Yogurt production Flashcards
Which approximately describes the percentage composition of protein, lactose and fat found in Cow’s milk?
Protein: 3.4%
Lactose: 4.6%
Fat:3.6%
Explain the denaturing stage in yoghurt production!
The whey proteins in the milk comprise of disulfide bonds which form compact spherical structures. Denaturing breaks these bonds enabling enhanced bonding with water molecules resulting with desirable textural properties for the yogurt.
Which of the following bacteria is NOT used in the production of yogurt?
(A) Lactobacillus bulgaricus
(B) Clostridium botulinum
(C) Streptococcus thermophilus
(D) Acidophilus bulgaricus
(B) Clostridium botulinum
Clostridium botulinum is an anaerobic, rod-shaped sporeforming bacterium that produces a neurotoxic protein. It can cause botulism, which is a severe form of food poisoning that happens when people ingest toxins released by clostridium botulinum.
During yogurt production, the milk sugar lactose is fermented into which products?
Glucose and galactose
Streptococcus thermophilus and Lactobacillus bulgaricus act synergystically. Products of each of their activity promotes development in the other species. Describe the growth process of these bacterium!
At an approximately 45°C, Streptococcus thermophilus will consume amino acids and sugars within the milk to aerobically produce lactic acid. This causes the pH to fall and allows Lactobacillus bulgaricus to thrive around 5.4-4.6 pH, since they require an acidic and anaerobic environment. Lactobacillus bulgaricus activity produces additional amino acids from the milk proteins further stimulating activity within Streptococcus and completing the cycle. Lactobacillus bulgaricus also produces lactic acid and as the pH reduces further, typically 1.5% lactic acid, which causes the rate of acivity within both species to reduce.
Describe the approximate percentages of proteins in milk!
About 80% is casein and 20% is whey protein (α-lactoglobulin, β-lactoglobulin, and serum albumin).
Why does plain yogurt have an acidic taste?
lactic acid presence
What are the effects of lactic acid on yoghurt?
- Gives the acidic taste.
- Acts as a natural perservative.
- Promotes a gel network within the yogurt, increasing its viscosity.
_______ is a major aromatic compound in yoghurts that gives its smell.
acetaldehyde
What are possible the stabilizers in yoghurt?
pectin, gelatin, or other similar modified starches
Why are stabilizers such as pectin added to yoghurt?
To improve the consistency of texture and build viscosity, which helps to minimize whey separation and bind free water molecules.
Define syneresis and give an example.
The separation of liquids from solids in food. It is highly undesired.
An example of this is when yoghurt or jam is left outside for too long without adequate stabilizers, there would be separation between the water on top and the solids on the bottom.
