Food Science Size Reduction Quiz

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Questions and Answers

What nutritional loss can decrease by up to 78% during the slicing of cucumber?

Thiamin

Vitamin D

Vitamin C (correct)

Vitamin A

How do emulsifying agents affect interfacial tension?

They reduce the interfacial tension between phases. (correct)

They increase the interfacial tension.

They enhance the viscosity of the liquids.

They prevent flavor loss in dry foods.

Which factors influence nutritional losses during storage?

Carbon dioxide levels, moisture content, and color.

Oxygen concentration, light exposure, and temperature. (correct)

Moisture content, light exposure, and size reduction.

Temperature, moisture content, and packaging type.

What effect does increased surface area during size reduction have on nutritional value?

It accelerates oxidation of fatty acids. Signup and view all the answers

What classification is used for emulsifiers with low HLB values (below 9)?

Lipophilic, used for w/o emulsions. Signup and view all the answers

Which volatile compounds are primarily lost during size reduction of spices and nuts?

Oils and aromatics. Signup and view all the answers

What is the primary benefit of using colloid mills in food processing?

To create high shearing forces for high-viscosity liquids Signup and view all the answers

What happens to the viscosity of the continuous phase when emulsifiers are added?

It is reduced, aiding droplet stability. Signup and view all the answers

How does ultrasonic homogenisation improve the characteristics of food emulsions?

By compressing and cavitating air bubbles to produce smaller droplets Signup and view all the answers

What is a common characteristic of synthetic emulsifiers like glycerol esters?

They are widely used in food processing. Signup and view all the answers

What is a significant effect of homogenisation on the texture of milk?

It creates a creamier texture by reducing fat globules Signup and view all the answers

What type of emulsion is margarine classified as?

Water-in-oil emulsion Signup and view all the answers

What is one of the nutritional benefits of homogenisation in food processing?

Improves digestibility of fats and proteins Signup and view all the answers

Which type of force is primarily used for reducing the size of brittle foods?

Compression forces Signup and view all the answers

What is a primary benefit of size reduction in food processing?

Enhances drying rates Signup and view all the answers

Which process is NOT typically associated with size reduction in solids?

Fermentation Signup and view all the answers

When a material exceeds its elastic limit, what is likely to occur?

Permanent deformation Signup and view all the answers

Which force type is most effective for processing fibrous foods?

Shearing (attrition) forces Signup and view all the answers

What potential negative effect can size reduction have on food quality?

Promotes enzymatic or microbial degradation Signup and view all the answers

What is one of the main considerations when controlling the size of particles during the reduction process?

Elastic stress limit Signup and view all the answers

How does size reduction impact ingredient mixing for food products like dried soups?

Enables more complete mixing Signup and view all the answers

What is the primary function of stabilizers in O/W emulsions?

Increase viscosity and prevent coalescence Signup and view all the answers

Which type of homogeniser is commonly used for emulsification of low-viscosity liquids?

High-speed mixers Signup and view all the answers

What characterizes the process of homogenization compared to emulsification?

It reduces droplet size and increases particle number. Signup and view all the answers

Ice cream is classified as what type of emulsion?

Oil in Water (O/W) Signup and view all the answers

What is the primary operation of pressure homogenisers?

Creating turbulence and shear forces at high pressure Signup and view all the answers

What is the main continuous phase in cake batters?

Starch, sugar, and flavors Signup and view all the answers

Which of the following is NOT a type of homogeniser mentioned?

Mechanical homogenisers Signup and view all the answers

Which of the following best describes water in oil (W/O) emulsions?

Examples include margarine. Signup and view all the answers

What is a primary benefit of using ultrasonic blades for size reduction?

They provide lower cutting force and reduced energy consumption. Signup and view all the answers

What is a suitable condition for cutting meats to enhance efficiency?

Tempering the meat just below freezing point. Signup and view all the answers

Which type of food requires food-grade lubricants for effective cutting?

Sticky foods like dates and candied fruits. Signup and view all the answers

Which of the following is NOT a type of size reduction equipment for fibrous foods?

Frying equipment. Signup and view all the answers

Why is knife blade sharpness important in food processing?

It minimizes the cutting force and prevents cell rupture. Signup and view all the answers

What characteristic of ultrasonic cutting technology enhances the cut quality?

Vibration at 20kHz with minimal disturbance. Signup and view all the answers

Which type of foods are typically dry particulate foods?

Grains and dry powders. Signup and view all the answers

What is a notable feature of ultrasonic cutting compared to traditional methods?

It allows for superior cut quality with cleaner cuts. Signup and view all the answers

Study Notes

Size Reduction Fundamentals

Size reduction, also known as comminution, is the process of decreasing the average size of solid food.
It involves grinding, compression, or impact forces.
Key processes for liquids include homogenization, emulsification, and atomization.
Increased surface area due to size reduction enhances drying rates, heating, cooling rates, and extraction efficiency.
It improves ingredient mixing for products such as dried soup and cake mixes.

Forces Utilized in Size Reduction

Compression Forces: Used to fracture brittle solids like crystalline foods.
Impact Forces: Used for hard materials, where collisions cause food to break apart along lines of weakness.
Shearing (Attrition) Forces: Employed for fibrous or softer foods, tearing them apart.

The Effect of Size Reduction on Food Quality

Quality Improvements: Enhanced eating quality, suitability for further processing, and an expanded range of available products.
Potential Degradation: May promote enzymatic or microbial degradation, requiring additional preservative treatments.

Equipment for Size Reduction of Solid Foods

Categories of Food Materials:
- Fibrous Foods: Meats, fruits, and vegetables with firm textures requiring specific cutting conditions.
- Dry Particulate Foods: Grains and dry powders, often reduced to fine powders for processing.

Importance of Knife Blade Sharpness

Sharp blades minimize cutting force, prevent cell rupture that leads to product damage and reduced yield.
Lubricants, like water for moist foods and food-grade lubricants for sticky foods, minimize friction during cutting.

Ultrasonic Cutting Technology

Introduced in the 1990s, utilizes blades or probes that vibrate at 20kHz, resulting in a cutting stroke of 50–100 µm.
Offers superior cut quality with minimal disturbance to food structure and lower cutting force.

Four Main Types of Size Reduction Equipment for Fibrous Foods:

Slicing and Flaking Equipment
Dicing Equipment
Shredding Equipment
Pulping Equipment

Advanced Slicing Equipment

Small, often unreported, changes in color, flavor, and aroma of dry foods may occur during size reduction.
Carotene oxidation can lead to bleaching and nutritional loss in dry foods.
Volatile compounds in spices and nuts are lost during size reduction.
Cell disruption in moist foods accelerates enzymatic reactions causing quicker flavor, aroma, and color deterioration.

Nutritional Value and Losses During Size Reduction

Increased surface area during size reduction accelerates the oxidation of fatty acids and carotenes.
Vitamin C and thiamin losses can be significant during size reduction (e.g., cucumber).
Nutritional losses during storage depend on temperature, moisture content, and oxygen concentration.

Size Reduction of Liquid Foods: Emulsification and Homogenization

Emulsification: Creates stable emulsions by mixing immiscible liquids.
Homogenization: Increases the intensity of emulsification, reducing droplet size and increasing particle number in the dispersed phase.

Theory of Emulsions

Oil in Water (O/W): Example: Milk.
Water in Oil (W/O): Example: Margarine.

Role of Emulsifying Agents

Reduce interfacial tension between phases, preventing droplet coalescence.
Lower the energy required to form emulsions.
Classified as polar or non-polar.
Examples: Glycerol esters, sorbitan esters of fatty acids.
HLB values specify the emulsifier's hydrophilic-lipophilic balance.

Stabilizers in Emulsions

Polysaccharide hydrocolloids function as stabilizers, forming viscous solutions or gels in water.
They increase viscosity in O/W emulsions, preventing coalescence.

Five Main Types of Homogenizers:

High-speed mixers
Pressure homogenizers
Colloid mills
Ultrasonic homogenizers
Hydroshear homogenizers and microfluidizers

High-speed Mixers

Utilize turbines or propellers to pre-mix emulsions of low-viscosity liquids.
Create shearing forces at the edges and tips of blades.
Commonly used for emulsification in food processing.

Pressure Homogenizers

High-pressure pumps operate at 10,000–70,000 × 10³ Pa.
Force liquid through a small gap at high velocity, creating turbulence and shear forces.
Widely used in milk pasteurization, ice cream, and soup production.

Colloid Mills

Disc mills with a small clearance between rotating and stationary discs.
Generate high shearing forces suitable for high-viscosity liquids.
Effective for peanut butter, meat, or fish pastes..

Ultrasonic Homogenizers

Use high-frequency sound waves (18–30 kHz) to cause compression and cavitation of air bubbles.
Produce emulsions with droplet sizes of 1–2 μm.
Commonly used for salad creams, baby foods, and essential oil emulsions.

Hydroshear Homogenizers and Microfluidizers

Hydroshear homogenizers create shear by spinning liquid in increasingly smaller circles.
Microfluidisers pump fluids into chambers, generating shear and turbulence.
Produce droplets smaller than 1 μm.

Effect of Homogenization on Foods

Affects the mouthfeel and texture of liquid and semi-liquid foods.
Reduces fat globules in milk, providing a creamier texture.

Dairy Products and Margarine

Butter: Created by churning cream, forming butter grains.
Margarine: A water-in-oil (w/o) emulsion, produced from oils and skim milk emulsified together.
Texture is achieved through fat crystallization during chilling.

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Description

Test your knowledge on the fundamentals of size reduction in food science. This quiz covers the processes involved in comminution, the forces utilized for size reduction, and the effects on food quality. Perfect for students and professionals in the food technology field.