Improve potato quality by minimising mechanical damage

Introduction

This page describes the consequences of mechanical damage and bruising to ware potatoes and how it affects their quality. Ways to minimise damage to tubers and how to assess whether your potatoes are being handled appropriately during harvest and washpacking are described.

When the skin of a potato is broken and bruised, the cells below are damaged and the tubers deteriorate because:

• entry of pathogens becomes easier
• water loss from the tuber increases.

This damage can have severe consequences.

Types of damage

Bruising

There are two types of potato bruises: blackspot and shatter bruise. Blackspot bruise (see Figure 1) involves damage to the tuber’s cell contents and requires the tuber to be peeled to be visible.

Figure 1 Blackspot on a Royal Blue potato

Shatter bruise (Figure 2) involves damage to cell walls and breaks in the skin, visible as cracking on the tuber surface. Shatter bruise can extend to the centre of the tuber and the broken skin is an ideal entry point for disease.

Figure 2 Shatter bruise on a Russet Burbank potato

Skinning

Skinning is most often seen in potatoes harvested before the skins have fully matured. Abrasion between tubers, or between tubers and soil clods or grading equipment, loosens and removes the outer layer of skin. The shelf life of these tubers is reduced because diseases can enter easily and shrivelling is likely due to high water loss.