Fats & Oils in Food Preparation

8/9/2019 Fats & Oils in Food Preparation

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HTF573


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Extraction Lipids must be removed from their natural food

sources

Rendering; remove fat from animal tissues by dryor moist heat. (lard & tallow)x Dry rendering; heating the tissue & collect the melted

fat, then expressed by squeezing the residue

x Wet rendering; for human consumption, putting the

tissues in hot water/steam & some pressure fluid fatthen separated from water adding antioxidant

Plant lipids are removed by hot/cold pressing.


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Extractionx Cold pressing; mechanical pressing of olives to express

oil without heat, resulting in an oil excellent purity

x Hot pressing; using steam or hot water to heat plantseeds to about 70C to facilitate extraction of lipids from

the seeds, a process that also extract same gums, off-

flavor and free fatty acids

Other technique; application of CO2

at 8000 psi at

warm temperature.


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Refining Undesirable constituents may be found after

extraction

Compound such as gums, lipoprotein, lecithins,

ketones & aldehydes

Gums & free fatty acids removed by degumming &

neutralization

x Degumming; steam & dilution of phosphoric acid

x Neutralization; a hot steam distillation procedure is

used to separate the volatile FFA from fat molecules


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Refining Bleaching; refinement process that removes

undesirable coloring & flavoring from fat & oil (filtering

through activated charcoal) Deodorizing; using steam distillation to remove low

molecular weight aldehydes, ketones, peroxide,hydrocarbon and FFA that would be detrimental to thearoma & flavor of fat

Winterizing; used to remove lipid fraction with meltingpoint high enough to cause them become solid atrefrigerator temperature. Oil used for salad dressing.


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Controlling Crystal Size The final stage. Careful control the temperature as the

fat is cooling

Appropriate agitation, achieving in smooth fat to formdesired crystals

Confectionary industry, fat undergo tempering to yield

product with crystal shapes (polymorphs)

xRemoving heat resulting from crystallization of fat andmaintaining a selected temperature to promote the formation

of stable, desirable crystals

x To avoid bloom in chocolate product.


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Quality Determinations

Chromatography

analysis

to determine relative amount of key component of

a fat. GLC & HPLC. Detect amount of free fatty

acids

Iodine number FA containing =bond able to take iodine. Indicates

amount of unsaturation in a fat

Peroxide values Oxidation of potassium iodide. Indicates the

deterioration of fat by oxidative rancidity.

Free fatty acids content By titration of fat with standard sodium hydroxide

solution. Detremine FFA. Values for hydrolytic

rancidity.

Standardized testing For testing fat & lipid have been dev. & review by

several group. AOCS, AOAC,CAC & IUPAC


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Hydrogenation Addition of hydrogen to unsaturated fatty acid in

the presence of catalyst (nickel) to reduce the

unsaturation of the molecules & raise the meltingpoint

Occurs on FA with 2 or more = bond

Vege oil can be modified from liquids to solids &extend shelf life

Shortening & margerine

Undesirable results; UFA undergo isomerizationresulting = bond in trans configuration.


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Inter- and Intraesterification Interesterification ; treatment of fat (lard) with

sodium methoxide or another agent to split FA

from glycerols and then to reorganize them on

glycerols to form different fat molecules with less

tendency to for coarse crystals.

x To produce margarine with higher melting point, good

spreading characteristic & ovoid trans FA 2 types; randomized & directed interesterification


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Randomized; Interesterification accomplishedusing melted fat.

Directed; process interesterification in which the

fat is kept below its melting temperature.x To raise the melting point of the fat

Improving the textural characteristic of a fat

Intraesterification; catalyzed reaction in which FAsplit from glycerols and rejoin in different

configuration but with the same FA being retainedin the molecules.x Alters the textural by modifying the crystallization &

crystals agitation


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Oils Available for consumers

E.g. peanut, corn, safflower,

canola, sunflower, olive, coconut Single type or blend of 2 or more

Special oil; macadamia nut, rice

bran oil (oryzanol + tocotrienols)


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Spread Butter

Stick margarine

Soft or tub margarine

Diet margarine

Whipped butter & margarine


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Shortening & lard Essentially all fat

Solid with considerable plasticity

Lard, from pig, grainy texture. Somealteration

Shortening, hydrogenation of vege oilsx Mono & diglycerides added to improve the ability

to form emulsion in batter & dough

xYellow color & butter like flavoring

Beef tallow, solid fat, from cattle. Add toshortening to have crystals. Usually notuse as single source


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Substituting one fat for another For health reason

Butter may need to be replace with other fat

Determine how much should be used to substitute

for the butter

E.g. butter stick margarine tub margarine


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Color Butter contribute to yellow creamy color

Margarine are colored to stimulate the color of

butter

Shortening now have beta carotene added to

provide desire yellow color


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Flavor Richness of flavor

Butter, complex flavor profile contributed by

butyric & FA, lactones, aldehyde & ketones

Most margarine & shortening have synthetic butter

flavor added

Olive oil & lard have distinctive flavor component


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Texture Influenced by fat in different way

Depends on type of food being considered

In pastry, contribute flakiness to bake productx Butter or shortening can be creamed with sugar to obtain fine

cell structure

x The fat is carved out by the sharp sugar crystal to create tinyspace where steam & CO2 collect & expend during baking

Fat in bread dough keep the crumb

and crust soft in comparison with bread

without fat.


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Tenderness Aspect of textural properties

Important in baked product

Depends on ability to interfere with developmentof gluten.x When flour protein become moistened with water &

stirred/beaten, gluten complex develop

x Resulting elastic network, when baked, stretches & set

permanently into the structure Way for fat & oil to interfere by physically

preventing / inhibit contact between water andflour protein


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Tenderness By mixing fat or oil with the flour

so that the lipid coat the surface

of the gluten complex A soft fat or oil can physically be

spread over much largersurface area than firm fat

The ability of a lipid to

accomplish this tenderizingaction is called shorteningpower.


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Emulsification For optimal textural qualities, stable emulsion are

desired

In most food system, type of emulsion is an oil-in-water emulsion (oil dispersed in aqueous phase)

An emulsifying agent need to facilitate the formation of

stable emulsion

x Shortening are formulated with added mono & diglycerides

so that fat & milk in cake batters are emulsified

x They have 1 or 2 hydroxyl group (largely hydrophobic)


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Emulsification May be provided by other food

ingredients

Available in the home is the lecithin inegg yolks

Lecithin; phospholopids

Even the presence of emulsifying

agent, some emulsion break because ofexcessive evaporation of water

Problem in souffles, contain fat from the

flavoring ingredient


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Similar problem found in somegravies

The emulsion can be

reestablished by replacing thewater lost through evaporationduring an extended heating and/orholding period.

A broken emulsion reinforce the

fact that fat & oil do not evaporatewhen they are heated in normalcookery procedures


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Cooking medium Have ability to be heated to temperature

well above the boiling temperature of water

More quickly than done by water, cause

change in texture, flavor & color

Butter & margarine are popular because

pleasing flavor & color. Used is

shallow frying

Oil usually selected for frying


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Can give desired qualities contributed by

fat without contributing such a large

number of calories.

Protein-based replacement

Carbohydrate-based replacement

Fat based replacement


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Fats & Oils in Food Preparation

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