Thermophilic Campylobacter spp. in salad vegetables in Malaysia

The main aim of this study was to combine the techniques of most probable number (MPN) and polymerase chain reaction (PCR) for quantifying the prevalence and numbers of Campylobacter spp. in ulam, a popular Malaysian salad dish, from a traditional wet market and two modern supermarkets in Selangor, Malaysia. A total of 309 samples of raw vegetables which are used in ulam were examined in the study. The prevalences of campylobacters in raw vegetables were, for supermarket I, Campylobacter spp., 51.9%; Campylobacter jejuni, 40.7%; and Campylobacter coli, 35.2%: for supermarket II, Campylobacter spp., 67.7%; C. jejuni, 67.7%; and C. coli, 65.7%: and for the wet market, Campylobacter spp., 29.4%; C. jejuni, 25.5%; and C. coli, 22.6%. In addition Campylobacter fetus was detected in 1.9% of raw vegetables from supermarket I. The maximum numbers of Campylobacter spp. in raw vegetables from supermarkets and the wet market were >2400 and 460 MPN/g, respectively.     

Effects of Gellan-Based Edible Coating on the Quality of Fresh-Cut Pineapple During Cold Storage

The effects of gellan-based [gellan gum 0.56 % (w/v), glycerol 0.89 % (w/v) and sunflower oil 0.025 % (w/v)] edible coating on the respiration rate, physico-chemical properties and microbiological and sensory quality of fresh-cut pineapple during 16 days of storage (5?±?1 °C, 85?±?10 % RH) were evaluated. Uncoated fresh-cut pineapple was stored under the same condition and served as the control. For cross-linking reaction which was necessary for gel formation of gellan gum, a 2 % (w/v) calcium chloride solution that contained 1 % (w/v) ascorbic acid and 1 % (w/v) citric acid (as antibrowning agents) was used. The results obtained show that the respiration rate and weight loss of gellan-based coated samples were significantly (p?<?0.05) lower than those of the uncoated samples during 16 days of storage at 5 °C. In addition, coated samples significantly (p?<?0.05) maintained the firmness and colour of fresh-cut pineapple during low-temperature storage as compared to uncoated samples. The results obtained in this study also indicate that pH, titratable acidity and total soluble solids of coated and uncoated samples showed little changes during 16 days of storage at 5 °C. Gellan-based formulation did not show any antimicrobial effect, and no significant (p?>?0.05) differences were found among total plate counts and yeast and mould counts for coated and uncoated samples. Total plate counts and yeast and mould counts for coated and uncoated samples reached 10⁶ CFU/g (limit of shelf life acceptance for fruit-based products recommended by the Institute of Food Science and Technology in the UK) after 12 days of storage at 5 °C. In addition, the scores for all sensory characteristics at day 12 were significantly (p?<?0.05) higher in coated samples as compared to control. Therefore, the results obtained in this study indicate that gellan-based edible coating formulation has the potential to maintain the quality of fresh-cut pineapple during low-temperature storage for about 12 days.     

Determination of trans‐ and cis‐Urocanic Acid in Relation to Histamine,Putrescine, and Cadaverine Contents in Tuna (Auxis Thazard) at Different Storage Temperatures

Scombroid fish poisoning is usually associated with consumption of fish containing high levels of histamine. However, reports indicate that some cases have responded to antihistamine therapy while ingested histamine levels in these cases were low. Potentiation of histamine toxicity by some biogenic amines, and release of endogenous histamine by other compounds such as cis‐urocanic acid (UCA) are some hypotheses that have been put forth to explain this anomaly. Very little is known about the effects of storage conditions on the production of both UCA isomers and biogenic amines in tuna. Thus, the production of trans‐ and cis‐UCA, histamine, putrescine, and cadaverine in tuna during 15 d of storage at 0, 3, and 10 °C and 2 d storage at ambient temperature were monitored. The initial trans‐ and cis‐UCA contents in fresh tuna were 2.90 and 1.47 mg/kg, respectively, whereas the levels of putrescine and cadaverine were less than 2 mg/kg, and histamine was not detected. The highest levels of trans‐ and cis‐UCA were obtained during 15 d storage at 3 °C (23.74 and 21.79 mg/kg, respectively) while the highest concentrations of histamine (2796 mg/kg), putrescine (220.32 mg/kg) and cadaverine (1045.20 mg/kg) were obtained during storage at room temperature, 10 and 10 °C, respectively. Histamine content increased considerably during storage at 10 °C whereas trans‐ and cis‐UCA contents changed slightly. The initial trans‐UCA content decreased during storage at ambient temperature. Thus, unlike histamine, concentrations of trans‐ and cis‐UCA did not result in elevated levels during storage of tuna.     

Characterisation of musk lime (Citrusmicrocarpa) seed oil

BACKGROUND: The seeds of musk lime (Citrus microcarpa) represent a substantial waste product of small‐scale citrus‐processing factories, as they constitute about 100.0 ± 3.2 g kg^?1 of the whole fruit and contain a considerable amount of crude fat (338.0 ± 11.3 g kg^?1). Thus the aim of the present study was to determine the physicochemical properties of this fat with a view to potential applications. RESULTS: The iodine and saponification values and unsaponifiable matter and free fatty acid contents of the freshly extracted oil were 118.0 g I₂ per 100 g oil, 192.6 mg KOH g^?1 oil, 22 mg g^?1 oil and 18 mg oleic acid g^?1 oil respectively. The oil had a Lovibond colour index of 33.1 Y + 1.1 B. Its fatty acid profile indicated that 73.6% of the fatty acids present were unsaturated. Linoleic (L, 31.8%), oleic (O, 29.6%) and palmitic (P, 21.4%) acids were the predominant fatty acids, existing mainly as the triacylglycerols POL (18.9%), PLL (13.7%) and OLL (11.9%). The melting and cooling points of the oil were 10.7 and ? 45.2 °C respectively. Electronic nose qualitative analysis of the oil showed the presence of volatile (aroma) compounds, although the concentrations of the more volatile compounds were lower than those present in the seeds. CONCLUSION: Musk lime seeds are a rich source of oil, which is unusual in having linoleic, oleic and palmitic acids dominating the fatty acid composition. This property should make the oil both relatively stable to thermal oxidation owing to the combined presence of oleic and palmitic acids (61.0%) and highly nutritive owing to its high concentration of unsaturated fatty acids (73.6%). Copyright © 2007 Society of Chemical Industry     

Effect of Moringa Oleifera Oil Blending on Fractional Crystallization Behavior of Palm Oil

The objective of this study was to see the effect of Moringa oleifera oil blending on the fractional crystallization behavior of palm oil. Palm oil blended with Moringa oleifera oil at 20% (w/w) was subjected to crystallization using a dry process at 21 and 18°C and a solvent process at 15 and 10°C. After recording the quantitative recoveries of the liquid and solid fractions, their fatty acid and triacylglycerol compositions, and the thermal profiles were determined by using gas liquid chromatography, high performance liquid chromatography, and differential scanning calorimetry, respectively. Results showed that the yield recoveries of liquid fractions under solvent-assisted crystallization were higher than those obtained by dry-crystallization conditions. Almost all of the liquid fractions isolated had experienced a significant (p < 0.05) increase in oleic acid as well as triolein contents. Among the solid fractions, those isolated by dry-crystallization were found to be higher (p < 0.05) in oleic acid and triolein contents than the reference stearin sample. Although the thermal profiles of the solid and liquid fractions derived by different methods looked similar to those of the two reference samples, remarkable differences were noticed with regard to the onset of crystallization and the position of the thermal transitions.     

Physical properties of Pseudomonas and Rhizomucor miehei lipase-catalyzed transesterified blends of palm stearin:palm kernel olein

The physical properties of Pseudomonas and Rhizomucor miehei lipase-catalyzed transesterified blends of palm stearin:palm kernel olein (PS:PKO), ranging from 40% palm stearin to 80% palm stearin in 10% increments, were analyzed for their slip melting points (SMP), solid fat content (SFC), melting thermograms, and polymorphic forms. The Pseudomonas lipase caused a greater decrease in SMP (15°C) in the PS:PKO (40:60) blend than the R. miehei lipase (10.5°C). Generally, all transesterified blends had lower SMP than their unreacted blends. Pseudomonas lipase-catalyzed blends at 40:60 and 50:50 ratio also showed complete melting at 37°C and 40°C, respectively, whereas for the R. miehei lipase-catalyzed 40:60 blend, a residual SFC of 3.9% was observed at 40°C. Randomization of fatty acids by Pseudomonas lipase also led to a greater decrease in SFC than the rearrangement of fatty acids by R. miehei lipase. Differential scanning calorimetry results confirmed this observation. Pseudomonas lipase also successfully changed the polymorphic forms of the unreacted blends from a predominantly β form to that of an exclusively β′ form. Both β and β′ forms existed in the R. miehei lipase-catalyzed reaction blends, with β′ being the dominant form.     

The wear of wrought aluminium alloys under dry sliding conditions

The sliding wear response of several wrought aluminium alloys (2124, 3004, 5056 and 6092) against a high purity alumina (99.9%) counterface was investigated, at a fixed sliding speed of 1 m/s and a load range of 23–140 N. The counterface was chosen so as to minimise the chemically driven aspects of adhesive wear. Severe wear was observed at all loads, with specific wear rates ranging from 0.37×10⁻⁴ to 2.37×10⁻⁴ mm³/N m. In all cases a mechanically mixed layer (MML) was formed, principally from severely work hardened aluminium alloy, but also including fine alumina particles. The thickness and morphology of the layer depended strongly on alloy composition, but the specific wear rate did not depend on the MML properties in a simple manner. The surface work hardening characteristics differed between alloys, but as with the MML, there was no simple relationship between surface work hardening characteristics and specific wear rate. The main correlation was found between the normalised wear rate and normalised pressure, which implies that the hardness of the starting aluminium alloy is the critical variable.     

Lysozyme-coated silver nanoparticles for differentiating bacterial strains on the basis of antibacterial activity

Lysozyme, an antibacterial enzyme, was used as a stabilizing ligand for the synthesis of fairly uniform silver nanoparticles adopting various strategies. The synthesized particles were characterized using UV-visible spectroscopy, FTIR, dynamic light scattering (DLS), and TEM to observe their morphology and surface chemistry. The silver nanoparticles were evaluated for their antimicrobial activity against several bacterial species and various bacterial strains within the same species. The cationic silver nanoparticles were found to be more effective against Pseudomonas aeruginosa 3 compared to other bacterial species/strains investigated. Some of the bacterial strains of the same species showed variable antibacterial activity. The difference in antimicrobial activity of these particles has led to the conclusion that antimicrobial products formed from silver nanoparticles may not be equally effective against all the bacteria. This difference in the antibacterial activity of silver nanoparticles for different bacterial strains from the same species may be due to the genome islands that are acquired through horizontal gene transfer (HGT). These genome islands are expected to possess some genes that may encode enzymes to resist the antimicrobial activity of silver nanoparticles. These silver nanoparticles may thus also be used to differentiate some bacterial strains within the same species due to variable silver resistance of these variants, which may not possible by simple biochemical tests.