Chapter 8 - New Technologies

Question 1

What is the difference between the Bactofuge and the Bactocatch?

Answer 1

While both methods separate the bacteria from the main stream and later recombine them after heat treatment, the Bactofuge does so by centrifugation (difference in density) and the bactocatch does so by sieving out the bacteria with use of a membrane (separation by size).

• In the Bactocatch skimmed milk is used.

Question 2

What is the difference in shelf life between pasteurized milk and Bactocatch milk?

Answer 2

The shelf life is almost twice as large in the refrigerator.
- CFU < 10 at 6 degrees, while pasteurized milk is 10^2 -10^6 CFU.
- The shelf life is almost 30 days.

Besides, the taste is considered better as the milk is not treated at high temp.

Question 3

In which two ways does HPP inactivate microbes?

Answer 3

• Cell membrane destruction (phospholipids crystallize)
• DNA destabilization

Besides, it does not inactivate spores.

Question 4

How can you pre-gelatinize soups?

Answer 4

With HPP, when starch clusters break open under pressure. Amylose leaches out and dissolves in water.

Question 5

What is the effect of HPP on proteins, fats, and carbs respectively?

Answer 5

Proteins:
- Gelling.
- Reversible and irreversible denaturation.
- Enhanced digestibility.

Fats:
- Induced crystallization.
- Membrane change (phospholipids crystallize).

Carbs:
- Gelling (starch, cellulose, pectin).
- Decrease of gelling temp.
- No or low Maillard reaction.

Question 6

What is the effect of HPP on vitamins, enzymes, aroma/colour, and allergenicity respectively?

Answer 6

Vitamins:
- No or minor decrease

Enzymes:
- Activity increases or decreases (dependent on the structure)
- Enzyme kinetics altered

Aroma/colour:
- No browning due to Maillard reaction
- No aroma loss/ increase

Allergenicity:
- Could be reduced, but still little information available

Question 7

What products are best used for Pulsed Electric Fields?

Answer 7

Mostly liquid/semi-solid products of high conductivity.

Question 8

What are two possible reasons products might be pre-treated with PEF?

Answer 8

1) It increases extractability of plant material
2) It changes the texture:
- Pre-treated potato chips are smoother
- Sugars can leach out of the cells and be removed (less maillard browning)
- Flexible texture, so thinner slices which don’t break
- Thus less surface area, meaning less oil uptake (from 33 to 28%)

Question 9

What are the pro’s and cons of PEF?

Answer 9

Pro’s:
- Maintain aroma and colour of food
- Inactivate microbes
- Fast (1 s)

Cons:
- Initial cost very high
- No effect on enzymes
- Less effective on spores than temperature
- Only suitable for liquids
- Air bubbles could result in non-homogenous treatment

Question 10

What types of irradiation are there?

Answer 10

• UV
• Ionizing: Alpha, beta, gamma