Salmonella is an important foodborne pathogen, whose ability to resist stress and survive can vary among strains. This variability is normally not taken into account when predictions are made about survival in foods with negative consequences. Therefore, we examined the contribution of variable phenotypic properties to survival under stress in 10 Salmonella serovars. One strain (Typhimurium 10) was intentionally RpoS-negative; however, another strain (Heidelberg) showed an rpoS mutation, rendering it inactive. We assessed an array of characteristics (motility, biofilm formation, bile resistance, acid resistance, and colony morphology) that show major variability among strains associated with a 10- to 19-fold difference between the highest and the lowest strain for most characteristics. The RpoS status of isolates did not affect variability in the characteristics, with the exception of resistance to NaCl, acetic acid, lactic acid, and the combination of acetic acid and salt, where the variability between the highest and the lowest strain was reduced to 3.1-fold, 1.7-fold, 2-fold, and 1.7-fold, respectively, showing that variability was significant among RpoS-positive strains. Furthermore, we also found a good correlation between acid resistance and lysine decarboxylase activity, showing its importance for acid resistance, and demonstrated a possible role of RpoS in the lysine decarboxylase activity in Salmonella.
A study was carried out to create a new product using watermelon flesh (sources of lycopene) and watermelon by-product, which was watermelon rind (sources of citrulline), into pastilles with different percentages of flesh and rind puree. The formulations involved were formulations A (70% flesh puree: 30% rind puree), B (50% flesh puree: 50% rind puree), and C (30% flesh puree: 70% rind puree). A commercial product was used as a reference in making the pastilles. The physical analyses that were carried out were pH, total soluble solids, water activity, colour analysis, and texture profile analysis (TPA). Chemical analysis that focused on lycopene determination, as well as sensory analyses, was also conducted. The pastilles produced had total soluble solids ranging from 41.44±0.68 to 49.03±1.49°Bx, and pH values measured at 2.52±0.09 to 2.54±0.17, which indicated an acidic aftertaste. Water activity was evaluated to be between 0.72±0.01 to 0.73±0.03, which signified the pastilles were safe to consume. The colour analysis for the L* value, a* value, and b* value was 36.84±1.48, 13.07±2.70, and 11.89±1.61, respectively, which indicated the yellowish-red colour of the pastilles. Formulation A had the highest lycopene value (0.197±0.01) as compared to the other formulations. The pastilles were successfully developed in seashell shapes with diameters of 2.74–2.76 cm and about 2.52–2.80 g in weight. The sensory evaluation showed that the pastilles from formulation B were more acceptable in terms of taste, appearance, and overall acceptability, followed by formulation A, and the least preferred was formulation C.
Although vegetables are considered to be an essential part of a healthy diet, studies have shown that they can also represent a hazard for human health as they are usually eaten raw and receive minimal treatment. In recent years, vegetables are among the food groups associated with higher rates of recurrence and are the leading cause of enteric diseases. There is a colossal amount of data available on fresh produce worldwide; however, limited data are available regarding the microbiological quality of ulam in Malaysia. In fact, cross -contamination that occurs during minimal processing of ulam has not yet been studied. Therefore, the aim of this study was to evaluate the microbiological quality and the occurrence of Escherichia coli and Salmonella in ulam. A total of 32 samples of ulam were randomly collected from wet markets and supermarkets in Kuala Terengganu, Malaysia. The samples were analysed for enumeration of aerobic mesophilic bacteria, coliforms, yeast and moulds, Bacillus cereus, Listeria monocytogenes and detection of Escherichia coli and Salmonella. In this study, the microbiological quality of ulam were in the range of 6.36-8.83; 4.14-7.48; 0-8.16; 3.94-6.45 log10 CFU/g for aerobic mesophilic bacteria, coliforms, Salmonella and yeast and moulds, respectively. Escherichia coli and Salmonella were detected in 3.13% and 9.4% of ulam samples, respectively. The findings from the study are intended to provide insight into the potential health risks associated with the consumption of ulam. The strong interdisciplinary approach by various agencies and development of safe agricultural systems will ensure the delivery of safe vegetables to the end-users
Fruit juice is an ideal medium in the production of a probiotic drink. Watermelon fruit is a suitable medium for the production of probiotic juice due to its nutritional content. However, its utilisation as a probiotic drink is underutilised. Experiments were conducted to determine the chemical (pH, Brix, titrable acidity) and microbiological changes (lactic acid bacteria (LAB) count) during fermentation of probiotic watermelon juice using different concentrations of Lactobacillus plantarum, Lactobacillus paracasei and Lactobacillus acidophilus (2%, 5% and 10%) at 30°C for 72 hrs. The results indicated a significant drop in pH of the probioticated watermelon juice (2%, 5% and 10%) using various Lactobacilli strains during 24 hrs of fermentation. Interestingly, 2% probioticated watermelon juice in all their strains of probiotic were higher than 5% and 10% probioticated watermelon juice. The lactic acid content in probioticated watermelon juice was reduced significantly throughout 72 hrs of fermentation, but the watermelon juice without probiotic strains increased only within 24 hrs of fermentation. The LAB count in probioticated watermelon juice (2%, 5% and 10%) maintained a high population count (108 to 109 CFU/mL) for all probiotic strains throughout fermentation. Since all concentrations studied showed similar results in the chemical and microbiological analyses, 2% concentration is proven to be sufficient for probioticated watermelon juice regardless of the types of Lactobacillus strains used.
This study explored the effect of chitosan coating incorporated with pineapple peel extract on the postharvest quality of white shrimp (Litopenaeus vannamei) during nine days of storage at 5°C. Incorporation of pineapple peel extract in chitosan coating was able to delay the decline of some important postharvest quality measures of white shrimp which includes reduced formation of total volatile basic nitrogen and peroxide value. It also decreased melanosis formation and hindered growth of Pseudomonas which assists in prolonging shelf ife quality of white shrimp. Additionally, shrimp coated with chitosan incorporated with pineapple peel extract had an improved sensory score which includes assessment on overall acceptance. The results showed that chitosan coating incorporated with pineapple peel extract could be a natural approach towards retaining postharvest quality of shrimp as well as decrease the employment of synthetic treatments. The utilization of pineapple peel could also reduce the agricultural waste in the environment.
is usually red in colour during ripening but can be green, white, or yellowish depending on the cultivar. Strawberry is a highly commercial fruit and most often consumed fresh. Strawberry is rich in carbohydrates, vitamin C and natural antioxidants such as flavonoids and phenolic compounds (Erkan & Wang, 2008
Strawberry (Fragaria Ananassa sp.) is non-climacteric, aggregate fruit with a rich source of anthocyanin and vitamin C. However, strawberry has short storage life and is very susceptible to decay and physiological deterioration process. Therefore, emitting the post-harvest LED light to strawberries during cold storage has been studied. This work aimed to evaluate different LED light treatment effects to retain post-harvest quality and microbial quality of the strawberry. The post-harvest parameters that have been used are weight loss, colour, firmness, total soluble solids, titratable acidity, and pH. The microbial parameter such as Escherichia coli count, Salmonella count, total plate count, and mold count would also has been assessed. Strawberries were irradiated under three different LED light types (white, blue and red). Blue and red LED lights have different wavelengths, which are 470 nm and 630 nm. The strawberry fruits were stored at 5ºC in a cold room and study parameter were assessed in 10 days. There were statistically significant differences (p<0.05) between the treatment of weight loss, firmness, pH, and total soluble solid. The best treatment for this experiment is blue LED light which showed the lowest weight loss, retained the colour and delayed firmness loss of the strawberry. This study also proved that blue LED light could reduce the growth of E.coli. In conclusion, LED light produces minimal heat, which improves food safety and preserves post-harvest quality of strawberry.
Banana has a short storage life and is classified under climacteric fruit that produces enough ethylene in changing physico-chemical characteristics, including colour, texture, aroma, chemical composition, respiration rate and senescence. Besides that, the presence of microbes also contributes to the postharvest losses which can be reduced by implementing various postharvest management practices that are currently in practice all over the world. Research has been done in delaying ripening and maintaining the quality of banana such as hot water treatment, controlled atmosphere storage, modified atmosphere packaging and postharvest chemical treatments such as methyl jasmonate, salicylic acid, acetylsalicylic acid or oxalic acid. However, not many focus on non-chemical method such as UV-C radiation. In line with that, this study aimed at evaluating the effects of UV-C radiation in delaying ripening and maintaining the postharvest quality of Berangan banana. Five treatments of UV-C radiation were used viz. 0.000 kJ/m², 0.004 kJ/m², 0.008 kJ/m², 0.012 kJ/m² and 0.016 kJ/m² with three replications. Postharvest parameters evaluated were percentage of weight loss (%), skin colour, starch pattern index (SPI), fruit firmness, soluble solids concentration (SSC), titratable acidity (TA), ascorbic acid (AA) and total phenolic content (TPC). The application of UV-C radiation did not significantly affect all postharvest parameters of treated Berangan bananas. However, UV-C radiation at 0.008 kJ/m2 tended to show the lower percentage weight loss and SPI score. In conclusion, 0.008 kJ/m² of UV-C radiation could be applied to delay ripening and maintaining other quality attributes of Berangan bananas. In addition, 0.008 kJ/m² UV-C also able to prolong the shelf life of Berangan bananas stored at 26±2°C/75% relative humidity up to nine days.
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