Studies on the development of texturized vegetable products by the extrusion process. II. Effects of extrusion variables on the available lysine, total and reducing sugars

Abstract

Available lysine (AL) losses in extruded cowpea (ECP) and in extruded mung bean (MB) proteins from commercial legumes, were predicted by a least squares regression equation using process temperature, screw speed, buffer pH and moisture content as the major independent variables. The destruction of AL depended strongly on the process temperature, moisture content, screw speed and pH. Total sugars released increased with increased process temperature and moisture content of the products and when screw speed and pH were decreased. The average total sugars was 16.25 mg/g of sample in ECP and EMB products. Reducing sugars were released in a quadratic function wih total sugars. Contour-maps show that the AL retention value could be improved if either the concentration of total or reducing sugars in the products is lowered. Materials and methods Raw materialsCowpea (CP) [Vigna sinensis (L.) Wilczek] and mung bean (MB) [Vigna rudiuta (L.) Wilczek] were obtained from the open market at Divisioria in Manila. These dried samples were contained in rice bags and stored in a cold room ( 10°C) until used. Methodology statistical analysis were described in part I of this series (Pham & del Rosario, 1984).The preparation of samples, experimental design, extrusion processing and Determination of available lysine (AL)The freeze dried samples were analysed for AL and moisture content. AL was determined using the fluorodinitrobenzene (FDNB) procedure of Carpenter (1960) with the modifications proposed by Booth (1971). This involved reaction of the samples with FDNB to form the dinitrophenyl (DNP)-lysine derivative and hydrolysing the sample with 6.1 M HC1 for 16 hr. After refluxing, the samples were filtered and two aliquots were taken from each sample. One aliquot was extracted with ether to remove any excess FDNB or DNP and used as a control. The methyl chloroformate derivative of lysine was formed in the second aliquot and the compound extracted with ether. The absorbance of both extracts was read at 435 nm against water. No correction factor was applied in the calculation of AL. Determination of total sugarsTotal sugars were extracted from the extruded samples by the procedure of Chiang & Johnson (1977). A 5 g sample was extracted with 50 ml of 80% hot ethanol and agitated for 15 min with a magnetic stirrer at room temperature. The suspension was then centrifuged at loo00 rev/min for 10 min. The supernatant was decanted and the residue was re-extracted under the same conditions to insure complete extraction of soluble carbohydrates. The total sugar content in the combined supernatant was determined by the anthrone method (McReady et ul., 1950). Determination of reducing sugarsreaction with 3,5-dinitrosalycyclic acid and phenol (Borel, Hosteller & Deuel, 1952).Reducing sugars were determined from the extracted solution of total sugars by Results and discussion Available lysineThe €-amino group of lysine is free to react like any free amino group in a system. Thus, it could be used as an indicator for the reaction undergone by the ...

The Maillard reaction and pet food processing: effects on nutritive value and pet health

“…Increasing the extrusion temperature to 1808C reduced OMIU-reactive lysine content by 8·4 % for the 20 % protein snack, and by 16·7 % for the 30 % protein snack. Although absolute values were not reported, extrusion of cowpeas and mung beans at temperatures from 93 up to 1328C decreased FDNB-reactive lysine content by 25·4 and 21·3 %, respectively (126) . Lankhorst et al (127) reported that extrusion of an experimental dog food had no effect on total lysine content, but OMIU-reactive lysine content was increased by 20·3 % after extrusion at 1108C and 35·6 % after extrusion at 1508C.…”

“…Increasing moisture content from 25 to 40 % during the extrusion of soyabean meal decreased total and FDNB-reactive lysine content by 5·0 and 6·5 %, respectively (30) . Also for cowpeas and mung beans, FDNB-reactive lysine content has been reported to be decreased with increasing moisture content from 30 to 45 % during extrusion (126) . For peas, however, increasing moisture content from 15 to 30 % during extrusion slightly increased total lysine content (1·2 %) and increased FDNB-reactive lysine content by 9·9 % (30) .…”

“…There is no information available on the effect of screw speed on total and reactive lysine contents during the extrusion of pet foods. Increasing screw speed during the extrusion of cowpeas and mung beans from 100 to 200 rpm resulted in reduced loss of FDNB-reactive lysine content (126) . Similarly, OPA-reactive lysine in a soya -sweet potato mixture resulted in less loss with increasing screw speed from 80 to 140 rpm during extrusion (129) .…”

Influence of extrusion cooking on physicochemical properties and starch digestion kinetics of Sphenostylis stenocarpa, Cajanus cajan, and Vigna subterranean grains

“…Similar extrusion-induced decrease in water solubility of extruded legumes as recorded for extrudates of Vigna subterranean flour in the current study were also reported for HTC Phaseolus vulgaris extrudates as temperature increased from 100–180°C [ 53 , 54 ]. Extrusion-induced decrease in water solubility of extruded legumes is perceived to be due to decreased protein solubility due to protein denaturation, which ultimately reflects on overall water solubility of the extruded legume product [ 54 , 55 ]. Howbeit in other studies, extrusion cooking seemed to increase water solubility of navy and pinto bean flours by 81.6% and 109.5% respectively [ 52 ], and common beans by 15.88–17.91% [ 31 ].…”

Use of near infrared spectroscopy to evaluate the intensity of extrusion‐cooking processing of pea flour

“…The formation of new nondisulphide covalent bonds such as isopeptide crosslinks had been advanced as the major reactions involved in protein texturization by extrusion-cooking (Burgess & Stanley, 1976;Stanley, 1989). In the presence of reducing sugars, Maillard reactions can be also implicated in protein cross-linking (Noguchi et al, 1982;Pham & Del Rosario, 1984b). The lower availability of the basic amino-acids (especially lysine) had been interpreted in this way.…”