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Factors Governing the Greening of Garlic Puree (continued)

Results & Discussion

The color developed with the garlic puree stored at various temperatures is shown in Table 1. The California Early cultivar did not develop green color initially but did so to an increasing degree when stored at or below 12°C. Above 23°C the color was still satisfactory after 32 days storage. The California Late cultivar had an initial light green color which intensified at low temperatures and decreased with warm storage.

Cultivar
Temp (°C) Days stored
California Early  
0
18
32
 
3
Cream
Lt Green
Dark Blue-Green
 
12
Cream
Lt Green
Blue-Green
 
23
Cream
Cream
Cream
 
28
Cream
Cream
Cream
California Late        
 
3
Lt Green
Lt Green
Dark Blue-Green
 
12
Lt Green
Lt Green
Blue-Green
 
23
Lt Green
Cream
Cream
 
28
Lt Green
Cream
Cream
Table 1 - Color of the garlic puree after storage of the bulbs at the temperatures indicated

Similar experiments, using a commercially grown Creole garlic cultivar, showed the same response to storage temperature. These experiments were done over a period of 3 years. Bulbs were switched from greening to non-greening and back again several times by moving them from one storage temperature to another. In one case this was done three times. Each time it took longer to make the change.

The neutral amino acids were investigated since they are involved in both the pinking of onions and the greening of garlic (Lukes, 1958; Shannon, 1961). Greening and non-greening bulbs were analyzed and the outstanding difference between the two was the reduced amount of PECSO in the non-greening type, e.g. 0.1 – 0.3 mg/g of garlic in non-greening and as high as 1.62 mg/g in the greening type. This amino acid is the precursor of the onion lachrymator (Virtanen and Spare, 1951) and its presence in garlic is not well known. The amount of PECSO decreased in warm storage and increased in cold storage. The central role of PECSO in the greening reaction was demonstrated by adding small amounts of it to non-greening, non-heated puree. The mixture turned a depth of green which depended upon the amount of PECSO added (Fig. 1). The equation for the line of best fit, between 0.1 and 1.8 mg PECSO, was absorbance = (0.59 + 0.67) x mg PECSO. The correlation was 0.985 and was significant at the 99% level. The puree that had no PECSO added was pale yellow. The color with 0.1 mg PECSO/g garlic was very light green: 0.4 was green and 1.0 was dark bluish-green.


References

Carson, J.F., Lundin, R.E. and Lukes, T.M. 1966. The configuration of (+)-S-(1-propenyl)-L-cysteine S-oxide from Allium cepa. J. Org. Chem. 31: 1634.
Lukes, T.M. 1958. Pinking of onions during dehydration. Food Technol. 13: 391
Moore, S., Spackman, D.H. and Stein, W.H. 1958. Chromatography of amino acid on sulfonated polystyrene resins. Anal. Chem. 30: 1185
Sano, T. 1950. Green pigment formation in ground garlic. M.S. thesis, Univ. of California, Berkeley.
Shannon, S. 1961. Factors affecting and biochemical reactions involved in the formation of a red pigment in the puree of onion (Allium cepa L.). PhD thesis, Univ. of California, Davis.
Virtanen, A.I. and Spare, C.G. 1961. Isolation of the precursor of the lachrymatory factor in onion (Allium cepa). Suomen Kemistilehti. 34: 72.



 


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