Storage of potatoes : effects of ethylene and 1-MCP on potato tuber quality and biochemistry

Abstract

Potatoes are widely consumed in UK and many other countries. There is a continuous demand for potatoes all year around both from consumers and retailers such that several postharvest technologies are being used to meet this demand. Sprouting is the main phenomenon affecting both the quality and marketability of potatoes during long term storage. Several sprout suppressants are widely used (e.g. maleic hydrazide and chloropropham, but there are concerns over their toxicity such that alternatives have been sought. Continuous exposure of potato tubers to ethylene (usually 10 µL L- 1 ) during storage was approved by the Chemicals Regulation Directorate since 2003. Even though potatoes have been regarded as non climacteric, this study aimed to examine the effect of different ethylene regimes in combination with or without 1-methylcyclopropene on physiological, biochemical and mechanical characteristics of a selection of important UK cultivars. In 2008-2009, ten potato cultivars were examined for their response to four different ethylene regimes during storage. Storage time and ethylene treatments had a cultivar specific effect on all the measured parameters (sprouting, sugars, texture). Ethylene applied after first indication of sprouting was as effective at sprout inhibition as when applied continuously for certain potato cultivars; therefore this could be considered as a more environmentally and economical alternative for sprouting inhibition. In addition, sugar accumulation was retarded when tubers were subjected to ethylene at the first indication of sprouting compared to those treated with continuous ethylene. In 2009-2010, four potato cultivars were studied and the effect of 1-MCP either before or after ethylene treatment on sprouting, respiration rate, endogenous ethylene production and texture was investigated. 1-MCP is believed to interact with ethylene receptors and therefore prevent or retard ethylene dependent responses. 1-MCP seemed to effectively block ethylene binding sites when applied before storage of tubers in ethylene resulting in less tuber sugar accumulation. In 2010- 2011, the effect and timings of 1-MCP and ethylene treatments on sprouting, tuber respiration, endogenous ethylene production and sugars on two potato cultivars was studied. 1-MCP effectively suppressed the action of ethylene in terms of the increase in the respiration rate or ethylene production and sugar accumulation. Selected potato samples were also analysed quantitavely for an array of phytohormone using a newly developed UPLC QToF MS method. This method had the advantage of quantifying simultaneously a significant number of plant growth regulators that are present in potato (ABA and its metabolites, cytokinins and gibberellins).