From fresh to frozen

Ever since the first frozen ready meal appeared on supermarket shelves back in the 1950s, frozen food has become increasingly popular with UK consumers as a regular fixture in the weekly grocery shop.

Offering the ultimate in convenience, frozen food requires little preparation, minimises waste and offers consumers great value for money. The most popular frozen vegetable in the UK is the pea – frozen at the peak of freshness, peas require no preparation and can be cooked in minutes while still retaining nutrients, colour and taste.

Its popularity is in no doubt; in 2014 UK consumers spent more than £508 million on frozen vegetables, with nine in 10 shoppers having purchased frozen peas at some point during the year.

However, the increasing demand for fresh to frozen presents a major logistical challenge in getting the legume from the field to the freezer in such a tight time span.

The UK’s largest frozen vegetable processor, Pinguin Foods, which supplies major multiple retailers including Marks & Spencer, Waitrose, Sainsbury’s and Tesco, pledges to achieve this in under 150 minutes. This requires the process to be managed with military precision and split second timing.


Case study

The Bühler Group, a global supplier of optical sorting solutions to the food and non food processing industries, is instrumental in helping Pinguin achieve its key performance indicator of delivering fresh to frozen peas in just 150 minutes from its 28 acre site in King’s Lynn, Norfolk.

Bühler is also helping to streamline the production process by ensuring that all foreign materials and defective products are removed quickly and efficiently, while helping to ensure the peas are as fresh as possible at the point of freezing.

The company’s optical sorting technology has served the global fruit and vegetable processing industry for decades. In fact, while Bühler’s sorting technology has been around since the 1940s, continued technology advances have resulted in many benefits, including enhanced equipment accuracy and speed in its ability to detect foreign materials (FM), extraneous vegetable matter (EVM) and other unwanted objects to meet exact customer specifications.

“Previously, the sorters used at the plant were only capable of a rejection rate of 15 good to one bad from the reject stream,” says Pinguin’s operations director Neil Winner. “Today, our range of Bühler Sortex optical sorters is operating at three to one, which gives us incredible cost benefits on yield. Our investment in Bühler technology has ensured all of our product is efficiently and effectively sorted.”


High spec tech

The optical sorters are designed to be used on production or packing lines, scanning and analysing the product. Using high definition cameras, broad spectrum lighting and infrared technology, they can also detect and remove product with colour defects or blemishes, as well as foreign objects.

“Our technology is not only looking for any colour or shape defects,” explains David McCambridge, applications specialist at Bühler Sortex. “By using profile shape recognition, colour detection and enhanced InGaAs camera technology, we can simultaneously remove FM such as insects, wood, glass, stones, seeds or flower heads as well as snails, slugs and any other material which will render the product unacceptable. In addition, the optical sorters remove any EVM, whether or not it is derived from the pea plant.”

The technology – high resolution cameras with optical sensors – also enables Pinguin Foods to handle product with very subtle colour defects, while the Sortex E range also uses InGaAs technology to detect a wider range of contaminants and stray fragments of common packaging materials.

Existing technologies often found it difficult to distinguish foreign objects from product, for example, fragments of light wood from potato or cauliflower, cardboard from carrot and some clear and coloured plastics from vegetable mixes.

Bühler’s InGaAs technology was developed to identify these difficult to detect contaminants and work seamlessly with the Sortex E at the end of a packing line to perform a final quality check to identify and reject foreign materials that may have entered the chain during processing.

Profile technology also provides Pinguin Foods with an advanced shape detection system, which intelligently detects and separates touching objects, allowing for higher capacity shape sorting. In addition, the customised, high response ejector is designed with a long life span, capable of working at high speeds with high capacity intakes. The sorters are controlled by a large, colour touch screen, making the equipment easy to operate.


Scrupulous sanitation

Food safety and hygiene are paramount in any modern food processing factory, meaning high standards are crucial. Pinguin’s King’s Lynn plant is no exception; the open design of the sorters makes them easy to clean, ensuring scrupulous sanitation levels are maintained.

“Bühler’s optical sorters are just one part of an extremely intensive process that enables us to deliver the peas from the field to the bag in 150 minutes. It’s a tight schedule with the pea harvest only lasting between six to eight weeks of the year, starting in mid June through to August,” continues Winner.

The peas are harvested by Holbeach Marsh Co-operative (HMC), a co-operative of around 30 member growers who produce vining peas for freezing from a growing region of more than 5,000 acres – ranging from Boston and Spalding to Wisbech and Chatteris across to King’s Lynn and into north west Norfolk – all within 25 miles of the Pinguin plant.


Pea process

Picked by the latest generation of Scania powered pea harvesting machines, the peas are picked and immediately transported to the Pinguin factory where they are first subjected to a tenderness test, using a tenderometer scale, as approved by Campden BRI.

Only the sweetest, most tender peas are graded AA and earmarked for the supermarkets’ premium ranges. These account for around 65 per cent of the crop. The remainder are graded accordingly, with lower grade peas destined for supermarket value ranges.

Once quality is assessed, the peas are mechanically cleaned, removing any dirt, debris, stones and stray pods. They are then blanched for 60 to 90 seconds to deactivate the enzymes that decompose vitamin C and other nutrients causing flavour and colour changes.

The peas are then frozen using an advanced industrial process called individually quick frozen (IQF), in which they are subjected to -40°C temperatures to ensure their core freezes so quickly that the cell structure and flavour remain intact. After freezing, they are sorted using seven of Bühler’s Sortex E1D optical sorters, weighed and put into bulk store freezers.

Before packaging, four Bühler Sortex optical sorters work simultaneously to provide a final quality check to ensure no further impurities have infiltrated during processing and storage, for example, fragments of cardboard, wood and plastics from pallets, plastic tags and packaging. The peas are then sent to a central distribution depot in Wisbech, from where they are dispatched to Pinguin’s customers around the country.

Winner concludes, “Using Bühler’s optical sorters allows us to make the most of the harvest – removing all foreign materials and other contaminants. We’ve increased the amount of good product sorted, which has resulted in fewer complaints from consumers and, in turn, suppliers.

“Complaints are costly so this is not only improving our reputation, but also ensuring that we deliver the best product every time.”

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