foam --Cooking foam -- Food Foam
foam is a substance that is formed by trapping many gas bubbles
in a liquid or solid. It can be considered a type of colloid.
Culinary foams are best associated with the Chef Ferran Adria from
El Bulli Restaurant in Spain who began experimenting with foams
consisting of natural flavors mixed with a gelling agent such as
agar (see below). The ingredients are then placed in an espuma or
thermo whip where the foam is forced out with nitrous oxide. Food
foams however are not new with soufflés first being seen
at restaurants in France around the late 1700's.
a foam involves the generation of a protein film surrounding a gas
bubble and the packing of gas bubbles into an overall structure.
Destabilization of protein foams occurs due to creaming, drainage
(from lamellae and plateau boarders), bubble coalescence and disproportionation
of the Basic Food Foams
of Liquid and Solid Foams: Beaten Egg Whites, Milk Foams and Whipped
Cream --gas in liquid; and, Marshmallows -- gas in solid)
example of a colloid foam (gas in liquid) used in cooking is egg
white which is a gas dispersed or spread throughout a liquid.
whites are made up of water, protein, and small amounts
of minerals and sugars (see egg
protein composition).. When eggs are beaten, air
is added and the proteins are denatured exposing their
hydrophobic (water hating) and hydrophilic (water
loving) ends of the protein. The proteins align themselves
between air and water forming bubbles with their hydrophilic
chains pointing into the water and dangling their
hydrophobic chains in the air. In addition the proteins
can bond to one another side-to-side as crosslinks
which add to the stability of a foam.
can you stabilize egg white foams?
Copper bowl The copper in a copper bowl assists in creating
a tight bond in reactive sulfur in egg white preventing the sulfurs
from binding other materials. This makes it take longer to form
the foam, but leads to a much more stable foam.
the foam is overbeaten in a non-copper bowl, eventually the proteins
become completely denatured and coagulate into clumps. These clumps
cannot be turned back to smooth peaks. If a copper bowl is used,
fewer protein molecules are free to denature and coagulate, because
of the conalbumin-copper complexes. In addition to forming complexes
with conalbumin, the copper may also react with sulfur-containing
groups on other proteins, further stabilizing the egg white foam.
Cream of Tartar - (potassium bitartrate) is an acidic salt
that can be used to change the pH of the egg white to an acidic
range by boosting the number of free-floating hydrogen ions in the
egg white. This has the effect of stabilizing the foam, and is therefore
an alternative to using a copper bowl. 1/8 teaspoon/0.5g cream of
tartar should be used per one egg white to create this effect. 1/2
teaspoon/2ml of lemon juice can also be used to create the same
3) Sugar -- Sugar is
added during foam preparation because it creates smooth, stable
foam one that will not collapse and drain quickly.
Why fats kill an egg white
Fat molecules also have both
hydrophobic and hydrophilic parts and will compete with proteins
in the hydrophobic/hydrophilic environment. The difference though
is unlike proteins, fats don't bond to each other side-to-side to
form a reinforcing networks instead they will compete with protein
molecules in forming bonds. So, the addition of any fat e.g,, egg
yolks will interfere with the formation of egg white foam. Note:
Once the protein complex is formed
though it is safe to expose fat molecules to it.
AND CREAM FOAMS
is the best type of milk to produce a foam?
in the case of egg white foams it is the protein molecules that
are responsible for milk being able to be foamed. And, as in the
case of egg whites addition of fat will minimize the formation of
foam. Foam stability decreases with increasing fat reaching a minimum
at about 5% and then increases rapidly as fat is increased to 10%.
At this point highly stable cream type foams form. Therefore 'skim
milk' will produce the greatest volume and most stable foams, unless
of course you go very high fat (35%) where whipping cream will also
produce a very stable foam.
does milk foam?
are two different types of proteins in milk: whey proteins and caseins
with caseins making up 80% of the total protein of milk. Casein
imparts good surface-active properties and thus plays a role in
the functional properties of whipping/foaming. Whey proteins although
offering less surface activity than casein, they offer far superior
foam stabilizing properties creating a more rigid film at the air/water
interface of the foam.
Both proteins are stable up to approximately 140F after which they
become susceptible to denaturation. At this temperature new proteins
are needed for stable foam so more milk must be added.
Effect does Temperature Have on Foaming Ability?
fat milk foams best at low temperatures. This also applies to both
whole milk and cream, although to a lesser extent. At temperatures
about 100F, on up through to 160F the trend is reversed with the
higher fat dairy products consistently exhibiting a greater volume
of foam being produced at any given point. In general temperature
trumps the influence of the fat on foaming.
make a culinary Foam?
Foams can produce a lighter feel than a to a thick sauce. 2- They
can provide both a tactile and textural aspects. 3- They can provide
a visual aspect to a dish.
are Foams made?
can "make" foam with a stick blender, but for it to hold, you need
a stabilizer such as agar, gelatin, or lecithin. Many chefs are
currently using the ISI Canisters
to produce a foam. This also requires the presence of a foaming
agent (see below).
AGENTS -- FOAM STABILIZERS:
foaming agents is a surfactant, which when present in small amounts,
facilitates the formation of a foam, or enhances its stability by
inhibiting the coalescence of bubbles (see Foaming Agents -- Wikipedia)
foam stabilizer prevents or retards the coalescence of gas bubbles.
as a foaming agent
is a very efficient foam stabilizer and this property is exploited
in the manufacture of marshmallows. Different gelatins have different
foam stabilizing properties and gelatin for this use needs to be
as a foaming agent
is classified as an amphoteric surfactant in that it can react with
either an acid or a base. It is ideal for converting juices and
watery liquids to airs and foams. To produce a stable foam, start
with a ration of .6% of lecithin.
making wasabi using lecithin foam video
or agar agar as a foaming agent
agar is a polymer made up of subunits of the sugar galactose. Agar
polysaccharides serve as the primary structural support for the
algae's cell walls.Agar is a gelatinous substance derived
from seaweed. Historically and in a modern context, it is chiefly
used as an ingredient in desserts throughout Japan, but in the past
century has found extensive use as a solid substrate to contain
culture medium for microbiological work. The gelling agent is an
unbranched polysaccharide obtained from the cell membranes of some
species of red algae, primarily from the genera Gelidium
and Gracilaria, or seaweed (Sphaerococcus euchema).
Commercially it is derived primarily from Gelidium amansii.
IN FOOD FOAMS
class II hydrophobin (HFBII)
in Culinary Foams has stimulated interest in researching new
substances that would create more stable foams. The class II
hydrophobin (HFBII) is an ultra low molecular weight protein
that is a highly surface-active protein. It has unique functions
as both superior adsorption on a solid surface and ability to
spread on hydrophobic surface. It has been shown to be exceptionally
stable in food foams compared to present stabilizers (Cox et.al.,
paper reports the use of a sucrose surfactant which forms a
coating around the air bubbles, but Bee added that others are
being investigated. "The surfactant has to be able to form a
crystalline layer that adsorbs to the surface," he said.
Polygonal Nanopatterning of Stable Microbubbles Emilie Dressaire,1
Rodney Bee,2 David C. Bell,1 Alex Lips,2 Howard A. Stone1* Micrometer-sized
bubbles are unstable and therefore difficult to make and store
for substantial lengths of time. Short-term stabilization is
achieved by the addition of amphiphilic molecules, which reduce
the driving force for dissolution. When these molecules crystallize
on the air/liquid interface, the lifetime of individual bubbles
may extend over a few months. We demonstrated low gas-fraction
dispersions with mean bubble radii of less than 1 micrometer
and stability lasting more than a year. An insoluble, self-assembled
surfactant layer covers the surface of the microbubbles, which
can result in nanometer-scale hexagonal patterning that we explain
with thermodynamic and molecular models. The elastic response
of the interface arrests the shrinkage of the bubbles. Our study
identifies a route to fabricate highly stable dispersions of
R. Cox, Deborah L. Aldreda and Andrew B. Russell. Exceptional
stability of food foamsnext term using class II hydrophobin
HFBII , Food Hydrocolloids Volume 23, Issue 2, March 2009,
could extend shelf-life on food foams -- Beveragedaily.com
-- Interfacial polygonal nanopatterning of stable microbubbles
to froth milk -- From Coffee geeks site.
-- Molecular Structure