Inorganic Composition

Table 7.1 summarizes measured concentrations of 27 elements in 10 nut and 2 seed varieties. This selection covers essential, potentially essential, and toxic elements. For potassium, phosphorus, magnesium, calcium, iron, and zinc, national nutritional tables and textbooks on nutrition were used as primary sources (i.e., FNIC, 2009; Institute of Medicine, 2009). When concentration data provided by different tables were entirely identical for all elements and all nut and seed varieties, only one set was used in the calculations. For the remaining elements, relevant publications on the inorganic constituents of nuts and seeds provided the bulk of the data (Waheed et al., 2007; Rodushkin et al., 2008 and references therein; Welna et al., 2008 and references therein; Yang, 2009).

The number of collected data sets varies greatly, both between different nuts/seeds and between analytes, with the general trend of the least data being available for trace elements and less common specimens — specifically, pecans, pistachios, pine nuts, and pumpkin seeds. These trends reflect differences in either nutritional or toxicological significance, as well as analytical challenges related to measurement at trace levels. In total, data from more than 60 independent data sources were used for this compilation. When three or more independent values were available for a given element in a given nut or seed variety, and the ratio between maximum and minimum concentrations was below 10, the median concentration is presented together with the RSD (%). For two available sets of data, or when the range of reported concentrations for a given element exceeded an order of magnitude, the concentration range is used instead. In some cases, only a single value was available.

As a rule, RSD values below 30% are typical for the majority of essential element concentrations (potassium, phosphorus, magnesium, calcium, iron, zinc, copper, and manganese), confirming the low variability between nut or seed compositions harvested in different locations (Rodushkin et al., 2008) and the fact that the accurate determination of macro elements in these matrices has been possible for decades (Mitchell & Beadles, 1937). However, given that even changes in the degree of dehydration during storage can provide concentration variations in excess of 5% RSD for nuts or seeds from the same location, the praxis of providing concentration information in some nutrition tables with three or even four significant figures seems questionable. The spread in reported values for trace elements is considerably greater than 30% RSD, reaching several orders of magnitude in some cases (e.g., mercury in Brazil nuts). There are several potential reasons for these variations:

• differences in soil composition, climate, and agricultural practices (e.g., use of fertilizers). These factors were shown to be responsible for variable concentrations of selenium, barium, and radon in Brazil nuts (Parekh et al., 2008), cadmium in sunflower seeds (Andersen & Hansen, 1984), and aluminum in pecans (Rodushkin et al., 2008)

• contamination during shelling, peeling, handling and packaging — for example, contact with unprotected skin may significantly alter sodium and chlorine concentrations in almonds, hazelnuts and walnuts

• analytical artefacts, including incomplete recovery of elements from the samples during work-up, inadequate control of and correction for laboratory contamination, and failure to recognize and account for non-specificity of the instrumental analysis. The potential for such sources of bias increases for analytes present at concentrations close to or at the detection limits for such techniques as flame AAS or ICP-OES. In spite of developments in analytical instrumentation, providing reliable data at low or sub-mg/g concentrations still represents a significant challenge.

n 73

TABLE 7.1 Concentration of Elements in Pine Nuts

Elements

Hazelnuts

Walnuts

Almonds

Pecans

Cashews

Brazil Nuts

Pistachios

Pine nuts

Peanuts

Coconuts

Pumpkin

Sunflower

(No. of

Seeds

Seeds

Sources)

Essential Elements

K(6—14)

7100(10)

4800(20)

7300(5)

4700(20)

6600(20)

6300(10)

10000(5)

6700(10)

6700(10)

6000(30)

8100(5)

5900(30)

P(6—15)

3100(20)

3900(10)

5300(20)

3100(20)

5600(10)

6900(10)

4900(10)

6300(10)

4300(20)

1800(20)

11000(10)

7700(20)

Mg(6—13)

1600(10)

1600(10)

2800(5)

1300(10)

2800(5)

4100(10)

1300(5)

2500(10)

2000(10)

900(40)

5300(5)

4000(10)

C (6—11)

1400(10)

1000(20)

2500(5)

720(> 50)

410(10)

1700(20)

1100(20)

130(30)

540(20)

200(50)

430(5)

1000(20)

Na(4—7)

30(> 50)

10(> 50)

60(> 50)

5(> 50)

110(30)

30(> 50)

30(40)

30(> 50)

20(> 50)

370(10)

180(40)

30(50)

Cl(1—3)

60

70

100(5)

100

200(> 50)

100

200(> 50)

600(> 50)

250(> 50)

50

20

30

Fe(5—14)

39(20)

33(20)

41(20)

25(10)

64(5)

27(20)

50(30)

55(10)

24(20)

31(5)

130(30)

53(30)

Zn(5—15)

23(20)

29(20)

33(10)

52(20)

57(10)

42(10)

22(5)

65(10)

32(10)

17(30)

75(5)

52(5)

Cu(5—18)

15(20)

15(20)

11(10)

10(10)

21(20)

18(20)

12(10)

15(30)

8(10)

7(10)

13(10)

20(40)

Mn(3—7)

60(5)

34(5)

20(30)

37(10)

23(30)

13(5)

12(10)

91(5)

15(30)

29(5)

40(30)

22(20)

Se(4—13)

0.02(> 50)

0.12(> 50)

0.03(30)

0.04(> 50)

0.12(50)

1 —50

0.05(40)

0.01(50)

0.05(40)

0.01(> 50)

0.06(> 50)

0.6(40)

Cr(1—4)

0.003—0.4

0.001—0.4

0.001—0.4

0.003

0.01—0.3

0.02—8

0.01—0.4

0.003—0.3

0.01—0.4

0.006

0.005

0.006—0.7

Ni(1—3)

0.5(20)

0.5(30)

0.6(30)

2

3(> 50)

7(30)

0.5(30)

1(> 50)

0.4(30)

0.2

3(20)

3(> 50)

Mo(1—2)

0.08

0.3

0.4(20)

0.07

0.3(> 50)

0.02

0.2(10)

0.2(20)

2(> 50)

0.04

0.7

0.4

I(2—3)

0.04(>ts}50)

0.03(> 50)

0.04(30)

0.04(> 50)

0.06(> 50)

0.05(> 50)

0.03(> 50)

0.03(> 50)

0.03(> 50)

0.02(> 50)

0.02(> 50)

0.02(> 50)

Co(1—2)

0.14

0.04

0.05(10)

0.18

0.03(5)

0.7

0.05(50)

0.05(5)

0.05(30)

0.003

0.04

0.06

B(1)

30

20

30

10

30

40

10

20

20

2

10

10

V(1)

0.0005

0.0004

0.0003

0.001

0.001

0.0004

0.0008

0.001

0.001

0.0003

0.0003

0.001

Toxic Elements

Cd (2—3)

o nn£

0.0005—0.008

0.04

0.0005

0.0005

0.005

0.05—0.2

0.01—0.09

0.005

0.01

0.01—1

Pb (2—4)

0.003—0.4

—0.006 0.0003—0.5

0.0005—0.3

0.0007

0.002—0.3

0.001

0.003—0.3

0.006—0.4

0.004—0.3

0.001

0.003

0.002—0.3

Hg (1—2)

0.002

0.0007

0.0005—0.06

0.003

0.0005—0.07

0.0001—0.4

0.0008—0.03

—0.12

0.0003

0.0002

0.0001

As (1—3)

0.006—0.3

0.005—0.8

0.005

0.005

0.003

0.001—0.02

0.01—0.6

0.006—0.4

0.005—0.2

0.001

0.002

0.006—0.02

Al (1 —4)

0.3—12

0.3—5

0.2—20

10

0.8—13

0.2—5

0.4—11

4—40

0.8—14

0.1

0.2

0.2—10

Sb (1)

0.0004

0.0002

0.0005

0.0004

0.0003

0.0003

0.0003

0.0004

0.0004

0.001

0.0004

0.0004

Sn (1)

0.01

0.0003

0.004

0.005

0.001

0.0006

0.007

0.05

0.004

0.005

0.004

0.003

U(1)

< 0.0001

< 0.0001

0.0004

0.0001

<0.0001

<0.0001

0.0005

<0.0001

0.0007

0.0004

0.002

0.001

Ba (1 —4)

10

2

2

10

0.1

70—2000

1

0.03

3

0.01

10

0.1

Tl (1—2)

0.007

0.002

0.003

0.009

0.0002

0.002

0.0003

0.0008

0.0002

0.002

0.0004

0.002—0.01

Concentrations of elements in nuts, expressed as median or range values (mg/kg), with RSD values (%) in parentheses.

Concentrations of elements in nuts, expressed as median or range values (mg/kg), with RSD values (%) in parentheses.

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