A review on global metal accumulators-mechanism, enhancement, commercial application, and research trend.

The biosphere is polluted with metals due to burning of fossil fuels, pesticides, fertilizers, and mining. The metals interfere with soil conservations such as contaminating aqueous waste streams and groundwater, and the evidence of this has been recorded since 1900. Heavy metals also impact human health; therefore, the emancipation of the environment from these environmental pollutants is critical. Traditionally, techniques to remove these metals include soil washing, removal, and excavation. Metal-accumulating plants could be utilized to remove these metal pollutants which would be an alternative option that would simultaneously benefit commercially and at the same time clean the environment from these pollutants. Commercial application of pollutant metals includes biofortification, phytomining, phytoremediation, and intercropping. This review discusses about the metal-accumulating plants, mechanism of metal accumulation, enhancement of metal accumulation, potential commercial applications, research trends, and research progress to enhance the metal accumulation, benefits, and limitations of metal accumulators. The review identified that the metal accumulator plants only survive in low or medium polluted environments with heavy metals. Also, more research is required about metal accumulators in terms of genetics, breeding potential, agronomics, and the disease spectrum. Moreover, metal accumulators' ability to uptake metals need to be optimized by enhancing metal transportation, transformation, tolerance to toxicity, and volatilization in the plant. This review would benefit the industries and environment management authorities as it provides up-to-date research information about the metal accumulators, limitation of the technology, and what could be done to improve the metal enhancement in the future.

Histamine stability in Rihaakuru at -80, 4 and 30°C.

Rihaakuru is a shelf stable fish paste product formed from a fish soup prepared from tuna. Histamine contamination is a food safety issue with this product that is manufactured from tuna fish that has been temperature abused. Histamine concentrations decreased between 31% and 73% in Rihaakuru stored for 10months at either -80, 4 or 30°C. This appears to be a property of the product as histamine solutions are reported to be stable, at least under frozen storage. The risk of histamine food poisoning due to Rihaakuru may reduce during the storage of the product.

Chemistry and microbiology of traditional Rihaakuru (fish paste) from the Maldives.

Rihaakuru is a traditional Maldivian side dish consumed mainly with rice. It is a thick brown fish paste, made from tuna after prolonged heating. Samples tested were found to have a low water activity (0.55-0.8), slightly acidic pH (5.62-6.18) and moderate salt content (1.4-1.6%). The product was found to be rich in polyunsaturated fatty acids such as omega-3, had high protein content (56-59%) and an energy level of 13.8 kJ/g. The product had a low microbial count (1.54-2.31 log(10) cfu/g). The bacteria isolated belonged to the Bacillaceae (Genus Clostridium, and Bacillus), Streptococcaceae (Genus Streptococcus), Micrococcaceae (Genus Staphylococcus), and Corynebacterium. The product appears to be a nutritious and shelf-stable product.

Biogenic amines and potential histamine - Forming bacteria in Rihaakuru (a cooked fish paste).

The biogenic amine concentration in Rihaakuru (a fish paste) (n=28), obtained from different parts of the Maldives (North, South, and Central), was determined by HPLC. Ten biogenic amines were detected; agmatine, not detected (ND) - 161ppm; cadaverine, ND - 387ppm; histamine, ND - 5487ppm; putrescine, ND - 290ppm; phenylethylamine, ND - 23ppm; serotonin, ND - 91ppm; spermine, ND - 329ppm; spermidine, ND - 79ppm; tryptamine, ND - <5ppm; and tyramine, ND - 50ppm. Nine biogenic amines were found in 3 samples, 8 in 10 samples, 7 in 6 samples, 6 in 3 samples, 4 in 5 samples, and 1 was found in 1 sample. Histamine was detected at levels that are regarded as a risk to human health. Fourteen isolates were selected from two randomly selected samples out of the 28 samples of Rihaakuru and screened for histamine production. Twelve of the 14 isolates produced histamine, with the highest histamine producers being Bacillus massiliensis Nai5 (6.65ppm) and Bacillus polyfermenticus (5.58ppm); while Bacillus malacitensis produced the least (<0.5ppm).

Control of biogenic amines in food--existing and emerging approaches.

Biogenic amines have been reported in a variety of foods, such as fish, meat, cheese, vegetables, and wines. They are described as low molecular weight organic bases with aliphatic, aromatic, and heterocyclic structures. The most common biogenic amines found in foods are histamine, tyramine, cadaverine, 2-phenylethylamine, spermine, spermidine, putrescine, tryptamine, and agmatine. In addition octopamine and dopamine have been found in meat and meat products and fish. The formation of biogenic amines in food by the microbial decarboxylation of amino acids can result in consumers suffering allergic reactions, characterized by difficulty in breathing, itching, rash, vomiting, fever, and hypertension. Traditionally, biogenic amine formation in food has been prevented, primarily by limiting microbial growth through chilling and freezing. However, for many fishing based subsistence populations, such measures are not practical. Therefore, secondary control measures to prevent biogenic amine formation in foods or to reduce their levels once formed need to be considered as alternatives. Such approaches to limit microbial growth may include hydrostatic pressures, irradiation, controlled atmosphere packaging, or the use of food additives. Histamine may potentially be degraded by the use of bacterial amine oxidase or amine-negative bacteria. Only some will be cost-effective and practical for use in subsistence populations.