CHALLENGE STUDIES WITH CLOSTRIDIUM BOTULINUM TYPE E IN A VALUE-ADDED SURIMI PRODUCT STORED UNDER A MODIFIED ATMOSPHERE

Challenge studies were carried out on raw, cooked, and sterilized surimi nuggets, inoculated with 10⁴ spores/g of C. botulinum type E spores. All products were packaged in air and air with an Ageless SS oxygen absorbent and stored at 4, 12 and 25C. Toxin was not detected in any raw product throughout storage (28 days). The absence of toxigenesis was attributed to the low pH (4.1–4.3) due mainly to the growth of lactic acid bacteria (10⁷CFU/g). Toxin was also not detected in any cooked product after 28 days. Product pH did not decrease as previously (due to the absence of LAB), but counts of C. botulinum still decreased throughout storage.
In sterile nuggets , C. botulinum counts increased to 10⁶ cfu/g at both 12 and 25C, respectively, by 28 days. Lactic acid bacteria and Bacillus spp. were not detected throughout the 28 days storage period. Toxin was detected by days 28 and 14 at 12 and 25C, respectively, and toxigenesis preceded spoilage. The absence of toxin in cooked nuggets was attributed to the anti-botulinal role by Bacillus species, the predominant spoilage bacteria in cooked nuggets.     

High-pressure-induced changes in bovine milk: a review

High-pressure (HP) treatment of food products is a novel processing technique during which the product is treated in a vessel of suitable strength at a high pressure, generally in the range 100–1000 MPa. As a result, several constituents and properties of the treated product are altered. HP-induced changes in the constituents and properties of milk are arguably among the most extensive of the range of food products studied to date. HP treatment of milk induces solubilization of minerals associated with the casein micelles, denatures whey proteins and, depending on pressure, can either induce aggregation or disruption of the casein micelles. These HP-induced changes in milk constituents affect the properties of the milk; cheesemaking properties of milk can be enhanced considerably, indicating potential application of HP treatment in this area; furthermore, encouraging results have also been reported for HP treatment of milk prior to yogurt manufacture. HP treatment of milk also affects its microflora; however, considerable variation in baroresistance between bacterial species and strains exists. Further applied research appears warranted to establish the full commercial potential of HP treatment of milk.     

Variation in the Levels of Sodium and Other Minerals of Nutritional Importance in Louisiana Oysters (Crassostrea Virginica)

The concentrations of nine individual minerals were determined in oysters harvested over a 10-month period. Significant (p > 0.01) monthly variations were observed in the levels of all the minerals determined. Salinity of the growing waters was significantly (p > 0.01) correlated to levels of sodium, magnesium, iron, chromium, and nickel in the oysters. Levels of potassium, copper and chromium were related to pH. Zinc and iron levels were correlated (p > 0.05) to water temperature. In this study, variations in the mineral content of oysters were often directly influenced by the growing water. This variation must be taken into consideration, should sodium labeling be required for fresh oysters.     

Adsorption of Gas-Phase Phenanthrene on Atmospheric Water and Ice Films

The adsorption of gas-phase phenanthrene on atmospheric water and ice films was investigated in a flow-tube reactor with a view to understanding the processing of semi-volatile organic compounds by fog and snow. Air-water (ice) interface partition constants were obtained by measuring the mass uptake of phenanthrene vapor on thin water and ice films with varying thickness. Adsorption enthalpies and entropies were obtained from the temperature dependence of the interfacial partition constants. The surface adsorption is the predominant mechanism for the uptake of phenanthrene in water and ice films with small film thickness or at low temperature. The adsorption of phenanthrene to ice resembles that to sub-cooled water and there's no significant difference between the adsorption of phenanthrene to water and that to quasi liquid layer (QLL) if we take into account the uncertainties on the thermodynamic quantities measured. Molecular dynamics simulations of phenanthrene at air/water and air/ice interfaces support these experimental observations. The interfacial air-water and air-ice partition constants of phenanthrene increased greatly in the presence of surface-active substances, indicating that surface active materials effectively enhanced the uptake of organic compounds by atmospheric water and ice films.