Condensed Milk

Chemistry of Paneer Preparation

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• Concentration - condensed milk is usually done by evaporation.
• A falling-film evaporator is generally used to remove the bulk of the water and a circulation evaporator to remove the remainder.
• Relatively high temperatures (up to 80°C) are often applied, which implies a lower viscosity in the evaporator but a higher initial viscosity of the final cooled product.
• The low water content of the sweetened condensed milk implies a high viscosity and boiling point. Evaporation in continuously operating equipment with many effects is, therefore, not easy. Fouling, thus, readily occurs. It is difficult to accurately adjust the desired water content, which is mostly monitored by means of refractive index.

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Striking” refers to the drawing of a sample from the pan and testing it for density.

• The density tests that have been found most practical for use at the pan are
• (1) Judging Density by appearance to eye
• (2) The Picnometer test and
• (3) The Hydrometer test.
• (4) Refractometer test
• (5) Viscometer test.

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Carrageenan is an additive used to thicken, emulsify, and preserve foods and drinks. It's a natural ingredient that comes from red seaweed (also called Irish moss). You'll often find this ingredient in nut milks, meat products, and yogurt.

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Cooling of Sweetened Condensed Milk:

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• It is one of the important steps in manufacture of sweetened condensed milk.
• It is absolutely essential to cool the product promptly to desired temperature because formation of large lactose crystals must be avoided. Consequently, seed lactose is added. Before that, the condensed milk must be cooled to a temperature at which lactose is supersaturated so that the seed lactose does not dissolve. However, the temperature must not be so low that spontaneous nucleation can occur before the seed crystals are mixed in. After seeding, cooling should be continued to crystallize the lactose.

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If we do not cool down quickly

(1) There is tendency of discoloring and

(2) Tendency of age thickening during storage.

Cooling will also help in

(1) Formation of smoother texture in finished product and

(2) Prevent objectionable sugar deposit.

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Crystallization�

• The relative smoothness of product will largely depend upon number and size of crystals present.
• Our main aim is not to prevent the formation of crystals but our main aim is to form more crystals having smaller size.
• In this process major constituent responsible is lactose because it has low solubility than sucrose.
• Also crystals formed are hard and thick. In case of sweetened condensed milk, the rate of lactose crystallization is further impeded (retarded) by

(1) The milk colloids and

(2) The higher viscosity which reduces the rate of diffusion.

Lactose is a disaccharide and reducing sugar. It is not very soluble and not so much sweet as sucrose. It is fermented by lactic and acidophilus organisms etc. The concentration of this sugar varies from 48-50 gm/liter. In solution, lactose exists in two forms i.e. α & β forms.

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Purpose of seeding

• The purpose of seeding is to give the lactose present in super saturation form an additional incentive for crystallization.
• When condensed milk at optimum temperature is seeded with properly prepared lactose in presence of vigorous agitation, numerous crystals of lactose of uniform size will be formed. This operation should be continued for about one hour. The number of crystals centers present at any time, that are capable of developing successively to crystal nuclei and to crystal is a function of degree of super saturation and that the existing crystal centers will increase with the degree of super saturation. In the absence of crystal nucl ei, or because of difficulty of migration of particles to existing nuclei, lactose even in highly super-saturated solution may refuse to crystallize or will crystallize only very slowly.

The seed material commonly used is powder of lactose hydrated.