 2) Sampling is made in accordance with GOST 13928 and GOST 26809 (for milk and cream), in accordance with GOST 3622 (for powdered milk, the concentrated milk and ice cream) and according to indications of a technique of performance of measurements (further MVI). 3) Preparation of tests to be made according to requirements of MVI. 4) The working volume of the analyzed milk test – 25 mm3. 5) Acidity of the analyzed milk no more than 20 T °. 6) Temperature of the analyzed milk from 15 °C to 35 °C.
Laboratory work № 3 Short theoretical data Definition of albumens in milk by method of formal titration. The method is based on binding of free amino groups of proteins by aldegidny groups of formalin therefore acidity of milk changes. The shift (on a titration curve) to the area of lower values рН is observed. The method is applicable for determination of the sum of albumens in milk (acidity not higher than 220 0T). Definition of percentage of protein in milk by a refraktometrical method. The index of refraction of Pd of milk consists of the sum of Pd of water and Pd of the proteins dissolved in her, dairy sugar, nonprotein nitrogenous substances and salts. Nonprotein nitrogenous substances, dairy sugar and salts are in milk in the form of true solution, a squirrel - in the form of colloidal. Fat in milk is in a type of an emulsion and doesn't influence total index of refraction of milk. Content of proteins (the sum of casein, albumine, globulin) in milk is determined by a difference of indications on a scale of " Squirrels" of milk and bezbelkovy serum under identical conditions of the performed measurements. Colorimetric method of definition of protein in milk. The method is intended for the research purposes. Ability of proteins to connect sour dyes is the basis him. By a colorimetric method, as well as by a standard method of Kjeldal, define a mass fraction of the general protein, including fraction of nonprotein nitrogen. Express measurement of protein content in milk on devices a belkomer of BMTs-1 or BM-003. The principle of operation of the device is based on a photocolorimetric method of measurement of optical density of the filtered mix of a dose of milk and a dose of solution of dye of organic acid blue-black. The method is based on ability of proteins of milk at рН below an isoelectric point to connect sour dyes, forming with them an insoluble complex, at the same time the optical density of solution of dye decreases in proportion to amount of protein. After removal of an insoluble complex measure again the optical density of the solution containing ostatochno untied dye which is proportional to a mass fraction of protein in milk. Structurally the device consists of two blocks: measuring and block of preparation of test. Definition of the general protein in milk by Kjeldal's method. The method of definition of nitrogenous substances in foodstuff has been offered by Kjeldal in 1883 and still, with little changes, is the main method of definition of albumens in milk and dairy products. Kjeldal has developed a method of determination of amount of proteins on nitrogen, bases in milk and dairy products. Kjeldal has developed a method of determination of amount of proteins on nitrogen, that organic substances when heating with the concentrated sulfuric acid are oxidized to H2O and CO2, and nitrogen of amino groups – NH2 passes into sulfate ammonium. Sulfuric acid when heating decays on sulphurous anhydride, atomic oxygen and water: H2SO4 The emitted atomic oxygen oxidizes amino acids. After the end of oxidation aminny nitrogen of albumens will be in a form of ammoniyny salt. Transferring nitrogen of proteinaceous connections to a form of sulfate ammonium, define amount of nitrogen in the form of ammonia, for this purpose dilute solution with water, neutralize sulfuric acid solution of a caustic natr and surplus create him alkaline reaction thanks to what ammoniyny salts emit ammonia: (NH)2SO4 + 2NaOH = Na2SO4 + 2NH3 + H2O The formed ammonia is overtaken in a reception flask with boric acid, Borat of ammonium which in the water environment is strongly hydrolyzed as a result turns out and has the alkaline environment, For neutralization he is used hydrochloric acid. By the number of ml of 0, 1 N of HCl solution who have gone for titration borathat find amount of nitrogen. For determination of amount of proteins the amount of nitrogen is multiplied by coefficient 6, 38. The coefficient is established from calculation that the amount of nitrogen is equal in milk proteins to 15, 65%. Equipment, devices and technical means: The refractometer, bath water, scales, pipettes on 1 ml, 5 ml, 10 ml, 20 ml, the device for measuring off of formaldehyde with a capacity of 1 ml, a test tube with a capacity of 10 ml, a flask measured on 100 ml, filter paper, Kjeldal's flask, a byuksa with a cover, acetic acid 10% solution, calcium chloride 4% solution, фенолфталеин 2% solution, a hydroxide of sodium of 0, 1 N solution, formalin 36-40% solution, cobalt sulfate 25% solution, milk of different structure; sulfate potassium, mercury oxide, sulfate copper, sulfuric acid, Tashiro's indicator, boric acid. Work performance order Definition of albumens in milk by method of formal titration. Bring in a glass with a capacity of 150-200 ml a pipette 20 ml of milk, 0, 25 ml of 2% solution of a fenolftalein and titrut 0, 1 N sodium hydroxide solution before emergence of the weak-pink coloring corresponding to a control standard. Then bring 4 ml of the neutralized 36-40% formaldehyde and again titrut before such coloring, as well as at the first titration. For preparation of a control standard of coloring in the same glass measure 30 ml of milk and 1 ml of 0, 25% - го cobalt sulfate solution. The standard is suitable for work during one change. In order to avoid a sediment of cream the standard is recommended to be poured periodically. The share of the general protein in milk can be determined also by table 3.1 Table 3.1
In parallel make check experiment on neutralization of mix of 20 ml of water and 5 ml of solution of formaldehyde. Processing of results. The mass fraction of protein (X2) is calculated as a percentage on a formula:
X2 = (V2 - V1 - V0) * 0, 96 + X1, (1) where: V2 - the total of solution spent for neutralization, ml; V1 - the amount of solution spent for neutralization before introduction of formaldehyde, ml; V0 - the amount of solution spent for check experiment, ml; 0, 96 - empirical coefficient, %/ml; X1 - the amendment to result of measurement of a mass fraction of protein, %. Determine the percentage of protein in milk by the refractometric method. For receiving protein-free serum measure 5 ml of the studied milk in a bottle and add to him 5-6 drops of 4% solution of chloride calcium (40 g of CaCI2 in one liter of the distilled water). The bottle is closed a stopper and slightly shake up contents. At the same time prepare 2-3 parallel tests (bottles have to be numbered). Bottles place in a tank, pour in it water to a half of height of bottles, close a cover. Water in a tank is boiled within ten minutes. Then hot water is replaced cold. Bottles cool within two minutes. Bottles take out from a tank, stir up so that the clot has collapsed and the emitted serum has mixed up with condensate. The filtered serum is applied on a measuring prism of the refractometer and smoothly close it a lighting prism. Observing in an eyepiece, clean an color of border of a treatment of light and shade. For improvement of sharpness of border measurement needs to be taken in 0, 5 - 1 min. since during this time from test air is removed and the surface of a lighting prism is better moistened. On a scale of " Squirrels" read the instrument for serum. Measurements repeat 3-4 times and count arithmetic-mean value of Bs. Having removed serum from both prisms, they are carefully washed out water and wiped a pure soft napkin or cotton wool. Then 1-2 drops of the studied milk place on a measuring prism. Take measurements on a scale of " Squirrels" in the same order, as on serum. As sharpness of border at milk is slightly worse, than at serum and water, measurements repeat 4-5 times and count arithmetic-mean value of Bm. Content of proteins in milk is determined by a formula: Bmol. % = Bm – Bs (2)
The general protein (proteins and nonprotein nitrogenous substances) is determined by a formula: Бо.б. = (Bm - Bs) *1, 0855 (3)
It is also possible to determine the content of casein, serumal proteins (albumine and globulin) in milk by a scale of " Squirrels". Content of casein in milk is determined by a formula: To % = (Bm - Bk.s.)*1, 1012, (4) where Bk.s. – the indication on a scale of " Squirrels" for casein free serum. For receiving casein free serum with milk (5 ml) bring 10 drops of 10% solution of acetic acid in a bottle. Content of serumal proteins is determined by a formula: % SB = Bm – K (5) Definition of the general protein in milk by Kjeldal's method. Place in Kjeldal's flask consistently several glass beads or pieces of porcelain, about 10 g of sulfate potassium, 0, 5 g of an oxide of mercury or 0, 04 g of sulfate copper. In a bottle with a cover measure 5 ml of milk, close a cover and weigh with an accuracy of 1 mg. The empty bottle is weighed again and on a difference between the mass of a bottle with milk and mass of an empty bottle establish the mass of the taken milk. Add 20 ml of sulfuric acid to a flask, pouring carefully on flask walls, washing away from them milk drops. The flask is closed a pear-shaped glass stopper and carefully roundabouts mix flask contents. The flask is put on the heating device in inclined situation at an angle 450 and carefully heated. Continue heating of a flask until foaming stops and contents of a flask don't become liquid. Then burning is continued at more intensive heating. Extent of heating is considered sufficient when the boiling acid is condensed in the middle of a mouth of a flask of Kjeldal. From time to time contents of a flask are mixed, washing away the charred particles from flask walls. Heating is continued until liquid doesn't become absolutely transparent and almost colourless (at application as the mercury oxide catalyst) or slightly bluish (at application as the catalyst of sulfate copper). After solution clarification heating is continued during 1, 5 h then to a flask allow to cool down to room temperature. Add 150 ml of the distilled water and several pieces of svezheprokalenny pumice, mix and again cool. In a conic flask measure 50 ml of solution of boric acid, add 4 drops of the indicator of Tashiro and mix. The conic flask is connected to the refrigerator by means of the allonge and a rubber stopper so that the end of the allonge was below the surface of solution of boric acid in a conic flask. Kjeldal's flask is connected to the refrigerator by means of the drop catcher passing through one stopper with a delitelny funnel. The graduated cylinder measure 80 ml of solution of a hydroxide of sodium (at application as the catalyst of a red oxide of mercury use the sodium hydroxide solution containing sodium sulfide) and through delitelny (or drop) a funnel bring him in Kjeldal's flask. At once after pouring out of solution close the crane of a delitelny funnel for avoidance of loss of the formed ammonia. Contents of a flask of Kjeldal are carefully mixed roundabouts and heated to boiling. At the same time it is necessary to avoid foaming. Continue distillation until liquid doesn't begin to boil pushes. At the same time regulate extent of heating so that time of distillation was no more than 20 min. It is possible to be convinced of completeness of distillation of ammonia by additional distillation in a new consignment of boric acid (20 ml) within 5 min. Coloring of solution of boric acid has to be left without change. At distillation don't allow heating of solution of boric acid in a conic flask. Too strong cooling (lower than +10 0C) is also undesirable as it can cause transfer of liquid from a conic flask in Kjeldal's flask. Before the end of distillation lower a conic flask so that the end of the allonge has appeared over the surface of solution of boric acid, and continue distillation within 1-2 min. Stop heating and disconnect the allonge. In a conic flask wash away external and internal surfaces of the allonge a small amount of the distilled water. Titrut distillate of 0, 1 N solution of hydrochloric acid before transition of green color to violet. In parallel carry out the control analysis as well as the main, applying 5 ml of the distilled water instead of milk. The control analysis is carried out in each series of determination of amount of protein and at each replacement of reactants. The mass fraction of the general protein (B) is calculated as a percentage to within the third decimal sign on a formula:
where 1, 4 – amount of nitrogen, equivalent 1 ml 0, 1 N of solution of hydrochloric acid, mg; 0, 1 – normality of solution of hydrochloric acid; V1 – the volume of 0, 1 N of the hydrochloric acid spent for titration of distillate in the main analysis, ml; V0 - the volume of 0, 1 N of the hydrochloric acid spent for titration of distillate in the control analysis, ml; 6, 38 – coefficient for transfer of a mass fraction of the general nitrogen to a mass fraction of the general protein; m – the mass of the milk taken on the analysis.
Report on performance of a task To present results of work in the form given in tab. 3.2
Control questions 1. Proteins of milk, their classification. 2. Methods of formal titration and Kjeldal, their chemical essence. 3. The Refraktometrichesky method on what properties of casein and serumal proteins it is based? Laboratory work № 4 Short theoretical data Determination of content of lactose by a refraktometrichesky method. Refractometry — determination of index of refraction, and refraction number – the conditional number showing refraction size in terms of a scale of this refractometer. The ray of light passing through various environments deviates the rectilinear way on a bigger or smaller corner depending on properties of the environment through which he passes. Definition of a mass fraction of lactose by a polarimetric method (according to G. Vizhinayta). Existence in molecules of sugars, in particular, of lactose, asymmetric carbon atoms does them optically active, that is capable to rotate the plane of the polarized light. This property is function of concentration of water solutions of carbohydrates therefore, measuring an angle of rotation α, it is possible to define concentration of lactose. Solutions for polarimetric researches have to be transparent therefore apply acetic zinc and zhelezistosinerodisty potassium to sedimentation of proteins and fat. Determination of calcium complexometric method (byDudenkov).The method is based on instant education the slabodissotsiirovannykh of complex connections of various cations with trilonom-B (disodium salt of etilendiamintetrauksusny acid). Various metals, irrespective of valency, react with trilonom-B in the molar relation 1: 1. All intra complex connections are very steady also rastvorima in water. When determining calcium use the indicator mureksidy. Mureksid forms complex connection of intensively red color with calcium. However this connection is less steady, than complex compound of calcium with Trilonom-B. Therefore at complexometric titration in an equivalence point cations of calcium disappear and there is a sharp change of coloring of solution in lilac to a bluish shade. Solutions, titrable trilonom-B with application of a mureksid, alkalinize a caustic natr to рН not lower than 12. Equipment, devices and technical means: Refractometer, bath water, SU-4 saccharimeter; calcium chloride 4% solution, sodium hydroxide 8% solution, trilon-B 0, 1n solution, calcium 0, 1n chloride solution, indicator мурексид, solutions of acetic zinc and zhelezistosinerodisty potassium, solution of bromnovatokisly potassium 0, 2n; pipettes of 5 ml, test tubes on 10 ml, flasks conic with a capacity of 200-250 ml, 100 ml, flasks measured with a capacity of 100 ml, cylinders measured, burettes. Work performance order Determination of content of lactose by a refraktometrichesky method. Measure a pipette in a test tube 5 ml of the studied milk, add 5-6 drops of 4% solution of chloride of calcium. Test tubes close traffic jams and place in a water bath with the boiling water for 5 min., then cool them to 15 °C, at the same time pay attention to that drops of the condensed water didn't remain on test tube walls. Then open a stopper and carefully extend serum in a glass tube which lower end is closed by cotton wool for a serum filtration. The drop of transparent serum is applied on a surface of the lower prism of the refractometer and slowly lower the top prism and take measurements. The mass fraction of dairy sugar in milk is found according to tab. 4.1 Table 4.1 - Dependence of a mass fraction of lactose in milk from index of refraction
Definition of lactose in milk by the accelerated method. To neutralize the filtrate received in the previous experience sodium hydroxide solution before alkalescent reaction on the indicator a fenolftaleina. To halve a filtrate. In a pure test tube to pour 2 ml of solution of sodium hydroxide and on drops to add when stirring solution of sulfate of copper (II) before emergence of a deposit of hydroxide of copper (II) of blue color. The received mix to shake up and add the first half of a filtrate. Emergence of bright blue coloring indicates presence at a lactose filtrate. When heating coloring of solution changes till red color. To evaporate the second part of a filtrate in a porcelain cup. Education on walls of a cup of a brown raid with a characteristic caramel smell indicates lactose presence. Definition of a mass fraction of lactose by a polarimetric method (according to G. Vizhinayta). In a glass on 100 ml weigh 33 g of milk with an accuracy of 0, 01 g. Milk is quantitatively transferred to a measured flask with a capacity of 100 ml, rinsing a glass with the distilled water. In a flask flow 5 ml of acetic zinc and zhelezistosinerodisty potassium. Flask contents after addition of each reactant are carefully mixed, without stirring up in order to avoid formation of vials of air. Then flow 25 ml 0, 2n solution of bromnovatokisly potassium, carefully mix. Contents of a flask are brought the distilled water to a tag and carefully mixed, strongly stirring up. In 5-10 min. filter via the dry folded filter in a dry flask. The filtrate is polarized in a polarimetric tube 400 mm long. Counting is carried out by 3-5 times and take arithmetic-mean. Content of lactose is calculated on a formula: L= where P — the indication of a saccharimeter; K — the amendment on deposit volume. Calcium definition by a kompleksonometrichesky method (across Dudenkov). To 5 ml of milk in a chemical glass flow 90-95 ml of the distilled water, 5 ml of 8% NaOH solution and from the burette measure precisely 3, 5 ml 0, 1n solution trilona-B, mix a glass stick and leave for 2 min. Bring about 0, 04 g of dry mix of the indicator of a mureksid with chloride sodium on a knife tip (1 part of a mureksid carefully pound with 50 parts of chemically pure chloride sodium). Solution is painted in lilac color. Contents are titrut 0, 1n CaCI2 solution, adding him on drops at continuous hashing before emergence of steady pink coloring. Then from the burette flow when stirring on drops solution trilona-B before emergence of steady lilac color again. In 1 min., in case of coloring disappearance, add 1 more drop Trilona-B. From the total amount of solution trilona-B, spent for the first and second titration and counted on precisely 0, 1n solution, subtract volume 0, 1n the CaCI2 solution spent for the return titration and find volume trilona-B, the milk connected with calcium. Content of calcium in mg of % is calculated by a formula: Ca= where and – quantity 0, 1n solution trilona-B, connected with calcium, ml; 2 amount of calcium, corresponding 1 ml 0, 1n solution trilona-B, mg; 5 – the volume of the milk taken for the analysis, ml. Control questions 1. Characteristic of lactose as main carbohydrate of milk. 2. Mineral substances of milk: macro - and minerals. 3. Methods of definition of lactose in milk. 4. Kompleksonometrichesky method of definition of calcium, his chemical essence. Laboratory work № 5 Studying of a method of determination of content in vitamin C milk (ascorbic acid) and enzymes
Work purpose: to determine the content of vitamin C and enzymes in various samples of milk. Task 1.To carry out high-quality reaction to vitamin C. 2. Quantitative definition of vitamin C 2, 6-dikhlorfenolindofenoly (on Tilmansa) Short theoretical data Vitamins. Milk contains all vital vitamins, but some in insufficient quantities. Content of vitamins depends on a season of year, breed of animals, quality of forages, storage conditions and processing of milk. Fat-soluble A, D, E, K vitamins and (V-carotene are steady against heating and begin to collapse at a temperature over 120 °C (vitamin A), but aren't steady against effect of air, ultraviolet rays and acids. Vitamin A gives to butter yellow color. Vitamin E is antioxidant of fats and protects vitamin A from oxidizing destruction. Water-soluble vitamins, except for vitamins C and B12, are steady against heating. They maintain heating in the alkaline environment worse. RR vitamin almost completely remains after thermal treatment and in the course of milk storage. Most collapses at pasteurization and storage vitamin C. Vitamin C (ascorbic acid). She participates in an oxidizing voskstanovitelnykh the processes happening in an organism. The lack of a viktamin With in food can cause a scurvy. Raw milk contains 0, 3 - 2, 0 mg of % of vitamin C. Vitamin C sinktezirutsya by hem microflora, his content in milk depends from the inkdividualnykh of features of an animal. Usually it raises in the winter and goes down in the summer. At milk storage the amount of ascorbic acid decreases. Light affects destructively ascorbic acid therefore at a milk hrakneniye in transparent bottles of loss of vitamin C make 50% and more. Better vitamin B bottles from dark glass and paper packages remains. It is important to consider it at production of vitaminizirovankny milk and dairy drinks. Enzymes (Latin fermentum - ferment) - the biological katalizaktor accelerating chemical reactions in live organisms. Under a deykstviye of enzymes large molecules of proteins, carbohydrates, fats rasshchepklyatsya on smaller. Enzymes accelerate reactions in tens of thousands and millions of times. Deykstviye of enzymes it is strictly specific, i.e. each enzyme catalyzes only one chemical reaction. Enzyme corresponds to the subkstrat (substance which chemical transformation he catalyzes). Enzymes work at a certain temperature, рН Wednesdays; their activity depends on availability of chemicals - activators and inhibitors. Opktimalny temperature, i.e. temperature at which the maximum of activity of enzymes is observed for most of them is equal to 40 - 50 °C. At further temperature increase activity of enzyme snizhaktsya. At a temperature of 60-80 °C of squirrels, the forming enzyme, denaturikrut, and enzyme is inactivated (loses the activity). The thermal denaturation of enzymes has important practical znachekny: pasteurization of raw materials promotes destruction of enzymes and predokhranyat foodstuff from enzymatic damage. The important factor influencing activity of enzymes is рН Wednesdays. Enzymes differ on optimum for their action to znachekniya рН. At too sour or alkaline reaction of the environment the enzyme denaturation proiskhokdit, and it loses the activity. By the chemical nature enzymes represent proteinaceous substances. They can be simple and complex proteins. Enzymes nakzyvat on that substance which they affect, adding the termination " az" to a name root: lipase, lactase, peptidaza and so forth. In milk enzymes are in a free state, and also are connected with casein micelles and covers of fatty balls. Devices and equipment Conic flasks with a capacity of 250, 100, 50 ml; scales; pipettes on 5, 10, 25 ml; burette; microburette; a funnel, the folded filter, solution with a mass fraction of metaphosphoric or hydrochloric acid of 2%; saturated solution of oxalic acid; saturated solution of chloride of sodium, 2, 6-dikhlorfenolindofenol; methylene blue, a reduktaznik, a water bath, 0, 1% solution of a fenolftaleinfosfat of sodium in ammoniac buffer mix. Work performance order Essence of a method: the chemical method of definition of vitamin C 2, 6-dikhlorfenolindofenoly (Tilmans's paint) is based by the specific indicator on properties of this indicator to change the coloring depending on reaction of the environment. In acidic environment the indicator gets pink coloring, in alkaline and neutral - blue. Being restored, the indicator becomes colourless. Decolouration of the indicator in the presence of vitamin C is explained by easy oxidability of vitamin. Carrying out experience: To part 5 ml of milk by 3 times with water. At cultivation to measure milk a pipette, to pour the distilled water from the burette. To bring 1 ml of 2% in a conic flask with a capacity of 50 ml hydrochloric acid of 5 ml of the received milk solution, to bring water to the total amount of 15 ml. Carefully shaking up, contents of a flask titrut from the microburette 0, 001 N solution of a 2, 6-dikhlorfenolindofenol, flowing him drops before emergence of the weak-pink coloring remaining 0, 5-1 min. To make two parallel definitions of one portion of the divorced milk and to find average size. To determine the content of vitamin C by a formula: х = where u - the amount of working solution 2, 6 dikhlorfenolindofenol which has gone for titration, ml; k - the amendment on a solution 2, 6 caption dichlorine-fenolindofenola; V- the volume to which the milk hinge plate at addition to her of water and hydrochloric acid is brought, by ml; V1 - the volume of the analyzed liquid taken for titration, ml; q - milk hinge plate; 0, 88 - amount of vitamin C, corresponding 1 ml 0, 001 N of solution 2, 6 dikhlorfenolindofenol, mg. Test on phosphatase Add 1 ml of 0, 1% solution of a fenolftaleinfosfat of sodium in ammoniac buffer mix (80 ml 1 N of solution of ammonia and 20 ml 1 N of solution of chloride of ammonium) to 2 ml of milk, heat on a water bath (40 — 45 °C) and check coloring of contents of a test tube in 10 and 60 min. If phosphatase is destroyed, i.e. milk is pasteurized, his color doesn't change. Light-or bright pink coloring demonstrates violation of the mode of pasteurization. The report on the done work To present results of work in the form given in tab. 5.3 and to write conclusions about the content of vitamin C and enzymes in various samples of milk. Table 5.3
Control questions: 1. What vitamins contain in milk? 2. Essence of a technique of definition of enzymes in milk 3. What is enzymes?
Laboratory work № 6 Short theoretical data
Pasteurization – the most widespread way of processing of milk. Pasteurization has possible to destroy pathogenic and vegetative microflora and to make milk and dairy products harmless to consumption. However any thermal impact on dairy raw materials is reflected both in separate components of milk, and in milk as to polydisperse system in general. Therefore it is necessary to select carefully the modes of thermal treatment at technological processing as much as possible to keep the biological value of dairy products. Pasteurized call the milk subjected to thermal treatment at certain modes and then cooled. Production of pasteurized milk, despite a variety of his types, consists generally of operations, identical to all types of milk: acceptance and assessment of quality of raw materials; raw materials preparation; normalization; cleaning; homogenization; pasteurization; cooling; fasovaniye and packing; marking; storage and realization. The technological scheme of production of the milk pasteurized
Acceptance and assessment of quality of raw materials
Purification of milk
Milk reservation
Milk normalization
Homogenization
Milk pasteurization
Cooling
Fasovaniye, packing and marking
Storage and realization
The efficiency of pasteurization caused by extent of death of pathogenic microflora influences the choice of the modes and ways of pasteurization (t, ° C and time τ, c), the interrelation of which is established in the form of the following equation: lnτ = á – β t; where τ -time of influence of temperature, with; á, β – coefficients which, according to Cook, for a tubercular stick have according to value 36, 84 and 0, 48; t – temperature of pasteurization, ° C. Depending on these factors appoint three modes of pasteurization: - long – at t = 60-63o With with endurance of 1800 with (30 min.); - short-term – at t temperature = 74-78o With with endurance 20 with; - instant – at t = 85-87 about With or t = 95-98o With without endurance. The choice of the mode of pasteurization is defined by technological conditions and properties of a product, and also an indicator of heat stability of milk. To establish whether pasteurization milk was exposed, whether there was a thermal treatment enough, conduct researches on availability of enzymes of phosphatase and peroxidase. Enzymes are quite sensitive to heating that allows to determine efficiency of various ways of thermal treatment of milk by degree of their inactivation. Long and high-temperature pasteurization destroy alkaline phosphatase therefore presence of active phosphatase at pasteurized milk indicates or low-quality pasteurization, or hit of raw milk after thermal treatment. As the temperature maximum of destruction of phosphatase is higher than a temperature maximum of destruction of pathogenic microorganisms and toxins, negative reaction to phosphatase reliably protects the consumer from a possibility of spread of diseases through milk and dairy products. Peroxydase enzyme more thermostable. It collapses at a temperature of 75 ° C with endurance of 10 min., at 80 ° C with endurance 20-30 with or 85o With without endurance therefore on peroxidase it is possible to determine efficiency only of high-temperature pasteurization by test. Also lactoalbumin test can be applied to definition of efficiency of high-temperature pasteurization of milk. She serves for establishment of pasteurization at a temperature over 80 ° C. Equipment, devices and technical means: Milk tests, chemical ware (pipettes, test tubes, droppers, measured cylinders), a water bath, an electric tile, holders, solution of yodistokaliyevy starch, 0, 5% - ny solution of peroxide of hydrogen, working solution for definition phosphotazy, a system precipitator zinc-copper, the distilled water. Work performance order Laboratory work №7 Short theoretical data Euphorbia serum turns out as a by-product by production of proteinaceous products. In many countries serum is used in production of ice cream, bakery and confectionery, products of baby food, medicines. Considerable volumes of whey go for production of the condensed and dry concentrates, and also forages for animals. Drinks belong to one of the biggest assortment groups of products of whey. Nutrition value and biological properties of whey allow to use her directly as drink or, after preliminary processing, as raw materials for preparation of various drinks. In drinks from whey there is no casein and milk fat, in separate types of drinks also serumal proteins can be removed. At the same time separate groups of drinks can be enriched with proteins of milk due to addition of buttermilk, skim milk or dairy proteinaceous concentrates, and also products from vegetable raw materials (soy, etc.). The mineral and microelement composition of whey approaches structure of mineral water, but considerably surpasses her in nutritional value. Therefore drinks from serum not only promote a satisfying of thirst and maintenance of water-salt balance, but also are nutritious. Technological process of production of drinks of the native not fermented serum is carried out in this sequence: - acceptance, assessment of quality and preparation of raw materials; - pasteurization and cooling of serum; - introduction of nutritional supplements and sugar syrup; - pasteurization and cooling of mix; - fragrance introduction (if necessary); - hashing and cooling of mix; - pouring, packing, marking, dookhlazhdeniye of a ready-made product. In the clarified serum specific serumal smack is weakened, and from it receive the transparent refreshing drinks. Biological processing of whey leads to change of its structure, accumulation of organic acids, water-soluble vitamins, lactates, flavoring and aromatic substances, allows is directed to change a ratio of " belok: uglevoda" in the desirable party and to improve taste of the developed drinks. Technological process of production of the fermented drinks of serum is carried out in the following sequence: - acceptance, assessment of quality and preparation of raw materials; - pasteurization and cooling of serum; - introduction of nutritional supplements and sugar syrup; - pasteurization and cooling of mix up to the zakvashivaniye temperature; - zakvashivaniye and souring; - fragrance introduction (if necessary); - hashing and cooling of skvashenny mix; - pouring, packing, marking, dookhlazhdeniye of a ready-made product. On organoleptic indicators drinks from whey have to conform to the requirements provided in table 7.1 Organoleptic indicators of drinks from whey Table 7.1
Drinks from whey have to meet for physical and chemical indicators the requirements provided in table 7.2. Work performance order Research methods.Organoleptic and physical and chemical indicators (a mass fraction of fat, acidity) of drinks – by standard methods. In our country from secondary dairy raw materials both " fresh", and sour-milk develop drinks. Mean the products developed from the raw materials which have undergone biological processing by souring by his true cultures of lactic bacteria by dairy drinks. Unlike curdled milk they have to have the destroyed clot and a liquid or semi-fluid consistence. Let's get acquainted with technology of preparation of some of them. Low-fat milk. Technological process is similar to production of cow's pasteurized milk. Skim milk acidity not higher than 19 °Т, will be pasteurized at a temperature of 76-78 °C with endurance 20 with or at 85-87 °C without endurance and cool up to 4-6 °C. The ready-made product has to have true taste and a smell without any strangers unusual for fresh milk, smacks and smells, to represent uniform liquid without deposit, white color with slightly bluish shade. In low-fat milk there have to be not less than 8, 1% of solids. Acidity of a ready-made product shouldn't be higher than 21 °Т. Drinks from serum develop both from not clarified serum, and from the thermal denaturation clarified after release of serumal proteins by method at 90-98 °C with endurance 1-2 hours or membrane methods. Drinks from not clarified serum contain all components of whey. Their technology is rather simple. These drinks opaque and in them loss of a flaked deposit is possible. The pasteurized whey is produced from cottage cheese serum with addition or without addition of flavoring and aromatic substances. The compounding (in kilograms) on the pasteurized whey with fillers on 1 t of a ready-made product (without raw materials losses) is presented in table 7.3 Laboratory work №8 Short theoretical data To cause lactic fermentation by production of fermented milk products, kisloslivochny oil and cheese, apply true bacterial cultures. Bacterial cultures usually produce in a look dry and liquid (seldom), kotoryesokhranyayutsyado10-14 days on cold, an expiration date of dry cultures – more 2-hmesyaets. At the plant, as well as in laboratory, prepare maternal (the main, initial or primary), transfer (secondary) and production (worker) ferment. All stock has to be sterile. Equipment, devices and technical means: the thermostat, pans, the electric stove, scales with weights, glasses, circles of parchment, ferment dry. Work performance order Technology of preparation of sour-milk ferments Maternal ferment. 1. Milk to proseparirovat and receive about 2 l of skim milk (to remove foam with a pure spoon). 2. To pour in milk in a flask, to close a wadded stopper, to propasterizovat in water at 90-95 °C within 30 min. 3. In the same ware to cool milk to 30 °C (in cold water). Temperature of milk is taken the thermometer without wooden frame. At preparation of ferment for acidophilus milk to cool up to 45 °C. 4. The film formed on the surface of milk is removed a sterile metal spoon. 5. To pour dry or to pour in liquid laboratory culture in milk, at the same time mixing it a verticil. Contents of a flask are mixed roundabouts. 6. To close ware a gauze or parchment and to put in the thermostat or in a vessel with water, where to maintain temperature 28-30os. The culture for acidophilus milk and yogurt is maintained at 40-45 °C. If milk was fermented in a flask, then it should be placed in the thermostat. 7. The first three hours to mix milk in each hour, then to cover capacity with a gauze. Final souring occurs cherez12-18ch. Maternal ferment is stored at a temperature of 10 °C. Her clot has to be quite dense, acidity – 65-70 °Т. Taste and aroma pure, accurately expressed. Transfer (secondary ferment) 1. To prepare skim milk also, as well as for maternal ferment (to pasteurize, remove foam, okhladitdo25-27 with °C). At preparation of ferment for acidophilus milk and yogurt temperature of milk has to be 40-45 °C. 2. To skim with maternal ferments a sterile spoon (2-3rd). To stir the remained clot a verticil to a smetanoobrazny state. To shake up contents of a flask. 3. To bring a pure beaker or the cylinder in prepared fat-free moloko2-3 by % of maternal ferment. 4. Folding of transfer (secondary) ferment comes in 8-14 h. Ferment has to have pleasant taste and aroma, acidity within 90-100 °. It is necessary to store this ferment at a temperature of 10 °. In maternal and transfer ferments of a bacterium are still insufficiently active therefore the third change is necessary for receiving working (polzovatelny) ferment. Working ferment is prepared similarly transfer, it is only necessary to reduce souring temperature to 20-24 °C, for acidophilus milk till 38-40 °. These ferments are usually ready in 6-10 h. Ready working ferment has to have sour-milk true taste and a smell, a uniform consistence, to be without vials of gas and foreign smacks and smells. Apply a so-called two-row way to respect for purity. From the main ferment at the same time train the main and working again. Working ferment every time ferment new the main. At such way remain more long time of property of the main ferment, and working ferment turns out quality. Laboratory work №9 Short theoretical data Dietary fermented milk products of all types develop according to the general technological scheme. The prepared milk skvashivatsya by ferments of true cultures then the received clot is cooled and ripens. Distinctions by production of separate types of products can be in temperature conditions of preparation of milk, souring and maturing, and also in use of ferments of various structure and introduction of fillers. Develop liquid fermented milk products in the thermostately and reservoir way according to the technological scheme (figure 1.1). When carrying out process of normalization the mass share of fat of ferment which is contributed in milk is considered. A mass fraction of fat to which it is necessary to normalize milk, determine by a formula:
where Zhn.M. – a mass fraction of fat in the normalized mix, %; Zhpr. – a mass fraction of fat in a ready-made product, %; Кз – the mass of the brought ferment, %; Жз – a mass fraction of fat in ferment, %. When using ferment of direct introduction the mass fraction of fat of the normalized mix is equal a mass fraction of fat of a ready-made product. By production of fermented milk products with fillers the composition of mix is counted on compoundings. |
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