IV]
T. S.
KRISHNAN
267
view is further supported by the fact that the sealing is quicker and more complete in fresh eggs,
which generally contain more CO 2 , than in old ones, which usually contain much less of this gas.
With water-glass the sealing is probably due to the deposition in the pores of insoluble gelatinous
SiO 2 formed by the hydrolytic dissociation of the Na 2 SiO 3 and its consolidation with time. This, as
has been observed, is evidently a slow process.
To determine the effect of shell-sealing on the keeping quality of eggs, a comparative study of
the interior quality of similar lots of treated and untreated infertile eggs stored at 100°F. (summer
conditions) was made. The treatment given was immersion for 12 hours in lime-water. Water-
glass was abandoned as being too slow for practical commercial application. The results of the
study are presented in Fig. 1. It was found in each test that the interior quality, as judged by
albumen index (Average diameter Height of thick white), percentage thick white and yolk index
(Height/Diameter of yolk), was somewhat better in the treated eggs than in the untreated ones. The
air-cell depth, however, showed a marked difference in the two lots. The treated ones had a signi
ficantly smaller air-cell depth than the controls at all stages of the storage period. In the above
experiment, which simulates summer conditions, the maximum allowable air-cell depth of 9.5 mm.
(3/8 in.) according to the Agricultural Grading and Marking Act, was attained in the untreated eggs in
four days, while in the treated ones this level was reached only after 11 days. In the commercial
grading of eggs by candling, considerable weight is attached to air-cell size. Those with air-cells of
more than ⅜ in. depth are rejected, below this limit eggs with bigger air-cells are relegated to lower
grades. In the hot summer months, when temperatures are high and humidity low, evaporation
from eggs is rapid and consequently air-cells increase in size quickly. Since the bulk of the eggs
are produced in villages and consumed in towns and cities, they have to be transported from the
rural areas to the urban and pass through various trade channels in the process. Consequently
they take a few days to reach the consumer. During the hot weather, unless eggs reach the consumer
within about 3-4 days of their being laid, for reasons already stated they may be rejected as under
grade, resulting in serious losses to the trade. If, however, soon after collection their shells are
sealed by immersion in lime-water for even 12 hours, their quality would be maintained better despite
these adverse conditions, for about a week, thereby giving more time for marketing them and thus
avoiding loss and wastage, besides providing the consumers with a better quality product. This
method would also keep down shrinkage and conserve the quality of eggs transported over long
distances during summer months.
In the United States of America and other western countries shell-sealing of eggs is generally
carried out by dipping in oil. The cost of the oil, which is patented, the difficulty of obtaining it
and the greasiness of shell resulting from this treatment are all handicaps in its adoption to Indian
conditions. With lime-water, on the other hand, the cost is negligible, the material is readily avail
able everywhere, its method of preparation and use are simple and require little skill, the period of
treatment is reasonably short and its use results in substantial benefits to the egg trade. It may
therefore be recommended for general adoption by village producers and traders who handle only
small numbers of eggs at a time. They are advised to put the eggs in lime-water for at least 12-18
hours, as quickly as possible after they are laid, and store them in the coolest place available. The
eggs should be removed from the liquid only at the time of sale. Better results are obtained if the
eggs are infertile or defertilized [Krishnan and Macdonald, in the press] before the lime treatment.
The process is intended only for use with table eggs.
SUMMARY
The comparative efficiency of lime-water and water-glass for egg preservation under Indian
conditions has been studied. Treatment for only six hours with lime water appeared to be much
more effective than five days with water-glass. Immersion for 18 hours in lime water seems to be
sufficient for shell sealing.
REFERENCE
Macdonald and Krishnan (1943). Indian J. vet, Sci., 13, 306