Pectin role in woolliness development in peaches and nectarines: A review

• The biggest role of pectin metabolism in CI of peach and nectarines is in the woolliness.
• Disorders of pectin metabolism are caused by imbalance of pectolytic enzyme activities.
• Post-harvest heat treatments must be precise set to reduce the woolliness.
• Post-harvest treatment with 1-MCP has no permanent effect on peaches or nectarines.
• Cellulase and lipoxygenase role in pectin metabolism and CI development is unclear.

One of the main problems during peach and nectarine cold storage is the associated chilling injuries, which can include woolliness, mealiness, leatheriness, flesh browning, internal reddening, and flesh or pit cavities. Woolliness is one form of chilling injury. It manifests as a lack of juiciness and a dry ‘woolly’ texture of the fruit flesh. Its occurrence is correlated with pectin metabolism and is controlled directly or indirectly by the pectolytic enzymes (i.e., polygalacturonase, pectin esterase, cellulase, lipoxygenase). Chilling injury to these fruit also results in changes in the fruit physiology and cell anatomy. A reduction in woolliness is possible with post-harvest treatments, such as with heat (which must be carried out carefully), calcium, ethylene (blocking or producing), nitrogen monoxide, or a controlled atmosphere. This paper focuses only on woolliness and factors affecting its occurrence. In this paper the role of pectin metabolism, temperature and postharvest treatments on occurrence of woolliness is discussed. The role of some enzymes, such as pectin esterase, and postharvest treatment with 1-MCP still remain unclear and further research is needed to elucidate physiological mechanisms that lead to development of woolliness.