Introduction • A Focused Improvement Team (FIT) was formed in Castlemaine Perkins

in February 2011 to identify the root cause of a can corrosion issue.

• Leaking cans in the trade have been an intermittent but recurring problem

for Castlemaine brewery.

• Secondary corrosion spreads quickly to adjacent

palletised cans causing further leakage.

Examination of leaking pallets rarely found any

cause to explain the initial can leak.

• Previous attempts to determine the cause of this issue centred on the

capability of the beer to degrade the aluminium can in isolation. Beer is

generally not acidic enough to have any significant effect on the cans. Other

brewery related materials in proximity to the can line area were considered

but did not induce this type of corrosion.

• Bacterial corrosion of aluminium is a concern in the aerospace industry.

This lead was followed to determine if Microbiologically Induced

Corrosion (MIC) or Biocorrosion could be causing our cans to leak.

Method Is there bacteria in our brewing or packaging environment which can

cause this?

• Three separate trials were performed using broth

inoculated with a Lactic Acid Bacteria & Wild Yeast

(typical beer spoilage organisms) and Aerobic Bacteria

periodically found in the can line pasteuriser.

• Filled and pasteurised cans with patches of their

print removed were incubated @ 30

C for up to 4 weeks.

Results • Can leakers were obtained after 8 days of incubation in the Aerobic

Bacteria inoculate.

• Bacteria had adhered to the surface of the can and produced aggressive

metabolites, such as organic & inorganic acids.

• These acids produced by bacteria accelerate

corrosion which results in the formation of

pin holes which cause the entire contents of the can

to leak.

• In real world situations the spillage of beer would then provide the vehicle

and nutrients for the bacteria to attack further cans in the carton and spread

throughout the pallet of product.

• The bacteria causing the can corrosion was identified as a water borne

organism (i.e. Pseudomonas spps) which is capable of growing under

packaging line conditions.

Identify The Root Cause of Secondary Can Corrosion In The Trade

Team: Ben Lanthois, Craig Lindsay, Simon Rowe, Leigh Oram & Rachel Ryan.

Presented by: Rachel Ryan, Castlemaine Perkins, Brisbane Australia.

Issue Action Result

Can line hygiene ATP testing & ClO2 spray system to be

introduced

ATP levels of < 150 RLU

Moisture on the cans

Air blowers to reduce the amount of moisture

on the cans before packaging

Reduction in the number of micro organisms as

there is limited moisture available

Bacterial access to the aluminium can occur

during transport

Introduce a barrier layer to protect the surface of the can.

Not feasible as it would be too expensive

Humid environment in NT & QLD are perfect

conditions for bacteria to grow.

No control over the humidity in this part of

Australia.

Controlled atmosphere shipping and storage

would be too expensive.

Can Line ATP Testing

• ATP testing of the can line identified a number of hot spots (e.g. filler,

air blower) where ATP levels were atypically high.

• After conducting a line clean, further inoculation studies in the lab

determined that ATP levels above 150 RLU were likely to mean

associated microbiological activity would fast track corrosion.

• While purely sterile conditions were not required, having the external

surface of the can < 150 RLU was likely to eliminate the opportunity

for corrosion.

Summary What is the solution?

The root causes of secondary can corrosion at Castlemaine brewery

were identified and Table 1 shows 4 of the key contributing factors.

Table 1

Can line hygiene, moisture reduction and containment measures

have been put in place. We are confident that there will be a visible

reduction in the number of leaking cans in the trade.

Conclusion An investigation has been completed into the intermittent corrosion

of canned beer from Castlemaine brewery with recommendations

put forward.

Bacterial populations facilitated an acidic corrosion of cans which

spread quickly with beer leakage to adjacent cans.

Hygiene testing enabled the provision of an ATP test measure to

provide indicative data for in brewery risk assessment and control.

A sanitising spray system combined with air blowers to reduce

moisture and the ATP testing regime will be implemented.

ATP counts ex the air blowers & filler > 500 RLU.