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 T 2 – firmness at T 1 )/(firmness at T 1 (T 2 − T 1 )] × 100 (percent change in firmness per degree temperature change) where T 1 = lowest temperature and T 2 = 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.