HyperDSC™(fast scan rate) was used to study the melting behavior of canola (CLO), sunflower (SFO), palm olein (PO), rice bran oils (RBO), and cocoa butter (CB), and was compared to the melting behaviors using conventional DSC. There was an increase in sensitivity with increase in scan rate. Slow scan rate (5 to 20C/min) gave low sensitivity, which increased when the scan rates were increased to 50, 100 and 200C/min. Peak resolution was affected by scan rate depending on the sample weight. Increase in the size of sample coupled with the use of fast scan rate decreased the peak resolution. Generally small sample sizes gave better peak resolution. Results of the effect of scan rate on glass transition (Tg) shows that Tg, which is a weak transition especially in crystalline and low amorphous materials was not detected using conventional scan rates (5 to 20oC/min). It was however detected using of hyperDSC™ scan rates (100 to 200oC/min). Increasing the scan rate resulted in an increase in the peak temperature and the elimination of shoulder peaks, which were caused due to the polymorphic behavior of the triacylglycerols in the oils. The increase in peak temperature caused a shift in the peak position towards a higher temperature value. There is a positive correlation between the peak temperature and scan rate. The correlation coefficients (r) for CLO, SFO, PO, RBO and CB were 0.96, 0.95, 0.97, 0.96 and 0.96 respectively.
5'-Phosphodiesterase (5'-PDE) is an enzyme that hydrolyses RNA to form 5'-inosine monophosphate (5'-IMP) and 5'-guanosine monophosphate (5'-GMP), which function as flavour enhancers. Selection of the best producer of 5'-PDE was made by determining the activity of the enzyme in six seeds that have been germinated, namely mung bean (Vigna radiate), soybean (Glycine max), adzuki/red bean (Vigna angularis L.), chick pea (Cicer arietinum), black eye pea (Vigna unguiculata) and petai (Parkia speciosa). Seeds that were not germinated acted as the control. In order to ensure there is no contamination from potential 5'-PDE-producing microorganisms during germination, microbial growth was reduced by using different surface sterilizing treatments where the seeds were soaked in 100 mL solution containing different concentrations of sodium hypochlorite (with or without 0.05% sodium azide) for 5 minutes before rinsing it five times with sterilized distilled water (total 500 mL). The seeds were observed every day for 3 days and the best surface sterilizing treatment was selected based on absence of mold growth and the effects on hypocotyl length. Sodium hypochlorite at 0.3% (v/v) concentration was able to inhibit mold growth in adzuki bean, soybean and chickpea. On the other hand, only 0.1% (v/v) sodium hypochlorite was needed to inhibit mold growth in black eye pea and petai, while mung bean required 0.05% (v/v) sodium hypochlorite to inhibit mold growth. Under these conditions, the growth of hypocotyl (hypocotyls length) was only slightly affected compared to the control. 5'-PDE was extracted from seeds that have been germinated for 24 hours and their control (ungerminated seeds) by homogenization in a blender with 400 mL of 50 mM acetate buffer, pH 4.5. After that, the homogenates were stirred for 30 min and the centrifuged at 9000 rpm for 15 min at 10°C. 5'-PDE activity was determined using thymidine 5'-monophosphate p-nitrophenyl ester as substrate at pH 7.0 and 55°C. The formation of nucleotide monophosphates, the products of reaction, was determined at 405 nm. As a strong presence of phosphomonoesterase (PME) will reduce the yield of nucleotide monophosphates as the enzyme hydrolyzes these products into nucleosides and orthophosphate, PME activity was also determined using p-nitrophenyl phosphate as the substrate at 60°C and pH 5.0. Thus, the seed with the highest 5'-PDE activity and a low PME activity can be selected. Germinated adzuki bean was found to have the highest 5'-PDE activity (0.59 µmol p-nitrophenol/min/mg protein) among the germinated seeds. A time-course study indicated that the level of 5'-PDE in adzuki bean increased with time of germination until 15 hours (0.69 µmol p-nitrophenol/min/mg protein), after which the acitivity decreased until it reached the basal level (0.44 µmol p-nitrophenol/min/mg protein) at 72 hours. On the other hand, PME in the bean was the highest at 9 h germination (0.98 µmol p-nitrophenol/min/mg protein). In general, controls have very low basal level of 5'-PDE activity (0.18- 0.42 µmol p-nitrophenol/min/mg protein).
Extracts from ‘kesinai’ (Streblus asper) leaves were investigated as a potential source of enzymes that can serve as an alternative to calf rennet in cheese making. Different types of extraction buffers were investigated namely sodium acetate buffer (pH 4.2-5.0), phosphate buffer (pH 6.0-7.0) and Tris-HCl buffer (pH 7.0-9.0). Finally, the milk-clotting enzyme was extracted using 100 mM Tris-HCl buffer (pH 7.4) with and without 5.0 mg/mL polyvinylpyrrolidone, 0.015 mL/mL Triton X-100 and 2 mM sodium metabisulphite. Purification was carried out using acetone precipitation, and ion-exchange and size-exclusion chromatographic techniques. Results showed that 100 mM Tris-HCl buffer (pH 7.4) was the most efficient extraction buffer among the buffers used in the extraction study. After the final purification step of size-exclusion chromatography, the enzyme was purified 3.3-fold with 42.3% of recovery. The enzyme showed an optimum temperature and pH at 60°C and pH 7.4, respectively. The enzyme was stable up to 70°C for one hour and the partially purified enzyme retained 83% and 96% of its original activity at pH 6.0 and 8.0, respectively. The molecular weight of the partially enzyme was estimated to be 75.8 kDa on SDS-PAGE. The milk-clotting activity of ‘kesinai’ enzyme was found to be lower than that of commercial Mucor rennet.
Proteases in ginger rhizome have the potentials in industrial applications. This study was conducted to extract and characterize the proteolytic enzyme from ginger (Zingiber officinale Roscoe). Ginger protease (GP) was extracted from ginger rhizome by homogenization with 100 mM potassium phosphate buffer pH 7.0 containing 10 mM cysteine and 5 mM EDTA which were found to be the most efficient extraction buffer and stabilizers. After centrifugation at 10,500 x g, protein in the crude extract was precipitated using 60% ammonium sulfate following which the precipitate was redissolved in 50 mM potassium phosphate buffer pH 7.0, dialyzed and then lyophilized. The extraction method yielded 0.94% (w/w of fresh weight) of GP with a specific activity of 27.6 ± 0.1 Unit/mg protein where 1 Unit is defined as the amount of protease causing an increase in absorbance by 1 unit per minute using azocasein as the substrate. Results show that the GP was completely inhibited by heavy metal cations i.e. Cu2+and Hg2+, and a thiol blocking agent or inhibitor, n-ethyl maleimide (NEM), indicating that GP is most probably a cysteine protease. The enzyme has an optimum temperature at 60⁰C and the optimum pH ranged between pH 6 to 8. Monovalent cations (K+ and Na+) have no significant effect on activity of GP, but divalent and trivalent cations showed moderate inhibitory effect. Detergents such as sodium dodecyl sulfate increased the activity of GP while Tween 80 and Tween 20 slightly reduced the activity.
Solvent-extracted Moringa oleifera seed oil was transesterified using immobilized lipase (Lipozyme IM 60) (Novozymes Bagsvaerd Denmark) at 1% (w/w) concentration, shaken at 60oC and 200 rpm for up to 24h. After transesterification, the oil was fractionated with acetone at -18oC and without acetone at 10oC to obtain two fractions, stearin and olein fractions. Incubation of the transesterified oil at 10oC for 24 h resulted in the formation of fat crystals, which settled at the bottom of the flask in sample transesterified for 24 h, while the control (0 h) sample became rather viscous with fat crystals in suspension. Transesterification resulted in a change in the triacylglycerol (TAG) profile of the oil, which in turn affected its solid fat content (SFC) and thermal behavior. The SFC value at 0oC after 24 h of reaction was 10.35% and significantly (P
The antibacterial activity of solvent-extracted oil of noni (Morinda citrifolia L.), spinach (Spinacia oleracea L.), lady’s finger (Abelmoschus esculentus (L.) Moench), bitter gourd (Momordica charantia Linn.), and mustard (Brassica nigra L.) seed oils, and coconut (Cocos nucifera L.) oil, palm (Elaeis guineensis L.) mesocarp in hydrolyzed and unhydrolyzed form were determined in order to explore their potential usage as antibacterial agent. The hydrolysis process that was catalyzed by immobilized lipase of Rhizomucor miehei (RMIM) showed highest hydrolytic activity with 1.0 ml of added water volume except bitter gourd seed oil and palm mesocarp oil which has maximum hydrolytic activity with added water volume of 5 ml and 2.5 ml respectively. Before hydrolysis, all oil samples did not show inhibition ring zones (IRZ) on any of the tested bacteria strains (Salmonella typhimurium, Listeria monocytogenes and Escherichia coli O157:H7). Hydrolyzed lady’s finger and bitter gourd seed oil showed IRZ on all tested bacteria strains; hydrolyzed mustard seed oil on S. typhimurium and L. monocytogenes; hydrolyzed spinach seed oil and coconut oil on L. monocytogenes; hydrolyzed noni seed oil and palm mesocarp oil did not exhibit IRZ on any of the tested bacteria strains. Most of the hydrolyzed oil exhibit an inhibition activity that was different from their respective dominant fatty acids except noni seed oil and palm mesocarp oil.
Natural products are useful for delaying the ripening process, preserving quality and reducing biochemical changes in fruits. Effect of gum arabic (GA) 10% and chitosan (CH) 1% edible coatings on physiological and biochemical properties of mango (Mangifera indica L. cv. Choke Anan) fruit were investigated. Mango fruit were stored at 13°C and 80% relative humidity for 28 days. Significant (P≤0.05) differences were observed in fruits treated with GA 10% and CH 1% as compared to the control. The results showed that GA 10% and CH 1% treatments significantly reduced weight loss than the control fruits. The application of CH 1% coating effectively inhibited the increase in soluble solid concentration (SSC), respiration rate and ethylene production. But no significant differences were observed in terms of ascorbic acid loss between treated fruits and control during the entire storage period. Furthermore, the combined application of GA 10% + CH 1% alleviated decay incidence and retained high firmness of mango fruit. These results suggested that application of GA 10% coating combined with CH 1% as a bio preservative might be a simple and effective technique for delaying ripening and maintaining quality of mango fruit during cold storage without the use of fungicides.
‘Cempedak’ (Artocarpus integer L.) is an aromatic exotic tropical fruit that can be widely found in Malaysia during season. The pulp yield and several physicochemical properties of five varietes of ‘cempedak’ (CH27, CH28, CH29, CH30 and CH33) were determined. The latter included total soluble solids, titratable acidity, pH, color, organic acids, sugars and carotenoid contents. Sensory evaluation of the five ‘cempedak’ varieties was conducted using Hedonic test, in which the assessed attributes include color, taste, texture and overall acceptability. Results indicate that CH33 yield the highest percentage (35.8%) of edible portion (fruit pulp), while CH27 shows the highest tiratable acidity (0.52%). CH30 had the lowest L* value (52.41), and highest intensity of color in terms of redness (32.45) and yellowness (65.27) values. All ‘cempedak’ varieties were highest in sucrose content (12.28-20.02 g/100 gFW) compared to fructose (5.70-6.72 g/100 gFW) and glucose (4.94-5.52 g/100 gFW), while malic acid (0.430.70%) was the highest organic acid as compared to citric acid (0.24-0.60%) and succinic acid (0.20-0.33%). All the ‘cempedak’ varieties studied have high content of α-carotene (2.30-45.27 μg/100 gFW), followed by β-carotene (2.30-12.23 μg/100 gFW), with CH28 having the highest content. From the five varieties of ‘cempedak’ fruit examined, it was found that CH28 ranked the highest in terms of sensory properties, namely taste, texture and overall acceptability.
The effects of alginate-based [sodium alginate, 0-2% (w/v), glycerol, 0-2% (w/v) and sunflower oil 0.025% (w/v)] and gellan-based [gellan, 0-1% (w/v), glycerol, 0-1% (w/v) and sunflower oil 0.025% (w/v)] edible coatings on fresh-cut pineapple were evaluated by response surface methodology (RSM). Weight loss, firmness and respiration rate were considered as response variables. The results showed that for all response variables the RSM models were significantly (p0.05) difference between predicted and experimental values. The overall optimum region predicted by RSM indicated that alginate and gellan-based coatings containing 1.29% (w/v) sodium alginate, 1.16% (w/v) glycerol and 0.56% (w/v) gellan gum, 0.89% (w/v) glycerol were optimized formulations respectively.