Ivan Chang-Yen

Nutritional and sensory quality of stirred soursop (Annona muricata L.) yoghurt

Soursops (Annona muricata L.) are highly aromatic fruits with white juicy flesh and are native to tropical North and South America. The ripe fruits are highly perishable, as they become soft and easily bruised. The objectives of the study were to incorporate soursop nectar at 0%, 5%, 10% and 15% in stirred yoghurts and to analyse the products for chemical and sensory quality. A focus group evaluated the initial yoghurts for process modifications. Yoghurts were evaluated on sensory attributes of appearance and colour, body and texture, flavour and aroma, and overall quality. Yoghurts with 10% and 15% soursop nectar had the highest (P<0.05) overall quality scores (12.60/20 and 12.75/20, respectively) but differed (P<0.05) in flavour and aroma from plain yoghurt and 5% soursop yoghurt. Most panelists would consider purchase of 10% and 15% soursop yoghurts over 0% and 5% soursop yoghurts. These yoghurts provided high percentage daily values of zinc, phosphorus and calcium and a good level of protein.

Distribution of selected heavy metals in skin and muscle of five tropical marine fishes

An investigation was carried out to determine the effect of tissue type, tissue location and size of fish on the heavy metal levels of five species of fish found in the marine environment of the tropical island of Trinidad. The study was conducted with the fish species Lutjanus synagris, Micropogon furnieri, Cynoscion leiarchus, Caranx hippos and Scomberomorus brasiliensis, and focused on the muscle and skin tissues of the fillet of these fish. The metals Fe, Zn, Cu, Ni, Pb, Cd and Cr were analysed by atomic absorption spectrophotometry after acid digestion of the tissues, but only Fe, Zn and Cu were detected. Skin tissue showed elevated levels of metals in comparison with muscle tissue, and significant differences in metal levels with respect to tissue location in skin, and varying effects of size on both muscle and skin metal levels in the different species, were found. These results emphasize the need for careful sampling of tissue in these fish species if reliable data on heavy metal levels are to be generated.

An evaluation of the extraction efficiencies of some common extractants for Fe, Cr, Mn, Ni, Pb and Cu on five grain-size fractionated, tropical marine sediments.

A number of extractants and extraction procedures were evaluated using a variety of tropical marine sediments fractionated on the basis of grain size. Total metal levels obtained by X-ray fluorescence analysis were used in the normalization of levels obtained by these extractants/extraction procedures. A change in extraction efficiency with change in the pH of the extractant used was observed for Fe and Mn irrespective of particle size of the fraction. Iron was extracted uniformly at each leaching level for the <53micro fractions. Manganese had comparable extraction efficiencies with both weak and strong extractants. The extraction efficiencies for Cr were generally low possibly due to an association with the residual phase. The ease with which both Pb and Ni were extracted indicated that they were only loosely bound in the sediments. The extraction efficiencies for Cu varied widely for the fractions of larger particle sizes but fell within narrow ranges for the <53micro fractions.

Lead pollution in East Trinidad resulting from lead recycling and smelting activities.

Several problems of acute lead poisoning in children have been identified over the past three years in Trinidad. In all cases investigated so far, continual exposure to lead from battery recycling or from lead-smelter wastes have been found responsible. In East Trinidad, illicit dumping of lead wastes from such sources has resulted in several sites becoming heavily contaminated. Some of these sites are in environmentally sensitive areas, including rivers and wetlands, and require urgent remedial action. Results of monitoring studies at several of these sites show lead levels as high as 75% by weight. The potential for surface and ground water contamination exists, as evidenced by leaching of lead into surrounding areas.

SOURCE IDENTIFICATION OF AN OIL SPILL ON TRINIDAD'S EAST COAST

ABSTRACT In April 1986, a large quantity of unrefined crude oil was released into the nearshore marine environment on Trinidads east coast. The oil was observed to have affected approximately 20 kilometers of coastline. Physical examination of the oil collected revealed that it had the appearance of a light grade crude, was golden brown in color, and had a characteristic gassy odor. Also observed was a mass mortality of the bivalve Donax sp (chip-chip), which inhabits sandy areas of the intertidal zone. Oil was extracted from samples of water, beach sand, and chip-chip collected from selected stations along the affected area. Also collected were samples of oil from possible sources located both offshore and at land-based facilities. Chemical characterization of the oil extracts, using capillary gas chromatography, atomic absorption and fluorescence spectroscopy, and carbon-13 nuclear magnetic resonance spectrometry, yielded data sets that distinguished the oils in the environment from the suspect source ...