Studies On The Techniques To Inhibit The Browning Of Fresh-cut Burdocks

Browning is the limiting factor in product quality and shelf-life of fresh-cut burdock. Inthis paper, we investigated the influences of heat shock, irradiation, CO2, nitric oxide, ethanolon the browning of fresh-cut burdock, aimed to find an effective and safe method on this issue.The main conclusions are as follows:1. Quality of fresh-cut burdock was affected by different time and temperature heatshock treatment. All the three heat shock conditions obviously delayed the browning offresh-cut burdock during storage time. At1°C, untreated control slices obviously browned onday3, but those treated with heat shock treatments still had good color till day12, moreover,their extent of dehydration was much lower and overall sensory quality was much better thancontrol. Inhibition in rise of the activity of phenylalanine aminolyase (PAL), the content oftotal phenols and the respiration rate by heat shock treatment is the main reason for delayingbrowning.2. High energy electronic beam had a significant effect on quality and browning ofFresh-cut burdock. The irradiation treatments obviously delayed the browning fresh-cutburdock during storage time. In addition, the irradiation treatments not only inhibited theactivities of polyphenol oxidase (PPO), phenylalanine ammonialyase (PAL) and4-coumaratecoenzyme A ligase (4CL), but also reduced the content of total phenols and malondiadehyde(MDA), thus maintained higher storage quality. The effect of1.0Kgy is better than0.5Kgyirradiation treatment.3. Carbon dioxide treatment is the most significant in browning inhibition of fresh-cutburdock. Untreated control slices obviously browned on day2, but those treated with carbondioxide still had good color till day9. Carbon dioxide treatment not only inhibited theactivities of polyphenol oxidase (PPO) and phenylalanine ammonialyase (PAL), whichrestrain the synthesis of phenolic compounds and reduced the content of total phenols, butalso reduced the content of malondiadehyde (MDA) and suppressed the risen of respiratoryrate, which reduced the damage to the cell membrane and alleviated peroxidation ofmembrane lipid.4. The enzymatic browning, respectively increase of polyphenol oxidase (PPO) andphenylalanine aminolyase (PAL) activity, synthesis of phenolic and malondiadehyde (MDA), respiratory rate were significantly suppressed by nitric oxide dip and ethanol fumingtreatment. Meanwhile, they showed marked difference in promoting the synthesis ofchlorogenic acid, gallic acid and protocatechuic acid, and then enhanced antioxidant capacity,reduced surface browning.