Milk contains many valuable components which can be extracted or utilised to produce butter, cheese, sour cream, yoghurt, milk powders, casein, whey proteins and lactose.



Major Components of Milk

Component Concentration (%W/W)
Fat 3.8 - 6.2

Protein (Casein)

Protein (Whey Proteins)

2.5 - 3.3

0.6 - 0.8

Lactose 4.6 -5.2
Minerals (Ash) 0.7 - 0.8
Water 83.7 - 87.8

PROLIQ is the protein, energy and mineral rich by-product left after the removal of most of the lactose from whey. It has proportionally more protein and minerals than whey on a dry matter basis, resulting from the removal of crystallised lactose. 

PROLIQ contains 6-9 times more solids, and 2-14 times more protein and minerals than whey on a liquid basis (Table 2). 



Major Components of Cheese Whey and PROLIQ

Component (%) Cheese Whey Concentration (%W/W) PROLIQ
Total Solids (%) 5.0 - 7.0 32 - 45

Protein  (%)

0.7 - 0.8

3 -11
Carbohydrate (%) 4.0 - 5.2 17 - 19
Minerals (%) 0.5 - 0.7 9 -10
Other Organic Solids (%) 0.05 7 - 9
Water (%)  93.0 - 95.0 55 - 58

Lactose is extracted primarily from cheese whey. A small proportion of lactic casein whey and permeates may be used at varying stages throughout the milk production season. Lactose crystals are produced after the whey is concentrated and crystalization is allowed to take place. The solid lactose crystals are recovered by centrifuging (spinning) with the liquid (mother liquor) separated and collected at the same time. The mother liquor is then pumped into the available storage tanks. 

Mother liquor quality is measured against a general specification (Table 3). Samples are taken immediately after production, during storage and prior to delivery and measured for total solids, density and lactose. Protein, minerals and vitamins are also reviewed regularly. 



General Specification for PROLIQ

Component Unit Range Measurement Technique
Total Solids % 30 - 42 Vacuum Oven 
Protein % 3 - 11 Kjeldahl (N x 6.3) 
Lactose % 16 - 19 Foss Milkoscan calibrated by Fehlings
Minerals (Ash) % 9 - 12 600°C oven
Calcium  mg/kg  6600 - 8200  ICP-OES 

A range of storage tanks are used across Fonterra. Their sizes range from 30,000 to 3,000,000 litres and are made from concrete, steel or bladder systems. The concrete tanks are coated with a polyurethane surface to protect against corrosion. The steel tanks have a glass surface fused to the steel to provide a permanent protection against corrosion.

Residence times for the PROLIQ in these tanks ranges from a few weeks to six months. PROLIQ is preserved well due to its high salt content and low water activity. PROLIQ can be stored for up to 12 months if maintained through agitation.

Delivery trucks are fitted with pumps to discharge loads between 18,000 - 23,000 litres into the customer's storage facilities. Minimum storage requirement is 30,000 Litres for reordering management


PROLIQ is a slightly acid (pH 5.0-5.2), thick, yellow liquid. At a typical density of 1150 kg/m3 (1.15g/ml), and 30-42% total solids, each 1000 litres contains 483-518 kg of dry matter (DM).

PROLIQ can appear to be thinner at various stages through a season. On investigation, total solids, protein, carbohydrate and mineral levels are normal. The apparent thinning is in part due to the changing nature of the milk proteins. These proteins (perhaps 3-4 in total) have a strong influence on viscosity and their proportions can change over the season. In addition, some fractionation occurs (breaking down of the protein into smaller groups of amino acids or peptides). This can reduce the viscosity but doesn't affect the nutritive value. It is like pre-digestion and could assist in speeding up digestion in the animal. 

Physical separation of PROLIQ can occur under certain conditions. This phenomenon is typified by the appearance of a thin brown liquid (serum) on the surface or as layers within the PROLIQ. In effect, the protein fraction separates from the liquid fraction. Analysis shows that the total mineral content for the two fractions are very similar. However the brown liquid (serum) may be less palatable. Heat, contaminated storage tanks and age are known to contribute to this phenomenon. Remixing by pump or stirrer usually allows normal consumption to resume. 

PROLIQ is corrosive to mild steel and uncoated concrete storage tanks  over time. Timber, fibreglass, plastic and stainless steel are least affected. 

PROLIQ is a milk derived product containing a large range of valuable biological components including essential amino acids, vitamins and carbohydrates. 

Total carbohydrates range from 17-19% consisting mainly of lactose (15-16%) with other sugars accounting for 2-3%. Other organic solids total 7-9% and include lactic acid (mainly existing as calcium lactate which can account for 3-5%) and citric acid. Some fat left in the whey is also included accounting for 1-2% of the total.

The protein fraction (9-11 % ) contains a large range of amino acids in a very balanced composition for stock feed (Table 4). Digestible crude protein averages 210 g/kg OM. This measure also includes a range of water soluble vitamins (Table 5). The fat soluble vitamins (A, D, E, K) are virtually non-existant due to their removal with the milk fats in cheese manufacture. 



Amino Acid Composition of PROLIQ 

(based on 42% total solids and 1150 kg/m3 density)

Amino Acid g/kg OM g/I 
Glutamic Acid 33.0 15.9
Aspartic Acid 19.2 9.3
Leucine 19.2 9.3
Lysine 15.6 7.5
Valine 11.8 5.7
lsoleucine 11.2 5.4
Threonine 11.2 5.4
Serine 10.1 4.9
Histidine 9.8 4.7
Alanine 9.0 4.3
Arginine 6.8 3.3
Phenylalanine 6.7 3.2
Tyrosine 5.5 2.7
Cystine 5.3 2.6
Methionine 5.0 2.4
Glycine 4.1 2.0
Tryptophan 2.8 1.4



Vitamin Content of PROLIQ 

(based on 42% total solids and 1150 kg/m3 density)

Vitamins g/kg OM g/I 
Pantothenic Acid 60 29.0
Riboflavin (B2) 30 14.5
Niacin (Nicotinic Acid) 9 4.3
Thiamine (B1) 4 1.9
Biotin (H) 1 0.5
Cobalamine (B12) 0.1 0.05


Contact us to find out more on how our stock supplement can produce the results you require with your stock.