From Shell to Shelf: Top Tips for Processing Egg Products
By Matt Hale, Global Key Account Director, HRS Heat Exchangers
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 Maldives1. As you would eggspect( 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, accounting for 17 % of the UK market2, and 29 % in the US3 last year. For safety and product longevity, most liquid egg products are pasteurised( sometimes known as Extended Shelf Life, or ESL, egg products).
Challenging characteristics
Processing eggs involves a number of key cooling and heating processes to maintain product quality
60 FDPP- www. fdpp. co. uk 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 heatsensitive 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.
Key pasteurisation considerations
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.
Pasteurisation can induce a number of unwanted effects, however, including gel formation and softening of the yolk, or irreversible denaturation of the proteins and changes to appearance. If not handled correctly, thermal pasteurisation can decrease protein content,