Metal Concentrations of Water and Food Cooked in Various Cooking Pots

Abstract

Migration of heavy metals from cooking pots into water and food during cooking was investigated.  Five foodstuffs and nine cooking pots were used.  Water was boiled for 6 m while the various foodstuffs were cooked for varying lengths of time to doneness.  Seven metals, namely Aluminum, Arsenic, Mercury, Lead, Cupper, Iron and Nickel were determined using spectrophotometer. The metal content of boiled water was significantly (p<0.05) higher than the unboiled water. Metal migration from the pots increased (p= 0.05) when sodium bicarbonate was introduced to the boiling water (pH 10.5). Migration of metals from pot into the cooking substances was lowest in Titanium steel cooking pot followed by enamel pot and lastly by Aluminum pot.  We discovered that generally cooked food samples had higher content of the metal elements compared to control samples, confirming that cooking pots can leach trace metals into food during cooking/processing depending on the materials they are forged with.  Aluminum pots leached the highest quantity of Al ions, with the older pot leaching more (0.98mg/L) than the new one (0.56mg/L) in boiled water extracts.  The metals observed to have migrated from some pots at levels exceeding the standard limits were Al, Ni and Fe ions.  Other leachates such as arsenic, mercury, lead and copper from the various pots were negligible. Some of the pots maintained a pattern of metal leaching irrespective of the food they were used to cook while others were affected by food type.  Our work has demonstrated that the problem of metal leaching is more or less arising from the pot; though food type affected their leaching.  Our results support the need to regulate the quality materials used to manufacture cooking pots.