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Milk Proteine Concentrate

Overview

It is easy to appreciate the evolution that has taken place with the traditional glass of milk when we consider the vast array of dairy products available today. Thanks to new technological advancements in the isolation/extraction of milk components, milk can now be "eaten," rehydrated, sliced and even spread. A complete, rich, complex and multifunctional food, milk gives life-sustaining nourishment to newborns babies. This is due in large part to the suspended protein factions, saline, emulsified fat, vitamins and other dissolved matter contained in the aqueous Whey material found in milk.

Ultrafiltration is the preferred method employed to extract milk proteins used in the manufacture of milk protein concentrate (MPC). This concentration process uses varying degrees of pressure to force the liquid matter through a porous membrane. The holes in the membrane are so small (2 to 20 nanometers) that only water, minerals and organic molecules can pass through; the larger-sized proteins are trapped and collected from the membrane. These concentrated milk proteins are then carefully subjected to evaporation and then spray drying. The resulting dry powder is highly sought after for both its nutritional and functional properties, which serve to enhance many finished food products.


Definition

A Milk Protein Concentrate (MPC) is a dairy protein product with a protein content greater than 42% on a dry matter basis. The casein to whey protein ratio is similar to that of the original skim milk; the lactose content in MPC varies according to protein concentration. As such, MPC-42 indicates a protein content of 42% and a lactose content of 46%, while MPC-75 signifies 75% protein and only 10.9% lactose.  In comparison, skim milk powder (SMP) contains around 35% protein and 52% lactose. Although they share similar form and function, MPC and SMP act differently depending on their application. Further processors will choose a type of MPC based on the desired protein level. The particular composition and functional benefits of each type of concentrate will determine its ultimate end use in further processed foods. 


Characteristics

Technological factors that influence the quality of MPC are as follows:

  • Quality of raw milk and operating parameters during heat treatment (pasteurization);
  • Degree of protein concentration (ultrafiltration and diafiltration, lactose washing, used for MPC 65 or greater); (Note: Figures/numbers indicate protein percentage in MPC)
  • Operating parameters when removing water (evaporation and spray drying);
  • Storage conditions of final product (Tmax = 20oC, hermetic packaging).


Appearance

MPC is a fine, white to light cream-coloured powder, uniform in composition and free of lumps. It has a fresh taste with no foreign or off-flavours and a clean, pleasant odour.


Microbiology

The quality of raw milk used to manufacture MPC must meet rigorous standards in terms of composition and microbiological characteristics. Fresh milk is collected according to stringent health and safety regulations and must be free of colostrum and foreign substances such as chemical products or antibiotics. A low somatic-cell content (100-200 000 per cm3) is desirable and helps to avoid a decreased flow during the ultrafiltration process. Milk fat solids are separated from the nonfat milk solids, after which the liquid nonfat material is pasteurized for the first time and is then concentrated by ultrafiltration until the desired protein content is achieved. The dried material is then subjected to a second pasteurization treatment to ensure a clean, innocuous concentrate.

MPC must be free from Salmonella, Staphylococcus aureus, Escherichia coli and other coliforms. MPC-75 must not contain more than 10 000 colony-forming units (CFU) per gram, in terms of total bacteria count, and a maximum count of 50 CFU/g for yeast and mold. The number of microorganisms capable of developing spores under aerobic conditions must not exceed 500CFU/g. Microorganisms capable of sporing under anaerobic conditions must not exceed 700 CFU/g.


Physicochemistry

MPC-75 should register a pH level of 6.8 when dissolved in a 10% solution. Its density should range between 330 and 400 g/L.


Varieties

Thanks to ultrafiltration, the level of protein in MPC can be controlled, making it possible to produce a wide variety of protein concentrates. In general, all these concentrates contain the same casein ratio: amount of serum protein present in the initial raw milk. However, there is a tendency today to produce MPC with a slightly higher casein content.


Composition

Milk proteins are divided into two general classes: caseins and serum proteins.

Caseins are made up of three components (alpha (α), beta (β) and kappa (κ)) and exist in colloidal suspension (micelle) whose diameter varies between 30 and 300 nanometers. Unlike caseins, serum proteins are soluble molecules that appear in the aqueous phase of milk. They are composed of four main components: α-lactalbumin, β-lactoglobulin, seric bovine serum albumen and proteose-peptone. During cheesemaking, caseins are used to form the curd while the serum proteins are found in the aqueous whey (the by-product of cheesemaking).

Although no official federal standards of identity have been developed to address the moisture content in MPC, the current standard applied in the case of commercially dried milk powders (CFR 21, moisture 4%, max) is applied to MPC.


Typical Composition of MPC 75

 Component

 MPC-75

Principal Components (g/100g)

 Protein (Ntotal x 6.38)

 75.0

 Native protein

 73.5

 Non-proteinaceous nitrogen

 1.5

 Lactose

 10.9

 Ash

 7.6

 Moisture

 5.0

 Fat

 1.5

 Minerals (g/100g S.T.) 
 Calcium

 2.30-2.40

 Phosphorus

 1.45-1.65

 Potassium

 0.45-0.55

 Chlorine

 0.16-0.17

 Sodium

 0.13-0.18

 Magnesium

 0.11-0.12

 
Various Uses

Depending on the level of protein concentrate, MPC can be used in the place of skim milk powder or to create specialty food items such as dairy products high in protein and low in carbohydrates (lactose). Similar to SMP, MPC can be used an ingredient in many prepared dishes: infant formulas, desserts, icings, baked goods, meat products, soups, sauces, low-fat spreads, dried dairy-based mixes, milk-based drinks, food products and beverages recommended for use by athletes and in weight-loss diets. MPC serves to increase the degree of opacity in low-fat food products.


Functional Properties

Functional Property

Mode of Action

Food System

Foaming/Whipping

Proteins form stable film of air bubbles (proteins act as air/water interfaces)

Meringues, mousses, cakes, ice creams (soft and hard), whipped cream, soufflés

Emulsification

Formation and stabilization of fat emulsions (proteins act as oil/water interfaces)

Sausages and delicatessen (meat emulsions), dairy drinks, soups, vinaigrettes, sauces, bakery products

Solubility

Greater solubility because preserves original protein structure through ultrafiltration

Dried dairy mixes (coffee whiteners)

Gelling (Thickening, Waterbinding)

Trapping of water in interior protein structure creates increased viscosity

Cheeses, yogurts (firm), sauces, milk-based drinks, creams for desserts, bakery products

Browning/ Colour/ Flavour*

Lactose and proteins undergo Maillard caramelization

Bakery products(pastries, cakes, muffins)

 

*MPC-42 is recommended due to its high lactose content



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