Enzymatic hydrolysate of African yam bean seed protein isolate was prepared by treatment with alcalase. The hydrolysate was further fractionated into peptide sizes of <1, 1–3, 3–5 and 5–10 kDa using membrane ultrafiltration. The protein hydrolysate (APH) and its membrane ultrafiltration fractions were assayed for in vitro antioxidant activities. The <1 kDa peptides exhibited significantly better (p < 0.05) ferric reducing power, diphenyl-1-picryhydradzyl (DPPH) and hydroxyl radical scavenging activities when compared to peptide fractions of higher molecular weights. The high activity of <1 kDa peptides in these antioxidant assay systems may be related to the high levels of total hydrophobic and aromatic amino acids. In comparison to glutathione (GSH), the APH and its membrane fractions had significantly higher (p < 0.05) ability to chelate metal ions. In contrast, GSH had significantly greater (p < 0.05) ferric reducing power and free radical scavenging activities than APH and its membrane fractions. The APH and its membrane fractions effectively inhibited lipid peroxidation, results that were concentration dependent. The activity of APH and its membrane fractions against linoleic acid oxidation was higher when compared to that of GSH but lower than that of butylated hydroxyl toluene (BHT). The results show potential use of APH and its membrane fractions as antioxidants in the management of oxidative stress-related metabolic disorders and in the prevention of lipid oxidation in food products.

This research characterized flour and raw starches isolated from red and white sweet potato cultivars. Their composition, determined by proximate analysis, is typical of sweet potato cultivars. These cultivars have high amylose content (32-34%) and exhibit a Ca-type X-ray diffraction pattern. Similar gelatinization characteristics were detected for both starches with onset temperature of 67 degrees C and enthalpy of 10.5-11.0 J/g. Starches of both red and white cultivars had well-correlated (r (2) = 0.982) and high solubilization and swelling temperatures, starting at 80 degrees C. Pasting properties of the white cultivar exhibit lower tendency for retrogradation. Water and oil absorption capacities were low for both red and white flours. When parboiled, both cultivars showed improved water absorption capacity and decreased least gelation concentration. It is concluded that the white cultivar should be preferred when low retrogradation tendency is required.

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Nutrition transition to high energy-dense foods has been implicated as the major causes of diet related diseases. Plantain-based dough meals supplemented with soybean cake and cassava fibre were developed by combining them in different proportions using response surface methodology. The flour blends were analyzed for the nutritional composition while the glycaemic index, antidiabetic potentials and protein digestibility of the dough meals were determined in wistar rats. The nutritional and essential amino acid contents of the flour blends were comparable to that of cerolina (a commercially available food product commonly recommended for diabetic patients). The rats fed with the formulated dough meals had lower glycaemic index and glycaemic load, and the blood glucose was significantly reduced compared to cerolina and metformin (a synthetic antidiabetic drug). All the plantainbased dough meals were comparable to cerolina and metformin in terms of nutritional quality and blood glycaemic control activities, respectively. Hence, the formulated plantain-based dough meals have potential to be used for the prevention and management of diabetes mellitus.

Marble vine (Dioclea reflexa) seed flour was defatted using n-hexane and made into a protein isolate by alkaline solubilization and acid precipitation. The protein isolate was hydrolyzed using alcalase and fractionated into different peptide sizes of <1, 1-3, 3-5 and 5-10 kDa using ultrafiltration membranes. The hydrolysate and its membrane fractions were evaluated for amino acid composition and in vitro antioxidant activities. The results showed that sequential fractionation resulted in higher serine, glutamic acid1glutamine, glycine and tyrosine contents. The 5-10 kDa peptides exhibited significantly (P < 0.05) higher 1,1 diphenyl-1-picryhydradzyl radical scavenging and metal chelation activity when compared to the unfractionated protein hydrolysate and other peptide fractions. Lipid oxidation was significantly (P < 0.05) attenuated by the peptide fractions. We conclude that peptide antioxidant activities were significantly (P < 0.05) improved by membrane fractionation, especially for the <1 kDa and 5-10 kDa fractions. PRACTICAL APPLICATIONSOxidative deterioration of foods, which limits shelf life, increases economic losses and may even lead to formation of toxic compounds which can be prevented using synthetic antioxidants. However, there is increased consumer preference for natural sources of antioxidants. The protein hydrolysate and membrane fractions produced in this work showed antioxidant ability that could make them candidates to replace potentially toxic synthetic antioxidants in foods. Metal chelating ability of the peptides can be used to prevent metal ion-dependent initiation of toxic free radical formation in foods. Incorporation of the peptides into foods will enhance scavenging of toxic free radicals that may form during storage, thereby improving product freshness and longevity. The linoleic acid inhibition potential of the peptides can be used to prevent lipid peroxidation and fatty acid deterioration in foods. Therefore, the Dioclea reflexa seed protein hydrolysates represent good natural sources of antioxidant food preservatives.

The nutritional quality of food transcends the availability of nutrients in food to being utilizable by the consumer. In this study, a complementary diet for infants was formulated with quality protein maize, soybean protein concentrate, and cassava starch. The formulated diet was extruded and the effect of extrusion on some antinutritional factors and in vitro protein and starch digestibilities of the meals were assessed. The amino acid profile of the samples was determined while other protein quality indices were calculated. The essential amino acid index of the formulated meal ranged from 87.3 in tryptophan to 133.7 in tyrosine-phenylalanine. Protein efficiency ratio of the formulated meal ranged from 1.20 to 2.45. The calculated biological value ranged from 92.57 to 95.20%.Extrusion cooking significantly improved the in vitro protein and starch digestibilities and significantly reduced some antinutritional factors of the formulated meals. Practical applicationsAdequate nutrition during infancy and early childhood is fundamental to the development of each child's full human potential. It is well recognized that the period from birth to 2 years of age is a "critical window" for the promotion of optimal growth, health, and behavioral development. Longitudinal studies have consistently shown that this is the peak age for growth faltering and common childhood illnesses. Nigeria is well endowed with adequate food supplies, however, more than one third of the children under the age of 5 are malnourished and of all deaths of children lower than 5 years of age are directly or indirectly attributable to malnutrition hence the reason for carrying out this study. Foods with balanced amino acid profile can be obtained by mixing legumes and cereal grains. Extrusion cooking utilizes the high temperature short time phenomenon which is effective for the improvement of the biological value of food. K E Y W O R D S amino acid profile, antinutritional factors, complementary diet, essential amino acid, extrusion cooking, in vitro protein digestibility, in vitro starch digestibility, protein quality, quality protein maize, soybean protein concentrate

The aim of this work was to compare the antioxidant and angiotensin converting enzyme (ACE) inhibitory properties of Moringa oleifera seed protein isolate (ISO) and its enzymatic protein hydrolysates. ISO was subjected to enzymatic (alcalase, pepsin and trypsin) hydrolysis to obtain alcalase isolate, pepsin isolate and trypsin isolate hydrolysates (AIH, PIH, TIH). Amino acid composition was similar for the samples except that TIH had lower Sulphur-containing amino acids while PIH was lower in tryptophan. All the samples were tested for antioxidant properties through free radical scavenging abilities such as 2,2 diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radical scavenging assays as well as ferric reducing antioxidant power (FRAP) and metal ion chelation assays. The maximum percentage inhibition obtained for the samples from the different assays are: DPPH, 36% (PIH); FRAP, 0.04% (PIH); hydroxyl radical scavenging activity, 42.98% (ISO); and inhibition of metal ion chelation, 29.46% (AIH). AIH (79.3%) had the highest ACE-inhibitory activity followed by TIH (75.1%) while PIH (43.0%) had the least. Generally, the hydrolysis process produced hydrolysates with improved antioxidant and ACE-inhibitory properties when compared to the isolate. We conclude that enzymatic hydrolysis with alcalase, pepsin and trypsin may be used to produce M. oleifera seed protein hydrolysates with potential to be used as ingredients for the formulation of functional foods and nutraceuticals.

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