Leafy vegetables fortification enhanced the nutritional profile and reduced the glycemic index of yellow cassava pasta.

Food-to-food fortification of yellow cassava flour with leafy vegetable powders (Amaranthus and Telfairia occidentalis) was employed in this study to develop cassava-vegetable spaghetti-like pasta products (YP, YPA5, YPA10, YPU5, YPU10, YPA5O). The nutritional profile, micronutrient retention, bioaccessibility, starch digestibility and in vitro glycemic index were assessed. The incorporation of leafy vegetable powder enhanced the nutritional quality of the yellow cassava pasta (YCP) products. The fortification increased (up to 3-fold) the protein in fortified YCP, increased the fibre (11%), doubled the ash and increased the beta-carotene (about 7-fold), iron (72%) and zinc contents by 10%. The phenolic content of fluted pumpkin leaf-fortified pasta with 10% leaf powder inclusion (YPU10) was 1100 µg GAE g-1, almost four times higher than that of the unfortified YCP. Leaf powders in the cassava pasta also favoured the retention of micronutrients during cooking and slowed down the starch digestibility. The retention during cooking was up to 91% in YPU10 for beta-carotene with no loss in iron, while the bioaccessibility of beta-carotene was impeded, the zinc retention was high and became significantly more bioaccessible with leaf addition and cooking. The estimated glycemic index of YCP was reduced by 19% and 15% in YPU10 and YPA10, respectively. The inclusion of the vegetables also reduced the glycemic index of the fortified YCP. Thus, adding leafy vegetable powder up to 10% into YCP is a promising approach to both valorise yellow provitamin A biofortified cassava and enhance the nutritional value.

Amino acid composition and antioxidant properties of the enzymatic hydrolysate of calabash nutmeg (Monodora myristica) and its membrane ultrafiltration peptide fractions.

The aim of this work was to determine amino acid composition and in vitro antioxidant activities of Monodora myristica protein hydrolysate and its membrane ultrafiltration peptide fractions. The Alcalase hydrolysate was fractionated using ultrafiltration membranes to produce peptide sizes of <1, 1-3, 3-5, and 5-10 kDa. The results showed that sequential fractionation resulted in higher glycine and glutamic acid and glutamine contents. Analysis of in vitro antioxidant properties showed that fractionation of the M. myristica hydrolysate led to significant (p < .05) improvements in 2,2-diphenyl-1-picrylhydrazyl radical scavenging, metal chelation activity, ferric reducing antioxidant power (FRAP), and hydroxyl (OH) radical scavenging activity. Linoleic acid oxidation was significantly (p < .05) attenuated by the peptide fractions. We conclude that peptide antioxidant activities were significantly (p < .05) improved by membrane fractionation, especially the 3-5 kDa fraction. PRACTICAL APPLICATIONS: The use of protein hydrolysate fractions with potential to prevent oxidation, which can reduce shelf life of foods and cause degenerate diseases due to cell damage is proposed for Monodora myristica. The demand for natural products and negative health issues associated with artificial food ingredients have led to increased consumer preference for natural sources of antioxidants. The protein hydrolysate and membrane fractions produced in this work showed high antioxidant ability that could qualify them to replace toxic synthetic antioxidants in foods. Peptide fractions had better metal chelation than the hydrolysates, which is important because chelation of metal ions can decrease the amount of free iron available to participate in the Fenton reaction and ultimately decrease the formation of toxic free radicals. Incorporation of the peptides into foods will enhance scavenging of toxic free radicals that may form during storage, thereby improving product freshness and shelf life in addition to preventing human degenerative diseases.

Effects of thermal processing on the nutritional and functional properties of defatted conophor nut (Tetracarpidium conophorum) flour and protein isolates.

Conophor nut (Tetracarpidium conophorum) was processed using different heat treatments to explore its full potential as food ingredients. The raw, boiled, and toasted nuts were defatted and the proteins isolated by alkaline solubilization and isoelectric precipitation. The variously processed nuts were analyzed for the proximate and amino acid compositions, and functional properties. The protein contents of the isolate ranges between 86.86 g/100g and 87.74 g/100 g, about 1.5-fold higher than those of the defatted flour samples. The essential amino acids of the isolates ranged between 40.57%-41.55%. Glutamic acid, aspartic acid, and arginine were the most predominant amino acids, while methionine and lysine were the first and second limiting amino acids, respectively. The protein efficiency ratio, biological values as well as the functional properties of the proteins were improved with processing. These properties may enhance the potential use of conophor nut protein isolates as high-quality protein ingredient in food systems.

Development of functional beverages from blends of Hibiscus sabdariffa extract and selected fruit juices for optimal antioxidant properties.

The demand for functional foods and drinks with health benefit is on the increase. The synergistic effect from mixing two or more of such drinks cannot be overemphasized. This study was carried out to formulate and investigate the effects of blends of two or more of pineapple, orange juices, carrot, and Hibiscus sabdariffa extracts (HSE) on the antioxidant properties of the juice formulations in order to obtain a combination with optimal antioxidant properties. Experimental design was carried out using optimal mixture model of response surface methodology which generated twenty experimental runs with antioxidant properties as the responses. The DPPH (1,1-diphenyl-2-picrylhydrazyl) and ABTS [2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)] radical scavenging abilities, ferric reducing antioxidant potential (FRAP), vitamin C, total phenolics, and total carotenoids contents of the formulations were evaluated as a test of antioxidant property. In all the mixtures, formulations having HSE as part of the mixture showed the highest antioxidant potential. The statistical analyzes, however, showed that the formulations containing pineapple, carrot, orange, and HSE of 40.00, 16.49, 17.20, and 26.30%, respectively, produced optimum antioxidant potential and was shown to be acceptable to a research laboratory guidance panel, thus making them viable ingredients for the production of functional beverages possessing important antioxidant properties with potential health benefits.

Kinetics of the inhibition of renin and angiotensin I-converting enzyme by cod (Gadus morhua) protein hydrolysates and their antihypertensive effects in spontaneously hypertensive rats.

BACKGROUND: Cod muscle has a balanced protein profile that contains potentially bioactive amino acid sequences. However, there is limited information on release of these peptides from the parent proteins and their ability to modulate mammalian blood pressure. OBJECTIVE: The aim of this study was to generate cod antihypertensive peptides with potent in vitro inhibitory effects against angiotensin-converting enzyme (ACE) and renin. The most active peptides were then tested for systolic blood pressure (SBP)-reducing ability in spontaneously hypertensive rats (SHRs). DESIGN: Cod protein hydrolysate (CPH) was produced by subjecting the muscle proteins to proteolysis first by pepsin and followed by trypsin+chymotrypsin combination. In order to enhance peptide activity, the CPH was subjected to reverse-phase (RP)-HPLC separation to yield four fractions (CF1, CF2, CF3, and CF4). The CPH and RP-HPLC fractions were each tested at 1 mg/mL for ability to inhibit in vitro ACE and renin activities. CPH and the most active RP-HPLC fraction (CF3) were then used for enzyme inhibition kinetics assays followed by oral administration (200 and 30 mg/kg body weight for CPH and CF3, respectively) to SHRs and SBP measurements within 24 h. RESULTS: The CPH, CF3, and CF4 had similar ACE-inhibitory activities of 84, 85, and 87%, which were significantly (p<0.05) higher than the values for CF1 (69%) and CF2 (79%). Conversely, the CF3 had the highest (63%) renin-inhibitory activity (p<0.05) when compared to CPH (43%), CF1 (15%), and CF4 (44%). CPH and CF3 exhibited uncompetitive mode of ACE inhibition, whereas renin inhibition was non-competitive. Even at a 6.7-fold lower dosage, the CF3 significantly (p<0.05) reduced SBP (maximum -40.0 mmHg) better than CPH (maximum -19.1 mmHg). CONCLUSIONS: RP-HPLC fractionation led to enhanced antihypertensive effects of cod peptides, which may be due to a stronger renin-inhibitory activity.

Effect of peptide size on antioxidant properties of African yam bean seed (Sphenostylis stenocarpa) protein hydrolysate fractions.

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.

Comparison of the physicochemical properties and pasting characteristics of flour and starch from red and white sweet potato cultivars.

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.