Abstract
We studied the effects of storage temperature on the activities of phenylalanine ammonia- lyase (PAL), peroxidase (POD) and polyphenol oxidase (PPO) in minimally processed kale (Brassica oleracea var. acephala) that was stored for 15 and 9 days at 5 ± 1oC and 10 ± 1oC, respectively. The main visual evidence for quality loss in whole leaves was yellowing and loss of turgescence. Minimally processed leaves presented significant browning, indicating increased POD and PPO activities. The PAL activity in minimally processed leaves stored at 5oC was fourfold higher than that of whole leaves after two days of storage. We showed that minimal processing influenced PAL, POD and PPO activities. The activity of all enzymes studied increased during storage, indicating that changes in phenolic metabolism play an important role in the decline of kale quality. PAL activity increased rapidly at the beginning of storage and exhibited a reduced rate of increase over time, while the PPO and POD activities increased continuously over time. The storage at 5 ° C was a great ally in delaying changes in phenolic metabolism; however, the absolute PAL activity was higher at 5 than at 10oC.
Highlights
There is a high level of interest in the production of minimally processed fruits and vegetables for consumption at home, in fast-food restaurants and in hotels; this demand has been attributed to the desire for reduced preparation time (BEAULIEU et al, 1997)
The Brazilian population consumes a significant amount of kale (Brassica oleracea cv. acephala), and minimally processed kale is popular in Brazil
Our results showed that increases in phenylalanine ammonialyase (PAL) activity at the start of storage may have contributed to phenol compound accumulation; these phenols may have been oxidized by polyphenol oxidase (PPO) and POD, inducing darkening in the minimally processed leaves beginning at six days at 10°C and at 11 days at 5°C
Summary
There is a high level of interest in the production of minimally processed fruits and vegetables for consumption at home, in fast-food restaurants and in hotels; this demand has been attributed to the desire for reduced preparation time (BEAULIEU et al, 1997). Agronomy processed products are used in industrial cooking and fast-food restaurants (WILEY, 1994). Brazil has many commodities that are useful when they are minimally processed, such as cabbage, taioba and serralha (CARNELOSSI et al, 2005). The Brazilian population consumes a significant amount of kale Acephala), and minimally processed kale is popular in Brazil. In the state of Brasilia, for example, the production of minimally
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