In storage
No information was available on the fate of thiram residues in commodities in commercial storage.
In processing
Information was provided on the fate of thiram during the processing of apples to juice and pomace and during the production of wine.
In an apple processing study in the USA thiram was applied 13 times at 11.6 kg ai/ha during the growing period in 1993 to Twenty-ounce apples on a farm in New York State (Armstrong, 1993; Leppert, 1995; Tufts, 1995). Apples (50 kg) were harvested 7 days after the final application and converted to mice and pomace according to a simulated commercial process. There was no washing step; the trial was designed to represent a "worst case" for residues. Thiram residues in apples, juice and pomace were measured by a CS2 evolution GLC head-space method. The thiram residue level in the juice was about 30% of that in the apples, while the level in wet pomace was the same as in the apples. Wet pomace was heated at 77-88°C until the weight had decreased to 20-25% to produce dry pomace. The increase in the thiram level suggested that little of the residue had been lost during the drying process. The residues in the analysed commodities were as shown below.
|
|
Thiram residue |
|
apples |
11.5 mg/kg |
|
juice |
3.3 mg/kg |
|
wet pomace |
11.8 mg/kg |
|
dry pomace |
42 mg/kg |
In grape processing studies in France field-sprayed grapes were processed into juice, wine and raisins (Blaschke, 1995a,b) and only wine (Blaschke, 1995c,d). The thiram results are summarized in Table 33. Samples other than wine had been stored for about 18 months at <18°C before analysis. Wine was kept at 4-8°C.
Approximately 50 kg of grapes were crushed to produce wine, while 3 kg and 6 kg were used for juice and raisin production respectively. Crushing took place in September and the wine was bottled (for analysis) about 6 months later. The champagne in trial 28203B004 (Blaschke, 1995d) was matured in the bottles for an additional year. Wet pomace was dried in an oven for 5 to 8 days and lost 50-60% of its weight.
Grapes were stemmed manually and crushed to produce juice, which was heated to 85-88°C for 5 minutes and then refrigerated for up to 5 days. The supernatant clear juice was bottled and sterilized by heating at 100°C for 20 minutes.
In raisin production, the grape bunches were dried in an oven at 60°C for about 6 days and lost 84-91% of their weight. After drying, the stems were manually removed.
Although no other dithiocarbamate fungicides had been used on the crops (except in trial 28203B004 where mancozeb had been used at a very early stage approximately 17 weeks before harvest) the residue levels of thiram calculated from the CS2 evolution method were substantially higher than thiram measured by HPLC. CS2 residues were not detected in wine produced from untreated grapes and in only four grape samples from untreated plots (trial 28203B002, 0.08 and 007 mg/kg as CS2, and trial 28203B002, 0.10 and 0.08 mg/kg as CS2) which suggests the thiram
567 production of thiram metabolites containing the CS2 group and with sufficient persistence and water-solubility to enter the wine. An unconfirmed possibility is that the liberated CS2 was derived from rubber tubing or gloves.
Table 33. Residues of thiram (expressed as thiram) in grapes, juice, pomace, must, wine and raisins after foliar application of thiram to grapes in supervised trials in France. The application conditions in the trials are listed in Table 30 (supervised trials on grapes).
|
Commodity |
Residues, as thiram, mg/kg |
|||||||
|
Blaschke, 1995b (France, 28203B001) |
Blaschke, 1995a (France, 28203B002) |
Blaschke, 1995c (France, 28203B003) |
Blaschke, 1995d (France, 28203B004) |
|||||
|
HPLC method |
||||||||
|
Grapes (PHI, days) |
1.6 (33) |
4.3 (22) |
1.2 (33) |
1.2(22) |
1.4 (49) |
1.9 (22) |
1.2 (34) |
3.0 (22) |
|
Juice |
<0.1 |
|
<0.1 |
<0.1 |
|
|
|
|
|
Must |
<0.1 |
0.2 |
<0.1 |
<0.1 |
1.3 |
1.7 |
<0.1 |
0.3 |
|
Wet pomace |
<0.1 |
<0.1 |
<0.1 |
<0.1 |
<0.1 |
<0.1 |
<0.1 |
<0.1 |
|
Dry pomace |
<0.1 |
<0.1 |
<0.1 |
<0.1 |
<0.1 |
<0.1 |
<0.1 |
<0.1 |
|
Wine |
<0.1 |
<0.1 |
<0.1 |
<0.1 |
<0.1 |
<0.1 |
<0.1 |
<0.1 |
|
Raisin |
5.7 |
4.9 |
<0.1 |
<0.1 |
|
|
|
|
|
CS2 method |
||||||||
|
Grapes (PHI, days) |
9.3 (32) |
12 (21) |
1.3 (32) |
4.3 (21) |
3.0 (48) |
7.4 (21) |
2.4 (33) |
2.5 (21) |
|
Wine |
0.9 |
0.9 |
0.22 |
0.25 |
0.98 |
0.74 |
0.12 |
0.19 |
Residues in the edible portion of food commodities
The thiram level in apple juice was about 30% of the level in the apples.
Thiram residues in grape juice and wine, by an HPLC method, were undetectable (<0.1 mg/kg).
