Aerated Food Product

8/17/2019 Aerated Food Product

1/22

Aerated Food ProductThe results of food aeration are:

i. a reduction in the density of the product;

ii. a change in the texture and rheology of theproduct, giving a different mouthfeel andappearance;

iii.enhanced ability to take up sauces, due toincreased surface area;

iv. modification of digestibility;v. the possibility of a reduced shelf-life, as the finely

divided air bubbles or increased porosity mayenhance oxidation reactions and affect fat andflavour ingredients;

vi. a decrease in the intensity of flavours


2/22

Classification of aerated foods

i) Beverages: beer, sparkling wine, carbonatedsoft drinks;

ii) Baked products: breads, cakes, pastries,croissants, biscuits, crackers, crumpets, voi auvents;

iii) Other cereal-based products: including

extruded and expanded products, breakfastcereals, snacks, popcorn;

iv) Dairy products: whipped cream, ice cream,dairy desserts, milkshakes, butter, cheese;

Aerated Food Product


3/22

i) Egg products: meringue, soufflé, fluffyomelettes;

ii)Chocolate and confectionery products:

aerated chocolate bars, crispy bars,marshmallow, nougat, pulled taffy, foamedsweets;

iii)Others, including, for example, unusualpart- or fully-processed products such asaerated meat foams or vegetable paste

foams, fruit fools, sorbets.



4/22

Aerated Food ProductMethods used to aerate foods:

Fermentation, in which aeration is achieved due to carbondioxide production by yeast in, for example, bread, beer andwine. This CO2 diffuses into existing bubbles, either entrained

during dough mixing, or attached to particles within the beeror wine

Whipping or shaking of low-medium viscosity liquids toentrap air (e.g. whipped cream, beaten egg whites, cakebatter, milk shakes, frappés). Fat crystals aid incorporation ofair into cake batters and ice cream. During whipping orshaking, bubbles rise and disengage from the liquid, so thatthe air content and bubble size distribution depend on therelative rates of entrainment and disentrainment.


5/22

Aerated Food ProductMixing of doughs or high viscosity pastes, in

which air bubbles are entrapped as surfaces cometogether. The high viscosity of the dough or pasteprevents rising and disengagement of bubbles,

although as with whipping and shaking,disentrainment of air occurs simultaneously withentrainment as new surface is created. In raised

bread, the bubbles incorporated by mixing act asnucleation sites for the CO2 produced duringfermentation. During creaming of butter and sugar,sugar crystals aid aeration.


6/22


Steam generation during slow to moderatecooking, baking or frying (e.g. crumpets, pikelets,doughnuts, waffies, most unleavened bakedgoods). Steam generation is often accompanied by

thermal expansion of the gases already in thebubbles, and by evaporation of other dissolvedcomponents (e.g. CO2, ethanol). Oven spring

during baking, concluded that evaporation of watercontributes more than half of the volumeexpansion, the rest being due to thermal expansion

and CO2 coming out of solution


7/22


Entrapment of air between sheeted layers, as inpastries and croissants.

Frying in very hot oil, such that internal steam is

formed rapidly, causing the product to puff.The use of chemical raising agents such as bakingpowders in cakes, or sodium bicarbonate in soda

breads.

Rapid dry heating of small or thin products toinduce blistering (e.g. of potato crisps or corn flakes)

or slight puffing (e.g. micronization of wheat orlegumes to enhance hydration or digestibility)


8/22


Gas injection, e.g. air or nitrogen injection in ice cream andsugar confectionery, carbon dioxide injection in soft drinks andnitrous oxide injection in instant whipped cream

Expansion extrusion, in which superheated product underpressure emerges suddenly from an extruder, such thatmoisture immediately vaporises, to produce crisp snacks,cereals and sugar confectionery.

Pressure beating (dissolution of air or gas under pressure),for example, in a syrup, fat mixture or chocolate, for

confectionery manufacture. Pressure beating gives a very finefood foam.


9/22


Puffing, in which products such as breakfast cereals containingsuperheated moisture are subjected to a sudden release ofpressure.

Vacuum expansion, followed by rapid cooling to set the

expanded product, e.g. chocolate bars.

Special cases, such as the use of a hot plate or microwaveoven to cook and expand popcorn, or mixing bread dough with

carbonated water under pressure to generate aeration withoutleavening, or initiation of carbon dioxide bubble nucleation bywidgets in canned beer, or the frothing of Cappuccino coffee bysteam injection, or freeze drying to produce porous coffee

particles.


10/22


11/22


Aerated systems are thermodynamically unstable. Stabilityis primarily affected by the rheology of the system


12/22


Bubbles are stabilized by surface activeagents (proteins, emulsifiers), solid crystals offat (as in whipped cream) or ice (as in icecream) in a viscous liquid phase, or by a semi-solid or solidified continuous matrix.

Gelatin is widely used to set the continuous

matrix of aerated food foams. Whey proteins,-Lactoglobulin, are well characterised interms of their contribution to the formationand stability of foamed food products.


13/22


In other cases stabilisation mechanisms act

consecutively, e.g. in cake making, the high viscosity ofthe creamed butter and sugar retains the entrainedbubbles, but during baking these bubbles are stabilised bythe egg protein

Often a combination of stabilisation mechanisms acttogether; for example, in bread dough proving, theviscoelastic protein matrix stabilises bubbles againstcoalescence, but added surfactants can give slightly extra

stability and an even greater loaf volume, while fat crystalscontribute to stability during baking.


14/22


Proteins and emulsifiers (small fatty acids chain) areboth surface active, reducing the surface tension at aninterface and so alleviating the thermodynamic

tendency to minimise the interfacial area.A mixed system of protein and surfactant can be unstable, as thesurfactant dilutes the proteins and prevents their interlinking, whilethe proteins interfere with rapid surface diffusion of the emulsifier.Lipid material generally can have this effect on protein-stabilisedfoams.

It is for this reason that when beating egg whites, it is

imperative that not even the smallest speck of the fatty yolk gets into the bowl


15/22

Table 2. Stabilisation mechanisms for aerated foods produced by different methods. Note that different aeration methods or

stabilisation

mechanisms may contribute at different points within a process

Aeration method liquid forced around extemal gas Gas forced though liquid In situ generation and/or

(whipping, shaking, (sparging) expansion of gas (steam, CO2,

dough mixing, layering) thermal expansion,

vacuum expansion)

Stabilisation mechanism

Proteins Milkshakes, soufflé, zabaglione, Widgets in beer, Beer foam, wine foam,

marshmallow, egg foams carbonated drinks, carbonated drinks,

Cappuccino proving bread dough,

sponge cake, angel cake,

soufflé

Fat crystals Whipped cream, puff pastry Instant whipped cream

Ice crystals Ice crea m, frozen desserts

High viscosity/semi-solid Batters, bread dough, pastries, Pikelets, pancakes,

cake batters, creamed butter baked goods,

and sugar, dairy desserts, Swiss cheese, gums

50ft butter, peanut butter,

meat doughs, fruit fool,

sorbet, fondant,

Yorkshire pudding

Solid matrix

Starch Bread, crackers, crumpets, Bread, crackers, crumpets,

cakes, waffles, pasì'ries, cakes, waffles, crispbreads,

poppadoms snacks, potato crisps,

cornflakes, breakfast cereals,

popcorn, pastries, poppadoms

Sugar Meringue, taffy Honeycomb, boiled sweets

Fat Chocolate bars Chocolate bars


16/22

Experimental techniques for studying aerated foods

1. food quality (rheology, texture, appearance);

2. foam behaviour (foamability, foam stability);

3. gas phase characteristics (air content, bubble sizedistribution, individual bubble behaviour).


For solid or more viscous foods, rheological andtextural measurements are predominant, the latteroften by sensory evaluation.


17/22

For the more fiuid food foams, foamability (the easewith which a foam is formed) and foam stability areof primary importance.

Foamability may be measured by sparging gas todetermine the time required to form a prescribedvolume of foam.

Foam stability may be characterised by the half-life of the foam, the rate of drainage or the rate ofchange of conductivity.



18/22

Air content is a primary parameter of aerated foods, but is

not easily determined. If the gas phase is continuous, aircontent may be termed porosity.

Air content can be calculated from the density or specific

volume, but this requires that the gas-free density beknown, and this can be difficult to determine.

More accessible parameters such as density, specificvolume and overrun are therefore more usually reported.



19/22


( )100

/

//×

⋅⋅⋅⋅⋅⋅−⋅⋅⋅

=volume product whipped of weight

volume product whipped of weight volume product unwhipped of weight overrun

1001001001 ×⎟ ⎠

⎞

⎜⎝

⎛

+=×⎟⎟ ⎠

⎞

⎜⎜⎝

⎛

−= OROR

gf ρ

ρ

α

100100

1001 ×⎟ ⎠ ⎞⎜

⎝ ⎛

−=×⎟⎟

⎠ ⎞⎜⎜

⎝ ⎛ −=

α

α

ρ

ρ gf OR

ρ= density; ρgf =gas-free density; α=void fraction


20/22


The expansion of extruded products is often char-acterised by the expansion ratio, E, the ratio of extrudate diameter to die diameter. The expansior ratio istypically in the range 1.5~3.0, indicating a radial

increase in volume of 2~9 times. However there isalso significant longitudinal expansion, such that thetotal increase in volume can be by a factor as highas 10, giving air contents of up to 90%


21/22

Table 3. Typical values of p arameters r elated to air content o f aerated foods (dependant in ali cases on temperature, composition and

processing factors)

Food Density Gas-free density Specific volume Overrun/specific Void fraction

(g/cm3) (g/cm3) (cm3/g) volumetric air contenti of air (%)

additional air added (%)

Popcom 14 > 1900 >95

Rice cakes 0.11-0.13 1.35-1.40 7.5-9 950-1150 90-92Puffed rice 0.13-0.17 1.35-1.40 6-8 700-950 88-90

Extruded products 0.10-0.33 1.25-1.40 3-10 300-900 75-90

Meringue 0.17-0.18 155 5.5-6.0 750-800 88-90Beaten egg whites 0.15-0.20 1.04 5.0-65 500-600 80-85

Baked loaf 0.20-035 1.25 3.0-5.0 250-550 72-85

Sponge cake 0.25-035 1.25 3.0-4.0 230-400 70-80

Risen dough 0.25-0.40 1.25 2.5-4.0 200-400 68-80

Marshmallow 035-0.45 1.4 2.2-2.9 200-300 68-75

Cake 035-0.40 1.25 2.5-3.0 200-250 68-72

Whipped cream 0.40-0.60 1.01 1.7-2.5 70-150 40-60

Ice crea m (hard) 054-0.55 1.09-1.10 1.8-1.85 100 50

Cake batter 0.55-0.80 1.15 1.25-1.8 40-100 30-50

Aerated chocolate bar 0.70-0.80 1.30-1.35 1.25-1.45 65-80 40-45 Nougat 0.80-0.90 1.3 1.1-1.25 40-65 30-40

Fruit fool 0.75-0.8 1.05-1.07 1.25-1.35 32-40 25-30

Ice cream (soft) 0.78-0.8 1.09-1.10 1.26-1.27 40 28

Milkshake 0.90-0.95 1.025-1.035 1.05-1.10 10-15 9-13

Micronized wheat 1.15-1.25 13-1.4 0.8-0.9 75-12 7-11

Bread dough (unrisen) 1.15-1.20 1.25-1.26 0.83-0.87 4-9 4-8

Wheat grains 1.25-135 1.35-1.45 0.75-0.8 2- 3 2- 3


22/22


Aerated Food Product

Documents

Transcript of Aerated Food Product