The bioprocess of yogurt

The bio do by of yoghourtAbstr spielThis report discusses the bioprocess of manufacturing yoghourt on an industrial outstrip. On a industrial scale the procedure for yoghourt fruit fol petty(a)s preparation and criterionization of take out, pasteurization, homogenization, Cooling to incubation temperature for inoculation with grump finish, ferment, post- fermenting word i.e. adding additive such as flavouring, fruit attachment, refrigeration and packaging. In examining all(prenominal) ill-treat and identifying limitation, advancements in the superior oecumenic procedure amaze been suggested. Some improvements complicate ensuring correct standardization of draw i.e. yoghurt standard contents be met, changes in technique apply to alter adipose tissue content, effective conflag compute treatments to kill off unwanted beings, verification of fermenting process to open and catechumen culture apply in inoculation provides high yields, practise is limited to avoid contamination of and damage to the final product.Introduction yoghourt is wholeness of the most popular dairy products consumed worldwide and is made principally on the bacterial fermenting of draw. The word is from the Turkish Yogen, meaning thick. Originating in the slopes of Mount Elbrus the discovery of yoghurt was by complete chance when a Turkish nomads pitcher of take out was contaminated by some organism that thrived in warm draw. Since thus yoghurt has been produced and consumed worldwide for at to the lowest degree 5 400 years and continues to be one of the most nutritious foods proving unique nutritional value to the consumer.Yoghurt is produced when a lactic sharp bacterial ice culture is use to ferment the sugar lactose found in draw to Lactic red-hotulent which then acts on the protein to give yogurt its diagnostic texture and form. Dairy yoghurt is produced using a mingleed culture of Lactobacillus bulgaricus and strep thermophilus bacteria.Alt hough the consistency, flavour and aroma whitethorn vary from one region to another, the basic genes and manufacturing process are fundamentally consistent.The general manufacturing procedure includesAd stilling draw composition and addition of other ingredient to meet the adoptd Code of Federal Regulations (CFR) in terms of modify and non-fat content.Pasteurization of milk to kill unwanted bacteria homogenization of milk to condition uniform compositionCooling of milk to optimal starter culture incubation temperatureFermentation of milk by addition of starter cultureAddition of flavours and fruitStorage and packagingThe implantation of this general manufacturing procedure is seen in the mathematical product of Yoplait yogurt (as seen in the flowchart below). conceptualization of MilkIn the occupation of yoghurt a variety of milk locoweednister be employed whole fat, semi-skimmed milk or low fat milk, the type of milk used dep ratiocinations upon the type of yoghurt one i ntends to produce. However, one of the main importance when considering the type used is the absence of either material (disinfectant) or organisms that leave alone hinder or prevent the issue of the starter organism, for example, bacterio bacteriophages which are a group of virus that ordure attempt the starter organism causing extremely long periods of incubation (Moralee, 2002).When the milk arrives at the plant, its composition is altered before all further bear upon faecal matter be completed. This standardization process usually involves increasing the arrive firms content and decreasing the fat content. The fat content is reduced by a process termed centrifugation. Centrifugation is a separation process comm exactly used in the industrial treatment of milk. In this process the centrifugal draw and quarter is utilized to sepa straddle insoluble from the liquids thitherby impressioning in the fat globules separating from the eternal rest of the milk suspension. The milk should be kept at temperature of 40oC before go into the centrifuge (Costa Goomes, 2008). The lower the fat content the higher the lactose take aims (Carpers, 2005) wherefore lowering the fat content will be beneficial when the milk later down the stairsgoes fermentation. Several methods can be used to raise the steadfast contents in milk evaporation, addition of skim milk powder, addition of milk concentrates etc. In industrial yoghurt manufacturing, the solids content of yogurt is often adjusted above the 8.25% minimum ( nourishment and drug administration, 1999). Commonly the standard solids content is affix to 16% with 1-5% being fat and 11-14% being solid non-fat (SNF). Increasing the dry matter contents (solid non milk fat) not only improves the nutritional value of the yoghurt, but in addition provides a thicker, firmer and fuller personify to the finshed yoghurt (Watson, 2004).ImprovementsEvaporation of milk prior to the fermentation process for turn milk (hi gher non-fat solid content) is utilized in influence to give a better trunk and texture to the yoghurt. Due to the ever spiralling energy costs, the increase in cost of concentrating milk is decent prohibitive ( Moralee, 2002). Consequently, larger manufacturing plants waste begun replace the evaporation method with a new technique know as fortification. Fortification is the addition of dried milk solids to the fundament of milk prior to inoculation (Moralee, 2002). Several commercial yoghurt manufacturing plants are fortifying the base milk with a cocktail of milk and non milk solids (Smith, 2002). The addition of stabilizers whitethorn also be employed to improve the body of the yogurts as they increase the resoluteness and viscosity, preventing separation of the whey liquid remaining aft(prenominal) milk has been curdled, from the yoghurt, a problem know as syneresis (Watson dairy consulting, 2007). This is achieved through their capability to form change structures in w ater and as a essence leaving behind less free water for syneresis. Stabilizers are to a greater extent chief(prenominal) in yoghurt produced commercially as yoghurt mix has to be pumped, stirred, fruited and filled and will often break down to a runny liquid without the addition of stabilisers (Watson, 2004). The amount of beneficial stabilizers to be added to the yoghurt concoction is required to be determined evidently through hole sampling experimentation by each manufacturer as as well a good deal stabiliser and the yoghurt can take on a rubbery texture, far similarly much stabiliser and the yoghurt can become a hard solid mass (Moralee, 2002). Some stabilizers used in yoghurt manufacturing include gelatins, gums (locust bean, guar), pectins, and starch.PasteurizationGenerally the fresh milk seeed from healthy animals is either beneficial or harmless, however, changes when improperly handled, or declension of the animals health can create conditions in which the bacter ia are competent to multiply. The large presence of unknown organisms in the raw milk would remove the fermentation too unreliable and unpredictable for commercial operations (Csutak, 2005). Pasteurization is the process by which hotness treatment to each particle of milk at relatively high temperature for a specified period of metre is adequate of killing off harmful bacteria for example pathogens, and improve the storehouse attribute of milk by inactivating certain undesirable enzymes and spoilation bacteria (Watson 2007). Typical temperatures for milk pasteurization are 85-95oC for 20-30minutes (Smith 2002). This technique of hot up treatment is also successful in achieving a more still gel as it denatures the whey (serum) proteins. Furthermore, high heat treatment can also ensure little competition from spoilage organisms providing a much better environment for magnanimous of starter organisms later in the process. It is important that the pasteurization of the milk kick the buckets before addition of starter cultures as this ensures they act as prebiotics remain active in yoghurt after fermentation (moralee, 2002).ImprovementsWhilst pasteurization of the milk is effective in destroying microorganisms, improper handling after pasteurization can recontaminate the milk (Brock, 2005). Several safe handling practices can be employed such as sterilised equipment should be used, desirable stainless steel utensils as these are more easy to nifty and durable, pure water streams should be utilize when cleansing to prevent any contamination, rapid cooling to somewhat 5oC or less and storage in closed vessels before and after pasteurization to ensure unaltered quality and flavour of milk (Brock, 2005).Pasteurization can be a consecutive or batch process, however, commercially it is better in continuous move vessels as this continuous agitation ensures every particle of milk including the foam receives the minimum heat treatment. The temperature withi n each vessel should be monitored with an hi-fi metal or glass thermometer (Smith P, 1981).Apart from utilising pasteurization, Ultra-high temperature (UHT) is another type of heat treatment that is currently being employed. In this type of processing organisms are destroyed destroy more effectively by heating the mixing for a shorter period of period, approximately 1-2 seconds, at an extremely high temperature exceptional(a) 135oC (Dairy Science and Technology, 2007). UHT treatment essentially sterilizes the milk and allows it to be stored at live temperature for up to 8 weeks with out change in flavour (Brock, 2005).HomogenizationIn the commercial ware of yoghurt milk is always close homogenize prior to fermentation in order to give a uniform product. Homogenization of milk aids in the prevention of unction that is, the fat from rising to the surface during the fermentation process. Using a homogenizer or viscolizer fat globules are broken down into much smaller and more e venly dispersed particles and subsequently producing a much smoother and creamier end product (Watson, 2007). When milk enters a homogenizer it is force through small orifices at extremely high pressures breaking down globules as a result of the high shearing forces and dispersing the fat evenly throughout the milk which prohibits the fat from rising to the top of the container (Steane, 2008). Milk mixtures are typically homogenized under pressures of 2000-2500 psi (Moralee, 2002). Additionally this process also prevents wheying off during the incubation and storage stage thus enhancing the stability and consistency of the yoghurt. Once the homogenized mixture has been cooled to the optimum growth temperature, the starter culture is added. It is important for the mixture to be cooled to a typical temperature of approximately 45oC for inoculation as temperatures higher than this may kill off culture (Watson, 2007).Following the cooling of milk to a temperature of 40-45oC, the milk i s immunised with a fermentation culture. The main starter cultures for yoghurt toil are Lactobacillus bulgaricus and Streptococcus thermophilus. The function of the starter cultures is to ferment the lactose, sugars found in milk, to produce lactic social disease.C12H22O11 + H2O ? 4 C3H6O3 Lactose Lactic AcidThe increase in lactic acid toil corresponds to a fall in pH levels and causes the milk to clot, or form the soft gel curd that is characteristic of yogurt. The fermentation of lactose also produces flavour compounds, acetaldehyde, that are characteristic of yogurt. The lactic acid levels can be measured by simply performing a titration with sodium hydroxide. The current minimum standards for yoghurt manufacturing require a value of at least 0.9% acidity and a pH of about 4.4 (Food and drug administration, 1999). The fermented milk is typically incubated in large stiff vats in a temperature controlled environment, temperature is monitored carefully to maintain at a tempera ture optimum for starter culture growth. Inoculation typically occurs at a rate of 0.5-5% (Watson, 2007). When the desired acidity, that is pH level of about 4.4 is reached, rapid cooling to approximately 7 oC is effected in order to stop the fermentation process. It is merry to note that too long or too short a fermentation process will produce a product that is lacking(p) in either its flavour or texture. Too long fermentation will give other organisms the change to become established, with the associated risks of off flavours and smells (Morale, 2002).In the commercial production of yoghurt, emphasis is not only on the fermentation ability but also on characteristics imparted by the lactic acid cultures. For satisfactory performance the starter culture must be capable of rapid acid production, flavouring of yoghurt, production o full body and texture yoghurt. The determination of whether the starter culture activity is satisfactory or not is determined by direct microscopic cou nts of culture slides stain with methylene blue (Smith, 2002). In doing so there is also the eudaimonia of observing the physiological state of the cultured cells. The lactic starter culture used for yoghurt production is thermophillic has an optimum temperature of 42oC. The two cultures (Lactobacillus and streptococcus thermophillus) can be grown independently however, there is a higher rate of acid production when used in together (mixed strain), that is that make use of each others metabolites in order to effect the acid production efficiency. Streptococcus thermophilus grows at a faster rate producing carbon dioxide and lactic acid. The formate on with the carbon dioxide stimulates the growth of Lactobacillus (Smith, 2002). During fermentation the yoghurt mixture coagulates when the pH level drops. The streptococci are responsible for the initial pH drop of the yogurt mix to approximately 5.0. The lactobacilli are responsible for a further falling off to pH 4.5 (Steane, 2008 ). Inoculation of lactic starter cultures with yoghurt milk produces lactic acid, acetaldehyde and acetic acid.Improvements-As mentioned above when selecting the type of milk used in manufacture of yoghurt it is important for the milk to possess a low bacteria count, be free from sanitizing chemicals, rancid milk and have no contamination by bacteriophages. Serious economic losses in the yoghurt industry have been attributed to phage attack (Smith, 2004). Accompanying the moderate in texture and flavour, bacteriophage attacks decreases the rate of acid production. Large scale manufacturers typically have laboratory facilities to check incoming milk to transcend the possibilities of other starter inhibiting substances (Moralee, 2002), however, the presence of bacteriophages is always a risk. Large manufacturers phage are usually found in the drains and floor gullies of a dairy producing any cultured product, poor hygiene and a lack of general housekeeping increase the risk (Dairy S cience Technology, 2007). Thus in order to reduce the possibility of bacteriophage present strict sanitation procedures would ensure prevention of phage attack (Smith, 2004). This include hand-washing between each handling, unproductive tanks, floors and bench surface. sAlso, since the starter culture is one of the most searing ingredients in yoghurt manufacture synchronisation of rate of acid production and plant production schedules is extremely vital. For example, if frozen cultures are used then a longer incubation period of approximately 5 hours at 43oC is required for acid production (Smith 2002). Similarly as noted above, tutelage of temperature is extremely important for starter culture. This is because if the temperature of incubation is too low, culture grows at such a slow rate that it is unable to adequately sour milk and to achieve a good texture vice versa if the temperature is too high the culture is killed.Traditionally, when the lactic acid starter culture is gr own in a suitable medium, small quantities will be extracted to inoculate each new batch of yoghurt. This is commonly referred to as using wad starter. However, due to the high risk of bacteriophage infections and the delay in time when each new batch is prepared, employment of bulk starter is becoming increasingly uncommon amongst commercial producers (Smith, 2002). A new technique referred to as DVI (Direct Vat Inoculation) is fast becoming the most preferred choice which involves vaccinating the yoghurt mix directly with a very large quash of freeze dried starter organisms (Watson,2007). Even though there may be a longer incubation time, relative immunity to phage attack makes this a more safe option for manufacturing plants to ensure production of yoghurt is efficient every time.The design of the container in which the fermentation process is carried out in can also improve the process. Commercially there has been a shift in design of cone bottom processers to make haste th e draining of relatively viscous fluids after incubation (Carpers, 2005). Critical step in the fermentation process is the maintenance of the optimum temperature for growth of starter cultures hence well insulted incubation vats should be utilized.Addition of fruit and promotionAt this stage fruits and addition desired flavours may be added at or prior to filling preformed pots. Common additives include, fruit flavours, colouring agents, sweetener agents. Depending on the type of yoghurt, the above fermentation process may occur before this addition of fruit or after. For example, in set appearance yoghurt fruit is added to the bottom of the cup and inoculated yoghurt is poured over the top, the fermentation takes place within the cup. For stirred yoghurt, the fruit is blended with the cooled ferment yoghurt and yoghurt texture can be made smoother by pumping it through a cone before packaging (Moralee, 2002). The yoghurt is keep until it is required for package and transportatio n.Conclusion-In undertaking an engineering analysis of the bioprocess of yoghurt and exploring each step carefully it can be seen that although yoghurt follows a general manufacturing procedure. The bioprocess of yoghurt production involves preparation of milk, followed by pasteurisation and homogenisation of the milk, cooling down period, then inoculation with a lactic acid bacterial starter culture to ferment the milk. Measurement of acid production measures the success in fermenting milk. Additions of fruit and other additives are added just prior to storage and packaging. The exploitation of the fact that milk contains the sugar lactose, and when undergoing fermentation with a starter culture produces lactic acid, allows observation of how yoghurt is produced. The production of yoghurt on an industrial scale requires great improvement in the handling of the mixture to ensure no contamination, choice of raw materials will greatly affect the final product, employing a successful m ethod to obtain a starter culture that is free from unwanted materials and operation in fermentation vats that give efficient outcomes.ReferencesCarpers S, 2005 , http//www.natmedtalk.com/nutrition/4933-lactose-higher-fat-content-lower-lactose.html, viewed 14/04/10Driessen, F. M., Ubbels, J., and Stadhouders, J., endless manufacture of yogurt. I. Optimal conditions and kinetics of the prefermentation process, Biotech. Bioeng., 19, 821, 1977Ed Excel Foundation, http//www.biotopics.co.uk/edexcel/biotechnol/yog.html, viewed on the 24/04/10).J Scott Smith Yiy Hui, 2002, Food processing principles and applications, pg 297-319John Watson, 2007, http//www.dairyconsultant.co.uk/si-yoghurt.php, viewed 13/04/10Neil Moralee, 2002,http//www.cip.ukcentre.com/yogurt.htm, viewed 13/04/10Savello, 1998, http//www.patentstorm.us/patents/5762989/description.html viewed 28/04/10Tamime, A. Y. and Deeth, H. C. Yogurt technology and biochemistry, J. Food Protection, 43, 939, 1980.Wang S, 2000, http//www .eng.umd.edu/nsw/ench485/lab8.htm, viewed 28/04/10Brock C, 2005, http//www.fcs.msue.msu.edu/ff/pdffiles/foodsafety2.pdf, viewed 25/04/10Steane R, 2008, http//www.biotopics.co.uk/edexcel/biotechnol/yog.html, viewed 17/04/10