Effect of Temperature on Firmness of Raw Fruits and Vegetables

The firmness of a number of fruits and vegetables was measured by deformation, extrusion and puncture tests over the temperature range 0-45°C. Most commodities showed decreasing firmness with increasing temperature but there were several exceptions to this general rule. For the majority of the commodities tested the firmness-temperature relationship was approximately linear. The firmness-temperature coefficient is defined as (firmness at T₂– firmness at T₁)/(firmness at T₁ (T₂? T₁)] × 100 (percent change in firmness per degree temperature change) where T₁= lowest temperature and T₂= highest temperature at which firmness is measured. The firmness-temperature coefficient ranged from -1.65 for apricot to +0.12 for carrot using the puncture principle, from ?0.97 for Baby Gold peach to +7.7 for large Canoga strawberries tested between 30–45°C using the deformation principle, and from -0.04 for Golden Delicious apple stored 7 months to ?1.34 for NK199 sweet corn using the extrusion principle.