Trace element solubility from food following enzymolysis.

Food items were treated with enzymes simulating gastric and intestinal digestive juices and the amounts of soluble lead, cadmium, zinc, iron, and copper, were determined. Enzyme treatment was conducted in two stages involving (I) pepsin at pH 2,5 followed by (II) pancreatin and amylase at neutral pH. Solubility was determined after each stage and additionally after post enzymolysis acidification. The foods examined comprised wholemeal bread, spinach, canned tomato, ox liver, pig kidney, canned crabmeat, beefburger, and canned corned beef, the last sampled from within the bulk and adjacent to the side seam of the can. Analyte solubility varied with (I) different food items, (II) processing or preparation of foods of similar origin, (III) action of pepsin or pancreatic enzymes and (IV) pH. Reasons for the variations are discussed.

Comparison of trace element solubility from food items treated separately and in combination.

Solubility of trace elements from various foods (beef, soya, crab, wholemeal and white bread) is assessed with various extractants, at different pH's and after enzyme treatment. Simple extractants do not solubilise trace elements to the same degree as when they are released after digestive enzyme action. Enzymic action can change the nature of the soluble species as well as their amount. Trace element solubility from one food can be affected markedly by the presence of another food, e.g. soya enhances the solubility of iron from beef but suppresses zinc solubility. Trace elements that are bound to the insoluble residue after enzymolysis are soluble in saline solution on subsequent extraction in only isolated instances.

The aluminium content of infant formula and tea.

Tea and infant formulae have been examined for the presence of aluminium. Concentrations in 13 different tea infusions ranged from 2.2 mg/l to 4.5 mg/l. In cow's milk-based infant formulae as made up for consumption, aluminium levels of between 0.03 mg/l and 0.20 mg/l were detected. Higher amounts were present in soya-based formulae with concentrations ranging from 0.64 mg/l to 1.34 mg/l.

Aluminium levels in milk and infant formulae.

Aluminium levels in infant formulae purchased in 1990 and prepared as for consumption were in the range 530 micrograms/l to 640 micrograms/l for soya-based products and 27 micrograms/l to 120 micrograms/l for cows' milk-based formulae. Mean aluminium concentrations in these soya and cows' milk-based samples were, on average, 37% and 45% lower, respectively, than those of the same brands purchased between 1985 and 1987. Levels of aluminium in breast milk were in the range 3 micrograms/l to 79 micrograms/l. In the case of retail cows' milk, values ranged from 4 micrograms/l to 33 micrograms/l whilst more variable amounts of between 5 micrograms/l and 285 micrograms/l were detected in retail soya milk.

Lead contamination during domestic preparation and cooking of potatoes and leaching of bone-derived lead on roasting, marinading and boiling beef.

Lead concentrations were measured in boiled, mashed potatoes and in baked potatoes that had been prepared and cooked in domestic kitchens. Levels of lead in the boiled, mashed potatoes ranged from below the 1 microgram/kg limit of detection up to 18 micrograms/kg with a mean of 6 micrograms/kg (wet weight). In the large majority of cases the lead in the tap water was the predominant source of the metal. Higher amounts of lead (range 11 micrograms/kg to 56 micrograms/kg, mean 27 micrograms/kg) were present in baked potatoes and this was attributed to soil adhering to the potato skin. The extent of leaching of lead from bone during cooking has also been investigated. For beef stocks there was little evidence to suggest that significant migration of bone lead occurred. For beef casseroles, marinaded in red wine, some leaching did occur from beef joints containing elevated amounts of bone lead; however the levels were all below 350 micrograms/kg and, on average, less than double that found in casseroles prepared from normal joints where the bone lead levels were an order of magnitude less.

A procedure for the determination of lead in green vegetables at concentrations down to 1 microgram/kg.

An accurate and highly sensitive dry ashing/graphite furnace atomic absorption spectrometry (GFAAS) procedure has been developed for the measurement of lead in green vegetables. The accuracy of the method was established by analysis of standard reference materials and confirmed by isotope dilution using an inductively coupled plasma-mass spectrometer (ICP-MS). The limit of detection (wet weight) of the technique is 1-3 micrograms/kg with relative standard deviations ranging from 6% for a sample of kale containing 500 micrograms/kg to 20% for cabbage containing 3.0 micrograms/kg.

Lead in feed incident--multi-element analysis of cattle feed and tissues by inductively coupled plasma-mass spectrometry and co-operative quality assurance scheme for lead analysis of milk.

Contaminated cattle feed was imported into the UK in 1989 and resulted in lead toxicity in some animals. Rapid analyses for lead and several other possible contaminating elements were required for feed and cattle tissues. Microwave dissolution of samples with measurement by ICP-MS was used for multi-element determinations. Lead was found to be the major contaminant. Lead levels in milk samples were measured by several laboratories during the crisis and an analytical quality assurance scheme was devised to monitor the quality of the data. The scheme allowed any poorly performing laboratories to be rapidly identified and excluded from the survey.