Production of kefir by tank method

1 Ism. Kol.uh Signature Date Sheet 1 OP 01.00. PP Razrab. Kosik N.I. Prov. Ruchay N.S. Review. Ruchay N.S. N. counter. Ruchay N.S. Utv. Leontiev V.N. Technology of production of fermented milk products Lit. Sheet 17 BGTU 71406005, 2018 Sheet No. Doc at Sour Milk Products Production Technology 1.1 Process Description The process of kefir production by tank method includes the following operations: - acceptance and preparation of raw materials; - mix normalization; - purification of mix; - mix homogenization; - pasteurization and cooling of mix up to the zakvashivaniye temperature; - zakvashivany mixes; - souring of mix in special tanks; - hashing, maturing and cooling of a clot; - pouring (packing) and dookhlazhdeniye. Hardware diagram of kefir manufacturing process is given in Appendix 2. Raw material acceptance and preparation shall be accepted by weight and quality established by the manufacturer's laboratory in accordance with the requirements of STB 970. The milk should be free from extracts and additives of dairy and non-dairy components, subjected to primary treatment. Milk is cleaned from mechanical impurities at temperature of supplied milk on centrifugal milk cleaners and (or) filtration. After cleaning, the milk is cooled to a temperature of (4 ± 2) ℃ and sent to industrial processing or to intermediate storage tanks (if necessary). Milk of not less than first grade, acidity not more than 19 ° T, density not less than 1027 kg/m3 is used for production of fermented milk beverages. Milk separation is started after its arrival in amount ensuring continuous operation of separator. Milk is separated on all types of separator-cream separators in accordance with the rules of their operation set out in the manufacturer's instructions, in compliance with the existing sanitary norms and rules. The optimal separation temperature is (40-45) ℃. It is allowed to separate milk under other temperature conditions depending on the equipment used. Defatted milk and cream obtained during separation are sent for processing, including normalization, or, if necessary, to intermediate storage tanks after cooling to a temperature of (4 ± 2) ℃. It is allowed to store raw milk, raw defatted milk (including the storage period of raw milk used for separation) at a temperature of (4 ± 2) ℃ and raw cream at a temperature of not more than 8 ℃ not more than 36 h (including transportation time) before the start of industrial processing. During storage, temperature and acidity of raw milk raw materials are determined every 2 hours. Before sampling, it is thoroughly mixed during (5-10) minutes. Storage of dry, condensed or concentrated milk, dry cream, buttermilk, milk permeate is carried out in accordance with TNPA per specific product. Normalization of the mixture The normalization of milk (except for the manufacture of whole milk kefir) is carried out in such a way that the weight fractions of fat and protein in kefir meet the requirements of STB 970. Defatted milk intended for production of defatted kefir is normalized by weight fraction of protein, if necessary. Milk is normalized by weight fraction of fat: - in the reservoir by adding to whole milk:· defatted milk;· cream. - using the separator-normalizer in the flow. The milk selected by quality is normalized so that the mass fraction of fat in the finished product is at least the mass fraction of fat specified in the specifications. When using starter prepared on defatted milk, the milk is normalized to a higher weight fraction of fat before fermentation.Milk is normalized according to the protein weight fraction by the following methods: - increasing the protein weight fraction in milk by adding dry condensed or concentrated milk; - reducing the protein weight fraction in milk by adding milk permeate obtained by removing defatted milk proteins by ultrafiltration. Powdered milk is previously dissolved in the normalized milk taken from lump, at a temperature (38-45) ℃. The mixture is filtered to purify large undissolved lumps, then added to the bulk of the milk to be normalized and thoroughly mixed. Condensed or concentrated milk is added directly to the milk to be normalized and thoroughly mixed. The process of ultrafiltration of defatted milk, including preliminary pasteurization, is carried out in accordance with the operating instructions of the ultrafiltration units and the manufacturer's process instructions, respectively. Cleaning, deaeration of mixture Centrifugal cleaning - cleaning from mechanical impurities in separators-milk cleaners. It allows you to remove not only mechanical impurities from milk, but also mucus, milk clots, epithelium, shaped blood elements. Amount of extracted impurities reaches 0.02-0.06% of milk weight passed through milk cleaner. The optimum centrifugal cleaning temperature is 50-55 ° C. The principle of operation is based on the difference in densities of milk plasma particles and mechanical impurities. They settle under the influence of centrifugal force and are removed from milk. The cleaning process itself takes place in the drum of the separator in the interstage space. When milk is fed into the drum, mechanical impurities having high density are thrown to the periphery. Milk as a lighter part creates a flow in the center of the drum (near the axis of rotation). Mucus contains mud, protein and bacterial layer. Milk cleaning is carried out with heating (50-55℃). As the temperature increases, the viscosity of the milk decreases and impurities are easily removed. Homogenization of the mixture Homogenization - treatment of milk to disperse (crush) fat beads. The intensity of homogenization increases with increasing temperature as the fat becomes liquid and the viscosity of the product decreases. The mixture (except for defatted milk) is homogenized at a pressure of (15 ± 2.5) Mpa and a temperature of (45 + 85) ℃ in order to prevent spontaneous settling of fat, increase the moisture retention of the clot, improve the taste and consistency of kefir. It is allowed to perform homogenization at pasteurization temperature or to apply separate homogenization of normalized mixture (cream). Pasteurization and cooling of mix up to the zakvashivaniye temperature will pasteurize Mix at the following modes: - (85-89) ℃ with endurance (10-15) mines; - (92±2) ℃ with endurance (5-6) min. Double pasteurization of mix is allowed: at first at a temperature (76±2) ℃ with endurance to 25 with, and then at a temperature (92±2) ℃ with endurance to 25 pages. The pasteurized mix is cooled up to the zakvashivaniye temperature (18-25) ℃. During pasteurization, foreign microbiota is inactivated and thermolabile fractions of serum proteins are isolated. At the same time, there is denaturation of serum proteins, which, when fermented, coagulate together with casein. At the same time, the hydration properties of casein are increased, the clot better retains the serum and does not settle during storage of sour milk beverages. The pasteurized mixture is not allowed to be stored at the fermentation temperature without leavening. Fermentation of the mixture, as well as fermentation (for the reservoir method) of the mixture is carried out in reservoirs for fermented milk products or in other containers equipped with special mixers and a cooling jacket, providing uniform mixing of the mixture with starter, maintaining optimal temperature for the development of starter microorganisms, mixing and cooling of the fermented mixture.The temperature of the mixture during fermentation should be in the range: - (18-21) ℃ - in the warm season; - (22-25) ℃ - in the cold season. In order to avoid foaming, which affects the separation of serum during storage of kefir, the mixture is supplied to the reservoir through the lower nozzle. Starter on kefir fungi is thoroughly mixed and added to the mixture in the following amount from fermented mass: - up to 3% - plums from kefir fungi, acidity (95-110) ° T; - up to 5% - production starter, acidity (95-100) ° T. Starter is introduced in flow with the help of dosing pump simultaneously with supply of mixture into reservoir for fermentation. When feeding the mixture into the tank with the starter available there, in order to avoid instantaneous coagulation of the protein and the formation of a coarse kefir consistency, it is recommended to supply the first portions of the mixture with a temperature of (2-4) ℃ below the sourcing temperature, the next portions of the mixture are supplied with (2-4) ℃ above the sourcing temperature. For better mixing of the mixture with the starter, the tank is filled with the stirrer turned on. The stirring is finished after (15 ± 2) minutes after filling the tank. It is allowed to add starter to the tank after filling it in small portions with the stirrer on. The mixing is finished after (15 ± 2) minutes after the starter application. After mixing the mixture with starter, it is left at rest for digestion at a temperature of (18-25) ℃ for (8-12) hours. During digestion, it is necessary to maintain the temperature of the mixture accurately since its fluctuations can lead to the formation of a non-uniform clot. When making kefir in the cold season, it is recommended to set the fermentation temperature to 25 ℃ to increase the viscosity and obtain a product with a dense uniform clot. An increase in the fermentation temperature above 25 ℃ is not recommended, since this accelerates the development of lactococci, but slows down the growth of yeast and aroma-forming microorganisms, which leads to the production of kefir with an unspoiled taste resembling the taste of downtown. The end of the digestion is determined by the formation of a strong clot and acidity, which should be in the range of (85-10) ° T or pH (4.65-4.5). Agitation, maturation and cooling of the clot After the completion of the digestion, ice water with a temperature of (2 ± 1) ℃ is supplied to the interwall space of the tank, in order to cool the clot to a temperature of (14 ± 2) ℃ and suppress acidity growth. After (30-60) minutes after the ice water supply, the stirrer is turned on and the clot is stirred for (10-30) minutes until a uniform consistency is obtained. After that, the mixer is stopped for (60-90) minutes. Further mixing is carried out periodically, including the mixer for (2-10) minutes every hour, until the clot temperature reaches (14 ± 2) ℃. The duration and multiplicity of mixing depends on the density of the clot and the cooling intensity. The mixed and cooled to temperature (14 ± 2) ℃ clot is left at rest for ripening for (9-13) hours, before turning off the water supply to the interwall space of the tank. During ripening, carbon dioxide, volatile acids, traces of alcohol accumulate, as a result of which kefir acquires specific taste properties. After maturation, the kefir is cooled to a temperature (4 ± 2) ℃ in a stream using plate or tubular heat exchangers. Plate heat exchanger shall have large clearance between plates (up to 6 mm). The lowest clot density loss is observed when the kefir is cooled in the tubular cooler. Purge is used to reduce the loss of kefir. When pumping, the destruction of the clot should be minimal, so it is necessary to avoid long narrow pipelines with a large number of valves, which can lead to significant pressure drops. Special volumetric pumps shall be used with safety valves as close to the tank as possible. Bottling (packing) and post-cooling. Kefir cooled to temperature (4 ± 2) ℃ is mixed in the tank for (2-5) minutes and sent for bottling to consumer packaging.The packed kefir is placed in a refrigerating chamber, after which the process is considered complete and the kefir is ready for implementation. In case it is not possible to ensure intensive cooling of the clot to a temperature of (14 ± 2) ℃ with two, three times stirring for (4-6) hours, it is allowed to direct the kefir for bottling at a temperature of (20 ± 2) ℃ after thorough mixing for 20 minutes, followed by ripening and post-cooling in the refrigerating chamber at a temperature of (4 ± 2) ℃ provided that the finished product meets the requirements of STB 970. At the same time, the total duration of clot ripening and ripening should be at least 24 h. After ripening and post-cooling of the packed kefir to a temperature of (4 ± 2) ℃, the technological process is considered completed and the kefir is ready for implementation [2.13].