Jamilah Bakar

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.

Effects of Different Wall Materials on the Physicochemical Properties and Oxidative Stability of Spray-Dried Microencapsulated Red-Fleshed Pitaya (Hylocereus polyrhizus) Seed Oil

The aim of this research was to investigate the influence of the composition of the wall material on the encapsulation and stability of microencapsulated red-fleshed pitaya seed oil. Hylocereus polyrhizus seed oil was homogenized with various wall material solutions at a core/wall material ratio of 0.33 and was microencapsulated by spray-drying. The microstructure and morphology of pitaya seed oil powder (PSOP) were observed using a scanning electron microscope (SEM). PSOP encapsulated with gum Arabic exhibited a lower degree of microencapsulation efficiency (MEE; 77.61–85.3%) compared to PSOP encapsulated with proteinaceous bases (90.12–98.06%). The study on oil retention revealed that sodium caseinate > whey protein > gum Arabic as effective wall materials for pitaya seed oil encapsulation. The effects of different wall systems on the oxidation stability of PSOP were studied under accelerated storage conditions; the peroxide value (POV) was determined throughout the test interval at several storage times. This study indicates that the use of lactose as wall material is able to increase the oxidation stability of PSOP; however, further research is needed to evaluate its antioxidative retention toward the oxidative stability of PSOP.

Novel starter cultures to inhibit biogenic amines accumulation during fish sauce fermentation

Bacteria with amine oxidase activity have become a particular interest to reduce biogenic amines concentration in food products such as meat and fish sausages. However, little information is available regarding the application of these bacteria in fish sauce. Hence, our study was aimed to investigate the effect of such starter cultures in reducing biogenic amines accumulation during fish sauce fermentation. Staphylococcus carnosus FS19 and Bacillus amyloliquefaciens FS05 isolated from fish sauce which possess amine oxidase activity were used as starter cultures in this study. Fermentation was held for 120 days at 35 °C. The pH value increased in all samples, while salt concentration remained constant throughout fermentation. Aerobic bacteria count was significantly lower (p < 0.05) in the control than in inoculated samples as a result of starter cultures addition. However, it decreased during fermentation due to the growth inhibition by high salt concentration. Proteolytic bacterial count decreased during fermentation with no significant difference (p > 0.05) among samples. These bacteria hydrolyzed protein in anchovy to produce free amino acid precursors for amines formation by decarboxylase bacteria. The presence of biogenic amines producing bacteria in this study was considered to be indigenous from raw material or contamination during fermentation, since our cultures were negative histamine producers. Amino acid histidine, arginine, lysine and tyrosine concentration decreased at different rates during fermentation as they were converted into their respective amines. In general, biogenic amines concentration namely histamine, putrescine, cadaverine and tyramine increased throughout fermentation. However, their concentrations were markedly higher (p < 0.05) in the control (without starter cultures) as compared to the samples treated with starter cultures. Histamine concentration was reduced by 27.7% and 15.4% by Staphylococcus carnosus FS19 and Bacillus amyloliquefaciens FS05, respectively. Both cultures could also reduce other amines during fermentation. After 120 days of fermentation, the overall biogenic amines concentration was 15.9% and 12.5% less in samples inoculated with Staphylococcus carnosus FS19 and Bacillus amyloliquefaciens FS05, respectively, as compared to control samples. These findings emphasized that application of starter cultures with amines oxidase activity in fish sauce fermentation was found to be effective in reducing biogenic amines accumulation.

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.

A Review: Microbiological, Physicochemical and Health Impact of High Level of Biogenic Amines in Fish Sauce

Problem statement: Biogenic amines are basic nitrogenous compounds present in a wide variety of foods and beverages. Their formations were mainly due to the amino acids decarboxylase activity of certain microorganisms. Excessive intake of biogenic amines could induce many undesirable physiological effects determined by their psychoactive and vasoactive action. Fish sauce which is considered as a good source of dietary protein, amino acids, vitamins and minerals was a popular condiment in Southeast Asian countries. However, it has also been reported that fish sauce contain high amount of amines. Hence, attention should be given to ensure the safety of this product. Approach: A review study was conducted to deliver an overview on the presence of biogenic amines in fish sauce and to discuss the important factors affecting their accumulation. Impact of amines on human health and efforts to reduce their accumulation in fish sauce were also discussed to give a comprehensive view. Results: Histamine, putrescine and cadaverine is the most abundant amines in fish sauce with maximum reported value of 1220, 1257 and 1429 ppm, respectively. Tyramine present in a lesser amount with maximum reported value of 1178 ppm. Other amines such as tryptamine, phenylethylamine, spermine and spermidine were considered as minor amines. However, different profiles of amines were reported in different type of products. This was depended on microbial flora, availability of precursors and physicochemical factors such as temperature, pH, salt, oxygen and sugar concentration. In synergistically supporting physicochemical factors, several microorganisms such as Enterobacteriaceae, Micrococci and Lactobacilli were responsible for biogenic amines formation in fish sauce. Conclusion: Since the formation of amines in fish sauce was a result of many factors, it was almost virtually impossible to control each factor during fermentation. Addition of amines degrading bacteria into fish sauce fermentation might be useful to prevent amines accumulation. Concomitantly, a good and hygienic manufacturing procedure will enhance the safety of fish sauce.

Purification and characterization of sago starch-degrading glucoamylase from Acremonium sp. endophytic fungus.

Abstract A novel sago starch degrading glucoamylase which had a strong amylopectin-hydrolyzing-activity was purified to homogeneity from a culture filtrate of Acremonium sp. isolated from forest trees. The purified enzyme was an oligomeric protein of two sub-units with molecular weights of 22 and 39 kDa. Optimum temperature and pH for enzyme activity were around 55°C and 5.5, respectively. The enzyme was stable in a pH range of 3.0–7.0 and temperatures up to 60°C. The purified enzyme was strongly inhibited by EDTA. The enzyme catalyzed hydrolysis of amylose and amylopectin, showed apparent K m values of 10.0 and 3.8 mg/ml and V max of 195 μmol/ml/min and 391 μmol/ml/min, respectively. Glucose was the sole product released by the hydrolysis, indicating that this enzyme displays an exo-action of starch-degrading activity.

Classification and quantification of palm oil adulteration via portable NIR spectroscopy

Short wave near infrared spectroscopy (NIR) method was used to detect the presence of lard adulteration in palm oil. MicroNIR was set up in two different scan modes to study the effect of path length to the performance of spectral measurement. Pure and adulterated palm oil sample were classified using soft independent modeling class analogy (SIMCA) algorithm with model accuracy more than 0.95 reported for both transflectance and transmission modes. Additionally, by employing partial least square (PLS) regression, the coefficient of determination (R2) of transflectance and transmission were 0.9987 and 0.9994 with root mean square error of calibration (RMSEC) of 0.5931 and 0.6703 respectively. In order to remove the uninformative variables, variable selection using cumulative adaptive reweighted sampling (CARS) has been performed. The result of R2 and RMSEC after variable selection for transflectance and transmission were improved significantly. Based on the result of classification and quantification analysis, the transmission mode has yield better prediction model compared to the transflectance mode to distinguish the pure and adulterated palm oil.

Enzyme Hydrolysates from Stichopus horrens as a New Source for Angiotensin-Converting Enzyme Inhibitory Peptides

Stichopus horrens flesh was explored as a potential source for generating peptides with angiotensin-converting enzyme (ACE) inhibitory capacity using 6 proteases, namely alcalase, flavourzyme, trypsin, papain, bromelain, and protamex. Degree of hydrolysis (DH) and peptide profiling (SDS-PAGE) of Stichopus horrens hydrolysates (SHHs) was also assessed. Alcalase hydrolysate showed the highest DH value (39.8%) followed by flavourzyme hydrolysate (32.7%). Overall, alcalase hydrolysate exhibited the highest ACE inhibitory activity (IC50 value of 0.41 mg/mL) followed by flavourzyme hydrolysate (IC50 value of 2.24 mg/mL), trypsin hydrolysate (IC50 value of 2.28 mg/mL), papain hydrolysate (IC50 value of 2.48 mg/mL), bromelain hydrolysate (IC50 value of 4.21 mg/mL), and protamex hydrolysate (IC50 value of 6.38 mg/mL). The SDS-PAGE results showed that alcalase hydrolysate represented a unique pattern compared to others, which yielded potent ACE inhibitory peptides with molecular weight distribution lower than 20 kDa. The evaluation of the relationship between DH and IC50 values of alcalase and flavourzyme hydrolysates revealed that the trend between those parameters was related to the type of the protease used. We concluded that the tested SHHs would be used as a potential source of functional ACE inhibitory peptides for physiological benefits.

Inhibitory effect of oxalic acid on bacterial spoilage of raw chilled chicken.

Oxalic acid was evaluated as a treatment for reducing populations of naturally occurring microorganisms on raw chicken. Raw chicken breasts were dipped in solutions of oxalic acid (0, 0.5, 1.0, 1.5, and 2.0%, wt/vol) for 10, 20, and 30 min, individually packed in oxygen-permeable polyethylene bags, and stored at 4 degrees C. Total plate counts of aerobic bacteria and populations of Pseudomonas spp. and Enterobacteriaceae on breasts were determined before treatment and after storage for 1, 3, 7, 10, and 14 days. The pH and Hunter L, a, and b values of the breast surface were measured. Total plate counts were ca. 1.5 and 4.0 log CFU/g higher on untreated chicken breasts after storage for 7 and 14 days, respectively, than on breasts treated with 0.5% oxalic acid, regardless of dip time. Differences in counts on chicken breasts treated with water and 1.0 to 2.0% of oxalic acid were greater. Populations of Pseudomonas spp. on chicken breasts treated with 0.5 to 2.0% oxalic acid and stored at 4 degrees C for 1 day were less than 2 log CFU/g (detection limit), compared with 5.14 log CFU/g on untreated breasts. Pseudomonas grew on chicken breasts treated with 0.5% oxalic acid to reach counts not exceeding 3.88 log CFU/g after storage for 14 days. Counts on untreated chicken exceeded 8.83 log CFU/g at 14 days. Treatment with oxalic acid caused similar reductions in Enterobacteriaceae counts. Kocuria rhizophila was the predominant bacterium isolated from treated chicken. Other common bacteria included Escherichia coli and Empedobacter brevis. Treatment with oxalic acid caused a slight darkening in color (decreased Hunter L value), retention of redness (increased Hunter a value), and increase in yellowness (increased Hunter b value). Oxalic acid has potential for use as a sanitizer to reduce populations of spoilage microorganisms naturally occurring on raw chicken, thereby extending chicken shelf life.

Purification and characterization of angiotensin converting enzyme-inhibitory peptides derived from Stichopus horrens: Stability study against the ACE and inhibition kinetics

Stichopus horrens is the most popular species of sea cucumber due to strong beliefs of its numerous medicinal properties. In this study, ACE-inhibitory peptides of S. horrens generated through enzymatic hydrolysis using Alcalase were isolated. Three peptides EVSQGRP, CRQNTLGHNTQTSIAQ and VSRHFASYAN were found to exhibit high inhibition potency with IC50 values of 0.05, 0.08 and 0.21 mM, respectively. It was found that the EVSQGRP, VSRHFASYAN and SAAVGSP exhibiting mixed inhibition patterns were susceptible to degradation by ACE as well, suggesting that the mixed-mode inhibition could be a result of new generated peptide fragments while CRQNTLGHNTQTSIAQ inhibited ACE in a non-competitive manner. In-vivo ACE inhibition studies showed that 400 mg/kg of Alcalase-generated proteolysate stabilized the blood pressure in normotensive rats. These results suggest that the hydrolysed protein components of S. horrens possess bioactive peptides that can be exploited as functional food ingredients against hypertension.