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.
Table 1 - Color of the garlic
puree after storage of the bulbs at the temperatures
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.
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.