Spinach powder

Schuller, A., Morisset, M., Maadi, F., Kolopp Sarda, M. N., Fremont, S., Parisot, L., Karmy, G., and Moneret-Vautrin, D. A. (2005). Occupational asthma due to allergy to spinach powder in a pasta factory. Allergy 60, 408 09. 

Table 7.1. Detection limits for lead with increasing concentrations of spinach powder in the slurry (from [25])...

Concentration of spinach powder in slurry, % m/V Mean absorbance Relative standard deviation, % Calculated detection limit, xg/g... 

Different biological samples were analyzed via the ICP-IDMS approach depicted in Figure 8.8 and the results obtained were compared with those of an interlaboratory study in which 14 laboratories using various non-IDMS techniques participated. In this study, a silicon content of 5.3 + 1.0 pg (mean + standard deviation based on five independent analyses) was found for a homogeneous pork liver sample via ICP-IDMS, which agreed well with the result of the inter-laboratory study of 5.1 + 2.8 pg g (mean of the means of individual laboratories + corresponding standard deviation). In contrast to this agreement, the results for a spinach powder were 333 + 11 pg g for ICP-IDMS and 176 + 189 pg g for the inter-laboratory study. The reason for this extreme difference between the ICP-IDMS result and the mean value, and also for the unacceptable standard deviation in the inter-laboratory study, is the presence of considerable amounts of silicate in spinach. Many laboratories had not adequately dealt with this silicate portion due to analytical difficulties with and errors in the sample preparation. 

It may be more expeditious at the community, state, or national levels to enrich and fortify foods of low nutrient quality with amino acids, minerals, and vitamins, than to try to supply foods which naturally contain the optimal quantities of nutrients. This is particularly applicable to situations where foods, which are rich in the desired nutrients, are rejected by the population to be fed. Lor example, there is a high rejection rate for broccoli, carrots, and other vegetable sources of vitamin A in the US. School Lunch Program. Therefore, food technologists have proposed the development of a snack food, like a potato chip, which would contain spinach powder and be fortified with minerals and vitamins. 

Determination of Peroxidase activity. Suspension of fi eze-dried spinach powder was allowed to stand at room temperature for 20 min and filtered through cheese cloth. The filtrate (peroxidase extract) was fractionated with 40-85 % ammonium sulfate and the preciptate was dissolved in 0.1 M phosphate buffer (pH 7.0). The isolated enzyme solution was fieeze-dried after dialysis against water. The enz5mfie activity was measured as described previously 12). 

SPINACH POWDER IS A SUITABLE MEDIUM FOR INTERLABORATORY COMPARISONS (ILC) OF ENVIRONMENTALLY RELEVANT NUCLIDES... 

Potential participants were invited by e-mail. Based on 77 affirmations (59 laboratories from Germany, five from Switzerland, four from Austria and the United Kingdom and one each from France, Italy, the Netherlands, Ireland and Luxembourg) the necessary amount of labelled spinach powder was produced. Commercial spinach powder (Spinacia oleracea) was used, which was prepared virtually free of weeds and yellow leaves from field-fresh spinach. According to the manufacturer the stalks were removed mechanically and leaves were washed three times after harvesting. The spinach was air-dried at 60° C and then finely ground (particle size average of 200 microns). The water content was 8 2%. 

In our laboratory eight kilograms of spinach powder were spread out in four stainless steel trays (45 cm x 60 cm) and the nuclide containing solutions were evenly distributed dropwise with a multi-channel-pipette. Sr-90, Cs-134 and Cs-137 were added as a mixture of dilute hydrochloric acid solution in 80% acetonitrile. To maintain the iodine in the non-... 

Spinach Powder is a Suitable Medium for ILC of Environmentally Relevant Nuclides... 

Table 1 Characteristics of three nuclides added to the spinach powder to check the...

Each of the required three individual values for each nuclide was corrected with the factor that resulted from the weights of labelled and imlabelled spinach powder. The arithmetic mean and standard deviation for each laboratory was calculated. The data were visually inspected for outlier elimination. In addition, outliers were identified using Mandel s wilhin- and between-laboratory consistency test statistic k and A-values, respectively) and Grubbs I and II tests according to DIN ISO 5125-2 The outher-free data sets were used to calculate repeatability and reproducibility. Individual z-scores were used as a measure of performance characteristic of the participating laboratories. ... 

To attain comparable values for the dry matter (DM) content of the samples, the participants were instructed to use a fast method for drying the spinach powder (135°C, 6 h). Preliminary studies had shown that drying at 100° C did not give a constant weight in a reasonable time. The average of the results of all participants was only about 2% above the reference value, although the range of the outlier-free values was broad (81.3 to 94.7%). 

The Cs-137 measurements included 350 individual measurements in 119 data sets from 76 participants, after the elimination of outliers 343 individual values in 118 data sets of 75 laboratories remained, i.e. there were only 2% outliers. The general mean was 7.6% less than the reference value. The repeatability and reproducibility coefficients of variation were 4.7% and 9.5%, respectively. The slightly increased value of the repeatability coefficient of variation compared to the other y-nuclides probably results from the lower specific activity of this nuclide in the spinach powder. This nuclide is routinely recorded and evaluated in all laboratories that measure environmental media. The cesium-137 analysis is facilitated by the presence of an interference-free gamma line at 662 keV and the high emission probability of 85%. 

Spinach powder seems to be a suitable medium for interlaboratory tests because it can be readily spiked homogenously, although the properties of the material have shown some problems. 

Overall, spinach powder seems to be well suited as a medium for interlaboratory comparisons. The quality of gamma spectrometric measmement of the y-nuclides K-40,1-131, Cs-134 and Cs-137, relevant for environmental monitoring, is good. However, we still foimd a broad range of results for Sr-90 analysis. 

---