High-temperature Short-time Extrusion Research Articles

Physico-chemical and rheological properties of Bengal gram (Cicer arietinum L.) starch as affected by high temperature short time extrusion.

Starch isolated from Desi Bengal gram seeds after conditioning to moisture contents of 16% and 18% was given a high temperature short time extrusion treatment (HTST). Physicochemical, morphological and rheological properties of untreated and treated starches were studied. Proximate composition of native starch revealed 9.2 g/100 g moisture, 0.01 g/100 g fat, 0.22 g/100 g ash and 0.25 g/100 g protein. Extrusion treatment led to a significant reduction (p ≤ 0.05) in amylose content of treatments from 32.5 to 30.4 g/100 g. Also there was reduction in Hunter colour 'L' value (91.6-78.5) with increase in 'a' (0.0-0.4) and 'b' (10.8-14.8) colour values of samples upon extrusion. Swelling index, solubility index and light transmittance presented a significant (p ≤ 0.05) increase upon extrusion. Pasting properties of extruded treatments decreased significantly(p ≤ 0.05) upon extrusion with increase in the moisture content from 16 to 18%. Scanning electron micrographs of native Bengal gram starch revealed small, spherical and smooth surfaced granules while granules were not visible after extrusion due to loss of granular structure. The storage modulus (G') of both untreated as well as treated starches increased with the increase in angular frequency, thereby depicting the dominance of elastic behaviour over viscous behaviour. The FTIR spectra of extruded samples revealed reduction in intensities of hydroxyl, alkyl and carbonyl stretches after extrusion.

Flavour retention during high temperature short time extrusion cooking process: a review

Research on the stability of flavours during high temperature extrusion cooking is reviewed. The important factors that affect flavour and aroma retention during the process of extrusion are illustrated. A substantial number of flavour volatiles which are incorporated prior to extrusion are normally lost during expansion, this is because of steam distillation. Therefore, a general practice has been to introduce a flavour mix after the extrusion process. This extra operation requires a binding agent (normally oil), and may also result in a non‐uniform distribution of the flavour and low oxidative stability of the flavours exposed on the surface. Therefore, the importance of encapsulated flavours, particularly the β‐cyclodextrin‐flavour complex, is highlighted in this paper.

Effect of Cysteine on the Functional Properties and Microstructures of Wheat Flour Extrudates

The effect of the concentration of added cysteine (0, 0.25, 0.5, 0.75, 1.0, and 1.5% (w/w)) on the functional properties and microstructures of wheat flour extrudates was studied in order to elucidate the relationship of the disulfide cross-linking, the extrudate microstructure, and the functional property of proteins through the high-temperature short-time extrusion. The added cysteine markedly affected the functional properties and microstructures of the extrudates during twin-screw extrusion. After extrusion, the disulfide content in the extrudate (including in both protein and cystine) increased by nearly two times. The expansion ratio of the extrudates decreased by 25%. The bulk density of the extrudates first dropped by 50% and then remained constant. The expansion volume of the extrudates first increased by 25% and then returned back. The water-holding capacity of ground extrudates decreased by 16%. The oil-absorption capacity of ground extrudates first increased by 135% and then remained constant. The “whiteness” value of the extrudates increased by 3.9 color units. The gumminess and cohesiveness of the extrudates increased. For the microstructures of the extrudates, the cell size decreased and the cell wall thinned; also, the cell surface morphology changed. The information generated in this study could be applied to predict and control the functional properties and textural characteristics of extruded products. Keywords: Cysteine; extrusion; disulfide cross-linking; microstructure; functional properties

Nutritional effects of expansion and short time extrusion on feeds for broilers

The effect of short time extrusion or expansion on digestibility and energy of feeds and grains was determined in 18–21 day old broiler chicks. Untreated corn-based feed or wheat or barley were compared with the same material treated by expansion or extrusion, and milled to equal size using three replicate groups of 10 birds for each dietary treatment. Extrusion of whole feeds enhanced GE digestion and increased the AME and AME n by 1.5 and 3.5% ( P < 0.05). Extrusion or expansion of wheat or barley and their addition to basal diets increased AME and AME n of the diets by 1.5–2.5% ( P < 0.05). Barley was less well digested than wheat. High temperature short time extrusion and expansion processes appear to enhance energy of common feeds for broilers.

Extrusion Processing Used to Convert Dead Poultry, Feathers, Eggshells, Hatchery Waste, and Mechanically Deboned Residue into Feedstuffs for Poultry

In Experiments 1 and 2, dead broilers (3 and 5 wk old) and dead turkeys (6 and 12 wk old), and broiler feathers were obtained from commercial sources and evaluated for nutritional contribution when co-extruded with soybean meal (48% CP). Samples of each age of dead birds and two feather treatments, with and without 5.13% proteolytic enzyme premix (INSTA-PRO®), were blended with soybean meal in an 25:75 ratio (wt/wt, wet basis) and processed through an INSTA-PRO® extruder. The resulting six extruded products were used in formulating isocaloric and isonitrogenous diets and were compared with a diet containing corn-soybean meal or corn-soybean meal with commercial feather meal when fed to broilers from 1 to 21 days of age. In Experiment 1, feeding diets containing dead broilers supported higher (P ≤ .05) body weight than those receiving the corn-soybean meal control diet. There was no difference (P > .05) in feed conversion. Enzyme treatment of the feathers improved growth rate but not feed conversion over the untreated feather diet in Experiment 1. In Experiment 2, dead poultry and enzyme-treated feather extruded products were good feed ingredients for broilers with feed efficiency and growth responses comparable to the corn-soybean meal control diet.In Experiments 3 and 4, centrifuged eggshells from egg-breaking plants (Source A or B), centrifuged hatchery solid (Source C or D), centrifuged hatchery solid plus liquid (Source C or D), and mechanically deboned turkey frame residue were each blended with ground corn to produce mixtures with 15 to 25% moisture and processed through an INSTA-PRO® extruder. Two experiments involving 480 Hy-Line® 36 laying hens were conducted for three 28-day periods to evaluate hen performance and egg quality when the extruded products were incorporated into the diet. No differences were found (P < .05) in egg production, egg weight, feed conversion, and egg specific gravity for all diets.The microbiological test (total aerobic count) indicated that the pre-extrusion blended mixtures had significant numbers of colony-forming units per gram of sample. The extruded products that exited from the extruder barrel were free of aerobic microorganisms. The results of these studies indicated that high temperature-short time extrusion is an alternative method for converting these poultry industry residues into feedstuffs.