yogurt as a milk product fermented by two bacterial strains: a lactic acid producing bacteria: Lactobacillus bulgaricus and Streptococcus thermophiles.pptx
yogurt as a milk product fermented by two bacterial strains: a lactic acid producing bacteria: Lactobacillus bulgaricus and Streptococcus thermophiles.
Contamination spoilage and preservation of milk and milk products
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yogurt as a milk product fermented by two bacterial strains: a lactic acid producing bacteria: Lactobacillus bulgaricus and Streptococcus thermophiles.pptx
2. YOGURT
• The word “yogurt” is believed to have come from the Turkish word “yogurmak,” which means to
thicken coagulate, or curdle.
• Today, the FDA defines yogurt as a milk product fermented by two bacterial strains: a lactic acid
producing bacteria: Lactobacillus bulgaricus and Streptococcus thermophiles.
• Yogurt is an ancient food that has been around for several millennia.
• One theory of the discovery of yogurt is during 10,000 – 5,000 BC.
• They stored their milk in bags made of the intestinal gut of the animals.
• The intestines contain natural enzymes that cause the milk to curdle and sour.
• The herdsmen noticed that this method of storing milk extends its shelf life and preserves it.
3. YOGURT
• Yogurt or yoghurt is a dairy product produced by bacterial fermentation of milk.
• The bacteria used to make yogurt are known as "yogurt cultures".
• Fermentation of lactose by these bacteria produces lactic acid, which acts on milk protein to give
yogurt its texture and its characteristic tang.
• According to FDA, yogurt is defined as the “food produced by culturing one or more of the
optional dairy ingredients (cream, milk, partially skimmed milk, and skim milk) with a
characterizing bacteria culture that contains the lactic acid-producing
bacteria, Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus”.
• It was named in the 8th century after the Turkish word “yogurmak,” which means to thicken,
coagulate, or curdle.
4. HISTORY
• Yogurt was created by accident when milk was exposed to bacteria or soured in warm
temperatures.
• Turkish texts from the 11th century (1100 BC to 1001 BC) mention yogurt being used by
nomadic Turks.
• Evidence from ancient pottery shows that Neolithic people were using pots to store milk.
• Indian texts place yogurt flavoured with cinnamon and mustard seed in the kitchen
of Indian emperor Akbar I, who reigned from 1556 to 1605 BC.
5. STARTER CULTURES IN PRODUCTION
• Dairy yogurt is produced using a
culture of Lactobacillus delbrueckii
and Streptococcus salivarius
bacteria.
• In addition, other Lactobacilli and
Bifidobacteria are also sometimes
added during or after culturing
yogurt.
6. TYPES OF YOGURT
• Yoghurt is the best known of all fermented milk products, and the most popular worldwide.
• The consistency, flavour and aroma vary from one district to another.
• In some areas, yoghurt is produced in the form of a highly viscous liquid, while in other countries it is in
the form of a softer gel.
• Yoghurt is also produced in frozen form as a dessert, or as a drink.
• The flavour and aroma of yoghurt differ from those of other acidified products, and the volatile aromatic
substances include small quantities of acetic acid and acetaldehyde.
• Yoghurt is typically classified as follows:
• Set type: incubated and cooled in the package.
• Stirred type: incubated in tanks and cooled before packing.
• Drinking type: similar to stirred type, but the coagulum is broken down to a liquid before being packed.
• Frozen type: incubated in tanks and frozen like ice cream.
• Concentrated: incubated in tanks, concentrated and cooled before being packed. This type is sometimes
called Greek yoghurt or strained yoghurt, sometimes labneh or labaneh
8. PRODUCTION OF YOGURT
• To make yogurt, milk is first heated to 180 degrees Fahrenheit for 30 minutes to denature
the whey proteins; this allows the proteins to form a more stable gel. The yogurt is
pasteurized before adding the cultures.
• The pasteurization process kills any pathogens that can spoil milk as well as to eliminate
potential competitors of the active cultures.
• After milk pasteurization, the milk is cooled down to 108 degrees Fahrenheit, the
temperature for optimal growth of yogurt starter cultures.
• Last, the yogurt starter cultures (probiotics) is added into the cooled milk and incubated
until a pH of below 5 is obtained. This is called the fermentation process, whereby lactose
in the milk is converted to lactic acid, which lowers the pH.
• When the pH drops below pH 5, micelles of caseins, which are amphiphilic proteins, loses
its tertiary structure due to the protonation of its amino acid residues.
• The denatured casein proteins reassemble by interacting with other casein proteins, and
these intermolecular interactions result in a network of molecules that provides the
semisolid texture of yogurt
9. COMPOSITION OF YOGURT
• The fermentation process is also essential for the tangy flavor of yogurt: the production
of lactic acid by Lactobacillus bulgaricus imparts a sour acidic and refreshing taste.
• A mixture of various carbonyl compounds like acetone, diacetyl and acetaldehyde are
also major contributors to the tarty yogurt flavor.
• Yoghurt has a high concentration of acetaldehyde due to the low utilization of this
metabolite by yoghurt bacteria, which lack alcohol dehydrogenase, the main enzyme
needed to convert acetaldehyde into ethanol During fermentation, acetaldehyde is
produced directly from lactose metabolism as a result of pyruvate decarboxylation.
• lactic acid bacteria also have alternative metabolic pathways that can produce
acetaldehyde
10. HEALTH BENEFITS
• Probiotic yogurt is associated with a variety of digestive health benefits.
• Regular consumption of yogurt with live and active cultures may help treat antibiotic-
associated diarrhea by restoring balance in your intestinal flora
• In addition, probiotic yogurt with Bifidobacteria may lessen the symptoms of IBS and
help reduce constipation
• Studies suggest that regular consumption of yogurt may lower blood pressure
• Yogurt contains less milk sugar (lactose) than milk. That’s because some of the lactose
in milk breaks down into glucose and galactose during yogurt production.Therefore, it
is better tolerated by people with lactose intolerance.
• Yogurt does not contain naturally is vitamin D, but it’s commonly fortified with
it. Vitamin D promotes bone and immune system health and may reduce the risk of
some diseases, including heart disease and depression
