Fermentation in Dairy Products

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Questions and Answers

Which of the following statements accurately describes the role of Lactobacillus bacteria in fermentation?

Lactobacillus bacteria convert lactic acid into sugars.

Lactobacillus bacteria convert sugars into lactic acid. (correct)

Lactobacillus bacteria increase the protein content of foods.

Lactobacillus bacteria produce ethanol as the main byproduct.

What is a consequence of milk pH falling below 4.6?

The milk forms a cream layer.

Casein proteins begin to precipitate. (correct)

The whey becomes coagulated.

The lactose content increases significantly.

Which of the following best describes bongkrekic acid?

A non-toxic byproduct of Lactobacillus fermentation.

A toxin produced by Burkholderia gladioli. (correct)

A natural preservative generated during fermentation.

A common ingredient in Southeast Asian dairy products.

How does the fermentation process enhance the nutritional profile of food?

By increasing its digestibility and vitamin content. (B) Signup and view all the answers

What is the primary protein found in milk, and what percentage does it account for?

Casein; 80-85%. (D) Signup and view all the answers

Which condition is most likely to cause an increase in the pH level of cow's milk?

Mastitis infection. (C) Signup and view all the answers

What is the main function of lactic acid in fermented foods?

To act as a natural preservative. (A) Signup and view all the answers

Which of the following statements about milk composition is correct?

The carbohydrate content of milk is very low. (D) Signup and view all the answers

What is the primary purpose of milk pasteurization?

To destroy all disease-causing microorganisms (D) Signup and view all the answers

Which of the following describes the limitations of typical food industry heat treatments on endospores?

They inactivate vegetative cells but not spores (C) Signup and view all the answers

Which vitamin is NOT naturally abundant in cow's milk?

Vitamin C (B) Signup and view all the answers

What is the temperature and time requirement for the High Temperature-Short Time (HTST) pasteurization method?

161°F for 15 seconds (D) Signup and view all the answers

Which component of an endospore contributes to its chemical and enzymatic resistance?

Outer proteinaceous coat (A) Signup and view all the answers

In low temperature-long time (LTLT) pasteurization, what is the temperature used?

145°F (B) Signup and view all the answers

What is a consequence of the high-temperature pasteurization process on milk?

Denatures serum proteins (D) Signup and view all the answers

What is the typical leucocyte count in non-mastitic milk?

70,000/ml (C) Signup and view all the answers

What type of organisms are primarily targeted by the UHT treatment in milk?

Non-spore forming pathogens (C) Signup and view all the answers

Which temperature range is essential for effective UHT treatment of milk?

275–284°F (135–140°C) (B) Signup and view all the answers

What causes spoilage in UHT-treated milk?

Bacillus spp. that survive the UHT process (B) Signup and view all the answers

What distinguishes prebiotics from probiotics?

Prebiotics are substrates for indigenous bacteria, while probiotics are live beneficial organisms. (C) Signup and view all the answers

Which of the following pathogens is primarily associated with milk?

Staphylococcus aureus (B) Signup and view all the answers

What is a commonly used probiotic organism in yogurt production?

Streptococcus salivarius subsp. thermophilus (D) Signup and view all the answers

What is the typical shelf life of UHT-treated milk when aseptically packaged?

40–45 days (A) Signup and view all the answers

Which of the following statements regarding milk microbiota is accurate?

The udder of a healthy cow can have a high degree of microorganisms. (C) Signup and view all the answers

What role do bifidobacteria and anaerobic lactobacilli play in the colon?

They metabolize non-digestible substrates and support gut health. (D) Signup and view all the answers

Which of the following is a characteristic of lactose intolerance?

It can cause symptoms like flatulence and diarrhea after consuming lactose. (B) Signup and view all the answers

Why are lactic starters crucial in the dairy industry?

They facilitate lactic acid production essential for cheese making. (D) Signup and view all the answers

Which lactic starter is included when flavor compounds such as diacetyl are desired?

L.lactis subsp.cremoris (D) Signup and view all the answers

In the production of cultured sour cream, what is the initial step taken?

Fermenting pasteurized and homogenized light cream with a lactic starter. (C) Signup and view all the answers

What is the pH range typically produced by the rod bacteria during fermentation?

4.2 - 4.5 (A) Signup and view all the answers

What happens to the milk that remains after butter is churned?

It is referred to as buttermilk. (A) Signup and view all the answers

Which of the following statements about coccus and rod bacteria during fermentation is accurate?

Coccus bacteria produce a higher initial rate of lactic acid than rod bacteria. (C) Signup and view all the answers

Study Notes

Fermentation

Fermentation enhances shelf stability and provides distinct aroma and flavors from fermenting organisms.
Lactobacillus bacteria convert sugars into lactic acid, which acts as a natural preservative against harmful bacteria while preserving nutrients.
Bongkrekic acid, a toxin produced by Burkholderia gladioli, has been linked to cases of poisoning from fermented coconut and corn products.
Fermentation encompasses a range of chemical changes and is integral to food processing.

Dairy Products

Milk is a universal human food source derived from various mammals.
Milk contains 3.5% protein and 14.9% carbohydrates, primarily consisting of casein (80-85% of protein).
Milk pH typically ranges around 6.6 but can rise to 6.8 in infected cows (mastitis), which is caused by bacteria like Streptococcus and Staphylococcus species.
Fresh milk is an ideal medium for lactic acid bacteria, which thrive in its nutrient composition.

Processing: Pasteurization

Pasteurization aims to eliminate disease-causing microorganisms; however, it does not kill endospores from certain bacteria (e.g., Clostridium).
Common pasteurization methods include:
- Low temperature-long time (LTLT): 145°F (63°C) for 30 minutes.
- High temperature-short time (HTST): 161°F (72°C) for 15 seconds.
- Ultra-high temperature (UHT): 275-284°F (135-140°C) for a few seconds, yielding commercially sterile milk.

Microbiota and Pathogens

Fresh milk is generally not free from microorganisms, with potential pathogens including Brucellosis, Anthrax, and Salmonella.
Milk spoilage is primarily caused by specific bacteria that can metabolize lactose, unlike other sugars.

Probiotics and Prebiotics

Probiotics consist of live beneficial organisms, commonly found in yogurt, which utilizes Streptococcus thermophilus and Lactobacillus bulgaricus.
Prebiotics are non-digestible substrates that enhance the growth of beneficial bacteria in the colon, such as oligosaccharides and inulin.

Lactose Intolerance

Lactose intolerance is common in adults, where insufficient lactase leads to digestive symptoms upon milk consumption.

Starter Cultures and Fermented Products

Lactic starters, essential for cheese making and other dairy products, include various Lactobacillus strains.
Butter is made by churning inoculated cream; buttermilk remains after butter is produced.
Cultured sour cream is made by fermenting pasteurized cream, while yogurt fermentation involves both cocci and rods for lactic acid production, affecting the final product's acidity.

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Description

This quiz explores the processes of fermentation in milk and its impact on dairy products. Gain insights into the role of bacteria like Lactobacillus in enhancing flavor, aroma, and nutritional content of both fermented and non-fermented dairy. Understand the significance of fermentation in food preservation and digestibility.