The milk tree – technology and use

Fermented milk-based beverages have enjoyed global appeal for many years while maintaining diverse cultural identities internationally. An increasing appreciation of the tentative relationship between fermenting microorganisms and gut microflora is reflected in the increasing range of fermented milks aimed at promoting a healthier microbiome.

Milk coagulation/precipitation is a central step in the production of a large range of cheese and casein-based products. The curd formed as a result of clotting milk by enzymatic cleavage of the phe-met bond in k-casein is texturised during further processing to generate a multitude of cheese varieties in conjunction with the flavour contribution of fermenting microorganisms.

Alternatively, after such curd is formed from skim milk, successive washing steps leads to the production of dried rennet casein. When acid is used to coagulate milk at its isoelectric pH, the washed and dried curd that results is known as acid casein. Acid casein may be further processed by solubilisation using alkali e.g. NaOH to produce sodium caseinate in spray dried form. Subtle compositional differences in the individual whey streams from these precipitation processes makes facilitate alignment with a choices of next stage process treatments/ingredient applications e.g. acid casein whey as a substrate for the production of high-gelling whey protein concentrates.

Pioneering work on the recovery of protein from whey using membranes is now applied widely to milk separations.

Industrial chromatography takes protein fractionation to a more detailed level. The functionality of these proteins/protein fractions may be further mediated by pre- and post-processing treatments such as heat treatment and/or combination with other ingredients e.g. specific ions and proteins. Enzymatic hydrolysis of proteins using selected enzymes may be used to improve functionality, reduce allergenicity and release targeted peptides.  Retention of bioactivity in selected protein fractions and peptides demands the use of milder processing treatments such as ultra-high pressure processing.