Dairy Processing: Exam 2

What is homogenization?

Breaking fat globules into smaller droplets to prevent creaming.

Why must fat be liquid during homogenization?

So fat globules can be broken into smaller droplets.

What are the purposes of the first and second homogenization stages?

First: breaks fat globules smaller. Second: breaks up clusters.

What are the benefits of homogenization?

Prevents cream separation and improves appearance and texture.

What are the drawbacks of homogenization?

Can increase lipolysis and oxidation and weaken cheese curd.

What vitamins are used to fortify milk?

Vitamins A and D.

Why is milk fortified?

To improve nutritional value.

What is thermalization?

Mild heating before pasteurization to reduce microbes.

Why doesn't thermalization replace pasteurization?

It does not provide enough pathogen destruction.

What is pasteurization?

Heating milk to destroy disease-causing microorganisms.

What is batch pasteurization?

Heating milk in a tank for a set time.

What is HTST?

High-Temperature, Short-Time.

What is UHT processing?

Very high heat for a short time followed by aseptic packaging.

What is sterilization after packaging?

Heating the product after it is sealed in its container.

Why do high-fat or sweetened products need different heat conditions?

Their composition can change heat transfer and microbial heat resistance.

What can limit shelf life after pasteurization?

Spores, heat-resistant microbes, surviving enzymes, and later contamination.

What is counter-current heat exchange?

Two fluids flow in opposite directions to transfer heat.

What is regeneration?

Using heat from pasteurized milk to warm incoming raw milk.

Why is regeneration useful?

It saves energy.

Why is pressure higher on the pasteurized side?

To help prevent raw milk from entering pasteurized milk.

What does the flow diversion device do?

Redirects milk that does not meet required conditions.

Where does inadequately treated milk go?

Back for proper treatment.

What should the alkaline phosphatase test show after conventional pasteurization?

Negative.

What should the peroxidase test generally show after conventional pasteurization?

Positive.

What can a positive phosphatase test indicate? *

Inadequate pasteurization or raw milk contamination.

What can a negative peroxidase test indicate?

More intense heating.

What does lipoprotein lipase do?

Breaks down milk fat and can cause rancid flavors.

What does plasmin do?

Breaks down milk proteins, especially casein.

How does heat affect dissolved gases and minerals?

It can remove gases and change mineral balance.

How does heat affect whey proteins?

It can unfold or denature them.

What can whey proteins interact with after heating?

Kappa-casein.

What is the Maillard reaction?

A reaction between proteins and lactose that causes browning.

What can prolonged heating cause?

Browning, cooked flavors, and reduced available lysine.

What are vegetative cells?

Actively growing bacterial cells that are generally heat-sensitive.

What are bacterial spores?

Dormant structures that are more heat-resistant.

How does fat affect microbial heat resistance?

Fat can protect microorganisms from heat.

How does pH affect microbial heat resistance?

Acidity generally makes microorganisms more heat-sensitive.

What is quality assurance?

An ongoing system that maintains product quality and safety.

What does fit for use mean?

Suitable for its intended purpose.

What is total quality management?

An organization-wide approach to maintaining and improving quality.

What is the difference between cleaning and sanitation?

Cleaning removes soil; sanitation reduces microorganisms.

What do chlorinated alkaline cleaners remove?

Organic residues such as fat and protein.

What do acid cleaners remove?

Mineral deposits and milkstone.

What do sanitizers do?

Reduce microorganisms on cleaned surfaces.

What employee hygiene practices are important?

Hand hygiene, clean gloves, hair restraints, beard restraints, and clean footwear.

Why is post-processing contamination dangerous?

It can reintroduce microbes after the bactericidal step.

What is HACCP?

Hazard Analysis and Critical Control Points.

What is the purpose of HACCP?

Preventing food-safety hazards.

What was NASA's role in HACCP?

Helped develop a preventive food-safety system for astronaut food.

Why does each product need an appropriate HACCP plan?

Different products and processes have different hazards.

What are the three food-safety hazards?

Biological, chemical, and physical.

What is a biological hazard?

A harmful microorganism.

What is a chemical hazard?

An unwanted chemical contaminant.

What is a physical hazard?

A foreign object such as glass or metal.

What is a CCP?

A step where a food-safety hazard can be controlled.

What is a critical limit?

A measurable boundary that must be met at a CCP.

What are three examples of a critical limit?

Time, temperature, humidity

What is monitoring?

Regularly checking whether a CCP meets its limits.

What are corrective actions?

Steps taken when a critical limit is not met.

What is verification?

Checking that the HACCP system works correctly.

Why are HACCP records important?

They document hazards, monitoring, corrections, and verification.

What is the target hazard in HTST pasteurization?

Disease-causing microorganisms in milk.

What is the CCP in HTST processing?

The pasteurization step.

What are the HTST critical limits?

Required minimum temperature and holding time.

What happens if HTST conditions are not met?

Milk is diverted for proper treatment.

What does MSNF stand for?

Milk Solids Nonfat.

What are the major components of MSNF?

Protein, lactose, and minerals.

What are the main components of ice cream?

Milk fat, MSNF, water, air, and sweeteners.

What does egg yolk add to French-style ice cream?

Egg yolk is part of the custard-style formulation.

What does water do in ice cream?

Forms ice crystals.

What does air do in ice cream?

Adds volume and creates a lighter texture.

What does milk fat do in ice cream?

Adds richness, flavor, and body.

What do sweeteners do in ice cream?

Add sweetness and lower the freezing point.

Why can excess MSNF cause sandy texture?

Lactose can crystallize.

What is a stabilizer?

An ingredient that binds water and limits ice-crystal growth.

What is an emulsifier?

An ingredient that helps control fat structure and air-cell stability.

What is the ice cream processing order?

Blend, pasteurize, homogenize, age, flavor, freeze, add inclusions, package, harden, store.

Why are ice cream ingredients blended thoroughly?

To distribute ingredients evenly and prevent clumps.

Why is ice cream mix homogenized warm?

To keep fat liquid so it can form smaller droplets.

What is aging in ice cream processing?

Holding the mix cold before freezing.

What happens during aging?

Fat partially crystallizes; proteins and stabilizers hydrate.

Why is aging important?

It improves whipping and air incorporation.

When are solid inclusions added?

Near the end of freezing or during filling.

What are the two objectives of freezing ice cream?

Form ice crystals and incorporate air.

Why is ice cream an emulsion?

It contains fat droplets dispersed in a water-based mix.

Why is ice cream a foam?

It contains air bubbles dispersed throughout the product.

What helps stabilize air bubbles in ice cream?

Partially coalesced fat.

What is overrun?

The percentage increase in volume from incorporated air.

How does more air affect ice cream?

Increases volume and makes the product lighter.

What is the overrun equation?

(Final volume − starting mix volume) ÷ starting mix volume × 100.

What is dynamic freezing?

Freezing and agitating ice cream mix in a barrel.

What is static hardening?

Rapidly freezing packaged ice cream without agitation.

Why is rapid hardening important?

It creates smaller ice crystals.

What is forced-air freezing?

Using moving cold air to remove heat.

What is plate freezing?

Using cold plates to remove heat through contact.

Why does some water remain unfrozen?

Dissolved ingredients lower the freezing point.

What causes icy texture?

Large ice crystals, often from temperature fluctuations.

What causes sandy texture?

Lactose crystallization from excessive MSNF.

What causes ice cream meltdown?

Ice melting and collapse of the air-cell structure.

What is cheese?

A dairy product made by coagulating milk and separating curds from whey.