| The production and preparation of corn is extremely important as a nationally important food crop and feed and
industrial raw material. In order to study the changes of its physical indexes (water content, crack rate, bulk density, ballast
rate, particle size index, maximum force, maximum force point deformation) and activity indexes (respiratory intensity, ger⁃
mination rate, electrical conductivity) under different pre-freezing rates (20, 30, 40 ℃/ min), in this paper, a vacuum
freeze-drying machine was used to freeze-dry corn seeds. The results show that when the pre-freezing rate was increased
from 20 ℃/min to 40 ℃/min, the water content, ballast rate, maximum force value, germination rate, respiratory intensity
reached the maximum value at 40 ℃/min and the minimum value at 20 ℃/min, and all of them increased with the increase
of pre-freezing rate, showing a proportional relationship. The particle size index, crack rate and electrical conductivity all
reach the minimum value at 40 ℃/min and the maximum value at 20 ℃/min, and all decrease with the increase of prefreezing rate, and the relationship is inversely proportional. The particle size index and ballast rate were complementary, the low⁃
er the pre-freezing rate, the lower the particle size index, the higher the ballast rate, the higher the degree of seed integrity.
The decrease of the crack rate indicated that the slower prefreezing rate could improve the stress inhomogeneity of seeds
and help to increase the integrity of seeds. The higher the seed integrity, the easier it is to germinate. In contrast, the bulk
density showed an irregular relationship with increasing pre-freezing rate, with water in the endosperm portion of the seed
crystallising more densely at 40 ℃/min, and starch density increased with pre-freezing rate, resulting in an increase of seed
bulk density to a maximum value of 1.323 g/cm³. The optimal pre-freezing rate of 40 ℃/min was obtained from the vacuum
freeze-drying experiments of corn seeds by different pre-freezing rates, which can reduce the cracking rate and maintain a
good germination rate while maintaining the seed activity, which provides a reference for the storage and subsequent use of
corn. |
