Ascorbic acid losses in vegetables associated with cook-chill food preparation

Objective. To assess ascorbic acid (AA) losses in four vegetables (broccoli, peas, cauliflower and cabbage) at each production stage in a cook-chill food service system. Setting. A long-stay psychiatric hospital in Cape Town. Design. Cross-sectional analytical study. On two repeat occasions, three samples of each vegetable were taken at the following stages: (i) delivery (day 1); (ii) after preparation (day 2); (iii) after cooking (day 5); (iv) after blastchilling (day 5); and (v) in the holdroom and after regeneration over a 4-day period (days 6 9). AA content of each sample was assessed in duplicate using the 2,6 dichloroindophenol method of titration. Statistical analyses. Differences between the AA concentration of each vegetable at baseline (delivery) and at subsequent stages in food production were assessed using analysis of variance (ANOVA) methods. Results. The most dramatic AA losses occurred during the cooking stage (mean loss 58%, standard deviation (SD) 19.5%, range 33 81%), with broccoli showing the greatest mean loss of 81% (SD 2.9%). During storage in the holdroom from day 6 to day 9, the average daily loss was 4.3% (SD 4.2%). Further average losses of 6.1% (SD 3.6%) were incurred after regeneration on each day. Mean AA losses on day 6 of production and after regeneration (the earliest time a patient would receive the vegetable) were 87% (SD 5.6%). On day 9 after regeneration (the latest time it could be received by a patient) mean losses were 89% (SD 10.5%). Conclusion. Use of a cook-chill food service system needs to be carefully controlled in order to minimise AA losses. In particular, prolonged cooking times should be avoided and vegetables should be immersed into rapidly boiling rather than cold water. A reduction of the number of days in the chilled storage holdroom would not substantially reduce overall AA losses.