4. Conclusion
This study has shown that processing operations and thermal
preservation processes, particularly in an aqueous environment,
resulted in significant glucosinolate loss in kale leaves. Preliminary
processing prior to preservation caused total GLS losses of 30e42%.
Of the three methods of preservation investigated (freezing,
sterilization, drying), the smallest GLS losses were in frozen kale
leaves, while the highest were in sterilized and dried, unblanched
leaves. Compared to the material after preliminary processing
(blanching or cooking), total glucosinolate retention in frozen,
canned, hot air-dried and freeze-dried products was 91%, 57%, 50%,
and 57% respectively.
A modification was introduced into the production process of
freezing kale leaves: cooking replaced the traditional blanching,
with the resulting frozen product requiring only heating and
seasoning by the consumer. In addition, the use of blanching as a
preliminary treatment improved GLS retention in dried leaves due
to the inactivation of myrosinase.