Mechanical Damage

• Impact bruising — internal tissue injury from a drop, collision, or rough handling, common in fruit such as apples.
• Compression damage — injury from stacking, tight packing, or excessive load in transit.
• Abrasion and skinning — surface injury from rubbing against equipment or other units, as in freshly harvested potatoes.
• Cuts — injury from blades, augers, or other moving parts during harvesting or conveying.
• Internal cracking or fissuring — fracture within a kernel, such as rice grain, that is not visible from outside.

These forms occur at every stage from harvest through to packing: a combine’s threshing action can crack kernels, an auger can abrade or cut them, a fruit bin dropped onto a conveyor can bruise its contents, and a poorly padded pack line can skin tubers. The common thread is that the injury originates from a physical force applied during handling, not from a biological or chemical process.

This is why mechanical damage is treated as a quality-measurement attribute in its own right, distinct from decay itself: it describes the physical injury and the elevated risk that follows from it, not a confirmed infection.

A substantial share of mechanical damage does not show immediately. Bruising in many fruit does not discolour until browning reactions and cell breakdown progress over hours or days, so a load can pass inspection sound at intake and reveal visible damage only once it reaches a market or a consumer. This latency is part of why mechanical-damage assessment relies on cut-sample or destructive inspection rather than surface appearance alone where accuracy matters.

Internal fissuring in rice grain is a parallel case at the kernel scale: cracks that form inside the grain, often from uneven drying or rough handling, are invisible on the intact kernel but govern how much of it survives milling as whole grain rather than breaking into fragments. Head rice yield — the proportion of milled rice that remains whole — is directly reduced by fissures that no external inspection would catch before milling.

A unit that passes through harvesting, conveying, temporary storage, sorting, and packing accumulates damage from several independent sources along the way, and the resulting marks look alike regardless of which step produced them. Visual or manual inspection of the finished product can quantify how much damage is present, but it cannot reliably attribute a given bruise, crack, or cut to a specific piece of equipment or handling step.

Identifying where in a handling chain damage is actually occurring requires instrumented methods — impact-recording devices built to travel through the line alongside the product and log the forces experienced at each point — rather than after-the-fact inspection of the product itself. This distinction matters operationally: a high damage figure tells an operator that damage is occurring, but locating the cause requires a different kind of measurement entirely.