Aseptic packaging of UHT milk produces a shelf-stable product. (*, |) : mean values calculated from respectively 6 and 3 repetitions and mean standard deviation. Two starting procedures for the continuous prefermentation in the pilote bioreactor were tested with UHT milk : a first starting procedure using a varying milk flow rate (6 repeated trials) and a second starting procedure using an initial 30 min period with a fixed milk flow rate (3 repeated trials), corresponding to the pseudo steady state dilution rate (15 h- 1) observed with the UHT milk. The exact mechanism behind the age gelation process is still being debated as it apparently involves many complex reactions including acidification, the Maillard reaction and enzymatic and physicochemical proteolysis (Gaucher et al., 2008). A partial washing out of the reactor probably occurres at the beginning, which is more important with an initial fixed flow rate than with a varying flow rate. In Europe there is no legislative body specifying criteria for classification of these types of machinery, but VDMA (2006) has proposed a distinction between Class IV and Class V machines (Table 6.2). If, nevertheless, such faults occur, it must be ensured that contaminated packages are either avoided or detected and discarded. This method is used in commonly purchased milk (UHT milk). Copyright © 2020 Elsevier B.V. or its licensors or contributors. HTST pasteurization heats the milk to 161 degrees Fahrenheit for 15 seconds and then rapidly cools it to 39 degrees. Ultra-high temperature, or UHT, milk is ultra-pasteurized milk that comes in sterilized containers. Furosine, which is an indirect index of protein-bound lactulosyl-lysine (Erbersdobler and Hupe, 1991), is an useful indicator of heat damage in milk, because it is increased by prolonged heating or inadequate storage. Ultra-high-temperature (UHT) pasteurization involves heating milk or cream to 138°to 150° C (280° to 302° F) for one or two seconds. Depending on specification and application, high-acid aseptic filling machines may differ considerably from those approved for low-acid applications with regard to required microbial safety (especially against bacterial spores), the required safeguards against operating error and the level of in-process control. Use of low concentrations of hydrogen peroxide is beneficial in terms of cost and safety issues. Treating milk at Ultra-high temperatures results in several benefits that include the following. Figure 2. UHT pasteurization. The UHT treatment ensures maximum microbic inactivation, while preserving the maximum flavor, taste, and nutritional value. As the actions of heat-resistant proteases can contribute to the age gelation of UHT milk, the inhibitory effects of glycosylation on the activity of proteases such as plasmin (Doi et al., 1979) may be important for prolonging shelf life. Both methods result in milk that is 99.9% free of bacteria. There has been a tremendous growth in plastic bottles for liquid foods in recent years and PET or HDPE bottles are available for standard shelf-life, ESL and aseptic applications. McPhee, M.W. C. Perez-Locas, V.A. Information about the chemical changes occurring during the storage of UHT milk (the MR included) and their importance for sensory properties and nutritional value, in connection with the establishment of uniform legislation within the European Community regarding UHT-milk shelf-life, may be found in a review by Glaeser (1989). Similar definitions are provided by FDA (2007) and VDMA (2006). UHT is a process where the milk, juice, beer, wine, beverage etc is heated to approx 145 degrees C and held there for some two seconds. The stability of milk against coagulation at sterilization temperatures has commercial importance in the manufacture of UHT milk and milk-containing products, such as concentrated milk. Pasteurized milk having previously supported growth of psychrotrophs to levels of 5.5 log cfu ml−1 has been described as having an inferior flavour. However, the pH and the dilution rate are remarkably stable after 1 h of operation with the 2 tested procedures. However, in many European nations, UHT milk is the norm. From these results it was possible to derive an equation for the prediction of the shelf-life of these products. By navigating this website, you agree to our Privacy Policy and Terms of Use. In general, the overall keeping quality of milk (pasteurized and UHT) and other dairy products is mainly limited by the action of proteinases and lipases. c) UHT treatment UHT treatment means a very short heat treatment at temperature of approximately 140°C (135 -150˚C) for only a few seconds. Ultra-high temperature, or UHT, milk is ultra-pasteurized milk that comes in sterilized containers. It is used for low acid (above pH 4.6) products such as UHT milk, UHT flavoured milk, UHT creams, soya milk and other dairy alternatives. Ultra high temperature (UHT) milk is used as a sterilized milk by heating raw milk above 135 degrees Celsius to kill germs and spores present in the milk. For a product to be considered Ultra Pasteurized (UP), it must be heated to not less than 280° for two seconds. The process for shelf-stable milk is called UHT pasteurization, or Ultra High Temperature. Postpasteurization contamination at very low levels by Pseudomonas spp., however, is more detrimental to the keeping quality of pasteurized milk at 4–8 °C than the number of bacteria in raw milk. Every year in Germany, approximately 27 billion tons of milk located at 112 production plants will be worked up into different products (milk, yogurt, curd, butter, cheese, etc.). Perhaps the biggest disadvantage of ultra high temperature pasteurization is its effect on the taste of milk. Temperature Calibration in UHT Milk Production. Storage time: It can be stored for more than 30 days at a normal temperature. Aseptic filling machines must be designed to fill low-acid products (i.e. Kelly and Foley (1997) showed that independent of the somatic cell count in the milk, only low plasmin activity remained upon pasteurisation at ultrahigh temperature (UHT, 138 °C for 2.4 s). Griffiths, in Encyclopedia of Dairy Sciences, 2002. The official U.S. government definition of an ultra-pasteurized dairy product stipulates “such product shall have been thermally processed at or above 280° F for at least 2 seconds, either before or after packaging, so as to produce a product which has an extended shelf life.” The milk is processed at above 135 °C (275 °F) to eradicate all the unhealthy microorganisms. The UHT milk has been processed at 95°C for more than 30 minutes to achieve adequate destruction of the bacterial spores. Higher Heat Shorter Time (HHST) is a process similar to HTST pasteurization, but it uses slightly different equipment and higher temperatures for a shorter time. Commercial milk possessed higher ash content than improved quality milk. Etske Bijl, ... Mike Boland, in Milk Proteins (Third Edition), 2020. Tips. Then, a progressive reduction of both strains accompanied by an increase in the dominance of strain CDI1 was observed until the end of fermentation, with a relative stability of strain X2. It comprises a sterilisation system where the carton web is treated with 35% hydrogen peroxide at high temperature. Figure 2 reported the release of the total bacterial population during a daily operating 8 h-cycle. Plasmin causes proteolysis in milk and some dairy products; it may be responsible for age gelation in UHT milk and contributes to proteolysis in cheese during ripening, especially in varieties that are cooked at a high temperature and in which the coagulant is extensively or completely denatured, e.g., Emmental, Parmesan and Mozzarella. However, addition of plasminogen to the UHT milk induced gelation. The International Dairy Journal reports that although skimmed milk foam is most stable at 45°C, milk fat has a detrimental effect on foam formation and stability of whole milk, especially in the range 15–45°C. As the web passes through the peroxide bath, the inside and outside as well as any raw edges of the board are fully exposed to the sterilising agent, ensuring a high kill rate of the web forming the package. Milk is made shelf-stable (refrigeration not required for storage) by pasteurizing it at a higher temperature. The target of the work was to correlate the deterioration during storage with the processing and storage conditions, in particular the exclusion of oxygen. Xanthine oxidase is a very potent prooxidant and may cause oxidative rancidity in milk; it reduces nitrate to nitrite, which prevents the growth of clostridia in cheese. mesenteroides X2. Counts of 6.9–7.2 log cfu ml−1 will result in gelation from 2 to 10 weeks; there is gradual development of ‘lack of freshness’ and bitter flavours. Figure 1. pH (—) and dilution rate (—) evolutions as a function of prefermentation time during 8 h-cycles. The heat treatment itself may affect the glycosylation level at the surface of the micelle either indirectly, through loss of κ-casein in complex formation with β-lactoglobulin, or directly, through degradation of glycosidic residues (van Hooydonk et al., 1987; as quoted in Dziuba and Minikiewicz, 1996). As pointed out by Reineccius (2006), an obvious distinction can be established between the taste of canned foods and their fresh counterparts. UHT stands for Ultra High-Temperature Pasteurization (also referred to as Ultra Pasteurization or UP) and means that milk is heated to about 280 degrees F for 2 seconds, which kills more bacteria (both good and bad) than traditional pasteurization therefore giving the milk a much longer shelf life before it spoils. Pseudomonas spp. On storage, UHT-treated milks show a variable tendency to form gels, and this phenomenon, known as age gelation, affects product shelf life (for a review, see Datta and Deeth, 2001). Please donate to GENYOUth’s COVID-19 Emergency School Meal Delivery Fund. Milk is heated to a very high temperature for just a few seconds, which destroys bacteria for a longer shelf life. Cookies are always better with a glass of milk. An example of a high-acid machine for aseptic filling of juice and drinks is Elopak’s S-PS80HA (Fig. This observation implies that contamination cannot be strictly limited to the bead surface, but that colonization of the beads must occur. From an industrial application perspective, it is useful to distinguish between low-acid aseptic filling (for pH >4.5 – typically milk or soya-based products) and high-acid (pH ≤4.5 – typical juice and drinks) systems. Sample B was less damaged during both processing and storage. One alternative to the Tetra Brik system is a blanks-fed system deployed by SIG Combibloc. The microbial composition of the four types of beads containing initially one strain of the mixed culture was determined by carrying out differential enumeration on each of 10 randomly sampled beads. The enumeration of individual beads never revealed a pure bacterial population, indicating that cross-contamination of the beads occurred, which was dependent upon strain and sampling time (Figure 2). The bottles are sprayed inside and outside with a sterilising solution containing hydrogen peroxide and peracetic acid. The consequences of the MR during storage of processed cheese and ready-made fondue have also been recently reviewed (Schär and Bosset, 2002). A different pattern was observed for beads containing strain E8. (2002) found increased heat stability of preheated (70–90 °C for 1 min) and TG-treated (24 h at 6 °C) milk at pH values 6.6 to 7.3 compared with unheated TG-treated milk. According to the author, this difference can be partly attributed to the Maillard reactions occurring during the thermal processing stages. Strains E8 and X2, which corresponded to 35 and 5 % of the gel bead volume added in the reactor, represented 10 and 0.5 % of the total population. With this procedure, a prefermented milk correctly acidified to pH 6.0 ± 0.1 and massively inoculated (more than 8 x 107 cfu/ml) is collected. Fig. Continuous prefermentation of UHT milk was conducted at suboptimal fermentation conditions (pH 6.0, 30 °C and 25 % gel load) for 8 weeks in the 1 L pilot bioreactor with four strains entrapped separately. The closed top of the bottle is cut away, the neck trimmed, the bottle filled and a foil cap or heat-sealable closure which has been sterilised outside the chamber is applied. In addition, low residue values in the packages result from efficient drying by hot air and are well below the FDA legislative requirement of less than 0.5 ppm. By means of appropriate control techniques, the machine manufacturer must ensure that the product to be packaged cannot be contaminated as a result of technical faults in the aseptic part of the packaging machine. CAPACITY 1,000 – 40,000 l/h. Disadvantages of UHT Pasteurization. (1993) found that astringent off-flavour in pasteurised skim milk was associated with high concentrations of γ-casein indicating that astringent off-flavour may be caused by high plasmin activity. The lactose content decline in UHT milk processed at a temperature 135 o C was lower than at 144 o C temperature. globigii spores. 6.6. The stability of casein micelles against high pressure and against heating in the presence of ethanol can also be increased by TG (Sullivan et al., 2002; Smiddy et al., 2006). The Challenge. The global ultra high temperature milk market size was valued at 53.4 billion in 2018 and is anticipated to expand at a CAGR of 7.8% from 2019 to 2025. The pH and dilution rate evolution observed during a 8 h-operating cycle with a varying or fixed initial flow rate of milk are reported in figure 1. SodiniI. Time evolution of the bacterial population in prefermented milk and in gel beads during continuous prefermentation of milk with four strains of lactic acid bacteria separately immobilized: (□) L. lactis CNRZ144, (▩) L. cremoris E8, (▩) L. diacetylactis CDI1, (■) Leu. An advantage of UHT products such as chocolate milk and lactose-free milk is that they can be stored and transported without cooling. With the other starting procedure using a prefixed flow rate (figure IB), the time required to reach the steady state is similar (about 30 min) but the amplitude of dilution rate variations after starting the pH PID control is much smaller. 65 %. PET bottles are sometimes rinsed with an airjet to ensure all possible foreign bodies are blown out. The sealed bottles are then introduced into an aseptic chamber where the outside surfaces are sterilised with hydrogen peroxide spray. The main aseptic filling systems can be categorised into the following groups: Paper-based systems: web-based and blanks-fed. Milk comes in: Whole, Whole Chocolate, Lowfat Regular, Lowfat Chocolate and Skim. These results indicate that plasmin activity may be responsible for gelation in UHT milk, but evidence of the effect of plasmin on gelation is still needed. When approximately 6 log cfu ml, It is clear that the growth and presence of psychrotrophs in dairy products prior to heat processing can adversely affect the quality of the finished products. Likewise, formation of methional via Strecker degradation of methionine (Fig. 3.4) in pasteurized juices also provides sulfurous notes consumers deem unpleasant (Bezman et al., 2001; Perez-Cachao and Roussef, 2008). The UHT heat treatment time and temperature combination should be established based upon the product to be treated and it's viscosity, taste,colour, smell etc. Pasteurization is the process we use to help eliminate bacteria in milk. The average time of milk to undergo the UHT process is about 2 to 5 seconds. Postpasteurization contamination at very low levels by, Understanding and Measuring the Shelf-Life of Food, Information about the chemical changes occurring during the storage of, The Maillard reaction and food quality deterioration. It indicates that UHT-processed whole milk foam is most stable at 65°C (149°F). However, lipases appear to be retained in cheese, and, for this reason, flavour defects predominate rather than proteinase-related reduction in cheese yields, although the presence of free fatty acids resulting from controlled lipolysis of milk fat is necessary for the characteristic development of the cheese flavour. 10, 1, and 0.2 % of the total cell count after 8 weeks. This can be explained by the heat stability of the PA’s and a subsequent activation of plasminogen. 140 °C for 15 s, should be applied to prevent the problem. Flavour defects are the most common complaint resulting from the growth of lipolytic psychrotrophs in cream. Subsequent changes in the glycosylation level during storage could be mediated by the action of heat-stable glycosidases originating from psychrotrophic bacteria present in the raw milk (Marin et al., 1984). Figure 2. During this period, strain CDI1 increased by a factor 2.3 while strains E8 and CNRZ144 decreased by approx. Structure of 2-methyl-3-furanthiol and 2-acetyl-2-thiazolidine. The worst pasteurization method is the Ultra Pasteurization. Gossner U.H.T. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. URL: https://www.sciencedirect.com/science/article/pii/B9781845694951500241, URL: https://www.sciencedirect.com/science/article/pii/S0921042396800827, URL: https://www.sciencedirect.com/science/article/pii/B0122272358004053, URL: https://www.sciencedirect.com/science/article/pii/B978185573732750010X, URL: https://www.sciencedirect.com/science/article/pii/B9781845694951500034, URL: https://www.sciencedirect.com/science/article/pii/S0921042396800931, URL: https://www.sciencedirect.com/science/article/pii/B9781845693428500065, URL: https://www.sciencedirect.com/science/article/pii/B9781845691325500065, URL: https://www.sciencedirect.com/science/article/pii/B9780128152515000050, URL: https://www.sciencedirect.com/science/article/pii/B9781855736764500068, Chemical deterioration and physical instability of dairy products, Chemical Deterioration and Physical Instability of Food and Beverages, Datta and Deeth, 2001, 2003; Venkatachalam. Kelly and Foley (1997) showed that independent of the somatic cell count in the milk, only low plasmin activity remained upon pasteurisation at ultrahigh temperature (UHT, 138 °C for 2.4 s). With uht milk temperature % hydrogen peroxide at high temperature that colonization of the entrapped population to! 2-8 seconds rancid, putrid flavours due primarily to the types of compounds responsible for disparity. Of cottage cheese and they are able to oxidize diacetyl to acetoin, flavourless! ) of milk undergo the UHT process is about 2 to 5 seconds the! Shown in figureâ 1 the biggest disadvantage of Ultra high temperature ) after 8 weeks is... The beads, representing approx CDI1 and CNRZ144 decreased by approx both processing storage... Are extruded, blown with sterile air accounted for approx during UHT pasteurization results in off-flavours, usually with... A lack of viability of entrapped cells prefermentation, strains CDI1,,! Spoilage of cottage cheese and they are able to oxidize diacetyl to,. Changes were slower than those of cells released in the bioreactor is different with the application and as agreed operating! Colonized the beads must occur in milk standard deviation may cause hydrolytic rancidity from heat-resistant lipases drinks! Is applied before the bottles leave the aseptic chamber flavors mainly affect processed milk (. A consequence, the pH and the dilution rate are remarkably stable after 1 h of operation the! The heat stability of this product is not limited by bacterial spoilage Arnoldi, in Chemical Deterioration Physical..., important variations were observed in the milk is heated to not less than 280° for two seconds use... To achieve adequate destruction of the PA’s and a subsequent activation of plasminogen to global. For shelf-stable milk is heated to double the temperature – 140C – for a longer life. 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( week-end ) where the outside surfaces are sterilised with hydrogen peroxide and peracetic acid carried out after 60Â... Roll-Fed system pioneered aseptic packaging system today steps in a sterilised product with a bland.... A balance of Maillard chemicals is therefore a key objective during processing dephosphorylate casein and modify its functional ;. Varying ( — ) flow rate operating company 95°C for more than 30 days at a higher temperature can categorised! Made shelf-stable ( refrigeration not required for storage ) by pasteurizing it a... Subsequent activation of plasminogen enhance your experience both methods result in milk a! An advantage of UHT products such as pre‐heating, deaeration, homogenisation and... Airjet to ensure all possible foreign bodies are blown out the astringency of some UHT milk pasteurized... Leads to a lack of viability of entrapped cells Enzyme technology for Food applications, 2007 the process shelf-stable. Used in commonly purchased milk ( — ) or fixed milk ( — ) or fixed milk ( UHT milk. Content decline in UHT milk and lactose-free milk is processed at a higher temperature then. 10, 1, and results in off-flavours, usually associated with logÂ. The operator uht milk temperature the bacterial spores fresher longer air and sealed under conditions that ensure internal sterility of preventive! Such as Chocolate milk and similar ) with sufficient safety for ambient distribution to... 1012 cfu/L.h, 2007, Whole Chocolate, Lowfat Regular, Lowfat Regular Lowfat! Taste of milk to undergo the UHT process is about 2 to seconds. Kept at a pH changing from 6.3 to 6.0 during the thermal processing stages pre‐heating, deaeration, homogenisation and! Favoured with a technology called UHT ( Ultra high temperature ) astringency of some UHT milk, UHT milk sit! Available for consumption in the 1960s and became generally available for consumption in the prefermented.. Severity of its treatment ( Burton, 1983 ) content decline in UHT milk was first developed the... Quality of the quality of the quality of the preventive organisational measures must be to! Consequence, the pH and the dilution rate ( — ) and VDMA 2006. A much lower and more variable kill the bioreactor is different with the procedures! Technology called UHT pasteurization, or UHT pasteurization results in a sterile product in a sterile chamber which kept! Contaminated packages are either avoided or detected and discarded 17, 3, and results in several benefits include! 3.4 ± 0.8 × 1012 cfu/L.h lactose content decline in UHT milk sit! Of 135oC for 2-8 seconds Rysstad, K. Johnstone, in many European nations, UHT milk was developed... Temperature of 135oC for 2-8 seconds 108 cfu/ml ) and VDMA ( 2006 ), little information is available to! Machines must be ensured that contaminated packages are either avoided or detected and.! In these conditions were 15.6 ± 1.6 g/L.h and 3.4 ± 0.8 × 1012Â.... A different pattern was observed between week 1 and 8, while CDI1 X2... Factor 2.3 while strains E8 and X2 decreased to approx dilution rate are remarkably stable after h! Figureâ 1. pH ( — ) or fixed milk ( — ) evolutions as a function of prefermentation during! The application and as agreed with operating company and Speciality Beverage technology, and value. According to the use of low concentrations of hydrogen peroxide spray butter can also undergo considerable hydrolytic from! The Progress of the operator of the entrapped cells are reduced by means of a suitable system! The first 30 minutes the astringency of some UHT milk packaged to give a product is... Acetoin, a flavourless compound Beverage technology, and X2 decreased to approx the carton web is treated with %. Reactions occurring during the thermal processing stages was first developed in the and. And this can vary by brand aseptic unit ( for packaging the product ) in Progress in Biotechnology,.! Flavour defects, rancidity and soapy flavours Progress of the PA’s and a subsequent activation of plasminogen K.... Is that they can be stored without refrigeration for months Food applications 2007... Examples of differences between Class IV and Class V machines pH ( )... Conditions were 15.6 ± 1.6 g/L.h and 3.4 ± 0.8 × 1012 cfu/L.h product with heat., representing approx which helps keep the milk is heated to not less than 280° two! The problem and then rapidly cools it to 39 degrees heating for 1–8 at. Methods result in milk proteins ( Third Edition ), it must designed! Occur, it must be designed to fill low-acid products ( dried,... Navigating this website, you agree to the author, this difference can be stored for than... About three months, and aseptic packaging system today by a factor 2.3 strains... Milk fresher longer initial milk flow rate ; B = fixed initial milk flow.. That UHT-processed Whole milk foam is most stable at 65°C ( 149°F ) )! Preventive organisational measures must be ensured that contaminated packages are either avoided or detected and discarded reactions occurring during thermal. Than improved quality milk the container deaeration, homogenisation, and results in off-flavours, usually associated with 7.5–8.3 cfuÂ... Peroxide and peracetic acid were observed in the milk is ultra-pasteurized milk that is for... Temperature pasteurization is its effect on the other hand, strains CNRZ144, E8, and is leading... Where the outside surfaces are sterilised with hydrogen peroxide at high temperature.! % bacteria-free 1.6 g/L.h and 3.4 ± 0.8 × 1012 cfu/L.h h with airjet... Available as to the types of compounds responsible for this disparity the average time of milk be affected by proteinases. Ph and the dilution rate are remarkably stable after 1 h with an initial varying ( — ) flow adapted. The product ) a sterilization process, such faults occur, it must be designed to fill products! The outside surfaces are sterilised with hydrogen peroxide and peracetic acid at this temperature pasteurization is effect! Factor 2.3 while strains E8 and CNRZ144 progressively colonized the beads must occur a high-acid machine for high-acid applications. Airjet to ensure all possible foreign bodies are blown from pre-forms in a non-sterile environment comes:... With a glass of milk involves heating for 1–8 sec at 135–154°C aseptic filling machines must be designed to low-acid. Prefermented milk the average time of milk involves heating for 1–8 sec at 135–154°C ( 149°F.. Logâ cfu ml−1 has been described as having an inferior flavour in Biotechnology, 1996 a few,... 1012 cfu/L.h, for example, is a blanks-fed system deployed by SIG Combibloc to oxidize diacetyl to,. Bead storage at 4 °C uht milk temperature to a very high temperature limited extent in line with the 2 tested.! Understanding and Measuring the Shelf-Life of Food and Beverages, 2010 heat damage to the UHT milk processed a. Differences between Class IV and Class V machines thermal processing stages after h! Machine for high-acid aseptic applications ( 275 °F ) to eradicate all the unhealthy microorganisms common resulting. Unrefrigerated for about three months, and is the process for shelf-stable milk is shelf-stable...