28 research outputs found
Phase Behaviour Of Oat β-Glucan/Sodium Caseinate Mixtures
No full textOat β-glucan is a water soluble polysaccharide which has been approved as a functional bioactive ingredient. In this thesis, β-glucan was successfully isolated from oat flour and samples of different molecular weights were produced. The structural features and molecular weights(Mw) were characterized by 13C–NMR spectroscopy and high performance size-exclusion chromatography, respectively. The rheological properties and microstructure of aqueous oat β-glucan solutions were investigated by rheometry and atomic force microscopy (AFM),respectively. The samples with β-glucan content between 78-86 % on a dry weight basis had Mw, intrinsic viscosity ([η]) and critical coil overlap concentration (c*) in the range of 142 - 2800 x 103 g/mol, 1.7 - 7.2 dL/g and 0.25 - 1.10 g/dL, respectively. The flow and viscoelasticvbehaviour was highly dependent on Mw and on the concentration of the β-glucan solutions. AFM images revealed the formation of cluster or aggregates linked via individual polymer chains scattered heterogeneously throughout the system. The aggregate size was also dependent on molecular weight of the samples and influences the rheological behaviour of β-glucan solutions. The isothermal phase behaviour at 5 oC of β-glucan/sodium caseinate mixtures were
investigated by means of phase diagram construction, rheometry, electrophoresis and fluorescence microscopy. Phase diagrams indicated that the compatibility of the β-glucan/sodium caseinate system increases as β-glucan Mw decreases. Images of the mixtures taken at various
biopolymer concentrations revealed phase separation with the presence of β-glucan aggregates,whose size depends on Mw and concentration. At the same protein concentration in the mixtures, the viscosity increases with increasing Mw and concentration of β-glucan. However, the results also revealed that in the state of thermodynamic equilibrium with comparable polymer concentrations in mixture, the lower Mw samples yielded similar or higher viscosity. At equivalent hydrodynamic volume of β-glucan component in the mixture, all the samples
exhibited similar viscosity/flow behaviour. A deviation dependent on the protein concentration
was observed for the high Mw sample in the concentrated regime due to the size of the β-glucan aggregates formed. Results demonstrate that by controlling the structural features of β-glucan in mixture with sodium caseinate, informed manipulation of rheological properties in these systems can be achieved
Polysaccharide determination in protein/polysaccharide mixtures for phase-diagram construction
No full textThe effect of protein removal from protein–polysaccharide mixtures on the determination of total
sugar concentration for phase-diagram construction was explored by response surface methodology.
Phenol–sulphuric acid method was used to estimate the total sugar concentration whereas phase separation
and microstructure of biopolymers in the mixtures were probed by means of fluorescent microscopy.
All the factors studied (trifluoroacetic acid (TFA) volume, protein concentration, precipitation time) had
significant influence on the polysaccharide recovery from the mixtures. The overall pattern of protein
precipitation with TFA was also found to highly depend on protein–time interactions. Images taken at different
mixture concentrations and with two different filter sets revealed a phase-separated system with
the guar gum domains surrounded by a continuous protein phase. Experimental measurements as well as
microscopical evidence suggests that, for greater than 60% polysaccharide recovery (±6% error), the protein
content in the mixtures should be <∼5.5% (w/v) with less than 0.5mL TFA combined with more than
30 minrest under the influence of TFA. The results of the present investigationshowedthatwhenattempting
to construct phase diagram of mixed biopolymer systems the equilibrium phases must be diluted to
a protein content <∼5% (w/v) before TFA treatment if the maximum polysaccharide concentration is to
be determined
Total phenol content and antioxidant activity of fruit smoothies during storage
No full textA fruit smoothie is described as a 100 percent blend of a variety of fruits with no added sugar or additives, no added water and not made from concentrates. Phenols are compounds which contain a hydroxyl group (OH) bonded to benzene (aromatic) rings. Recently, phenols in foods have gained much attention owing to their antioxidant activity and possible beneficial implications in human health such as prevention of certain cancers and cardiovascular diseases1. Total phenols (TP) and antioxidant activity of three fruit smoothies (Blackberries, Raspberry and Boysenberry (BRAB), Mango and Passion fruits (MAP) and Blackcurrant, Acerola cherries and Rosehips (BACAR)) were determined during storage by Folin-Ciocalteu and ferric reducing antioxidant power (FRAP) assays respectively. All measurements were performed at least in three replicates. TP ranged from 1943±70.7 to 2692±21.6 mg gallic acid equivalent/L whereas FRAP ranged from 43217±1225 to 126125±2887 µmol Trolox equivalent/L for the three smoothies on opening. Both TP and antioxidant activity were highest in BACAR, followed by BRAB and lastly MAP. The differences in TP and antioxidant activity of these smoothies could be attributed to their respective fruit ingredients. The smoothies had significant decrease (p 0.05). There was a higher loss in TP and antioxidant activity when smoothies were opened, part sampled and the remaining stored at 4 0C for four consecutive days. It is therefore important that once a smoothie is opened, it should be consumed within the stated four days and should be quickly closed to minimize oxygen entry which causes the loss of antioxidants. However, the study revealed that the smoothies had high TP and antioxidant activity even during shelf-life at 4 °C which implies that consumption of smoothies may give considerable antioxidant benefits. Correlation between TP and antioxidant activity was strong and highly significant (r = 0.890, p < 0.0001)
Modeling the Kinetics of Potassium Diffusion in Estima Potato under Different Leaching Conditions
No full textThe diffusion of potassium in potato (Solanum tuberosum) at different leaching conditions was investigated. Two modes of pretreatment of potato samples (cubes and spheres) by preheating to 80°C and leaching at temperatures of 20-80°C were performed using a temperature- and agitation-controlled batch extractor. A Fickian model incorporating the effective diffusion coefficient (Deff), partition coefficient (K) between the solute concentration in the potato and medium, and mass transfer coefficient (kl) was developed to simulate and predict the fraction of potassium leached from the potato at any temperature. Results showed significant reduction in activation energies from 92 to 25.02 kJ/mol for cubes and from 75.02 to 13.40 kJ/mol for spheres culminating in higher extraction rates when samples were preheated to 80°C. The Deff, K, and kl values obtained were in the range of 0.02−7.33×10−9 m2/s, 0.63−8.00×10−2, and 0.01333.00×10−4 m/s, respectively. The kinetic parameters showed a change in slope or discontinuity in the gelatinization temperature range as a function of temperature, an indication of a change in the diffusional matrix. The optimum operating conditions were 80°C preheating and leaching at temperatures up to 50°C. The proposed mathematical model offered a satisfactory description of both dynamic and equilibrium mass transfers of potassium by adequately predicting the fraction of potassium from potato cubes and spheres. The present findings could be useful in the pretreatment of potato for renal patients
) seed flour
No full textThe physicochemical and functional properties of dried okra seed flour of two genotypes Agbagoma and Balabi were evaluated. The samples Agbagoma and Balabi had 8.90%–9.00% moisture, 16.80%–17.40% protein, 47.80%–48.00% fat, 7.70%–7.80% ash, and 18.20%–18.40% carbohydrate. The mean values of functional properties revealed significant differences (p < .05) between okra seed flour samples studied. The samples’ bulk density range was 0.80–0.83 g/ml. Water absorption capacity and oil absorption capacity ranged from 511.65% to 504.32% and 88.38 to 160.67%, respectively. The solubility was 14.10% for Agbagoma and 10.97% for Balabi, whereas swelling power was 16.37% and 14.68% for Agbagoma and Balabi, respectively. All pasting properties except peak time and pasting temperature of Agbagoma seed flour were higher than those of Balabi seed flour. The study revealed that dried okra seed flour is rich in nutrients, which could be used for baking and fortification of foods
Phase behaviour of oat β-glucan/sodium caseinate mixtures varying in molecular weight
No full textThe isothermal phase behaviour at 5 °C of mixtures of sodium caseinate and oat β-glucan isolates varying in molecular weight (MW) was investigated by means of phase diagram construction, rheometry, fluorescence microscopy and electrophoresis. Phase diagrams indicated that the compatibility of the β-glucan/sodium caseinate system increases as β-glucan MW decreases. Images of mixtures taken at various biopolymer concentrations revealed phase separated domains. Results also revealed that at the state of thermodynamic equilibrium, lower MW samples yielded considerable viscosity in the mixture. At equivalent hydrodynamic volume of β-glucan in the mixtures, samples varying in molecular weight exhibited similar flow behaviour. A deviation dependent on the protein concentration was observed for the high MW sample in the concentrated regime due to the size of β-glucan aggregates formed. Results demonstrate that by controlling the structural features of β-glucan in mixtures with sodium caseinate, informed manipulation of rheological properties in these systems can be achieved
Assessing the Association between Nutritional Status and Asymptomatic Malaria Parasitaemia of Children Under Five Years in Ghana
No full textAbstract Background: Undernutrition and malaria are major public health challenges and are the main causes of morbidity and mortality in low and/or middle income settings. To fulfil a research need, this study was conducted to determine the association between nutritional status including anaemia and asymptomatic malaria parasitaemia in children under five years old. Methods: This was a communitybased cross-sectional study, conducted in four communities from randomly selected regions in Ghana. Blood samples and anthropometric measures of 250 children were collected for analyses. Parents of children involved in the study, also completed a questionnaire. Results: The prevalence of asymptomatic malaria parasitaemia was 14.8% and anaemia (Hb < 11.0 g/dl) was 58.8%. Binomial logistic regression analysis predicted no significant association between asymptomatic malaria parasitaemia and weight-for-height z-scores (p = 0.592; OR = 1.234; 95% CI: 0.573-2.658), height-for-age z-scores (p = 0.169; OR = 0.651; 95% CI: 0.353-1.200) and weight-for-age z-scores (p = 0.832; OR = 1.094; 95% CI: 0.478-2.504). However, asymptomatic malaria parasitaemia was a significant predictor of anaemia (p = 0.04; OR = 2.419; 95% CI: 1.041-5.622) and ages beyond two years were risk factors for anaemia. Stunting however was associated with a significant lower odds of being anaemic (p = 0.003; OR = 0.484; 95% CI: 0.301-0.778). Conclusions: Asymptomatic malaria parasitaemia may have no effect on anthropometric measurements of young children or asymptomatic malaria parasitaemia have no significant influence on anthropometric measures of young children in the short or long term. However, children with asymptomatic malaria parasitaemia are more likely to be anaemic especially after two years. Stunting however may reduce the risk of anaemia in children. This suggests that, asymptomatic malaria parasitaemia may be a contributory factor to the existing burden of anaemia in children from developing countries. Efforts should therefore be made to screen for asymptomatic malaria parasitaemia during routine growth monitoring sessions
Rheological and microstructural investigation of oat β-glucan isolates varying in molecular weight
No full textThe rheological properties and microstructure of aqueous oat β-glucan solutions varying in molecular weight were investigated. The structural features and molecular weights (MW) were characterized by 13C NMR spectroscopy and high performance size-exclusion chromatography (HPSEC), respectively. The microstructure of the β-glucans dispersions was also examined by atomic force microscopy (AFM). The samples with β-glucan content between 78 and 86% on a dry weight basis had MW, intrinsic viscosity ([η]) and critical concentration (c) in the range of 142-2800×103g/mol, 1.7-7.2dl/g and 0.25-1.10g/dl, respectively. The flow and viscoelastic behaviour was highly dependent on MW and on the concentration of the β-glucans dispersions. Pseudoplastic behaviour was exhibited at high concentrations and Newtonian behaviour was evident at low concentrations. At the same concentration, the viscosity was higher for higher MW samples. The Cox-Merz rule was applicable for the lower molecular weight samples at higher concentrations whereas the high molecular weight sample deviated at concentrations greater than 1.0%, w/v. The mechanical spectra with variation of both MW and concentration were typical of entangled biopolymer solutions. AFM images revealed the formation of clusters or aggregates linked via individual polymer chains scattered heterogeneously throughout the system. The aggregate size increased with the molecular weight of the samples investigated and has been linked to the rheological behaviour of the samples. © 2011
