The mode of action and activities of guava leaf extracts against various food pathogens were studied. The killing kinetics, viability and cell leakage of Kocuria rhizophila, Salmonella typhimurium, Listeria monocytogenes and Escherichia coli O157:H7, measured after exposure to guava methanolic extracts (GME) revealed a significantly higher (p≤0.05) release of bacterial nucleic acids, K+ ions and protein than that of untreated microbes, indicating disruption of the bacterial membrane. GME caused a significantly higher (p≤0.05) release of RNA in gramnegatives compared to gram-positives. GME caused a relatively small but significant release of pyrines and pyrimidines in all organisms investigated. GME probably disrupted the integrity of the Gram-negative microorganism lipopolysaccharide (LPS) layer. Unlike all the other microorganisms tested, E. coli O157:H7, demonstrated the lowest protein leakage, the highest K+ leakage, the highest pyrines and pyrimidines leakage within the first 10 min of extract exposure, but the lowest after 30 minutes, which may indicate their good homeostasis ability or adaptability. Understanding the mode of action of this flavonoid rich guava leaf extract, would help develop it as an alternative biodegradable and safe, antimicrobial for food and medicine, and as a by-product of the guava industry.
Keropok lekor is an important fish product in Malaysia. The customer demands for keropok lekorhave been increasing. This study was conducted to analyze the microbiological quality of keropok lekor in every stage of its processing, namely mincing, mixing, kneading, boiling and cooling. When processing keropok lekor, the boiling of keropok lekor at 100°C for 10 min reduced the Total Plate Counts (4.38±0.47 log10 cfu/g), psychrotrophic counts (2.00 ± 0.00 log10 cfu/g), mesophilic sporeformer counts (1.26 ± 0.34 log10 cfu/g) and total coliform counts (1.71±0.51 log Most Probable Number/g) significantly (p>0.05). However, the microbial counts were found to increase significantly (p
The present work aimed to determine the best formulation of mixed drink made from red cabbage and roselle extracts. Six mixed drink formulations were prepared based on different ratios of red cabbage to roselle extracts: F1 (30:20); F2 (35:15), F3 (40:10); F4 (20:30); F5 (15:35) and F6 (25:25). Samples were prepared by pasteurising the mixed drinks with the pre-determined amount of ingredients at 90°C for 5 sec. The pH of roselle extract (2.06 ± 0.02) was found to be more acidic as compared to red cabbage extract (6.38 ± 0.03). This contributed to the low pH in mixed drink formulations (2.68-3.48). Total titratable acidity (TTA) (0.44-0.89% malic acid w/v) and total anthocyanin content (247.99-339.77 mg cyanidin-3-glucoside/L) were shown to increase significantly with increasing roselle extract concentration. Similarly, total soluble solids (TSS) (12.23-12.83°brix) was found to increase significantly with higher ratio of red cabbage extract due to high TSS content (7.67 ± 0.08°brix) in the extract as compared to roselle extract (4.63 ± 0.09°brix). There were significant differences among all the samples in L*, a* and b* values. Mixed drink formulations that contained higher concentration of red cabbage extract were lighter and redder in colour. Significant differences were observed in sweetness, sourness, taste and overall acceptability of drinks, with F3 yielding the highest mean scores for all attributes. Mean score of sensory attributes of the mixed drinks were related to physicochemical properties. Mean scores of all sensory attributes had negative correlation with TTA. Sweetness mean score was positively correlated to the L* value, sourness mean score was positively correlated with pH, L* and a* values but negatively correlated with b* value, and colour mean score had positive correlation with a* value. Therefore, it can be concluded that panellists preferred less sour drinks, which were lighter and redder in colour.β-carotene onto the PKSAC in a model system but yielded the highest desorption efficiency.
Fatty acid profile from crude extracts of local sea cucumber Stichopus chloronotus was determined using gas chromatography (GC) technique. The extracts were prepared separately in methanol, ethanol, phosphate buffer saline (PBS), and distilled water as part of our study to look at the affinity of these solvents in extracting the lipid from sea cucumber. The PBS and distilled water extractions indicate water-soluble components, while the organic fractions are extracted in methanol and ethanol as organic solvents. Furthermore, water extraction is the conventional method practiced in Malaysia. In our analysis the C14:0 (myristic), C16:0 (palmitic), C18:0 (stearic), C18:2 (linoleic), C20:0 (arachidic), and C20:5 (eicosapentaenoic, EPA) were significantly different (p < 0.01) in the four solvent extractions. However, the PBS extraction contained a much higher percentage of EPA (25.69%) compared to 18.89% in ethanol, 7.84% in distilled water, and only 5.83% in methanol, and variances were significantly different (p < 0.01 ). On the other hand, C22:6 (docosahexaenoic acid or DHA) is much higher in water extraction (57.55%), in comparison to the others where only 3.63% in PBS and 1.20% in methanol, and this difference is significant at p < 0.01. No DHA was detected in ethanol extractions. Subsequently, C18:1 (oleic acid) was only detected in PBS (21.98%) and water extraction (7.50%). It is interesting that palmitic acid, C16:() was higher in methanol (20.82%) and ethanol (2.18%), while 12.55% was detected in PBS and only 2.20% in water extraction: and again this was significantly different at p < 0.01. Although our results have shown that all four solvents were different in terms of their ability to extract fatty acids, the major component for tissue repair was well preserved. Probably this is one of the important precocious steps when working with a delicate sea cucumber, in both experimental and/or at the preparative stages. Freshness of the sea cucumber samples is important when undertaking this type of experiment. Finally, we believe that the local sea cucumber S. chloronotus contains all the fatty acids required to play a potential active role in tissue repair.