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Study on Antioxidative Mechanism of Vegetables by Postharvest Heat Treatment

Author: ZhangZi
Tutor: LiJinCai
School: Tianjin University
Course: Olericulture
Keywords: Postharvest Heat Treatment Antioxidative Mechanism Pepper Pepper shreds Broccoli
CLC: TS255.5
Type: Master's thesis
Year: 2007
Downloads: 162
Quote: 0
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Abstract


Abnormal metabolism of Reactive Oxygen Species (ROS) is the most important reason resulted in vegetable’s senescence. Postharvest heat treatment has been used for retarding senescence and maintaining quality on fruits and vegetables. However, antioxidative mechanism on delaying vegetable’s senescence by postharvest heat treatment hasn’t been systematically reported. Therefore, we investigated the effect of hot water treatment with different treat-time and temperature on physiological indices in peppers, pepper shreds and broccolis, in order to research the antioxidative mechanism of vegetables by postharvest heat treatment. The physiological indices included ROS contents (hydrogen peroxide and superxide), antioxidative substance content (ascorbic acid), antioxidative enzyme activity and some senescence indices, such as color, weight loss rate, chlorophyll, protein and malondialdehyde (MDA).Treatments of peppers and pepper shreds at 55℃for 1 min and 50℃for 4 min and treatment of broccolis at 55℃for 30 s retarded changes of color and weight loss rate, reduced MDA content and increased contents of chlorophyll and protein. They also alleviated production of hydrogen peroxide and superxide, enhanced ascorbic acid content and increased activities of antioxidative enzymes that included superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) during storage period. These data showed that those treatments were effective in retarding the progress of senescence because they could improve antioxidative function of vegetables and reduce accumulation of ROS.In addition, treatment of pepper shreds at 45℃for 10 min had little change in senescence indices, ROS contents and antioxidative function compared with controls. And, treatments of broccolis at 50℃for 2 min and 45℃for 4 min partly increased activities of APX and CAT, content of ascorbic acid and partly reduced hydrogen peroxide content, but their senescence indices had no significance difference with controls. These results showed that those heat treatments had no significant effect on the progress of vegetable’s senescence.Nevertheless, heat treatment of peppers at 45℃for 10 min hastened color change, increased MDA content and reduced contents of chlorophyll and protein. It also increased contents of hydrogen peroxide and superxide and decreased activities of SOD, CAT and APX. These results indicated that the treatment had already accelerated the progress of senescence and brought heat injury to peppers.

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CLC: > Industrial Technology > Light industry,handicrafts > Food Industry > Fruits, vegetables,nuts processing industry > Vegetable processing food
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