Kharidah Muhammad

Antioxidant activities and phenolics content of eight species of seaweeds from North Borneo

The antioxidant activity of eight edible species of Malaysian North Borneo seaweeds obtained from Sabah waters (Kudat, Tanjung Aru and Semporna) consisting of three red seaweeds (Eucheuma cottonii, E. spinosum and Halymenia durvillaei), two green seaweeds (Caulerpa lentillifera and C. racemosa) and three brown seaweeds (Dictyota dichotoma, Sargassum polycystum and Padina sp.) were determined. Methanol and diethyl ether were used as extraction solvent. The antioxidant activities were determined by two methods, TEAC (trolox equivalent antioxidant capacity) and FRAP (ferric reducing antioxidant power) assays. The total phenolic content of the extract was determined according to the Folin–Ciocalteu method and results were expressed as phloroglucinol equivalents. The methanolic extracts of green seaweeds, C. lentillifera and C. racemosa, and the brown seaweed, S. polycystum showed better radical-scavenging and reducing power ability, and higher phenolic content than the other seaweeds. The TEAC and FRAP assays showed positive and significantly high correlation (R2 = 0.89). There was a strong correlation (R2 = 0.96) between the reducing power and the total phenolic content of the seaweeds methanolic dry extracts. These seaweeds could be potential rich sources of natural antioxidants.

Effects of isolation technique and conditions on the extractability, physicochemical and functional properties of pigeonpea (Cajanus cajan) and cowpea (Vigna unguiculata) protein isolates. I. Physicochemical properties

Physicochemical properties of pigeonpea and cowpea protein isolates were determined as a function of extraction technique and pH of the extracting medium. Protein extractability by the isoelectric point precipitation (IP) technique was positively correlated within the pH of the NaOH solution used in the pH range 8.5–12.5. The micellization (MP) technique extracted significantly (P<0.05) less protein than the IP technique when extraction pH of the NaOH was 9.5 or higher, and 10.5 or higher from cowpea and pigeonpea, respectively. The subunit composition and electrical mobility of the isolates were not affected by extraction technique and pH conditions. However, it was observed that the IP isolate extracted at pH 12.5 had the lowest proportion of hydrophilic amino acids, suggesting that the pH of the extracting medium exerted a major influence on the hydrophilicity of the isolates. Pigeonpea MP isolate exhibited significantly (P<0.05) higher exposed hydrophobicity than the IP isolates except for those extracted at pH 9.5 and 10.5. However, the cowpea MP isolate exhibited significantly lower exposed hydrophobicity than the IP isolate extracted at pH 8.5 but this was higher than the rest of the IP isolates. For IP isolates, an inverse relationship was apparent between the extraction pH and hydrophobicity. The MP isolates from both legume seeds were significantly lighter in colour than the corresponding IP isolates and, for the latter, the lightness value (L) was inversely correlated with extraction pH. Differential scanning calorimetry showed that the MP isolates exhibited higher transition enthalpy (ΔH) than the IP. For the IP isolates, ΔH decreased with increasing extraction pH.

Effect of crosslinking reagents and hydroxypropylation levels on dual-modified sago starch properties

Chemical modification is usually carried out to overcome the unstable properties of native sago starch and improve its physical properties during processing. In this study, dual-modification of sago starch was carried out. The first stage of modification was hydroxypropylation, using propylene oxide at levels ranging from 6 to 12%. This was followed by crosslinking, using three different types of crosslinking agents: a mixture of sodium trimetaphosphate (STMP) and sodium tripolyphosphate (STPP), phosphorus oxychloride and epichlorohydrin. Through hydroxypropylation, it was found that there was a significant increase in molar substitution which in turn induces an increase in crosslinking and this was seen from the marked increase in phosphorus content and degree of substitution. This was accompanied by a significant decrease in paste clarity, swelling power and solubility compared to that of the native starch. Starch that was hydroxypropylated with 10–12% propylene oxide and crosslinked by a mixture of 2% STMP and 5% STPP produced modified starch with the most desirable properties in that it exhibited no viscosity breakdown, high acid resistance, high freeze-thaw stability and improved gel texture.

Effect of pH on phosphorylation of sago starch

Sago starch, in a semidry state was phosphorylated with 2% sodium trimetaphosphate (STMP), 5% sodium tripolyphosphate (STPP) singly, and in combination at pH levels between 6 and 11. As the reaction pH was increased from 6 to 11, the degree of phosphorylation was observed to decrease from 0.186 to 0.083% P with STPP, except at pH 9 where the degree of phosphorylation was increased to 0.224% P. In the case of STMP, the degree of phosphorylation increased from 0.066 to 0.119% P as reaction pH was increased from 6 to 10. In the reactions using a mixture of STPP and STMP, the P content decreased from 0.320 to 0.115% when a similar range of pH was employed. At the reaction pH of 9, a starch phosphate obtained using STPP exhibited low hot paste viscosity but high cold paste viscosity and shear stability when cooked at 95°C. Treatment of sago starch with a mixture of STPP and STMP yielded the best starch phosphate at the reaction pH of 9.5 which showed lower hot paste viscosity and much higher cold paste viscosity than that of sago starch phosphates prepared at pH 9 using STPP. Paste clarity measurements of the phosphorylated starches indicated that cross-linking accelerated rapidly above pH 8 with STMP, above pH 9 with STPP, and above pH 6 with a mixture of the two.

Comparison of Cardiovascular Protective Effects of Tropical Seaweeds, Kappaphycus alvarezii, Caulerpa lentillifera, and Sargassum polycystum, on High-Cholesterol/High-Fat Diet in Rats

This study was designed to investigate the comparative in vivo cardiovascular protective effects of red, green, and brown tropical seaweeds, namely, Kappaphycus alvarezii (or Eucheuma cottonii), Caulerpa lentillifera, and Sargassum polycystum, in rats fed on high-cholesterol/high-fat (HCF) diets. Male Sprague-Dawley rats (weighing 260-300 g) on the HCF diet had significantly increased body weight, plasma total cholesterol (TC), plasma low-density lipoprotein cholesterol (LDL-C), plasma triglycerides (TG), lipid peroxidation, and erythrocyte glutathione peroxidase (GSH-Px) and superoxide dismutase levels after 16 weeks. Supplementing 5% seaweeds to HCF diet significantly reduced plasma TC (-11.4% to -18.5%), LDL-C (-22% to -49.3%), and TG (-33.7% to -36.1%) levels and significantly increased HDL-C levels (16.3-55%). Among the seaweeds, S. polycystum showed the best anti-obesity and blood GSH-Px properties, K. alvarezii showed the best antihyperlipemic and in vivo antioxidation effects, and C. lentillifera was most effective at reducing plasma TC. All seaweeds significantly reduced body weight gain, erythrocyte GSH-Px, and plasma lipid peroxidation of HCF diet rats towards the values of normal rats.

Influence of altered solvent environment on the functionality of pigeonpea (Cajanus cajan) and cowpea (Vigna unguiculata) protein isolates

Functional properties of pigeonpea and cowpea isolates were determined as a function of pH and NaCl concentrations. At low pH, nitrogen solubility decreased with increasing NaCl concentration whereas, at high pH, it increased. Addition of NaCl to the solvent medium resulted in a marginal improvement and a significant improvement, in the emulsifying activity and emulsion stability of pigeonpea isolate, respectively. The above treatment decreased these properties for the cowpea isolate. Varying both the pH and NaCl concentrations resulted in significant improvements in the emulsifying properties of the isolates relative to the control treatment. NaCl concentrations higher than 0.1 M significantly (P<0.05) increased the expansion of pigeon and cowpea protein–stabilized foams but reduced foam stability, and adjusting pH from 2 to 8 improved foam expansion but decreased foam stability. Varying both the pH and salt concentration had similar effects on the foaming properties of the isolates. The least gelation concentration (LGC) of the isolates decreased with increasing salt concentration. Adjusting the pH to values away from the apparent isoelectric point, elicited similar responses in LGC. In 0.5 M NaCl solution, adjusting the pH to 2, 6 and 8 resulted in significant reductions in LGC relative to the distilled water protein suspensions.

Combination of saponification and dispersive liquid-liquid microextraction for the determination of tocopherols and tocotrienols in cereals by reversed-phase high-performance liquid chromatography.

A simple sample preparation technique coupled with reversed-phase high-performance liquid chromatography was developed for the determination of tocopherols and tocotrienols in cereals. The sample preparation procedure involved a small-scale hydrolysis of 0.5g cereal sample by saponification, followed by the extraction and concentration of tocopherols and tocotrienols from saponified extract using dispersive liquid-liquid microextraction (DLLME). Parameters affecting the DLLME performance were optimized to achieve the highest extraction efficiency and the performance of the developed DLLME method was evaluated. Good linearity was observed over the range assayed (0.031-4.0μg/mL) with regression coefficients greater than 0.9989 for all tocopherols and tocotrienols. Limits of detection and enrichment factors ranged from 0.01 to 0.11μg/mL and 50 to 73, respectively. Intra- and inter-day precision were lower than 8.9% and the recoveries were around 85.5-116.6% for all tocopherols and tocotrienols. The developed DLLME method was successfully applied to cereals: rice, barley, oat, wheat, corn and millet. This new sample preparation approach represents an inexpensive, rapid, simple and precise sample cleanup and concentration method for the determination of tocopherols and tocotrienols in cereals.

Effect of drying time, bean depth and temperature on free amino acid, peptide‐N, sugar and pyrazine concentrations of Malaysian cocoa beans

The effect of drying time on free amino acid, peptide-N, sugar and pyrazine concentrations as well as the influence of bean depth and temperature on these compounds during cocoa drying was studied. Drying time, bean depth and temperature significantly decreased the concentration of free amino acids, peptide-N, total reducing sugars and sucrose and increased the concentration of trimethyl-, tetramethylpyrazine and total pyrazines in cocoa beans. The best drying treatment was obtained at the combination of bean depth/drying temperature of 8.3 cm/40 °C. This was based on the fact that it produced significantly high concentrations of hydrophobic free amino acids, peptide-N and total reducing sugars and significantly low concentration of trimethyl-, tetramethylpyrazine and total pyrazines. Drying treatment of 1.5 cm/60 °C significantly produced the lowest concentration of free amino acids, peptide-N and total reducing sugars and the highest concentration of pyrazines.

Changes in urocanic acid, histamine, putrescine and cadaverine levels in Indian mackerel (Rastrelliger kanagurta) during storage at different temperatures.

Histamine, putrescine cadaverine and cis-urocanic acid (UCA) have all been implicated or suggested in scombroid fish poisoning. However, there is little information on UCA especially during storage. Changes in their contents during storage of whole Indian mackerel at 0, 3±1, 10±1 for up to 15 days and 23±2°C for up to 2 days were monitored. Fresh muscles contained 14.83 mg/kg trans-UCA, 2.23 mg/kg cis-UCA and 1.86 mg/kg cadaverine. Histamine and putrescine were not detected. After 15 days at 0 and 3°C, trans-UCA content increased to 52.83 and 189.51 mg/kg, respectively, and decreased to <2 mg/kg at the other two temperatures. Storage at 10°C also resulted in an increase in trans-UCA after 3 days, only to decrease after 6 days. The concentration of cis-UCA increased nearly 13-fold after 15 days at 0 and 3°C, decreased at 10°C and remained unchanged at 23°C. Histamine, putrescine and cadaverine levels increased significantly (P value<0.05) at all temperatures especially at 23°C.

The effect of electron beam irradiation on preparation of sago starch/polyvinyl alcohol foams

Abstract Blends of sago starch (SS)/polyvinyl alcohol (PVA) were irradiated with doses ranging from 10 to 30 kGy. Foams were then produced from these irradiated blends using a microwave. Changes in the degree of crosslinking, gel strength, thermal stability morphology of blends and linear expansion of foam with increasing irradiation doses were subsequently investigated. It was observed that the degree of crosslinking was important in maximizing the positive effect on foams produced. The gel strength of SS/PVA blends was affected by the irradiation. The crosslinking by the irradiation enhanced the thermal stability of SS/PVA blends. The results also revealed that the highest linear expansion of foams could be produced by irradiation blends at 15 kGy. Changes in blend morphology were observed upon irradiation.