Food testing: checking for bad culture

One of the most critical roles of the food manufacturing industry is to deliver food that is not only of good quality but is safe to eat.

Being aware of food safety risks and hazards at an early stage of production, not only can save on costs and time, but it helps to improve public health and build consumer confidence.

Microbiological testing

According to Food Standards Australia New Zealand (FSANZ) , the majority of food recalls (36 per cent) over the past 10 years were due to potential microbial contamination. The three most common bacteria include Listeria, Escherichia coli (E. coli) and Salmonella. FSANZ statistics show that 48 per cent of food recalls in the last 10 years were due to Listeria monocytogenes contamination; 19 per cent were due to Salmonella contamination; and 12 per cent were a result of high levels of E. coli.

Most microbiological contaminations result from poor food handling practices or inadequate temperature control. For example, the presence of E. coli in ready-to-eat foods can result from insufficient heat treatment.

According to FSANZ, E. coli should not be detected in foods at a level exceeding more than
three per gram. The standard plate count, also referred to as the aerobic plate count or the total viable count, is one of the most common tests used in microbiological food testing.

There are a few companies such as Medvet Laboratories and Arrow Scientific that offer microbiological testing services to the food industry.

Arrow Scientific offers a range of HACCP verified 3M testing plates for bacteria including E. coli, Salmonella and Listeria that can help verify sanitation at critical control points throughout the food production line. The latest addition to the company’s product portfolio – the 3M Petrifilm bacteria testing plate – is suitable for both raw materials and finished products and enables food processors to perform onsite microbial testing.

Chemical analyses

In addition to microbiological testing, conducting chemical analyses in the food and beverage manufacturing industry are equally important to ensure food safety. Chemical tests can be applied to identify contaminants such as cleaning products, pesticide residues and metals such as lead.

Food manufacturers may also perform chemical tests to identify product quality. For example, tests on nutritional content and ingredients such as protein, salt, dietary fibre, fat, oil or alcohol content. Companies including MEP Instruments, Graintec Scientific and Arrow Scientific offer a variety of instruments that measure food ingredients.

MEP Instrument’s new modular Packaged Beverage Analyser for Beer (PBA-B) from Anton Paar performs multiple measurements in one cycle – including density and specific gravity, alcohol content, original extract, extract content, apparent extract, degree of fermentation and carbon dioxide content measurements.

The PBA-B requires no sample preparation as samples are taken directly from the package. According to MEP Instruments, the PBA-B, yields results in four minutes and only requires water and a water/ethanol mixture are required for adjustments and calibration.

Water activity

Determining the water activity of a product can help define critical limits for microbial and chemical parameters, which need to be controlled to prevent food safety hazards. It is also an important measure of product quality. For example, information on water activity can set critical control points to avoid loss of crispness in dry products and caking and clumping of powders.

Marketing and Sales Manager at Graintec Scientific, Craig Moore, says the company’s Decagon water activity devices are the company’s best sellers. The latest addition to the Graintec Scientific’s range of instruments is the Decagon AquaLab DUO, which measures water activity and moisture content simultaneously. The sample equilibrates in a sealed chamber and the Duo analyses sample moisture—both water content and water activity—by measuring relative humidity in the chamber.

“Water activity provides a lot of information to manufacturers about the shelf-life, texture, taste [and] smell of their product,” Moore says.

“Water activity is not linear, and thus manufacturers can gain a wealth of information about how they can better develop their product, determine how much water they can use in a product without changing the texture, increase their profits, and avoid those nasty product recalls.”

Looking for qualifications in food testing?

TAFE NSW and TAFE SA offer courses specific to the food manufacturing industry that can help you and/or your workers develop their laboratory skills in food testing.