quantification was evaluated by extracting vitamin C from broccoli subjected to a heat shocked treatment (prior to matrix disruption) and raw non-heat shocked broccoli samples. The results are presented in Fig. 2. In this study, HS florets and stalks contained more vitamin C (mainly as L-AA) than their NHS counterparts. In addition, NHS samples contained higher percentage of DHAA compared to the HS samples. In NHS-CE and NHS-HE florets samples, vitamin C entirely occurred as DHAA while some L-AA was found in the NHS-CE and NHS-HE stalks. This study showed that extracting vitamin C from raw NHS broccoli resulted in conversion of L-AA to DHAA. The conversion of L-AA to DHAA was attributed to oxidative enzymes (such as AAO and APx). The heat shock treatment applied in the current study resulted in complete inactivation of oxidative enzymes, since vitamin C in samples heat shocked prior to matrix disruption occurred mainly as L-AA. Furthermore, AAO activity was not detected in the heat shocked samples. Further degradation of DHAA to other compounds such as 2,3-diketogulonic acid could explain why the NHS samples contained less vitamin C compared to the HS samples. The observation of high vitamin C losses in raw NHS samples was in agreement with the report of Yamaguchi et al. (2003) that ascorbic acid oxidase activity could degrade all vitamin C in raw broccoli within 15 min while the vitamin C content of heated broccoli remained constant during incubation for 15 min under the same conditions. In the current study, the retention of some L-AA in the NHS stalks (both CE and HE) but not in NHS florets (both CE and HE) indicated that enzymatic conversion of L-AA to DHAA could be higher in raw florets than in raw stalks. Although some thermal degradation of vitamin C during the heat shock treatment could not be ruled out, this study indicated that enzymatic oxidation play a greater role in vitamin C loss than thermal degradation, since non-heat shocked samples lost more vitamin C than the heat shocked ones.