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Tater Turgor

PULLMAN, Wash. — Where bruising is concerned, all fruits and vegetables aren’t created equal.

Just ask Washington State University agricultural engineer Gary Hyde, who, for a quarter of a century, has been studying how produce is bruised during handling.

Hyde has found that a cold, turgid tuber is easily bruised. The same can be said for D’Anjo pears. But Bartlett pears bruise more easily when they are warmer. Turgid apples bruise more easily, but temperature doesn’t affect them.

Answering complex questions about bruising is helping the fruit and vegetable industries provide higher quality fruits and vegetables to consumers while lowering costs associated with bruising.

Hyde is still learning how to reduce bruising from handling apples, pears and potatoes. There are essentially two approaches; better equipment and operating procedures, or modifying growing practices and conditioning commodities for handling.

Hyde says turgor — internal pressure — affects bruising in apples, pears and potatoes, but differently for each commodity.

The more turgor, the more easily apples, D’Anjo pears and potatoes are bruised. Lower the turgor just a little and there’s less bruising.

Cold temperatures increase bruising in potatoes and pears, but don’t affect apples.

Knowledge about the physiology of bruising can save the potato and tree fruit industry millions of dollars. Hyde says in some instances growers can use this new scientific knowledge to manipulate their crops, making them less susceptible to bruising. Perhaps more commonly, storage operators can change some of their practices to reduce bruising during handling. But they must achieve a delicate balance.

A cold storage operator can reduce bruising by lowering the turgor of fruit. But this results in less fruit to sell. If they lower the water content of fruit by 1%, they have 1% less fruit to sell. So bruising must be decreased enough to more than offset the loss of water content or packers have no incentive to condition the fruit for less bruising.

These small reductions in water content don’t reduce eating quality, Hyde says.

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