Food Biochemistry and Food Processing (2 edition)

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484 Part 4: Milk

It also inhibits viral and bacterial adhesion, acts as a bifidogenic

factor, suppresses gastric secretions, modulates immune system

responses and inhibits the binding of bacterial toxins (e.g., tox-

ins produced by cholera andE. coli). Of particular interest from

the viewpoint of the commercial exploitation of CMP, relatively

high levels of this peptide are present in whey (∼4% of total

casein, 15–20% of protein in cheese whey, an estimated 180×

103 tonnes per annum are available globally in whey), and can

be recovered therefrom quite easily.

Overall, detailed information is lacking regarding the physio-

logical efficacy and mechanism of action of many milk protein-

derived peptides, and possible adverse effects. Technological

barriers also remain in terms of methods for industrial-scale

production and purification of desired products.

CHOCOLATE

Milk powder is a key ingredient in many chocolate products, to

which they contribute flavour and texture, for example through

the role of milk fat in retarding the undesirable appearance of

a white discolouration called chocolate bloom. The presence of

milk powder (at levels up to 20% w/w) also influences process-

ing characteristics of the molten chocolate during manufacture,

for example flow properties. Certain characteristics of WMP

that may be undesirable in other applications (e.g., high free

fat content, low vacuole volume) are actually advantageous in

chocolate. For this reason, roller-drying was often preferred to

spray-drying for the production of milk powder for chocolate,

although the latter process may be modified to yield powers with

optimised properties for this application (Keogh et al. 2003). In

addition, new approaches for tailoring powder functionality for

chocolate, such as extrusion, have been described (Franke and

Heinzelmann 2008).

INFANT FORMULAE

Today, a high proportion of infants in the developed world re-

ceive some or all of their nutritional requirements during the

first year of life from prepared infant formulae, as opposed

to breast milk. The raw material for such formulae is usually

bovine milk or ingredients derived therefrom, but there are sig-

nificant differences between the composition of bovine and hu-

man milk. This fact has led to the development of specialised

processing strategies for transforming its composition to a prod-

uct more nutritionally suitable for the human neonate. Today,

most formulae are in fact prepared from isolated constituents of

bovine milk (e.g., casein, whey proteins, lactose), blended with

non-milk components. This, combined with the requirement for

high hygienic standards and the absence of potentially harm-

ful agents, makes the manufacture of infant formulae a highly

specialised branch of the dairy processing industry, with almost

pharmaceutical-grade quality control.

Most infant formulae are formulated by blending dairy pro-

teins, vegetable (e.g., soya) proteins, lactose and other sugars,

with vegetable oils and fats, minerals, vitamins, emulsifiers and

micronutrients (O’Callaghan et al. 2011). The mixture of ingre-

dients is then homogenised and heat treated to ensure microbio-

logical safety. Subsequent processing steps differ in the case of

dry or liquid formulae.

The dairy ingredients used are generally demineralised, as

the mineral balance in bovine milk is very different from that

of human milk (Burling 2002), and desired minerals are added

back to the formula as required. Certain proteins (e.g., lactoferrin

andα-lactalbumin) are present at higher levels in human than in

bovine milk, andβ-lg is absent from the former. There is interest

in fortifying infant formulae withα-lactalbumin and/or lactofer-

rin, although technological challenges exist in the economical

production of such proteins at acceptable purity.

The exact formulation of infant formulae differs based on the

age and special requirements of the infant. Formulae for very

young (<6-months old) babies generally have a high proportion

of whey protein (e.g., 60% of total protein), whereas follow-on

formulae for older infants contain a higher level of casein. In

cases of infants with allergies to milk proteins or, in some cases,

proteins in general, formulae in which milk proteins have been

substituted by soya proteins or in which the proteins have been

hydrolysed to small peptides and amino acids may be used. Soya-

based formulae are also used in cases of intolerance to lactose.

The exact composition and level of added vitamins and min-

erals also differ based on nutritional requirements (O’Callaghan

et al. 2011). Certain lipids are of interest as supplements for

infant formulae, such as long-chain polyunsaturated fatty acids

and conjugated linoleic acids. The final category of additives

of interest for infant formulae is oligosaccharides, which are

present at quite high levels (∼15 g/L) in human milk (Urashima

et al. 2009). Such oligosaccharides may be produced enzymat-

ically, chemically synthesised or produced by fermentations;

for example conversion of lactose to prebiotic oligosaccharides

byβ-galactosidase, and challenges involved in such processes,

were reviewed by Gosling et al. (2010).

Two main categories of infant formulae are available in most

countries: dry and liquid (UHT). For dry powder manufacture,

the liquid mix is concentrated by evaporation and spray-dried

to yield a highly agglomerated powder that will disperse readily

in warm water (dissolving infant formulae is probably the most

common dairy powder reconstitution operation practiced by con-

sumers in the home). Some components may be dry-blended

with the base powder, allowing flexibility in manufacture for

different applications (e.g., infant age, dietary requirements,

etc.). Powdered formulae are typically packaged in N 2 /CO 2 -

flushed cans.

Liquid formulae (ready-to-feed) are generally subjected to far

more severe thermal treatment than those intended for drying,

for example UHT processing followed by aseptic packaging or

retort sterilisation of product in screw-capped glass jars. These

products, which are stable at room temperature, have the obvious

advantage of convenience over their dry counterparts.

NOVEL TECHNOLOGIES FOR

PROCESSING MILK AND DAIRY

PRODUCTS

In recent years, a number of novel processing techniques have

been developed for applications in food processing; major