Process control

Keith Graham, marketing manager, Baker Perkins, discusses the role of manufacturing processes in meeting an increasing demand for taste, texture and convenience in the savoury snack market.

The crowded savoury snack food market is dynamic and developing swiftly, and is largely driven by taste, texture and convenience. Consumers are becoming more adventurous and there is a clear trend to provide differentiation and added value through snacks of diverse shapes and sizes, with an increasingly exotic range of tastes and flavours.

Manufacturers need flexible equip-ment that can generate a range of products, with the ability to bring new products to market quickly and make short life brands a profitable option. Equipment suppliers have to offer new technologies and concepts that will expand end product portfolios. Extrusion connects all these requirements.

Quality first

Today’s sophisticated twin screw extruders are designed to produce consistent high quality products at efficiency levels that minimise downtime and waste. They are automatically controlled using parameters stored in preconfigured user recipes. The ability to change the recipes is usually restricted to production managers or process technologists; product inconsistency caused by operator intervention in the process is eliminated.

Automatic start up and shut down is crucial to smooth and efficient operation. Machines are automatically sequenced from warm up to production and optimised to minimise time and material waste. There is no operator involvement, and therefore no opportunity for error. The shut down sequence is similarly automated to reduce waste and cleaning time.

Expanded products

The basis on which many businesses enter the snack market is a standard line consisting of an extruder, dryer and flavouring system. This will generate direct expanded products – a long established way of making straightforward snacks such as corn curls, corn balls, corn puffs, chipsticks, maize rings and a whole range of profiled shapes – rings, squares, rectangles stars, alphabet shapes and animals.

Products are formed when the material is forced under pressure through a die. As the product emerges from the die the water in it turns to steam, which causes the product streams to expand. The streams are cut into small pieces by high speed blades running against the face of the die. The ‘library’ of profiles is continually being expanded; retrofitting new dies at any point during the lifecycle of an extruder can freshen a product portfolio with novel and attractive shapes.

Die development has extended to the creation of products with a distinctive surface texture, usually consisting of a number of individual strands. Another recent addition to the direct expanded range includes snacks with a cluster-like form, as if several pieces have been linked: they are eye-catching, with a light and crispy texture, and the extensive surface area allows more seasoning.

Downstream, coating with sugar can provide additional options for added value product development, particularly in sweet products.

Line expansion

A crucial advantage of the extrusion process is that, as a business expands, a standard line may be extended at any time to broaden the range of products that can be made to include both traditional and the new generation of indulgent or healthy snacks.

This can include a full portfolio of high specification complex products, including whole grain / multigrain and sweet or savoury filled pillows with intriguing shapes, textures and surface patterns; plus high added-value sticks, pillows, bars and bites in plain, shredded or filled forms. Special dies and cutters, co-extrusion equipment, dryers, fryers, ovens and coolers can be added to form versatile plants.


For many companies, a logical and cost-effective step is the addition of co-extrusion technology, which can be retrofitted to an existing single or twin-screw extrusion line supplied by virtually any manufacturer.

Co-extrusion involves forming ‘pillows’ by incorporating fillings with contrasting tastes and textures into the cereal tube as it leaves the extruder. Extrudate and filling are combined into concentric streams at the die, with the flow at each outlet individually adjustable for consistency and weight control.

Co-extrusion allows the product to have different flavours, colours and textures outside and inside. Virtually any obtainable flavour and filling is practical – sweet and savoury creams, cheese, fruit paste and chocolate praline are typical.

‘Standard’ shapes such as squares can be produced, as well as novel patterns including chevrons, waves and trapeziums. It is even possible to produce different shapes and flavours simultaneously for variety packs.

Co-extruded wafers (or ‘credit card snacks’) are slim, flat or rectangular and can incorporate a variety of fillings. Size can vary from small peanut-sized pieces to small bars. They may be positioned as snacks in their own right or as ‘dipping’ products – perhaps a peanut butter snack into savoury spread or a tomato filled snack into cheese.

Because of their shape, a small amount of filling occupies a large area, and consequently results in an intensely flavoured product. They open up a whole new area of marketing opportunities and can be based on any of the complete range of grains processed by extrusion such as corn, wheat, or rice.

Consumer appeal

In addition to familiar, conventional flavours, Asian, Middle Eastern and Hispanic tastes are becoming increasingly popular, both in conventional and co-extruded products. Chilli, paprika, teriyaki, guacamole, sweet and sour, black bean sauce and a wide family of curries can be used individually or in combination to produce snacks with wide consumer appeal.

The option of replacing traditional savoury fillings with real fruit brings positive nutrition into the co-extruded snack arena. The same ranges of shapes and textures used for savoury snacks are available, and there are many exciting options including different combinations of fruit fillings.

A filling of 100 per cent real fruit or a fruit paste blend can be encapsulated in a crispy wholegrain shell. These bite sized pieces are available as pillows, wafers or bars and provide both confectionery and snack manufacturerswith a way to offer a healthy option as well as taste and convenience to their customers.

The inherent versatility of extrusion allows the development of totally new snacks. For example, croutons, in a range of sizes and shapes and in a variety of flavours, can now be produced on a conventional extrusion line.

Extrusion is the most cost-effective solution for these bagged snacks compared to conventional processes based on mixing, forming and baking of bread dough. Their light, crunchy texture is distinctive, with a firm bite that distinguishes the crouton from other extruded snacks. Process flexibility enables product size changes using a range of dies and rapid flavour changes via a spray unit.

Another innovative technique makes a completely fresh range of products using a specially designed ‘coathanger’ die generating a thin, wide sheet of dough up to a metre wide. This is cut into regular, geometric shapes by an in-line rotary cutter, a machine used in the cracker industry and adapted for snack production.

Engraved rolls cut, and in some cases emboss, dough pieces in a variety of shapes from the full width of the sheet at high speed. Cutting is normally into interlocking shapes to avoid waste. Another type of ‘coathanger’ die produces narrow streams of product, which are shape-profiled before being cut to length: another new and distinctive characteristic. These snacks may be conventionally fried or baked in an oven for a lower fat content.

Healthier options

Reducing fat content has become important to the snack industry as consumer awareness of the importance of diet grows. As most extruded products require no frying they are a natural fit in this sector. Additionally, recent new product concepts involve the use of whole grains and multigrains, which are well established in other food sectors, particularly bakery and breakfast cereals. They make a positive contribution to the nutritional profile as well as the taste and texture of the products.

Multigrain products feature a combination of grains such as wheat, rye, corn, barley or rice, and offer the opportunity for snack manufacturers to develop products with an imaginative appearance featuring new textures and colours.

Whole grain products retain, after processing, all three parts of the original grain – the germ, bran and endosperm – in their original proportions: refining normally removes the bran and germ, losing about 25 per cent of a grain’s protein along with at least 17 key nutrients.

An extruder can be configured to make a wide range of whole and multigrain products. They include shredded, expanded and cracker snacks, all with greatly reduced levels of saturated fat, overall fat content and salt. The end product potential is virtually unlimited, both for new concepts and healthy adaptations of existing brands.

As the snack market continues to develop, more attention is being paid to making snacks from a wider range of ingredients than the traditional potato and corn. Vegetables and pulses are beginning to feature in snacks and the flexibility of extrusion makes it ideal for processing these ingredients to create interesting snack textures without the need for frying.

A new colour change system allows changeover between variations of an extruded snack to be made ‘on the run’: for example, matching the colour of vegetable-flavoured snacks such as carrot, beetroot, tomato, broccoli or peas in a single pack.

Colour is injected into the die and the transition phase is extremely rapid. This skid-based system spells an end to the inconvenience and cost of cumbersome mixing and storage of different coloured snacks, with its impact on waste, hygiene and shelf life.


With low running costs, minimal waste and fast changeovers, twin screw extrusion is an attractive process for snack manufacturers. Companies of all types and sizes use the technology, from new market entrants to established multinationals. It is a flexible process that allows new concepts, shapes and tastes to be pursued, generating profitability for a wide range of products and at high levels of quality.

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