Browning Inhibition And Fracturability Maintenance Of Fresh-Cut Burdock And Development Of Soft Canned Burdock

Burdock (arctium lappa L., Liuchuanlixiang), provided by Shunfu Food Co., Ltd (Xuzhou, Jiangsu province, China), was used as raw material. Firstly, nutritional ingredient and sensory quality of burduck at different harvest periods were investigated. Secondly, a compound with browning inhibition and fracturability maintenance effects simultaneously on burdock was developed. To examine its general applicability, the effects of compound on sensory quality of burdock at different harvest periods were investigated. Burdock soft can was developed at last. The main results were summarized as follows:1. Burdock was sampled at 190,210 and 230 days after sowing, marking as harvest period Ⅰ,Ⅱand Ⅲ. Changes of nutritional ingredient content and sensory quality of burdock at different harvest periods were analyzed. The results showed that when we delayed harvest time, moisture content of burdock reduced while the amino acid and reducing sugar content increased. Protein, total sugar, inulin content showed 64%,18%,33% decrease at period Ⅲ respectively when compared toperiod Ⅰ. Lignin content enhanced and 1.5-fold increase was observed in burdock fracturability. L*、a*and b* of burdock color increased with harvest time delaying. Burdock at period Ⅲ, with rich amino acid, uniform white color and high fracturability, was suitable for fresh-cut processing.2. Response surface methodology was used to optimize the concentration of L-Cys, calcium ascorbate and calcium lactate. L*, fracturability and activities of browning and softening associated enzymes were investigated. The results indicated that the best compound contained 0.29 g/100mL L-Cys,1.2 g/100mL calcium ascorbate and 0.2 g/100 mL calcium lactate. After dipped in compound for 15 min and stored at 4℃, polyphenol oxidase (PPO) and peroxidase (POD) activities of burdock decreased, and were lower than the control significantly. The maximum suppressed ratio of PPO and POD activities were 55% and 39%, showing at 4 d and 6 d respectively. Polygalacturonase (PG) and pectin methylesterase (PME) activities were also inhibited by compound. Phenylalnine ammonialyase (PAL) activity was activated, and the activity in compound treated burdock was 1.54-fold of the control at 4 d. After storage 6-8 d, malondialdehyde (MDA) and lignin content were lower than the control, while the total phenol content was significantly higher than the control. Compounds could effectively control browning and maintain fracturability of burdock for 4 days.3. Since high temperature accelerateed browning and softening, burdock at different harvest periods was storaged at 30℃ for 1 d. The effects of compound on sensory quality and activities of browning and softening associated enzymes of burdock were investigated. A significantly lower PPO activity was observed in compound treated burdock and inhibition ratio increased continuously, with a 45% decrease at period Ⅲ. The compound effectively inhibited POD activity and 26% decrease was showed at period Ⅲ. PAL activity of compound treated burdock showed 20%～26% increase at different harvest periods, while PME activity was mostly suppressed with 44.4% decrease at period Ⅲ after compound treated. The compound effectively inhibited PG activity only at period Ⅲ. Phenol content showed most increase at period Ⅱ after compound treated. The compound effectively retarded 18% lignin accumulation at period Ⅱ and Ⅲ. When we delayed harvest time, more and more browning and softening associated enzymes of burdock were suppressed by the compound. Application of the compound could effectively control the browning and softening of fresh-cut burdock at different periods.4. To develop instant burdock soft san, we applied sensory evaluation to flavored soup. As the main indicators, enzyme activity and the total number of colonies were assayed to optimize blanching and sterilization process parameters. The results showed that: Blanching at 90℃ hot water for 60 s were optimal blanching conditions for burdock. In this condition, PPO and POD activities dropped to 8%, and color and fracturability of burdock maintained good.1.0 g salt,6.5 mL white vinegar,0.2 g chili powder and 5 mL sesame oil were added into every 100 g burdock, resulting in a tasty and instant burdock product. Sterilizing at 80℃ for 5 min made the total number of colonies less than 10 CFU/g.