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Technology of milk products Dry Milk powder presentation
DRIED MILK AND MILK PRODUCTS
SHARON A J
Marco Polo in the 13th century reported that soldiers of Kublai Khan carried
sun-dried milk on their expeditions.
Scriptures from the early Bhuddhist and Jain period have documented sweet
made from Heat desiccated milk such as sihakesara and morandeka Which
was used as Desserts to be eaten at the end of Meal.
The first commercial production of dried milk was organized by the Russian
chemist M. Dirchoff in 1832. In 1855, T.S. Grimwade took a patent on a dried
Roller drying was the main means of producing milk powders until the 1960s
when spray drying took over.
Composition of Milk
Carbohydrate: (approx. 5% )
• mainly Lactose→ Lactic acid by bacterial fermentation
• In heated milk products, e.g., in condensed milk, there is also lactulose which is
a little sweeter’
Fat: 3-4% in whole milk;
• contains fat soluble vitamins, pigment carotene & Xanthophylls; contains
cholesterol & phospholipids but is primarily TGs(95%)
• The fat in milk occurs in the form of droplets or globules, surrounded by a
membrane and emulsified in the milk serum part (the whey part or the watery
• Milk is an o/w emulsion which is not naturally physically stable that is why
creaming occurs if it is left to stand.
Casein (80% of milk protein)
• The casein is arranged in super-structures called micelles, which consist of protein together with
phosphate, citrate and calcium.
• The caseins are actually a group of similar proteins, which can be separated from the other milk
proteins by acidification to a pH of 4.6 (Ip)
• The casein micelles also may be coagulated by addition of the enzyme rennin.
Whey proteins (20% of milk protein)
• lactalbumin, lactoglobulin & immunoglobulin
• Whey proteins are more hydrated than casein and are denatured and precipitated by heat rather
than by acid.
Other protein components
• include enzymes such as lipase, protease, & alkaline phosphatase, which hydrolyses TGs, proteins,
& phosphate esters, respectively.
Themilk proteins are of high BV & are readily used by the body
Vitamins & Minerals:
• Vitamins A, B6, B12, C, D, K, E, thiamine, niacin, biotin,
riboflavin, folates, and pantothenic acid.
• Vitamin A is naturally in the fat component of whole milk
and more may be added prior to sale.
• whole milk is generally (98%) fortified with vitamin D
because it is naturally present only in small amounts.
• Low-fat and non-fat milk are fortified with both of these
fat-soluble vitamins because milk fat is reduced or absent.
• Ca & P approx. 1% of milk
• Ca is present as calcium caseinate, calcium phosphate &
• Other minerals present are chloride, magnesium,
potassium, sodium, and sulfur.
The heat processing of milk causes the following
Reduction in water activity.
Substantial destruction of pathogenic and spoilage microorganisms.
Inactivation of enzymes.
Heat induced chemical interactions leading to reduction of Redox potential.
All these help to extend the shelf life of under the ambient temperature
DRIED MILK PRODUCTS
Dry milk: made with whole milk or skimmed milk dehydrated to about 97% by
spray drying & vaccum drying. Good shelf life. Highly hygroscopic & can be
reconstituted to fluid milk.
Skim milk powder: Skim Milk Powder is obtained by removing water from
pasteurized skim milk. It contains 5% or less moisture (by weight) and 1.5% or
less milkfat (by weight) and a minimum milk protein content of 34%.
Khoa: semi-solid obtained from milk by evaporating in open pans with
continuous stirring in circular motion. Yield is about 20% of weight of milk used.
Whey powder : is a mixture of globular proteins isolated from whey, the liquid
material created as a by-product of cheese production. Whey protein is
commonly marketed as a dietary supplement, and various health claims have
been attributed to it in the alternative medicine community.
Flow chart diagram of
Whole Milk powder
Milk powder manufacture is a process now carried out on a large scale.
It involves removal of water at the lowest possible cost under stringent hygiene
conditions while retaining all the desirable natural properties of the milk - colour,
flavour, solubility, nutritional value.
During milk powder manufacture water is removed by boiling the milk under
reduced pressure at low temperature.
The resulting concentrated milk is then sprayed in a fine mist into hot air to
remove further moisture and so give a powder.
Whole (full cream) milk contains, typically, about 87% water and skim milk
contains about 91% water.
Approximately 13 kg of whole milk powder (WMP) or 9 kg of skim milk powder
(SMP) can be made from 100 L of whole milk.
RECEIVING AND SELECTION
Milk should be of high chemical, bacteriological and
Acidity higher than 0.15% reduces the solubility.
Antibiotic and pesticides reduce quality.
Clarification by centrifugation or filtration is needed.
Cooling to 4 degree C.
Standardization: to adjust the ratio of fat and Total Solids.
Standardised milk is heated to temperatures between 75 and 120 C and held
for a specified time from a few seconds up to several minutes (cf.
pasteurisation: 72 C for 15 s).
Preheating causes a controlled denaturation of the whey proteins in the milk
and it destroys bacteria, inactivates enzymes, generates natural antioxidants
and imparts heat stability.
The exact heating/holding regime depends on the type of product and its
High preheats in Whole Milk Powder is associated with improved keeping
quality but reduced solubility.
Preheating methods are indirect (via heat exchangers), or direct (via steam
injection or infusion into the product), or a mixture of the two
Different pasteurisation methods
• Low-temperature-longer time(LTLT)
• 65oC for 30 minutes, called the Holding or Batch
• High-Temperature-Short-Time (HTST)
• heat treatment of 72oC for 15 seconds is applied, followed by
rapid cooling to below 10oC. Also called the continuous system or
• Ultra High Temperature (UHT)
• 149.5oC for 1 second or 93.4oC for 3 sec.
Heat treatment: Higher than pasteurization (88-95 C/15-
1. Destroy all pathogens.
2. Inactivate enzymes (especially lipase).
3. Activate SH groups (antioxidant).
HTST produces better powder quality.
De-aeration of milk before heating protects vitamin C
The preheated milk gets concentrated in stages from around 9.0% total solids content
for skim milk and 13% for whole milk, up to 45-52% total solids.
This is achieved by boiling the milk under a vacuum at temperatures below 72 C in
a falling film on the inside of vertical tubes, and removing the water as vapour.
This vapour, which may be mechanically or thermally compressed, is then used to heat
the milk in the next effect of the evaporator which may be operated at a lower pressure
and temperature than the preceding effect.
More than 85% of the water in the milk may be removed in the evaporator. Evaporators
are extremely noisy because of the large quantity of water vapour travelling at very high
speeds inside the tubes.
In spray drying, milk is concentrated to 40-50% and for roller drying, to only 33-
Highly concentrated milk will form a thick layer on the roller. which inhibits
Highly concentrated milk is viscous and causes difficulties during atomization.
Function : to prevent creaming, or the rising of fat to the top of the container of milk.
The process of homogenization permanently emulsifies the fine fat globules by a
method that pumps milk under high pressure [2000–2500 lb/in2 (psi)] through small
mesh orifices of a homogenizer.
Homogenization mechanically increases the number & reduces the size of the fat
globules. The size is reduced to 1/10 of their original size.
Resulting in the milk that maintains more uniform composition with improved body
and texture, a whiter appearance, richer flavor, & more digestible curd.
Homogenization of highly concentrated milk (more than 3:1) destabilizes protein
and decreases powder solubility.
When the product enters the valve
area under high pressure and with low
velocity it must pass the adjustable
gap between the valve and seat.
Creates a rapid increase in velocity
with a corresponding pressure drop.
The very high energy release causes
turbulence, this in combination with
powerful cavitation will tear apart
particles to a submicron size.
The high velocity collision of the
product on the impact ring will further
contribute to this action.
Atomizing the concentrated milk into a hot air stream (180-200C).
Controlling the air temp., air flow, and size of droplets, water could be removed
from droplets exposed to relatively low heat.
Spray drying: excellent solubility, flavor and color.
Powder leaves the two or three-stage dryer and enters cooling systems.
EFFECTS OF HEAT
Coagulation of protein (lactalbumin & lactoglobulin) at 66°C.
Increasing temperatures and length of heating may break the fat emulsion if the protein
film around the fat globules breaks. Thus the fat will coalesce.
High heat also forms greater amounts of coagulum at the bottom of the pan than low
Maillard reaction or Non-enzymatic browning or“carbonyl-amine browning” reaction
between the free carbonyl group of a reducing sugar and the free amino group of
protein. Max. effect is with lysine followed by tryptophan & arginine.
Destruction of microorganisms at higher temperatures.
Scorching of milk: heating over hot water stirring can prevent it.
Colour, flavour & digestibility.
DIFFERENT TYPES OF DRYING
• Pasteurized milk is first
an evaporator to
approximately 50% milk solids.
The resulting concentrated
milk is then sprayed into a
heated chamber where the
water almost instantly
evaporates, leaving fine
particles of powdered milk
•Milk is applied as a thin film
to the surface of a heated
drum, and the dried milk
solids are then scraped off.
However, powdered milk
made this way tends to
have a cooked flavor, due
to caramelization caused by
greater heat exposure.
• Same as drum
Spray drying involves atomising the milk concentrate from the evaporator into fine
Done inside a large drying chamber in a flow of hot air (up to 200 degree C) using
either a spinning disk atomiser or a series of high pressure nozzles.
The milk droplets are cooled by evaporation and they never reach the temperature of
The concentrate may be heated prior to atomisation to reduce its viscosity and to
increase the energy available for drying.
The remaining water is evaporated in the drying chamber, leaving a fine powder of
around 6% moisture content with a mean particle size typically of < 0.1 mm diameter.
Secondary drying takes place in a fluid bed, or in a series of such beds, in which hot
air is blown through a layer of fluidised powder removing water to give product with a
moisture content of 2-4%.
Technically known as lyophilisation, or cryodesiccation—is a dehydration
process typically used to preserve a perishable material or make the material
more convenient for transport.
The food material is placed in a vacuum chamber and frozen until the water
crystallizes. The air pressure is lowered, creating a partial vacuum, forcing air
out of the chamber; next heat is applied, sublimating the ice; finally a freezing
coil traps the vaporized water.
Freeze drying, which preserves many nutrients in milk, compared to drum
Freeze dried ice cream
Loading a freeze dryer
PACKAGING AND STORAGE
The powder passes through a sieve with 0.7 mm diameter
Important to retain the proper quality during storage.
Container should protect the powder from moisture, air, light
and contamination substances.
Can be Tin cans, Retort pouches, etc.
Multilayer boxes or bags with a polyethylene layer inside.
Cans covered with aluminum foil on the contact surface.
Long storage should be in an atmosphere of inert gas such as
nitrogen or in partial vacuum.
High moisture content of the powder increases lactose
High relative humidity of the environment is dangerous.
QUALITY AND PROCESS CONTROL:
CHEMICAL COMPOSITION OF MILK POWDER (%)
Microbiological and organoleptic control.
Water, fat, free fat, proteins, mineral, Total Ash, solubility,
flowability, bulk density and particle size distribution.
QUALITY DEPEND ON
Manufacturing techniques and parameters
Drying techniques and conditions.
EFFECT OF THE DRYING TECHNIQUE ON POWDER STRUCTURE
AND BULK DENSITY (g/cm3):
Roller drying gives compact structure with irregular shape.
Very low bulk density.
Spray drying gives spherical particles with smooth surface.
Higher bulk density.
High inlet air forms Wrinkles.
Nozzle atomizer gives higher density (more regular shape).
More protein denaturation = less solubility.
Heat treatment increases stability. Lower inlet and outlet temperatures.
Milk quality (acidity is important).
Too low outlet air temperature or high feeding flow rate will increase
Formation of lumps: lactose will absorb water from
atmosphere and form lumps.
TO IMPROVE FLOW ABILITY (ABILITY TO FLOW FREE)
WITHOUT FORMING LUMPS
2. calcium phosphates,
3. silica oxide
can be added to cover the surface and decrease adhesion
Oxidation is enhanced in the presence of oxygen, light and ions.
Packing in a partial vacuum or replace oxygen with inert gases like nitrogen.
Maillard reaction. (too high temperature during drying or too high storage
SKIM MILK POWDER PRODUCTON
Skim Milk Powder is obtained by removing water from pasteurized skim milk.
It contains 5% or less moisture (by weight) and 1.5% or less milk fat (by weight)
and a minimum milk protein content of 34%.
Skim Milk Powder is classified for use as an ingredient according to the heat
treatment used in their manufacture.
There are three main classifications: high-heat (least soluble), medium-heat, and
low-heat (most soluble).
Spray-dried Skim Milk Powder is available in two forms: ordinary or non-
agglomerated (non-instant) and agglomerated (instant).
SKIM MILK POWDER PREPARATION
1. Receiving and selecting milk, Clarification, Cooling and storing at temperature below
7 degree C.
2. Separation to 0.05-.1% fat.
3. Pasteurization: Usually 72 C for 15 sec is used.
4. Heat treatment: Skim milk powder differs from whole milk powder by the heat
treatment given to skim before evaporation.
a. Low heat skim milk: only pasteurization.
b. High heat skim milk: 85-88 C for 15-30 min.
Extent of heat treatment is measured by whey protein index (WPNI): mg N/g
powder. Highest with low heat.
EVAPORATION AND DRYING.
Two-part moisture removal:
a. Evaporation: To increase the TS to 40-50%. Energy used in multiple effect
evaporator is 10 times lower than in spray drying. Also evaporation
produces large powder particles with less occluded air and longer life.
b. Drying: atomizing the concentrated milk into a hot air stream (180-200C).
Controlling the air temp., air flow, and size of droplets, water could be
removed fro droplets exposed to relatively low heat.
PACKAGING AND STORAGE
Non Fat Dry Milk Powder (Skim Milk Powder)
can be stored at ambient temperature with no risk of
oxidative changes as fat is removed.
It is a powdered gruel made from a mixture of malted barley, wheat flour,
and whole milk, which is evaporated until it forms a powder.
Malt powder comes in two forms:
Diastatic malt contains enzymes that break down starch into sugar; this
is the form bakers add to bread dough to help the dough rise and create
a good crust.
Nondiastatic malt has no active enzymes and is used primarily for flavor,
mostly in beverages. It sometimes contains sugar, coloring agents, and
Whey protein is the collection of globular proteins isolated from whey.
The protein in cow's milk is 20% whey protein and 80% casein protein,
The protein fraction in whey constitutes approximately 10% of the total dry solids in whey.
This protein is typically a mixture of beta-lactoglobulin (~65%), alpha-lactalbumin (~25%),
bovine serum albumin (~8%)
The amino acid cysteine in whey protein is a substrate for the synthesis of glutathione in the
body which is an ubiquitous cellular antioxidant; laboratory experiments have suggested
that whey protein and its components might reduce the risk of cancer in animals, suggesting
an avenue for future medical research
The product is obtained by drying liquid buttermilk that was derived from the
churning of butter and pasteurized prior to condensing. Dry buttermilk product
shall have a protein content of less than 30%. It may not contain, or be derived
from, NDM, dry whey or products other than buttermilk and contains no added
preservative, neutralizing agent or other chemical.
The Product should be stored and shipped in a cool, dry environment with
temperatures below 80ºF and relative humidity below 65%.
Applications include bakery products, frozen desserts, dry mixes, beverages,
dairy products, frozen foods, salad dressings and snack foods.
MILK PERMEATE POWDER
Milk Permeate is a by-product of the Milk Protein Concentrate (MPC) production
process, formed after ultrafiltration of milk to extract protein and fat.
The product is then dried using advanced spray drying techniques. Milk
permeate powder is characterized by a clean, slightly salty taste and uniform
particle size. It consists of lactose, water, vitamins and minerals.
Milk Permeate Powder can be used to standardize Skim Milk Powder (SMP) and
is a natural food ingredient with excellent functional and nutritional
characteristics. It is suitable for a wide range of applications including beverages,
seasonings, confectionery, soups, sauces, desserts, bakery and dairy.
FREEZE-DRIED ICE CREAM
Ice cream that has had most of the water removed from it by a freeze-drying
process, sealed in a pouch, and requires no refrigeration.
It is also known as astronaut ice cream or space ice cream, typically a slab of
ready-to-eat dehydrated ice cream. Compared to regular ice cream, it can be
kept at room temperature without melting and is more brittle and rigid but still
soft when bitten into.
It was developed by Whirlpool Corporation under contract to NASA for the
Apollo missions. However, it was never used on any Apollo mission.
Hand book of Milk processing Dairy products and Packaging technology by EIRI board of
consultants & Engineers .Engineers India Research institute.
Vaclavik,V.A., Christian,E.W., Essentials of Food Science, Third Edition, Springer.