Studies on aluminium leaching from cookware in tea and coffee and estimation of aluminium content in toothpaste, baking powder and paan masala

The Science of the Total Environment 193 (1997) 243-249

Studies on aluminium leaching from cookware in tea and coffee and estimation of aluminium content in toothpaste, baking powder and paan masala Poonam Rajwanshi”, Vibha Singh”, M.K. Gupta”, Vinita Kumari”, Rohit Shrivastav”, M. Ramanamurthyb, Sahab Dass”,* ‘Department

of Chemistry, Faculty bAnalytical

of Science, Dayalbagh Educational Institute, Da.valbagh. Chemistry Division, B.A.R.C., Bombay 400085, India

Agra

282 005, India

Received 16 March 1996; accepted 23 October 1996

Abstract Studieswereconductedin order to assess the level of aluminium (Al) in samplesof Indian tea, coffee, toothpaste, paan masala(mouth freshener)and baking powder. Leachingof Al from cookware while preparing tea and coffee wasalsostudied.Experimentswerealsoconductedto study the sequentialleachingof Al from cookware by preparing tea and coffee in the presenceof standardsizeAl sheets(coupons).A smallamount of Al wasfound to have leached from couponsduring preparation of tea. Tea leaves,were found to be a rich sourceof Al and a maximum of 2.2% Al is extracted in tea infusions.Coffee powda on the other hand was not found to be a rich sourceof Al. Baking powder was found to be a rich sourceof Al and 1 kg of cake prepared with l-3 teaspoonof baking powder may contain 2-12.7 mg of Al in each serving(25 g). Toothpaste alsocontainsa significantquantity of Al, more so, when packedin Al tubes. ingestionpattern of Al from theseitemsby humansis alsodiscussed.Copyright 0 1997Elsevier ScienceB.V. Kqwords:

Tea; Coffee; Toothpaste; Aluminium leaching; Cookwaresand cooking

1. Introduction On account of low absorption across the human gastrointestinal tract, aluminium (Al) was earlier not considered to have any adverse effect * Corresponding author.

on human health. However, in medical reports published recently, the possible association with various diseasessuch as dialysis encephalopathyj dementia, [l] osteomalacia, fractures and or high levels of bone Al [l-3] and Alzheimer’s disease [4,5] for which an excessive intake of Al in the human body has been hypothesized. A real associ-

0048-9697/97/$17.00 Copyright 0 1997 Elsevier Science B.V. All rights reserved HI

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244

P. Rufwanslri

VI 01. I: T/w Science

qf the Total

ation of these disorders with an excessive intake of Al in the human body however, is still not clear, especially in the case of Alzheimer’s disease

WI. Various contributors of Al to human diet are, food containing natural Al, Al containing food additives and Al from contact of food with containers. cookware, utensils, cans and foil wrappings. Although the Al content naturally present in food is very low [7LlO], many items such as baking powder, cheese and pickled vegetables are known to contain substantial amounts of Al from Al containing additives [8,9], which are therefore considered to be a major source of dietary Al intake [8,9,1 1~121. Greger [I 1] has estimated that an average daily intake of Al from food-additives in American diets could be 20-25 mg and a total diet study has revealed that the average daily intake of Al from food stuffs in U.K. is 3.9 mg [13]. WHO:FAO [14] expert committee on food additives has established a provisional tolerable weekly intake (PTWI) of 7 mg Al/kg of body weight. During 1987. Tennakone et al.. [15] described a 1000 fold increase in Al leaching from utensils in the presence of 1 ppm fluoride. Subsequent research [ 16- 181 demonstrated only minimal enhancement of Al leaching in the presence of fluoride. Tennakone et al. [19] recognized the error in reporting high values after re-experimentation and it was confirmed that a minimal increase in leaching of Al occurs in the presence of 1 ppm fluoride. but leaching becomes significant at 10 ppm fluoride and above 1193. Results of an exhaustive study carried out on leaching aspects of Al by our group indicate that pH rather than fluoride content of the cooking medium, plays a significant role in leaching [20]. Tea leaves are known to naturally contain high levels of Al since the tea bush accumulates large quantities of Al from acid soil. The black tea is reported to contain between 500 and 1900 mg Al/kg [17,31 -2.51. Fairweather-Tait et al., [17] reported extraction of 26-39% Al from tea leaves during preparation of tea infusions containing 2.7 4.9 mg/l .41. Different forms of Al in tea leaves and tea infusions hal,e been reported [26,27]. Yamada and

Em+ronmmt

193 (1997)

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Hattori [26] reported that Al forms complexes with fluorides in tea leaves and tea infusion while Nagata et al. 1271 suggested that most of the Al in tea was bound to catechins. Flaten and Odegard, [24] have pointed out that most of the extractable Al in brewed tea is strongly bound to organic species (theaflavins, thearubigins and other polyphenolic fermentation products) and that these high molecular weight complexes are not readily absorbed across the gastrointestinal tract. French et al., [28] have suggested that complexation plays an important part in Al speciation in tea, even under simulated gastric conditions. Farrar and Blair, [29] have reported that tea tannins reduced the absorption of 67Ga, which is a marker of Al, in both nourished and starved rats, suggesting that the component in tea may have an inhibitory effect on Al uptake from other dietary sources. The adverse effect of tea on iron bioavailability is well known [30,31]. The present study deals with the estimation of total Al content in various Indian tea and coffee samples and the percentage leaching of Al on brewing tea in Al cookware. To observe the effects of differences in surface topography (shape) and quality of material used in different saucepans on metal leaching, another study was conducted using Al coupons of standard size, drawn from the sheets used in utensil manufacturing. Four sequential leachings on each coupon were also performed to understand the pattern of Al leaching on repeated use of Al cookware during cooking. Moreover, total Al content in certain food items, viz. toothpaste (packed in Al and plastic tubes), paan masala (mouth freshener containing lime, cathechu and areca nut, with and without tobacco) and baking powder were also measured.

2. Experimental Al sheets used in the study supplied by the Indian Aluminium Company (Bombay) were of 1.5 mm thickness (2s alloy conforming to IS 19 000 equivalent to AA 1200 used in utensil making). The sheets (drawn from the same lot) were cut into plates of uniform size, 2 x 3 in.

(coupon). Four samples of tea and two samples of coffee (250 g each) were obtained from the local market. Tea in sample 1 was of a leafy variety while others were of a granular type. Tea and coffee samples were analyzed for total Al content using a procedure described by Koch et al., [32]. Tea and coffee samples (0.5 g each) after drying for 24 h in an oven, were powdered and digested with 4 ml 14 M nitric acid and 1 ml 12 M perchloric acid by heating for 30 min until no brown oxides of nitrogen evolved and the solution began to give off white fumes. The solution was transferred to a 50 ml calibrated flask and was diluted to the mark with distilled water. It was then stored in precleaned polyethylene bottles for analysis of Al. Using double distilled deionized water (conductance 2.0 ,&), throughout the study, the experiments on Al leaching were performed in triplicate. The glassware and plasticware were washed with nitric acid (10% v/v) and distilled water before use.

3. Tea and coffee infusions in Al coupons

Samples of tea and coffee infusions were prepared by placing the Al coupon in 200 ml double distilled water in a 250 ml glass beaker (Borosil). It was then allowed to boil for 10 min after which 2 g of tea leaves were added and left to boil for another 2 min. Coffee infusions were prepared by adding 1 g of coffee powder to the boiled distilled water. After a contact time of 5 min for both tea and coffee. the Al coupon was removed and the volume of liquid was noted after cooling. The solution was then transferred into precleaned polyethylene bottles for the analysis of Al content. Each coupon was boiled four times to study the effect of successive use of utensils on Al leaching. A blank set without the Al coupon was also prepared for each sample in order to determine the Al content in tea and coffee infusions in the absence of the Al coupon.

4. Al in food samples

A few selected food stuffs, viz. tea, coffee, toothpaste, paan masala, baking powder were procured from the local market. Five samples of toothpaste (packed in Al/plastic tube), six samples of paan masala (with/without tobacco) and three samples of baking powder were obtained from the local market. Paan Masala and toothpaste samples were analyzed following the earlier reported procedure of Koch et al. [32]. The Al content in baking powder was analyzed following the method reported by Holak et al. [33]; 1.0 g of the sample was digested with 2.0 ml sulphuric acid and 3 ml (30%) hydrogen peroxide. When the initial vigorous reaction was reduced, a bunsen flame was applied until samples began to char. Hydrogen peroxide (1 ml) was then added and heated until the soiution no longer charred. Distilled water (25 ml) was added after the solution cooled, the solution was then boiled for 3-5 min. The solution after filtration was diluted to a total volume of 50 ml and stored in precleaned polyethylene bottles for analysis. On account of the non-availability of standard reference material, a known amount of dissolved Al was added to samples which gave a recovery of 94 (S.D. 5.5X), 92 (SD. 6.5%)) 98 (S.D. 7.3%) and 99% (S.D. 3.2%) for tea and coffee, toothpaste, paan masala and baking powder, respectively. Reagent blanks were also included along with a different batch of samples and these blanks equated to a mean of 0.008 mg/kg (range, 0.002-0.1023 mg/kg) with a standard deviation of 0.078 mg/kg. Limit of detection was defined as three times the standard deviation of the reagent blanks which corresponded to 0.23 mg/kg.

5. Al estimation

Al was determined in all the samples using a direct current atomic emission spectrophotometer (Beckman Spectraspan V) under the following conditions: argon flow rates: sleeves, 50 psi; nebuliser, 20 psi; slit: entrance, 50 x 300 fm;

246

P. Rajwanshi

Table 1 Aluminium Sample

content no.

Dry

et al. i The Science

in tea and coffee

with

weight

SD.

Infusions

Lag/g)

aluminium

Tea I 2 3 -I

599 634 704 633

kl68 +34 i58 1141

11 13 13 14

Coffee 5 6

396 458

_+I3 kl28

8 6

of’ the Total

Enoironment

193 (1997)

243-249

coupons (ppm)

exit, 50 x 300 fm; PMT voltage, 500-600 V; signal integration: time, 5 s; repeats, 3 s; wavelength, 369.1 nm. Calibration was performed using standard (0.1 and 2.0 @g/ml) solutions prepared from the pure metal. Two standards (0.1 and 2.0 pg/ml) were used for the calibration. A preliminary scan was carried out for a few typical samples using the dynamic background corrector (DBC 33). No background correction was found to be necessary. The calibration standards were run between every six samples to check and correct for any drift in the calibration.

6. Results and discussion 6.1. Totul Al content irl teu and coflhe The amount of total Al content found in various brands of tea leaves and coffee powder are given in Table 1 and range between 599 and 704 /Agig in tea and between 396 and 458 ,ug/mg in coffee. There is very little variation in the Al content among different brands of tea and coffee. In leafy variety tea (sample 1) a marginally lower amount of Al content has been found.

Table 3 indicates that Al content in tea infusions of samples I, 2. 3 and 4 without Al coupon (i.e. blank value) and in the case of four sequential lcachings (with Al coupon) ranged between

S.D.

Al per cup (100 ml) (mg)

Al extracted

& 1.5 kl.1 f I.0 +2.0

1.1 1.2 1.3 1.4

1.7 3.0 1.8 3.2

kl.2 il.5

0.8 0.6

1.9 1.3

(x,)

9.0-13.0, 11.8-14.5, 11.4413.8 and 11.4416.3 ppm, respectively. Al leached out from coffee for blank, first, second, third and fourth leachate in samples 1 and 2, respectively, ranged between 6.8-9.7 and 4.7-8.4 ppm. Al concentration for all the five sets i.e. blank (without Al coupon), first, second, third and fourth leachate was found to be in a similar range. The mean Al concentration obtained for different brands of tea infusion samples, without Al coupon, ranged between 9 and 15 ppm which is lower than the values of 40-100 ppm reported by Coriat and Gillard [21], but somewhat higher than the values reported by Gromican (2.4 ppm) [34], Greger (4.6 ppm) [ll], Koch et al. (4.4-6.0 ppm) [32] and Flaten and Odegard, (2.0-6.2 ppm) 1241. The Al content in coffee infusion was lower than in tea infusions (6-8 ppm). Marginally lower concentrations of Al was observed for a leafy variety of tea (sample 1) compared to tea leaves with a smaller grain size. In general, less Al leached out during the second leaching than in the first, while the third and fourth leachings yield a higher amount of Al than the second leaching, but less than that in the first leaching. Average values of Al in tea infusions calculated in four samples of tea ranged between 11 and 14 ppm as shown in Table 1 and the percentage extraction of Al from various samples ranged between 1.7 and 2.2%. Consecutive leaching in the case of coffee (sample 1) exhibits an almost similar range except for a jump in the second leaching, while in sample 2, 2nd, 3rd and 4th leachings are similar and significantly lower than the first leaching (Table 2).

P. Rajwanshi Table 2 Sequential Sample

leaching no.

Tea I 2 3 4 Coffee I 2

of aluminium

et al. 1 The Science

@g/ml)

in tea and coffee

of the Total

infusions

with

193 (1997)

aluminium

243-149

241

coupons

Blank

SD.

I

SD.

II

SD.

III

S.D.

IV

S.D.

9.0 11.8 13.8 14.6

+ 0.02 +I.26 +0.15 j-2.07

10.4 14.5 13.7 16.2

k1.34 1-2.26 50.26 10.75

11.1 12.0 11.4 15.6

k3.71 kO.25 kO.78 22.36

10.1 12.2 13.2 11.5

+0.44 i-l.24 +0.65 jrO.80

13.0 12.2 12.8 12.5

+0.12 +3.53 kO.81 +0.35

6.8 7.0

50.74 il.45

7.2 8.4

kO.35 i2.06

9.1 4.7

+2.06 k1.06

7.1 5.8

+0.64 *4.19

7.3 5.1

+3.22 +3.61

The study indicates that negligible amounts of Al leach out from Al coupons when boiling tea leaves and the Al present is mainly due to the Al already present in tea leaves. The results also indicate tea as a rich source of Al mainly due to the Al accumulating property of the tea plant. Boiling tea and coffee in Al utensils does not cause a further enrichment in Al content of tea. In the same context sequential leaching has a negligible effect on enhancement in Al content of tea infusions. The variation in Al content of different brands of tea and coffee samples reflects the variation in Al content in soil, air, water around the plantation area and type of plants. 6.3. Food

Environment

item

Al concentration obtained in toothpaste, paan masala and baking powder are shown in Table 3. The toothpaste packed in Al tubes were selected in order to observe the effect of Al tube on the Al content of the toothpaste. To clearly understand the effect of packing material, one set of toothpaste with plastic tube packing was also selected for the analysis. The Al content of toothpaste of a particular brand, packed in an Al tube was found to be 7.60 mg/g while in a plastic tube it was found to contain 5.47 mg/g. In different brands of paan masala, Al content ranged from 1.17 to 2.10 mg/g. In paan masala without tobacco, the Al ranged between 1.17 and 1.89 mg/g, while in paan masala with tobacco, Al content ranged between 2.0 and 2.10 mg/g. In the case of baking powder samples, the concentration of Al was significantly higher. The

values obtained for samples 1, 2 and 3 were 33.82, 24.01 and 16.43 mg/g, respectively. Our results are in agreement with those of Holak [33,35] who reported Al concentration in baking powder to range between 19.15 and 26.00 mg/g.

Table 3 Aluminium pattern Sample

content

no.

Tooth paste I (Al packing) 2 (Al packing) 3 (Al packing) 4 (Plastic packing) 5 (Al packing) Paan masala 1 (without tobacco) 2 (without tobacco) 3 (without tobacco) 4 (without tobacco) 5 (with tobacco) 6 (with tobacco) Baking 1 2 3

in various

food

items

and their

Al (mgk)

Ingestion”

7.12 10.64 7.31 5.47 7.60

2.8 4.3 2.9 2.2 3.0

1.29

1.3

1.35

1.3

1.17

1.2

1.89

1.9

2.10 2.00

2.1 2.0

(20%)

ingestion

(mg)

powder 33.82 24.01 16.42

n Assuming total intake, per incident, masala as 2 and 5 mg, respectively.

of tooth

paste and paan

24x 6.4.

P. Rajwanshi Ingestion

of’

et al. / The Science

of’ the Total

Al

6.4.1. Tea und coffer

Tea is a rich source of Al as compared to coffee. Per cup (100 ml capacity) Al ingestion from tea prepared with coupons would range between 1.1 and 1.4 mg. In the same context consumption of five cups of tea per day would expose a person to 5-7 mg of Al (Table 1). According to Koch et al., [32], consumption of 1.2 1 tea/day markedly increases the amount of Al excreted in the urine which indicates that some chemical form of Al present in tea is readily absorbed. They have also noted that most of the Al present in tea infusions is complexed with organic molecules and that larger complexes are less bioavailable than smaller ones [32]. The ingestion of Al through coffee ranges from 0.6 to 0.8 mg per cup. Therefore, consumption of five cups of coffee per day would expose a person to 3-4 mg of Al. 64.2. Toothpustr

Considering 20% toothpaste ingestion per brushing (2 g being used per brushing) the Al available for absorption has been calculated and values obtained indicate that toothpastes provide Al in the range of 2.2-4.3 mg per brushing. The amount of Al present in toothpaste can be attributed to aluminium oxide present as an ingredient in the toothpaste and due to the packaging in the Al tube. 6.4.2. Puun tllasaln

The ingestion pattern of paan masala can be accounted for in the same manner as that of toothpaste and the values calculated are given in Table 3. Al available for absorption per sachet (containing 5 g of paan masala) without tobacco and with tobacco range between 1.2 and 1.9 mg and 2 and 2.1 mg, respectively. Consumption of four sachets per day would expose a person to 4.7--X.4 mg of Al.

One teaspoonful of Al containing baking powder will contain 8L 169 mg Al. The results obtaIned are in agreement with values obtained

Environment

193 (1997)

243-249

by Ellinger [36]. Cake (1 kg) prepared with l-3 teaspoonfuls of an Al containing baking powder may contain 2- 12.7 mg Al in each serving (25 g)*

7. Conclusions

This study indicates tea to be rich in Al which provides between 2.7 and 4.2 ppm of the metal in infusions. The leafy variety contains less Al. Coffee on the other hand is not rich in Al. Ingestion of Al per cup through tea and coffee ranges between 1.l and 1.4 mg and between 0.6 and 0.8 mg, respectively. The study also highlights the insignificant role of fluoride in Al leaching as tea infusions are known to be fluoride rich [37]. Al content obtained in various brands of toothpaste ranged between 5.47 and 10.64 mg/g. The ingestion of Al from toothpaste per brushing, considering 2 g toothpaste used per brushing and 20% of it is ingested, ranged between 2.2 and 4.3 w. In the case of paan masala the Al content ranged between 1.2 and 2.1 mg/g in different brands studied. The ingestion of Al through paan masala per sachet considering the 5 g paan masala in one sachet and its 20% ingestion, ranged between 1.2 and 1.9 mg and between 2.0 and 2.1 mg in paan masala, with and without tobacco, respectively. In the case of baking powder, where Al is one of the main ingredients, Al content was found to be between 16.42 and 33.82 mg/g. One teaspoonful of baking powder will therefore contain approximately 82- 169 mg Al.

Acknowledgements

Authors thank Professor Satya Prakash, Head, Chemistry Department, for constructive suggestions and providing necessary facilities. Financial support given by DST, New Delhi, is gratefully acknowledged. Thanks are also due to Mr. Gurusharan Prasad and Mr. Santosh for overall assistance.

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