Cooking extruder

Tossavainen, O., Hakulin, S., Kervmen, R., Myllymaki, O., and Linko, P. (1986). Neutralisation of acid casein in a twin-screw cooking extruder. Lebensm. Wiss. Technol. 19,443 47. 

Cooking extruders have been studied for the liquefaction of starch, but the high temperature inactivation of the enzymes in the extruder demands doses 5—10 times higher than under conditions in a jet cooker (69). For example, continuous nonpressure cooking of wheat for the production of ethanol is carried out at 85°C in two continuous stirred tank reactors (CSTR) connected in series plug-flow tube reactors may be included if only one CSTR is used (70). 

One of the first applications of biodegradable materials is based on the cooked, extruded, and expanded starch known from the food and chemical sectors (Fig. 14.23). Starch is cooked with water in the extruder and chemically modified as necessary or mixed with plasticizers, then expanded to a starch foam and dried. The extrudate is ground so that the functional properties thus created can be used in the food/chemicals sector. The foamed, cut, and dried extrudate is the end product for loose-fill packaging applications. The degree of expansion is a measure of the foam texture. It increases strongly with product temperature at the die, helped by a higher specific mechanical energy input. However, both measures increase the water-solubility of the product. 

Altomare, R. Ghossi, P. An analysis of residence time distribution patterns in a twin screw cooking extruder. Biotech. Progress 1986, 2 (3), 157-163. 

In a more recent study, Hinchliffe and Willis (2003) model dynamic systems using genetic programming. The new approach is evaluated using two case studies, a test system with a time delay and an industrial cooking extruder. The objectives minimized are the root mean square error and the correlation and autocorrelations between residuals. The residuals of a model represent the difference between the predicted and actual values of the process output. In this work, two MOGPs are compared, one based on Pareto ranking but without preferences, and... 

An extrusion system consists of several important subsystems (i) a feed delivery and proportioning system (ii) a preconditioning area, which enables the raw materials to equilibrate in moisture content and heat (iii) the cooking extruder itself (iv) a laminar-flow area or die that allows aligning of molecules to occur (v) a die and cutter to shape and cut the product into pieces and (vi) a dryer/cooler to reduce moisture in the final product to a microbiologically stable level. 

Meuser, F., Gimmler, N., and Ceding, J. (1990) System Analytical Consideration of Derivatization of Starch with a Cooking Extruder as Reactor, Starch/Starke 42, 330—336. 

Huber, G.F. 2001. Snack foods from cooking extruders. Chapter 12 (pp. 315-367) in Snack Foods Processing. E. Lusas and L.W. Rooney (eds.). First edition. Technomic Publishing,... 

Extrusion-cooking of cell-wall rich products (e.g. wheat bran, apple pomace, citrus peels, sugar-beet pulp, pea hulls.) led to an important solubilisation of polysaccharides of various types without extensive degradation of the polymeric structure. The possibility of obtaining gelled systems directly with the extruded pectin-rich materials was demonstrated. 

The effects of extrusion-cooking mainly on citrus fibres will be now detailed on samples which have been, unless otherwise stated, extruded in the same average conditions (SME 250kWh/t). 

An important feature concerned the degree of methylation (dm). A value of 81 % was obtained after acid extraction and a very high value of 91 % was obtained for the pectins from extruded fibres. This is an unusual value for a dm and this result shows that extrusion-cooking had a very limited effect on the methylation of the pectin. 

Three different whey protein products extruded at the cook temperature of 75 °C resulted in varying degrees of melt texturization (Table 5.3). Among the whey proteins, WPC (WPC80) was the least texturized. Whey lactalbumin (WLAC) and WPI were both significantly (p < 0.05) more texturized, but a wider spread of texturization was observed for WPI, the initial and final values were from 28% to 94.8%, and therefore more emphasis was placed on studying WPI (Onwulata et ah, 2006). 

Calcium caseinate and butter oil have been extruded directly at 50-60% moisture levels to obtain a cheese analog with no surface water or fat (Cheftel et ah, 1992). The fat emulsification and melting ability increased with screw speed or barrel temperature. The texture of the extmded analogs was similar to those obtained by batch cooking and was affected by pH (Cheftel et ah, 1992) and emulsifying salts (Cavalier-Salou and Cheftel, 1991). The product can be used as adjimcts for hamburger, pizza, and sauces. 

Onwulata, C. 1., Isobe, S., Tomasula, P. M., and Cooke, P. H. (2006). Properties of whey protein isolates extruded under acidic and alkaline conditions. /. Dairy Sci. 89, 71-81. 

Products where this is the sole expansion system are extruded products. This sort of cooking is used for the production of breakfast cereals, savoury snacks and some crisp breads. Of these, only the crisp breads are really within the scope of this book. 

Extrusion Cooking. In extrusion cooking the ingredients are fed into the extruder either individually or as a pre-made slurry. The ingredients would obviously vary, depending on the product required, but are likely to include flour and water. 

Extrusion cooking is an ideal system for a large company. The equipment is capital intensive while the products can often be made from relatively low cost ingredients. Setting up an extruder is complicated, so extruded products are relatively hard to copy. 

An extruder can, under suitable conditions and with the right ingredients, mix, cook, knead, shear, shape and form. Claims are made that an extruder saves capital cost since the capital cost of an extruder is less than that of the other equipment needed to perform all these operations. This may be true but is not necessarily the way that an existing bakery would view things since they probably already have the traditional equipment and need to purchase an extruder. 

Extruders are normally classified by their method of construction, i.e. twin screw or single screw and the operating conditions, i.e. cold extrusion or extrusion cooking. Cold extrusion is used to make liquorice and pasta among other products and so is outside the scope of this work. Extrusion cooking, which is defined as heating the product above 100 °C, has many uses. 

The matrix used for the encapsulation of juice solids was a mixture of low DE maltodextrin (DE 10) and lactose. A typical formulation prior to cooking would be 23% water, 26% lactose and 51% maltodextrin. This material was cooked to the desired temperature (ca. 110 C), mixed with 85 Brix juice solids and optionally, peel oil, extruded, washed and dried. The extrusion process is essentially the same as used by Swisher (3), A product containing up to 40% juice solids may be produced via this process. This loading of juice solids is substantially greater than the 10-15% juice solids loading claimed by Barnes and Steinke ( 5 ). 

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