# Spoilage Index Results from our Trials

The spoilage index is an accumulation of the reciprocal of Safe Days. Safe Days depends on the temperature, T , and moisture content, MC. Safe days is defined as:
Number of days until germination capacity is reduced to 95% (Fraser & Muir 1981)
Safe Days = 10^(6.234 -0.2118 MC – 0.0527 T) wheat and cereals
= 10^(6.224 – 0.302 MC – 0.069 T) canola and oilseeds
The objective for safe storage, is to maximize the number of safe days by lowering the temperature T, and the moisture content, MC. Look at how the number of safe days varies with temperature for ‘dry’ wheat:
• 14.5% @ 30⁰C = 38 safe days
• 14.5% @ 20⁰C = 128 safe days
• 14.5% @ 0⁰C = 1458 safe days
• New Definition: Spoilage Index = Ʃ ( 1/ safe days) x 100
Example, if safe days is six, then after 3 days we will have an accumulated deterioration of: (1/6 + 1/6 + 1/6) x 100 = 50%, after 6 days : (6 x 1/6) x 100 = 100% of the way to 95% germination.
We modified the spoilage index in order to accumulate every hour instead of every day:
Spoilage Index (SI) = Ʃ ( 1/ safe days)/24 x 100
What we got from our trial runs from 2007 to 2015:
File      SI     trial time (hours)
071      22.6   214
072      13.7   259
073      11.6   14.8
0809P  3.1      54
0809W 23.8    290
0810B 60.6     291
0810W 24.9    215
0909B   3.6       151
0909W 149.8  268
1010     250     674
1110     71.6     239
1216      85.3    263 bin had no temp cables, so used discharge T
1217      364.6   335 used discharge T, so SI is questionable
1218      45        417 used discharge T
1219      85.3     405 used discharge T
1309B    3494    1274 certainly had spoilage here, cause high MC
1316      216.9    1724
1317      371.4     1910
1318      72.6       1741
1319      38.7       951
1409      1284      2020
1410     350         1296
1416      315.7     1969
1417     86.5        1969
1418     51.2        1600
1419     109.7      1600
1509     426.7      1940  but using sample tube MC 14.5% gives SI of 72.7
1510     104         1862                                                    15.1                      110.2
1516     242         1941                                                     15.8                     145
1517     276         1941                                                     16.2                      196
1518     399         2069                                                     15.8                      267.5
1519     397         1941                                                     15.3                      113.2
As you can see many of our trials had an SI > 100 and this was mainly due to starting with a high or very high MC so the SI grew quickly in the first few days.