Food Processing

What is the result of heat treatment on milk proteins?

• Denaturation

• Blanching

• Creaming

• Froth formation

• Degradation

Answer explanation

Heat treatment of milk can lead to denaturation of milk proteins, which involves the unfolding of the protein molecules from their native structure. This can alter their functional properties such as solubility, viscosity, and emulsifying capacity. Denaturation can be both beneficial and detrimental depending on the desired properties of the final product. For example, denaturation of whey proteins in cheese production is important for proper curd formation and texture, while denaturation of casein proteins in UHT milk can lead to sedimentation and off-flavors.

Tags

NGSS.MS-PS1-4

What is the effect of pasteurisation on vitamins in milk?

• Great loss

• Increase

• Sublime

• Little or no loss

• Significant loss

Answer explanation

Pasteurization involves heating milk to a specific temperature for a specified time to kill harmful bacteria while preserving the quality and taste of the milk. Although pasteurization may result in some loss of heat-sensitive vitamins such as thiamin, riboflavin, and vitamin C, the loss is generally small and not considered nutritionally significant. Most other vitamins in milk are relatively stable to heat and are not significantly affected by pasteurization.

Which of the following is the time-temperature combination for thermisation?

• 57 to 68 °C for 15 sec

• 63 °C for 30 min

• 72 to 74 °C for 15 to 20 sec

• 120 °C for 3 min

• 135 to 140 °C for 2 to 4 sec

Answer explanation

Thermisation is a milder heat treatment than pasteurization, and is sometimes used as an alternative to pasteurization for milk that will be used in the production of cheese or other dairy products.

Thermisation is used to partially heat-treat raw milk to reduce the number of bacteria present, without altering its nutritional and sensory qualities as much as pasteurization would. It is often used for artisanal and specialty dairy products, where the goal is to maintain the natural characteristics of the milk while still ensuring its safety. Thermisation can also help to extend the shelf life of the milk and reduce the risk of spoilage during storage.

Which of the following is the time-temperature combination for LTST pasteurisation?

• 57 to 68 °C for 15 sec

• 63 °C for 30 min

• 72 to 74 °C for 15 to 20 sec

• 120 °C for 3 min

• 135 to 140 °C for 2 to 4 sec

Answer explanation

LTST (Low Temperature Short Time) pasteurization is also known as the Holding method, as it involves heating milk to a lower temperature for a longer duration than HTST (High Temperature Short Time) pasteurization. In LTST, milk is typically heated to 63°C and held at that temperature for 30 minutes, while in HTST, milk is heated to a higher temperature of 72-74°C and held for a shorter time of 15-20 seconds.

Tags

NGSS.HS-PS3-4

Which of the following is the time-temperature combination for HTST pasteurisation?

• 57 to 68 °C for 15 sec

• 63 °C for 30 min

• 72 to 74 °C for 15 to 20 sec

• 120 °C for 3 min

• 135 to 140 °C for 2 to 4 sec

Which of the following is the time-temperature combination for UHT?

• 57 to 68 °C for 15 sec

• 63 °C for 30 min

• 72 to 74 °C for 15 to 20 sec

• 120 °C for 3 min

• 135 to 140 °C for 2 to 4 sec

What is the method of using the heat of a hot liquid, such as pasteurized milk, to preheat cold incoming milk?

• Heating

• Cooling

• Power saving

• Regeneration

• Standardisation

Answer explanation

Regeneration is a heat exchange process that uses the heat of a hot liquid or product to preheat a cold incoming liquid or product. In the dairy industry, this process is commonly used in milk processing plants to preheat cold raw milk before pasteurization.

During the regeneration process, the cold raw milk is passed through a heat exchanger that is in contact with the hot pasteurized milk exiting the pasteurizer. This allows the cold milk to be preheated to a higher temperature before entering the pasteurizer, reducing the amount of energy required to heat the milk to the pasteurization temperature.

By using the heat of the pasteurized milk to preheat the cold incoming milk, the regeneration process saves energy and reduces the overall operating cost of the pasteurization system. This is because the heat of the pasteurized milk is recovered and reused, rather than being lost to the environment.

Tags

NGSS.MS-PS3-3

NGSS.MS-PS3-4

Which of the following methods refers to the deactivation of microbes in food using electricity?

• Power ultrasound

• High-pressure processing

• Pulsed electric field

• Hurdle technology

• All of the above

Answer explanation

Pulsed electric field (PEF) is a non-thermal food processing technology that uses short pulses of high-voltage electrical energy to inactivate microorganisms in food. PEF treatment can help to preserve the quality and nutritional value of food while also improving its safety by reducing the microbial load. The process works by applying an electric field to the food product, which causes the microbial cell membranes to become permeabilized or ruptured, leading to cell death. PEF can be used on a variety of food products, including juices, milk, and liquid eggs.

When several factors for food processing and preservation are applied to one food product, it is called _________.

• Hurdle technology

• Mix and match processing

• Symbiotic method

• Mutualism approach

• None of the above

Answer explanation

Hurdle technology is a food preservation approach that involves combining multiple factors or hurdles to make the food product more resistant to microbial growth and spoilage. The hurdles can be physical, chemical, or biological, and they are applied in a way that creates a synergistic effect, meaning the combined effect is more significant than the individual effect of each hurdle. By applying multiple hurdles, the food product can be preserved without the use of high heat or chemical preservatives, which can alter the taste and nutritional value of the food. The hurdles used in hurdle technology can vary depending on the specific food product and desired outcome, but some common examples include controlling pH, water activity, temperature, and the use of antimicrobials.

In a spray dryer, what is the name of the spinning disc that distributes the liquid droplets in the drying chamber?

• Pulser

• Electron spinner

• Atomiser

• Atomic sprayer

• Metasizer

Answer explanation

A spray dryer is a device used to dry a liquid substance by spraying it into a hot air chamber, where the liquid evaporates and dries into a powder or fine particles. The atomizer is a component of the spray dryer that is responsible for breaking up the liquid into small droplets, which are then sprayed into the drying chamber. The spinning disc atomizer is a type of atomizer that uses a spinning disc to distribute the liquid droplets in the drying chamber.