The Effect of Heat Treatment on Anilinonaphthalene-8-Sulphonate Binding to Rapeseed Albumin (Napin)

Protein surface hydrophobicity can be measured by the fluorescent probe method. The effect of heat treatment on Brassica napus (rapeseed) albumin (napin) interactions with a fluorescent probe, anilinonaphthalene-8-sulphonic acid (ANS) was investigated by fluorescent titration. Upon heating to 100°C for 30 min the number of napin binding sites for ANS (n) increased from 5(±0·7) to 13(±0·5) moles of ANS bound per mole of protein. The ANS-protein dissociation constant (Kd) was 2·0(±0·4)×10^-6 M for the unheated protein and 10·4(±0·1)×10^-6 M for heat-denatured napin. There was also a blue shift in the fluorescence emission spectrum maximum for denatured napin–ANS complex consistent with an increase in the hydrophobicity of the ANS binding sites in the denatured protein. The characteristic fluorescence increase for heat-denatured albumin–ANS mixtures is therefore due to an increase in the number, binding affinity and hydrophobicity of binding sites. Heat treatment of napin leads to the appearance of additional surface hydrophobic sites in the denatured protein. © 1997 SCI.     

Effect of pH and Ionic Strength on the Heat Stability of Rapeseed 12S Globulin (Cruciferin) by the ANS Fluorescence Method

The heat stability of rapeseed 12S globulin (cruciferin) was examined using 8-anilinonaphthalene-1-sulphonic acid (ANS) as a fluorescence probe. Heating cruciferin (0·06–0·3 mg ml⁻¹ in 10 mM glycyl–glycyl piperizine buffer, pH 7·0, with 0·1–1·0 M NaCl) for 20 min increased its hydrophobicity as monitored by ANS fluorescence measurements. The mid-point temperature for the heat effect (T_m) increased linearly with increasing solvent pH (T_m (°C)=4·16 pH+41 (μ=0.1)) or sodium chloride concentration (T_m (°C)=14·7 [NaCl]+71 (pH=7·0)). The range of T_m values for cruciferin was 45–96°C. At 20°C cruciferin was unstable at pH<3·0 but relatively stable under alkaline conditions (pH 8–10). Though possessing an oligomeric structure, cruciferin appears to heat denature in accordance with the two-stage deactivation model for simple globular proteins.     

Impact of enzyme preparation and degree of hydrolysis on peptide profile and nitrogen solubility of sodium caseinate hydrolysates

The solubility of casein ingredients is limited under certain pH conditions. Therefore, sodium caseinate (NaCN) was hydrolysed at laboratory scale with four enzyme preparations (Alcalase, Prolyve, FlavorPro Whey and pepsin) yielding hydrolysates having degree of hydrolysis (DH) values between 0.19 ± 0.11 and 19.25 ± 0.73%. The nitrogen solubility index (NSI) over the pH range 2.0–8.0 was affected by (i) the specificity of the enzyme preparation, (ii) the DH and (iii) the presence of unhydrolysed NaCN within the hydrolysate. The trends observed at laboratory scale (<5 L) were also seen with the semi‐pilot‐scale (300 L) hydrolysates generated with Alcalase and FlavorPro Whey. Removal of unhydrolysed NaCN from the FlavorPro Whey hydrolysate using a 5‐kDa ultrafiltration (UF) membrane increased NSI. This study has highlighted the importance of carefully selecting the proteolytic preparation along with the DH to design casein‐based ingredients with enhanced technofunctional properties.     

Antimicrobial interactions of microbial species involved in the fermentation of cassava dough into agbelima with particular reference to the inhibitory effect of lactic acid bacteria on enteric pathogens

Lactic acid bacteria, Bacillus species and yeasts are involved in the fermentation of cassava dough into agbelima. Microbial interactions within and between these groups of microorganisms were investigated in addition to the survival of five enteric pathogens inoculated into agbelima under various conditions. Nine out of 10 cultures of lactic acid bacteria isolated at the end of agbelima fermentation showed inhibitory effect against 10 cultures of lactic acid bacteria isolated at the start of fermentation. Only 3 out of 10 isolates of Bacillus subtilis were inhibited by 10 isolates of lactic acid bacteria tested. No interactions were observed between yeasts and the lactic acid bacteria, whereas three of the Bacillus isolates showed inhibitory effects against the yeasts. Twelve isolates of Lactobacillus plantarum tested inhibited the growth of an isolate each of Lactobacillus fermentum and Lactobacillus brevis but none tested positive for bacteriocin production. The antimicrobial effect of the lactic acid bacteria was attributed to acid production. In fermenting cassava dough, enteric pathogens survived to different extents depending on pH and their sensitivity to acids. Vibrio cholerae C-230, Salmonella typhimurium 9 and Salmonella enteritidis 226 were not detectable in 10 g of sample after 4 h when inoculated into the 48-h fermented product, agbelima, whereas Shigella dysenteriae 2357T and Escherichia coli D2188 were detectable up to 8 h in the product.     

Modification of Stearidonic Acid Soybean Oil by Immobilized Rhizomucor miehei Lipase to Incorporate Caprylic Acid

Immobilized sn-1,3 specific Rhizomucor miehei lipase (RML) was used to catalyze the incorporation of caprylic acid (C8:0) into high stearidonic acid (SDA, C18:4ω3) soybean oil (SDASO) to form structured lipids (SL). The effects of type of biocatalyst (Celite-, octyl-Sepharose-, and Duolite-immobilized RML) and reaction temperature (30, 40, 50, and 60 °C) on acidolysis and acyl migration were studied. Celite-immobilized RML (C-RML) at 50 °C maximized C8:0 incorporation and minimized acyl migration compared to other treatments. Optimal levels of substrate molar ratio (C8:0 to SDASO), incubation time, and enzyme load for SL synthesis by C-RML at 50 °C was determined by response surface methodology to be 6:1, 24 h, and 20 % weight of substrates, respectively. This optimum treatment was scaled-up in hexane or solvent-free reaction media using SDASO or an SDA-enriched acylglycerol mixture as substrate. This yielded various SL with C8:0 contents ranging from 17.0 to 32.5 mol% and SDA contents ranging from 20.6 to 42.3 mol%. When digested, these SL may deliver C8:0 for quick energy and SDA for heart health making them potentially valuable for medical and nutraceutical applications.     

Comparison of cigarette and water pipe smoking among female university students in Egypt.

This study investigated behavioral and sociodemographic factors associated with tobacco use among female university students patronizing water pipe cafes in Cairo, Egypt. We interviewed two groups of female university student smokers (100 and 96 students from a public and a private university, respectively). The interviews took place in nine water pipe cafes near the two universities. A logistic regression model was developed to analyze the relationship between tobacco-related knowledge and beliefs and the choice between smoking water pipe or cigarettes. Among these smokers, 27% smoked cigarettes only, 37.8% smoked water pipe only, and 35.2% smoked both types of tobacco. Most of the water pipe smokers (74.1%) preferred this method because they believe it to be less harmful than smoking cigarettes. More than half of the subjects were encouraged to start smoking by other females (56.6%). Curiosity was a significant factor for initiation (OR = 2.8, 95% CI = 1.3-6.2, p<.01). We found no significant differences between water pipe and cigarette smokers regarding current age, age at initiation, quit attempts, knowledge about the hazards of smoking, wanting to be fashionable, or smoking with friends. About one in four (23.7%) attempted to quit, with health cited as a major reason. An urgent need exists for correction of the misperception among this study population that water pipe smoking is safe and less harmful than cigarette smoking.     

The microbiology of Ghanaian cocoa fermentations analysed using culture-dependent and culture-independent methods

Export of cocoa beans is of great economic importance in Ghana and several other tropical countries. Raw cocoa has an astringent unpleasant taste and a spontaneous fermentation is the first step in a process leading to cocoa beans with the characteristic cocoa flavour and taste. The microbiology of Ghanaian cocoa fermentations was investigated using culture-dependent and culture-independent methods. Samples were collected at 12 hour intervals during 96-144 hour tray and traditional heap fermentations. Yeast, Lactic Acid Bacteria (LAB), Acetic Acid Bacteria (AAB) and Bacillus spp. were enumerated on suitable substrates and identified using phenotypic and molecular methods. The yeast and bacterial micro-populations involved in the cocoa fermentation were further investigated using the culture-independent method Denaturing Gradient Gel Electrophopresis (DGGE). A microbiological succession was observed during the fermentations. At the onset of fermentation yeasts were the dominating microorganisms. Lactic Acid Bacteria became dominant after 12-24 h of fermentation and remained predominant throughout the fermentations with AAB reaching high counts in the mid phase of fermentation. Bacillus spp. were only detected during heap fermentations where they reached high numbers during the later stages of fermentation. Hanseniaspora guilliermondii was the predominant yeast during the initial phase and Pichia membranifaciens during the later phases of fermentation. A number of other yeast species including three putatively undescribed species were isolated during the fermentations. Lactobacillus fermentum was the dominant LAB in most samples. Several other LAB including Lactobacillus plantarum, Leuconostoc pseudomesenteroides, Leuconostoc pseudoficulneum, Pediocococcus acidilactici and a putatively undescribed LAB species were detected during the fermentations. Acetobacter syzygii, Acetobacter pasteurianus and Acetobacter tropicalis were the predominant AAB in all investigated fermentations. During the later stages of heap fermentation Bacillus licheniformis and occasionally other Bacillus spp. were detected in high numbers. In general the culture-based findings were confirmed using DGGE. However, DGGE indicated that Lc. pseudoficulneum plays a more important role during the fermentation of cocoa than expected from the culture-based findings as it yielded a strong band in most DGGE fingerprints. Cluster analysis of the DGGE fingerprints revealed that the DGGE fingerprints clustered according to fermentation site. Within each fermentation site the profiles clustered according to fermentation time. The DGGE method seems to offer a relatively fast and reliable tool for studying yeast and bacterial dynamics during cocoa fermentations.     

Fatty Acid Composition of Irvingia gabonensis and Treculia africana Seed Lipids and Phospholipids

Lipid compositions of two non-conventional oilseeds (Irvingia gabonensis and Treculia africana) were studied. Total lipids were extracted by the Folch method and phospholipids were isolated by solid phase extraction. Fatty acid compositions of total lipids and phospholipids were determined by gas chromatography. Phospholipid classes and tocopherols were quantified by HPLC. The major fatty acids in I. gabonensis seed total lipids were myristic (41.4–48.9 %) and lauric (39.8–46.8 %) while those in T. africana seed were linoleic (29.1–31.4 %) and oleic (22.9–25.9 %). The principal fatty acid at the sn-2 position of I. gabonensis seed triacylglycerols was myristic (49.5 %) while that of T. africana was linoleic (50.6 %). Phospholipid content of crude T. africana seed oil was 3.3 % and that of I. gabonensis was 0.1–0.3 %. The composition and distribution of saturated fatty acids in I. gabonensis seed lipids suggest that it may contribute to cardiovascular disease risk factors among the Igbo people in Nigeria that use the seed as food ingredient.     

Removal of nitrate in raw water using a vertical roughing filter with an external carbon source

High nitrate concentration in water endangers health to both humans and livestock. The aim of this research was to investigate the efficacy of a roughing filter enhanced by an external carbon source in removing nitrate in raw water. Two upward vertical roughing filters in series were used—a vertical roughing filter with ethanol as a carbon source (VRF_wt) and a vertical roughing filter without a carbon source (VRF_wo). The average nitrate removal efficiency in a VRF_wt was 88%, 70% and 83%, at carbon:nitrogen ratios (C/N ratio) of 1.05, 1.08 and 1.1, respectively. The average chemical oxygen demand (COD) removal efficiency in the VRF_wt was 75%, 43% and 46% at C/N ratios of 1.05, 1.08 and 1.1, respectively. The total average reduction of dissolved oxygen (DO) in the VRF_wt at C/N ratios of 1.05, 1.08 and 1.1 was 42%, 54% and 51%, respectively, while the drop in the VRF_wo was 17%, 18% and 17%. The VRF_wt showed a high potential for removing nitrate in raw water. Therefore, when the VRF_wt is applied at large scale, it would improve access to water sources that were previously declared unacceptable by many water utilities due to excessive nitrate concentrations.