Degradation of histamine by the halotolerant Staphylococcus carnosus FS19 isolate obtained from fish sauce

Histamine is found in many fermented food products and may have detrimental effects on the health of its consumers. Histamine and other amines are degraded by the oxidative deamination activity of certain microorganisms. In this study, the growth characteristics and histamine-degrading activity of a Staphylococcus carnosus FS19 isolate derived from fish sauce were investigated. This bacterium exhibits optimal growth at 35 °C, pH 8 and 9% sodium chloride when cultivated in tryptic soy broth. The histamine-degrading activity of the S. carnosus FS19 isolate was optimised at 40 °C and pH 6 in 9% buffered sodium chloride. When added to fish sauce samples, this bacterium exhibits remarkable histamine-degrading activity. The histamine concentration was reduced by approximately 15.1% and 13.8% in the fish sauce samples that contained 18% and 21% salt, respectively. However, no histamine degradation was observed in samples with a salt content greater than 21%. In addition, a slight degradation of other amines, including putrescine and cadaverine, was also observed in some of the samples. In contrast, tyramine degradation did not occur in any of the samples. Therefore, S. carnosus FS19 is a culture that could potentially reduce the histamine content of fermented fish products

Biogenic amines, amino acids and microflora changes in Indian mackerel (Rastrellinger kanagurta) stored at ambient (25–29 °C) and ice temperature (0 °C)

Biogenic amines formation in Indian mackerel of tropical region was investigated during storage at ambient (25–29 °C) and ice temperature (0 °C) in relation with changes of amino acids content and amines forming bacteria. All amines increased significantly during storage at two temperatures except for spermidine and spermine. Histamine concentration of 363.5 ppm was detected after 16 h stored at ambient temperature. Aerobic plate count of fish stored at ambient temperature reached 6.98 log CFU g−1 after 16 h, close to the upper limit (7 log CFU g−1) suggested by International Commission on the Microbiological Specifications for Foods (ICMSF). However, proper icing procedure retarded the formation of histamine effectively, resulting only 8.31 ppm after 16 days of ice storage. Aerobic plate count of 5.99 and 7.72 log CFU g−1 were recorded for fish stored in ice after 16 days and ambient temperature after 20 h, respectively. Histamine exhibited high correlation with histidine (r2 = −0.963, P  0.05). As storage time progressed, the amines forming bacteria grew significantly except for that stored in ice

Effects of different levels of CO2 on biochemical changes and relationships among different quality indices in Indian mackerel (Rastrelliger kanagurta)

The profile of total volatile base nitrogen (TVBN), pH, biogenic amines were studied in Indian mackerel packed under different levels of CO2 . Gutted and beheaded Indian mackerel was stored in air, vacuum packaging (VP), 30% CO2 /65% N2 /5% O2 (M30C), 60% CO2 /35%N2 /5%O2 (M60C), 80% CO2 /15%N2 /5% O2 (M80C) and 100% CO2 (M100C) at 5°C for 12 days. The application of VP and MAP was effective in retarding the formation of TVBN, total biogenic amines and improve the shelf life of Indian mackerel. Cadaverine obtained the best correlation with storage time when compared with other biogenic amines. Cadaverine or cadaverine + putrescine can serve as a reliable objective freshness indicator of fish stored in different atmospheres. Among the commonly used freshness indices, TVBN was the best quality indicator correlated with histamine. VP and MAP conditions influenced the performance of quality indicators. pH was a good quality indicator of spoilage in air-stored fish except for VP and MAP packed fish. Lower value of TVBN (30 mg/100g) was suggested as an upper limit for this species of fish under MAP condition based on APC and sensory result

Analysis of the Polypropylene-Based Aluminium-Air Battery

Global energy demand is rising due to the rapid development and adoption of new technologies in every sector. Hence, there is a need to introduce a clean energy source that does not cause damage to the environment. Aluminium-air battery with its high theoretical specific volumetric capacity is an exciting alternative for post-lithium energy storage and has been at the forefront of energy research for years. However, the conventional aqueous electrolyte-based aluminium-air battery with bulky liquid storage, parasitic corrosion of aluminium in contact with the electrolyte, and formation of a passive oxide or hydroxide layer has precluded its widespread application. In order to achieve successful simplification and cost-effectiveness, a novel idea of a polypropylene-based aluminium-air battery is proposed. In this work, a polypropylene-based aluminium-air battery was constructed using aluminium foil as an anode, carbon fiber cloth as an air-cathode, and Polypropylene and Kimwipes as the separator. The effects of the electrolyte concentration on the aluminium-air battery were investigated and analyzed using various discharge currents. The study showed that the performance of the polypropylene separator is better than that of the Kimwipes separator. The battery capacity is negatively correlated with the concentrations of the electrolyte. At a discharge current of 30 mA, the aluminium-air battery has a specific capacity of 375 mAh g−1 when 1 M of potassium hydroxide was used as electrolyte

Biogenic amine and microfloral profiling of Indian mackerel, Rastrelliger kanagurta cuvier during storage

Indian mackerel is the most common marine fish in Malaysia and is potentially associated with histamine poisoning incidence. However, no literature is available on the profile of biogenic amines in different storage conditions. Biogenic amines, biochemical, microbiological changes and sensory evaluation were investigated in Indian mackerel stored at different temperature and modified atmosphere packaging. Dominant spoilage microflora was identified in fish stored in air, vacuum packaging and 100%. Indian mackerel was subjected to storage at ambient temperature (25-29°C),chilled temperature (5 °C) and ice temperature (0 °C). Biogenic amines and various biochemical analysis such as pH, total volatile basic nitrogen and amino acids were carried out. All amines except for spermidine and spermine increased significantly during storage at ambient and chilled temperatures. The concentration of histamine reached the FDA acceptable limit after 16 hours at ambient temperature and 5 days at chilled temperature. Proper icing procedure retarded the formation of histamine effectively. This study confirmed the relationship between histidine and formation of histamine at ambient and chilled temperature. As storage time progressed, the amines forming bacteria grew significantly except for that stored in ice. The Indian mackerel was stored in air, vacuum packaging, 30% CO2/5% O2/65% N2, 60% CO2/5% O2/ 35% N2, 80% CO2/5% O2/ 15% N2 and 100% CO2 at chilled temperature (5°C) for 12 days. Each biogenic amine responded differently to a different level of CO2. High level of CO2 (≥60% CO2) was effective in retarding the formation of histamine in Indian mackerel. Fish stored in vacuum packaging and 30% CO2/5% O2/ 65% N2 tended to have a high concentration of histamine and tyramine. Vacuum packaging and all modified atmosphere packaging treatments were effective in reducing the pH and total volatile basic nitrogen. This study confirmed that the inhibitory effect of CO2 increases as the level of CO2 increases. The aerobic psychrotrophic bacteria were responsible for the formation of cadaverine and putrescine during the later stage of storage. The application of modified atmosphere packaging improved the shelf life of Indian mackerel. According to sensory evaluation, the fish was still acceptable by the panelists when stored for 5 days in air, 7 to 8 days in vacuum packaging and 30% CO2/5% O2/ 65% N2, 9 days in 60% CO2/5% O2/ 35% N2, 10 to 11 days in 100% CO2. In general, Aeromonas sp. was found as the dominant spoilage microflora during storage in air, vacuum packaging and 100% CO2. However, the diversity of microflora changed toward the end of the storage. The microbial diversity was directed to Pseudomonas sp. and enterobacteria in fish stored in air. In vacuum packaging, the prevalence of lactic acid bacteria and enterobacteria increased at the end of storage. The findings of the present study could contribute to the knowledge of food safety in controlling biogenic amine formation and microbial ecology in tropical fish. Aerobic plate count and total volatile basic nitrogen were correlated well with histamine at different storage temperature and atmosphere. Among the biogenic amines, cadaverine or cadaverine + putrescine can serve as good freshness indicator. A higher percentage of CO2 and a lower percentage of O2 in modified atmosphere packaging can be applied successfully in retarding the formation of histamine

Managing Sentosa as an attraction for both tourists and local residents.

Our objective and motivation underlying this research is to contribute in enabling Sentosa achieve its vision of making Sentosa the favorite recreational playground for both locals and tourists. Our results are based on 258 questionnaires completed in different parts of Singapore which form a non-probability sample. All the theoretical frameworks and research methodology are highlighted in Chapter One of the report

Role of information on outsourcing decisions.

The irrationality of the decision-maker has been explored in various situations such as escalation of commitment (that is, the allocation of additional resources to a failing course of action) and loss aversion. This research aims to study the decision-making behaviour of managers in an outsourcing context. Specifically, four independent variables are manipulated to investigate their effects on outsourcing decision. They are: sunk cost, the magnitude of sunk cost with respect to net savings resulting from outsourcing, manager’s responsibility for the historical investment and the performance of the current operation under consideration for outsourcing. A hypothetical outsourcing case scenario was developed to test the above variables. It was administered to a total of 342 third year accountancy undergraduates from Nanyang Technological University. The findings suggested that the presence of sunk cost information and the higher proportion of sunk cost to net savings resulted in a reduced likelihood of makin

MODELLING THE DIELECTRIC PROPERTIES OF COW'S RAW MILK UNDER VAT PASTEURIZATION

An efficient microwave milk pasteurization system requires a rigorous temperature dependent dielectric model of the milk, since the performance of milk pasteurization strongly depends on its dielectric properties. This paper describes the dielectric modelling of cow’s raw milk during batch (Vat) pasteurization which covers the frequencies from 0.2 GHz to 6 GHz. An open-ended coaxial sensor is used for the measurements of dielectric constant, loss factor, and ionic conductivity at temperature range of 25°C to 75°C with an interval of 5°C. Combinations of Cole-Davison and Debye equations are modified to fit the dielectric measurements. It was found that the measured dielectric constant decreased as the frequency increased, while the high temperature processed produce lower in a convergence manner toward 6 GHz. The loss factor exhibited high losses at higher temperature and lower frequencies, as well as converged at 1.9 GHz then diverged up to 6 GHz. Three relaxation processes are dominated at all temperature treatments within the frequency range. The relaxation time, τ, and the activation energy, Q, are modelled based on linear fitting of measured data according to Debye and Arrhenius approaches

Integrated Microfibre Device for Refractive Index and Temperature Sensing

A microfibre device integrating a microfibre knot resonator in a Sagnac loop reflector is proposed for refractive index and temperature sensing. The reflective configuration of this optical structure offers the advantages of simple fabrication and ease of sensing. To achieve a balance between responsiveness and robustness, the entire microfibre structure is embedded in low index Teflon, except for the 0.5–2 mm diameter microfibre knot resonator sensing region. The proposed sensor has exhibited a linear spectral response with temperature and refractive index. A small change in free spectral range is observed when the microfibre device experiences a large refractive index change in the surrounding medium. The change is found to be in agreement with calculated results based on dispersion relationships

Simulating forest fire spread and fire-fighting using cellular automata

In response to the transboundary haze problem in Southeast Asia, a physical model is adopted to simulate the spread and extinguishing of fire. This study is done in the context of Dumai, Indonesia, as it is one of the areas that significantly contribute to the haze problem. This model aims to provide perspectives on the persistence of forest fires despite fire-fighting efforts. While existing models using Huygens’ principle of wave propagation allow an understanding of the natural spread of fire, our model applies cellular automata to predict and analyse the effects of fire-fighting intervention strategies, with the spatial and propagation dynamics of fire considered. Cellular automata is an active area of research among physicists, and is widely used by chemists and biologists to model many types of natural phenomena. We note similarities between our model predictions and observations of real-world phenomena. Analyses on the factors that affect the spread of fire are presented, in order to understand which ones are dominant in differing situations. This provides insights on optimum conditions for fire-fighting efforts, and suggests guidelines that may be considered for fire control in future forest fires