Retention of Nutrients and Phytochemicals in Fresh and Processed Broccoli

253 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1997.The objective of the study was to determine whether thermal processing, storage and preparation affected concentrations of ascorbic acid, $\beta$-carotene, sulforaphane (SF), sulforaphane nitrile (SFN), cyanohydroxybutene (CHB), iberin (I) and iberin nitrile (IN) in fresh and frozen broccoli. The mean initial concentration of ascorbic acid decreased during fresh storage by 13.0% on a wet weight basis (WWB) and by 7.0% on a dry weight basis (DWB) in 1994, and by 48% on a WWB and by 54.4% on a DWB in 1995. Approximately 30% of the concentration was lost during thermal steam blanching. Ascorbic acid content was maintained during frozen storage. Microwave cooking decreased the concentration by 16.4% on a WWB and by 7.0% on a DWB in 1994, and by 29.1% on a WWB and by 15.3% on a DWB in 1995. There was no significant change in the initial $\beta$-carotene concentration during fresh storage in 1994, but in 1995 $\beta$-carotene decreased by 49%on a WWB and by 56% on A DWB. Stream blanching decreased the concentration by 15%. Frozen storage and microwave cooking did not significantly affect the $\beta$-carotene content. The initial concentrations of CHB, SF, SFN, and IN in 1994 and 1995 in fresh broccoli decreased significantly (p $<$ 0.01) during three weeks of storage at $4\sp\circ$C in 1994 and 1995 (91.5%, 55.3%, 71.9% and 91.4%, 49.3%, 92.0% and 90.8%, respectively). Thermal steam blanching lowered (p $<$ 0.01) the concentration of CHB, SF, SFN, and IN in 1994 and 1995 (96.7%, 65.5%, 97.0%, and 100.0%; and 95.1%, 47.4%, 67.6% and 100.0%, respectively). The phytochemicals were not detected in fresh broccoli that had been steam blanched and frozen. Microwave cooking decreased (p $<$ 0.01) the initial concentration of CHB, SF, SFN, and IN in 1994 and 1995 (76.7%, 37.0%, 55.4%, 86.3% and 73.6%, 32.2%, 76.2%, 77.9%, respectively.) Autolysis reduced the formation of CHB and SF (80.0% and 18.9%, respectively) and increased SFN and IN (38.4% and 31.1%, respectively). The initial activity of myrosinase decreased significantly (p $<$ 0.01) during two weeks of storage from 19.2 to 13.3 $\mu$mole min$\sp{-1}$ glucose mg$\sp{-1}$ protein). Microwave cooking (8 min) significantly decreased (p $<$ 0.01) the initial activity of myrosinase to 7.2 $\mu$mole glucose min$\sp{-1}$ mg$\sp{-1}$ protein, but did not inactivate it entirely.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD