Extrusion Cooking

Segmented screwbarrel singlescrew wet extruders

A typical drawing of the single segmented wet extruder is shown in Fig. 3.1. Segmented screw barrel single-screw extruders are the most widely applied cooking extrusion design in the food, pet foods and feeds processing industries. 'Wet' means that steam and water can be injected into the barrel during processing. Typically, the barrels of these machines are also equipped with heating and cooling jackets. They process more tonnage of extruded products than any other extruder design. The...

Development of an extruder product quality controller

We will illustrate this topic by a case study. One class of control strategy that can be used for control problems with interactions or complex responses such as found in the extrusion process is model predictive control (MPC).30 The basis of model predictive control is a dynamic model that describes the features of the process. The model is used to predict the future trajectory of the process outputs for any pattern of input variation. Models are usually linear and obtained by direct...

Classification of ingredients by their functional roles in extrusion cooking

The complex mixture of materials present in a recipe may appear very confusing to the extrusion cooking technologist and machine operator. One of the first steps taken at CCFRA in developing a better understanding of the extrusion cooking process was the introduction of the Guy Classification System for ingredients. This was published in 19943 and is based on the grouping of ingredients according to their functional role using a physicochemical approach. Originally six groups were selected to...

Introduction

Extruders offer food scientists a palette of conditions and ingredients from which new foods may be created. Although snack foods were among the first commercially successful extruded foods, today extruders produce many foods of nutritional importance. Specific product categories are described elsewhere in this book, yet in this chapter the numerous factors that influence nutritional quality in all products will be explored. Emphasis will be placed on human foods, but extrusion effects...

Single vs twinscrew extruder

Single-screw extrusion has been employed successfully in food and feed production over the last 60 years. Because of consumer demands for innovative food products in the market, extruder manufacturers adopted twin-screw extruders approximately 30 years ago. Twin-screw extruders have greater ability and flexibility for controlling both product and process parameters. They are a flexible design permitting easy cleaning and rapid product changeover. Because of the ability to better match the...

Examples from group 4 soluble solids

The most common forms of soluble solids used in extrusion are small carbohydrates and salt. They dissolve in the aqueous phase and form a more viscous plasticising fluid but have little effect on most of the structure-forming biopolymers at low levels of addition ( 5 ). However, they can reduce the level of starch in a recipe by their very presence in the melt fluid. For example if sugar is added at 10 of the dry recipe for an extruded product, using 15 total water for the extrusion, the maize...

Fine details of snack formation

The extrusion process concentrates on the transformation of the starch within the recipe but may be modified to produce a range of snacks with different characters. This may be done by changing the recipe and also by changing processing conditions. The recipes are based on major starch-rich ingredients such as maize, rice, wheat or potato. These materials are different in terms of their composition and their minor ingredients such as protein, lipid, carbohydrates and fibres cause small...

Baby food products

Other products that are relatively new to the toddler or baby food market are snacks designed to be held easily by the child, such as a three-inch stick. These sticks melt and become gummy once in contact with the child's saliva. These products are usually cookie type recipes with similar texture and taste. Cheesy pretzels are common as well. They may be formed into long sticks of 3-4 inches, which are filled with jam. The contrasting texture between the pretzel on the outside and the jam-like...

The market for baby foods

Baby foods and cereals can utilize a number of the above processing techniques in production. However, it is important to first establish the market available to the consumer in baby foods and cereals and define the characteristics of that market. We can easily separate these markets into two categories Highly soluble baby cereals are commonly extruded with high shear rate and formulated to use fruit juices, cane sugar, or fructose as a sweetener and fortified with stable vitamins and minerals....

Starchbased products

The main sources of starch are from the abundant cereal and potato crop of the major industrialised countries of the world. There may be some other crops such as cassava or sago that are also a good source of starch in their countries of origin, but for most manufacturers the large cereal crops are the most economic source of starch. Potato derivatives have unique flavour qualities, which add value to the products in which they are to cover their higher costs. Examples of starch-based products...

Optimised thermal performance in extrusion

Bruyas, Clextral, Firminy 4.1 Introduction The twin-screw extrusion cooking process in the industries producing foods for animal and human consumption has developed considerably over the last 30 years. Twin-screw extrusion technology produces physical and chemical changes in the product through processes of macromixing or micromixing, according to Zoulalian.1 Mixing involves a substantial transfer of energy that plays a major role in the transformation of the material. The...

Macronutrients 621 Carbohydrates

Starchy tubers and grains provide important energy and satiation in most diets. Sugars provide sweetness and are involved in numerous chemical reactions during extrusion. Control of carbohydrates during extrusion is critical for product nutritional and sensory quality. Extrusion conditions and feed materials must be selected carefully to produce desired results. For example, a weaning food should be highly digestible, yet a snack for obese adults should contain little digestible material. A...

References and further reading

AKDOGAN H (1999), 'High moisture food extrusion', Intl J Food Sci Technol, 34(3), 195-207. ALBERTS DS, MARTINEZ ME, ROE DJ, GUILLEN-RODRIGUEZ JM, MARSHALL JR, VAN LEEUWEN J B, REIDME, RITENBAUGHC, VARGAS PA, BHATTACHARYYA AB, EARNEST DJ and SAMPLINERRE (2000), 'Lack of effect of a high-fiber cereal supplement on the recurrence of colorectal adenomas. Phoenix Colon Cancer Prevention Physicians' Network', N Engl J Med, 342(16), 1156-62. ALONSO R, GRANT G, DEWET P and MARZO F (2000), 'Nutritional...

Proteins and amino acids

Extrusion improves protein digestibility via denaturation, which exposes enzyme-access sites. Most proteins such as enzymes and enzyme inhibitors lose activity due to denaturation. The extent of denaturation is typically assessed as change in protein solubility in water or aqueous solutions. These changes are more pronounced under high shear extrusion conditions (Della Valle et al., 1994), although mass temperature and moisture are also important influences. For example, wheat protein...

Defining cooking of cereals

The term 'cooked' or 'cooking' is an ambiguous term used commonly in the market to describe a process which can be defined scientifically for a given ingredient such as a starch granule' s evolution through a glass transition phase, where the starch granule finally can be considered gelatinized and the protein globules are textured. Since most of the ingredients for baby foods are starch- or sugar-based we will try to explain the terminology that pertains to these portions of ingredients....

Socioeconomical future of baby food production

One of the major dependencies of developing countries is the source of food for their young population. In the USA as well as Europe, extensive fund raising has been going on from the private sector to buy food in order to feed the young population of the developing world. These are certainly meritorious, well-intentioned projects. However, the need is growing and to date these projects have not proven an efficient means to lessen the dependence of the populations of developing countries on...

Dietary fiber

Fiber is a term used to describe many food components. In 1999 the American Association of Cereal Chemists coined the following description of dietary fiber Dietary fiber is the edible parts of plants or analogous carbohydrates that are resistant to digestion and absorption in the human small intestine with complete or partial fermentation in the large intestine. Dietary fiber includes polysaccharides, oligosaccharides, lignin, and associated plant substances. Dietary fibers promote beneficial...