To evaluate the base line levels of potentially toxic and essential trace metals namely, Cd, Ph, Cr, Mn, Ni, Cu and Zn in water, locally grown vegetables, cereals and vegetable ghee-oil samples of a highly industrial city Gujranwala have been measured after wet digestion by employing AAS technique. Sampling was made from selected sites in and around the city over a period of three months. The concentration of Mn, Ni, Zn, Cu and Pb was found significantly higher in vegetables ranging from 3-63, 2-81, 5-92, 7- 70 and 6-60 ppm respectively. Nickel and Cu concentration was found higher in cereals whereas, Cd was found at ppb level in all variety of samples studied. Tap water, vegetable ghee-oil have recorded lower concentration of these metals. Vegetables collected from urban area have shown elevated level of contamination than those of taken from canal irrigated farms. The overall level of trace metals with few exceptions of vegetable samples was found within the permissible limits fixed by WHO. The analytical method was checked by applying on SRM of wheat and spinach. The results were found in agreement with the certified values within experimental error. The major polluting sources of the city such as automobile, man made activities, soil and road dust, metallic corrosion and industrial activities have been indicated. The environmental impacts of pollutants on water and food quality of an industrial and non-industrial city are briefly discussed in the light of their adverse effects on human health.

Steam injection heating systems for food and agricultural products are subject to condensation-induced water hammer (CWH), which may cause significant damage to equipment and pose a threat to operators. A method is suggested for process design and operation of a steam injection heater that reduces occurrence of CWH. The method is based on a correlation between the thermodynamic ratio of the product and the Peclet number. A laboratory steam injection heater was instrumented to determine the relationship between CWH, the thermodynamic ratio, and the Peclet number. The thermodynamic ratio for water and various concentrations (55 to 67.5 brix) of sucrose solution was recorded under process conditions at the onset of CWH during steam injection heating. Good correlation was observed between the Peclet number and threshold thermodynamic ratio. A linear equation was found (with r 2 = 0.79) that gives the predicted minimum thermodynamic ratio for system operation without CWH.