TRANSPORTING SKIM MILK POWDER THE RIGHT WAYBY ADAM WILSON FOUNDER OF THE WILPAK GROUP

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What is the common ingredient in many bakery products, confectionary, milk chocolates, processed meats, ready to cook meals, baby foods, ice cream, yoghurt and health foods?

The answer is skim milk powder.

With that in mind, it is no surprise that according to Dairy Australia, Australia has produced 1.1 million tonnes of skim milk powder in the last five years. Another surprising fact is that approximately 70-75% of all Australian-produced skim milk powders are exported overseas1.

Before we delve into the effects of poor storage on skim milk powders and the solutions available to avoid these mistakes, it is important to identify exactly what the ideal storage environment for skim milk powders is.

Milk powders are hygroscopic, meaning they attract surrounding moisture as a result of high lactose content. With that in mind, the ideal storage conditions for skim milk powders is a cool and dry environment, away from strong odours.

When skim milk powder is stored in a cool and dry environment, its shelf life exceeds two years. Specifically, when stored at 15°C and a humidity of 15% the shelf life of skim milk powder is:

• Maximum: four years • Average: three years • Minimum: two years.

The logistical challenge of exporting, in ideal conditions, tonnes of perishable skim milk powder to a continent across the globe is no easy feat. It is no wonder that cost-effective storage and efficient logistics are critical success factors to the milk powder industry.

So what exactly are the challenges for milk powder exporters? What are the common mistakes that can be easily avoided? And what are the best solutions for the international transportation of milk powders from Australia?

If you would like to learn more about this issue, its solutions and much more, keep reading.

It is easy to forget that skim milk powder is perishable. It is also a popular misconception that powdered products last long periods of time without requiring specific surroundings. However, exposure to prolonged radiant heat and moisture can make the milk powder dangerous to consume.

Too much moisture will introduce mould, odours and ‘off-flavours’. Maintaining optimal storage conditions and preserving a longer shelf life thereby affects the profits of both producers and exporters, and potentially brand reputation as well.

THE IDEAL STORAGE ENVIRONMENTS FOR SKIM MILK POWDERS

1. Dairy Australia 2015, Milk Powder. Available from http://www.dairyaustralia.com.au/Markets-and-statistics/Production-and-sales/Milk-Powder.aspx

SKIM MILK POWDER STORAGE

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As previously mentioned, skim milk powder is hydroscopic, meaning that it will attract moisture from the atmosphere. This absorption alters the physical properties of the powder, which can make it brown and/or sticky.

When minor, these side effects of high humidity do not present a health or safety problem for consumers. If the browning is slight, there may still be flavour changes (making the product less desirable for applications such as yoghurt production), but the changes are not noticeable in bakery applications. Additionally, stickiness or “caking” can be resolved through grinding the powder to make it once again free-flowing.

However, a possible consequence of allowing skim milk powder’s moisture content to surpass 15% is microbiological growth, which is dangerous if consumed. If growth is detected, the product must be discarded.

The main concern for the transportation of skim milk powders is health and safety. It is common for slight changes in skim milk powders to occur during storage. As most skim milk powders are processed into other goods, small changes are quite negligible and usually undetectable. However, if skim milk powders are exposed to radiant heat, there are a number of changes that occur that can pose safety issues for human consumption.

Flavour and Smell

Problem: The flavour of skim milk powders should be sweet and free from any rancid odours. But, off-flavours may develop over time in the presence of other food products or materials (onions, spices, petrol, etc.) during storage or transport.

While off-flavours are not ideal, if an off-flavour has been produced due to the presence of other food products, the skim milk powder will be safe for human consumption. Still, this flavour change reduces product integrity and can render the milk powder undesirable and possibly unusable for food producers and other consumers.

This problem can be easily avoided with proper cover solutions.

THE EFFECTS OF POOR STORAGE ON SKIM MILK POWDER SHELF LIFE

THE SIDE EFFECTS

Stored skim milk powders with exposure to above 35°C and 90% relative humidity conditions for over three months exhibited the following changes:

• Reduced shelf life (by a factor of four) • Non-enzymatic browning • Possible bacterial growth

Storing skim milk powder for three months at 37°C and 90% relative humidity is equal to storage for 12 months at ambient temperate climates (approximately 15-25°C and 80% or less relative humidity).

That’s a staggering 75% reduction in shelf life due to exposure to radiant heat

Solution: Insul® products are designed to seal and separate goods during storage and transport, substantially reducing the impact of surrounding odours and preserving the skim milk powder’s original flavour.

Please Note: Off-flavours and smells could also be a by-product of microbial growth as a result of exposure to excessive moisture. Skim milk powders should be immediately discarded if any growth has been detected.

Browning

Problem: Skim milk powders that have developed extensive browning should not be used, as the colour change may indicate degradation. Browning or the “Maillard Reaction” (non-enzymatic browning due reactions between amino acids and sugars) in milk powders produces adverse effects on the colour of the recombined products and is a result of a combination of exposure to moisture and heat. Browning will occur faster as the storage temperature and moisture levels are higher.

Solution: To retain the original properties of the skim milk powder during storage, temperatures should be below 20°C and the water activity level below 0.2. Insul® technology is proven to keep product temperatures stable and protects from ambient heat.

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Acidity

The acidity levels or pH levels of milk powders decrease when stored in a room-temperature environment.

Problem: While changes in pH levels are not significant for skim milk powder at the commercial level, if poorly stored, an acidic taste may develop as a result. If an acidic, unpleasant taste is noticed, the product should not be used.

Solution: To maintain cooler temperatures for the skim milk powder when the temperature of the storage facility or transport vehicle is room temperature or higher, Insul® products can be used.

Solubility

Extended exposure to high temperatures while in storage will result in the skim milk powder losing its solubility. The term solubility is also used to describe the dispersing characteristics of the skim milk powder when reconstituted with water or other fluids.

Problem: Lost solubility creates a “sticky” consistency and the powder can become “caked” or lumpy. When this occurs, the powder must be given additional time to dissolve and requires extra stirring and/or grinding, which has commercial implications.

Solution: In the diagram below we can see that the best temperature to store skim milk powder and avoid insolubility is sub 20°C degrees. Again, Insul®’s technology creates a temperature-controlled environment, so the solubility of the skim milk powder can be preserved.

Storage time (days)

0 10 20 30 40 50 60

Chan

ge in

sol

ubilit

y (%

)

0

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100

Effect Storage Temperature on Solubility of Milk Protein Concentrate (MPC85)

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It should be apparent at this point that skim milk powder is a perishable and can be adversely affected by radiant heat and moisture. Substantial loss of shelf life, microbial growth, and flavour changes are among these significant effects.

The Wilpak Group has a variety of ideal solutions to store and transport skim milk powder without requiring the investment of millions into industrial refrigerators and refrigerated transport.

Insul® Range

The Insul® technology behind the Wilpak Group’s Insul® range is a seven-layer thermal insulation material optimised to hold a consistent temperature environment by reflecting radiant heat and preventing cool air from escaping.

The Insul® technology is proven to be able to maintain ambient temperatures even when exposed to radical external temperature changes, such as when shipments are placed in loading docks and exposed to heat from the sun. The Insul® technology provides the ideal environment for the storage and transportation of skim milk powders as it can regulate temperatures and avoid radiant heat exposure that can reach up to 50°C.

Below is a test conducted by an independent exporter of film, which shows how the Insul® technology can protect freight from substantial temperature spikes over a several day period.

The Insul® technology is offered in a variety of forms including a freight pallet cover, box liners and mail liner. The Wilpak Group can also customise a solution to fit any special requirements.

THE IDEAL SOLUTION

Start Time 10/08/04 8:52:00 Finish Time 16/09/04 13:52:00

Without Insulcap®

Internal (°C)

Days

Shipped in containerPreshipmentDischarged at

Hong Kong Berthed at Yantian

-40

-30

-20

-10

0

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60

0 5 10 15 20 25 30 35

With Insulcap®

If you would like to know more about skim milk powder logistic solutions:

Call us on 1300 881 660

Visit us on wilpak.com.au

Download our brochures, case studies and results

Adam Wilson Michael Partyka John Hell Ajit Bhatia

CONNECT WITH OUR DEDICATED TEAM

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