Effects of postharvest curing treatment on flesh color and phenolic metabolism in fresh-cut potato products

Authors: WANG, QINGGUO - Shandong Agricultural University; CAO, YU - Shandong Agricultural University; ZHOU, LILI - Shandong Agricultural University; Jiang, Cai-Zhong; FENG, YANYAN - Shandong Agricultural University; WEI, SHAOCHONG - Shandong Agricultural University

Submitted to: Journal of Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/22/2014
Publication Date: 8/22/2014
Publication URL: http://www.sciencedirect.com/science/article/pii/S0308814614012266
Citation: Wang, Q., Cao, Y., Zhou, L., Jiang, C., Feng, Y., Wei, S. 2014. Effects of postharvest curing treatment on flesh color and phenolic metabolism in fresh-cut potato products. Journal of Food Chemistry. 169:246-254.

Interpretive Summary: Potato is the third largest food crop in world. In 2010, the worldwide production of potatoes reached 324 million tones. As global living standards increase, so too is the demand for fresh-cut potatoes. However, just like many fruits and vegetables, fresh-cut potatoes are prone to browning after cut. This turns out to be the major limitation for their shelf life and prevents fresh-cut potatoes from being a more popular consumer choice. Browning may be the symptom of an ongoing degenerative process, as well as the interaction of phenolic compounds (substrates) and polyphenol oxidases (PPO) that are activated after the cut surface contacted with oxygen. Browning may also be the result of an active inductive process, requiring de novo synthesis of PAL and the consequent accumulation of phenolic compounds. Although high phenolic compound activities are associated with high potential of browning , they also have positive benefits such as enhancing the antioxidant capacity of plant tissue. Many polyphenols, especially phenolic acids, are directly involved in the response of plants to different types of stress. These chemicals contribute to healing by lignifications of damaged areas, and possess antimicrobial properties by increasing concentrations after pathogen infection. The mechanism of browning in potato tuber fresh-cut is still very obscure. Various approaches have been applied to extend the shelf life of fresh-cut potatoes. These methods include use of chemical compounds and plant extracts, as well as modified atmosphere packaging that exclude oxygen from the environment. However, these anti-browning means are generally constrained due to their high cost, low efficiency or potential health hazards. Therefore, it is desirable to develop a simple, safe and cost-effective method to extend the shelf life of fresh-cut potatoes for commercial use. Curing is a normal practice after potato harvested to promote dormancy and extend postharvest storage life, by preventing decay caused by microorganism during storage. Curing at 15oC for 14 days in dry conditions reduced the incidence of skin spot from 70% prick wounds infected down to 4%. Kim and Lee reported that reconditioning of potato improved chip color by reduce no enzymatic browning during high temperature frying. However, the biochemical changes related to phenolic metabolism and enzymatic browning in cured potato tuber flesh and after cutting remains unclear. To date, no information is available on the effect of postharvest curing treatment on fresh-cut potatoes in terms of color, detailed physiological and biochemical changes. Accordingly, the objective of the present study is to investigate the effect of postharvest curing on the color of fresh-cut potatoes, and to understand possible mechanism by measuring respiration, membrane leakage, PAL, PPO activities and phenolic content during curing and the subsequent fresh-cut shelf life period. Result indicated that postharvest curing not only changed phenolic metabolism during curing, but also improved fresh-cut color for 12 days after fresh cut. Significantly lower PAL and higher phenolic content and PPO activities during curing treatment and fresh-cut potatoes were detected compared to the control, which lead to the lower browning in the slices from curing treated potatoes. HPLC analysis revealed that amounts of total phenolics, chlorogenic acid, gallic acid and protocatechuic acid were induced by curing and highly accumulated in the curing treated potatoes. These results demonstrated that phenolic metabolism played an important role in the control of browning of fresh cut potato after curing.

Technical Abstract: The flesh color and phenolic metabolism in potato tuber during curing and after cut were investigated. Result indicated that postharvest curing not only changed phenolic metabolism during curing, but also improved fresh-cut color for 12 days after fresh cut. Significantly lower PAL and higher phenolic content and PPO activities during curing treatment and fresh-cut potatoes were detected compared to the control, which lead to the lower browning in the slices from curing treated potatoes. HPLC analysis revealed that amounts of total phenolics, chlorogenic acid, gallic acid and protocatechuic acid were induced by curing and highly accumulated in the curing treated potatoes. These results demonstrated that phenolic metabolism played an important role in the control of browning of fresh cut potato after curing.