No abstract

Extrusion cooking is an ideal method for the manufacture ready-to-eat snacks. The benefits include increased protein and starch digestibility in protein-enriched cereal snack products. Extrusion cooking needs to be controlled if product quality is to be maintained. Extrusion cooking was carried out at barrel temperature of 110˚C-150˚C, screw speed of 350-450 rpm, and feed moisture of 12%-14% to investigate the effect of extrusion conditions on physical properties (expansion ratio and bulk density) of a rice, sorghum and soy flour blend. From response surface analysis, expansion ratio and bulk density were found to be significantly (P < 0.05) dependent on feed moisture and barrel temperature while the screw speed had a significant (P > 0.05) effect. Expansion ratio and bulk density ranged from 2.0 to 2.6 and 0.79 to 0.95 g/ml respectively. One hundred grams of the extruded product would supply 45% of the recommended daily allowance for protein in children aged up to 12 years. The mineral content in 100 g extrudates was found to be 52 mg calcium, 3.01 mg iron and 1.23 mg zinc. The retention of amino acids in the extruded products was 88%-95% with lysine-a limiting amino acid in cereals having a loss of 9.1% after extrusion. Extrusion conditions can be optimized to produce ready-to-eat snack products with high expansion ratio, low bulk density and a good nutritional profile to meet the growing consumer needs for nutritious ready-to-eat snack products.

Cereals including maize generally have limiting amino acids particularly lysine. In most cases, spontaneous fermentation is used to improve the nutritional profiles of maizebased products. However, in such fermentation, biological risks including the presence of pathogenic microorganisms, chemical contaminants, and toxic compounds of microbial origin such as mycotoxins pose a health risk. The aim of this study was, therefore, to improve the nutritional properties of maize flour by reducing antinutritional factors through microbial fermentation by strains of Lactobacillus plantarum and Saccharomyces cerevisiae and their cocultures. A factorial experimental design was used to evaluate the effect of fermentation setups and time on proximate composition, antinutritional factors, and in vitro digestibility of proteins in maize flour.During 48 h of fermentation, protein content was improved by 38%, 55%, 49%, and 48%, whereas in vitro protein digestibility improved by 31%, 40%, 36%, and 34% for natural, Lactobacillus plantarum, Saccharomyces cerevisiae, and their coculturefermented maize flour, respectively. The highest improvement in protein content and its digestibility was observed for Lactobacillus plantarum strain-fermented maize flour.Phytate, tannin and trypsin inhibitor activity were reduced significantly (p < .05) for natural, Lactobacillus plantarum, Saccharomyces cerevisiae, and coculture-fermented maize flour. The highest reduction of phytate (66%), tannin (75%), and trypsin inhibitor (64%) was observed for coculture-fermented maize flour. The two strains and their cocultures were found feasible for fermentation of maize flour to improve its nutritional profiles more than the conventional fermentation process.

The antioxidant activity of extract from roasted barley grain was evaluated by various methods in vitro and in vivo. Results showed that the extract exhibited high antioxidant activities in vitro and in vivo, evidenced by its ability to chelate ferrous ions, scavenge hydroxyl and superoxide radicals, and prevent lipid peroxidation of liver homogenate. The extract significantly increased the total antioxidant capability (T-AOC) in aged mice (P < 0.05). The activities of antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) increased while levels of malondialodehyde (MDA) and manoamine oxidase (MAO) decreased in both the liver and brain of aged mice treated with the extract compared to the control (untreated mice). The results demonstrate potential antioxidant activities and antiaging effect of roasted barley grain. This provides scientific support for the use of roasted barley grain as an antioxidant against oxidative stress.

Microwave processing and cooking of foods is a recent development that is gaining momentum in household as well as large-scale food applications. Barley contains phenol compounds which possess antioxidant activity. In this study the microwave oven roasting condition was optimized to obtain grains with high antioxidant activity measured as the ability to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical. Antioxidant activity of grains roasted under optimum conditions was assessed based on DPPH radical scavenging activity, reducing power and inhibition of oxidation in linoleic acid system. The optimum condition for obtaining roasted barley with high antioxidant activity (90.5% DPPH inhibition) was found to be at 600 W microwave power, 8.5 min roasting time, and 61.5 g or 2 layers of grains. The roasting condition influenced antioxidant activity both individually and interactively. Statistical analysis showed that the model was significant (P < 0.0001). The acetone extract had significantly high inhibition of lipid peroxidation and DPPH radical scavenging activity compared to the aqueous extract and alpha-tocopherol. The reducing power of acetone extracts was not significantly different from alpha-tocopherol. The acetone extract had twice the amount of phenol content compared to the aqueous extract indicating its high extraction efficiency. GC-MS analysis revealed the presence of phenol acids, amino phenols, and quinones. The aqueous extract did not contain 3,4-dihydroxybenzaldehyde and 4-hydroxycinnamic acid which are phenol compounds reported to contribute to antioxidant activity in barley grain.