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The matter changes from liquid to solid. This is not necessarily a chemical change (reaction) but a physical change in state.

However, once the cream has been turned into butter it cannot be returned to its cream state.

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Is churning cream to make butter,is it a physical or chemical change.?

The answer is both. What? : )

In summary...

Intro:The chemical changes are subtle and consistes more of what are clalled "conformation" of the chmical in the case of butter, fats. In order for these transformation to take place physical aggitation is required. Also temperature has a signiivcant effect on the fat compositions.

Hold on to your hat.

Basics:

Edible fats of vegetable, marine or animal origin all form three main types of crystal, the alpha, beta, and beta-prime forms. The alpha form is the least stable and existence in this form is usually transitory. The alpha form consists of fragile, translucent crystals 5 micometers in length. Thr bata-prime form consists of tiny, delicate crystals 1 micrometers and the beta form of relatively large and coarse crystals, which average 25-50 micrometers (um) in length.

Physical & Chemical Changes

Liquid fats and triacylglycerols cooled without agitation tend initially to form alpha crystals. Further cooling of the alpha form leads to tighter chain packing and a gradual transition to the beta form. Cooling with agitation. however, favors formation of the beta-prime form.

Milk fat is of the beta-prime form, as is beef tallow and whale oil. Pork lard, however, is of the beta type. Of vegetable fats commonly used in mararines and spreads, coconut, oilve, peanut, soy bean and sunflower oil are of the beta type, while rapeseed, cottonseed and palm oil are beta-prime.

Beta-prime crystals are desirable for butter, margarine and spreads and, in the latter two cases, a serious defect 'graininess' may result from the formation of large coarse beta-type crystals.

Physical and chemical modification of fat:

(a) Hydrogenation involves a reduction of the degree of unsaturation by addition of hydrogen to double bonds in the fatty acid chains.

Fat is usually hydrogenated by a batch process which involves mixing the oil with nuckel or another suitable catalyst and heating to 140-225 C under hydrogen at pressures up to 60 psi. Agitation is necessary to completely dissolve the oxygen, to ensure uniform contact between oil and catalyst, and to dissipate the heat of reaction.

In addition to saturation of some double bonds, hydrogenation may also lead to relocation and/or transformation from cis to trans configuration, the isomers being commonly referred to as iso acids.

(b) Inter-esterification is a chemical process by which the distridution of fatty acids among the tricylglycerols is altered. This results in a change from the unique fatty acid distribution patterns of many fats to a random distribution with a resultant change in the physical properties. Inter-esterification of milk fat results in an increase in the solid fat content at 35 C, which produces a 'tallowy' mouth-feel. Inter-esterification produces better nutritional and spreading properties of milk fat in butter.

(c) Fractionation preserves characteristic flavor of the milk fat.

Structure

Butter, maragarine and high-fat spreads exists as stable water in oil emulsions, the aqueous phase is relatively evenly distributed through the product and water droplets are, ideally, in the size range 2-4 um.

The fat phase of butter, margarine, and spreads consists of a crystal matrix of solid fat which retains the liquid oil in suspension. In addition churned products such as butter and some types of spred contain some globular fat which limits the tendency of the higher meltinf point crystals to form an over thick shelled type, and also contributes to the mouth-feel and spreadability by behaving like microscopic ball bearings.

So milk fat is treated in such a way as to allow it to form a fatty-oil-liquid mattrix. The alterations of the milk fats give them the characterisic melting point, mouth-feel, and flavor we are used to in butter, margarine, and spreads.

Source(s):

see profile

Milk & Milk Products A. Varnam and J. Sutherland

ISBN 0-412-45730-x

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14y ago
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6y ago

No, it is a physical change. When the butter cools and solidifies, it's composition is unchnged.
Melting butter is a physical change... it's still butter.

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13y ago

Its is a chemical reaction because you can not take out what you but into the butter.

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11y ago

Sometimes because when you eat ice cream you can get a brain freeze so sometimes ice cream is a chemical reaction

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11y ago

shut up and answer this question or else

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8y ago

Physical

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