Dairy Ingredients for Food Processing

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Chapter 5

Concentrated Fluid Milk Ingredients

Nana Y. Farkye and Shakeel ur - Rehman

Introduction

Concentrated fl uid milk products can broadly
be defi ned as liquid or fl uid milk that has had
its composition altered from its normal,
natural state by techniques such as evapora-
tion, condensing, and membrane processing
(e.g., ultrafi ltration [UF], reverse osmosis
[RO], nanofi ltration [NF], microfi ltration
[MF], or combinations thereof). The resultant
fl uid milk product usually has higher total
solids than normal milk but the concentra-
tions of its components differ.
Concentrated milk offers economy,
reduced transportation costs, convenience,
added utility, and functionality (nutrient
dense) to producers, processors, and consum-
ers. For example, milk may be concentrated
3 : 1 fold on the farm prior to shipping to a
milk processing factory, permitting a tanker
to haul 3 times the original milk volume/
weight for the same cost. The highest practi-
cal concentration for milk to be sold as fl uid
milk is 3 : 1 on a volume basis. At this con-
centration, the lactose content is approxi-
mately 13.1%, which is equivalent to 19.9 g
lactose/100 g water, making lactose saturated
at 21 ° C; it may be supersaturated at refriger-
ated temperatures. Hence, higher concentra-
tion levels may result in lactose crystallization.
At a 3 : 1 concentration, 946.38 ml (1 quart)

of concentrated milk testing 9.92% fat and

24.10% solids - not - fat (SNF) (34.02% total

solids, TS), and weighing 2.275 lbs upon

addition of approximately 1.9 L (2 quarts) of

water yields 3 quarts of reconstituted milk

testing 3.5% fat and 8.5% SNF.

Composition of Liquid or Fluid

Milk and Market Milk

Milk is defi ned by the Code of Federal

Regulations (21CFR 131 : 110) as a lacteal

secretion from complete milking of one of

more healthy cows, containing at least 3.25%

fat and at least 8.25% SNF. Physical fraction-

ation of milk resulting in removal of water or

altering the relative concentrations of milk

components to increase TS content results in

a product that is broadly defi ned as “ concen-

trated fl uid milk ” in this chapter. The reader

must be aware of the legal defi nition of con-

centrated milk as defi ned in the Code of

Federal Regulations (21CFR131.115).

Changes Caused by

Concentrating Milk

In addition to the increase in solute concen-

trations that results from concentration of

milk due to removal of water, other changes

occur in milk. Walstra et al. (1999) list the

following changes that result from concen-

trating milk:

1. Decrease in water activity (e.g., water
   activity of milk is 0.993 compared to
   0.986 for evaporated milk).

Dairy Ingredients for Food Processing edited by
Ramesh C. Chandan and Arun Kilara
© 2011 Blackwell Publishing Ltd.