From Shell to Shelf: Top Tips for Processing Egg Products
Eggs are one of nature’s most nutrient-dense foods, containing high quality protein as well as being naturally rich in vitamin D, B2 (riboflavin), vitamin B12, iodine, selenium, and several other essential dietary vitamins and minerals. It’s therefore unsurprising that they are one of the world’s most popular foods.
The Netherlands tops the global egg consumption stakes (per person) by some margin, followed by Hong Kong, China, Mexico and the Maldives. As you would eggs-pect (sorry!), thanks to their great natural packaging, the majority of eggs are supplied in their shells, but depending on country and market, the demand for liquid egg products remains strong. For safety and product longevity, most liquid egg products are pasteurised (sometimes known as Extended Shelf Life, or ESL, egg products).
Processing eggs involves a number of key cooling and heating processes to maintain product quality and safety, as well as maximise shelf life, so choosing the right heat exchangers and processing systems is essential. Eggs are not only highly perishable, but also contain a complex mixture of heat-sensitive proteins, fats, vitamins and minerals. Furthermore, they are comprised of both white and yolk, each of which have different textural and nutritional characteristics.
Fresh eggs have a thick white and a raised yolk. Over time, the white thins and the yolk spreads and enlarges as water passes through the membrane from the white into the yolk. Because of this, eggs need to be refrigerated and processed quickly, and one of the key stages in the production of liquid egg is to cool the product to around 5 °C or less immediately after breaking and filtering to prevent further bacterial growth. The contents of an egg are essentially sterile until broken, so one of the aims of processing is to reduce or eliminate any bacteria or contamination which may be introduced once the egg is cracked. Liquid whole egg and yolk should be held at or below 4 °C, and egg whites below 7 °C, meaning that heat exchangers (such as the HRS MI Series) are crucial in egg processing.
The other crucial thermal process for producing liquid egg products is UHT pasteurisation. However, while the white and yolk are distinct components, when mixed, they interact mutually – for example, egg white is denatured at 58 °C while yolk is denatured at 65 °C. These low temperatures can make it hard to aseptically process natural liquid egg products, so in many cases eggs are cooked before the minimum time and temperature required for pasteurisation has been achieved.
Various time and temperature regimes are used to pasteurise eggs depending on the product, which could be whole egg; separated egg (whites or yolks); or a treated product, like salted yolk. Each product type presents a different challenge in terms of viscosity, and products with added salt also introduce a higher likelihood of equipment degradation or corrosion.
Corrugated tube heat exchangers such as the HRS MI Series, are ideal for pasteurising liquid egg and other egg products. The corrugated design creates turbulent product flow, which reduces fouling and improves heat transfer. This means that a smaller corrugated tube heat exchanger will provide an equivalent (or even superior) performance to a similar-sized smooth tube heat exchanger. Where there is greater risk of fouling, or where the product needs particularly careful handing (for example, with some cooked egg products), then the gentle action of the HRS Unicus Series of reciprocating scraped surface heat exchangers (SSHEs) is ideal.
A final consideration when choosing equipment for egg processing is the ability to clean-in-place (CIP), which is particularly important given the physical nature of the product and the potential for the formation of harmful bacteria. All HRS heat exchangers and pasteurisation systems are designed for efficient, thorough and traceable CIP, giving users peace of mind in addition to industry-leading performance.