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level: Ice Cream

Questions and Answers List

level questions: Ice Cream

QuestionAnswer
What are the simple ingredients in ice cream, and then the more in-depthSIMPLE: Ice, cream, flavours, sugar and air IN-DEPTH: proteins, fat, emulsifier, sugar, stabiliser, inclusions, flavour and water
What % of ice cream is air50%. Less air = more premium
What does sugar do to the productLowers the freezing temperature. More sugar = lower freezing temperature (freezing point depression)
Define matrix phaseHolds the ice phase together. Consists of protein, sugars and stabilisers
List the composition of ice cream in terms of volume and energy contributionSee image
What is the point of proteins inside air bubblesStructure-in-structure which stabilises the product
What is the manufacturing process for ice creamMixing (room temperature) -> homogenisation (high pressure) -> Pasteurisation -> Freezing (put air in) -> Extrusion (mould asap) -> Hardening (blast freezer) -> Coating -> Cold store -> Distribution
How does the ice cream freezer workAs a surface heat exchanger with a dasher inside a hollow cylinder
Why are foams (such as ice cream) annoyingUnstable due to density difference. They are like emulsions but just with different densities
What are the name of particles of which stabilise fat droplets in ice cream?Pickering particles
What is the vital role for fat and proteinsHardening stage when the temperature distribution fluctuates. Proteins stabilise and fats crystallize
What are the three foam destabilisation mechanisms (want to avoid these)Disproportionation, coalescence and creaming of bubbles and serum drainage
What are some issues within the ice cream processAeration & freezing (pressure drop, coalescence) -> extrusion (low viscosity, disproportionation) -> Harden and store (temperature, abuse and coalescence) -> Transportation (melting) ->consume
Why do bubbles expand on extrusionDue to Laplace pressure difference
What are some problems when transporting ice creamAs altitude changes, so does pressure, thus changing volume as P1V1 = P2V2
What are some solution to transporting ice creamPressurized transport (expensive) Leave space in tubs (waste of plastic, consumer wont be happy) Put in less air (destroys product) Find a different route (expensive with fuel) Engineer microstructure to be stable to pressure changes
What two things do you want built in stability into the microstructure to ensure the product is stable?Build in stability to coalescence and disproportionation
What is the difference of protein at the surface compared to protein and fat at the surfaceJust protein: low surface elasticity and viscosity gives poor stability Protein and Fat: better bubble stability. High surface elasticity and viscosity and predict improved stability
What are the three methods to make an emulsion stable at the interfaceAdd either proteins, small molecules or mix of both
What is emulsion stability related toType of adsorbed material, where proteins form very stable emulsions. Ideal level of protein can be found experimentally
What are some technical challenges with ice cream (overall challenges with the product)Make and keep small air bubbles, even through storage abuse. Control bubble stability as matrix is changed. Also, to prevent coalescence and disproportionation
How do you reduce coalescenceThicker interfacial area, high solid fat content and gelled continuous phase
Define disproportionationSolubility difference in smaller bubbles and larger bubbles, where the smaller bubbles dissolves into the larger bubbles
How do you reduce disproportionationAttach proteins, crystals, monoglycerides, Pickering particles or a mixture of proteins and monoglycerides to the bubbles surface
Stability of air phase is caused by trapping the structure at what temperature-18 degrees celsius
Define ageingSometimes occurs between pasteurisation and freezing. Allows the product to sit and rest or low speed stirring and cooling at 5 degrees Celsius. Aim is crystallisation of fats, hydration and protein rearrangement