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1、 General Understanding ambient yoghurt White paper second edition Challenges and opportunities General CONTENTS Introduction _ 3 Who is this white paper for?_ 3 What is ambient yoghurt and why is everyone excited about it?_ 3 What do producers need to know?_ 3 Yoghurt takes a new turn _ 4 Consumer p

2、erspective _ 4 Market perspective _ 4 Production perspective _ 5 Key manufacturing challenges _ 5 Regulatory perspective _ 5 Key process points in producing ambient yoghurt _6 Formulation of the yoghurt milk _ 6 Non-dairy additives _ 6 Deaeration of yoghurt milk _ 7 Homogenization of yoghurt milk _

3、7 Yoghurt milk pasteurization _8 Fermentation _8 Cooling of the yoghurt _8 Additives after fermentation(low-viscosity yoghurt)_ 9 Addition of aroma _ 9 Heat treatment of the yoghurt _ 9 Downstream design to secure hygiene _ 10 Storage conditions impact shelf life _ 10 Adding fruit and particles to a

4、mbient yoghurt _ 11 The particulate foods market is growing _ 11 The challenge of heat-treating particles _ 11 When should particles be added to the yoghurt?_ 12 Before heat treatment _ 12 Line design for particle integrity and homogenous distribution _ 14 Lactose-free ambient yoghurt _ 15 Tetra pak

5、 your dairy advisor _ 17 3 Introduction Who is this white paper for?This booklet is for dairy processing professionals who want to learn more about the opportunities in the expanding world of ambient yoghurt.Working with ambient yoghurt requires careful attention to materials and processes in order

6、to uphold high product quality.What is ambient yoghurt and why is everyone excited about it?Ambient yoghurt has boomed in popularity in recent years,and become a growth item in many markets.Ambient yoghurt is actually an abbreviation for the longer,more correct name“yoghurt-based product for ambient

7、 distribution”.These products do not need to be stored or distributed in cold conditions,and exist in a large range of textures and viscosities.What do producers need to know?Since ambient yoghurt requires additional heat treatment and additives to ensure a product that is stable over time at room t

8、emperature,this places great demands on proper dosing,mixing and heat treatment.In the following pages,we lay out some of these challenges in more detail,offering advice and technical guidance reflecting best practices in the dairy industry.Legal note:In many countries the definition of yoghurt requ

9、ires that it must contain live yoghurt bacteria.Since a heat treatment of ambient yoghurt inactivates these bacteria,the product is not legally allowed to be sold as yoghurt in these countries.4 Yoghurt takes a new turn Consumer perspective Ambient yoghurt or yoghurt-based products for ambient distr

10、ibution is a category that has grown in recent years and become immensely popular.It is either eaten with a spoon or else drunk directly from the package.The essential point about ambient yoghurt is that it does not have to be stored or distributed in cold conditions.This can make the drinking or ea

11、ting process more convenient for consumers,and it also means that they can easily travel and take the product with them for consumption later.The consumer enthusiasm for ambient yoghurt is partly built on its convenience,and partly on its nutritional profile it contains appropriate levels of natural

12、 proteins,fat,and minerals,with relatively low sugar levels compared to soft drink beverages.Market perspective Ambient yoghurt is experiencing a growth spurt in popularity.While global production volumes of most yoghurt types grew at a compound annual growth rate(CAGR)of 4%during the period 2013-20

13、16,ambient yoghurt production grew at a CAGR of 19%in the same period.This niche product,currently rising from small volumes,is gaining attention as a convenient and healthy consumer drink.From a manufacturers point of view,ambient yoghurt presents many good business opportunities,when compared with

14、 chilled products.Opportunity How Enter new geographical markets Longer shelf life allows distribution to larger geographical areas.Facilitates transportation Cold distribution is costly and is not available in all markets.Encourage new consumption patterns The ambient version can be consumed on the

15、 go,as a snack and can be put in a bag for sudden hunger needs.Reach new consumer groups For instance,by appealing to consumers who dont eat breakfast or dont like to eat cold products.Increase production efficiency through larger production batches Chilled products have limited shelf life and are t

16、herefore produced in relatively small batches to ensure they reach the retailer/consumer in fresh condition;this is not a limitation for ambient yoghurt.5 Production perspective Today,a large range of ambient yoghurt products are produced commercially,with largely unique formulations or production p

17、rocess.Generally,ambient yoghurt products can be divided into low-viscosity and high-viscosity products,which are produced differently and therefore present different processing challenges.But regardless of viscosity,producing ambient yoghurt always differs from traditional yoghurt in one principal

18、way:The yoghurt is heat-treated after fermentation to inactivate bacteria.This enables the yoghurt to be distributed and stored at ambient temperatures.They enjoy a long shelf life of 4-12 months,depending on the way they are formulated and processed.Shelf life definitions are subjective,but low-vis

19、cosity products generally have longer shelf lives than high-viscosity products.The shelf life is typically limited by physical instability(whey separation)and changes in flavour and colour.Key manufacturing challenges The additional heating required for ambient yoghurt affects a natural,classic yogh

20、urt in a number of ways:The viscosity will be reduced Whey will separate out from the yoghurt Aroma,colour and mouthfeel may change,for example,an undesirable sandy or powdery mouthfeel.In order to counter these changes,special ingredients are added to the yoghurt.But to achieve consistent product q

21、uality that appeals to a given group of consumers,careful attention must be paid to choosing and dosing these additives,as well as the mechanical treatment and heat treatment of the yoghurt.Getting all of this to work right in a production environment is a question of engineering optimization and fo

22、od chemistry know-how.Regulatory perspective As already mentioned,many countries define yoghurt as containing live yoghurt bacteria.Since a heat treatment of the yoghurt kills these bacteria,the product is not legally allowed to be called“yoghurt”in these countries.Alternative labels may be used,suc

23、h as:Yoghurt-based product Post-fermentation heat-treated yoghurt Yoghurt-based beverage Fermented dairy dessert 6 Key process points in producing ambient yoghurt Point-by-point,there are many considerations when designing processing lines to fit particular product recipes.This section is not an eng

24、ineering discussion filled with flow diagrams,but it will give you some idea of the challenges in perfecting ambient yoghurt.Formulation of the yoghurt milk The yoghurt can be made from both fresh and recombined milk,but as with any yoghurt,the milk should preferably have a low bacterial count and c

25、ontain absolutely no antibiotics.The milk is commonly standardized and pasteurized before it is further formulated by the addition of ingredients.Non-dairy additives Combinations of additives are added to the product in order to overcome the negative effects of the later heat treatment.These additiv

26、e combinations will determine the products mouthfeel and viscosity,as well as prevent sedimentation.For high-viscosity ambient yoghurt,the additives used are typically combinations of starch,pectin,and gelatine or some type of gum component.High-viscosity ambient yoghurt has a texture and appearance

27、 similar to chilled stirred yoghurt,but is packaged and sold as a spoonable or drinkable product depending on the market.Formulated additive mixtures are commercially available.The additives are added before fermentation to the milk,before the yoghurt milk pasteurization,and their purpose is mainly

28、to increase viscosity and create good mouthfeel and stability.Though some protection from the heat is provided by the increased viscosity,the additives for high-viscosity ambient yoghurt typically do not contain any protein-protecting components,making the product sensitive to the heat load during f

29、inal heat treatment.Depending on the recipe used,the product can also be sensitive to any mechanical shear applied after fermentation.With these challenges in mind,a final heat treatment system with plate heat exchangers is often recommended.Even with a well designed formulation and process,about ha

30、lf of the viscosity is generally lost in this final processing step.7 For low-viscosity ambient yoghurt,the additive used is often a pectin,pure or mixed with another component.Packaged and sold as a drinkable product,the characteristics can vary but the product still has a clearly pourable consiste

31、ncy.For these applications,additives are commonly added after fermentation.The pectin interacts with the protein in the fermented product,securing stability over shelf life by avoiding sedimentation or separation.It also protects it during the final heat treatment,making the yoghurt less sensitive t

32、o heat load than a high-viscosity ambient yoghurt.To achieve optimum protein protection,the product is homogenized in the final heat treatment.While a plate-based final heat treatment system could very well be used here,a system based on tubular heat exchangers is often preferred,as it increases pro

33、duction flexibility.Deaeration of yoghurt milk It is recommended to deaerate the yoghurt milk in order to reduce the air content.This is especially important when recombined milk is used as a base.Deaeration will minimize the risk of fouling during heat treatment,as well as minimize the fermentation

34、 time.But perhaps most importantly,it can improve product stability.Homogenization of yoghurt milk The milk is homogenized at a pressure around 200 bar at about 60-70C,depending on formulation.Most commonly a two-stage homogenizer is used for optimal running condition and flexibility.Homogenization

35、will prevent creaming and improve the stability and consistency of the yoghurt,but can also improve functionality of additives.8 Yoghurt milk pasteurization The yoghurt milk is heat-treated in order to:Kill any pathogenic(disease-causing)microorganisms in the milk Create the best conditions for ferm

36、entation.The heat-treatment kills off all vegetative microorganisms that might otherwise compete with the starter culture during fermentation.The heat-treatment also causes formation of nutrients that improve the growth of the starter culture Create the best conditions for the formation of a strong

37、yoghurt network during fermentation,by denaturing the proteins.A strong network maximizes the chances of getting a viscous and stable final product If the product recipe contains additives,the heat-treatment might also activate their functionality.Denaturation of the whey proteins dimensions the hea

38、t-treatment step.Typically,yoghurt milk is heated to 90-95C and held at this temperature for 5-10 minutes for full whey protein denaturation,but other equivalent time-temperature combinations can also be applied.After the yoghurt milk pasteurization,the yoghurt milk is cooled to fermentation tempera

39、ture(43C).Fermentation The yoghurt milk is pumped into a fermentation tank where the required amount of yoghurt culture is added in-line to the milk or directly in the tank manhole.Typically,fermentation takes place for 4-10 hours,depending on the bacteria strains used.When the desired pH has been r

40、eached(pH 4.5),the product should be cooled.Cooling of the yoghurt The yoghurt is now cooled in a plate heat exchanger to around 20C,in order to stop fermentation,and then pumped to an intermediate buffer tank.A fermentation tank is normally emptied within 30-60 minutes in order to maintain uniform

41、quality.Some starter cultures have very low post-acidification,i.e.change very little after the desired pH has been reached,and can therefore be stored at fermentation temperature for several hours.For products using these starter cultures,it is possible to eliminate the cooling and intermediate buf

42、fer steps.9 Additives after fermentation(low-viscosity yoghurt)The addition of an additive(pectin see above)to a low-viscosity ambient yoghurt can be done in the fermentation tanks,or in the buffer tanks after cooling.The addition can be done in two ways:The additive in powder form,often combined wi

43、th sugar,in mixed directly into the fermented product using a high-shear mixer A concentrated solution with additive and sugar dissolved in water is created and later added to the fermentation/buffer tank or dosed continuously into the yoghurt stream prior to final yoghurt heat treatment.Addition of

44、 aroma Aroma can be added to low-viscosity yoghurt by mixing an aroma concentrate into the buffer tank or inline to the heat treatment.Fruit juice can also be added,but it will also reduce the products milk solids.An alternative way of adding the aroma is to dose it aseptically and continuously prio

45、r to the filling machine,using specialized dosing equipment.Adding aromas or colours to high-viscosity ambient yoghurt can be challenging.Any added ingredient needs to be aseptic to avoid contaminating the product.The fermented product is often quite viscous before heat treatment and the aromas and

46、colours are often viscous as well.Static or dynamic inline mixers must be used in order to achieve a homogenous product.An alternative strategy can be to add the aroma/colour in the formulation step before yoghurt milk pasteurization,but this requires the ingredients to be heat-stable.Heat treatment

47、 of the yoghurt The yoghurt must now be heat-treated to allow ambient distribution.The temperature/time combination used is dependent on pH,composition,stabilizer type,etc.The heat treatment is designed to inactivate the yoghurt culture not to eliminate bacterial spores from the yoghurt.They will re

48、main,but provided that the pH of the product is low enough,they will remain inactive.For an undiluted,high-viscosity yoghurt with a pH below 4.5,treatment at 75C for 20 seconds is often used.The yoghurt is generally sensitive to heat,so using higher temperatures risks giving the final product a powd

49、ery or sandy mouthfeel,as well as reduced viscosity.Homogenization is normally not included in the final heat treatment of high-viscosity yoghurt,as homogenization would break down the starch additive and reduce the viscosity.10 Low-viscosity yoghurts are generally heat treated at higher temperature

50、s (90-110C),as they are often mixed with water or juice before the heat treatment.Though the additives used in this type of product make it less sensitive to heat,further elevated temperature/time can still damage product quality.For low-viscosity yoghurt,a homogenization(150-200 bar)is included pri

51、or to the yoghurt heat treatment to reduce final viscosity and to improve the stabilizing effect of the pectin on the proteins.Using lower-pressure homogenization may result in early sedimentation during storage.It is important that the pectin is fully dissolved before it is homogenized together wit

52、h the yoghurt.If,for example,dry pectin has been added,the homogenization temperature should be increased to around 65C.Downstream design to secure hygiene The ambient yoghurt is commercially sterile containing no microorganisms capable of growing in the product after the final heat treatment.The lo

53、w pH is a significant hurdle for microbiological growth,but the design should nevertheless consider the risk of contamination.High-hygienic or aseptic conditions in design and operation should be applied.For high-viscosity yoghurt,consideration must also be made to minimize shear on the product to p

54、reserve the viscosity.A cone-shaped buffer tank with positive pump at outlet to feed the filler should be used to minimize product losses.Storage conditions impact shelf life The shelf life of ambient yoghurt is mainly determined by physical changes like sedimentation,whey separation or changes in t

55、aste or colour.These are natural processes that occur over time,but the rate will increase if the product is distributed and stored at elevated temperatures.11 Adding fruit and particles to ambient yoghurt The particulate foods market is growing Two major trends are driving the increased popularity

56、of adding particles such as grains,nuts or seeds to food products:Consumer demand for convenience foods with homemade quality Beverages giving the consumers new experiences by adding particles.Both these trends fit into the consumption patterns of yoghurt.Products with particles are perceived as bet

57、ter,overall.Taste and texture of particles are appreciated,and yoghurt with particles is perceived as healthier and more natural.Adding particles generally gives a perception of higher quality,but it does increase the complexity of technology and line design.What is the optimal heat treatment to ach

58、ieve food safety,while maintaining the quality of the entire product?How should the transfer and pumping be designed to secure minimal mechanical treatment and avoid rapid pressure changes?And how should the particles be added to the yoghurt for accurate dosing and homogenous distribution?The challe

59、nge of heat-treating particles Particles vary in size,shape and composition,which in turn affect their physical properties density,thermal conductivity and specific heat capacity.Some particles are easily heated.Others withstand heat longer and might require higher temperature and longer exposure ti

60、mes.Particle size also affects heating conditions.The bigger the particle,the longer it will take to transfer heat from the particles surface to its core(the coldest spot).But the size of the particle can also influence the heat transfer from the heating media to the liquid phase and from the liquid

61、 phase to the surface of the particle.Larger particles can for example create greater turbulence in the liquid phase and thereby improve heat transfer.To achieve good product quality,particle integrity needs to be protected.Optimizing heating in the process design is thus the basis for both maintain

62、ing product quality and ensuring food safety.This demands knowledge of heat transfer in particulate foods.12 Based on several decades of experience with heat transfer models at Tetra Pak,we have developed well-established calculation tools to predict the heating and cooling of particulate foods.Our

63、PartCalc tool allow us to predict with great accuracy the required heating area of the heat exchangers,to minimize overheating of the liquid while securing the highest level of food safety.For more information see the Tetra Pak white paper“The inside story on heat treatment of particulate foods”.Whe

64、n should particles be added to the yoghurt?After heat treatment The recommended method for adding fruit or other food particles,such as grains,nuts or seeds,is to add them after final heat treatment of the yoghurt.In this case the fruit itself must be high heat-treated(or equivalent)before addition

65、to avoid contamination of the yoghurt.Heat-treating the yoghurt separately from the fruit particles has several advantages.The separate heat treatments can be optimized for each products specific properties,both from the perspective of heat load and mechanical treatment,resulting in:Improved quality

66、 in terms of particle integrity,yoghurt viscosity,etc.Increased production flexibility Possibly lower running cost.Adding fruit after final heat treatment is preferred from the standpoint of processing flexibility and product quality,but the initial equipment cost is likely higher than for other sol

67、utions.Before heat treatment Fruit or other food particles can also be added before final yoghurt heat treatment.This has several advantages:Possibly lower investment cost Simple production time schedule(PTS)for the filling line Minimized line equipment downstream after final yoghurt heat treatment,

68、reducing the risk of recontamination.13 But the liquid base of a product(in this case the yoghurt base)should not be over-processed if high quality is to be achieved.And as we pointed out in the previous section,particles often require longer heating time and/or higher temperature than yoghurt,which

69、 is sensitive to heat.Thus one critical drawback to this process is that texture and stability of the yoghurt can be negatively impacted when particles and yoghurt are heat-treated together.This method is therefore only recommended for low-viscosity yoghurts,where additives make the yoghurt less sen

70、sitive to heat,and with particles that can be rapidly heated,in order to minimize overheating the yoghurt base.Figure 1.Example of process line concept for high-viscosity ambient yoghurt with fruit addition before or after the final yoghurt heat treatment 14 Line design for particle integrity and ho

71、mogenous distribution Addition of particles to ambient yoghurt also requires control of the line design to secure particle integrity and homogenous distribution.Examples of parameters to consider are the design of:Heat exchangers such as the inlets of tube packages,tube sizes Tanks Agitators Pumps F

72、or more information see the Tetra Pak white paper“Minimizing damage when processing particles,fibres and pulp”.15 Lactose-free ambient yoghurt The market for lactose-free and lactose-reduced dairy products is experiencing significant growth.Demand for lactose-free products in general is driven by an

73、 increase in the supply of milk products to areas where lactose intolerance is prevalent in the population.This is a result of globalization factors such as relocation and new population/demographic distribution in countries where lactose intolerance was not significant before.Demand is also related

74、 to many consumers self-diagnosing their lactose intolerance or simply viewing lactose-free products as part of a healthy lifestyle.The value-added dairy segment including desserts,yoghurt,and flav-oured milk is also increasing,and lactose-free products are one of the main contributors to market gro

75、wth.To produce lactose-free ambient yoghurt,the lactose in the milk must be hydrolysed by adding lactase.The lactase will split the lactose molecule into glucose and galactose(see figure below)which increases the sweetness of the milk.Thus utilizing lactose reduction technology can create an equally

76、 sweet final product while adding less sugar.Products with reduced lactose and reduced carbohydrate content are well-suited to the consumer trend of reducing sugar intake.Like all other enzymatic processes,the speed of hydrolysation is dependent on temperature in the process,dosage and strength of t

77、he lactase,product pH and lactose concentration.The optimum working temperature for lactase can vary between 3565C and the optimum pH for lactase hydrolysation can be in the range of 3.07.4,depending on the source of the lactase.Therefore,adding the lactase to the warm yoghurt milk before fermentati

78、on is started will ensure the most efficient hydrolysation.For fermented products,producers should exercise caution when using an enzyme with a lower pH limit,5.5 for example.If the hydrolysis process is not completed before the fermentation reaches pH 5.5,the lactase will be inhibited to such a deg

79、ree that the lactose content will be too high in the final product.16 For ambient yoghurt,lactase can also be added just before filling,and the actual hydrolysis process will take place in the packaged product during the first days of storage.The enzyme used should then be of a type that is still ac

80、tive at the pH of the final product(4.5)and is dosed continuously and aseptically to the product.This type of solution gives a high degree of production flexibility,as the same fermented base can be used for both reduced-lactose and normal product variants.17 Tetra pak your dairy advisor Tetra Pak h

81、as solid experience within ambient yoghurt,and has a worldwide installed base of process lines for ambient drinking yoghurt products.In fact,Tetra Pak supported the successful launch of ambient yoghurt in China.Our customer and solution experience is based on deep understanding and extensive special

82、ist knowledge.We are able to offer customized solutions targeting your requirements,and can help you design or upgrade lines based on your specific processing needs,with the lowest total cost of ownership.Thanks to our well established industrial and technology profile,we can support your yoghurt pr

83、oduction,regardless of the changing tastes and demands of your marketplace.The right plant design and processing design can offer you unlimited new business opportunities through new products,improved quality,and lower costs.We offer:Extensive knowledge of processing technologies,as well as how best

84、 to implement them Product Development Centres and dedicated technology specialists Valuable knowledge and experience through partnerships with suppliers of technology,ingredients and supplies Processing modules and line concepts for all known technologies End-to-end offerings,handling everything fr

85、om incoming raw ingredients to pallets of finished products on your loading dock.As an innovator,Tetra Pak actively explores and develops the challenges of the food and beverage industry.We collaborate with customers,universities,and other business partners to develop new applications and find the b

86、est solutions for producing new products with flexibility.We develop customized solutions for your needs and maintain a leading position in developing new line concepts.At our Product Development Centres located in Europe,Asia,North America and South America,customers can carry out product trials to

87、gether with Tetra Pak specialists with unique comprehensive expertise in food processing and packaging.The centres provide highly flexible pilot plant facilities for processing and packaging trials,which ensures fast and reliable industrial scale-up.Customers can experiment with recipes and use the

88、latest processing equipment.For further information on dairy processing and packaging in general,try: Youll also find more specific information here:https:/ 18 Tetra Pak International S.A,Tetra Pak Processing system AB,revision 1 2022-03-07 Tetra Pak and Protects Whats Good are trademarks belonging to the Tetra Pak G