FOOD & BEVERAGE
CRACK THE CHALLENGE OF THERMAL EGG PROCESSING WITH TUBULAR HEAT EXCHANGERS
Corrugated tube heat exchanges provide a number of benefits over other designs
By Matt Hale, international sales & marketing director, HRS Heat Exchangers E
ggs are a key foodstuff and ingredient. According to industry data, Britons eat an average of 197 eggs a year. While shell-on eggs account for the bulk of this consumption, processed egg products represent 20 per cent of the market, with a value around £213 million a year. Processed egg products can take a number of forms but the most common is liquid egg, which accounts for around 64 per cent of processed egg production in the UK.
BUYING BRITISH
Overall consumer demand for eggs has risen steadily over the decade and Brits increasingly want the reassurance of home-produced eggs, with UK production growing 28 per cent over the last ten years. One of the reasons for this is the recognised high production standards and food safety assurances which come with British eggs (indicated by the British Lion mark). That quality and reassurance is also sought by the buyers of processed egg products. Not only does this place specific requirements on the raw materials used by egg processors, but it also means that the equipment used must be of the highest quality, delivering reliable results time after time.
EGG CHARACTERISTICS
Fresh eggs have a thick white and an upstanding yolk. Over time, the white thins and the yolk spreads and enlarges as water passes through the membrane from the white into the yolk, weakening it. Because of this, eggs are refrigerated and processed quickly, usually within a week. Liquid egg is a very delicate product as the proteins in egg are more sensitive to heat than other products, such as milk or juices. This is due to the fact that the white and yolk are distinct components with different compositions and behaviours. When mixed, they interact mutually – for example, egg white is denatured at 58°C while yolk is denatured at 65°C.
22 DECEMBER/JANUARY 2021 | FACTORY&HANDLINGSOLUTIONS
These low temperatures also make it hard to aseptically process natural liquid egg products; the eggs are frequently cooked before the required time and temperature minimums are achieved.
THE IMPORTANCE OF PASTEURISATION There may be a number of reasons to process eggs, including convenience, to extend shelf life or as part of other food processing and manufacturing operations. The main reason to pasteurise egg products is for food safety, but other reasons include ease of use, improved hygiene and product uniformity. Depending on the exact combination of treatment time and temperature used, it is possible to produce a shelf life of up to 16 weeks for refrigerated liquid egg products.
Irrespective of the treatment method used, it is important to use fresh, clean and sanitised eggs, and to chill and filter them immediately after breaking. 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. Yolk and whole egg products are generally pasteurised in their liquid form, while liquid egg white may be pasteurised when sold as a liquid or frozen product. In contrast, dehydrated egg yolk (with the glucose removed) is normally pasteurised by holding containers in a large chamber over several days.
TECHNICAL CHALLENGES
For most liquid egg products, pasteurisation using heat exchangers remains the main form of heat treatment. Various time and temperature regimes are used to pasteurise eggs depending on the product, which could be whole
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54
