Course:FNH200/2012w Team12 Yogurt

From UBC Wiki

Introduction

Yogurt originates from Eastern European and Western Asian nomadic tribes.[1] The product was unintentionally discovered through the fermentation of milk which was stored in animal skins at warm climates.[1] Presently, yogurt is produced through the fermentation of milk by harmless bacterial cultures and follows comprehensive processing steps to achieve the desired texture and sensory properties. The market offers a wide range of yogurt varieties to meet consumer preferences. Manufacturers employ appropriate packaging techniques and provide storage information to minimize contamination and prevent food-borne illnesses. Furthermore, the increasing popularity of yogurt and its versatility has led to functional applications in today’s consumer-driven market.

Homemade Yogurt

With increasing demand and popularity in Canada, it is crucial for food manufacturers to employ appropriate processing and packaging methods to provide consumers with safe, high quality yogurt. Also, it is important to consider sensory properties when manufacturing yogurt, because customers are always looking for products that would meet their preferences. On this Wiki page, our main focus is to answer the following questions:

  • What are some regulations that Canada has to standardize yogurt manufacturing process?
  • What kind of advancements to yogurt have been made to ensure consumer safety and to adapt to consumer fancy?
  • What can we (as consumers) do to eat yogurt in a safe manner?

In addition, this page is going to briefly discuss the history, statistics on Canadian yogurt production/consumption, the different applications of yogurt, and related food-borne illnesses.

History

One of the prevailing beliefs of yogurt’s origin dates back to roughly the 3rd Millennium BC (about 5000 years ago) in what is now Turkey.[2]Yogurt was happened upon by Turkish goat herders who kept milk in goatskin bags which was spontaneously fermented by bacteria that existed in those containers.[2] Throughout history, yogurt has been celebrated as a food product with healing benefits and positive effects on longevity.

Commercial yogurt production in Europe and the United States began with the Carasso father-son duo beginning in 1916. Isaac Carasso founded Dannon to produce yogurt products out of his concern for children suffering from intestinal disorders which was influenced by the studies of Dr. Elie Metchnikoff[3].

In Canada, yogurt production is attributed to a Quebecois from Trois-Rivieres, Jude Delisle, who discovered yogurt and its health benefits while on a trip in France.[4] Delisle received assistance from the Pasteur Institute of France and acquired a lactic starter to begin the production of yogurt himself.[4] Deslisle joined the Danone Group and became Danone Canada in 1997 and to this day, Danone Canada leads Canadian yogurt production.[4]

Statistics

In the last twenty years, yogurt consumption has been growing in Canada.[5] Most notably, yogurt consumption has increased by 22%, between 2005 and 2010, growing from 6.77 litres per capita to 8.28 litres per capita.[5] Concerning Canadian yogurt production, the 2012 calendar year saw yogurt production at 312 633 (‘000 kg) which is a slight decline from 2011 where yogurt production was at 315 413 (‘000 kg).[6] However, since 2007, yogurt production has increased by 18.35%.[6]


Regulations in Canada

In Canada, the Food and Drugs Act and Regulations set the standard of food products by specifying the composition of different foods, approved food additives, and labeling regulations.[7] These laws were created to ensure the quality of food manufactured and sold in Canada. Although there is no federal standard of yogurt,[7] the National Dairy Code defines yogurt as a product obtained from fermentation of Lactobacillus bulgaricus and Streptococcus thermophilus to generate lactic acid.[8] Moreover, this code specifies permitted ingredients and additives in yogurt, and labelling regulations.[8] Since this code is created by the Federal/Provincial/Territorial Food Safety Committee (previously known as the Canadian Food Inspection System Implementation Group) and is not forced by the federal law, food manufacturers can apply the standard listed in the National Dairy Code voluntarily.[9]

Production and Processing

Ingredients

Although yogurt can be produced using the milk of various animals, most industrialized yogurt is produced using cow’s milk.[10] Whole milk, partially skimmed milk, skim, or whole milk enriched with cream may used. In order to ensure the development of the yogurt culture, the following criteria for the raw milk must be met:[11][12]

  • low bacteria count
  • free from antibiotic, sanitizing chemicals, mastitis milk, colostrum, and rancid milk
  • no contamination by bacteriophage


Yogurt may also include some or all of the following ingredients:

Other dairy products: concentrated skim milk, non fat dry milk, whey, and/ or lactose. These products are often used to increase the nonfat solids content.

Sweeteners: glucose, sucrose, and/ or high- intensity sweeteners (eg. aspartame).

Stabilizers: gelatin, carboxymethyl cellulose, locust bean gum, guar gum, alginates, carrageenans, and/ or whey protein concentrate.

Flavors and Fruit Preparations: natural and artificial flavouring, assorted fruits.[10]

Manufacturing process

From start to finish, the production of yogurt takes several hours to allow for optimal fermentation. During its large-scale production in yogurt companies, the specific conditions, environment, and temperatures are critical in ensuring consistent results of the final product [13].

1. Adjustment of milk composition and blending of ingredients: Milk composition may be adjusted to achieve the desired fat and solids content. This is done by clarifying and separating the cream from the skim milk.[12] Often, dry milk is added to increase the amount of whey protein to provide the desirable texture. Stabilizers may also be added.[13]

2. Milk Pasteurization: The milk mixture is pasteurized at 85ºC for 30 minutes or at 95ºC for 10 minutes to denature the whey (serum) proteins, allowing the proteins to coagulate and form a more stable gel, which prevents separation of the water during storage. The heat treatment also reduces the number of spoilage organisms in the milk to provide a better environment for the starter cultures to grow. During this process, the surface of the casein micelle becomes modified so that the milk thickens in a structurally different manner than it would in a non heated acid gel.[12][13]

3. Homogenization: The blend is homogenized to mix all ingredients thoroughly and improve yogurt consistency.[13]

4. Cooling: The milk is cooled to 42ºC to bring the yogurt to the ideal growth temperature for the starter cultures, L. bulgaricus and S. thermphilus.[12][13]

5. Inoculation with Starter Culture: The starter cultures are mixed into the cooled milk.[13]

6. Holding: The milk is held at 42ºC until a pH of 4.5 is reached.[12] This allows the fermentation to progress to form a soft gel and the characteristic flavor of yogurt. This process can take several hours. Given the right conditions, the bacteria would be able to ferment lactose and produce lactic acid.[13]

7. Second Cooling: The yogurt is cooled to 7ºC to stop the fermentation process.[12]

8. Addition of Fruit and Flavours: Fruit and flavours are added at different steps depending on the type of yogurt. (Refer to Varieties of yogurt).[13]

9. Packaging: The yogurt is pumped from the fermentation vat and packaged into various containers including Tetra Paks, mini pots, sharing tubs, and cups.[13][14] Tetra Brik and Top, two varieties of Tetra Paks, are ideal for packaging yogurt-based drinks or smoothies.[14] Unlike yogurt-based drinks, yogurt is packaged into small pots, sharing tubs, and cups, so that it is easy to scoop the content from these containers. Sterilization of containers is imperative to prevent potential contamination of yogurt. Tetra Paks are treated with hydrogen peroxide for sterilization while other containers are treated with UV light, prior to filling them with yogurt.[15][16]

  • Sharing Tub

    Sharing Tub

  • Yogurt Cup

    Yogurt Cup

  • Tetra Rex

    Tetra Rex

  • Tetra Brik

    Tetra Brik

This is a video showing the packaging of yogurt.

Sensory Properties

Sensory perception of yogurt is an important factor to consider during manufacturing process, because a wide range of yogurt needs to be produced to meet consumer preferences. Manufacturers can practice different methods to create various flavours and textures of yogurt.

Flavour

L. bulgaricus and S. thermphilus are added as starter cultures, microorganisms that are used in manufacturing process of cultured dairy products, in yogurt processing to compensate uncontrollable and inefficient microbial activity of naturally-occurring microflora in milk.[12] Although both organisms can grow independently, food manufacturers utilize both cultures to enhance the rate of lactic acid fermentation.[11][17]High levels of lactic acid synthesis is the key for yogurt production, because it is the main contributor to yogurt’s sour taste.[18] Furthermore, it is known that acetaldehyde, a product of S. thermphilus fermentation, is known to be a key contributor to yogurt’s aroma, and higher concentration of this compound provides a better flavour.[17] Fruits and flavouring agents (eg. aspartame and honey) are often added to yogurt to eliminate undesired flavour and result in a positive impact on the acceptability of yogurt.[19] Finally, fat content of yogurt has a significant impact on the flavour, because many flavour compounds are hydrophobic and fat would act like a solvent for these compounds.[17]

Texture

Texture of yogurt can be altered by fat content and different processing techniques. Yogurt with higher fat content not only enhances the flavour, but it also results in a product with high viscosity and richness.[10] Heat treatment of milk prior to fermentation is known to create a firmer texture compared to untreated milk, because whey protein starts to interact with casein during denaturation (caused by heat treatment at temperature >70ºC).[20] To achieve lower viscosity, manufacturers can mix yogurt at high speed to breakdown coagulants after the fermentation period.[21]

Proper Storage and Handling of Yogurt

Before purchasing yogurt, it is important that consumers pay close attention to the “best before” date that is printed on the label. This date indicates the date before which the yogurt still retains its physical and chemical properties during the time of manufacture. In other words, the yogurt has not changed significantly in its taste or appearance.[22] Therefore, for the best- quality experience, it should be consumed before this date.[23]

After buying it, try to place it in the refrigerator as soon as possible. Ideally it should not have warmed up after purchase and should still be relatively cool. To maintain ideal flavours and textures, store the yogurt on the shelves where the temperature is typically cooler than in the door of the refrigerator. To prevent negative alterations of the texture and flavor, do not store it in the freezer.[22] Doing so may also destroy the live culture activity in the product.[23] However, you may be able to prolong its shelf-life by storing it in the freezer. If you choose to freeze it, thawing the yogurt in the refrigerator is necessary before consuming.[24] After opening the container, try to consume it within a week. If it isn’t all consumed in one serving, protect the yogurt from contamination and odors by sealing the container tightly. It is also recommended that you use a clean spoon to take as much yogurt as you plan to consume into a bowl, and eat from the bowl, instead of eating directly from the container. If there happens to be left-over yogurt in the bowl, avoid returning it to the original container to lower the chance of contamination.[22] If you notice mould appearing in the container, discard the product.[24] If there is separation and you see a watery layer on top, you may gently stir it back in.[25] Or, you may choose to pour it off.[23]

Food-borne Illnesses

Raw Milk and Yogurt Production

Although milk is required to be pasteurized for sale in Canada,[7] individuals may choose to drink or produce dairy products from raw milk that is obtained directly from dairy farms. Individuals may choose to consume dairy products made from raw milk because raw milk is believed to boost one’s immune system and is more easily digestible for individuals with lactose intolerance.[26] Despite the potential benefits of raw milk, public health officials are concerned about its consumption and processing. BC Centre of Disease Control states that raw milk is unsanitary due to fecal and environmental contamination.[27] Moreover, the absence of milk pasteurization could result in pathogenic bacteria (Listeria, Salmonella, E. coli O157:H7, and Campylobacteria) in milk, which could be hazardous for those with a weaker immune system.[27] Thus, usage of raw milk in yogurt production may expose one to various food-borne illnesses and people should be cautious when consuming yogurt made from raw milk.

Yogurt contamination during processing

Yogurt manufactured from pasteurized milk is generally safe, but improper handling of milk during the manufacturing process could lead to the contamination of yogurt. In 1991, an E.Coli O157:H7 outbreak in England resulted in individuals (1-56 years old) that suffered from diarrhea and acute renal failure.[28]Although there were several problems identified in the manufacturing plant, the most likely cause of contamination during this yogurt processing was due to inadequate pasteurization or improper cleaning of the mobile pump.[28] This case implies that proper cleaning method and processing are necessary to prevent contamination and food-borne illnesses during yogurt production.

Yogurt's Functional Applications

Yogurt contributes to a wide range of health benefits and is gaining recognition for its functional properties.[29][30] Yogurt meets today’s health-conscious consumer demands as it is commonly used as a fat substitute to reduce calorie and fat content in certain foods.[31][32][33] Moreover, the product’s specific properties create practical uses in marinades to facilitate the tenderization of meats.[30]

Applications of yogurt includes being an ingredient used in tzatziki sauce

Yogurt-Based Fat Substitutes

Yogurt-based fat substitutes appeal to consumer demands for products with low calorie and fat content. Due to its contribution of daily calcium requirement and lower caloric contribution, low-fat yogurt is commonly used as substitutes for oil and butter in many recipes.[30][32] When substituting fat with yogurt, it is essential to use unsweetened, plain yogurt achieve a taste similar to the food being made.[31][32] However, yogurt’s wide availability of flavours enables consumers to incorporate it into baked goods in order to enhance desirable flavours.[32] Furthermore, the substitution of yogurt in recipes that require baking powder or baking soda produces airy textures.[32] The product’s extra moisture content requires for one cup of oil or butter to be replaced with three-fourths cup of yogurt.[32] Yogurt-based fat substitutes are commonly used in cakes, chocolate baked goods, biscuits, muffins, and quick breads.[34] Shorter baking time is usually required when using yogurt-based fat substitutes due to yogurt’s low fat content which increases vulnerability of overcooking the final product.[34]

Yogurt in Marinades

Yogurt is often used in marinades due to its specific properties that enhance the tenderness of certain meats.[30] Lactic acid in yogurt makes the product slightly acidic at a pH as high as 5.5, which provides an optimal environment for protein denaturation in meat.[35][36] A common application of yogurt marinades is to tenderize tough lamb and goat meats in Indian cuisine.[36]

Summary

In conclusion, yogurt lacks federal standards under the Food and Drug Regulations. However, standardized processing steps allow manufacturers to achieve consistent results in the production of yogurt that is safe for consumption for the population. Over the years, more flavours and different packaging techniques have been developed to adapt to consumer preferences. In order to enjoy the benefits of yogurt, it is important to be aware of and practice the proper storage techniques, for example storing it in the refrigerator to prevent spoilage while keeping it fresh. Consumers should also be aware of the risks of using raw milk for yogurt production, as it is likely to contain pathogenic bacteria.

Yogurt will continue to increase in popularity and be on demand as the generation who grew up with it become parents and introduce it to their children. Yogurt companies will continue to develop new products to appeal and attract the needs and preferences of consumers.


As a wrap up, here is a video that includes key information about yogurt and tells the story of how it is made.

Exam question

Which of the following is/are not a method(s) used to improve the safety of commercially-sold yogurt nowadays?

  1. pasteurize the milk at 85ºC for 30 minutes
  2. pasteurize the milk at 95ºC for 10 minutes
  3. homogenization
  4. storing the yogurt in the freezer

A) 2

B) 1 & 3

C) 2 & 3

D) 3 & 4 (right answer)

E) 1, 3, & 4

References

  1. ↑ 1.0 1.1 Nummer, B. A. (2002). Fermenting yogurt at home. Retrieved from http://nchfp.uga.edu/publications/nchfp/factsheets/yogurt.html
  2. ↑ 2.0 2.1 Danone. (2013). A brief history of yogurt. Retrieved from http://downtoearth.danone.com/2013/01/31/a-brief-history-of-yogurt/
  3. ↑ Danone (n.d.). The history of Danone. Retrieved from http://www.danone.com/en/press-releases/cp-mai-2009.html
  4. ↑ 4.0 4.1 4.2 Danone. (n.d.). Danone's history. Retrieved from http://www.danone.ca/en/company/history
  5. ↑ 5.0 5.1 Canadian Dairy Commission. (2012). Consumption. Retrieved from http://www.cdc-ccl.gc.ca/CDC/index-eng.php?id=3800
  6. ↑ 6.0 6.1 Government of Canada. (n.d.). Production: Yogurt. Retrieved from http://www.dairyinfo.gc.ca/pdf/prod_yogurt.pdf
  7. ↑ 7.0 7.1 7.2 Food and Drug Regulations, C.R.C., c. 870 (2013). Retrieved from http://laws.justice.gc.ca/eng/regulations/C.R.C.,_c._870/index.html.
  8. ↑ 8.0 8.1 Federal/Provincial/Territorial Food Safety Committee. (2006). National Dairy Regulation and Code: Processing Sector interpretive Guidelines. Retrieved from: http://www.dairyinfo.gc.ca/pdf/Interpretive%20Guidelines_Processing_e.pdf
  9. ↑ Canadian Food Inspection System. (2009). Important Information. Retrieved from: http://epe.lac-bac.gc.ca/100/206/301/cfia-acia/2011-09-21/cfis.agr.ca/english/indexe.shtml
  10. ↑ 10.0 10.1 10.2 Dairy Goodness. (2013). “Types of Yogurt”. Retrieved from http://www.dairygoodness.ca/yogurt/types-of-yogurt
  11. ↑ 11.0 11.1 The Dairy Council. (2013). “Production of Yogurt”. Retrieved from http://www.milk.co.uk/page.aspx?intPageID=81.
  12. ↑ 12.0 12.1 12.2 12.3 12.4 12.5 12.6 University of Guelph. (2009). “Yogurt and Fermented Beverages”. Retrieved from: http://www.uoguelph.ca/foodscience/dairy-science-and-technology/dairy-products/cultured-dairy-products/yogurt-and-fermented-beverages.
  13. ↑ 13.0 13.1 13.2 13.3 13.4 13.5 13.6 13.7 13.8 Milk Facts. (2013). “Yogurt Production”. Retrieved from http://www.milkfacts.info/Milk%20Processing/Yogurt%20Production.htm
  14. ↑ 14.0 14.1 Tetra Pak. (n.d.). “Selection of carton packages for yogurt and yogurt drinks”. Retrieved from http://www.tetrapak.com/packages/customerdesign/pages/default.aspx#/~Yoghurt--Yoghurt-based_drinks
  15. ↑ Tetra Pak (n.d.). Aseptic packaging. Retrieved from http://www.tetrapak.com/products_and_services/aseptic_solutions/aseptic_packaging/Pages/default.aspx
  16. ↑ D20400077 (2009). Yoghurt packaging machine [Video file]. Retrieved from http://www.youtube.com/watch?v=XjiP7MsNt8k
  17. ↑ 17.0 17.1 17.2 Routray, W., & Mishra, H. (2011) Scientific and technical aspects of yogurt aroma and taste: a review. Comprehensive Reviews in Food Science and Food Safety. 10(4), 208-220. doi: 10.1111/j.1541-4337.2011.00151.x
  18. ↑ Beshkova, D., Simova, E., Frengova, G. & Simov, Z. (1998).Production of flavour compounds by yogurt starter. Journal of Industrial Microbiology & Biotechnology, 20, 180-186. doi: 10.1038/sj.jim.2900504
  19. ↑ Astawan, M., Wresdiyati, T., Sulliantari, S., Arief, I. & Septiawan, R. (2012). Production of symbiotic yogurt-like using indigenous lactic acid bacteria as functional food. "Media Peternakan", 35, 9-14. doi| 10.5398/medpet.2012.35.1.9
  20. ↑ Lee, W. J. & Lucey, J. A. (2010). Formation of physical properties of yogurt. The Asian-Austrailian Association of Animal Production Societies. 23. 1127-1136. Retrieved from http://www.ajas.info/pdf/23-149.pdf
  21. ↑ Allgeyer, L. C., Miller, M. J., & Lee, S. Y. (2010). Sensory and microbiological quality of yogurt drinks with prebiotics and probiotics. Journal of Dairy Science. 93, 4471-4479. doi: 1 0.3168/jds.2009-2582
  22. ↑ 22.0 22.1 22.2 Dairy Farmers of Canada. (n.d.). “How to Store Yogurt”. Retrieved from http://www.dairygoodness.ca/yogurt/how-to-store-yogurt
  23. ↑ 23.0 23.1 23.2 The Dannon Company. (n.d.). What’s the best way to store Dannon yogurt?. Retrieved from http://www.dannon.com/pdf/yogurtStored.pdf
  24. ↑ 24.0 24.1 StillTasty. (n.d.). Food Storage – How long you can keep Yogurt. Retrieved from http://www.stilltasty.com/fooditems/index/18717
  25. ↑ Weatherford Democrat. (2008). “How to store and keep yogurt at its best”. Retrieved from http://weatherforddemocrat.com/food/x1155989934/How-to-store-and-keep-yogurt-at-its-best.
  26. ↑ Wintonyk, D. (2010). Raw milk: magic elixir or health hazard?. Retrieved from: http://bc.ctvnews.ca/raw-milk-magic-elixir-or-health-hazard-1.475735
  27. ↑ 27.0 27.1 BC Centre of Disease Control. (2012). Raw Milk. Retrieved from http://www.bccdc.ca/foodhealth/dairy/Raw+Milk.htm
  28. ↑ 28.0 28.1 Morgan, D., Newman, C. P., Hutchinson, D. N., Walker, A. M., Rowe, B., and Majid, F. (1993). Verotoxin producing Escherichia coli O 157 infections associated with the consumption of yoghurt. Epidemiology and Infection. 111: 181-187. doi:10.1017/S0950268800056880
  29. ↑ Biswas, S. (2010). Yogurt and the functional food revolution. BBC News. Retrieved from http://www.bbc.co.uk/news/business-11926609
  30. ↑ 30.0 30.1 30.2 30.3 Stonyfield Farm Incorporated. (2011). Yogurt cooking tips. Retrieved from http://www.stonyfield.com/recipes/cooking-yogurt/yogurt-cooking-tips
  31. ↑ 31.0 31.1 Moncel, B. (2013). Fat substitutes for baking: Replacement options for reducing fat in baked goods. Retrieved from http://foodreference.about.com/od/Ingredient_Substitutions/a/Fat-Substitutes-For-Baking.htm
  32. ↑ 32.0 32.1 32.2 32.3 32.4 32.5 Makkieh, K. & Media, D. (2013). The advantages of using yogurt as a fat replacer. Retrieved from http://healthyeating.sfgate.com/advantages-using-yogurt-fat-replacer-2504.html
  33. ↑ Radi, M., Niakousari, M. & Amiri, S. (2009). Physicochemical, textural and sensory properties of low-fat yogurt produced by using modified wheat starch as a fat replacer. Journal of Applied Sciences. 9, 2194-2197. doi: 10.3923/jas.2009.2194.2197
  34. ↑ 34.0 34.1 Thayer, A. (2010, August 19). Baking alternative – reducing fat in your favorite baked goods recipes [Web log message]. Retrieved from http://www.wilton.com/blog/index.php/baking-alternatives-reducing-fat-in-your-favorite-baked-goods-recipes
  35. ↑ Russo, J. (2011). How acidic is yogurt?. Retrieved from http://www.livestrong.com/article/394657-how-acidic-is-yogurt/
  36. ↑ 36.0 36.1 Anderson, J. (2012). “How to tenderize steak, beef, other meats, steak marinade recipes”. Retrieved from http://janderson99.hubpages.com/hub/How-to-Tenderize-Steak-Beef-Other-Meats-Steak-Marinade-Recipes
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