Characterisation of phenolic acids,flavonoids, proanthocyanidins and antioxidant activity of water extracts from seed coats of marama bean [Tylosema esculentum] – an underutilised food legume

Freeze‐dried aqueous phenolic extracts with possible application as natural antioxidant functional food ingredients were prepared from marama bean seed coats by extracting with water. Phenolic acids, flavonoids and proanthocyanidins in the extracts were characterised by HPLC/MS. The major flavonoids were the flavanols methyl (epi)afzelechin‐3‐O‐gallate (40%) and methyl (epi)catechin‐3‐O‐gallate (28%), and the major phenolic acid was gallic acid (10%). Proanthocyanidins in the extracts were predominantly prodelphinidins composed of epicatechin‐3‐O‐gallate and epigallocatechin present as major terminal and extension units and epigallocatechin‐3‐O‐gallate and epicatechin present as minor extension unit constituents. The polymer structure was found to be unique compared with other legumes because of the high percentage of galloylated units. Extracts showed a high DPPH free radical scavenging activity (707 μmol TE g^?1), protective effect against AAPH‐induced human red blood cell haemolysis and copper‐catalysed human LDL oxidation suggesting that the extracts may have potential health benefits.     

Effect of γ-irradiation on some physicochemical and thermal properties of cowpea (Vigna unguiculata L. Walp) starch

Previously, we reported that starch-related functional properties of cowpea flours and pastes were modified by 2, 10 and 50 kGy γ-irradiation doses. To elucidate some of the effects of γ-irradiation specifically on cowpea starch as well as the actual contribution of starch to the observed functional modifications at the flour and paste level, starch was isolated from irradiated cowpea flours and pastes and studied using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), Fourier Transform Infra-Red (FTIR) spectroscopy, Rapid Visco-Analyser (RVA) pasting properties, and some functional properties. Pasting (peak, trough, breakdown, final, and setback viscosities) and swelling properties were significantly decreased in a dose-dependent manner. DSC of cowpea starch showed increases in peak gelatinisation temperature with increasing irradiation dose. SEM (2500×) microphotographs showed that up to 50 kGy irradiation did not present any visible physical effect on the cowpea starch granule. FTIR indicated that starch granule surface order (crystallinity) was not affected by the irradiation doses employed.     

Susceptibility to Cronobacter sakazakii decreases with increasing age in neonatal CD-1 mice

Neonatal, premature, or very low birth weight infants fed reconstituted powdered infant formula contaminated with Cronobacter (Enterobacter sakazakii) may develop infections resulting in severe outcomes such as septicemia, necrotizing enterocolitis, meningitis, or death. Infants who recover from infection may have morbidities such as hydrocephalus, mental retardation, or developmental delays. Although increasing age appears to reduce susceptibility to Cronobacter infection, it is not known at what age or why these infants become less susceptible. Our study objectives were to compare the susceptibilities of neonatal mice of different ages to Cronobacter sakazakii infection. Timed-pregnant CD-1 mice were allowed to give birth naturally. Neonatal mice were orally gavaged at postnatal days (PNDs) 1.5, 5.5, and 9.5 with a single dose of vehicle or 10(3), 10(7), or 10(10) CFU/ml C. sakazakii strain MNW2 in reconstituted powdered infant formula. Pups were euthanized 7 days after challenge. Brains, livers, and ceca were excised and analyzed for C. sakazakii invasion, and blood was collected for serum amyloid A analysis as a biomarker of infection. C. sakazakii invasion was age dependent; the pathogen was isolated from brains, livers, and ceca of neonatal mice treated at PNDs 1.5 and 5.5 but not from those of pups treated at PND 9.5. C. sakazakii was more invasive at PND 1.5 in brains than in livers and ceca and was isolated from 22, 14, and 18% of these tissue samples, respectively. Serum amyloid A was detected in only one treated neonate. Mortality was observed only in neonates treated at PND 1.5. In conclusion, neonatal mice had a time-dependent susceptibility to C. sakazakii infection, with resistance increasing with increasing age.     

Nutritional quality and antioxidant activity of marama-sorghum composite flours and porridges

Marama bean, an underutilised legume in southern Africa, is a good source of protein, fat and phenolic compounds, the latter known to have potential health benefits. Marama flours, sorghum meal, marama-sorghum composite flours and porridges were analysed for proximate composition, amino acid composition, energy value, fatty acid composition, total phenolic content and antioxidant activity. Compositing sorghum meal (70%) with marama flours (30%) significantly increased the protein and fat contents in flours and porridges. Energy values of marama-sorghum composite porridges were 11-24% higher than sorghum porridge. Lysine content was 3-4 times higher in marama-sorghum porridges than in sorghum porridge. There was an increase in oleic acid as sorghum meal was composited with marama flour. There was a positive correlation between the total phenolic content and antioxidant activity in all samples. Use of marama flour in sorghum composite flours and porridges improved the nutritional quality and antioxidant activity.     

Influence of salt and pH on the solubility and structural characteristics of transglutaminase-treated wheat gluten hydrolysate

Hydrolyzed wheat gluten (GH, 77–85% protein) was prepared by limited chymotrypsin digestion at 37 °C for 4 h (degree of hydrolysis = 6.4%) and 15 h (degree of hydrolysis = 10.3%). Microbial transglutaminase (MTGase) treatment (55 °C for 1 h, or 5 °C for 18 h) effect on the solubility and structural characteristics of GH was examined under selected food processing conditions (pH 4.0–7.0, 0–0.6 M NaCl). The MTGase treatment increased solubility of GH by 3–29-fold (P < 0.05) within pH 4.0–7.0. Addition of 0.6 M NaCl or changing the conditions of MTGase incubation did not significantly alter solubility characteristics of GH. The MTGase treatment decreased surface hydrophobicity, and increased carboxyl groups in GH, suggesting cross-linking and deamidation. Fluorescence and UV spectra attributed the improved GH solubility to MTGase-induced polar environment, and partial masking of some nonpolar aromatic amino acids possibly due to high-molecular-weight polypeptides formed.