Abstract:
Effects of heat treatments and modified atmospheres on chlorophyll loss and quality of stored broccoli (Brassica oleraceae cv. Top Greens) were studied. The study was divided into 3 parts ; the effects of heat treatment , the effects of modified atmospheres on stored broccoli and the relationship between heat treatment and modified atmosphere. In the first experiment,florets were dipped into water at 45'~ for 7 and 14 minutes, at 50'~ for 2 and 7 minutes and at 25'~ for 7 minutes (control) and then stored at 25'C, 65-85% RH for 3 days. It was found that heat treatment retarded chlorophyll loss and dipping florets into water at 50'~ for 7 minutes was the most effective for retarding yellowing and maintaining chlorophyll content. In addition, chlorophyllase activity remained low in florets that received this treatment. In the second experiment, florets were packed in plastic boxes, wrapped with PE, PP film, LLDPE film at 14 pm and 20 pm thickness and stored at ~OC, 90-95% RH. Other florets stored in an unwrapped plastic box as the control. The results showed that wrapping in plastic film reduced the rate ofrespiration, ethylene production, weight loss and chlorophyll degradation, while unwrapped florets lost weight and wilt rapidly. Sensory evaluation showed that wrapping in LLDPE film at 20 pm thickness was the most effective treatment for maintaining appearance of the florets. In the third experiment, dipping florets into water at 50'~ for 7 minutes and water at 25'C for 7 minutes were packed in plastic boxes, wrapped with 20 pm LLPPE film and unwrapped and then stored at 4'C, 90-95% Rh for 30 days. Hot water treated florets either wrapped or unwrapped showed water soaking, increased yellowing and chlorophyll loss and produced off-odors. Sensory evaluation showed that wrapped unheated florets had the highest scores for quality.