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HPLC Analysis of Garlic Clove Homogenates (continued)

Component
Source of Variation
Sum of Squares
Degrees of Freedom
Mean Squares
F
P-value
             
Allyl Between Groups
50.54
2
25.27
1.4
0.276
  Within Groups
269.66
15
17.98
 
 
  Total
320.2
17
 
 
 
   
 
 
 
 
 
1-Propenyl Between Groups
87.57
2
43.78
59.13
7.68E-08
  Within Groups
11.11
15
0.74
 
 
  Total
98.68
17
 
 
 
   
 
 
 
 
 
Methyl Between Groups
67.21
2
33.6
2.03
0.165
  Within Groups
248.02
15
16.53
 
 
  Total
315.23
17
 
 
 
   
 
 
 
 
 

Table 5. Analysis of variance


Whilst the differences in primary flavour compounds between isozyme groups appear limited to the effect of the initial level of the 1-propenyl cysteine sulphoxide in intact garlic tissue, the relationships between common morphological characteristics and between morphological characteristics and alkyl groups (derived from alkyl cysteine sulphoxides) appear more evident. Tables 6 - 10 show the calculated correlation coefficients ( r ) for all available features of the samples (Table 4) and whilst a number of significant correlations can be seen, relationships of this nature in plants are seldom linear and so the figures should be viewed with caution until further studies have been undertaken. It is worth noting at this point that Saghir has reported on the use of chemical and anatomical data as valuable indicators of taxonomic relationships in alliums and has suggested a correlation between the proportions of alkyl sulphides found in tissue samples and morphological features such as inflorescence and bulb structure and leaf anatomy.

Conclusions

From a practical standpoint there were some elements of the method that require close attention and possibly some modification,

  • samples for HPLC injection must be totally dry as water contamination causes severe ‘spiking’ of the traces,
  • the pre-guard filter must be cleaned in 20% nitric acid in an ultrasonic bath for 30 minutes every day. Such is the level of deposit that failure to clean (or replace) this filter regularly causes increasing back pressure and drifting retention times,
  • because of the solvents employed, only glass syringes should be used for HPLC injection and,
  • whilst every effort was made to ensure consistent final sample volume this method can inherently lead to error at this stage.
The tests have shown that there is a significant difference between the levels of some primary flavour compounds found in garlic tissue homogenates and some principal isozyme groups.
There was an insufficient number of representative samples from secondary isozyme groups to enable statistical analysis beyond the primary groups. A representative from primary isozyme group 2 would aid future investigations.
Whilst every effort was made to confirm the identities of the clones used, future studies should include isozyme testing as an accurate means of grouping.

 

 

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