Yogurt



Background

Yogurt is a dairy product, which is made by blending fermented milk with various ingredients that provide flavor and color. Although accidentally invented thousands of years ago, yogurt has only recently gained popularity in the United States.

It is believed that yogurt originated in Mesopotamia thousands of years ago. Evidence has shown that these people had domesticated goats and sheep around 5000 B.C. The milk from these animals was stored in gourds, and in the warm climate it naturally formed a curd. This curd was an early form of yogurt. Eventually, a process for purposely producing yogurt was developed.

While yogurt has been around for many years, it is only recently (within the last 30-40 years) that it has become popular. This is due to many factors including the introduction of fruit and other flavorings into yogurt, the convenience of it as a ready-made break-fast food and the image of yogurt as a low fat healthy food.

Manufacturers have responded to the growth in the yogurt market by introducing many different types of yogurt including low fat and no-fat, creamy, drinking, bio-yogurt, organic, baby, and frozen. Traditional yogurt is thick and creamy. It is sold plain and in a wide assortment of flavors. These are typically fruit flavors such as strawberry or blue-berry however, newer, more unique flavors such as cream pie and chocolate have also been introduced. Cereals and nuts are some-times added to yogurts. Yogurt makers also sell products with a varying level of fat. Low fat yogurt, which contains between 0.5% and 4% fat, is currently the best selling. Diet no-fat yogurt contains no fat at all. It also contains artificial sweeteners that provide sweetness while still reducing calories. Creamy yogurt is extra thick, made with whole milk and added cream. Drinking yogurt is a thinner product, which has a lower solids level than typical yogurt. Bio-yogurt is made with a different type of fermentation culture and is said to aid digestion. Yogurt that is made with milk from specially fed cows is called organic yogurt. This type of yogurt is claimed to be more nutritious than other yogurts. Other types of yogurts include pasteurized stirred yogurt that has extended shelf life, baby yogurt made specifically for children, and frozen yogurt.

The yogurt itself has a generally aldehydic flavor, which is a result of the fermentation process. Since it is made from milk, yogurt is rich in nutrients. It contains protein and vitamins and is a rich source of calcium. In fact, a small container of yogurt contains as much calcium as a third of a pint of milk. In addition to these nutritional characteristics, yogurt is also thought to have additional health benefits. One of the suggested benefits of yogurt is that it acts as a digestive aid. In the body, it is thought that yogurt can encourage the growth of beneficial bacteria in the gut. These organisms help to digest food more efficiently and protect against other, harmful organisms. Another health benefit of yogurt is for people that are lactose intolerant. These people have difficulty digesting milk products however, they typically can tolerate yogurt.

Raw Materials

In general, yogurt is made with a variety of ingredients including milk, sugars, stabilizers, fruits and flavors, and a bacterial culture

When the milk arrives at the plant, its composition is modified before it is used to make yogurt. This standardization process typically involves reducing the fat content and increasing the total solids. Once modification occurs, it is pasteurized to kill bacteria and homogenized to consistently disperse fat molecules.
When the milk arrives at the plant, its composition is modified before it is used to make yogurt. This standardization process typically involves reducing the fat content and increasing the total solids. Once modification occurs, it is pasteurized to kill bacteria and homogenized to consistently disperse fat molecules.
(Lactobacillus bulgaricus). During fermentation, these organisms interact with the milk and convert it into a curd. They also change the flavor of the milk giving it the characteristic yogurt flavor of which acetaldehyde is one of the important contributors. The primary byproduct of the fermentation process is lactic acid. The acid level is used to determine when the yogurt fermentation is completed which is usually three to four hours. The suppliers of these yogurt cultures offer various combinations of the two bacterial types to produce yogurts with different flavors and textures.

To modify certain properties of the yogurt, various ingredients may be added. To make yogurt sweeter, sucrose (sugar) may be added at approximately 7%. For reduced calorie yogurts, artificial sweeteners such as aspartame or saccharin are used. Cream may be added to provide a smoother texture. The consistency and shelf stability of the yogurt can be improved by the inclusion of stabilizers such as food starch, gelatin, locust-bean gum, guar gum and pectin. These materials are used because they do not have a significant impact on the final flavor. The use of stabilizers is not required however, and some marketers choose not to use them in order to retain a more natural image for their yogurt.

To improve taste and provide a variety of flavors, many kinds of fruits are added to yogurt. Popular fruits include strawberries, blueberries, bananas, and peaches, but almost any fruit can be added. Beyond fruits, other flavorings are also added. These can include such things as vanilla, chocolate, coffee, and even mint. Recently, manufacturers have become quite creative in the types of yogurt they produce using natural and artificial flavorings.

The Manufacturing
Process

The general process of making yogurt includes modifying the composition of and pasteurizing the milk; fermenting at warm temperatures; cooling it; and adding fruit, sugar, and other materials.

Modifying milk composition

Pasteurization and homogenization

Fermentation

Adding other ingredients

Quality Control

Milk products such as yogurt are subject to a variety of safety testing. Some of these include tests for microbial quality, degree of pasteurization, and various forms of contaminants. The microbial quality of the incoming milk is determined by using a dye reaction test. This method shows the number of organisms present in the incoming milk. If the microbial count is too high at this point, the milk may not be used for manufacture. Since complete pasteurization inactivates most organisms in milk, the degree of pasteurization is determined by measuring the level of an enzyme in the milk called phosphatase. Governmental regulations require that this test be run to ensure that pasteurization is done properly. Beyond microbial contamination, raw milk is subject to other kinds of contaminants such as antibiotics, pesticides or even radioactivity. These can all be found through safety testing and the milk is treated accordingly.

In addition to safety tests, the final yogurt product is also evaluated to ensure that it meets the specifications set by the manufacturer for characteristics such as pH, rheology, taste, color, and odor. These factors are tested using various laboratory equipment such as pH meters and viscometers and also human panelists.

The Future

The future of yogurt manufacturing will focus on the development of new flavors and longer lasting yogurts. The introduction of new flavors will be driven by consumer desires and new developments by flavor manufacturers. The suppliers of the bacterial cultures are conducting research that hints at the development of uniquely flavored yogurts. By varying the types of organisms in the cultures, yogurt is produced much faster and lasts longer than conventional yogurt.

Additionally, the nutritional aspects of yogurt will be more thoroughly investigated There is some evidence that has shown consumption of yogurt has a beneficial antibiotic effect. It has also been shown to reduce the incidence of lactose intolerance and other gastro-intestinal illnesses. Other purported benefits of yogurt include the reduction of cholesterol, protection against certain cancers, and even boosting the immune system. The research is still not complete on these benefits however, these factors will likely be important in the continued market growth of yogurt.

Where to Learn More

Books

Helferich, W. and D. Westhoff. Yogurt: All About It, 1980.

Hui, Y.H., ed. Dairy Science and Technology Handbook. New York: Wiley VCH, 1992.

Robinson, R.K. "Snack Foods of Dairy Origin." In Snack Food. Edited by Gordon R. Booth. New York: Van Nostrand Reinhold, 1990, pp. 159-182.

Robinson, R.K and A.Y. Tamime. "Recent developments in yoghurt manufacture." In Modern Dairy Technology. Edited by B.J.F. Hudson. London: Elsevier Applied Science Publishers, 1986, pp 1-36.

Perry Romanowski



User Contributions:

1
Obi Theodora
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Aug 29, 2006 @ 9:09 am
The article is quite educative. But i will like you to add references to the article and also I want to know what happens to yoghurt during storage. That is what happens to the fat content, total solids and total soluble solids.
Thanks
2
shylesh
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Apr 9, 2008 @ 2:02 am
I would like to know more about yogurt preparation
3
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Dec 27, 2010 @ 3:15 pm
Can you recomend the best culture to be used as a starter to give a good taste of yogurt?
4
emma
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Feb 16, 2011 @ 9:21 pm
i was just wondering if you could possibly tell me what processes are taken to transform the raw materials in yoghurt into the manufactured food.

i.e if there is mixing, cooling, size reduction, heating etc??
please let me know asap!
5
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Sep 3, 2011 @ 7:19 pm
How can I prepare yogurt at home just for household consumption?
Thanks
6
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Sep 4, 2011 @ 2:02 am
why does the yellowish color appears though it is kept in the refrigerator?
7
mamodike
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Jul 13, 2012 @ 6:18 pm
I liked the article i think it was educational and i would like to know more. So how many products would be produced per day? how much electrical energy consumed is per day on production? and how much electrical energy would be used on refrigeration?. another thing, could you please point out the stages were energy is used and how? and also the main point were electricity is mostly used and how much of it is used.

I would real appreciate it if you answer my questions as soon as posssible

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